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

Sears, Kelly P.; Kappmeyer, Lowell S.; Wise, L.N.; Silva, Marta; Ueti, Massaro W.; White, Stephen N.; Reif, Kathryn E.; Knowles, Donald P.

doi:10.1016/j.vetpar.2019.06.009

Cited by 27 publications

(38 citation statements)

References 33 publications

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“…The newly proposed T. haneyi (Knowles et al, ) appears to be positioned in clade C, and the previously described T. equi reference genome belongs to clade A (Hall et al, ). Knowles et al () note that they were yet to find natural co‐infection of animals with these two types, although recent experimental work by the group has shown super‐infection is possible (Sears et al, ). Since this screening of Gambian samples has only focused on genotyping based on a single genetic locus, it is impossible to confirm whether the clade C samples detected here correspond to T. haneyi per se.…”

Section: Discussionmentioning

confidence: 99%

“…Infection of equines with different T. equi clade genotypes has been noted, with studies of naturally infected populations showing differences in the severity of clinical signs between individuals depending on the infecting genotype (Manna et al, ). Additionally, recent experimental work has shown that super‐infection with both T. equi and the newly described T. haneyi is possible, and can be maintained for many months (Sears et al, ). In comparison with T. haneyi infection, T. equi infection results in greater haematological effect, with a more pronounced neutropenia which becomes more marked following experimental super‐infection with T. haneyi (Sears et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Theileria equi diversity in The Gambia using a novel genotyping method

Coultous

McDonald

Raftery

et al. 2019

Transbound Emerg Dis

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Theileria equi, one of the primary pathogens causing equine piroplasmosis, has previously been sub‐classified into a number of clades on the basis of 18S SSU rRNA gene sequence diversity. This partitioning of the parasite population has potential implications for host immunity, treatment and vaccine development. To detect and identify different clade genotypes among and within individual equine blood samples, a novel PCR‐based technique was designed and optimized. Theileria equi has only recently been described in The Gambia, and the developed genotyping technique was used to analyse blood samples taken from 42 piroplasmosis‐positive horses and donkeys within the country. Three different T. equi genotypes were detected within the population, including the same genotype as the recently described Theileria haneyi, with 61.9% of individuals found to be infected with more than one genotype. Overall, there was a trend that males were more likely to have a multiple genotype infection. Thus, the novel genotyping technique has been shown to be effective in analysis of field populations and offers researchers a rapid method of identifying multiple T. equi genotypes both within individuals and equine populations in epidemiological studies.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of Theileria equi diversity in The Gambia using a novel genotyping method

Coultous

McDonald

Raftery

et al. 2019

Transbound Emerg Dis

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“…Five distinct T. equi clades are currently recognized [12], and recent work has provided sufficient evidence to define a second species of equine-infective Theileria, known as Theileria haneyi [13]. In contrast to T. equi, T. haneyi (Eagle Pass strain) induces minimal clinical disease in spleen-intact horses [13,14], characterized by mild changes in PCV and occasional development of fever during the acute phase [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…Prevalence surveys in The Gambia, Nigeria, and South Africa have also reported co-infection of horses with T. equi and T. haneyi or triple infection with T. equi, T.haneyi, and B. caballi [15][16][17]. Both organisms cause persistent, asymptomatic infection, and both are capable of superinfection in the presence of humoral immunity to the other [14]. Long-term studies suggest that the majority of co-infected horses are unable to spontaneously clear either species, and, as there is not yet a vaccine, control strategies are centered on acaricide use, rigorous surveillance testing, and the use of chemotherapeutic drugs to clear infection.…”

Section: Introductionmentioning

confidence: 99%

“…Long-term studies suggest that the majority of co-infected horses are unable to spontaneously clear either species, and, as there is not yet a vaccine, control strategies are centered on acaricide use, rigorous surveillance testing, and the use of chemotherapeutic drugs to clear infection. [3,14] Currently, the only medication known to be effective in achieving T. equi chemosterilization in vivo is imidocarb dipropionate (ID), an aromatic diamidine and carbanilide derivative [7,18,19]. Frerichs et al initially validated the current ID treatment regimen of 4 mg/kg, administered every 72 hours for 4 doses [18].…”

Section: Introductionmentioning

confidence: 99%

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Imidocarb Dipropionate Lacks Efficacy Against Theileria haneyi and Fails to Consistently Clear Theileria equi in Horses Co-infected with T. haneyi<b></b>

Sears

Knowles

Dinkel

et al. 2020

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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 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 2/3 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.

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

et al. 2020

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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.

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

Cited by 27 publications

References 33 publications

Analysis of Theileria equi diversity in The Gambia using a novel genotyping method

Analysis of Theileria equi diversity in The Gambia using a novel genotyping method

Imidocarb Dipropionate Lacks Efficacy Against Theileria haneyi and Fails to Consistently Clear Theileria equi in Horses Co-infected with T. haneyi<b></b>

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

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