Detection and quantification of Toxoplasma gondii in ovine maternal and foetal tissues from experimentally infected pregnant ewes using real-time PCR

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.

Investigation of Toxoplasma gondii and Neospora caninum as cause of ovine abortion in affected flocks of Urmia, northwest of Iran

Toxoplasma gondii and Neospora caninum, two obligatory intracellular protozoan parasites, are important causes of neonatal mortality and abortion in farmed ruminants worldwide. Previously, protozoan abortions in small ruminants were attributed to T. gondii, but the role of N. caninum in these abortions was uncertain. The aim of this study was to investigate the role of T. gondii and N. caninum in ovine abortion in Urmia, northwest of Iran using a molecular method. Overall, 130 placenta and brain samples of aborted ovine foetuses were collected. Extracted DNA from placenta and CNS tissues of the aborted foetuses were analysed using PCR with primers specific for T. gondii and N. cani­num. The association of the frequency of T. gondii and N. caninum infection of aborted foetuses with age and breed in flocks was also studied. The results showed that out of the 130 examined ovine foetuses, 5.3 and 2.3 % were PCR-positive for T. gondii and N. caninum DNA, respectively. In this study, no significant differences were recorded relating to Toxoplasma and Neospora infection in different age groups in flocks and among sheep breeds included in the present study (P>0.05). The results of this study proved the importance of T. gondii and N. caninum as reasons of abortion in the studied area.

Characterization and evaluation of a recombinant multiepitope peptide antigen MAG in the serological diagnosis of Toxoplasma gondii infection in pigs

Background

Toxoplasmosis caused by Toxoplasma gondii is a serious disease threatening human and animal health. People can be infected with T. gondii by ingesting raw pork contaminated with cysts or oocysts. Serological test is a sensitive and specific method usually used for large-scale diagnosis of T. gondii infection in humans and animals (such as pigs). Commercial pig Toxoplasma antibody ELISA diagnostic kits are expensive, which limits their use; moreover, the wide antigen composition used in these diagnostic kits is still unclear and difficult to standardize. The multiepitope peptide antigen is a novel diagnostic marker, and it has potential to be developed into more accurate and inexpensive diagnostic kits.

Methods

The synthetic multiepitope antigen (MAG) cDNA encoding a protein with epitopes from five T. gondii-dominant antigens (SAG1, GRA1, ROP2, GRA4, and MIC3) was designed, synthesized, and expressed in Escherichia coli BL21 (DE3) strain. The recombinant protein was detected through western blot with pig anti-T. gondii-positive and -negative serum, and then IgG enzyme-linked immunosorbent assay (ELISA) named MAG-ELISA was designed. The MAG-ELISA was evaluated in terms of specificity, sensitivity, and stability. The MAG-ELISA was also compared with a commercial PrioCHECK^®Toxoplasma Ab porcine ELISA (PrioCHECK ELISA). Finally, the trend of pig anti-T. gondii IgG levels after artificial infection with RH tachyzoites was evaluated using MAG-ELISA and two other ELISA methods (rMIC3-ELISA and PrioCHECK ELISA).

Results

MAG antigen could be specifically recognized by pig anti-T. gondii-positive but not -negative serum. MAG-ELISA showed high diagnostic performance in terms of specificity (88.6%) and sensitivity (79.1%). MAG-ELISA could be used for detecting anti-T. gondii IgG in the early stage of T. gondii infection in pigs (at least 7 days after artificial infection).

Conclusions

Our results suggest that MAG antigen can be applied to specifically recognize anti-T. gondii IgG in pig, and MAG-ELISA has the potential for large-scale screening tests of T. gondii infection in pig farms and intensive industries.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04917-w.

Molecular characterization of Toxoplasma gondii isolates from free-range chickens reveals new genotypes in Goiânia, Goiás, Brazil

The aim of this study was to evaluate the genotypic characteristics of Toxoplasma gondii isolated from free-range chickens in the metropolitan area of Goiânia, Goiás, in Brazil's central-west region. The seroprevalence rate was found to be 96%, according to an indirect hemagglutination assay. Brain and heart samples were processed by peptic digestion for a mice bioassay. The tissues were homogenized and the resulting samples were subjected to polymerase chain reaction (PCR), which revealed that 64% of them contained the parasite's DNA. The mice bioassay revealed 15 isolates, 8 of them tachyzoites isolates from the peritoneal lavage and 7 from brain cysts. T. gondii genotypes were determined through PCR-RFLP, using the following markers: SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, alt. SAG2, Apico and CS3. Three genotypes were identified, inclued ToxoDB #65, and the other two are not yet described in the literature. Hence, we conclude that the isolates obtained from the metropolitan area of Goiânia showed relatively low genetic diversity.

Clams and potential foodborne Toxoplasma gondii in Nunavut, Canada

The prevalence of Toxoplasma gondii exposure in Inuit living in Nunavut (20%) is twice that of the US (11%); however, routes of exposure for Inuit communities in North America are unclear. Exposure to T. gondii in humans has been linked with consumption of raw or undercooked shellfish that can accumulate environmentally resistant oocysts. Bivalve shellfish, such as clams, are an important, nutritious, affordable and accessible source of food in many Northern Communities. To date, presence of T. gondii in clams in Northern Canada has not been reported. In this study, we tested for T. gondii presence in clams (Mya truncata) that were harvested in Iqaluit, Nunavut over a 1-week period in September 2016. Of 390 clams, eight (2.1%) were confirmed to contain T. gondii DNA (≥99.7% identity), as determined using polymerase chain reaction (PCR) and sequence confirmation. Additionally, three clams (0.8%) were confirmed to contain Neospora caninum-like DNA (≥99.2% identity). While N. caninum is not known to be a zoonotic pathogen, its presence in shellfish indicates contamination of the nearshore with canid faeces, and the potential for marine mammal exposure through marine food webs. Notably, the PCR assay employed in this study does not discriminate between viable and non-viable parasites. These findings suggest a possible route for parasite exposure through shellfish in Iqaluit, Nunavut. Future research employing viability testing will further inform public health messaging on the infectious potential of T. gondii in shellfish.

Toxoplasmosis: Recent Advances in Understanding the Link Between Infection and Host Behavior

Humans, wildlife, and domestic animals are intimately linked through shared infections. Many parasites and pathogens use multiple host species, either opportunistically or sequentially, such that managing disease risk frequently requires a broader understanding of the ecological community. The coccidian protozoan Toxoplasma gondii infects more than one hundred species of vertebrates, ranging from bats to beluga whales. In humans, acute toxoplasmosis can have serious health consequences for immunocompromised individuals. Even amongst asymptomatic patients, however, toxoplasmosis has been linked to a range of behavioral alterations and conditions, such as changes in risk tolerance, neuroticism, mental illness, suicide, and accident proneness. Whether such links are causal or simply correlational has been the subject of intense study and debate; from an evolutionary standpoint, selection may favor parasite-induced alterations in host behavior that increase the likelihood a host is consumed by the definitive host-in this case a domestic or wild felid. Here, we examine current evidence for parasite-induced manipulations of host behavior, in both humans and other animals. We critically evaluate proposed mechanisms through which infection might influence host behavior, which range from inflammation in the brain to changes in hormones or neurotransmitters. Considering estimates that T. gondii may infect up to one-third of the global human population, we conclude by examining the implications of these changes for human behavior, individual fitness, and emergent cultural properties.

Comparative aspects of laboratory testing for the detection of Toxoplasma gondii and its differentiation from Neospora caninum as the etiologic agent of ovine abortion

Histologic examination of aborted material is an essential component in the diagnosis of ovine toxoplasmosis. However, the detection of Toxoplasma gondii in histologic sections, and its differentiation from the closely related protozoan Neospora caninum, is challenging. We developed a chromogenic in situ hybridization (ISH) assay for the identification of T. gondii in paraffin-embedded tissue samples. We examined retrospectively the archived placental tissue of 200 sheep abortion submissions for the presence of T. gondii by immunohistochemistry (IHC), ISH, and real-time PCR (rtPCR). All placental samples that tested positive for T. gondii by rtPCR (9 of 200) were also positive by IHC, with inconclusive IHC staining in an additional 7 rtPCR-negative cases. Further testing for N. caninum of all 200 placentas by rtPCR revealed 7 Neospora-positive cases. T. gondii ISH was positive in 4 of 9 IHC-positive samples and 1 of the 7 N. caninum rtPCR-positive samples. Real-time PCR was used as the reference standard for specificity and sensitivity calculations regarding placenta samples. Specificity of ISH and IHC was 99% and 96-100%, respectively. The sensitivity of ISH (44%) was quite low compared to IHC (100%). The exclusive use of ISH for the detection of T. gondii, and thus for the diagnosis of ovine toxoplasmosis, was not acceptable. However, combined with rtPCR, both ISH and IHC can be useful detection methods to improve histologic evaluation by visualizing the parasite within tissue sections.

Economic and public health importance of Toxoplasma gondii infections in sheep: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, control, and genetic diversity of T. gondii in sheep in the past decade. There is debate and uncertainty concerning repeat congenital infection as evidenced by finding T. gondii DNA in progeny of chronically infected sheep. However, there is no concrete evidence that T. gondii is the cause of repeated abortions in sheep. Recent data concerning pathogenesis of abortion in acutely infected sheep are reviewed. PCR-RFLP typing of T. gondii DNA derived from viable T. gondii isolates or tissues of infected sheep revealed low genetic diversity in sheep in Europe, Africa, Asia and North America but high diversity in South America. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Treatment with Bumped Kinase Inhibitor 1294 Is Safe and Leads to Significant Protection against Abortion and Vertical Transmission in Sheep Experimentally Infected with Toxoplasma gondii during Pregnancy

Previous studies on drug efficacy showed low protection against abortion and vertical transmission of Toxoplasma gondii in pregnant sheep. Bumped kinase inhibitors (BKIs), which are ATP-competitive inhibitors of calcium-dependent protein kinase 1 (CDPK1), were shown to be highly efficacious against several apicomplexan parasites in vitro and in laboratory animal models. Here, we present the safety and efficacy of BKI-1294 treatment (dosed orally at 100 mg/kg of body weight 5 times every 48 h) initiated 48 h after oral infection of sheep at midpregnancy with 1,000 TgShSp1 oocysts. BKI-1294 demonstrated systemic exposure in pregnant ewes, with maximum plasma concentrations of 2 to 3 μM and trough concentrations of 0.4 μM at 48 h after each dose. Oral administration of BKI-1294 in uninfected sheep at midpregnancy was deemed safe, since there were no changes in behavior, fecal consistency, rectal temperatures, hematological and biochemical parameters, or fetal mortality/morbidity. In ewes infected with a T. gondii oocyst dose lethal for fetuses, BKI-1294 treatment led to a minor rectal temperature increase after infection and a decrease in fetal/lamb mortality of 71%. None of the lambs born alive in the treated group exhibited congenital encephalitis lesions, and vertical transmission was prevented in 53% of them. BKI-1294 treatment during infection led to strong interferon gamma production after cell stimulation in vitro and a low humoral immune response to soluble tachyzoite antigens but high levels of anti-SAG1 antibodies. The results demonstrate a proof of concept for the therapeutic use of BKI-1294 to protect ovine fetuses from T. gondii infection during pregnancy.

Toxoplasma gondii infection and toxoplasmosis in farm animals: Risk factors and economic impact

The protozoan parasite Toxoplasma gondii is a zoonotic parasite that can be transmitted from animals to humans. Felids, including domestic cats, are definitive hosts that can shed oocysts with their feces. In addition to infections that occur by accidental oral uptake of food or water contaminated with oocysts, it is assumed that a large proportion of affected humans may have become infected by consuming meat or other animal products that contained infective parasitic stages of T. gondii. Since farm animals represent a direct source of infection for humans, but also a possible reservoir for the parasite, it is important to control T. gondii infections in livestock. Moreover, T. gondii may also be pathogenic to livestock where it could be responsible for considerable economic losses in some regions and particular farming systems, e.g. in areas where the small ruminant industry is relevant. This review aims to summarize actual knowledge on the prevalence and effects of infections with T. gondii in the most important livestock species and on the effects of toxoplasmosis on livestock. It also provides an overview on potential risk factors favoring infections of livestock with T. gondii. Knowledge on potential risk factors is prerequisite to implement effective biosecurity measures on farms to prevent T. gondii infections. Risk factors identified by many studies are cat-related, but also those associated with a potential contamination of fodder or water, and with access to a potentially contaminated environment. Published information on the costs T. gondii infections cause in livestock production, is scarce. The most recent peer reviewed reports from Great Britain and Uruguay suggest annual cost of about 5-15 million US $ per country. Since these estimates are outdated, future studies are needed to estimate the present costs due to toxoplasmosis in livestock. Further, the fact that T. gondii infections in livestock may affect human health needs to be considered and the respective costs should also be estimated, but this is beyond the scope of this article.

Comparison of freeze-thaw cycles for nucleic acid extraction and molecular detection of Cryptosporidium parvum and Toxoplasma gondii oocysts in environmental matrices

Freeze-thaw DNA extraction methods and PCR primers were compared to optimize detection of Cryptosporidium parvum and Toxoplasma gondii oocysts in different matrices. Increasing FT cycles did not increase parasite DNA detection, and primers targeting the 18S ssrRNA gene yielded the most sensitive detection of C. parvum oocysts.

Advances in serological, imaging techniques and molecular diagnosis of Toxoplasma gondii infection

BACKGROUND

Toxoplasmosis is worldwide distributed zoonotic infection disease with medical importance in immunocompromised patients, pregnant women and congenitally infected newborns. Having basic information on the traditional and new developed methods is essential for general physicians and infectious disease specialists for choosing a suitable diagnostic approach for rapid and accurate diagnosis of the disease and, consequently, timely and effective treatment.

METHODS

We conducted English literature searches in PubMed from 1989 to 2016 using relevant keywords and summarized the recent advances in diagnosis of toxoplasmosis.

RESULTS

Enzyme-linked immunosorbent assay (ELISA) was most used method in past century. Recently advanced ELISA-based methods including chemiluminescence assays (CLIA), enzyme-linked fluorescence assay (ELFA), immunochromatographic test (ICT), serum IgG avidity test and immunosorbent agglutination assays (ISAGA) have shown high sensitivity and specificity. Recent studies using recombinant or chimeric antigens and multiepitope peptides method demonstrated very promising results to development of new strategies capable of discriminating recently acquired infections from chronic infection. Real-time PCR and loop-mediated isothermal amplification (LAMP) are two recently developed PCR-based methods with high sensitivity and specificity and could be useful to early diagnosis of infection. Computed tomography, magnetic resonance imaging, nuclear imaging and ultrasonography could be useful, although their results might be not specific alone.

CONCLUSION

This review provides a summary of recent developed methods and also attempts to improve their sensitivity for diagnosis of toxoplasmosis. Serology, molecular and imaging technologies each has their own advantages and limitations which can certainly achieve definitive diagnosis of toxoplasmosis by combining these diagnostic techniques.

Experimental ovine toxoplasmosis: influence of the gestational stage on the clinical course, lesion development and parasite distribution

The relation between gestational age and foetal death risk in ovine toxoplasmosis is already known, but the mechanisms involved are not yet clear. In order to study how the stage of gestation influences these mechanisms, pregnant sheep of the same age and genetic background were orally dosed with 50 oocysts of Toxoplasma gondii (M4 isolate) at days 40 (G1), 90 (G2) and 120 (G3) of gestation. In each group, four animals were culled on the second, third and fourth week post infection (pi) in order to evaluate parasite load and distribution, and lesions in target organs. Ewes from G1 showed a longer period of hyperthermia than the other groups. Abortions occurred in all groups. While in G2 they were more frequent during the acute phase of the disease, in G3 they mainly occurred after day 20 pi. After challenge, parasite and lesions in the placentas and foetuses were detected from day 19 pi in G3 while in G2 or G1 they were only detected at day 26 pi. However, after initial detection at day 19 pi, parasite burden, measured through RT-PCR, in placenta or foetus of G3 did not increase significantly and, at in the third week pi it was lower than that measured in foetal liver or placenta from G1 to G3 respectively. These results show that the period of gestation clearly influences the parasite multiplication and development of lesions in the placenta and foetus and, as a consequence, the clinical course in ovine toxoplasmosis.

Parasite distribution and associated immune response during the acute phase of Toxoplasma gondii infection in sheep

BACKGROUND

In many countries, Toxoplasma gondii (T. gondii) is a major cause of reproductive disorders and abortions in the sheep industry, and therefore responsible for important financial and economic losses. In addition, undercooked infected lamb is an important risk factor for human toxoplasmosis. In the present study, the initial phase of the infection was investigated: the parasite's entry site, the subsequent distribution of the parasite and the host-immune response.

RESULTS

Parasite DNA was already detected in the cranial small intestinal mucosa the first days after oral infection with T. gondii tissue cysts. Simultaneously, high IFN-gamma and IL-12 responses were induced mainly in the mesenteric lymph nodes. The emergence of IgG1 (at 8dpi), and IgG2 (at 11 dpi) was accompanied by a decrease or even disappearance of the IFN-gamma and IL-12 response in the Peyers' patches (PP), PBMC's and popliteal LN's. Meanwhile the parasite DNA could be recovered from most mucosal and systemic tissues to become undetectable in the small intestine, popliteal LN, PBMC and spleen 3 weeks pi.

CONCLUSIONS

Our results indicate that parasites enter the cranial small intestine the first days after infection and that after an increase the first two weeks after infection, the parasite DNA levels in the intestine drop below the detection limit three weeks after infection. This coincides with an increase in parastic-specific serum IgG1 and IgG2 and a decrease of the antigen-specific IFN-gamma response in PP, PBMC and popliteal LN. We suggest a role for IFN-gamma and IL-12 in controlling the infection.

Toxoplasma gondii infection enhances the kairomonal valence of rat urine

Many animals use chemicals as pheromones to communicate between individuals of the same species, for example to influence mate choice or to assert dominance. Pheromonal communication is an open broadcast system that can be intercepted by unintended receivers such as predators and prey. We have recently reported that male rats infected by the protozoan parasite Toxoplasma gondii become more attractive to female rats. This suggests a facilitatory effect of infection on rat pheromone production. In view of the open nature of pheromonal communication, we postulate that Toxoplasma gondii infection collateraly enhances kairomonal valence of infected rats to their prey. We compared the strength of kairomonal interception by mice when using scent marks from rats infected with Toxoplasma gondii vs. marks from uninfected control rats. Mice exhibited greater avoidance to both fresh urine and aged rat urine marks obtained from infected animals. These results indicate that, at least in some cases, parasitism can result in opportunity costs for hosts by making prey species more averse to them.

Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep

After oral administration of ewes during mid gestation with 2000 freshly prepared sporulated oocysts of T. gondii isolate M4, abortions occurred between days 7 and 11 in 91.6% of pregnant and infected ewes. Afterwards, a further infection was carried out at late gestation in another group of sheep with 500 sporulated oocysts. Abortions happened again between days 9 and 11 post infection (pi) in 58.3% of the infected ewes. Classically, abortions in natural and experimental ovine toxoplasmosis usually occur one month after infection. Few experimental studies have reported the so-called acute phase abortions as early as 7 to 14 days after oral inoculation of oocysts, and pyrexia was proposed to be responsible for abortion, although the underline mechanism was not elucidated. In the present study, all placentas analysed from ewes suffering acute phase abortions showed infarcts and thrombosis in the caruncullar villi of the placentomes and ischemic lesions (periventricular leukomalacia) in the brain of some foetuses. The parasite was identified by PCR in samples from some placentomes of only one sheep, and no antigen was detected by immunohistochemical labelling. These findings suggest that the vascular lesions found in the placenta, and the consequent hypoxic damage to the foetus, could be associated to the occurrence of acute phase abortions. Although the pathogenesis of these lesions remains to be determined, the infectious dose or virulence of the isolate may play a role in their development.

Application of quantitative real-time polymerase chain reaction for the diagnosis of toxoplasmosis and enzootic abortion of ewes

Toxoplasma gondii and Chlamydophila abortus are the 2 most common infectious causes of ovine abortion worldwide. These obligate intracellular pathogens are associated with severe placentitis leading to abortion or stillbirth in pregnant ewes, and resulting in significant economic losses. The objectives of the current study were the development, validation, and application of a duplex real-time polymerase chain reaction (PCR) assay capable of quantifying the burden of infection by T. gondii and C. abortus in material submitted for diagnostic purposes. The validation was carried out using samples from ewes experimentally infected with these organisms. Based on the numbers of genome copies detected, an arbitrary cutoff level was established to correlate with significant pathological changes sufficient to give rise to abortion. When the PCR assay was applied to samples from 66 Irish farms with naturally occurring outbreaks of ovine abortion, toxoplasmosis and enzootic abortion of ewes (EAE) accounted for 14% and 20% of the farms, respectively, while on 6% of the farms, there was evidence of dual infection. When standard diagnostic techniques including histopathological examination, serological analysis, chlamydial antigen detection, and bacteriological culture, were used on samples from the same farms, toxoplasmosis was diagnosed in 17% of farms, and EAE in 12%; dual infection was diagnosed on 3% of the farms. In general, good agreement was found between the PCR and the standard methods. The duplex real-time PCR assay developed in this study has proved to be a very sensitive and rapid tool that might provide a valuable addition to the methods currently available for routine diagnosis of ovine abortions.

Advances in diagnosis of protozoan diseases

Microscopy still remains the gold standard procedure for the diagnosis of many protozoan infections in animals, but the specific identification requires skilled and experienced personnel. Immunoassays, detecting antibodies or specific protozoan antigens, have been developed but often lack sensitivity and specificity due to close relationship between many protozoa. Recent research has focussed almost exclusively on molecular based techniques for the identification and quantification of parasite DNA in samples. Opinion differ on most appropriate targets to use and there are very few diagnostic kits available making comparison between laboratories difficult. Future research needs to focus on robust, cheap field diagnostic assays.

Protozoan parasite Toxoplasma gondii manipulates mate choice in rats by enhancing attractiveness of males

Females in various species typically avoid males infected with parasites, while parasite-free males advertise their status through conspicuous phenotypic traits. This process selects for heritable resistance and reduces direct exposure of the female to parasites. Coevolving parasites are likely to attempt to circumvent this obstacle. In this paper, we demonstrate a case of parasitic manipulation of host mate choice. We report that Toxoplasma gondii, a sexually transmitted infection of brown rats, enhances sexual attractiveness of infected males. Thus under some evolutionary niches, parasites can indeed manipulate host sexual signaling to their own advantage.

Identification of tissue cyst wall components by transcriptome analysis of in vivo and in vitro Toxoplasma gondii bradyzoites

The Toxoplasma gondii bradyzoite is essential to establish persistent infection, yet little is known about what factors this developmental form secretes to establish the cyst or interact with its host cell. To identify candidate bradyzoite-secreted effectors, the transcriptomes of in vitro tachyzoites 2 days postinfection, in vitro bradyzoites 4 days postinfection, and in vivo bradyzoites 21 days postinfection were interrogated by microarray, and the program SignalP was used to identify signal peptides indicating secretion. One hundred two putative bradyzoite-secreted effectors were identified by this approach. Two candidates, bradyzoite pseudokinase 1 and microneme adhesive repeat domain-containing protein 4, were chosen for further investigation and confirmed to be induced and secreted by bradyzoites in vitro and in vivo. Thus, we report the first analysis of the transcriptomes of in vitro and in vivo bradyzoites and identify two new protein components of the Toxoplasma tissue cyst wall.

Methods to produce and safely work with large numbers of Toxoplasma gondii oocysts and bradyzoite cysts

Two major obstacles to conducting studies with Toxoplasma gondii oocysts are the difficulty in reliably producing large numbers of this life stage and safety concerns because the oocyst is the most environmentally resistant stage of this zoonotic organism. Oocyst production requires oral infection of the definitive feline host with adequate numbers of T. gondii organisms to obtain unsporulated oocysts that are shed in the feces for 3-10 days after infection. Since the most successful and common mode of experimental infection of kittens with T. gondii is by ingestion of bradyzoite tissue cysts, the first step in successful oocyst production is to ensure a high bradyzoite tissue cyst burden in the brains of mice that can be used for the oral inoculum. We compared two methods for producing bradyzoite brain cysts in mice, by infecting them either orally or subcutaneously with oocysts. In both cases, oocysts derived from a low passage T. gondii Type II strain (M4) were used to infect eight-ten week-old Swiss Webster mice. First the number of bradyzoite cysts that were purified from infected mouse brains was compared. Then to evaluate the effect of the route of oocyst inoculation on tissue cyst distribution in mice, a second group of mice was infected with oocysts by one of each route and tissues were examined by histology. In separate experiments, brains from infected mice were used to infect kittens for oocyst production. Greater than 1.3 billion oocysts were isolated from the feces of two infected kittens in the first production and greater than 1.8 billion oocysts from three kittens in the second production. Our results demonstrate that oral delivery of oocysts to mice results in both higher cyst loads in the brain and greater cyst burdens in other tissues examined as compared to those of mice that received the same number of oocysts subcutaneously. The ultimate goal in producing large numbers of oocysts in kittens is to generate adequate amounts of starting material for oocyst studies. Given the potential risks of working with live oocysts in the laboratory, we also tested a method of oocyst inactivation by freeze-thaw treatment. This procedure proved to completely inactivate oocysts without evidence of significant alteration of the oocyst molecular integrity.

Distribution of Lesions in Fetal Brains Following Experimental Infection of Pregnant Sheep With Toxoplasma gondii

Six ovine fetal brains were harvested 33 to 35 days postchallenge from 5 ewes, each of which was given 3000 Toxoplasma gondii oocysts on day 90 of pregnancy. Histopathologic examination of transverse sections taken at 13 levels in the fetal brains revealed the presence of toxoplasmosis-related lesions in all 6 brains. However, lesions were not randomly distributed ( P = .007); they were most numerous at the level of the optic tract, the rostral margin of the pons, and 4 mm caudal to the ansate sulcus and were absent in all sections at the level of the caudal cerebellum. Lesion distribution may be due to hemodynamic factors, differences in the expression of endothelial surface receptor molecules at the level of the blood-brain barrier, or the presence of localized permissive/inhibitory factors within the brain. The results have implications for the selection of areas of brain from aborted ovine fetuses to be examined histopathologically for laboratory diagnosis.

Molecular diagnosis of infections and resistance in veterinary and human parasites

Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.

Study on ovine abortion associated withToxoplasma gondiiin affected herds of Khorasan Razavi Province, Iran based on PCR detection of fetal brains and maternal serology

Toxoplasma gondii, an obligatory intracellular protozoan parasite, is one of the causative agents of ovine abortion, as reported in many countries. Different techniques are being used to detect this pathogen in infected ovine fetuses. One of the most sensitive and specific diagnostic techniques is Nested-PCR amplification of the B1 target gene of the organism. In total, 200 brain samples of aborted ovine fetuses and maternal sera submitted from different parts of Khorasan Razavi province, Iran were investigated to track the role ofToxoplasma gondiiin ovine abortion by a slightly modified Nested-PCR and IFAT assays, respectively. Among all samples, 27 (13·5%) were PCR-positive and 31 (15·5%) were IFAT-positive and theToxoplasma-induced abortion prevalence calculated was 8·8% to18·2% with 95% confidence interval. Results show that high levels of congenital transmission may occur in 27/31(87%) of pregnancies with an excellent logical agreement (ĸ=0·9) between 2 different tests. According to the results of this study, the Nested-PCR employed in this investigation could be recommended as an applied routine test for the routine examination and confirmation ofToxoplasma gondii-induced ovine abortion.