A case of transplacental transmission of Theileria equi in a foal in Trinidad

Revisiting the genotypes of Theileria equi based on the V4 hypervariable region of the 18S rRNA gene

Introduction

Equine theileriosis, an economically important disease that affects horses and other equids worldwide, is caused by a tick-borne intracellular apicomplexan protozoa Theileria equi. Genotyping of T. equi based on the 18S rRNA gene revealed the presence of two, three, four or five genotypes. In previous published reports, these genotypes have been labelled either alphabetically or numerically, and there is no uniformity in naming of these genotypes. The present study was aimed to revisit the phylogeny, genetic diversity and geographical distribution of T. equi based on the nucleotide sequences of the V4 hypervariable region of the 18S rRNA gene available in the nucleotide databases.

Methods

Out of 14792 nucleotide sequences of T. equi available in the GenBank™, only 736 sequences of T. equi containing the complete V4 hypervariable region of the 18S rRNA gene (>207 bp) were used in multiple sequence alignment. Subsequently, a maximum likelihood phylogenetic tree was constructed based on the Kimura 2-parameter model (K2+I).

Results

The phylogenetic tree placed all the sequences into four distinct clades with high bootstrap values which were designated as T. equi clades/ genotypes A, B, C and D. Our results indicated that the genotype B of Nagore et al. and genotype E of Qablan et al. together formed the clade B with a high bootstrap value (95%). Furthermore, all the genotypes probably originated from clade B, which was the most dominant genotype (52.85%) followed by clades A (27.58%), and C (9.78%) and D (9.78%). Genotype C manifested a comparatively higher genetic diversity (91.0-100% identity) followed by genotypes A (93.2-99.5%), and B and D (95.7-100%). The alignment report of the consensus nucleotide sequences of the V4 hypervariable region of the 18S rRNA gene of four T. equi genotypes (A-D) revealed significant variations in one region, between nucleotide positions 113-183, and 41 molecular signatures were recognized. As far as geographical distribution is concerned, genotypes A and C exhibited far-extending geographical distribution involving 31 and 13 countries of the Asian, African, European, North American and South American continents, respectively. On the contrary, the genotypes B and D exemplified limited distribution with confinement to 21 and 12 countries of Asian, African and European continents, respectively. Interestingly, genotypes A and C have been reported from only two continents, viz., North and South America. It was observed that genotypes A and C, and B and D exhibit similar geographical distribution.

Discussion

The present study indicated the presence of only four previously described T. equi genotypes (A, B, C and D) after performing the molecular analyses of all available sequences of the complete V4 hypervariable region of the 18S rRNA gene of T. equi isolates in the GenBank™.

Evidence of transplacental transmission of equine piroplasms Theileria equi and Babesia caballi in an Italian breed mare

Equine piroplasmosis (EP) is a vector borne disease caused by apicomplexans protists Babesia caballi (Nuttal et Strickland, 1910) and Theileria equi (Laveran, 1901). Carrier mares may transmit the infection transplacental resulting in neonatal piroplasmosis or abortions. This event has been described for T. equi by several authors over the world, but no evidence for B. caballi has been reported in Europe. In this study, vertical transmission for both parasites in an Italian breed mare has been confirmed using molecular and microscopic tools. Transplacental transmission is an underestimated problem mainly in endemic areas as it not only contributes to the spread and maintenance of the infection, but also produces significant economic losses.

Tick-borne pathogens in neotropical animals in Trinidad, West Indies

Background

Ticks are important vectors of many pathogens that have contributed to the morbidity and mortality of humans and domestic animals worldwide. Wildlife species have also been implicated as reservoir hosts of a variety of tick-borne pathogens. The objective of this study was to determine which tick-transmitted pathogens were present in the animals harvested from the forest in Trinidad for human consumption.

Methods

Thin blood smears from 43 neotropical animals were examined microscopically for tick-borne pathogens. Additionally, DNA extraction and PCR amplification of the 16S rRNA gene were used for amplification of Anaplasma and Ehrlichia while the gltA gene was used for Bartonella, and Rickettsia spp. and the 18S rRNA gene for Babesia, Hepatozoon and Theileria species.

Results

Pathogen DNA was amplified from four samples (a deer, collared peccary and two agoutis). Sequencing of the amplified products from the deer and collared peccary revealed 99.8% homology to Anaplasma bovis and 98.8% homology to Ehrlichia canis, respectively. Sequences from two agoutis revealed 90.4% homology to Theileria spp. DNA of Hepatozoon spp., Bartonella spp. Babesia spp. and Rickettsia spp. was not detected in any of the screened samples. An incidental finding in this study was the presence of bacteria in the blood of animals.

Conclusions

The results indicate that the DNA of tick-transmitted pathogens is present at a frequency of about 10% in the study population and suggests that neotropical mammals may serve as a source for the potential transmission of tick-borne pathogens to domestic animals and humans. In addition, physicians and hunters should be aware of the symptoms associated with zoonotic tick-borne pathogens so that these infections can be recognised, diagnosed and treated promptly. Bacteria present in carcasses can pose a food safety hazard and hunters should be trained in proper harvesting and handling of carcasses.

Graphical Abstract

Occurrence and Genetic Diversity of Babesia caballi and Theileria equi in Chilean Thoroughbred Racing Horses

This study aimed to serologically and molecularly survey Babesia caballi and Theileria equi in thoroughbred horses from racecourses in Chile. Additionally, the genetic diversity of the positive samples was assessed. A total of 286 thoroughbred horses from the Santiago and Valparaíso racecourses had their serum samples submitted to an ELISA for B. caballi and T. equi, and 457 samples (from the Santiago, Valparaíso, and Concepción racecourses) were tested with nested PCRs for the B. caballi 48 KDa rhoptry protein (RAP-1) and T. equi 18S rRNA genes. Selected RAP-1 and 18S positive products were sequenced to perform phylogenetic and haplotype analyses. An overall seroprevalence of 35.6% was observed for these Chilean racecourses: 23.7% for T. equi, 8.4% for B. caballi, and 3.5% for both agents. Overall, a 53.6% occurrence by nPCR was detected for the three Chilean racecourses: 44.2% for T. equi, 5.4% for B. caballi, and 3.9% for both agents. Phylogenetic analysis of T. equi and B. caballi showed genetic proximity with sequences previously detected in other countries. Haplotype analysis revealed a low diversity among the Chilean sequences, which may have originated from those reported in Brazil, Israel, or Cuba. Babesia caballi and T. equi were detected for the first time in Chilean thoroughbred horses.

Molecular and Serological Detection of Piroplasms in Horses from Nigeria

Equine piroplasmosis, an economically important disease of equids caused by the hemoprotozoan parasites Theileria equi, T. haneyi, and Babesia caballi, has a worldwide distribution. These parasites are transmitted by ixodid ticks. To improve the detection of horses in Nigeria exposed to piroplasm parasites, 72 horses with variable clinical signs of piroplasmosis were sampled from Northwest and Northcentral Nigeria and tested by nPCR and cELISA. Blood and serum samples were collected from each horse via jugular venesection. Individually, nPCR or cELISA failed to identify all horses exposed to piroplasms. A combination of species-specific nPCR and the OIE-approved T. equi and B. caballi cELISAs enhanced the detection of horses exposed to parasites. The results also demonstrated horses showing abnormal hematology were positive for only T. equi, except for one sample that was coinfected with T. equi and T. haneyi. We also identified ticks collected from some of the horses, with Rhipicephalus evertsi evertsi being the most prevalent. This study shows that a larger proportion of horses in the sample set were exposed to T. equi than B. caballi or T. haneyi. Additionally, ticks that have been previously reported as potential vectors for these parasites were found to have infested sampled horses. Further studies are needed to investigate which tick species are competent vectors for Theileria spp. and Babesia caballi in Nigeria.

Twenty Years of Equine Piroplasmosis Research: Global Distribution, Molecular Diagnosis, and Phylogeny

Equine piroplasmosis (EP), caused by the hemoparasites Theileria equi, Theileria haneyi, and Babesia caballi, is an important tick-borne disease of equines that is prevalent in most parts of the world. Infection may affect animal welfare and has economic impacts related to limitations in horse transport between endemic and non-endemic regions, reduced performance of sport horses and treatment costs. Here, we analyzed the epidemiological, serological, and molecular diagnostic data published in the last 20 years, and all DNA sequences submitted to GenBank database, to describe the current global prevalence of these parasites. We demonstrate that EP is endemic in most parts of the world, and that it is spreading into more temperate climates. We emphasize the importance of using DNA sequencing and genotyping to monitor the spread of parasites, and point to the necessity of further studies to improve genotypic characterization of newly recognized parasite species and strains, and their linkage to virulence.

Transplacental Transmission of Theileria equi Is Not a Common Cause of Abortions and Infection of Foals in Israel

Although the main route of transmission of Theileria equi is through tick feeding, transplacental transmission is also possible and may lead to abortion, or to the birth of a sick or carrier foal. The aim of this study was to evaluate the role of T. equi as a cause of abortions in Israel and the risk of foals being infected at a young age. Eight aborting mares were serologically evaluated for exposure to T. equi via the immunofluorescence antibody test (IFAT) and their aborted fetuses were evaluated using PCR and qPCR. In addition, five mares and their foals (aged 4-6 months) from a highly endemic farm were tested for T. equi infection using IFAT, PCR and qPCR. Five of the eight aborting mares were seropositive for T. equi; however, none of the aborted fetuses was infected. All five mares from the endemic farm were subclinically infected with T. equi. Of their five foals, one was infected, with relatively high parasitemia and different parasite genotype than its dam's, suggesting another source of infection. The results of this study suggest that transplacental transmission of T. equi is not common and does not appear to be a prominent cause of abortion in chronically infected mares.

Babesia (Theileria) equi genotype A among Indian equine population

Equine piroplasmosis, caused by Babesia (Theileria) equi, is well reported from many parts of India. However, literature regarding its prevalence from semi arid India is limited. Alongside, there is complete absence of information about genetic characterization of B.(T.) equi and the associated genotypes from India. In the present study, the prevalence of B.(T.) equi was studied from semi arid India using 18S ribosomal gene based PCR assay. An overall prevalence rate of 10.46% was recorded. PCR was more sensitive and specific in comparison with blood smears. The found isolates were sequenced. These sequences were aligned and submitted into NCBI. All the isolates showed 100% homology with each other and represented a single haplotype. When compared with other isolates of B.(T.) equi across India and globe, using Genetool and Mega 6 softwares, they showed 99.5-99.2% and 95.7-97.0% homologies, respectively. A unique substitution of G by A at 206 nucleotide position was reported in all found isolates in comparison to earlier reported isolates from India. The studied isolates were found to be phylogenetically closer to isolates from USA and Trinidad than to other parts of the world. All the Indian isolates belonged to genotype A of B.(T.) equi.

Abortion in association with transplacental Theileria equi infection in a mare from the State of Espírito Santo, southeast Brazil: case report

ABSTRACT Equine piroplasmosis is a tick-borne disease caused by the protozoan parasites Babesia caballi and Theileria equi. We report a case of abortion in association with transplacental Theileria equi infection in a mare from the State of Espírito Santo, southeast Brazil. An apparently healthy mare aborted at the tenth month of gestation. At necropsy, the subcutaneous tissue, skeletal muscles, and visible mucosae of the aborted fetus were pale, and there was moderate hydrothorax and marked splenomegaly. Microscopic findings included splenic lymphoid hyperplasia and nephrosis. Merozoite-infected erythrocytes were found within blood vessels of all organs examined and were most numerous in the brain. DNA extracted from the spleen, liver, kidney, and thymus was used as a template for PCR. Generic primers were employed for the detection of piroplasm 18S ribosomal gene. All samples were positive for piroplasm DNA by PCR. Amplicons were purified and then sequenced. Sequencing analysis of these amplicons revealed 98% identity to T. equi sequences. Based on our findings, we suggest that abortion in this case resulted from transplacental Theileria infection.

Assessment of equine piroplasmids in the Nhecolândia sub-region of Brazilian Pantanal wetland using serological, parasitological, molecular, and hematological approaches

Brazilian Pantanal is the world´s largest wetland ecosystem, where cattle's ranching is the most important economic activity. The objective of this study was to compile some epidemiological features on equine piroplasmids from the Nhecolândia sub-region of Pantanal wetland through the evaluation of the patterns of T. equi and B. caballi infections in different groups of horses; identification of the tick species that infest horses; and to study phylogenetic relationships among Theileria equi 18S rRNA gene sequences. During October 2015, blood and serum samples were collected from 170 horses in four different categories. Ticks, after identification, had their hemolymph and eggs examined for the presence of piroplasmid sporokinets. Also we searched parasites in the peripheral blood smears of the investigated horses. The number of red blood cells (RBCs) and the packed cell volume (PCV) ​​were determined to test for anemia in the infected animals, and exposure to B. caballi and T. equi was evaluated by enzyme-linked immunosorbent assay. "Catch all primers" based on 18S rRNA gene were used in polymerase chain reactions (PCR) to detect equine piroplasmids, followed by three nested PCRs for the phylogenetic analysis. The serological results showed that 61.8% and 52.9% of the horses sampled were exposed to T. equi and B. caballi, respectively. Piroplasmid DNA was detected in 43.5% of the horses analyzed. Our sequencing revealed 98-100% identity with some sequences previously published in GenBank for T. equi, and microheterogeneity among others. We found that 51.2% of the animals sampled were infested with Dermacentor nitens, Amblyomma sculptum, and Rhipicephalus (Boophilus) microplus, singly or co-infested. Since positive and negative animals presented similar RBC and PCV values, and no sporokinets were found on blood smears, hemolymph and eggs of the ticks collected, we suggest that infected equines can act as asymptomatic carriers for piroplasmosis in the studied region. Our results together showed the enzootic characteristic of equine piroplasmids in Pantanal region highlighting the importance of using different methods for detection these parasites. Moreover, breeding mares and foals should be monitored since they displayed the greatest occurrences for molecular test (59.0% and 86.1% respectively) and tick infestations (87.2% and 63.9% respectively).

Transplacental transmission of Theileria equi in mules: Should we worry?

Equine piroplasmosis, disease globally responsible for significant economic losses, is caused by the transmission of the hemoprotozoa Theileria equi and Babesia caballi by ticks. Transplacental transmission has been reported previously in horses, which is not the case for mules´ foals. The present study investigated, by Real Time-PCR (RT-PCR), the presence of both Theileria equi and Babesia caballi in newborn mules before the ingestion of colostrum. Blood samples of 18 mares and their respective mules´ foals were collected and analyzed by RT-PCR. Only one mare was positive for B. caballi. In contrast, 13 mares were positive for T. equi, with two foals (11.1%) positive for the same protozoon, both of affected mares. We may conclude that transplacental transmission of Theileria equi also occurs in mules which may be an important concern while breeding such animals.

Transplacental transmission of Theileria orientalis occurs at a low rate in field-affected cattle: infection in utero does not appear to be a major cause of abortion

Background

Bovine theileriosis, caused by the haemoprotozoan Theileria orientalis, is an emerging disease in East Asia and Australasia. Previous studies have demonstrated transplacental transmission of various Theileria spp. but molecular confirmation of transplacental transmission of T. orientalis has never been confirmed in the field. In this study, cow-calf (< 48 h old) pairs were sampled across 3 herds; opportunistic samples from aborted foetuses or stillborn calves were also examined. Molecular (multiplex qPCR) and serological (ELISA) methods were used to determine infection prevalence and the presence of anti-Theileria antibodies in each herd. In addition, pregnant heifers and foetal calves were sampled at abattoir and tested for the presence of T. orientalis by qPCR.

Results

The qPCR results indicated that, even though there was a high prevalence of T. orientalis infection in cows, the rate of transplacental transmission to their calves was low, with only one newborn calf from one herd and one foetus from the abattoir testing positive for T. orientalis DNA. Five aborted foetuses and stillborn calves, 3 of which were derived from a herd experiencing a high number of clinical theileriosis cases at the time of sampling, all tested negative for T. orientalis by qPCR. This suggests that in utero infection of calves with T. orientalis may not be a major driver of abortions during theileriosis outbreaks. Temporal monitoring of 20 calves born to T. orientalis-positive mothers indicated that T. orientalis was detectable in most calves between 10 and 27 days post-partum, consistent with prior field studies on adult cattle introduced to Theileria-affected herds. There was a positive correlation between the ELISA ratio of newborn calves and their mothers within 48 h of calving; however, maternal antibodies were only detectable in some calves and only for 4–4.5 weeks post-partum. All calves displayed high parasite loads peaking at 4–8 weeks post-partum, with only some calves subsequently mounting a detectable adaptive antibody response.

Conclusions

These findings indicate transplacental transmission of T. orientalis appears to play only a minor role in persistence of T. orientalis infection in the field; however calves are highly susceptible to developing high level T. orientalis infections at 4–8 weeks of age regardless of whether maternal antibodies are present post-partum.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2166-9) contains supplementary material, which is available to authorized users.

Theileria equi infection causing abortion in a mare in Brazil

The aim of this report was to confirm the cause of abortion to be Theileria equi acquired transplacentally in a mare in Federal District, Brazil. The aborted fetus showed a high parasitemia of erythrocytes (80%) by the oval and Maltese cross forms of T. equi. Necropsy of the fetus demonstrated congestion of organs, jaundice, anemia and pronounced spleno- and hepatomegaly. Twelve breeding mares, including the one that aborted and her fetus, tested positive for T. equi infection by universal and multiplex PCR assay. The absence of histopathologic changes such as inflammation and necrosis in the placenta and fetal tissues as well as the negative microbiological results and negative serology for Leptospira spp. in the mare that aborted were important to exclude other infectious agents that may be involved in equine abortion. This report highlights the transplacental transmission of T. equi infection in horses in endemic areas and reinforces the importance of investigating equine theileriosis as a possible cause of abortion in mares.

Molecular detection and prevalence of Theileria equi and Babesia caballi in horses of central Balkan

Equine piroplasmosis is significant tick-borne disease with wide distribution. The prevalence of equine piroplasmosis in Serbia, Montenegro and Bosnia and Herzegovina is unknown. In aim to obtain a first insight into the prevalence we performed molecular epidemiological study which included 142 horses, on seven locations in these three countries. We first performed PCR for the detection of a 450bp long section of the 18S rRNA of piroplasma-specific region. For all positive samples we have done multiplex PCR for the species detection. Species determination was further confirmed by sequencing PCR products of 10 randomly selected Theileria equi and all Babesia caballi samples. The overall prevalence rates in analysed region for T. equi and B. caballi were 22.5% and 2.1%, respectively. Possible risk factors (such as location, age, sex and activity) associated with PCR positivity were evaluated. Marked differences were found in prevalence between geographic areas. There was no significant association between positivity and age group. T. equi was more prevalent in females and farming horses. This is the first report on the molecular survey of T. equi and B. caballi in central Balkan. Further prevalence studies on definitive host and vectors in this region are necessary.

Molecular Detection of Theileria spp. in Livestock on Five Caribbean Islands

Theileria spp. are tick-transmitted, intracellular apicomplexan protozoan parasites infecting a wide range of animals. As there is very limited information on the prevalence of Theileria spp. in the Caribbean we used the recently described genus-specific pan-Theileria FRET-qPCR to identify infected animals in the region and a standard 18S rRNA gene PCR and sequencing to determine the species involved. We found Theileria spp. in 9% of the convenience samples of animals (n = 752) studied from five Caribbean islands. Donkeys (20.0%: 5/25) were most commonly infected, followed by sheep (17.4%, 25/144), cattle (6.8%; 22/325), goats (5.0%; 12/238), and horses (5.0%; 1/20). Six species of Theileria were identified: T. equi (donkeys, cattle, goats, and sheep), Theileria sp. OT3 (sheep and goats), Theileria sp. NG-2013a (cattle), Theileria sp. YW-2014 (donkeys), Theileria sp. B15a (goats), and Babesia vulpes or a closely related organism (sheep and goats). Only T. equi has been previously reported in the Caribbean. Our findings expand the known host ranges of Theileria spp. and the known distribution of the organisms around the world.

A field survey for the seroprevalence of Theileria equi and Babesia caballi in donkeys from Nuu Division, Kenya

Equine piroplasmosis is one of the most significant tick-borne disease of equids. The prevalence of this disease in donkeys of semi-arid Kenya remains largely unexplored. The primary objective of this study was to demonstrate the extent to which donkeys in Nuu division, Kenya have been exposed to the haemoprotozoans Babesia caballi and Theileria equi, the causative agents of equine piroplasmosis. The study also assessed the effect of age and sex on seroprevalence. A stratified sampling approach was used and three hundred and fourteen donkeys were sampled across nine sub-locations in Nuu division, Mwingi district. Serodiagnosis was via competitive inhibition enzyme linked immunosorbent assays (cELISA). The seroprevalence of T. equi was 81.2% (95% CI: 76.4-85.4). There was no significant difference in sub-location seropositivity, gender seropositivity or age related seropositivity. Antibodies against B. caballi were not detected (95% CI: 0-1.2). Findings from this study suggest that T. equi infection is endemic in Nuu division, Mwingi where it exists in a state of endemic stability. Existence of the infection should be communicated to animal health practitioners and donkey owning communities in the area.

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.

A rare clinical presentation of transplacental transmission and subsequent abortion by Babesia (Theileria) equi in a mare

The present article deals with the rare presentation of transplacental transmission and subsequent abortion by Babesia (Theileria) equi. A pregnant mare was brought with the history of fever and inappetence. Per rectal examination revealed absence of fremitus of the foetus. The foetus was removed using foetotomy. Blood smear examination of the dam and contact smear of the aborted foetus revealed characteristic Maltese cross appearance of B. equi. The possible routes of transmission of parasite, its pathogenesis and future strategies are described in the present article.

Transplacental transmission of Babesia equi (Theileria equi) from carrier mares to foals

This article communicates the first per-acute and fatal clinical report of transplacental transmission of Theileria equi from carrier mothers to foals from Punjab, India. Two cases of equine piroplasmosis due to T. equi were diagnosed in neonatal foals borne to Throughbred mares. High degree of parasitemia with annular and maltese cross shaped parasites in erythrocytes was seen in both cases. Blood cellular changes revealed leucopenia and neutropenia with mild degenerative left shift. Anaemia was macrocytic normochromic type. Intense yellow discoloration of mucous membranes indicated jaundice. In areas endemic for equine piroplasmosis, jaundice in neonatal foal can be easily misdiagnosed as neonatal isoerythrolysis. Foals with post-partum jaundice should always be screened for equine piroplasmosis.