The effect of an injectable toltrazuril - gleptoferron (Forceris®) on Cystoisospora suis oocyst excretion and growth of neonatal piglets pre- and post-weaning

In this study the efficacy of an intramuscular formulation of toltrazuril combined with gleptoferron for the control of porcine cystoisosporosis caused by Cystoisospora suis was investigated. The study was carried out on three Belgian farms with a confirmed history of C. suis infections. As none of the farms implemented a standardized toltrazuril treatment regimen for their piglets, the presence of resistant C. suis strains seems improbable. In total 90 litters, representing 1249 piglets, were included in the study and randomly allocated to either the treatment or control group. Piglets in the treatment group received a single intramuscular injection, containing 45 mg toltrazuril and 200 mg gleptoferron, between 1 and 3 days of age. Piglets in the control group received a single injection with only 200 mg gleptoferron. The effect of treatment on oocyst excretion, expressed in oocysts per gram of feces (OPG), average daily weight gain (ADG) and mortality was determined both pre- and post-weaning. A significant decrease in OPG as well as a decrease in the number of litters (pre-weaning) and pens (post-weaning) that tested positive for cystoisosporosis, was observed in the treated animals compared to the controls. Furthermore, treatment resulted in an increased ADG during the period from day 1 to day 21 (p-value: 0.03881). There was no significant difference in mortality observed between the treatment group to the control group (p-value: 0.2167). To our knowledge, this is the first report on the effect of toltrazuril on oocyst excretion after weaning. This finding highlights the potential long-term benefits of the treatment beyond the initial administration.

Isospora juruviarae n. sp. (Apicomplexa: Eimeriidae) from chivi vireos Vireo chivi (Vieillot, 1817) (Passeriformes: Vireonidae) in South America

Chivi vireos Vireo chivi (Vieillot, 1817) are passerine birds widely distributed throughout Brazil, but mainly observed in the Atlantic Forest of the South and Southeast regions of the country. In this context, the current study identifies a new species of Isospora Schneider, 1881 from V. chivi captured in the Marambaia Island, on the coast of the State of Rio de Janeiro, Southeastern Brazil. The oocysts of Isospora juruviarae Andrade & Berto n. sp. are subspheroidal to ovoidal, measuring on average 26 by 24 μm. Micropyle is absent or inconspicuous. Oocyst residuum absent, but polar granules are present. Sporocysts are ellipsoidal with pointed posterior end, measuring on average 17 by × 11 μm. Stieda and Sub-Stieda bodies are present. Sporocyst residuum is present among the vermiform sporozoites, which have refractile bodies and nucleus. This morphology was different from the other Isospora spp. recorded in the same family, superfamily and parvorder as the host. Molecular identification was targeted by the amplification and sequencing of two different loci of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and one locus of the 18S small subunit ribosomal RNA (18S) gene. Phylogenetic analyses were not very efficient in forming monophyletic groups associated with host taxon, zoogeographical region or taxonomic character; however, they confirmed the identification as a new species through comparison with sequences from Isospora spp. of wild passerines. Finally, based on the morphological and molecular analyses of the oocysts recovered from the chivi vireo V. chivi in the current work, I. juruviarae is considered new to science, being the second species recorded in the host family Vireonidae and the first to have a supplementation by molecular identification.

Molecular and statistical approaches to the delimitation of Eimeriidae species: a case of extreme polymorphism in eimerian oocysts from the plumbeous pigeon Patagioenas plumbea (Vieillot, 1818) (Columbiformes) in South America

The current work aimed to analyze, morphologically, statistically, and molecularly, oocysts shed from plumbeous pigeons, Patagioenas plumbea (Vieillot, 1818), from a locality at 2197 m of altitude near the Agulhas Negras peak, the highest point of the State of Rio de Janeiro, southeastern Brazil. The oocysts were extremely polymorphic, being subspheroidal, ovoidal, or ellipsoidal, in addition to having the random presence/absence of characteristic features associated with the oocyst wall, such as micropyle, micropyle cap, lateral micropyle, and outer veil/rough wall. Linear regression confirmed the extreme polymorphism of oocysts, showing that if all combinations of taxonomic characters in oocysts (morphotypes) were overestimated, 19 different species could be identified/described. In contrast, the means comparison analysis between oocysts with the presence/absence of characteristic features and the histograms showed equivalences and regularity in the distribution in the classes of measures, which indicate the presence of a single species in the measured oocysts. Molecular analyses were performed from the isolation of individual oocysts of different morphotypes, which had their genetic material extracted, amplified, and sequenced in 4 non-overlapping loci in the cox1 and cox3 genes and fragments of the small and large subunit rDNA of mitochondrial DNA. The sequences were 100% identical between the morphotypes, with the exception of a very small divergence observed at the locus that partially covers the cox3 gene. The phylogenetic analysis was inconclusive for the locus within the cox1 gene traditionally used for eimeriid coccidians; however, the other loci should have a promising future for phylogenetic studies when more sequences for the same genic regions are deposited in GenBank. Finally, the multifactorial analysis of the current work supported that the polymorphic oocysts shed from P. plumbea are a single species, which was named Eimeria patagioenasae, making this the twenty-second eimerian description from Columbiformes.

Anti-Cryptosporidium oocysts polyclonal antibodies for cryptosporidiosis diagnosis and protection

Cryptosporidiosis is an intestinal infection that is triggered by the protozoan parasite Cryptosporidium spp. Cryptosporidium oocysts can spread from one host to another either through direct contact with infected hosts' faeces or through indirect means (consumption of contaminated water or food). Significant numbers of oocysts are produced as a result of the rapid growth of the parasite within the infected hosts. For proper care of cryptosporidiosis, a laboratory diagnosis is necessary. Therefore, this study aimed to produce anti-Cryptosporidium parvum (C. parvum) oocyst immunoglobulin (Ig)G polyclonal antibodies (pAbs). The produced pAbs were used in the detection of C. parvum oocysts antigens in stool and serum samples of infected calves. Moreover, pAbs were tested in protection of balb-c male mice from cryptosporidiosis infection. C. parvum oocysts were used in the preparation of antigens to be used in the immunization of New Zealand white rabbits. pAb was purified by ammonium sulphate precipitation method, caprylic acid purification method and diethylaminoethyl (DEAE) anion exchange chromatographic method. Sandwich enzyme-linked immunosorbent assay (ELISA) (using prepared pAb) scored higher sensitivity (85% and 95% for serum and stool samples) than that (80%) of microscopic examination of stool samples. Moreover, pAb significantly reduced the oocysts shedding, decreased inflammatory cytokines and enhanced the loss in the body weight of protected animals. The prepared pAb succeeded in the diagnosis of cryptosporidiosis in calves with high sensitivity either in the serum or stool samples. Our results indicated the usefulness of using the prepared pAb in protection against cryptosporidiosis.

Sub-lethal exposure to chlorfenapyr reduces the probability of developing Plasmodium falciparum parasites in surviving Anopheles mosquitoes

BACKGROUND

Pyrethroid resistance in the key malaria vectors threatens the success of pyrethroid-treated nets. To overcome pyrethroid resistance, Interceptor® G2 (IG2), a 'first-in-class' dual insecticidal net that combines alpha-cypermethrin with chlorfenapyr, was developed. Chlorfenapyr is a pro-insecticide, requiring bio-activation by oxidative metabolism within the insect's mitochondria, constituting a mode of action preventing cross-resistance to pyrethroids. Recent epidemiological trials conducted in Benin and Tanzania confirm IG2's public health value in areas with pyrethroid-resistant Anopheles mosquitoes. As chlorfenapyr might also interfere with the metabolic mechanism of the Plasmodium parasite, we hypothesised that chlorfenapyr may provide additional transmission-reducing effects even if a mosquito survives a sub-lethal dose.

METHODS

We tested the effect of chlorfenapyr netting to reduce Plasmodium falciparum transmission using a modified WHO tunnel test with a dose yielding sub-lethal effects. Pyrethroid-resistant Anopheles gambiae s.s. with L1014F and L1014S knockdown resistance alleles and expression levels of pyrethroid metabolisers CYP6P3, CYP6M2, CYP4G16 and CYP6P1 confirmed by quantitative reverse transcription polymerase chain reaction (RT-qPCR) prior to conducting experiments were exposed to untreated netting and netting treated with 200 mg/m3 chlorfenapyr for 8 h overnight and then fed on gametocytemic blood meals from naturally infected individuals. Prevalence and intensity of oocysts and sporozoites were determined on day 8 and day 16 after feeding.

RESULTS

Both prevalence and intensity of P. falciparum infection in the surviving mosquitoes were substantially reduced in the chlorfenapyr-exposed mosquitoes compared to untreated nets. The odds ratios in the prevalence of oocysts and sporozoites were 0.33 (95% confidence interval; 95% CI 0.23-0.46) and 0.43 (95% CI 0.25-0.73), respectively, while only the incidence rate ratio for oocysts was 0.30 (95% CI 0.22-0.41).

CONCLUSION

We demonstrated that sub-lethal exposure of pyrethroid-resistant mosquitoes to chlorfenapyr substantially reduces the proportion of infected mosquitoes and the intensity of the P. falciparum infection. This will likely also contribute to the reduction of malaria in communities beyond the direct killing of mosquitoes.

Investigation into the potential of using UV-treated sporulated oocysts of Eimeria tenella as a local solution to immunization of chickens against caecal coccidiosis

In this study, we aim to evaluate the immune response of chickens to UV-treated sporulated oocysts as a means of protection against caecal coccidiosis caused by field strains of Eimeria tenella. Two groups of chicks were immunized using prepared UV-treated oocysts of E. tenella and challenged at day 20 post hatching. The first group was immunized only once at day 1 post hatching, the second group was immunized twice (day 1 and day 8 post hatching). Two non-immunized control groups were used: the first group was challenged with E. tenella, while the second group remained uninfected. The effectiveness of immunization on production and animal health was evaluated by the following criteria: body weight, feed conversion ratio, blood in faeces, mortality, lesion scores and oocyst output. The two immunized groups showed a significantly better performance in body weight, weight gain and lesion scores than the non-immunized group. However, all three groups performed significantly worse than the unchallenged group. The mortality of the non-immunized infected group was high (70%) while mortality in both immunized and unchallenged groups of chickens was significantly lower (range 2.2 to 4.4%) than the infected group (p < 0.05). The production of oocysts in faeces, post-infection, was significantly higher in the non-immunized group compared to the immunized group (p < 0.05) and both were significantly higher than the uninfected group (p < 0.05). In conclusion, immunization by prepared UV-irradiated oocysts is effective in stimulating at least a partial protective immunity in immunized chickens against caecal coccidiosis.

Experimental infection of sheep at mid-pregnancy with archetypal type II and type III Toxoplasma gondii isolates exhibited different phenotypic traits

Toxoplasma gondii is a major cause of reproductive failure in small ruminants. Genotypic diversity of T. gondii strains has been associated with variations in phenotypic traits in in vitro and murine models. However, whether such diversity could influence the outcome of infection in small ruminants remains mostly unexplored. Here, we investigate the outcome of oral challenge in sheep at mid-pregnancy with 10 sporulated oocysts from three different T. gondii isolates belonging to archetypal II and III and selected according to their genetic and phenotypic variations shown in previous studies. Seventy-three pregnant sheep were divided in four groups: G1 infected with TgShSp1 isolate (type II, ToxoDB#3), G2 with TgShSp16 isolate (type II, ToxoDB#3), G3 with TgShSp24 isolate (type III, ToxoDB#2) and G4 of uninfected control sheep. Two different approaches were carried out within this study: (i) the outcome for the pregnancy after infection (n = 33) and (ii) the lesions and parasite tropism and burden at 14 and 28 days post infection (dpi) (n = 40). The onset of hyperthermia and seroconversion occurred one and two days later, respectively in G1 when compared to G2 and G3. However, sheep that suffered from reproductive failure, either by abortion, foetal dead at the time of euthanasia or stillbirth were similar among infected groups (50%, 40% and 47%, respectively). Histological lesions in placentomes and foetal tissues from euthanized animals from the second approach were only detected at 28 dpi and mainly in G1. At 14 dpi, T. gondii-DNA was only detected in G1 in the 11% of the placentomes. However, at 28 dpi the frequency of detection in placentomes was higher in G1 (96%) than in G2 and G3 (7% and 47%, respectively) besides in foetuses was lower in G2 (20%) than in G1 and G3 (100% and 87%, respectively). Regarding late abortions, stillbirths, and lambs of G1, G2 and G3, the frequency of microscopic lesions was similar between groups (79%, 78% and 67%, respectively) whereas T. gondii-DNA was evidenced in 100%, 55% and 100%, respectively. These recently obtained T. gondii isolates led to similar reproductive losses but intra- and inter-genotype variations in the rise of hyperthermia, dynamics of antibodies, frequency of lesions and parasite detection and distribution. Thus, the different phenotypic traits of the isolates could influence the outcome of the infection and mechanisms responsible for it, and further investigations are warranted.

APOLOCYSTIS BOSANQUETI N. SP. (APICOMPLEXA: EUGREGARINORIDA) FROM THE INVASIVE EARTHWORM AMYNTHAS AGRESTIS (ANNELIDA: MEGASCOLECIDAE), WITH SIGNIFICANCE FOR THE MONOPHYLY OF THE FAMILY MONOCYSTIDAE

Apolocystis bosanqueti n. sp., a parasite of an important invasive earthworm in North America, Amynthas agrestis, is described from a site in northern Vermont. The earthworm host follows an annual life cycle in Vermont, so the entire life cycle of the parasite can be observed in 7 mo. In spring, the parasites were first seen in juvenile worms as paired gamonts (suggesting precocious association). These paired gamonts mature into gametocytes that form an opaque structure, with a thick gelatinous envelope (epicyst), that becomes full of zygotes. The resulting gametocyst becomes packed with ∼105 fusiform oocysts. The mature orbicular gametocysts are large (∼1 mm in diameter) and visible to the naked eye through the body wall of the host's anterior segments. The new species most resembles Apolocystis herculea described from many lumbricid earthworm species in Europe but differs from that parasite because Ap. herculea infects the intestinal wall in the posterior of the host rather than the anterior segments. A survey of 9 other earthworm species sympatric with Am. agrestis revealed that only Amynthas tokioensis, also an invasive species, was infected with Ap. bosanqueti, albeit much less commonly. Diagnosis for the family Monocystidae is problematic because cardinal characters are lacking, and the commonly cited character, a trophozoite with no anterior differentiation, is violated in most genera placed in the family. For the first time, a molecular phylogeny is presented that includes 3 genera of monocystids with diverse cell morphology (including the new species) and supports the monophyly of the family. The only morphological character that may be used to diagnose the Monocystidae is the morphology of oocysts, which are fusiform with extended terminal tips. A comparison of oocysts from 7 parasites recovered from local earthworms, including from 3 monocystid species in the phylogeny, confirms the utility of this diagnostic trait. The 2 hosts of the new species were most likely introduced from Japan, so the range of Apolocystis likely extends into East Asia.

Cystoisospora suis infection in suckling piglets in Brazil: Prevalence and associated factors

Piglet coccidiosis is a parasitic disease caused by the protozoan Cystoisospora suis, which is regarded as the most prevalent gastrointestinal parasite in intensive pig farms. Despite the availability of highly effective chemo-metaphylaxis (toltrazuril), coccidiosis is still prevalent in European and other countries. We conducted a cross-sectional study on swine farms in Brazil, to assess the prevalence of Cystoisospora suis in fecal samples and determined the associated factors. In total, 666 litters from 50 farms were sampled twice within one week between samplings (mean age at sampling: 10.75 and 17.7 days). Of 666 litters, 225 (33.8%) were positive at least once, and the expected within farm prevalence of C. suis oocysts was 32.9% (25.4-41.3%; 95% confidence interval). Oocysts were more prevalent in fecal samples collected from farms with diarrhea (odds ratio = 6.75). The room temperature was also positively associated with oocyst detection; a one-degree increase in room temperature increased the chance of a litter being positive by 23.2%. Up-to-date, this is the most comprehensive technical evidence of factors associated with C. suis infection in Brazilian industrial piglet farms.

Susceptibility of primary, secondary and suspected vectors to Plasmodium vivax and Plasmodium falciparum infection in Ethiopia

BACKGROUND

Insecticide-based vector control interventions in combination with case management with artemisinin-based combination therapy has reduced malaria incidence and prevalence worldwide. Current control methods focus on the primary malaria vectors, Anopheles gambiae sensu lato (s.l.) and the An. funestus group; however, the impact of secondary and suspected vectors has been either sidelined or received limited attention. Defining the susceptibility of secondary, suspected vector species to different parasites in time and space is essential for efficient malaria control and elimination programs. The aim of this study was to assess the susceptibility of An. gambiae s.l., An. coustani complex and An. pharoensis to Plasmodium vivax and P. falciparum infection in Ethiopia.

METHODS

Larvae of Anopheles spp. were collected from different aquatic habitats and reared to adults under laboratory conditions, with the temperature and humidity maintained at 27 ± 1 °C and 75 ± 5%, respectively. Adult female mosquitoes were identified to species as An. gambiae s.l., An. coustani complex and An. pharoensis. Females of these three Anopheles spp. were allowed to feed in parallel feeding assays on infected blood containing the same gametocytes isolated from P. falciparum and P. vivax gametocyte-positive patients by indirect membrane feeding assays. All blood-fed mosquitoes were held under laboratory conditions. After 7 days, all surviving mosquitoes were dissected to detect mid-gut oocyst and enumerated under a microscope.

RESULTS

Of 5915 female Anopheles mosquitoes exposed to gametocyte-infected blood, 2106 (35.6%)s fed successfully in the 32 independent infection experiments. There was a significant variation in feeding rates among An. gambiae s.l., An. pharoensis and An. coustani complex (G-test = 48.43, P = 3.049e-11). All three exposed mosquito species were receptive to P. vivax and P. falciparum infection development. The percentage of infected mosquitoes following feeding on an infected blood meal was significantly different among species (G-test = 6.49, P = 0.03886). The median infection intensity (II) for An. coustani complex, An. gambiae s.l. and An. pharoensis was 1.16, 2.00 and 1.25, respectively. Although the proportion of infected mosquitoes significantly differed in terms of II, infection rate (IR) and mean oocyst density among the species, mean oocyst density and IR were highly correlated with gametocyte density in all tests (P < 0.001).

CONCLUSION

Primary, secondary and suspected vectors were experimentally susceptible to both P. vivax and P. falciparum infection. An effective malaria elimination program might include surveillance and control tools which target secondary and suspected vectors that might play an outdoor transmission role, possibly resulting in reduced focal malaria transmission. Comparison of the three species' mean infection rates with standard deviation.

Worldwide Dispersion of Coccidia from Migratory Birds: First Report of Eimeria bazi Chauhan et Bhatia, 1970 (Eimeriidae) Outside Asia from Buff-Necked Ibises Theristicus caudatus (Boddaert, 1783) (Threskiornithidae) in South America

BACKGROUND

Eimeria spp. are coccidian protozoan parasites of domestic and wild animals. Pelecaniform birds are hosts of some Eimeria spp., however, from the family Threskiornithidae only one eimerian species is recorded, Eimeria bazi Chauhan et Bhatia, 1970 which was described from red-naped ibises Pseudibis papillosa (Temminck, 1824) in India. In this study, in turn, this species is morphologically and molecularly identified from buff-necked ibises Theristicus caudatus (Boddaert, 1783) in Brazil.

PURPOSE

This study aimed to report E. bazi from buff-necked ibises T. caudatus in southeastern Brazil, revealing the worldwide distribution of this coccidian species, in addition to providing preliminary genotypic identification via sequencing of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene.

METHODS

A total of 73 fecal samples were collected from a flock of buff-necked ibises, which remained on the campus of the Federal Rural University of Rio de Janeiro (Universidade Federal Rural do Rio de Janeiro-UFRRJ) from March 2019 to August 2020. Fecal samples were processed by the Sheather's method to recover oocysts. The morphological and morphometrical studies of the oocysts were performed using an optical microscope and graphic editing software. Molecular analysis was performed by sequencing of the COI gene, and the phylogenetic analysis was based in the neighbor-joining and maximum likelihood estimates.

RESULTS

Forty-five fecal samples were positive for oocysts identified as E. bazi. This oocysts are ovoidal, 26.2 × 18.9 μm, with smooth to slightly rough wall, c.1.7 μm thick. Micropyle robust and protruding, sometimes with a polar body attached. Oocyst residuum absent, but one or two small polar granules are present. Sporocysts ovoidal to lemon-shaped, 14.2 × 8.7 μm. The Stieda body is knob-like to rounded and sub-Stieda body is absent or vestigial. Sporocyst residuum is composed of granules often membrane-bound. Sporozoites are vermiform, with refractile bodies. This morphology was consistent with the original description of E. bazi from P. papillosa in India. Molecular analysis at the COI gene exhibited low similarity with coccidians sequenced for the same genic region deposited in GenBank, sitting E. bazi separately on the cladogram.

CONCLUSIONS

The morphological and molecular studies support the identification of E. bazi from T. caudatus in South America, thus revealing the wide distribution of this eimerian species in the world provided by migratory birds and/or with intercontinental distribution.

DNA-based quantification and counting of transmission stages provides different but complementary parasite load estimates: an example from rodent coccidia (Eimeria)

Background

Counting parasite transmission stages in faeces is the classical measurement to quantify “parasite load”. DNA-based quantifications of parasite intensities from faecal samples are relatively novel and often validated against such counts. When microscopic and molecular quantifications do not correlate, it is unclear whether oocyst counts or DNA-based intensity better reflects biologically meaningful concepts. Here, we investigate this issue using the example of Eimeria ferrisi (Coccidia), an intracellular parasite of house mice (Mus musculus).

Methods

We performed an infection experiment of house mice with E. ferrisi, in which the intensity of infection correlates with increased health impact on the host, measured as temporary weight loss during infection. We recorded the number of parasite transmissive stages (oocysts) per gram of faeces (OPG) and, as a DNA-based measurement, the number of Eimeria genome copies per gram of faeces for 10 days post-infection (dpi). We assessed weight loss relative to the day of experimental infection as a proxy of host health and evaluated whether DNA or oocyst counts are better predictors of host health.

Results

Absolute quantification of Eimeria DNA and oocyst counts showed similar but slightly diverging temporal patterns during 10 dpi. We detected Eimeria DNA earlier than the first appearance of oocysts in faeces. Additionally, Eimeria OPGs within each dpi did not explain parasite DNA intensity. Early dpi were characterized by high DNA intensity with low oocyst counts, while late infections showed the opposite pattern. The intensity of Eimeria DNA was consistently a stronger predictor of either maximal weight loss (1 value per animal during the infection course) or weight loss on each day during the experiment when controlling for between-dpi and between-individual variance.

Conclusions

Eimeria ferrisi oocyst counts correlate weakly with parasite intensity assessed through DNA quantification. DNA is likely partially derived from life-cycle stages other than transmissive oocysts. DNA-based intensities predict health outcomes of infection for the host more robustly than counts of transmissive stages. We conclude that DNA-based quantifications should not necessarily require validation against counts of transmissive stages. Instead, DNA-based load estimates should be evaluated as complementary sources of information with potential specific biological relevance for each host-parasite system.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05119-0.

A portfolio of geographically distinct laboratory-adapted Plasmodium falciparum clones with consistent infection rates in Anopheles mosquitoes

Background

The ability to culture Plasmodium falciparum continuously in vitro has enabled stable access to asexual and sexual parasites for malaria research. The portfolio of isolates has remained limited and research is still largely based on NF54 and its derived clone 3D7. Since 1978, isolates were collected and cryopreserved at Radboudumc from patients presenting at the hospital. Here, procedures are described for culture adaptation of asexual parasites, cloning and production of sexual stage parasites responsible for transmission (gametocytes) and production of oocysts in Anopheles mosquitoes. This study aimed to identify new culture-adapted transmissible P. falciparum isolates, originating from distinct geographical locations.

Methods

Out of a collection of 121 P. falciparum isolates stored in liquid nitrogen, 21 from different geographical origin were selected for initial testing. Isolates were evaluated for their ability to be asexually cultured in vitro, their gametocyte production capacity, and consistent generation of oocysts.

Results

Out of 21 isolates tested, twelve were excluded from further analysis due to lack of mature gametocyte production (n = 1) or generation of satisfactory numbers of oocysts in mosquitoes (n = 11). Nine isolates fulfilled selection criteria and were cloned by limiting dilution and retested. After cloning, one isolate was excluded for not showing transmission. The remaining eight isolates transmitted to Anopheles stephensi or Anopheles coluzzii mosquitoes and were categorized into two groups with a reproducible mean oocyst infection intensity above (n = 5) or below five (n = 3).

Conclusions

These new P. falciparum culture-adapted isolates with reproducible transmission to Anopheles mosquitoes are a valuable addition to the malaria research tool box. They can aid in the development of malaria interventions and will be particularly useful for those studying malaria transmission.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03912-x.

FIRST REPORT OF GENUS Cryptosporidium IN CERVIDS SPECIES: Mazama americana, Mazama nana AND Blastocerus dichotomus

We analyzed Cryptosporidium spp. in fecal samples of wild cervids (Ozotoceros bezoarticus, Blastocerus dichotomus, Mazama nana, Mazama americana, and Mazama bororo) from many Brazilian regions, a fact unprecedented in the literature. Sniffer dogs were used to collect 936 fecal samples of cervids from 14 Brazilian localities. Cervids species were identified using polymerase chain reaction (PCR) performed from genomic DNA extracted from 563 fecal samples of Ozotoceros bezoarticus, Blastocerus dichotomus, Mazama nana, Mazama americana, and Mazama bororo. Cryptosporidium spp. oocyst screening was performed using malachite green negative staining. Nested PCR (nPCR) protocols targeting the 18S rRNA and GP60 genes followed by genetic sequencing were performed for Cryptosporidium spp. detection and Cryptosporidium parvum subtyping, respectively. Nested PCR targeting actin gene and genetic sequencing were performed in samples with non-identified Cryptosporidium species by 18S rRNA amplicon sequencing. The association between the occurrence of Cryptosporidium and the presence of bovines in the same locality was evaluated using Fisher's exact test. The positivity rates of diagnostic methods were compared by McNemar test and the Kappa correlation coefficient. The prevalence rates of Cryptosporidium spp. in cervids were 1.42% (8/563) and 0.36% (2/563) by nPCR and malachite green negative staining, respectively. C. parvum IIaA16G3R1 isolate was identified in three fecal samples from M. americana, two from M. nana and one from B. dichotomus. Cryptosporidium ryanae were found in one sample from B. dichotomus. We identified a new Cryptosporidium genotype, named Cryptosporidium deer genotype BR, from one M. americana fecal sample.

Supplementary morphological data and molecular analyses of Eimeria labbeana (Labbé, 1896) Pinto, 1928 (Chromista: Miozoa: Eimeriidae) from columbiform birds in Portugal

Columbiformes have a worldwide distribution, of which 166 species occur in Eurasia. They have been reported parasitized by coccidians recurrently in recent years; however, Eimeria labbeana (Labbé, 1896) Pinto, 1928, which is first Eimeria sp. from Columbiformes described in the late nineteenth century, is not taxonomically identified by its oocysts since the 1930s. In this context, the current study aimed to supplement the morphology of E. labbeana from Eurasian collared doves Streptopelia decaocto Frivaldszky, 1838 and from a common woodpigeon Columba palumbus Linnaeus, 1758 in Portugal, providing a preliminary genotypic characterization. Three of the four columbiforms were positive for oocysts identified as E. labbeana, which were morphologically revised as having micropyles, in addition to other minor adjustments. Oocysts from S. decaocto and C. palumbus were morphologically identical and equivalent in all morphometric aspects, besides having genotypic similarity of 99.5%. Phylogenetic analysis based on the mitochondrial cytochrome c oxidase subunit 1 gene resulted in a large clade with Eimeria spp. and Isospora spp. from different vertebrates and low similarity between Eimeria spp. from Columbiformes, whereas the phylogenetic analysis based on the small subunit ribosomal RNA gene resulted in well-supported monophyletic groups, including one with the coccidians of columbiform birds.

In vitro activity, safety and in vivo efficacy of the novel bumped kinase inhibitor BKI-1748 in non-pregnant and pregnant mice experimentally infected with Neospora caninum tachyzoites and Toxoplasma gondii oocysts

Bumped kinase inhibitors (BKIs) target the apicomplexan calcium-dependent protein kinase 1 (CDPK1). BKI-1748, a 5-aminopyrazole-4-carboxamide compound when added to fibroblast cells concomitantly to the time of infection, inhibited proliferation of apicomplexan parasites at EC50s of 165 nM (Neospora caninum) and 43 nM (Toxoplasma gondii). Immunofluorescence and electron microscopy showed that addition of 2.5 μM BKI-1748 to infected HFF monolayers transformed parasites into multinucleated schizont-like complexes (MNCs) containing newly formed zoites, which were unable to separate and form infective tachyzoites or undergo egress. In zebrafish (Danio rerio) embryo development assays, no embryonic impairment was detected within 96 h at BKI-1748 concentrations up to 10 μM. In pregnant mice, BKI-1748 applied at days 9-13 of pregnancy at a dose of 20 mg/kg/day was safe and no pregnancy interference was observed. The efficacy of BKI-1748 was assessed in standardized pregnant mouse models infected with N. caninum (NcSpain-7) tachyzoites or T. gondii (TgShSp1) oocysts. In both models, treatments resulted in increased pup survival and profound inhibition of vertical transmission. However, in dams and non-pregnant mice, BKI-1748 treatments resulted in significantly decreased cerebral parasite loads only in T. gondii infected mice. In the T. gondii-model, ocular infection was detected in 10 out of 12 adult mice of the control group, but only in 3 out of 12 mice in the BKI-1748-treated group. Thus, TgShSp1 oocyst infection is a suitable model to study both cerebral and ocular infection by T. gondii. BKI-1748 represents an interesting candidate for follow-up studies on neosporosis and toxoplasmosis in larger animal models.

GAMOGONY OF SARCOCYSTIS STRIXI IN MAMMALIAN CELL CULTURES

We are interested in the disease ecology of Sarcocystis species that infect birds of prey as definitive and intermediate hosts. The present study was done to test our hypothesis that a laboratory model can be developed for sarcocystis infection in mammals using gamma interferon gene knockout (KO) mice as a source of Sarcocystis strixi bradyzoites and mammalian cell cultures as a source of sporulated S. strixi oocysts. Sporocysts of S. strixi from a naturally infected barred owl (Strix varia) were fed to KO mice to produce sarcocysts, and the enclosed bradyzoites were obtained by acid-pepsin digestion of abdominal and thigh muscles. Bradyzoites, metrocytes, and an unusual spherical stage were seen in digest before the inoculation of host cells. The spherical stages stained dark with Giemsa stain, but no nucleus was observed, and they were seen free and associated with the concave portion of some bradyzoites. Examination of infected cell cultures demonstrated that macrogamonts and microgamonts were present at 24 hr post-inoculation. Since sporulated oocysts were not observed, we had to reject our current hypothesis.

Identification of a Cyclospora cayetanensis Oocyst Antigens and Their Validity in the Detection of Immunogenic Patterns of Cyclosporiasis Patients

INTRODUCTION

The diagnosis of cyclosporiasis is currently based on the microscopic detection of oocysts, which may provide invalid results. The availability of simple, objective immunological screening tests would facilitate epidemiological studies of cyclosporiasis. Therefore, the present study aimed to identify the antigens of Cyclospora cayetanensis oocysts and their validity in serodiagnosis.

METHODS

According to parasitological and molecular diagnoses, three study groups were specified. Group (G) I included 30 patients with cyclosporiasis, GII included 12 patients with other parasitic infections, and GIII included 16 healthy subjects. SDS-PAGE was used to analyse C. cayetanensis antigens, and the validity of western blotting and enzyme-linked immunosorbent assays (ELISAs) was then assessed amongst the sera of all study groups.

RESULTS

The C. cayetanensis antigenic profile showed eight characteristic bands with molecular weights ranging from 14 to 175 kDa. Western blot analysis of sera revealed 93.3% (28/30 of GI) and 92.8% (26/28 of GII and III) sensitivity and specificity, respectively, dividing the patients in GI into four subgroups. The most frequent diagnostic bands (71.4% of GI sera) showed weights of 26-28 kDa, followed by 71 kDa (53.6%). ELISA sensitivity was 90% (27/30), and specificity was 78.6%. Validation showed perfect agreement between the PCR and western blot results, and ELISA presented substantial agreement with both the PCR and western blot results.

CONCLUSIONS

Our findings suggest the existence of high immunogenic diversity in C. cayetanensis and indicate that the 26-28 kDa immunogenic groups may potentially be used as a diagnostic marker of cyclosporiasis. Due to the high validity of ELISA, it might be the test of choice for the routine serodiagnosis of cyclosporiasis.

Sporulation rate and viability of Eimeria tenella oocysts stored in potassium sorbate solution

In order to find a new preservation solution for avian coccidial oocysts that can replace potassium dichromate (K₂Cr₂O₇) solution, Eimeria tenella oocysts were preserved in 0.1 to 10% potassium sorbate (C₆H₇KO₂) solution in this study. The results showed that there was no significant difference between the sporulation rate of E. tenella oocysts preserved in 0.1 to 10% C₆H₇KO₂ solution and in 2.5% K₂Cr₂O₇ solution (p > 0.05). The 0.5 to 10% C₆H₇KO₂ solution could also effectively inhibit the growth of bacterial microorganisms. E. tenella oocysts preserved in 1% C₆H₇KO₂ solution at 4 °C for 3, 6, 9, and 12 months, with the oocyst production of E. tenella oocysts being 1.3-, 1.2-, 1.6-, and 1.3-fold higher than that of oocysts stored in 2.5% K₂Cr₂O₇ solution (p < 0.05). In conclusion, C₆H₇KO₂ could replace K₂Cr₂O₇ as the preservation solution of avian coccidial oocysts.

Outbreaks of clinical toxoplasmosis in humans: five decades of personal experience, perspectives and lessons learned

Background

The protozoan parasite Toxoplasma gondii has a worldwide distribution and a very wide host range, infecting most warm-blooded hosts. Approximately 30% of humanity is infected with T. gondii, but clinical toxoplasmosis is relatively infrequent. Toxoplasmosis has a wide range of clinical symptoms involving almost all organ systems. In most persons that acquire infection postnatally, symptoms (when present) are mild and mimic other diseases such as flu, Lyme disease, Q fever, hematological alterations, or mumps. It is likely that clinical disease is more common than reported. The ingestion of infected meat or food and water contaminated with oocysts are the two main modes of postnatal transmission of Toxoplasma gondii. The infective dose and the incubation period of T. gondii infection are unknown because there are no human volunteer experiments.

Methods

Here, I have critically reviewed outbreaks of clinical toxoplasmosis in humans for the past 55 years, 1966–2020. Information from oocyst-acquired versus meat-acquired infections was assessed separately.

Results

Most outbreaks were from Brazil. There were no apparent differences in types or severity of symptoms in meat- versus oocyst-acquired infections. Fever, cervical lymphadenopathy, myalgia, and fatigue were the most important symptoms, and these symptoms were not age-dependent. The incubation period was 7–30 days. A genetic predisposition to cause eye disease is suspected in the parasites responsible for three outbreaks (in Brazil, Canada, and India). Only a few T. gondii tissue cysts might suffice to cause infection, as indicated by outbreaks affecting some (but not all) individuals sharing a meal of infected meat.

Conclusions

Whether the high frequency of outbreaks of toxoplasmosis in humans in Brazil is related to environmental contamination, poor hygiene, socioeconomic conditions, or to genotypes of T. gondii needs investigation.

Graphic Abstract

Oocyst shedding patterns of Eimeria species and their association with management and performance at ten rose veal starter farms in the Netherlands

Coccidiosis at rose veal starter farms is often diagnosed however, this was the first study performed considering this topic on this type of rearing unit. The objective of this study was to identify Eimeria species faecal shedding patterns at ten Dutch rose veal starter farms during rearing. Further objectives were to investigate associations with (gut) health, production and management decisions. Faecal samples from twelve randomly selected calves per farm were collected weekly during 9 consecutive weeks. Thereafter samples were pooled in a predetermined composition of six. These calves were clinically evaluated every sample visit and weighed at the first and last visit. Laboratory tests included a flotation test of the samples. If this yielded Eimeria oocysts, both oocysts per gram feces (OPG) and species differentiation were established using a modified McMaster method. Management parameters and technical herd results were identified after finalizing the study period using a questionnaire. Studied patterns in oocyst shedding included the pool's cumulated OPG, maximum OPG level and the number of sample days (SD) that OPG exceeded a confirmed level. Statistical analysis included univariate and multivariate analysis. Associated (p < 0.10) OPG patterns considering rumen fill, faecal consistency and average daily weight gain (ADG) were tested using a model with herd included as random effect. RESULTS: on all ten farms E. alabamensis, E.bovis and E. zuernii besides non-pathogenic species were identified, often as mixed infections. Peak OPG occurred predominately at SD 21 and 28 (E. alabamensis and E. bovis), and at SD 42 (E. zuernii). In 16 pools, OPG levels ≥500 for E. bovis or E. zuernii, were found. Significant correlation (p < 0.0001) showed between the log₁₀ OPG of pathogenic Eimeria and of all Eimeria species. Multivariate analysis showed significant correlation between cumulative faecal consistency scores and cumulative log₁₀ OPG of pathogenic Eimeria species (β = 0.16; p = 0.008). Pools exceeding 750 OPG for E. bovis showed 93 g lower ADG and pools experiencing ≥2 SD with >1000 OPG for E. alabamensis 141 g lower ADG. From the questionnaire we identified lower cumulated OPG of all Eimeria species except for E. bovis at farms where the units were cleaned before arrival of the calves. CONCLUSION: As a rule, on Dutch rose veal starter farms, mixed Eimeria infections occur, but shedding patterns differ between farms. Clinical and growth performance is related to OPG patterns found. Cleaning units before arrival of calves lowers oocyst shedding during the rearing period.

The impact of maturity on the ability of Eimeria acervulina and Eimeria meleagrimitis oocysts to sporulate

The sporulation of oocysts of Eimeria that infect poultry is known to be under the influence of environmental conditions, including temperature, oxygen supply, and moisture. However, even when these conditions are optimal, the level of sporulation can remain low. The effect of oocyst maturity on their ability to sporulate was investigated for two species of Eimeria: E. acervulina of chickens, and E. meleagrimitis of turkeys. After oral infection of birds, oocysts were collected at their production site in the intestine at different times around the prepatent period. The percentage of sporulation was determined by observation of 100 oocysts for each sample. With E. acervulina, it was observed that sporulation depended on the time of collection of the oocysts in the intestine, and that it increased with aging oocysts (from 5% to 40% globally in 8 h). With E. meleagrimitis, sporulation remained low with oocysts collected in the duodenum (below 20%), but oocysts collected in the midgut and in the lower intestine sporulated more efficiently (around 80%) than oocysts collected in the duodenum at the same time. One explanation for these results is the assumption that oocysts may be produced before fertilization, and that microgametes have not yet fertilized the newly produced oocysts. As time goes on, more oocysts would be fertilized, locally in the duodenum for E. acervulina, and descending along the gut for E. meleagrimitis. This hypothesis needs to be investigated further, but it could lead to new approaches to control these parasites by targeting the microgametes.

Distribution, redescription, and molecular identification of Isospora striata McQuistion et al. 1997 (Eimeriidae), from woodcreepers (Dendrocolaptidae) in South America

Woodcreepers are passerines of the family Dendrocolaptidae, which have a high forest dependency. The current work aimed to redescribe Isospora striata McQuistion et al. 1997, from two new hosts in protected areas in Brazil, revealing new localities of parasitism, in addition to providing preliminary genotypic identifications via sequencing of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene from both host species. Isospora striata has oocysts that are subspheroidal to ovoidal, 19.4 × 16.8 μm with smooth wall. Oocyst residuum is absent, but micropyle and polar granules are present. Sporocysts are ovoidal, 13.6 × 8.3 μm, with both Stieda and sub-Stieda bodies. Sporocyst residuum is present and sporozoites with refractile body, nucleus, and striations. The morphological study and the 100% similarity in sequencing of the COI gene between samples of different dendrocolaptid species confirmed the identification of a single species, supporting the identification of I. striata in the Brazilian Atlantic forest and consequently the wide distribution of this coccidian species in the Neotropical Region.

Digging into Toxoplasma gondii infections via soil: A quantitative microbial risk assessment approach

Soil has been identified as an important source of exposure to a variety of chemical and biological contaminants. Toxoplasma gondii is one of those potential biological contaminants associated with serious health effects in pregnant women and immunocompromised patients. Gardening or consumption of homegrown vegetables may present an important route of T. gondii infection via accidental ingestion of soil. In the Netherlands, there is quantitative information on the risk of T. gondii infection via meat products, but not on the risk of infection through soil. The objective of this study was to develop a quantitative microbial risk assessment (QMRA) model for estimating the risk associated with T. gondii exposure via accidental soil ingestion in the Netherlands. In order to obtain the needed information, a magnetic capture method for detection of T. gondii oocysts in soil samples was developed, and T. gondii DNA was detected using qPCR targeting the 529 bp repeat element. The method was shown to provide 95% probability of detection (95% CI: 88-100%) when at least 34 oocysts are present in 25 g of soil. T. gondii DNA was detected in 5 of 148 soil samples with interpretable results (3%, 95% CI: 1.5-7.7%). Results for 18 samples were not interpretable due to PCR inhibition. The estimated amount of oocysts presented in qPCR positive samples was quantified by a linear model, and the amount varied from 8 to 478 in 25 g of soil. The estimated incidence rate of T. gondii infection from the QMRA model via soil varied from 0.3 to 1.8 per 1000 individuals per day. Several data gaps (e.g., soil contamination/ingestion and oocysts viability) have been identified in this study, the structure of the model can be applied to obtain more accurate estimates of the risk of T. gondii infection via soil when data become available.

Occurrence of Toxoplasma gondii on Raw Leafy Vegetables in Gaza, Palestine

ABSTRACT

Toxoplasma gondii, a ubiquitous obligate intracellular parasite that can infect homeothermic animals, is one of the main pathogens causing foodborne diseases worldwide. In Gaza, Palestine, leafy vegetables are frequently eaten raw. The present study was carried out to investigate the occurrence of T. gondii oocyst in local leafy vegetables. Fifty samples each of six species of leafy plants sold in open-air markets, in supermarkets, and by retail sellers were randomly collected from March to August 2019, for a total of 300 samples. The samples were examined by light microscopy after flotation in Sheather's sucrose solution and by PCR assay of the pelleted samples. All suspect T. gondii oocysts were confirmed with a PCR assay. With the PCR assay of the pelleted samples, only 19 (6.33%) of the 300 samples were positive for T. gondii, whereas with the Sheather's flotation method, 35 (11.66%) of the 300 samples were positive. With the PCR assay, among the six plant types mint had the highest T. gondii prevalence (10.00% of samples) followed by watercress and dill (both 8.00%), parsley (6.00%), thyme (4.00%), and lettuce (2.00%). Even though the relative prevalence of T. gondii in the contaminated plant species was similar with both the PCR and Sheather's flotation methods, the actual prevalences were different. With Sheather's flotation, T. gondii prevalence was highest in mint (18.00% of samples) followed by watercress (14.00%), dill (13.00%), parsley (10.00%), thyme (10.00%), and lettuce (6.00%). The relationship between T. gondii contamination and the time of year the samples were collected was also significant. The highest prevalence recorded was in July followed by June and August. These findings indicate that leafy vegetables, particularly mint, can be contaminated with T. gondii and are a potential risk factor for transmitting T. gondii to humans in Gaza, Palestine.

HIGHLIGHTS

Molecular characterization of Cryptosporidium spp. from domestic pigs in Argentina

Cryptosporidiosis in pigs is caused by different Cryptosporidium species or genotypes, with C. suis and C. scrofarum considered porcine specific species. There is scarce information on Cryptosporidium infection in pigs in South America. A total of 520 individual faecal samples were obtained from 1, 2, 3 and 4 week old piglets (n = 130 from each age group), from 13 Argentinean intensive pig farms. The diagnosis of species of Cryptosporidium combined microscopy and molecular techniques. Genotyping from samples with Cryptosporidium oocysts at microscopy was performed by genus-specific and species-specific nested PCR targeting 18S rRNA gene fragments, and sequencing. Microscopic analysis detected Cryptosporidium oocysts in 47/520 (9%) faecal samples from 11/13 (85%) farms, with farm infection rates between 0 and 17.5%. Presence of Cryptosporidium oocysts was associated with diarrhea. The proportion of microscopically positive samples was not associated with piglet age. A total of 15/47 (32% of samples with oocyst compatible structures) were positive by genus and species-specific nested PCR. Species-specific PCR and sequencing showed presence of C. suis, C. scrofarum, and both species in 3, 8 and 4 samples, respectively. The proportion of positive samples on each specific PCR was similar between age groups, being C. suis proportion slightly higher in 4 week old piglets. The use of molecular tools allowed the confirmation of C. suis and C. scrofarum infection in Argentinean pigs. Cryptosporidiosis was widely distributed in the main pig husbandry area from Argentina, with a low to moderate intra farm infection rate.

Isospora oliveirai n. sp. (Chromista: Miozoa: Eimeriidae) from the Greenish Schiffornis Schiffornis virescens (Lafresnaye, 1838) (Passeriformes: Tyranni: Tityridae) in South America

BACKGROUND

Coccidia are obligatory intracellular parasites with at least one intestinal phase in their life cycles, being Isospora Schneider, 1881 the main coccidian genus related to the order Passeriformes. However, there is no record of isosporans from the passerine family Tityridae, which is the family of the greenish schiffornis Schiffornis virescens (Lafresnaye, 1838).

PURPOSE

This study aimed to examine the faeces from a greenish schiffornis S. virescens captured in the Itatiaia National Park, State of Rio de Janeiro, Southeastern Brazil, to determine what coccidian parasites were present.

METHODS

Only one specimen of Schiffornis virescens was captured with mist nets. Coccidian oocysts were recovered from the fecal samples by flotation in Sheather's saturated solution. Morphological observations, line drawings, photomicrographs and measurements were made in optical microscopy and digitally edited. The molecular analysis included the study of the sequence of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene, with phylogenetic reconstructions based on the Neighbor-Joining and Maximum Likelihood analysis.

RESULTS

An Isospora sp. considered as new to science is described and identified from Schiffornis virescens (Lafresnaye, 1838). Isospora oliveirai n. sp. has oocysts that are subspheroidal, 26.0 × 24.8 μm, with rough, bilayered wall, c.2.5 μm thick. Micropyle and oocyst residuum absent, but one to six polar granules are present. Sporocysts lemon-shaped, 18.1 × 10.9 μm. The Stieda body is knob-like to half-moon-shaped and sub-Stieda is rounded. Sporocyst residuum is present, composed of scattered spherules of different sizes. Sporozoites are vermiform, with refractile bodies and nucleus. Molecular analysis at the COI gene exhibited similarity of 97% with Isospora serinuse Yang, Brice, Elliot et Ryan, 2015 from island canaries Serinus canaria (Linnaeus, 1758), and Isospora spp. from great tits Parus major (Linnaeus, 1758) and European robins Erithacus rubecula (Linnaeus, 1758).

CONCLUSION

Based on the morphological and molecular features, I. oliveirai is considered as new to science and the first coccidian species recorded from Tityridae.

tenella oocyst purification and optimization of centrifugation conditions for improved recovery of oocysts and sporocysts

Saturated salt floatation method is widely used for coccidian oocyst purification. However, the repeated procedures and inefficient oocysts recovery rate are a continuous challenge. This study aimed to investigate the best suitable floatation solution, along with optimal centrifugation speed and time for Eimeria tenella (E. tenella) oocyst and sporocyst purification. Different floatation solutions i-e, saturated salt, Sheather's sugar and sodium hypochlorite (NaClO) at 20-60% concentrations were used to purify oocyst. It was found that about 96.99% oocysts (8609×g for 10 min) were recovered under these conditions without any effect on the viability of sporocysts. The recovery rate of oocysts using 50% NaClO (V/V) was significantly higher than 35% saturated salt flotation solution (P < 0.05). The optimal method for purification of oocysts based our experimentation was centrifugation at 8609×g for 3 min using 50% NaClO floatation solution, and the optimized centrifugation conditions for improved recovery of sporocysts (about 99.3%) were at 2152×g for 5 min. The present study provided a better method for the coccidian oocyst purification, which could be successfully adopted as a better alternative to existing techniques commonly used for investigations/research pertaining to coccidia.

Cryptosporidium spp. in Columba livia Gmelin, 1789 (Columbiformes: Columbidae) free-living pigeons from urban areas in Pelotas, Rio Grande do Sul, Brazil

Cryptosporidium spp. are parasites with zoonotic potential that cause intestinal diseases, generally intense diarrheal, on their hosts, which tend to be immunocompromised. Large populations of pigeons in urban environments can lead to greater human exposure to Cryptosporidium spp., as this bird is considered a potential reservoir and is able to transmit several pathogens. This study aimed in determining the occurrence of Cryptosporidium spp. oocysts in feces of free-living pigeons (Columba livia) found in urban areas in the city of Pelotas, Rio Grande do Sul, south of Brazil. Fecal samples (n = 50) were collected from young and adult pigeons captured in different locations in the urban area and the parasitological diagnosis was performed through Ritchie's modified technique and Kinyoun's technique. Among the 50 samples, 18% (IC95% 9.7-30.8) were positive for Cryptosporidium spp. with a low number of oocysts being detected on fecal smears. Our results confirmed the occurrence of Cryptosporidium spp. oocysts in feces of free-living pigeons from the urban area of the city of Pelotas. This is the first report of Cryptosporidium spp. oocysts in feces of pigeons in south Brazil. This data has epidemiological significance because the oocysts could be from zoonotic species, which consequently shows that humans might be exposed to infection.

Endogenous Developmental Cycle of the Human Coccidian Cyclospora cayetanensis

Cyclospora cayetanensis is a coccidian parasite of humans of known and growing importance. However, we are surprisingly naïve as to our understanding of how to diagnose it and how it develops inside the human body. Here we provide details of the developmental stages of C. cayetanensis in the gallbladder of a 33-yr-old male with human immunodeficiency virus. The gallbladder was removed surgically in 2001 because of severe abdominal pain. For the present study, the archived paraffin block of gallbladder was processed for light microscopy and transmission electron microscopy (TEM). Histological sections were examined after staining with hematoxylin and eosin (HE) or using the periodic acid Schiff (PAS) reaction. Immature and mature asexual stages, gamonts, and oocysts were seen in epithelial cells, both in the superficial epithelium and in glands. The merozoites were present singly, in pairs, and 3 or more in a single parasitophorous vacuole in the host cytoplasm. Up to 6 nuclei were seen in immature schizonts without evidence of merozoite formation. Mature schizonts were 7.6 × 5.1 μm and contained up to 10, 3-4 μm long merozoites. Merozoites were 0.6 to 2.0 μm wide, and their shape varied from pear-shaped to slender. Merozoites were generally PAS-positive; however, some were intensely positive, some had only minute granules, while others were PAS-negative. The microgamonts (male) were 6.6 × 5.2 μm and contained fewer than 20 microgametes around a residual body. The microgametes were up to 2 μm long and were flagellated. Macrogamonts (female) contained distinctive eosinophilic wall-forming bodies that varied in size and were less than 1 μm in HE-stained sections. Macrogamonts were 5.8-6.5 × 5.3-6.5 μm. Oocysts in sections were unsporulated and had a diameter of 5.7-7.5 μm. The TEM examination confirmed the histologic findings. The DNA extracted from paraffin sections was confirmed as C. cayetanensis with real-time PCR. The detailed description of the life cycle stages of C. cayetanensis reported here in an immunosuppressed patient could facilitate histopathologic diagnosis of this parasite. We have shown that the parasite's development more closely resembles that of Cystoisospora than Eimeria and that the parasite has multiple nuclei per immature meront indicating schizogony, and we have undermined evidence for a Type II meront.

Detection of Toxoplasma gondii oocysts in fresh vegetables and berry fruits

BACKGROUND

Toxoplasma gondii is the third most important contributor to health burden caused by food-borne illness. Ingestion of tissue cysts from undercooked meat is an important source of horizontal transmission to humans. However, there is an increasing awareness of the consumption of fresh fruit and vegetables, as a possible source for oocyst transmission, since this stage of the parasite can persist and remain infective in soil and water for long time. Herein, we outline findings related with detection of T. gondii oocysts in vegetables and berry fruits, which are usually raw consumed. The procedure includes the estimation of the number of oocysts.

METHODS

Food samples were collected from local producers and supermarket suppliers. Toxoplasma gondii oocysts were concentrated after washing the samples by applying high resolution water filtration and immunomagnetic separation (method 1623.1: EPA 816-R-12-001-Jan 2012), in order to (i) remove potential Cryptosporidium spp. oocysts and Giardia spp. cysts present in the samples; and (ii) select T. gondii oocysts. Toxoplasma gondii oocyst detection and an estimation of their numbers was performed by conventional PCR and real time qPCR, using specific primers for a 183-bp sequence of the T. gondii repetitive DNA region. All PCR-positive DNA samples were purified and sequenced. Restriction enzyme digestion with EcoRV endonuclease confirmed the presence of the T. gondii DNA fragment. In addition, the presence of the parasite was observed by fluorescent microscopy, taking advantage of the oocysts autofluorescence under UV light.

RESULTS

Forty percent of the analysed samples (95% CI: 25.5-56.5%) presented the expected PCR and digested DNA fragments. These fragments were confirmed by sequencing. Microscopic autofluorescence supported the presence of T. gondii-like oocysts. The estimated mean (± SE) oocyst concentration was 23.5 ± 12.1 oocysts/g, with a range of 0.6-179.9 oocysts/g.

CONCLUSIONS

Our findings provide relevant evidence of contamination of fresh vegetables and berry fruits with T. gondii oocysts.

Mouse Models for Use in Cryptosporidium Infection Studies and Quantification of Parasite Burden Using Flow Cytometry, qPCR, and Histopathology

Cryptosporidiosis threatens life of young children in developing countries and newborn calves around the world. No vaccine or therapy can prevent or cure this diarrhea-inducing enteric disease caused by Cryptosporidium spp. protozoan parasites. There is an essential need to discover new therapeutic drugs efficient in reducing parasite burden in infected individuals. Research therefore relies on reliable small animal models of cryptosporidiosis. Here, we present excellent mouse models which can efficiently mimic pathogenesis of human and bovine cryptosporidiosis. We also describe methods to purify C. parvum oocysts from stool and intestine of infected mice to facilitate oocyst quantification. Moreover, we present protocols using flow cytometry, quantitative polymerase chain reaction, and histopathology to accurately quantify parasite burden in stool or intestine samples.

Cell Culture Infectivity to Assess Chlorine Disinfection of Cryptosporidium Oocysts in Water

This chapter provides a detailed protocol to assess disinfection efficacy of chlorine against Cryptosporidium oocysts including the core chlorine disinfection assay, the in vitro cell culture infectivity assay, and microscopy analysis and data interpretation.

Evaluation of immunogenicity and protection of the Mic1-3 knockout Toxoplasma gondii live attenuated strain in the feline host

Toxoplasmosis is a zoonotic disease caused by the parasite Toxoplasma gondii. Up to a third of the global human population is estimated to carry a T. gondii infection, which can result in severe complications in immunocompromised individuals and pregnant women. Humans and animals can become infected by ingesting either tissue cysts containing T. gondii bradyzoites, from raw or undercooked meat, or sporulated oocysts from environmental sources. T. gondii oocysts are released in the faeces of cats and other felids, which are the parasite's definitive hosts, leading to environmental contamination. Therefore, vaccination of the feline host against T. gondii is an interesting strategy to interrupt the parasitic life cycle and subsequently limit contamination of intermediate hosts. With this goal in mind, we tested in cats, an attenuated live strain of T. gondii deleted for the Mic1 and Mic3 genes (Mic1-3KO) that was previously shown to be an efficient vaccine candidate in mouse and sheep models. Subcutaneous or oral vaccination routes induced a high specific antibody titer in the cat sera, indicating that the Mic1-3KO strain is immunogenic for cats. To assess protection induced by the vaccine candidate strain, we followed oocysts shedding by vaccinated cats, after oral challenge with a T. gondii wild-type strain. Surprisingly, a high antibody titer did not prevent cats from shedding oocysts from the challenge strain, regardless of the vaccination route. Our results show that the Mic1-3KO vaccine candidate is immunogenic in the feline host, is well tolerated and safe, but does not confer protection against oocysts shedding after natural infection with wild type T. gondii. This result highlights the particular relationship between T. gondii and its unique definitive host, which indicates the need for further investigations to improve vaccination strategies to limit environmental and livestock contaminations.

Morphological and molecular identification of Isospora massardi Lopes, Berto, Luz, Galvão, Ferreira & Lopes, 2014 (Chromista: Miozoa: Eimeriidae) from thrushes Turdus spp. (Passeriformes: Turdidae) in South America

In the current work, Isospora massardi Lopes, Berto, Luz, Galvão, Ferreira & Lopes, [10] is identified from white-necked thrushes Turdus albicollis Vieillot, 1818, rufous-bellied thrushes Turdus rufiventris Vieillot, 1818 and from a new host, the yellow-legged thrush Turdus flavipes (Vieillot, 1818) in a new locality, the Itatiaia National Park, in Southeastern Brazil, providing a preliminary genotypic characterization via sequencing of the mitochondrial cytochrome c oxidase subunit 1 (COI) and 18S small subunit ribosomal RNA genes. The oocysts and sporocysts of I. massardi of the current study are morphologically similar to the original description and are uniform in the proportionality of width on length, but exhibited different patterns of size associated with each host species. Furthermore, a genotypic difference of 3% was found in the COI sequences from T. flavipes and T. albicollis. Therefore, an ecological discussion is introduced aimed at associating these morphometric and genotypic differences with an ongoing speciation process.

Coccidia of Columbiformes: a taxonomic review of its Eimeriidae species and Eimeria columbinae n. sp. from Columbina talpacoti (Temminck, 1809) from Brazil

Coccidia (Chromista: Miozoa: Eimeriidae) of columbiform birds (Aves: Columbiformes) have been described since the end of the nineteenth century; however, some of these descriptions were poorly detailed or inconclusive. In this sense, the current work makes a detailed taxonomic revision reconsidering and organizing 18 Eimeria spp. and two Isospora spp. previously described or reported of Columbiformes. Along with this, a new species of Eimeria is morphologically and molecularly identified by the mitochondrial cytochrome c oxidase subunit 1 (COI) gene and by the 18S small subunit ribosomal RNA (18S) gene from the ruddy ground-dove Columbina talpacoti (Temminck, 1809) in the Médio Paraíba region of the State of Rio de Janeiro, southeastern Brazil. Eimeria columbinae n. sp. has subspheroidal oocysts, 14.7 × 13.2 μm, with smooth, bi-layered wall, ~ 1.1 μm and length/width ratio of 1.1. Micropyle and oocyst residuum are present, but polar granule is absent. Sporocysts are ellipsoidal to slightly asymmetrical, 9.0 × 5.1 μm, with both Stieda and sub-Stieda bodies. Sporocyst residuum present and sporozoites with refractile body and nucleus. This is the 19th description of an eimerian from Columbiformes in the World, and the second to have a molecular identification of the COI and 18S genes.

Isospora borbai n. sp. (Chromista: Apicomplexa: Eimeriidae) from gnateaters Conopophaga spp. (Passeriformes: Tyranni: Conopophagidae) in South America

BACKGROUND

The gnateaters Conopophaga spp. are insectivorous passerines commonly observed in high and humid forests, where they remain lodged in thin branches and, sometimes, they fly to the ground to catch insects. The insectivorous feeding habit is related to low prevalence and density of coccidians in passerines; however, several coccidian species are recorded for families of insectivorous passerines.

PURPOSE

This study aimed to examine the feces from gnateaters Conopophaga spp. captured in the municipality of Barra Mansa and in the Itatiaia National Park, State of Rio de Janeiro, Southeastern Brazil, to determine what coccidian parasites were present.

METHODS

Nine gnateaters were captured with mist nets. Coccidian oocysts were recovered from the fecal samples by flotation in Sheather's saturated solution. Morphological observations, line drawings, photomicrographs and measurements were made in optical microscopy and digitally edited. The molecular analysis included the study of the sequence of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene, with phylogenetic reconstructions based on the neighbor-joining and maximum likelihood analysis.

RESULTS

Four Conopophaga spp. were positive for oocysts. An Isospora sp. considered as new to science is described and identified from Conopophaga melanops (Vieillot, 1818) and Conopophaga lineata (Wied, 1831). Isospora borbai n. sp. has oocysts that are subspheroidal, 17-22 × 15-22 (20.2 × 19.1) µm, with rough, bilayered wall, c.1.7 μm thick. Micropyle present, but without micropyle cap. Oocyst residuum absent, but one or two polar granules are present. Sporocysts are ellipsoidal, 12-15 × 8-11 (14.1 × 9.1) µm. The Stieda body is knob-like to half-moon-shaped and sub-Stieda body is rounded. Sporocyst residuum is present, composed of scattered spherules of different sizes. Sporozoites are vermiform with refractile body and nucleus. Molecular analysis at the cox1 gene exhibited similarity greater than 99% with Isospora spp. isolates from other Neotropical passerine birds.

CONCLUSION

Based on the morphological and molecular features, I. borbai is considered as new to science and the first coccidian species recorded from Conopophagidae.

A morphological and molecular comparison of Eimeria bovis-like oocysts (Apicomplexa: Eimeriidae) from European bison, Bison bonasus L., and cattle, Bos taurus L., and the development of two multiplex PCR assays for their identification

The European bison, Bison bonasus is the largest terrestrial mammal in Europe; it is also on the red list, being recognized as vulnerable to extinction by the International Union for Conservation of Nature. The species suffers from low genetic variability, rendering it vulnerable to various environmental and biological threats. This study presents the first molecular confirmation of Eimeria bovis infection in European bison, and details a 1708 bp nucleotide sequence of the 18S rRNA gene in European bison-derived E. bovis (GenBank: MK691697). It also describes two multiplex PCR assays based on 18S rRNA gene for identifying Eimeria bovis oocysts and developmental stages in European bison and cattle. These yielded DNA banding patterns common for those of Eimeria spp. (250 bp for the first assay and 305 bp for the second assay) and species-specific E. bovis DNA in positive samples (344 bp and 586 bp, respectively). Both multiplex PCRs yielded bands characteristic of Eimeria spp. and E. bovis in samples containing DNA of oocysts from both bison and cattle. Moreover, convergent results were obtained for the DNA of the wall of colon in both assays, indicating the presence of developmental stages of Eimeria spp. other than E. bovis. Despite displaying the same sporulation time (four days), and similar general morphological features, the E. bovis oocysts derived from European bison were significantly narrower than those obtained from cattle (t = -6.19, p < 0.001), with a significantly higher shape index (length/width ratio) (t = 3.94, p <  0.001). The result provides further evidence for infection of European bison with a highly-pathogenic bovine protozoan, E. bovis.

Oxidative stress linked to changes of cholinesterase and adenosine deaminase activities in experimentally infected chicken chicks with Eimeria spp

Both oxidative stress and alterations in adenosinergic and cholinergic systems participate in initiation and progression of parasitic infectious diseases. Nevertheless, the involvement of these pathways during eimeriosis remains poorly understood. Therefore, the aim of this study was to evaluate the involvement of adenosinergic and cholinergic systems in regulation of inflammatory response and oxidative stress in chicken chicks experimentally infected with Eimeria spp. Two groups were formed for comparison at 3 time points (days 5, 10 and 15) of infection (PI): uninfected (control) and infected. Erythrocyte counts, hematocrit and hemoglobin levels were lower in infected chicks on day 15 post-infection (PI). Total leukocytes, heterophil and lymphocyte counts were higher in infected chicks on days 5 and 10 PI, while eosinophil counts were higher only on day 10 PI. Serum levels of total protein and globulins were higher in infected chicks on days 10 and 15 PI, while triglycerides and cholesterol levels were lower on day 15 PI. Acetylcholinesterase activity in total blood and butyrylcholinesterase activity in serum were higher in infected chicks on day 15 PI, while adenosine deaminase activity was higher on day 10 PI and lower on day 15 PI compared with the respective control. Finally, serum levels of reactive oxygen species and catalase activity in total blood were higher in infected chicks on day 15 PI, while superoxide dismutase activity in total blood was lower at the same time of infection. These data suggest that cholinergic and adenosinergic systems display a pro-inflammatory profile that contributes to impairment of immune and inflammatory responses in a mixed Eimeria infection. Furthermore, oxidative stress may contribute to clinical signs of disease as well as to pathogenesis. In summary, the impairment of immune response and alterations in blood antioxidant/oxidant status contributes to disease pathophysiology.

Gastrointestinal parasites in reindeer (Rangifer tarandus tarandus) calves from Fennoscandia: An epidemiological study

Reindeer (Rangifer tarandus tarandus) host numerous parasites. Although there is a general knowledge about parasite diversity in reindeer, detailed baseline information about parasitic infections is limited. Detailed knowledge of parasite prevalence and diversity provide a pathway for more targeted parasite control, an increasing need expected in the future. The main aim of our cross-sectional study was to estimate the prevalence of gastrointestinal parasites in semidomesticated reindeer calves. The 480 reindeer calves included in our study were aged 6-7 months, originated from 9 reindeer herding cooperatives in Finland and 1 in Norway, and were slaughtered during September-November 2015 in 10 reindeer slaughterhouses. All the reindeer calves passed meat inspection, and the detected parasitic infections were subclinical. As the reindeer included in this study were young animals intended for slaughter, they had never been administrated any antiparasitic treatment. Assessments of gastrointestinal parasitism among these reindeer calves were based on fecal examination and morphological identification of coccidian oocysts or helminth eggs. Individual fecal samples collected from the rectum of each of the reindeer were examined using a modified McMaster method. Most (78.3%) of the reindeer calves had eggs or oocysts of at least one parasite species in their feces, and more than half (53.5%) had a mixed infection. Strongylid eggs were detected in 75.6%, Eimeria sp. oocysts in 50.6%, Moniezia sp. eggs in 28.1%, Nematodirus sp. eggs in 22.1%, Capillaria sp. eggs in 9.4%, and Trichuris sp. eggs in 0.6% of the samples. The prevalence of gastrointestinal parasites was similar or higher relative to previous estimates from the region; the proportion of reindeer calves shedding strongylid eggs and the proportion of reindeer calves shedding Moniezia sp. eggs had increased. Prevalence varied by geographical region, which may reflect different herding practices or environmental parameters. Higher reindeer density was a risk factor for testing positive for Eimeria sp. oocysts, and the odds of testing positive for Nematodirus sp. eggs were higher if a peroral route was used for antiparasitic treatment in the reindeer herding cooperative. The mean proportion of reindeer estimated to receive antiparasitic treatment in Finland was 86% in 2004-2005 and 91% in 2014-2015. During the historical time frames of current management practices, this routine annual antiparasitic treatment of breeding reindeer has not decreased the prevalence of gastrointestinal parasites in reindeer calves, which can be seen as sentinels or indicators of the infection pressure.

Re-Evaluation of Asynchronous Asexual Development of Cystoisospora canis in Intestines of Dogs

The coccidian parasite Cystoisospora canis (syn. Isospora canis) can cause clinical disease in dogs. Three generation of schizonts have been reported in the small intestine of dogs before oocysts are excreted 9-11 days post inoculation (PI). Here, we re-evaluated asexual development of C. canis in 2 dogs necropsied 10 days after oral inoculation with 100,000 C. canis oocysts; both dogs had excreted oocysts 9 days PI. Asexual and sexual stages were seen in the lamina propria throughout the small intestine. Merozoites of different sizes were present, often in the same vacuole. They were arranged singly, in pairs, and many within a single parasitophorous vacuole. The maximum number of nuclei within developing merozoites in a group was 8, but it could not be discerned if they were individual nuclei or parts of merozoites. Findings of abundant asexual stages 1 day after dogs had started excreting oocysts indicated continued asexual multiplication beyond the prepatent period. The stages found resemble the 3 generations reported previously. The mode of division of the asexual generations remains unclear. The results of the present study indicate that there are many generations that are difficult to determine because of the multiplication of merozoites in the original host cell without leaving it to enter new host cells. From the literature, it is evident that cat and dog coccidia ( Cystoisospora spp.) divide by more than 1 type of division, including endodyogeny. In the past, the schizont/meront groups containing more than 1 generation have been called "cysts." However, cyst is not an accurate term because it is best used for an orally infective stage of coccidia; monozoic tissue cysts of C. canis can occur in paratenic hosts in extraintestinal organs. We recommend the term "types" as originally proposed for intestinal stages of Toxoplasma gondii and used for the original description of the life cycle of C. suis of swine when describing endogenous stages of the Sarcocystidae. Ultrastructural studies are needed to determine the precise form of multiplication of canine Cystoisospora species.

Purification of Cyclospora cayetanensis oocysts obtained from human stool specimens for whole genome sequencing

Background

Cyclospora cayetanensis is a food-borne intestinal human parasite that causes outbreaks of diarrhea. There is a need for efficient laboratory methods for strain-level characterization to assist in outbreak investigations. By using next generation sequencing, genomic sequences can be obtained and compared to identify potential genotyping markers. However, there is no method available to propagate this parasite in the laboratory. Therefore, genomic DNA must be extracted from oocysts purified from human stool. The objective of this study was to apply optimized methods to purify C. cayetanensis oocysts and extract DNA in order to obtain high-quality whole genome sequences with minimum contamination of DNA from other organisms.

Results

Oocysts from 21 human stool specimens were separated from other stool components using discontinuous density gradient centrifugation and purified further by flow cytometry. Genomic DNA was used to construct Ovation Ultralow libraries for Illumina sequencing. MiSeq sequencing reads were taxonomically profiled for contamination, de novo assembled, and mapped to a draft genome available in GenBank to assess the quality of the resulting genomic sequences. Following all purification steps, the majority (81-99%) of sequencing reads were from C. cayetanensis. They could be assembled into draft genomes of around 45 MB in length with GC-content of 52%.

Conclusions

Density gradients performed in the presence of a detergent followed by flow cytometry sorting of oocysts yielded sufficient genomic DNA largely free from contamination and suitable for whole genome sequencing of C. cayetanensis. The methods described here will facilitate the accumulation of genomic sequences from various samples, which is a prerequisite for the development of typing tools to aid in outbreak investigations.

Gametogony of Eimeria cameli in the small intestine of one-humped camel (Camelus dromedarius)

Domesticated Old World camels (Camelus dromedarius and Camelus bactrianus) are important for the economy of several countries in Asia, Africa, and the Arabian Peninsula, and coccidiosis is an important disease in camels. There is confusion concerning the species of coccidian parasites in camels and their life cycles. Although five species of Eimeria (E. cameli, E. rajasthani, E. dromedarii, E. bactriani, and E. pellerdyi) were named from camels, E. cameli is considered the most pathogenic. Here, development of gametogonic stages and oocysts of E. cameli are described in the lamina propria of the small intestines of naturally infected camels. Only sexual stages have been confirmed.

Discovery of new Toxoplasma gondii antigenic proteins using a high throughput protein microarray approach screening sera of murine model infected orally with oocysts and tissue cysts

Background

Toxoplasma gondii is an obligate intracellular protozoan parasite that causes congenital toxoplasmosis, as well as other serious clinical presentations in immune compromised humans. The parasite has also been recently linked to behavioral diseases in humans and other mammalian hosts. New antigens are being evaluated to develop a diagnostic kit for the diagnosis of acute infection or a protective vaccine.

Methods

In this study, we have focused on the discovery of new antigenic proteins from T. gondii genomic data using a high throughput protein microarray screening. To date, microarrays containing > 2870 candidate exon products of T. gondii have been probed with sera collected from patients with toxoplasmosis. Here, the protein microarrays are probed with well-characterized serum samples from animal models administered orally with oocysts or tissue cysts. The aim was to discover the antigens that overlap in the mouse profile with human antibody profiles published previously. For this, a reactive antigen list of 240 antigens recognized by murine IgG and IgM was identified using pooled sera from orally infected mice.

Results

Analyses of screening data have identified plenty of antigens and showed strong immunogenicity in both mouse and human antibody profiles. Among them, ROP1, GRA2, GRA3, GRA4, GRA5, GRA6, GRA7, GRA8, GRA14, MIC1, MIC2 and MAG1 have shown strong immunogenicity and used as antigen in development of vaccines or serological diagnostic assays in previous studies.

Conclusion

In addition to the above findings, ROP6, MIC12, SRS29A and SRS13 have shown strong immunogenicity but have not been tested in development of a diagnostic assay or a vaccine model yet.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2934-1) contains supplementary material, which is available to authorized users.

Molecular identification of Sarcocystis halieti n. sp., Sarcocystis lari and Sarcocystis truncata in the intestine of a white-tailed sea eagle (Haliaeetus albicilla) in Norway

An emaciated white-tailed sea eagle (Haliaeetus albicilla) from Western Norway was found and nursed briefly before it died. The necropsy revealed that the principal cause of death was an inflammation and occlusion of the bile ducts. A secondary finding was the presence in the intestinal mucosa of numerous sporulated Sarcocystis oocysts measuring 21.8-22.8 × 16.0-17.0 μm. The aim of this study was to identify these oocysts to species level using molecular methods. Genomic DNA was extracted from 10 mucosal scrapings containing oocysts and subjected to PCR amplification and sequencing of four DNA regions: the 18S and 28S rRNA genes, the ITS1 region and the cox1 gene. DNA of three previously known Sarcocystis spp. was identified, but only two of these, Sarcocystis halieti n. sp. and Sarcocystis lari, both employing sea birds as intermediate hosts, were considered to have used the sea eagle as a definitive host and to have formed oocysts in its intestine. The third species found, Sarcocystis truncata, employs red deer as intermediate hosts and seems to use felids as definitive hosts based on its phylogenetic position and prevalence. The sea eagle had probably recently ingested portions of one of the latter hosts (red deer or cat/lynx) containing stages (sarcocysts/oocysts) and thus DNA of S. truncata. The species S. halieti and S. lari could only be unambiguously separated from their most closely related congeners on the basis of their ITS1 sequences. This is the first report of Sarcocystis oocysts in sea eagles and the first identification to species level of Sarcocystis oocysts in any type of eagle. The sea eagle also acted as intermediate host of an unidentified Sarcocystis spp. as evidenced by the finding of six thin-walled sarcocysts in a histological section of cardiac muscle.

W A A V P guideline for evaluating the efficacy of anticoccidials in mammals (pigs, dogs, cattle, sheep)

This guideline is intended as an aid in the design, implementation and interpretation of studies for the assessment of drug efficacy against Eimeria in cattle and sheep, Cystoisospora in pigs and dogs, and Cryptosporidium in cattle. It deals with the most important aspects of how to conduct both experimental and field studies for dose determination, dose confirmation and assessment of field effectiveness. Also, guidance on the selection of animals, diagnostic techniques, statistical evaluation and methods for the preparation, maintenance and use of parasites is provided. The specific management conditions that may influence the course of natural infections and consequently determine treatment schemes are mentioned and suggestions for best practice in sampling and evaluation of data prior to conducting of efficacy studies are given. The guideline is also intended to assist investigators in carrying out specific studies, provide relevant information for registration authorities involved in the decision-making process, assist in the approval of anticoccidial drugs in the target species, and facilitate the world-wide adoption of standard procedures. Although currently not implemented, issues of drug resistance testing and alternative methods for drug testing are also discussed as future issues in drug testing against mammalian coccidia.

Dynamics of Plasmodium vivax sporogony in wild Anopheles stephensi in a malaria-endemic region of Western India

Background

In global efforts to track mosquito infectivity and parasite elimination, controlled mosquito-feeding experiments can help in understanding the dynamics of parasite development in vectors. Anopheles stephensi is often accepted as the major urban malaria vector that transmits Plasmodium in Goa and elsewhere in South Asia. However, much needs to be learned about the interactions of Plasmodium vivax with An. stephensi. As a component of the US NIH International Center of Excellence for Malaria Research (ICEMR) for Malaria Evolution in South Asia (MESA), a series of membrane-feeding experiments with wild An. stephensi and P. vivax were carried out to better understand this vector-parasite interaction.

Methods

Wild An. stephensi larvae and pupae were collected from curing water in construction sites in the city of Ponda, Goa, India. The larvae and pupae were reared at the MESA ICEMR insectary within the National Institute of Malaria Research (NIMR) field unit in Goa until they emerged into adult mosquitoes. Blood for membrane-feeding experiments was obtained from malaria patients at the local Goa Medical College and Hospital who volunteered for the study. Parasites were counted by Miller reticule technique and correlation between gametocytaemia/parasitaemia and successful mosquito infection was studied.

Results

A weak but significant correlation was found between patient blood gametocytaemia/parasitaemia and mosquito oocyst load. No correlation was observed between gametocytaemia/parasitaemia and oocyst infection rates, and between gametocyte sex ratio and oocyst load. When it came to development of the parasite in the mosquito, a strong positive correlation was observed between oocyst midgut levels and sporozoite infection rates, and between oocyst levels and salivary gland sporozoite loads. Kinetic studies showed that sporozoites appeared in the salivary gland as early as day 7, post-infection.

Conclusions

This is the first study in India to carry out membrane-feeding experiments with wild An. stephensi and P. vivax. A wide range of mosquito infection loads and infection rates were observed, pointing to a strong interplay between parasite, vector and human factors. Most of the present observations are in agreement with feeding experiments conducted with P. vivax elsewhere in the world.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1931-8) contains supplementary material, which is available to authorized users.

Recombinase polymerase amplification (RPA) combined with lateral flow (LF) strip for detection of Toxoplasma gondii in the environment

Toxoplasma gondii infects all warm-blooded vertebrates, resulting in a great threat to human health and significant economic loss to the livestock industry. Ingestion of infectious oocysts of T. gondii from the environment is the major source of transmission. Detection of T. gondii oocysts by existing methods is laborious, time-consuming and expensive. The objective of the present study was to develop a recombinase polymerase amplification (RPA) method combined with a lateral flow (LF) strip for detection of T. gondii oocysts in the soil and water. The DNA of T. gondii oocysts was amplified by a pair of specific primers based on the T. gondii B1 gene over 15min at a constant temperature ranging from 30°C to 45°C using RPA. The amplification product was visualized by the lateral flow (LF) strip within 5min using the specific probe added to the RPA reaction system. The sensitivity of the established assay was 10 times higher than that of nested PCR with a lower detection limit of 0.1 oocyst per reaction, and there was no cross-reactivity with other closely related protozoan species. Fifty environmental samples were further assessed for the detection validity of the LF-RPA assay (B1-LF-RPA) and compared with nested PCR based on the B1 gene sequence. The B1-LF-RPA and nested PCR both showed that 5 out of the 50 environmental samples were positive. The B1-LF-RPA method was also proven to be sufficiently tolerant of existing inhibitors in the environment. In addition, the advantages of simple operation, speediness and cost-effectiveness make B1-LF-RPA a promising molecular detection tool for T. gondii.

Schizogony and gametogony of oocyst-deficient T-263 strain of Toxoplasma gondii

Oocysts are important stage for the spread of Toxoplasma gondii because they are environmentally resistant. Among all hosts of T. gondii, only felids can excrete oocysts. Cats that have excreted T. gondii oocysts after primary infection develop immunity to re-excretion of oocysts, and this immunity appears to be long-lasting. It would be desirable to have a non-infectious vaccine for the prevention of T. gondii infection in cats and to understand mechanism of immunity to excretion of oocysts. An initial step will be to indentify stage/stages of the parasite for induction of immunity. A chemically-induced mutant of T. gondii, T-263, is immunogenic but lacks the capacity to form oocysts in cats. Cats fed live bradyzoites of T-263 do not excrete oocysts after challenge with oocyst producing strains. However, it is not known at what stage of the parasite development the oocyst formation is halted. Here, four cats were fed live tissue cysts of the T-263 strain and examined for enteroepithelial stages and oocyst production. Two cats were administered methyl prednisolone aceatate (20mg/kg) once intramuscularly and these cats were euthanized 5 and 7days post inoculation. No oocysts but immature and mature schizonts (types D and E), male, and female gamonts were detected in two cats euthanized. The remaining two cats did not excrete oocysts examined 3-14days post inoculation, but both seroconverted and developed antibody titers of 1:400 tested by the modification agglutination test, indicating exposure to the inocula. The results demonstrate that the T-263 strain is defective in oocyst formation and the observations should help future studies in identification of genes/factors responsible for oocyst formation in the intestine of cats.

Bioaccumulation of Toxoplasma and Cryptosporidium by the freshwater crustacean Gammarus fossarum: Involvement in biomonitoring surveys and trophic transfer

The protozoa Toxoplasma gondii and Cryptosporidium parvum are public health priorities because their oocysts can persist in recreational, surface, drinking, river, and sea water sources for a long time. To evaluate the capacity of the freshwater crustacean Gammarus fossarum to accumulate T. gondii and C. parvum oocysts, gammarids were exposed to 200, 2000 or 20,000 oocysts per gammarid and per day for 21 days followed by 5 days of depuration. C. parvum DNA was detected by qPCR in G. fossarum in only one out of four pools for the highest concentration and after 14 days of exposure, and T. gondii DNA was detected after 7 days of exposure to the two highest concentrations. Our results document the capacity of G. fossarum to accumulate T. gondii in its tissues proportionally to the ambient concentration; the maximum number of oocysts was detected in gammarid tissues after exposure to 20,000 oocysts per day. Mean values of 3.26 (±3), 21.71 (±15.18), and 17.41 (±10.89) oocysts were detected in gammarids after 7, 14, and 21 days, respectively, and after 5 days of depuration, T. gondii oocysts were still present in gammarid tissues. These results show for the first time that a freshwater crustacean can bioaccumulate T. gondii oocysts, suggesting that G. fossarum is a potential effective bioindicator of protozoan contamination in biomonitoring studies. Moreover, due to its key position in freshwater food webs, G. fossarum could also play a role in the trophic transfer of protozoa.