Outbreak of equine piroplasmosis in Florida

Short, Michael A.; Clark, Carol; Harvey, John W.; Wenzlow, Nanny; Hawkins, Ian K.; Allred, David R.; Knowles, Donald P.; Corn, Joseph L.; Grause, Juanita F.; Hennager, Steven G.; Kitchen, Diane L.; Traub‐Dargatz, Josie L.

doi:10.2460/javma.240.5.588

Cited by 60 publications

(72 citation statements)

References 18 publications

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“…The EP free status of the U.S. was due, at least in part, to the fact that there was no evidence for endemic vector-borne transmission. Some of the sporadic cases that had been identified in the U.S. prior to the 2009 outbreak may have been the result of diagnostic insensitivity at importation because the complement fixation test [8], used for import screening prior to 2005, has a high incidence of false negative results [9]. Prior to the Texas outbreak vector-borne transmission had not been suspected for any of the U.S. cases.…”

Section: Introductionmentioning

confidence: 99%

Amblyomma cajennense is an intrastadial biological vector of Theileria equi

Scoles

Ueti

2013

Parasites Vectors

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BackgroundThe 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.MethodsA 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.ResultsA. 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.ConclusionThis 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.

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Section: Introductionmentioning

confidence: 99%

Amblyomma cajennense is an intrastadial biological vector of Theileria equi

Scoles

Ueti

2013

Parasites Vectors

View full text Add to dashboard Cite

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“…The complement fixation test (CFT) was the official regulatory test in the United States until it was determined to yield an unacceptable number of false-negative results due to the inability of equine IgG subclass 5 to fix complement (14,15). The failure of the CFT to detect all persistently infected horses with T. equi may have resulted in the reintroduction of this pathogen, leading to the recent outbreaks in the United States (2,8,12). In 2005, the CFT was replaced with the competitive enzyme-linked immunosorbent assay (cELISA) as the official regulatory test for EP.…”

mentioning

confidence: 99%

“…Both B. caballi and T. equi are widespread in tropical and subtropical regions, where approximately 90% of the world's horse population is located (9), and few countries in these regions can be considered EP free, as reported by the World Organization for Animal Health (OIE). The United States is still considered EP free and has been reporting to the OIE on individual outbreaks identified since 2008 (2,12). EP is designated a foreign animal disease in the United States, and any case identified initiates an immediate regulatory response, including quarantine and control measures.…”

mentioning

confidence: 99%

“…entral to biosecurity strategies is preventing the spread of infectious animal diseases by strictly regulating movement of infected animals (1,2). The introduction of infected animals into a naive population increases the risk of transmitting pathogens that could cause significant economic losses to the livestock industry (2,3).…”

mentioning

confidence: 99%

“…The introduction of infected animals into a naive population increases the risk of transmitting pathogens that could cause significant economic losses to the livestock industry (2,3). Importation of animals and animal by-products from areas with a high prevalence of infectious agents is tightly regulated, and imported animals are screened and quarantined at all entry points for further testing and evaluation (4).…”

mentioning

confidence: 99%

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