Grzeda Emily, Maurer Taylor, Dannemann Clara, Kibiriti Lemaly Ole, Kioko John, Kiffner Christian
Miami University, Oxford, OH, USA.
Kenyon College, Gambier, OH, USA.
Parasitol Res. 2017 Nov;116(11):3163-3173. doi: 10.1007/s00436-017-5633-5. Epub 2017 Oct 5.
Ticks and associated pathogens pose serious threats to the health of livestock. To assess the efficacy of acaricide dip treatment (cypermethrin, chlorpyrifos, piperonyl butoxide, citronella), we assessed post-treatment tick acquisition and tick mortality of free-ranging Boran cattle inhabiting a wildlife-cattle ranch in Northern Tanzania. Because host intrinsic variables and exposure to ticks may substantially affect tick acquisition, we incorporated host sex, body mass, health condition, and distance traveled in models of tick acquisition. Using generalized linear mixed models that accounted for non-independence of individuals, we found that tick species richness increased with host body mass but was not significantly related to other factors. In contrast, tick abundance increased with time since acaricide treatment, was positively correlated with host body mass, and was higher in female than male cattle. Distance traveled and health condition did not predict tick acquisition. Overall, these patterns were similar when separately analyzing acquisition of the more common tick species (Rhipicephalus pulchellus, R. sanguineus sensu lato, and R. praetextatus). Logistic regression models suggested that tick mortality was high for a few days after acaricide dip treatment but declined steeply post-treatment; 3.5 days after treatment, only 50% of ticks were dead, and mortality declined further thereafter. Our results provide new information regarding tick acquisition patterns in this system including female-biased tick parasitism and support for the hypothesis that increased host body mass provides greater resources and thus supports higher ectoparasite abundance and species richness. The limited acaricide duration of action and effectiveness on all tick species calls for adjusting tick management practices.
蜱虫及其相关病原体对家畜健康构成严重威胁。为评估杀螨剂浸浴处理（氯氰菊酯、毒死蜱、胡椒基丁醚、香茅油）的效果，我们对坦桑尼亚北部一个野生动物与牛群混居牧场中自由放养的博拉牛进行了处理后蜱虫附着情况及蜱虫死亡率的评估。由于宿主内在变量和蜱虫暴露情况可能会对蜱虫附着产生重大影响，我们在蜱虫附着模型中纳入了宿主性别、体重、健康状况以及移动距离等因素。通过使用考虑个体非独立性的广义线性混合模型，我们发现蜱虫物种丰富度随宿主体重增加而增加，但与其他因素无显著关联。相比之下，蜱虫数量随着杀螨剂处理后的时间增加而增多，与宿主体重呈正相关，且雌性牛身上的蜱虫数量高于雄性。移动距离和健康状况无法预测蜱虫附着情况。总体而言，在分别分析较常见蜱虫物种（微小扇头蜱、血红扇头蜱指名亚种和草原扇头蜱）的附着情况时，这些模式是相似的。逻辑回归模型表明，杀螨剂浸浴处理后的几天内蜱虫死亡率较高，但处理后急剧下降；处理3.5天后，只有50%的蜱虫死亡，此后死亡率进一步下降。我们的研究结果提供了关于该系统中蜱虫附着模式的新信息，包括蜱虫寄生的雌性偏好，并支持了宿主体重增加会提供更多资源从而支持更高的体表寄生虫数量和物种丰富度这一假说。杀螨剂作用持续时间有限且对所有蜱虫物种效果不佳，这就需要调整蜱虫管理措施。
