Persistently infected horses are reservoirs for intrastadial tick-borne transmission of the apicomplexan parasite Babesia equi

Detection of tick-borne pathogens in Rhipicephalus bursa ticks collected from the autochthonous Garrano breed of horses in Portugal

The Garrano is a semi-feral horse breed native to several mountains in the northern Iberian Peninsula. Despite being endangered, this unique breed of pony has managed to survive in the wild and continues to be selectively bred, highlighting their remarkable resilience and adaptability to harsh environments. Wildlife plays a critical role in the survival of tick vectors in their natural habitats and the transfer of tick-borne pathogens, as they can serve as reservoir hosts for many agents and amplifiers for these vectors. The semi-feral lifestyle of the Garrano horses makes them particularly vulnerable to exposure to numerous tick species throughout the year. Therefore, the aim of this study was to investigate the occurrence of Anaplasma, Ehrlichia, Babesia, Theileria, and spotted fever rickettsiae in the Garrano horse ticks to obtain a knowledge of circulating agents in this host population. The collected ticks (n = 455) were identified as Rhipicephalus bursa. DNA specimens were organized in pools of 5 ticks, for molecular screening. Pools PCR results confirmed the presence of Candidatus Rickettsia barbariae (n = 12 for the ompB gene, n = 11 for the ompA gene and n = 6 for the gltA gene), Babesia bigemina (n = 1), Babesia caballi (n = 3), Theileria equi (n = 15) and Theileria haneyi (n = 1).These results confirm the circulation of an emerging rickettsial spotted fever group member, Candidatus R. barbariae, in R. bursa ticks. Our findings demonstrated that Candidatus R. barbariae co-circulates with B. bigemina and T. equi, which are vectored by R. bursa. We are reporting for the first time, the detection of T. haneyi among R. bursa ticks feeding in the Garrano horses in Portugal. Surveillance studies for tick-borne infections are essential to provide information that can facilitate the implementation of preventive and control strategies.

Haemato-biochemical characterization of equine piroplasmosis asymptomatic carriers and seropositive, real-time PCR negative horses

Equine piroplasmosis (EP) is caused by Theileria equi and Babesia caballi, transmitted by tick vectors. Horses can suffer an acute, subacute, and chronic forms of the disease, with clinical signs such as poor performance, fever, pale mucosal membranes, and jaundice. The diagnosis of EP subclinical cases is complex due to the sensitivity of real-time PCR and the limited parasite load in some carriers, making it challenging to differentiate them from seropositive, PCR negative (S+PCR-) individuals. This study aimed to describe haematological and biochemical changes in asymptomatic EP carriers, EP S+PCR- horses and control horses (EP seronegative and PCR negative). It also investigated potential haemato-biochemical markers to aid in distinguishing true EP carriers alongside molecular and serological tests. A comprehensive haematology and biochemistry profile was conducted on 410 sera and EDTA blood samples, comprising 130 EP positives by real-time PCR and competitive ELISA (cELISA) (carriers), 130 EP negatives by real-time PCR but positive to cELISA (S+PCR-) and 150 EP negative horses to real-time PCR and c-ELISA (controls). Our study confirmed that a haematological and biochemistry profile could help to differentiate between EP carriers/S+PCR- from healthy horses. Carriers and S+PCR- horses showed significant increases in the white blood cell count (WBC), high total proteins (TP) and total globulins (GLOB) concentration, and liver function markers compared to controls. Additionally, the evaluation of uric acid (UA) suggested oxidative stress in carrier horses. However, no useful haemato-biochemical diagnostic markers were identified to aid the challenging differentiation of EP carriers and S+PCR- horses, highlighting the need for improvement in molecular/serological diagnosis for these horses.

A U.S. Isolate of Theileria orientalis Ikeda Is Not Transstadially Transmitted to Cattle by Rhipicephalus microplus

Theileria orientalis Ikeda has caused an epidemic of bovine anemia and abortion across several U.S. states. This apicomplexan hemoparasite is transmitted by Haemaphysalis longicornis ticks; however, it is unknown if other North American ticks are competent vectors. Since the disease movement is largely determined by the host tick range(s), the prediction of the T. orientalis spread among U.S. cattle populations requires determination of additional competent tick vectors. Although Rhipicephalus microplus has mostly been eradicated from the U.S., outbreaks in populations occur frequently, and the U.S. remains at risk for reintroduction. Since R. microplus is a vector of Theileria equi and T. orientalis DNA has been detected in R. microplus, the goal of this study was to determine whether R. microplus is a competent vector of T. orientalis. Larval R. microplus were applied to a splenectomized, T. orientalis Ikeda-infected calf for parasite acquisition, removed as molted adults, and applied to two T. orientalis naïve, splenectomized calves for transmission. After 60 days, the naïve calves remained negative for T. orientalis by PCR and cytology. Additionally, T. orientalis was not detected in the salivary glands or larval progeny of acquisition-fed adults. These data suggest that R. microplus is not a competent vector of the U.S. T. orientalis Ikeda isolate.

PCR detection of Theileria equi and Babesia caballi in apparently healthy horses in Paraguay

Equine piroplasmosis (EP) is a tick-borne disease caused by Theileria equi and Babesia caballi in equids, including horses. EP has a global distribution and often leads to a significant socioeconomic impact on the equine industry. Infected animals remain as carriers and become a source of infection for tick vectors, thereby posing an immense challenge in the disease management. Therefore, detection of these carriers is crucial to assess the risk of transmission and to implement appropriate control measures in endemic countries. Paraguay is a tropical country where various tick-borne diseases are common among livestock; however, the status of EP remains unknown in this country. Because the tick vectors capable of transmitting T. equi and B. caballi are endemic in Paraguay, we hypothesised that Paraguayan horses are infected with these parasite species. To test our hypothesis, we prepared blood DNA samples from a total of 545 apparently healthy horses in 16 of the 17 departments of Paraguay and analysed them with specific PCR assays to detect T. equi and B. caballi. The PCR results showed that 178 (32.7%) and 8 (1.5%) of the horses were infected with T. equi and B. caballi, respectively. Among the infected horses, two (0.4%) were infected with both parasite species. Our analyses further indicated that the positive rates of T. equi infection did not differ between horse breeds, males and females, or age groups. We also found that haematological parameters were the same between the non-infected animals and animals with single infections. By contrast, the two horses co-infected with T. equi and B. caballi had haemoglobin and haematocrit values lower than the normal ranges. In conclusion, the present study demonstrated that Paraguayan horses are infected with T. equi and B. caballi and that the rate of T. equi infection is higher than that of B. caballi. Our findings highlight the need to add EP to the list of differential diagnoses when anaemic horses are presented to equine clinics in Paraguay.

A risk assessment of equine piroplasmosis entry, exposure and consequences in the UK

BACKGROUND

Equine piroplasmosis (EP) is currently not endemic in the UK, despite a lack of formal surveillance and the presence of carrier horses in the equine population. Pathogen establishment would have significant welfare and economic impacts on the national equine industry, but the disease is often overlooked by UK practitioners.

OBJECTIVES

To assess the risk of disease entry, exposure and consequences to the UK equine population.

STUDY DESIGN

Qualitative risk assessment.

METHODS

A qualitative risk assessment was constructed utilising the current World Organisation for Animal Health (OIE) published framework for importation risk assessment, assessing the key areas of disease entry, exposure and consequences to the UK equine population.

RESULTS

The overall risk of EP entry to the UK via importation of infected equidae with acute disease is very low but considered medium with subclinical carrier animals. Entry via importation of ticks or the importation of blood is considered very low. The risk of EP exposure to susceptible equidae in the UK is considered low by the infection routes of tick-bites, contaminated needles and contaminated blood, but very high via transplacental transfer. However, the consequences of EP endemic establishment are considered of high significance to the UK equine industry.

MAIN LIMITATIONS

A lack of available numerical data for events and variables in disease import risk meant a qualitative assessment was the most practical method for this scenario.

CONCLUSIONS

This risk assessment highlights that EP positive animals are able to enter and are currently present in the UK, and that conditions do exist that could allow forward transmission of the disease. It has highlighted a gap in existing policy where the UK falls behind OIE guidelines and has suggested steps to correct this discrepancy and improve national biosecurity.

Molecular epidemiology of Theileria species in ticks and its potential threat to livestock in the Republic of Korea

The purpose of this study was to investigate molecular epidemiology of Theileria spp. in ticks in Korea and assess their potential threat from wildlife animals to domestic animals. A total of 21152 hard ticks were collected from Chungcheong and Jeolla provinces of Korea from March to October 2021. Tick species were identified by microscopy and Theileria spp. were screened by nested PCR targeting 18S rRNA. Haemaphysalis spp. were the most abundant tick species, followed by H. longicornis, H. flava, Amblyomma testudinarium, and Ixodes nipponensis. Of the collected ticks, 6914 ticks (541 pools) were screened, and PCR showed 211 positive pools (39.0%; MIR: 3.05). The PCR and phylogenetic analysis identified two Theileria species, T. luwenshuni and Theileria sp., with T. luwenshuni (162/211, 76.78%; MIR: 2.34) being more abundant than Theileria sp. (36/211, 17.06%; MIR: 0.52); co-infection of the two species were noted (13/211, 6.16%; MIR: 0.19). Among the tick species, H. longicornis, especially nymphs, showed the highest prevalence. Regarding season, the highest prevalence was observed in May. Considering the tick and Theileria species identified in this study, H. longicornis nymph and cervine play a critical role in maintaining Theileria spp. in Korea and could be a potential threat to domestic animals, including deer and goats. In addition, there are significant correlations among tick distribution, region, season, and prevalence of Theileria.

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.

Novel equi merozoite antigen (ema-1) gene heterogeneity in a geographically isolated Theileria equi population in Croatia

BACKGROUND

The apicomplexan haemoparasite Theileria equi, a causative agent of equine piroplasmosis, is an established pathogen of significant welfare and economic concern within the Croatian equine population. A previous large surveillance study of T. equi has identified two distinct parasite populations, one in the north and one in the south, geographically separated by the Dinaric Alps, which traverse the country. This study aimed to further investigate the genetic diversity within these two populations, focussing on allelic variability of the equi merozoite antigen gene, ema-1.

METHODS

Following nested PCR of DNA isolates, the generated ema-1 amplicons were subsequently sequenced and compared by phylogenetic analysis to available sequences representing previously described ema-1 genotypes (groups A-C).

RESULTS

Isolates from the southern T. equi population clustered with the existing ema-1 groups A and B. Strikingly, isolates from the northern population clustered into two novel ema-1 genotypes, named groups D and E.

CONCLUSIONS

This detection of hitherto unreported genotypes suggests that historic geographical isolation has led to a degree of divergent evolution in this northern T. equi population. Additionally, current global regulatory testing of equine piroplasmosis relies heavily on EMA-1 based immunodiagnostics, and the discovery of unique ema-1 genotypes may question the efficacy of current diagnostics in international equine movement, with ramifications for the global equine community.

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.

Serological and molecular detection of Babesia caballi and Theileria equi in Mexico: A prospective study

Equine piroplasmosis is a disease of horses, mules and donkeys, caused by the hemoprotozoans Babesia caballi and Theileria equi and transmitted by ticks of tropical and subtropical regions. Because the clinical signs are not specific, the diagnosis of equine piroplasmosis is difficult. In Mexico, where the environmental factors are conducive to the persistence of these pathogens, there is a lack of molecular studies to evaluate the occurrence of both parasites in horses. In the present study, matching serum and whole blood samples were obtained from 269 horses residing in 24 locations with tropical or subtropical climate and the presence of ticks. Testing of serum samples by ELISA demonstrated 55.7% seroprevalence of B. caballi and 68.4% prevalence of antibodies to T. equi. Blood samples analyzed with nPCR test were 7.8% positive to B. caballi and 78.8% positive to T. equi, while a duplex qPCR showed 15.24% positive samples to B. caballi and 59.11% to T. equi. From these results, 27 samples were sequenced for T. equi and 13 for B. caballi, confirming the presence of both horse parasites that cause equine piroplasmosis and suggesting that they are widespread in Mexico. This is the first study confirming the presence of B. caballi and T. equi in Mexico using both serological and molecular diagnostic methods. This study shows a high incidence of exposure to the etiological agents of equine piroplasmosis in horses in the studied areas.

Isolation of infectious Theileria parva sporozoites secreted by infected Rhipicephalus appendiculatus ticks into an in vitro tick feeding system

Background

Vector-borne diseases pose an increasing threat to global food security. Vaccines, diagnostic tests, and therapeutics are urgently needed for tick-borne diseases that affect livestock. However, the inability to obtain significant quantities of pathogen stages derived from ticks has hindered research. In vitro methods to isolate pathogens from infected tick vectors are paramount to advance transcriptomic, proteomic, and biochemical characterizations of tick-borne pathogens.

Methods

Nymphs of Rhipicephalus appendiculatus were infected with Theileria parva by feeding on a calf during an acute infection. Isolation of sporozoites was accomplished by feeding infected adult ticks on an in vitro tick feeding system. Sporozoite viability was tested using in vitro bovine lymphocytes.

Results

We isolated infectious T. parva sporozoites secreted into an in vitro tick feeding system. Infected adult R. appendiculatus ticks attached to and successfully fed on silicone membranes in the in vitro tick feeding system. Bovine blood in the receptacle was replaced with cell-free medium and the ticks were allowed to feed for 3 h to collect secreted T. parva sporozoites. Secreted sporozoites infected in vitro bovine lymphocytes, demonstrating that isolated sporozoites remained viable and infectious.

Conclusions

This work is the first to report the isolation of mature infectious T. parva sporozoites using an in vitro tick feeding system, which represents a significant step towards the development of a more efficient control strategy for T. parva. Isolation of infectious tick-stage parasites will facilitate the examination of the vector-pathogen interface, thereby accelerating the development of next-generation vaccines and treatment interventions for tick-borne pathogens.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05120-7.

Rapid Detection of Equine Piroplasms Using Multiplex PCR and First Genetic Characterization of Theileria haneyi in Egypt

Equine Piroplasmosis (EP) is an infectious disease caused by the hemoprotozoan parasites Theileria equi, Babesia caballi, and the recently identified species T. haneyi. Hereby, we used a multiplex PCR (mPCR) targeting the 18S rRNA gene of T. equi and B. caballi for the simultaneous detection of EP in Egyptian equids and examined the presence of T. haneyi infections in Egypt. Blood samples from 155 equids (79 horses and 76 donkeys) collected from different governorates of Egypt were examined by mPCR and PCR targeting T. hayeni. The mPCR method revealed a prevalence of T. equi of 20.3% in horses and of 13.1% in donkeys and a prevalence of B. caballi of 1.2% in horses. B. caballi was not detected in donkeys in the current study. The mPCR method also detected coinfections with both species (2.5% and 1.3% in horses and donkeys, respectively). Additionally, we report the presence of T. haneyi in Egypt for the first time in 53.1% of the horse and 38.1% of the donkey tested samples. Coinfection with T. haneyi and T. equi was found in 13.5% of the samples, while infection with the three EP species was found in 1.9% of the samples.

Molecular Identification of Selected Tick-Borne Protozoan and Bacterial Pathogens in Thoroughbred Racehorses in Cavite, Philippines

Tick-borne diseases (TBDs) considerably impair equine health and productivity. Moreover, TBDs, particularly equine piroplasmosis, impede international movement and trade of equids, which is a vital component of the global horse racing industry. In the Philippines, horse racing is a lucrative industry generating millions of USD annually. However, information on equine TBDs is scarce. This study intended to describe molecularly the equine tick-borne infections in a racehorse park in Cavite, Philippines and identify the risk factors associated with the infections. One hundred twenty-four (n = 124) thoroughbred racehorses were sampled and screened for selected tick-borne protozoan and bacterial pathogens using polymerase chain reaction (PCR) assays. Racehorses were positive for Babesia caballi (12.10%; 15/124), Theileria equi (0.81%; 1/124), Anaplasma phagocytophilum (10.48%; 13/124), Borrelia burgdorferi sensu lato (38.71%; 48/124), A. marginale (0.81%; 1/124), and Coxiella burnetii (0.81%; 1/124). Rickettsia was not detected in the samples. Gender was determined as a significant risk factor for B. caballi infection. Sequencing analysis revealed that seven partial 18S rRNA B. caballi isolates shared 98.63–100% identity with each other and were classified as genotype A. Meanwhile, the sequence obtained from the lone T. equi-positive sample was 99.77% identical to isolates from Spain, Switzerland, China, Saudi Arabia, and South Korea, and was confirmed as genotype E based on the 18S rRNA gene. Eight Anaplasma 16S rRNA partial sequences were highly identical to A. phagocytophilum and A. ovis. Partial sequences of Borrelia 5–23S rRNA were most closely related to B. japonica and other Borrelia sp. isolates from various countries. This study reports the first molecular detection of Borrelia and Anaplasma and the identification of B. caballi and T. equi genotypes in racehorses in the Philippines. Findings from this study shall be useful in crafting equine tick and TBD control and prevention programs in the country.

Molecular Detection and Phylogenetic Analysis of Tick-Borne Pathogens in Ticks Collected from Horses in the Republic of Korea

The horse industry has grown rapidly as a leisure industry in the Republic of Korea (ROK) in parallel with an increased demand for equestrian activities. As a result, there has been an increase in horse breeding and equestrian population and potential exposure to ticks and their associated pathogens. To provide a better understanding of the potential disease risks of veterinary and medical importance, a study was conducted to determine the geographical distribution and diversity of ticks collected from horses and vegetation associated with horse racetracks/ranches throughout the ROK. This included a survey of five associated common pathogens, Anaplasma phagocytophilum, Ehrlichia chaffeensis, Borrelia spp., Babesia caballi, and Theileria equi. A total 9220 ticks were collected from horses and associated pastures. Ticks were identified to species, stage of development, and sex. Two species of ticks, Haemaphysalis longicornis (99.9%) and Ixodes nipponensis (0.1%) were identified. Two of the target pathogens, A. phagocytophilum and Borrelia spp., were detected in 5/1409 tick pools (0.35%) and 4/1409 pools (0.28%) of H. longicornis, respectively, both of which are zoonotic pathogens of medical importance. The results of 16S rRNA phylogenetic analysis of A. phagocytophilum showed a close relationship to strains distributed in China, USA, Germany, Italy, Turkey, and Poland. Borrelia spp. showed a close relationship, based on 16S rRNA gene, to the strains reported from the USA (B. burgdorferi and B. americana) and Japan (B. tanukii and B. garinii). These results provide information about the potential risks of veterinary and medical importance and the development of mitigation strategies for disease prevention.

Immune response of adult horses, pregnant mares and foals to an experimental vaccine with recombinant EMA-2 protein of Theileria equi

Equine theileriosis, caused by the Theileria equi protozoan, is a disease of worldwide importance. T. equi expresses surface proteins, of which the EMA-2 protein is a promising antigen for vaccine use. The aim of this study was to evaluate the immune response of adult horses, pregnant mares, and foals to an experimental EMA-2 protein of recombinant T. equi vaccine. A total of 46 horses were used in this study for vaccine trials and challenges. Twelve geldings, 14 pregnant mares, and 14 foals were divided into vaccinated and control groups. Total serum specific anti-rEMA-2 IgG, IgG subclasses, and transcription of cytokines related to the immune response were evaluated. For the vaccine challenge, six six-month-old foals were divided into vaccinated and control groups. For the challenge, blood from a horse with theileriosis was transfused to the foals. Geldings and pregnant mares maintained anti-rEMA-2 IgG levels at 130 and 140 days after vaccination, respectively. The most-detected IgG subclasses in vaccinated were IgG3/5, IgG4/7, and IgG1. IL2, IL10, IL12, IL17, IFN-γ, and TNF-α were the most-transcribed cytokines in PBMCs of vaccinated horses stimulated with rEMA-2. Challenge with T. equi demonstrated that vaccinated foals had an increase of 33% in total IgG four days after blood transfusion, while control foals had no significant response, suggesting that vaccine antibodies may have recognized EMA-2 protein of the native T. equi antigen. T. equi recombinant EMA-2 was shown to be a promising vaccine antigen by inducing humoral and cellular immunity similar to that observed in natural parasite infections.

A survey on equine tick-borne diseases: The molecular detection of Babesia ovis DNA in Turkish racehorses

Common vector-borne diseases of horses include equine piroplasmosis (EP) caused by Babesia caballi and Theileria equi, and equine granulocytic anaplasmosis (EGA) caused by Anaplasma phagocytophilum. Equine piroplasmosis leads to severe health issues in horses and restrictions on the movement of horses internationally. Anaplasma phagocytophilum causes an acute febrile illness in horses and is also of zoonotic importance. In the present study, blood samples were collected from 152 Turkish racehorses from three different provinces (İzmir, Gaziantep, and Konya) of Turkey to investigate the prevalence of EP and EGA. Standard and nested polymerase chain reactions were performed to identify equine piroplasms and A. phagocytophilum, respectively. PCR primers targeting Babesia spp. 18S rRNA, B. caballi BC48, T. equi EMA-1, and A. phagocytophilum 16S rRNA genes were used for molecular diagnosis. Following the cloning and subsequent sequencing of PCR-positive samples, a total of 15 (9.9%) horses were found to be infected with at least one pathogen. Theileria equi and A. phagocytophilum were found in 3.3% (5/152) and 6.6% (10/152) of the samples, respectively. Although B. caballi specimens were not detected in any of the samples, a positive signal was detected for the Babesia genus-specific 18S rRNA PCR. Subsequent sequencing of this signal revealed 100% identity to Babesia ovis. This is the first detection of B. ovis DNA in racehorses in Turkey to the best of our knowledge. Additionally, this study also reports the first molecular identification of A. phagocytophilum in Turkish racehorses. Based on this report, it is recommended that future epidemiological studies on horses also take B. ovis, a parasite usually found in sheep, into consideration and that further detailed studies be conducted to unravel the transmission pathways and potential clinical effects of B. ovis in horses.

Theileria equi claudin like apicomplexan microneme protein contains neutralization-sensitive epitopes and interacts with components of the equine erythrocyte membrane skeleton

Theileria equi is a widely distributed apicomplexan parasite that causes severe hemolytic anemia in equid species. There is currently no effective vaccine for control of the parasite and understanding the mechanism that T. equi utilizes to invade host cells may be crucial for vaccine development. Unlike most apicomplexan species studied to date, the role of micronemes in T. equi invasion of host cells is unknown. We therefore assessed the role of the T. equi claudin-like apicomplexan microneme protein (CLAMP) in the invasion of equine erythrocytes as a first step towards understanding the role of this organelle in the parasite. Our findings show that CLAMP is expressed in the merozoite and intra-erythrocytic developmental stages of T. equi and in vitro neutralization experiments suggest that the protein is involved in erythrocyte invasion. Proteomic analyses indicate that CLAMP interacts with the equine erythrocyte α-and β- spectrin chains in the initial stages of T. equi invasion and maintains these interactions while also associating with the anion-exchange protein, tropomyosin 3, band 4.1 and cytoplasmic actin 1 after invasion. Additionally, serological analyses show that T. equi-infected horses mount robust antibody responses against CLAMP indicating that the protein is immunogenic and therefore represents a potential vaccine candidate.

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.

Stray Mexico origin cattle captured crossing into Southern Texas carry Babesia bovis and other tick-borne pathogens

Cattle fever ticks, Rhipicephalus microplus and R. annulatus have been eradicated from the United States and inspectors from the U.S. Department of Agriculture (USDA), Animal Plant Health Inspection Service (APHIS), Cattle Fever Tick Eradication Program (CFTEP) monitor the quarantine zone along the Texas border to prevent the introduction of livestock carrying cattle fever ticks from Mexico. Stray livestock apprehended by CFTEP in the zone are checked for ticks and tested for infectious disease-causing pathogens but are not evaluated for evidence of infection with tick-borne pathogens. We tested blood samples collected from stray cattle by CFTEP inspectors for evidence of infection with tick-borne pathogens. As a comparison group representing U.S. resident cattle, we tested blood samples that had been sent to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) for unrelated testing. Both sets of blood samples were evaluated using the same specific and broad-spectrum PCR assays. For the border cattle the overall prevalence of infection with one or more tick-borne pathogen was 58.5 % (79/135) with many co-infections, including 30 cattle positive for Babesia bovis and/or Babesia bigemina (22.2 %) and 77 cattle positive for Anaplasma marginale (57 %), three of these animals were also positive for Borrelia theileri. No resident cattle represented by the TVMDL samples were infected with either of the Babesia spp., or with Borrelia theileri, but three were positive for Theileria orientalis and 7.3 % (7/96) were positive for A. marginale. These data show that cattle originating in Mexico have a higher prevalence of infection with tick-borne pathogens relative to resident U.S. cattle and specifically, a proportion are infected with bovine Babesia, which is absent from U.S. cattle populations. Consequently, these stray cattle may be a reservoir of tick-borne pathogens and if populations of Boophilus ticks become reestablished in areas where they had previously been eradicated, could pose a significant risk to the U.S. Cattle industry.

First Case of Autochthonous Equine Theileriosis in Austria

A 23-year-old pregnant warmblood mare from Güssing, Eastern Austria, presented with apathy, anemia, fever, tachycardia and tachypnoea, and a severely elevated serum amyloid A concentration. The horse had a poor body condition and showed thoracic and pericardial effusions, and later dependent edema and icteric mucous membranes. Blood smear and molecular analyses revealed an infection with Theileria equi. Upon treatment with imidocarb diproprionate, the mare improved clinically, parasites were undetectable in blood smears, and 19 days after hospitalization the horse was discharged from hospital. However, 89 days after first hospitalization, the mare again presented to the hospital with an abortion, and the spleen of the aborted fetus was also PCR-positive for T. equi. On the pasture, where the horse had grazed, different developmental stages of Dermacentor reticulatus ticks were collected and subjected to PCR, and one engorged specimen was positive for T. equi. All three amplicon sequences were identical (T. equi genotype E). It is suspected that T. equi may repeatedly be transmitted in the area where the infected mare had grazed, and it could be shown that transmission to the fetus had occurred. Due to the chronic nature of equine theileriosis and the possible health implications of infection, it is advised to include this disease in the panel of differential diagnoses in horses with relevant clinical signs, including horses without travel disease, and to be aware of iatrogenic transmission from inapparent carrier animals.

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.

Imidocarb Dipropionate Lacks Efficacy against Theileria haneyi and Fails to Consistently Clear Theileria equi in Horses Co-Infected with T. haneyi

Control of Theileria equi, the primary cause of equine theileriosis, is largely reliant on acaracide use and chemosterilization with imidocarb dipropionate (ID). However, it is currently unknown if ID is effective against Theileria haneyi, the recently identified second causative agent of equine theileriosis, or if the drug maintains effectiveness against T. equi in the presence of T. haneyi co-infection. The purpose of this study was to address these questions using ID treatment of the following three groups of horses: (1) five T. haneyi infected horses; (2) three T. haneyi-T. equi infected horses; and (3) three T. equi-T. haneyi infected horses. Clearance was first evaluated using nPCR for each Theileria sp. on peripheral blood samples. ID failed to clear T. haneyi in all three groups of horses, and failed to clear T. equi in two of three horses in group two. For definitive confirmation of infection status, horses in groups two and three underwent splenectomy post-treatment. The T. equi-nPCR-positive horses in group two developed severe clinical signs and were euthanized. Remaining horses exhibited moderate signs consistent with T. haneyi. Our results demonstrate that ID therapy lacks efficacy against T. haneyi, and T. haneyi-T. equi co-infection may interfere with ID clearance of T. equi.

Molecular diagnosis and biochemical studies of tick-borne diseases (anaplasmosis and babesiosis) in Aberdeen Angus Cattle in New Valley, Egypt

Background and Aim:

Anaplasmosis and babesiosis are tick-borne diseases that threaten livestock production with subsequent considerable economic losses. This study was conducted to diagnose Anaplasma and Babesia infection using molecular techniques in imported Aberdeen Angus cattle imported from Uruguay to El-Kharga Oasis in New Valley, Egypt, and to investigate the effects of disease on some serum biochemical and oxidative stress parameters.

Materials and Methods:

Blood samples were collected from 31 cattle, 21 diseased and ten apparently normal, of varying ages and sex. The blood was used for the preparation of blood smears, polymerase chain reaction assay, and separation of serum for biochemical investigation. The experimental production farm at the Faculty of Agriculture, New Valley University, was infested with ticks and variable clinical manifestations during the period from December 2017 to March 2018. One calf died of a suspected blood parasite infection.

Results:

The blood film examination revealed infection by blood parasites in 21 samples. Anaplasma marginale and Babesia bovis were identified in 12 and 14 samples, respectively. A total of 14 samples were examined by polymerase chain reaction (PCR) to make these identifications. Biochemical parameters showed significantly elevated serum alanine aminotransferase, aspartate aminotransferase, total bilirubin (T. Bil), and urea in blood from parasite-infected female cattle and male calves compared with controls. Increased serum total protein, globulin, and creatinine were recorded only in infected female cattle. The blood glucose level was significantly decreased in infected female cattle and male calves compared with controls. Furthermore, albumin and albumin/globulin ratio was significantly reduced in the infected female cattle. Oxidative stress profiles of infected animals showed a significant increase in serum nitric oxide and malondialdehyde, and both total antioxidant capacity and reduced glutathione (GSH) were significantly reduced in comparison with control animals.

Conclusion:

The incidence of A. marginale and B. bovis infection is high in imported Aberdeen Angus cattle in New Valley Province. PCR methods provide a short-term assessment of disease. An extensive epidemiological survey, employing serology together with molecular genetic methods, monitoring of abundance and distribution of tick vectors, availability of vaccination programs, and tracking of animal transport is also needed for control of blood parasites.

First report of genetic diversity and risk factor analysis of equine piroplasm infection in equids in Jilin, China

Background

Equine piroplasmosis (EP) is a tick-borne hemoprotozoan disease of equids, caused by Theileria equi and Babesia caballi. Equine piroplasmosis represents a serious challenge to the equine industry due to important economic losses worldwide. The present study aimed to evaluate the prevalence of Theileria equi and Babesia caballi infections in equids from Jilin Province, China.

Methods

A total of 220 blood samples (192 horses and 28 donkeys/mules) were collected from March 2018 to October 2019 in five districts of Jilin Province and analyzed by PCR. Potential risk factors, including the region, sex, management, and host species of the animals were assessed in relation to T. equi infection. Moreover, the V4 hypervariable region of the T. equi 18S rRNA gene was analyzed to identify specific genotypes.

Results

The overall prevalence of T. equi in equids was 27.7%, whereas B. caballi infection was not identified. The district with the highest positive rate was Baicheng (43.3%), followed by Tonghua (28.9%), Yanbian (26.4%), Jilin (23.3%), and Liaoyuan (20.9%). The sex of the animals and farm management were identified as main risk factors, which were significantly associated with the prevalence of Equine piroplasmosis (P < 0.05). The risk factor analysis indicated that the females were at a higher risk (OR: 2.48, 95% CI: 1.17–5.27) of being infected compared to the males, whereas the organized farm was protective factor (OR: 0.42, 95% CI: 0.22–0.80). The phylogenetic analyses revealed that there were two T. equi genotypes (A and E) in Jilin.

Conclusions

Our findings provided important epidemiological data for the prevention and control of T. equi infection in Jilin, China.

Investigating the presence of equine piroplasmosis in Ireland

BACKGROUND

Equine piroplasmosis (EP) is a notifiable disease in Ireland and a significant concern to domestic and international equine industries. Information regarding EP presence in Ireland is currently limited. This retrospective surveillance study describes a serological and molecular analysis of blood samples submitted to the Irish Equine Centre for EP testing between January 2013 and April 2016.

METHODS

Following serological testing, seropositive samples were screened using a PCR targeting the 18S ribosomal RNA gene. Amplicon sequences were bioinformatically analysed to identify the parasite species and to assess genetic diversity.

RESULTS

From 2099 screened equine blood samples, 2.5 per cent and 1 per cent were seropositive for Theileria equi and Babesia caballi, respectively. T equi DNA was detected in 9 per cent of the seropositive samples while B caballi DNA was not detected in any sample. The T equi DNA sequences displayed no genetic diversity at this locus, in contrast to samples from the UK and from endemic areas.

CONCLUSION

Detection of EP-seropositive and parasitaemic horses in Ireland indicates a clear and present health risk to the equine population. It is recommended that owners adopt appropriate biosecurity measures and that clinicians are mindful of this disease as a differential diagnosis.

Molecular detection of Theileria species and Babesia caballi from horses in Nigeria

Equine piroplasmosis (EP) is an infectious, tick-borne disease caused by the hemoprotozoan parasites, Theileria equi, Babesia caballi, and a recently reported new species, T. haneyi. Infections by these apicomplexan parasites limit performance and cause economic losses for the horse industry. Equine piroplasmosis is widespread in the northern regions of Nigeria, where an increasing portion of the animal population is composed of horses. This disease has remained epidemiologically challenging, especially as the movement of horses increases across Nigeria. In this study, blood samples from 300 horses were collected in three states of northwestern Nigeria. The presence of piroplasms was screened by nested PCR targeting 18S rDNA and positive samples were analyzed using species-specific-nested PCR-targeting genes including ema1 (T. equi), rap1 (B. caballi), and a gene coding a protein of unknown function (T. haneyi). Species-specific-nPCR results demonstrated that the prevalence of T. equi was 13.0% (39/300), B. caballi was 3.3% (10/300) and T. haneyi was 2.7% (8/300). Mixed infections with T. equi and B. caballi was 2.7% (8/300) while T. equi, B. caballi, and T. haneyi multiple infection prevalence was 0.6% (2/300). We used 18S rDNA sequences to determine close relationships between T. equi by phylogenetic analysis and demonstrated that among 57 sequences of Theileria parasites, 28 samples belonged to clade A (49%), 13 samples were found to be clade C (22%), and 16 were clade D (28%). These results demonstrate the genetic diversity of T. equi circulating in horses from Nigeria.

Natural Theileria equi infection in captive Tapirus terrestris (Perissodactyla: Tapiridae) in the Brazilian Amazon

The objective of this study was to detect natural Theileria equi infection in captive tapirs (Tapirus terrestris) in the Brazilian Amazon. Samples from 19 captive tapirs were collected from zoological and botanical gardens and conservation parks in the Pará (n = 18) and Amazonas (n = 1) states. Whole-blood samples were collected for subsequent screening of T. equi DNA by PCR using the BEC-UF2 and EQUI-R primer set. Microscopic analyses of blood smears revealed T. equi trophozoites in 37% (7/19) of the animals examined, and T. equi DNA was detected in 58% (11/19) of the blood samples analyzed. Sequencing of amplified PCR products revealed an identity with T. equi isolates obtained from horses and waterbuck available in GenBank. In conclusion, T. equi infection occurs in captive tapirs in the Brazilian Amazon, and these mammals could potentially act as reservoirs.

Quantitative analysis of Anaplasma marginale acquisition and transmission by Dermacentor andersoni fed in vitro

In this study, we describe a new in vitro tick feeding system that facilitates the study of ticks and tick-borne pathogens. To optimize the system, we used Dermacentor andersoni and Anaplasma marginale as a tick-pathogen interaction model. Ticks were fed on bovine blood containing 10-fold dilutions of the pathogen to determine the effect of dose on tick infection rate. After feeding on infected blood, ticks were transferred to uninfected blood to stimulate bacterial replication within the tick vector. During stimulation feeding, blood samples were collected daily to determine if infected ticks secreted viable A. marginale. The results demonstrated similar attachment rates between the first and second tick feeding. Tick midgut and salivary glands were infected with A. marginale. However, salivary gland infection rates decreased as the percentage of parasitized erythrocytes decreased during tick acquisition feeding. Bacteria recovered from the in vitro system were able to infect a naïve bovine host. Using the highly transmissible A. marginale St. Maries strain, we demonstrated that the artificial tick feeding system is a suitable tool to study tick-pathogen interactions and that A. marginale tick salivary gland infection is dose dependent. This work demonstrates the utility of an artificial tick feeding system to directly study the association between the number of acquired pathogens and transmissibility by ticks.

Antigenicity assessment of the Theileria equi merozoite antigen (EMA-2) expressed in Pichia pastoris in mice and horses

Equine theileriosis is a severe equine disease caused by the protozoan Theileria equi, which is prevalent in tropical and subtropical areas. In this study, a recombinant equi merozoite antigen-2 (rEMA-2) of T. equi was used as an immunogen. Two groups of 10 mice each were divided into control and vaccinated groups. Sixty mares seronegative for theileriosis were divided in two groups, one vaccinated and another group as a control animal. Mice and mares of the vaccinated groups were inoculated with 150 μL of the vaccine containing 50 μg of rEMA-2 and 2 mL of the vaccine containing 200 μg of rEMA-2, respectively, at days 0 and 21. The immunogenicity of rEMA-2 was evaluated by ELISA and fluorescent antibody test (IFAT) using serum from vaccinated mice, mares and antigenicity in naturally infected horse. At every point throughout the ELISA study, there were significant differences between the vaccinated and control groups (p < 0.05). The vaccine induced 3- and 4-fold IgG increases in mice at the 14th and 28th day, respectively, compared to the control group. The horses' IgG dynamics showed a significant (p < 0.05) increase in the total IgG titer as early as day 7, which increased until day 28 at which time a more significant (p < 0.001) IgG titer was observed. In evaluating the isotypes, we observed a trend similar to that of total IgG, where IgG(T) (IgG3-5) were significantly (p < 0.05) more elevated than the other isotypes analyzed, followed by IgGb (IgG4-7) and IgGa (IgG1). Positive fluorescence was detected by IFAT, suggesting that the protein is immunogenic and conserves some epitopes identical to the native T. equi antigens present in the equine blood smear. Thus, our results suggest that rEMA-2 can be a promising vaccinal antigen.

Infection dynamics of Theileria equi and Theileria haneyi, a newly discovered apicomplexan of the horse

Theileria equi infection, exotic to the United States has reemerged through intravenous (iatrogenic) and tick-borne transmission. Surveillance at the US-Mexico border identified a new species, Theileria haneyi, (T. haneyi^EP) (EP = Eagle Pass, Texas) which warranted additional investigation due to inability to detect by PCR targeting of T. equi ema-1 and EMA-1-cELISA validated for T. equi. Infection dynamics of T. haneyi^EP were evaluated, including ability to superinfect in the presence of T. equi-Texas (T. equi^TX), the isolate responsible for the reemergence of T. equi in the U S. Experimental infection with T. equi^TX or T. haneyi^EP revealed minimal clinical disease however, T. equi^TX infection led to significantly greater neutropenia. Comparison of time to antibody detection following inoculation revealed significantly greater time to detectable anti-T. haneyi^EP antibody (26.67 days post-inoculation (DPI)) than T. equi^TX (11.67 DPI). Regardless of initial infection with either T. equi^TX or T. haneyi^EP, superinfection was established. Comparative analysis of antibody responses from a splenectomized horse infected with T. haneyi^EP to that of a spleen intact horse infected with T. equi^FL revealed a different antibody binding profile to T. haneyi^EP, T. equi^TX and T. equi^FL merozoite antigen and limited shared antigen/cross-reactive antibody(s). Affinity purified T. equi EMA-1 and EMA-2 from T. equi^FL were shown as targets for horse antibodies against T. haneyi. Data presented here show (1) T. haneyi^EP can superinfect in the presence of T. equi^TX infection and co-persists for minimally 25 months, (2) intravenous challenge with T. haneyi is subclinical, and (3) limited cross-reactive antibody between T. haneyi^EP and T. equi includes reactivity to EMA-1 and EMA-2.

A Review on Equine Piroplasmosis: Epidemiology, Vector Ecology, Risk Factors, Host Immunity, Diagnosis and Control

Equine Piroplasmosis (EP) is a tick-borne disease caused by apicomplexan protozoan parasites, Babesia caballi and Theileria equi. The disease is responsible for serious economic losses to the equine industry. It principally affects donkeys, horses, mules, and zebra but DNA of the parasites has also been detected in dogs and camels raising doubt about their host specificity. The disease is endemic in tropical and temperate regions of the world where the competent tick vectors are prevalent. Infected equids remain carrier for life with T. equi infection, whilst, infection with B. caballi is cleared within a few years. This review focuses on all aspects of the disease from the historical overview, biology of the parasite, epidemiology of the disease (specifically highlighting other non-equine hosts, such as dogs and camels), vector, clinical manifestations, risk factors, immunology, genetic diversity, diagnosis, treatment, and prevention.

Inhibitory effects of Syzygium aromaticum and Camellia sinensis methanolic extracts on the growth of Babesia and Theileria parasites

Currently, chemotherapeutics against piroplasmosis are also associated with toxicity and the emergence of drug-resistant parasites. Therefore, the discovery of new drug compounds is necessary for the effective control of bovine and equine piroplasms. Syzygium aromaticum (clove) and Camellia sinensis (green tea) have several documented medicinal properties. In the present study, the growth-inhibiting effects of S. aromaticum and C. sinensis methanolic extracts were evaluated in vitro and in vivo. The half-maximal inhibitory concentration (IC₅₀) values for methanolic S. aromaticum against Babesia bovis, B. bigemina, B. divergens, B. caballi, and Theileria equi were 109.8 ± 3.8, 8.7 ± 0.09, 76.4 ± 4.5, 19.6 ± 2.2, and 60 ± 7.3 μg/ml, respectively. Methanolic C. sinensis exhibited IC₅₀ values of 114 ± 6.1, 71.3 ± 3.7, 35.9 ± 6.8, 32.7 ± 20.3, and 60.8 ± 7.9 μg/ml against B. bovis, B. bigemina, B. divergens, B. caballi, and T. equi, respectively. The toxicity assay on Madin-Darby bovine kidney (MDBK), mouse embryonic fibroblast (NIH/3T3), and human foreskin fibroblast (HFF) cell lines showed that methanolic S. aromaticum and methanolic C. sinensis affected only the viability of the MDBK cell line with half-maximal effective concentrations (EC₅₀) of 894.7 ± 4.9 and 473.7 ± 7.4 μg/ml, respectively, while the viability of NIH/3T3 and HFF cell lines was not affected even at 1000 μg/ml. In the in vivo experiment, methanolic S. aromaticum and methanolic C. sinensis oral treatments at 150 mg/kg inhibited the growth of Babesia microti in mice by 69.2% and 42.4%, respectively. These findings suggest that methanolic S. aromaticum and methanolic C. sinensis extracts have the potential as alternative remedies for treating piroplasmosis.

Molecular detection of Rickettsia spp., Anaplasma platys and Theileria equi in ticks collected from horses in Tayrona National Park, Colombia

Horses are among the domestic animals that closely interact with humans and are highly parasitized by ticks, which are the primary vectors of zoonoses. As horses in Tayrona National Natural Park (PNNT) are used as a means of transporting goods, luggage and people, they are in constant contact with wild animals, workers and tourists from different countries. These factors increase the transmission risk of hemoparasites. The purpose of this study was to determine the presence of Rickettsia sp., Anaplasma sp., and Theileria sp., in horse ticks in this protected area using conventional PCR. We collected 343 ticks of genera Amblyomma, Rhipicephalus and Dermacentor. Of the 61 samples analyzed by PCR, 18 (29.5%) individuals were positive for Rickettsia sp., 15 (24.5%) for Anaplasma sp. and 4 (6.6%) for Theileria sp. This is the first report of these hemoparasite genera in ticks associated with horses in this preserved natural area, demonstrating the importance of additional studies on the presence and epidemiology of hemoparasites and their vectors in domestic and wild animals in conserved areas with a high flow of tourists.

Molecular and serological detection of Theileria equi, Babesia caballi and Anaplasma phagocytophilum in horses and ticks in Maranhão, Brazil

ABSTRACT: Equine piroplasmosis is a tick-borne disease caused by the intraeytrhocytic protozoans Babesia caballi and Theileria equi. It has been reported as a main equine parasitic disease. In addition, Anaplasma phagocytophilum, the causative agent of granulocytic ehrlichiosis, causes a seasonal disease in horses. Both diseases, can be detrimental to animal health. In this sense, blood samples and ticks were collected from 97 horses raised in the microregion of Baixada Maranhense, Maranhão State, Brazil. Serum samples were subjected to Indirect Fluorescence Antibody Test (IFAT) and blood samples and ticks to Polymerase Chain Reaction (PCR) to evaluate the infection by Theileria equi, Babesia caballi and Anaplasma phagocytophilum. The overall seroprevalence was 38.14%, 18.55% and 11.34% for T. equi, B. caballi and A. phagocytophilum, respectively. The results of PCR from blood samples showed 13.40% and 3.09% positive samples to T. equi and B. caballi, respectively. A total of 170 tick specimens were collected and identified as Dermacentor nitens, Amblyomma cajennense sensu lato and Rhipicephalus (Boophilus) microplus. It was detected 2.35% (4/170) and 0.59% (1/170) positive tick samples by PCR for T. equi and B. caballi, respectively. All samples were negative to A. phagocytophilum. No statically difference (p>0.05) was observed when gender, age, use of ectoparasiticide and tick presence were analyzed. A BLASTn analysis of the sequenced samples indicated 97 to 100% similarity with T. equi 18S rRNA gene sequences in GenBank and 98 to 100% with B. caballi. Genetic analysis classified the obtained sequences as T. equi and B. caballi cluster, respectively. It can be concluded that these pathogens occur and are circulating in the studied area.

Ticks and Tick-Borne Pathogens of the Caribbean: Current Understanding and Future Directions for More Comprehensive Surveillance

Ticks are obligate hematophagous arthropods of significant importance to human and veterinary medicine. They transmit a vast array of pathogens, including bacteria, viruses, protozoa, and helminths. Most epidemiological data on ticks and tick-borne pathogens (TBPs) in the West Indies are limited to common livestock pathogens such as Ehrlichia ruminantium, Babesia spp. (i.e., B. bovis and B. bigemina), and Anaplasma marginale, and less information is available on companion animal pathogens. Of note, human tick-borne diseases (TBDs) remain almost completely uncharacterized in the West Indies. Information on TBP presence in wildlife is also missing. Herein, we provide a comprehensive review of the ticks and TBPs affecting human and animal health in the Caribbean, and introduce the challenges associated with understanding TBD epidemiology and implementing successful TBD management in this region. In particular, we stress the need for innovative and versatile surveillance tools using high-throughput pathogen detection (e.g., high-throughput real-time microfluidic PCR). The use of such tools in large epidemiological surveys will likely improve TBD prevention and control programs in the Caribbean.

Verification of post-chemotherapeutic clearance of Theileria equi through concordance of nested PCR and immunoblot

Certain countries including the United States remain non-endemic for particular infectious diseases such as equine piroplasmosis through import restrictions and surveillance. Endemic regions often employ premunition as the primary method to control disease, however in non-endemic countries, chemosterilization combined with methods to confirm parasite elimination are required to maintain disease-free status. The ability of imidocarb diproprionate (ID) to clear persistent Theileria equi infection from infected horses has been shown through the inability of treated horses to transmit via blood transfer. However, the common lengthy persistence of anti-T. equi antibody causes regulatory tests such as cELISA or IFA to remain positive for extended periods. Persistence of positive testing creates challenges for regulatory veterinary medicine and international trade. Concordance between nested polymerase chain reaction (nPCR) targeting the ema1 gene and immunoblotting (IB) measuring declination in anti-EMA1 and anti-EMA2 antibody were used to verify clearance of T. equi from 179 ID-treated horses. These data support the use of IB to demonstrate declining anti-EMA1 and EMA2 titers in T. equi-infected horses subsequent to successful ID treatment. Such data provide concordant support to a negative nPCR and allow for a more timely determination of effective ID clearance of T. equi. The post ID treatment results indicate that while nPCR was consistently negative by 14 days and cELISA generally remained positive after 1 year, immunoblot was on average negative after 4 months and 100% in agreement with nPCR.

Amblyomma americanum ticks infected with in vitro cultured wild-type and mutants of Ehrlichia chaffeensis are competent to produce infection in naïve deer and dogs

Monocytic ehrlichiosis in people caused by the intracellular bacterium, Ehrlichia chaffeensis, is an emerging infectious disease transmitted by the lone star tick, Amblyomma americanum. Tick transmission disease models for ehrlichiosis require at least two hosts and two tick blood feeding episodes to recapitulate the natural transmission cycle. One blood feeding is necessary for the tick to acquire the infection from an infected host and the next feeding is needed to transmit the bacterium to a naïve host. We have developed a model for E. chaffeensis transmission that eliminates the entire tick acquisition stage while still producing high numbers of infected ticks that are also able to transmit infections to naïve hosts. Fully engorged A. americanum nymphs were ventrally needle-infected, possibly into the midgut, and following molting, the unfed adult ticks were used to infect naive deer and dogs. We have also described using the ticks infected by this method the transmission of both wild-type and transposon mutants of E. chaffeensis to its primary reservoir host, white tailed deer and to another known host, dog. The infection progression and IgG antibody responses in deer were similar to those observed with transmission feeding of ticks acquiring infection by natural blood feeding. The pathogen infections acquired by natural tick transmission and by feeding needle-infected ticks on animals were also similar to intravenous infections in causing persistent infections. Needle-infected ticks having the ability to transmit pathogens will be a valuable resource to substantially simplify the process of generating infected ticks and to study infection systems in vertebrate hosts where interference of other pathogens could be avoided.

Sequence heterogeneity in the 18S rRNA gene in Theileria equi from horses presented in Switzerland

A reverse line blot (RLB) hybridization assay was adapted and applied for equine blood samples collected at the animal hospital of the University of Zurich to determine the presence of piroplasms in horses in Switzerland. A total of 100 equine blood samples were included in the study. The V4 hypervariable region of the 18S rRNA gene was amplified by polymerase chain reaction and analyzed using the RLB assay. Samples from seven horses hybridized to a Theileria/Babesia genus-specific and a Theileria genus-specific probe. Of these, two hybridized also to the Theileria equi-specific probe. The other five positive samples did not hybridize to any of the species-specific probes, suggesting the presence of unrecognized Theileria variants or genotypes. The 18S rRNA gene of the latter five samples were sequenced and found to be closely related to T. equi isolated from horses in Spain (AY534822) and China (KF559357) (≥98.4% identity). Four of the seven horses that tested positive had a documented travel history (France, Italy, and Spain) or lived abroad (Hungary). The present study adds new insight into the presence and sequence heterogeneity of T. equi in Switzerland. The results prompt that species-specific probes must be designed in regions of the gene unique to T. equi. Of note, none of the seven positive horses were suspected of having Theileria infection at the time of presentation to the clinic. Clinicians should be aware of the possibility of equine piroplasma infections outside of endemic areas and in horses without signs of piroplasmosis.

Microscopic and Molecular Detection of Theileria (Babesia) Equi Infection in Equids of Kurdistan Province, Iran

BACKGROUND

Equine piroplasmosis (EP) is the cause of persistent tick-borne infection with no symptoms, but the most important problem of EP is due to the persistent carrier state. Carrier animals to Babesia (Theileria) equi (Laveran 1901) and B. caballi (Nuttall, 1910) infestation could be identified by extremely sensitive PCR-based method. The purpose of this study was to identify the causative agents of equine piroplasmosis based on molecular and microscopic assays in equids from Kurdistan Province, Iran.

METHODS

Thirty one horse and mule blood samples were used with history of living in Kurdistan Province of Iran. The blood specimens were utilized for T. equi and B. caballi DNA identification by PCR and Giemsa stained smears for microscopic observation.

RESULTS

The results clearly showed the presence of B. (Theileria) equi DNA in 30 of 31 blood samples (96.77%), but the microscopic examination revealed the 3 of 31 positive Babesia like organisms in the red blood cells (9.67%).

CONCLUSION

The obtained results demonstrated the presence of hidden B. (Theileria) equi infection in horses with previous habitance in Kurdistan Province of Iran. The carrier animals became a main source of infection and can transmit the disease. Therefore, hidden infection might be considered as a health threatening and limiting factor in animals used in therapeutic antisera research and production centers.

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.

Quantitative PCR detection of Theileria equi using laboratory workflows to detect asymptomatic persistently infected horses

Equine piroplasmosis is the most important tick-borne disease of horses. Regulations on movement of horses into disease-free countries are in place to preserve international trade. Introduction of infectious disease, such as equine piroplasmosis, into non-endemic countries remains a substantial risk owing to the wide-spread distribution of vectors. Identification and restriction of movement of Theileria equi persistently infected horses is an integral part of control strategies, because persistently infected horses with low parasitaemia are an important reservoir. We used real-time PCR for diagnosis of T. equi DNA in clinically healthy horses in an equine piroplasmosis endemic area. The sensitivity was assessed using a synthetic plasmid DNA and a laboratory workflow was developed to maximise detection of persistently infected horses. The detection limit was 10 rDNA copies of the plasmid DNA. Assuming that each red blood cell contains a single T. equi genome the detection limit corresponded to 2.5 T. equi/μl of total blood and parasitaemia as low as 2-3.8 × 10(-5)%. A laboratory workflow was developed and assessed on samples from Saudi Arabia. The laboratory workflow focused on samples returning no or single positive result in duplicate PCR. In total, we obtained 42% (59/141; 95% confidence interval: 33.85-50.15) T. equi positive samples, 26% (37/141) negative for T. equi samples. The remaining 45 samples were judged as suspect with no definitive diagnosis made. The Saudi Arabia's T. equi small subunit ribosomal DNA (SSU rDNA) sequencing (n=16) demonstrated A clade (n=15) as the dominant T. equi clade. Clade B was sequenced in a single case. We present an approach for diagnostic workflow to detect T. equi in clinically healthy but persistently infected horses. Results from Saudi Arabia confirm that T. equi is widespread in the Middle East region. High proportion of horses with low parasitaemia calls for caution with results based on a single blood sample. Understating of the fluctuation of the parasitaema in persistently infected horses in endemic areas is needed to establish the required sample numbers for reliable detection of T. equi.

Transmission dynamics of Borrelia turicatae from the arthropod vector

BACKGROUND

With the global distribution, morbidity, and mortality associated with tick and louse-borne relapsing fever spirochetes, it is important to understand the dynamics of vector colonization by the bacteria and transmission to the host. Tick-borne relapsing fever spirochetes are blood-borne pathogens transmitted through the saliva of soft ticks, yet little is known about the transmission capability of these pathogens during the relatively short bloodmeal. This study was therefore initiated to understand the transmission dynamics of the relapsing fever spirochete Borrelia turicatae from the vector Ornithodoros turicata, and the subsequent dissemination of the bacteria upon entry into murine blood.

METHODOLOGY/PRINCIPAL FINDINGS

To determine the minimum number of ticks required to transmit spirochetes, one to three infected O. turicata were allowed to feed to repletion on individual mice. Murine infection and dissemination of the spirochetes was evaluated by dark field microscopy of blood, quantitative PCR, and immunoblotting against B. turicatae protein lysates and a recombinant antigen, the Borrelia immunogenic protein A. Transmission frequencies were also determined by interrupting the bloodmeal 15 seconds after tick attachment. Scanning electron microscopy (SEM) was performed on infected salivary glands to detect spirochetes within acini lumen and excretory ducts. Furthermore, spirochete colonization and dissemination from the bite site was investigated by feeding infected O. turicata on the ears of mice, removing the attachment site after engorment, and evaluating murine infection.

CONCLUSION/SIGNIFICANCE

Our findings demonstrated that three ticks provided a sufficient infectious dose to infect nearly all animals, and B. turicatae was transmitted within seconds of tick attachment. Spirochetes were also detected in acini lumen of salivary glands by SEM. Upon host entry, B. turicatae did not require colonization of the bite site to establish murine infection. These results suggest that once B. turicatae colonizes the salivary glands the spirochetes are preadapted for rapid entry into the mammal.

Epidemiological investigation of equine piroplasmosis in China by enzyme-linked immunosorbent assays

The objective of this study is to investigate the seroprevalence of equine piroplasmosis in China. A total of 1990 sera were collected from clinically healthy horses in various districts located in ten different provinces of China and examined by using indirect enzyme-linked immunosorbent assays (ELISAs) with recombinant Theileria equi (T. equi) merozoite antigen 2 (rEMA-2) and Babesia caballi (B. caballi) 48-kDa rhoptry protein (rBc48), respectively. The results showed that 1,018 (51.16%) and 229 (11.51%) samples were positive for B. caballi and T. equi infection, respectively. The number of samples with mixed infection was 152 (7.64%). These results indicated that equine piroplasmosis was widespread in China.

Amblyomma cajennense is an intrastadial biological vector of Theileria equi

Background

The apicomplexan hemoprotozoan parasite Theileria equi is one of the etiologic agents causing equine piroplasmosis, a disease of equines that is endemic throughout large parts of the world. Before 2009 the United States had been considered to be free of this parasite. Occasional cases had occurred but there was no evidence for endemic vector-borne transmission in the U.S. until a 2009 outbreak in Texas in which Dermacentor variabilis and Amblyomma cajennense were implicated as vectors. Although D. variabilis has previously been shown to be a competent laboratory vector, studies suggested A. cajennense was not a competent transstadial vector, even though the presence of this tick species on horses in South American is epidemiologicaly correlated with higher a prevalence of infection. In this study we tested the transstadial and intrastadial vector competence of D. variabilis and A. cajennense for T. equi.

Methods

A tick passaged T. equi strain from the Texas outbreak and ticks colonized from engorged females collected off horses on the outbreak ranch in Texas were used for these studies. Nymph or adult ticks were fed on infected horses and transmission fed on naïve horses. Infections were tracked with PCR and serology, dissected tick tissues were tested with PCR.

Results

A. cajennense transmitted T. equi intrastadially when adult ticks acquired infection by feeding on an infected horse, and transmitted to a naïve host on subsequent reattachment and feeding. D. variabilis failed to transmit in the same experiment. Transstadial transmission was not successful for either tick species. PCR on DNA isolated from eggs of females that had fed on an infected horse suggests that there is no transovarial passage of this parasite by either tick species.

Conclusion

This work confirms that ticks from the Texas population of A. cajennense are competent intrastadial vectors of T. equi. We propose that the most likely natural mode of transmission for this parasite/vector combination in the Texas outbreak would have been biological transmission resulting from adult male ticks moving between infected and uninfected horses. The intrastadial mode of transmission should be considered as one equally possible scenario whenever implicating vectors of T. equi.

Lymphocytes and macrophages are infected by Theileria equi, but T cells and B cells are not required to establish infection in vivo

Theileria equi has a biphasic life cycle in horses, with a period of intraleukocyte development followed by patent erythrocytic parasitemia that causes acute and sometimes fatal hemolytic disease. Unlike Theileria spp. that infect cattle (Theileria parva and Theileria annulata), the intraleukocyte stage (schizont) of Theileria equi does not cause uncontrolled host cell proliferation or other significant pathology. Nevertheless, schizont-infected leukocytes are of interest because of their potential to alter host cell function and because immune responses directed against this stage could halt infection and prevent disease. Based on cellular morphology, Theileria equi has been reported to infect lymphocytes in vivo and in vitro, but the specific phenotype of schizont-infected cells has yet to be defined. To resolve this knowledge gap in Theileria equi pathogenesis, peripheral blood mononuclear cells were infected in vitro and the phenotype of infected cells determined using flow cytometry and immunofluorescence microscopy. These experiments demonstrated that the host cell range of Theileria equi was broader than initially reported and included B lymphocytes, T lymphocytes and monocyte/macrophages. To determine if B and T lymphocytes were required to establish infection in vivo, horses affected with severe combined immunodeficiency (SCID), which lack functional B and T lymphocytes, were inoculated with Theileria equi sporozoites. SCID horses developed patent erythrocytic parasitemia, indicating that B and T lymphocytes are not necessary to complete the Theileria equi life cycle in vivo. These findings suggest that the factors mediating Theileria equi leukocyte invasion and intracytoplasmic differentiation are common to several leukocyte subsets and are less restricted than for Theileria annulata and Theileria parva. These data will greatly facilitate future investigation into the relationships between Theileria equi leukocyte tropism and pathogenesis, breed susceptibility, and strain virulence.