The impact of vector control on the prevalence of Theileria cervi in farmed Florida white-tailed deer, Odocoileus virginianus

Allison Cauvin,Samantha M Wisely,Rebecca Shuman,Karen Hood,Jeremy Orange,Jason K Blackburn,Katherine A Sayler

doi:10.1186/s13071-019-3344-8

Allison Cauvin, Samantha M Wisely + Show 5 more

Open Access

https://doi.org/10.1186/s13071-019-3344-8

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Abstract

BackgroundVector-borne diseases exert a global economic impact to the livestock industry. Understanding how agriculture practices and acaricide usage affect the ecology of these diseases is important for making informed management decisions. Theileria cervi is a hemoprotozoan parasite infecting white-tailed deer (Odocoileus virginianus) and is transmitted by the lone star tick, Amblyomma americanum. The purpose of this study was to determine if acaricide treatment decreased hematozoan prevalence in farmed white-tailed deer when compared to geographically-close wild deer or altered the genotypes of T. cervi present.ResultsWe compared prevalence of T. cervi in 52 farmed adult white-tailed deer which were regularly treated with permethrin and ivermectin, 53 farmed neonates that did not receive treatment for vector control, and 42 wild deer that received no form of chemical vector control. Wild deer had significantly higher prevalence of T. cervi than farmed deer. Additionally, no neonate fawns tested positive for T. cervi, and we found that age was a significant predictor of infection status. We found no difference in genotypic variation in T. cervi isolates between adjacent herds of farmed and wild white-tailed deer, although a divergent genotype X was identified. Chronic infection with T. cervi had no significant effects on mortality in the white-tailed deer.ConclusionsWe found significantly lower prevalence of T. cervi infection in farmed (40%) compared to wild white-tailed deer (98%), which may be due to the inclusion of chemical vector control strategies. More work is needed to determine the implications, if any, of mixed genotypic infections of T. cervi, although we found no significant effect of infection with Theileria on mortality in farmed deer. Theileria infection does sometimes cause disease when an animal is stressed, immunosuppressed, or translocated from non-endemic to endemic regions.

Highlights

Vector-borne diseases exert a global economic impact to the livestock industry
We found no significant difference in T. cervi prevalence between the farmed deer re-sampled in spring vs autumn (Fisher’s exact test, P = 0.65)
Wild deer sampled in spring 2016 had a 100% (12/12) prevalence for T. cervi infection, and wild deer sampled in autumn 2016 had a 96.7% (29/30) prevalence

Summary

Introduction

Vector-borne diseases exert a global economic impact to the livestock industry. Understanding how agriculture practices and acaricide usage affect the ecology of these diseases is important for making informed management decisions. These obligate intracellular parasites are transmitted by ixodid ticks and have been detected in select mammalian species on almost every continent [8] These organisms cause some of the most economically important and costly livestock diseases in the world [9]. Theileria parva, the etiological agent of East Coast fever, can exist in a state of endemic stability in indigenous cattle breeds and cause little economic loss with little intervention or can cause enormous economic loss in naïve herds [5] These epidemiological differences are driven by the prevalence of infection within herds and sympatric reservoir species, the age at which animals are infected, and management actions such as chemical vector control [10]

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