Sporogony and experimental transmission of Babesia equi by Boophilus microplus

Differential nested patterns of Anaplasma marginale and Coxiella-like endosymbiont across Rhipicephalus microplus ontogeny

Understanding the intricate ecological interactions within the microbiome of arthropod vectors is crucial for elucidating disease transmission dynamics and developing effective control strategies. In this study, we investigated the ecological roles of Coxiella-like endosymbiont (CLE) and Anaplasma marginale across larval, nymphal, and adult stages of Rhipicephalus microplus. We hypothesized that CLE would show a stable, nested pattern reflecting co-evolution with the tick host, while A. marginale would exhibit a more dynamic, non-nested pattern influenced by environmental factors and host immune responses. Our findings revealed a stable, nested pattern characteristic of co-evolutionary mutualism for CLE, occurring in all developmental stages of the tick. Conversely, A. marginale exhibited variable occurrence but exerted significant influence on microbial community structure, challenging our initial hypotheses of its non-nested dynamics. Furthermore, in silico removal of both microbes from the co-occurrence networks altered network topology, underscoring their central roles in the R. microplus microbiome. Notably, competitive interactions between CLE and A. marginale were observed in nymphal network, potentially reflecting the impact of CLE on the pathogen transstadial-transmission. These findings shed light on the complex ecological dynamics within tick microbiomes and have implications for disease management strategies.

Apicomplexa micropore: history, function, and formation

The micropore, a mysterious structure found in apicomplexan species, was recently shown to be essential for nutrient acquisition in Plasmodium falciparum and Toxoplasma gondii. However, the differences between the micropores of these two parasites questions the nature of a general apicomplexan micropore structure and whether the formation process model from Plasmodium can be applied to other apicomplexans. We analyzed the literature on different apicomplexan micropores and found that T. gondii probably harbors a more representative micropore type than the more widely studied ones in Plasmodium. Using recent knowledge of the Kelch 13 (K13) protein interactome and gene depletion phenotypes in the T. gondii micropore, we propose a model of micropore formation, thus enriching our wider understanding of micropore protein function.

Differential Expression of Immune Genes in the Rhipicephalus microplus Gut in Response to Theileria equi Infection

Rhipicephalus microplus is the only tick species known to serve as a biological vector of Theileria equi for horses and other equids in Brazil. The protozoan T. equi is one of the causal agents of equine piroplasmosis, a major threat in horse breeding systems. Vector competence is closely linked to the pathogens' ability to evade tick defense mechanisms. However, knowledge of tick immune response against infections by hemoparasites of the Theileria genus is scarce. In the present study, the expression of genes involved in immune signaling pathways of R. microplus adults' guts when challenged with a high or low parasitic load of T. equi was evaluated. This research demonstrates divergences in the immune gene expression pattern linked to T. equi infection in R. microplus since the Toll, IMD, and JNK signaling pathways were transcriptionally repressed in the guts of adult ticks infected with T. equi. Moreover, the results showed that different infectious doses of T. equi induce differential gene expression of key components of immune signaling cascades in R. microplus gut, suggesting a link between the intensity of infection and the activation of tick immunity response. The present study adds knowledge to elucidate the gut immune signaling response of R. microplus to T. equi infection. In addition, the generated data can serve as a basis for further investigations to develop strategies for controlling and preventing equine piroplasmosis.

Dynamics of Theileria equi Infection in Rhipicephalus (Boophilus) microplus during the Parasitic Phase in a Chronically Infected Horse

Experimental studies have demonstrated that Rhipicephalus (Boophilus) microplus transmits Theileria equi to horses. However, the degree and dynamics of this protozoan infection in the vector’s organism have not been fully elucidated. Therefore, this study aimed to evaluate the infection rate and parasitic load of T. equi in R. (B.) microplus, the infection dynamics in this arthropod during experimental infestation in a horse chronically infected with T. equi, and to evaluate the trans-stadial and intrastadial transmission competence of T. equi by R. (B.) microplus. The experimental infestation period of R. (B.) microplus on the horse was 33 days, but males were found on the animal up to 60 days post-infestation. After the fifth day post-infestation, ticks and equine blood were collected every two days. Whole ticks from the same developmental stage collected in the same day were pooled. Adult ticks were dissected to extract salivary glands and gut. DNA extraction was performed for all the samples, and they were then submitted to qPCRs for T. equi diagnosis. Freshly molted nymphs collected as larvae in the horse and freshly molted males and females collected as nymphs in the horse showed equal to or greater than 75% positivity for T. equi, indicating a strong possibility of trans-stadial transmission. The longest permanence of the male ticks on the horse associated with the high positivity rate of this type of sample for T. equi indicate that the male may play a role in the intrastadial transmission of T. equi to infection-free horses. The salivary glands displayed 77.78% positivity for T. equi and presented a higher infection rate at the end of the experimental period (100% from 29 to 33 days post-infection). This study shows that R. (B.) microplus has high T. equi infection rates and that the infection rate and parasitic load increased over the experimental period. These findings confirm the importance of chronically infected horses with T. equi as a source of infection for R. (B.) microplus.

Characterization of the Rhipicephalus (Boophilus) microplus Sialotranscriptome Profile in Response to Theileria equi Infection

This study intends to characterize the sialotranscriptome profile of Rhipicephalus (Boophilus) microplus in response to Theileria equi and identify genes of interest with differential genomic expression, indicating relevant targets in the tick–protozoan interactions. The experimental design consisted of RNA sequencing from uninfected and T. equi-infected R. microplus salivary glands (SGs) to obtain transcriptomic profiles for characterization and comparison. A total of 288,952 transcripts were obtained from both tick profiles, 3456 transcripts (p < 0.05) differentially expressed in response to T. equi infection. The uninfected SGs’ registered 231,179 transcripts, of which 155,359 were annotated. The most transcribed sequences were female-specific histamine binding protein and lipocalins. Regarding the T. equi-infected SGs, from the 238,964 assembled transcripts, 163,564 were annotated. The most transcribed sequences were histone demethylase JARID1 and Y-box-binding protein. Five transcripts (cystatin, arginase, nuclear factor κB kinase inhibitor subunit β (IκB), IκB delta, lysosomal-trafficking regulator, and reeler protein) presented the gene ontology (GO) category “response to protozoan” and were exclusively displayed in the T. equi-infected profile. The transcriptome of T. equi was also analyzed, registering 4728 hits. The study’s genetic and molecular information would be of great value for future studies and biotechnological applications envisaging disease control.

Serological detection and risk factors for equine piroplasmosis in the semiarid region of Pernambuco, Northeastern Brazil

Equine piroplasmosis, an economically important disease in horses, has so far not been reported in Pernambuco state, Brazil. This study aimed to evaluate the seroprevalence of anti-Babesia caballi and anti-Theileria equi antibodies based on the detection of these agents in equine blood and in ticks on horses in the municipality of Petrolina, Pernambuco, northeastern Brazil. Blood samples were drawn from 393 horses and sera were examined by ELISA. The presence of tick infestations was evaluated, and 101 ticks were subjected to DNA amplification for the detection of Babesia spp. by polymerase chain reaction (PCR). No parasites were detected in the blood smears. Anti-B. caballi and anti-T. equi antibodies were found in 27.2% (107/393) and 34.8% (137/393) horses, respectively. Infestation by Dermacentor nitens was detected in 4.3% (17/393) of the horses. There was no DNA amplification of the agents in ticks. The risk factors for the presence of anti-T. equi antibodies (P < 0.05) were: purebred (P < 0.001), animals older than 156 months (P = 0.014), and the presence of ticks (P = 0.001). No risk factors for B. caballi were identified. This study confirmed the circulation of agents of equine piroplasmosis in the municipality of Petrolina, state of Pernambuco, Brazil.

The Complexity of Piroplasms Life Cycles

Although apicomplexan parasites of the group Piroplasmida represent commonly identified global risks to both animals and humans, detailed knowledge of their life cycles is surprisingly limited. Such a discrepancy results from incomplete literature reports, nomenclature disunity and recently, from large numbers of newly described species. This review intends to collate and summarize current knowledge with respect to piroplasm phylogeny. Moreover, it provides a comprehensive view of developmental events of Babesia, Theileria, and Cytauxzoon representative species, focusing on uniform consensus of three consecutive phases: (i) schizogony and merogony, asexual multiplication in blood cells of the vertebrate host; (ii) gamogony, sexual reproduction inside the tick midgut, later followed by invasion of kinetes into the tick internal tissues; and (iii) sporogony, asexual proliferation in tick salivary glands resulting in the formation of sporozoites. However, many fundamental differences in this general consensus occur and this review identifies variables that should be analyzed prior to further development of specific anti-piroplasm strategies, including the attractive targeting of life cycle stages of Babesia or Theileria tick vectors.

Serological detection and molecular characterization of piroplasmids in equids in Brazil

Equine piroplasmosis is a disease caused by the hemoparasites Babesia caballi and Theileria equi and is considered to be the most important parasitic infection affecting Equidae. The objective of the present study was to carry out an epidemiological molecular and serological survey for the presence of these two protozoal organisms in equids from the northwestern region of the State of Rio Grande do Sul (RS), south Brazil. For this purpose, blood samples were collected from 90 equids in the city of Passo Fundo, RS, Brazil. Those were animals used for sport activities, outdoor recreational riding, and work including cattle herding and mounted patrol. Anti-T. equi and anti-B. caballi IgG antibodies were detected in the sera of those animals by commercial ELISA kits. The molecular diagnosis of equine piroplasmosis due to T. equi or B. caballi (or both) consisted in the amplification of the 18S rRNA gene by nested PCR followed by sequencing of the amplified PCR product and sequence comparison and phylogenetic analysis of the isolates; 17 (18.9%) and 5 (5.55%) out of the 90 serum samples tested in this study were positive for T. equi and B. caballi, respectively. Piroplasmid 18S rRNA gene fragments were detected by PCR in 24.4% (22/90) of the samples analysed and shared 99-100% identity with sequences of T. equi by BLASTn. Samples for the phylogenetic analysis were divided into 2 groups. In group A, there was close phylogenetic relationship between 4 sequences and sequences previously reported along the US-Mexico border, in South Africa, and in Brazil. There was a phylogenetic proximity between 5 samples from group B and samples tested by other authors in the US and Spain. Variation of the 18S rRNA gene allowed the identification of 9 new T. equi genotypes in the geographical region studied.

Molecular characterization of Theileria equi in horses from the state of Rio de Janeiro, Brazil

Theileria equi is one of the etiologic agents of the equine piroplasmosis. This infectious disease is transmitted by ticks and is a worldwide problem in the international horse movement. The 18S rRNA gene of T. equi is often used for genotyping and phylogenetic purpose. This study aimed to analyze the degree of the heterogeneity of the 18S rRNA gene of T. equi in horses from the state of Rio de Janeiro, Brazil. The complete T. equi 18S rRNA sequences were obtained from twenty naturally infected horses. The PCR amplicons were cloned and sequenced. The phylogenetic analyses were performed using a set of T. equi 18S rRNA sequences and other related organisms available in ARB-Silva database. There were twelve distinct T. equi 18S rRNA gene sequences circulating in horses in the state of Rio de Janeiro, Brazil. Monophyletic clades with 2% evolutionary divergence between clades and high bootstrap value were the support to divide T. equi sequences in three distinct clades. The sequences from this study grouped into clades I (70%, n=14/20) and II (30%, n=6/20). All of the T. equi sequences grouped within a node other than the theileriids. This study reported a clear division of two distinct genotypes of T. equi 18S rRNA sequences in state of Rio de Janeiro, Brazil, and it demonstrates that distinct isolates of T. equi can coexist in the same geographic region.

Genetic diversity of piroplasmids species in equids from island of São Luís, northeastern Brazil

Abstract Equine piroplasmosisis, a tick-borne disease caused by the intra-erythrocytic protozoans Babesia caballi and Theileria equi, has economic importance due to the international trade and the increased movement of horses all over the world. The goal of this study was to evaluate the occurrence of phylogenetic diversity of T. equi and B. caballi genotypes among infected equids from São Luís Island, state of Maranhão, northeastern Brazil. Between December of 2011 and June of 2012, EDTA-blood and serum samples were collected from 139 equids (90 donkeys, 39 horses and 10 mules). From 139 serum samples submitted to ELISA assay, IgG antibodies to T. equi and B. caballi were detected in 19.4% (27/139) and 25.2% (35/139), respectively. Among sampled animals, 21.6% (30/139) and 55.4% (77/139) were positive for cPCR assays for T. equi and B. caballi, based on ema-1 and rap-1 genes, respectively. Overall, the T. equi sequences (n=7) submitted to Maximum Likelihood analysis (based on a 18S rRNA fragment of 1700 bp after alignment) grouped into three main groups, which were subdivided in eight clusters. The present work showed that different genotypes of T. equi and B. caballi circulate among equids in Brazil.

Seroprevalence rates of antibodies against Theileria equi in team roping horses from central-western region of Paraná

The purpose of this study was to estimate the prevalence of Theileria equi in horses from central western region of Paraná state, Brazil. The presence of antibodies IgG against T. equi was determined in serum samples obtained from 400 team roping horses of the district of Guarapuava by the enzyme-linked immunosorbent assay (ELISA). Results showed that 242 (61%) animals were positive which demonstrates that equine piroplasmosis is widespread and therefore it might be a contributing factor for the irregular performance among athletes horses in the region studied. No association regarding age and sex were observed (p>0.05). To our knowledge, this is the first report describing a serological survey on equine piroplasmosis in the state of Paraná, Brazil.

Vector ecology of equine piroplasmosis

Equine piroplasmosis is a disease of Equidae, including horses, donkeys, mules, and zebras, caused by either of two protozoan parasites, Theileria equi or Babesia caballi. These parasites are biologically transmitted between hosts via tick vectors, and although they have inherent differences they are categorized together because they cause similar pathology and have similar morphologies, life cycles, and vector relationships. To complete their life cycle, these parasites must undergo a complex series of developmental events, including sexual-stage development in their tick vectors. Consequently, ticks are the definitive hosts as well as vectors for these parasites, and the vector relationship is restricted to a few competent tick species. Because the vector relationship is critical to the epidemiology of these parasites, we highlight current knowledge of the vector ecology of these tick-borne equine pathogens, emphasizing tick transmissibility and potential control strategies to prevent their spread.

Review of equine piroplasmosis

Equine piroplasmosis is caused by one of 2 erythrocytic parasites Babesia caballi or Theileria equi. Although the genus of the latter remains controversial, the most recent designation, Theileria, is utilized in this review. Shared pathogenesis includes tick-borne transmission and erythrolysis leading to anemia as the primary clinical outcome. Although both parasites are able to persist indefinitely in their equid hosts, thus far, only B. caballi transmits across tick generations. Pathogenesis further diverges after transmission to equids in that B. caballi immediately infects erythrocytes, whereas T.equi infects peripheral blood mononuclear cells. The recent re-emergence of T.equi in the United States has increased awareness of these tick-borne pathogens, especially in terms of diagnosis and control. This review focuses in part on factors leading to the re-emergence of infection and disease of these globally important pathogens.

Molecular epidemiology of Theileria equi in horses and their association with possible tick vectors in the state of Rio de Janeiro, Brazil

The aim of this study was to detect Theileria equi (Laveran 1901) DNA in horses and ticks using real-time PCR and to list the factors associated with infection in animals located in the Seropedica and Petropolis municipalities of the state of Rio de Janeiro. We tested blood samples from 314 horses and samples from 300 ticks, including 191 Amblyomma cajennense, 104 Dermacentor nitens, and 5 Ixodida larvae. Factors inherent to the horse, the ownership, and animal management were obtained from an epidemiological questionnaire and were evaluated in association with the presence of T. equi DNA in the animals. Among the horses in the study, 81 % (n = 253/314) presented T. equi DNA, and the animals of the Seropedica municipality had the highest infection frequency (91 %, n = 128/141, p < 0.001). The factors that had significantly different infection frequencies by chi-squared or Fisher's exact tests (p < 0.2) were included in a logistic regression model using the R programming package. Work and walking activity (odds ratio [OR] = 5.7, CI = 2.3-14.4), reproductive activity (OR = 3.8, CI = 1.3-11.5), and tick infestation (OR = 2.6, CI = 1.1-6.2) were factors that favored the presence of T. equi DNA in the animals (p < 0.05). Among the tick samples, A. cajennense and D. nitens were the identified species. The presence of T. equi DNA was observed in 9.9 % (n = 19/191) of the A. cajennense samples and 3.8 % (n = 4/104) of the D. nitens samples. A multivariate analysis revealed that the presence of A. cajennense on the animals (OR = 4.1, CI = 1.8-9.1) was associated with the presence of T. equi DNA in the horses. In the studied municipalities, activities related to work, walking, and reproduction and the presence of ticks on the horses, particularly an intense infestation of A. cajennense, are factors that lead to infection with T. equi in the horses.

Neutral lipid composition changes in the fat bodies of engorged females Rhipicephalus microplus ticks in response to fungal infections

The tick's fat body plays an essential role in energy storage and utilization. This study aimed to analyze the fat body neutral lipid composition in Rhipicephalus microplus engorged females. In the first study (physiological profile of untreated ticks), the lipid analysis took place over the course of 4 days; the engorged females were incubated at optimal conditions and their fat bodies were dissected daily. Fat body lipid analysis after fungal infection with Metarhizium anisopliae sensu lato (s.l.) or Beauveria bassiana s.l. was performed with four groups: one without any treatment, one that was inoculated with a solution of 0.1 % Tween 80 in water, and two groups that were inoculated with M. anisopliae or B. bassiana conidial suspensions. The fat bodies were dissected 24 and 48 h after infection. Lipid analysis was conducted by thin-layer chromatography on a silica plate. The results of the physiological profile showed that the amounts of triacylglycerol (TAG) and free cholesterol (CHO) decreased with time, whereas cholesterol ester (CHOE) increased on the second and fourth days. Following M. anisopliae or B. bassiana infection, there was an increase in the amount of CHO after 24 h, whereas the other lipid classes were not altered. M. anisopliae caused an increase in CHOE and TAG and a reduction in CHO at 48 h after infection; however, B. bassiana infection did not cause significant alterations in the concentrations of these lipids. M. anisopliae and B. bassiana infection changed the fat body metabolism of engorged female R. microplus ticks. This study provides the first report of changes in the neutral lipid composition of the R. microplus fat body.

Factors associated to Theileria equi in equids of two microregions from Rio de Janeiro, Brazil

Serum samples from 714 equids of Itaguaí and Serrana microregions, Rio de Janeiro, southeastern Brazil, were examined by indirect fluorescent antibody test (titer 1:80) for Theileria equi. The prevalence in the microregions and factors associated with seropositivity were evaluated and the prevalence ratio (PR) calculated. The overall prevalence of T. equi infection was 81.09% (n = 579), with higher prevalence (p < 0.05) in the Itaguaí (85.43%) when compared to Serrana microregion (76.92%). The geographic area, altitude, farming condition and area of origin of equids were associated (p < 0.05) with seropositivity for T. equi. Equids reared in the Itaguaí microregion (PR = 1.11, p = 0.003) and at altitudes below 500 m (PR = 1.10; p = 0,014) were more likely to be seropositive for T. equi. Furthermore, when equids were born in the farm (PR = 1.10, p = 0.008) and reared with poor farming conditions (PR = 1.13, p = 0.018) they were more likely to be exposed to T. equi. The main ticks found on equids were Amblyomma cajennense and Dermacentor (Anocentor) nitens. The microregions studied are endemic areas for equine theileriosis and there exists enzootic stability for T. equi. Only factors related to the collection area of serum samples influenced the seropositivity of equids for T. equi in that region.

Molecular and serological detection of Theileria equi and Babesia caballi in donkeys (Equus asinus) in Brazil

Piroplasmosis in donkeys has been recognized as a serious problem of major economic importance, since the affected animals manifest loss of appetite and decreased working capacity. The present work is aimed at detecting infection or exposure of donkeys in São Paulo, Brazil to Theileria (T.) equi and Babesia (B.) caballi using molecular and serological approaches. EDTA-blood and serum samples were collected from 88 donkeys (Equus asinus). From 88 sampled donkeys, 65 (73.86%; 95% confidence interval, PI=63.41, 82.65) and 82 (93.2%; 95% confidence interval, PI=85.75, 97.46) animals showed IgG antibodies to T. equi (by ELISA) and B. caballi (by IFAT), respectively. Twenty-eight (31.81%; 95% confidence interval, PI=22.3, 42.61) and 18 (20.45%; 95% confidence interval, PI=12.6, 30.39) donkeys were positive to T. equi and B. caballi nested PCR assays, respectively. The results indicated that T. equi and B. caballi are prevalent among donkeys in Brazil.

Production of recombinant EMA-1 protein and its application for the diagnosis of Theileria equi using an enzyme immunoassay in horses from São Paulo State, Brazil

The erythrocytic-stage surface protein, Equi Merozoite Antigen 1 (EMA-1), is a major candidate for the development of a diagnostic antigen for equine piroplasmosis. In order to establish an effective diagnostic method for practical use, the gene encoding the entire EMA-1 of Theileria equi Jaboticabal strain was cloned and expressed in Escherichia coli as a histidine-tagged protein (His6-EMA1). The expressed EMA-1 reacted with specific antibodies in Western blot and had an apparent molecular mass of 34 kDa which was largely consistent with its theoretical value. The nucleotide sequence of the EMA-1 gene of Jaboticabal strain was comparatively analyzed with other published sequences. The results indicated a high degree of homology with EMA-1 genes of all other strains isolated from various countries. The recombinant purified His6-EMA1 protein was tested in an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies anti-T. equi in horses. The ELISA clearly differentiated T. equi-infected from Babesia caballi-infected horse sera or normal horse sera. Field serum samples collected from horses in the State of São Paulo, Southeastern Brazil, were examined for the diagnosis of T. equi infection by ELISA. Of 170 samples analyzed, 95.88% (163/170) were positive for T. equi infection. These results suggest that the His6-EMA1 protein expressed in E. coli could be a reliable immunodiagnostic antigen for ELISA test and that T. equi infection is a serious concern in the State of São Paulo, Brazil.

Serological prevalence of Babesia caballi and Theileria equi in horses of Lara State, Venezuela

The main objective of this study was to demonstrate the occurrence of equine piroplasmosis (EP) in horses of Lara State, Venezuela, and to correlate it with the factors host's sex and age in order to know the epidemiology of this disease at the Venezuelan Centroccidental Region. Antibody levels to Babesia caballi and Theileria equi were assessed in 360 equine serum samples, collected from 9 municipalities of Lara State, using an ELISA technique with recombinant antigens and monoclonal antibodies (Mabs). Antibodies to B. caballi were found in 254 horses (70.6%), whereas 181 animals (50.3%) were detected as seropositives to T. equi. In addition, 128 samples (35.56%) were seropositives to both hemoparasites. There were no significant differences between the seropositivity to B. caballi and T. equi with the factors sex and age of the horses. These results show that Lara State is an enzootic area for equine piroplasmosis, and are a contribution to a partial knowledge of the dynamic of this disease in Venezuela.

[Biological characteristics of Boophilus microplus (Acari: Ixodidae) on dog under experimental infestation]

Boophilus microplus, a common parasite of cattle, has eventually reported in dogs. To describe biological features of this parasitism, one dog was experimentally infested with 10,000 larvae of B. microplus which were previously held in acclimatized camera at 27+/-1 degrees C and relative humidity up to 80%. The mean of parasitic phase was 24.4+/-1.50 days, with 0.42% of recovery rate. Of 21 natural detached B. microplus females, six engorged enough (75.1+/-30.23 mg) to achieve posture. The mean period of pre-posture was 4.33+/-1.37 days and the means period of posture was 9.17+/-2.32, producing a mean of 18.78+/-15.34 posture weight. The mean of eggs production index observed was 22.38%. The results showed that B. microplus females fed on dogs to complete their life cycle. The females collected were able to ovoposite viable eggs suggesting that dogs can be a possible alternative hosts to B. microplus, especially when there is no other preferential host species available.

Detection and molecular characterization of Babesia caballi and Theileria equi isolates from endemic areas of Brazil

Blood samples were collected from 487 adult horses, including 83 pregnant mares, at a slaughterhouse located in Araguari, Minas Gerais State, Brazil. For each blood sample, the packed cell volume (PCV) was determined, and Giemsa-stained smears were microscopically examined for the presence of hemoparasites. The plasma was examined by the indirect fluorescent antibody test for detection of antibodies against Babesia caballi and Theileria equi. In addition, DNA was extracted and analyzed by a multiplex real-time polymerase chain reaction (PCR), specific for B. caballi and T. equi. Products of PCR were sequenced and compared with each other and with known sequences. The serological results showed a total prevalence of 91.0% for T. equi and 83.0% for B. caballi, while by PCR, prevalences of 59.7% for T. equi and 12.5% for B. caballi were observed. However, no correlations were seen between positivity (neither by serology nor by PCR) and PCV values. As expected, the microscopic examination of blood smears showed low sensitivity in detecting the infections when compared to the PCR. Only 35 out of 570 blood smears were positive, with parasitemias below 0.1%. No congenital transmission was detectable. As far as sequencing is concerned, no differences were seen among the isolates of each species nor among them and known sequences available. These results confirm, by molecular methods, the high prevalence rates of T. equi and B. caballi infections in carrier horses in Brazil. However, no diversity was observed among the isolates within the studied regions.

Infectivity rate and transmission potential of Hyalomma anatolicum anatolicum ticks for Babesia equi infection

The infectivity rate of Babesia equi in the salivary glands of Hyalomma anatolicum anatolicum was assessed. The hungry nymphs were fed on a donkey experimentally infected with B. equi. The engorged dropped-off nymphs were collected at different levels of parasitaemia and kept in BOD incubator. After ecdysis, the hungry adults were prefed on rabbits for different time intervals, thereafter the salivary glands were dissected out and acini were examined after methyl green pyronin (MGP) staining. A total of 134 male and 139 female ticks were dissected out. Average infected acini per tick were found to be significantly higher (p<0.05) in male as compared to the female ticks. Further, maximum infected acini in both male and female ticks were found at 24h of prefeeding on rabbits and overall infected acini per tick increased with rise in parasitaemia. The release of infected ticks on susceptible donkeys resulted in development of clinical babesiosis.

Amblyomma cajennense (Acari: Ixodidae): salivary gland cells of partially engorged females ticks and the production of lipid by their mitochondria

Morphologically, the salivary glands of ticks are paired structures consisting of a secretory and an excretory portion, lacking a reservoir for the storage of the secretion. The secretory portion is composed in females by cells that form acini classified into the types I, II, and III. The excretory possess a major duct, from which arise several intermediate ducts that then subdivide to form the canaliculi or acinal tubules, which end at the acini from where they collect the secretion. The present study describes the ultrastructural changes that occur in the mitochondria of cells of the acini I, II, and III in the salivary glands of partially engorged females of the Cayenne tick Amblyomma cajennense. The results show that this organelle exhibits completely disarrayed crests due to the presence of lipidic material inside the matrix and between the crests, thus demonstrating their participation in the production of the lipids that would be used structurally by the cells. These organelles with ultrastructural changes were denominated derived mitochondria.

Ability of the vector tick Boophilus microplus to acquire and transmit Babesia equi following feeding on chronically infected horses with low-level parasitemia

The protozoan parasite Babesia equi replicates within erythrocytes. During the acute phase of infection, B. equi can reach high levels of parasitemia, resulting in a hemolytic crisis. Horses that recover from the acute phase of the disease remain chronically infected. Subsequent transmission is dependent upon the ability of vector ticks to acquire B. equi and, following development and replication, establishment of B. equi in the salivary glands. Although restriction of the movement of chronically infected horses with B. equi is based on the presumption that ticks can acquire and transmit the parasite at low levels of long-term infection, parasitemia levels during the chronic phase of infection have never been quantified, nor has transmission been demonstrated. To address these epidemiologically significant questions, we established long-term B. equi infections (>1 year), measured parasitemia levels over time, and tested whether nymphal Boophilus microplus ticks could acquire and, after molting to the adult stage, transmit B. equi to naive horses. B. equi levels during the chronic phase of infection ranged from 10(3.3) to 10(6.0)/ml of blood, with fluctuation over time within individual horses. B. microplus ticks fed on chronically infected horses with mean parasite levels of 10(5.5) +/- 10(0.48)/ml of blood acquired B. equi, with detection of B. equi in the salivary glands of 7 to 50% of fed ticks, a range encompassing the percentage of positive ticks that had been identically fed on a horse in the acute phase of infection with high parasitemia levels. Ticks that acquired B. equi from chronically infected horses, as well as those fed during the acute phase of infection, successfully transmitted the parasite to naive horses. The results unequivocally demonstrated that chronically infected horses with low-level parasitemia are competent mammalian reservoirs for tick transmission of B. equi.

Morphological characterization of the ovary and vitellogenesis dynamics in the tick Amblyomma cajennense (Acari: Ixodidae)

In this work we describe the internal morphology of the female reproductive system of the cayenne tick Amblyomma cajennense. This system is represented by a panoistic ovary, which lacks nurse cells in the germarium. This ovary consists of a single tube, in which a large number of oocytes develop asynchronously, thus accompanying the processes of yolk deposition in the oocytes. The oocytes were classified into stages that varied from I to V, according to: cytoplasm appearance, presence of the germ vesicle, presence of yolk granules, and presence of chorion. The study of vitellogenesis dynamics suggest that the yolk elements are deposited in the oocyte following a preferencial sequence, in which the lipids are the first to appear, followed by proteins an finally by the carbohydrates. In this way the yolk of A. cajennense ticks have these three elements that may be free in the cytoplasm or chemically bounded forming glycoprotein or lipoprotein complexes.

Expression of equi merozoite antigen 2 during development of Babesia equi in the midgut and salivary gland of the vector tick Boophilus microplus

Equi merozoite antigens 1 and 2 (EMA-1 and EMA-2) are Babesia equi proteins expressed on the parasite surface during infection in horses and are orthologues of proteins in Theileria spp., which are also tick-transmitted protozoal pathogens. We determined in this study whether EMA-1 and EMA-2 were expressed within the vector tick Boophilus microplus. B. equi transitions through multiple, morphologically distinct stages, including sexual stages, and these transitions culminate in the formation of infectious sporozoites in the tick salivary gland. EMA-2-positive B. equi stages in the midgut lumen and midgut epithelial cells of Boophilus microplus nymphs were identified by reactivity with monoclonal antibody 36/253.21. This monoclonal antibody also recognized B. equi in salivary glands of adult Boophilus microplus. In addition, quantification of B. equi in the mammalian host and vector tick indicated that the duration of tick feeding and parasitemia levels affected the percentage of nymphs that contained morphologically distinct B. equi organisms in the midgut. In contrast, there was no conclusive evidence that B. equi EMA-1 was expressed in either the Boophilus microplus midgut or salivary gland when monoclonal antibody 36/18.57 was used. The expression of B. equi EMA-2 in Boophilus microplus provides a marker for detecting the various development stages and facilitates the identification of novel stage-specific Babesia proteins for testing transmission-blocking immunity.

Ultrastructure of Babesia equi trophozoites isolated in Minas Gerais, Brazil

A transmission electron microscope study was carried out on Babesia equi obtained from a splenectomized horse, from the municipality of Santa Luzia, Minas Gerais, Brazil. The isolate was inoculated into two splenectomized foals (1.05 x 10(10) parasitized erythrocytes by B. equi). Trophozoites have a single membrane in direct contact with the cytoplasm of the red blood cells, a prominent nucleus, well-developed rough and smooth endoplasmic reticulum, numerous free ribosomes and small food vacuoles. B. equi trophozoites have a cytostome and a long tubular feeding structure in direct contact with the blood plasma.

Detection of natural infection of Boophilus microplus with Babesia equi and Babesia caballi in Brazilian horses using nested polymerase chain reaction

The potential role of Boophilus microplus as a natural tick vector of Babesia equi and Babesia caballi in Brazilian horses was assessed using nested polymerase chain reaction (PCR)-based marker assay. B. equi merozoite-specific 218bp gene fragment was detected in almost 96% of horse blood samples, and 45.3-62.5% of females, eggs, larvae, and nymphs of B. microplus collected from 47 horses at Campo Grande in the State of Matto Grosso, Brazil. Except for the partially-fed female ticks, the B. caballi-specific 430bp gene fragment was amplified from horse blood samples, and all developmental stages. Parasite DNA from both species was detected in horse blood samples and B. microplus, with the preponderance of B. equi DNA. No DNA samples were positive solely for B. caballi parasite. Only 32% of the Giemsa-stained thin blood smears were positive for Babesia parasites, as against detection of B. equi parasite DNA in 95.7% of the blood samples by nested PCR. We have obtained molecular evidence that strengthens earlier experimental and ultrastructural studies in Brazil incriminating B. microplus as a natural vector of B. equi, and possibly of B. caballi. The detection of B. equi and B. caballi DNA in eggs and larvae of B. microplus is likewise suggestive of the possibility of both transovarial and transstadial parasite transmission in this tick vector.

Detection of equine Babesia spp. gene fragments in Dermacentor nuttalli Olenev 1929 infesting mongolian horses, and their amplification in egg and larval progenies

Babesia equi (EMA-1) and Babesia caballi (BC48) gene fragments were amplified by polymerase chain reaction (PCR), in blood samples, and partially fed-females and egg and larval progenies of Dermacentor nuttalli, collected from horses in Altanbulag, Tuv Province, Mongolia. While Babesia parasite DNA was detected in some horse blood samples during the first PCR, all positive cases in partially fed-female ticks, eggs and larvae were confirmed by nested PCR. Present study reinforces earlier similar findings in unfed D. nuttalli ticks collected from an open space vegetation in Bayanonjuul, Tuv Province in Central Mongolia, pointing to the most likely important role of D. nuttalli in the transmission of equine babesiosis in Mongolia. The detection of parasite DNA in eggs and larval progenies is likewise suggestive of transovarial parasite transmission in this tick species.

Dermacentor variabilis and boophilus microplus (Acari: Ixodidae): experimental vectors of Babesia equi to equids

The experimental vector competence of five laboratory-reared ixodid tick species representing three genera [Amblyomma americanum (L.), Boophilus microplus (Canestrini), D. andersoni Stiles, D. occidentalis Marx, and D. variabilis (Say)] for Babesia equi (Laveran 1901) was evaluated by delayed transfer of male ticks from infected to susceptible equids or by infesting the latter animals with adult ticks previously fed as nymphs on infected equids. After feeding for 5, 6, or 13 d on acquisition hosts, ticks were forcibly removed and held off the host at 26 degrees C, approximately 93% RH, and a photoperiod of 14:10 (L:D) h for 6, 12, or 27 d. Intrastadial transmission to susceptible ponies by D. variabilis males, and transstadial transmission to susceptible burros by B. microplus adults, was demonstrated by blood smear and indirect immunofluorescence serology. The data indicated that male D. variabilis and adult B. microplus, tick species that occur on equids in North America and, in the case of the latter tick, also extensively in tropical and subtropical regions of the world, may be competent natural vectors of B. equi

Epidemiological aspects of Babesia equi in horses in Minas Gerais, Brazil

The prevalence of Babesia equi in two climatic regions of Minas Gerais state was determined using the indirect fluorescent antibody test (IFAT) with blood samples obtained from horses in two slaughterhouses. Of 399 samples, 241 (60.4%) showed a positive reaction. Anti-B. equi antibody was detected in every county studied, the prevalence being 59.7% for horses in the area where the temperature rises above 18 degrees C in winter and 61.4% in the area where it remains below 18 degrees C, indicating that climatic variation has no substantial effect on the prevalence of the infection in Brazil. Blood samples collected from all 95 horses on a ranch in the state of Minas Gerais, Brazil, on which clinical babesiosis had never been reported, were subjected to the IFAT Anti-B. equi antibodies were detected in horses of all ages, but with a significantly lower prevalence in animals less than 6 months old.

Seroepidemiologic studies on Babesia equi and Babesia caballi infections in Brazil

Horses from six stud farms representing the most frequent types of horse breeding in Brazil were tested for Babesia antibodies by the IFA test. The farms are located at the tropic of Capricorn at an altitude of 472-715 m where temperatures below 0 degrees C may occur. Horses of conventional stud farms were infested with Dermacentor nitens, Amblyomma cajennense, and Boophilus microplus. Infestation with Bo. microplus was associated with direct or indirect contact of horses with cattle, and was not detected at professional stud farms. At one large professional stud farm, only D. nitens was observed. Prevalence of Babesia equi correlated positively (p<0.001) with contact of pastured horses to cattle (67.1% versus 17.5%). The IFA test was validated using sera from 92 non-infected horses and from 18 ponies infected experimentally with the USDA strains of B. equi or B. caballi or with the Brazilian isolates from the study area. Differences in test results obtained using antigens from USDA strains or Brazilian isolates were not significant. The specificity was 100% except for the IFA test using Brazilian antigen of B. caballi (98%). The sensitivity was 100% except for the IFA test using the USDA antigen of B. caballi. Accuracy of the tests ranged from 98 to 100%, and predictive values from 99 to 100%. Only 59% (132/224) of sera, positive by the IFA test for B. equi, tested positive by CF test, and 45% (232/515) of sera, positive by the IFA test for B. caballi, also tested positive by CF test. In all, 740 field sera from 140 horses, including 63 mares and their foals, were tested. Prevalence and incidences of B. caballi infections were significantly higher than those of B. equi infections: 49.2% (31/63) of the mares were infected with B. equi, but 79.4% (50/63) with B. caballi; 36% (18/50) of the foals became infected with B. equi within 12 months, but 100% (50/50) with B. caballi within 10 months. Maternal antibodies against B. equi and B. caballi in foals were 44 (22/50) and 68% (34/50), respectively. Titers persisted for 1-5 months for B. equi and 1-4 months for B. caballi.