Ecological Systems Laboratory, Department of Ecology and Conservation Biology, Texas A&M University, College Station, TX, 77843, USA.
Department of Entomology, Texas A&M AgriLife Research, College Station, TX, 77843, USA.
Parasit Vectors. 2020 Sep 23;13(1):487. doi: 10.1186/s13071-020-04366-x.
Some tick species are invasive and of high consequence to public and veterinary health. Socioeconomic development of rural parts of the USA was enabled partly through the eradication by 1943 of cattle fever ticks (CFT, Rhipicephalus (Boophilus) annulatus and R. (B.) microplus). The southern cattle fever ticks (SCFT, R. (B.) microplus) remain a real and present threat to the USA animal agriculture because they are established in Mexico. Livestock-wildlife interactions in the Permanent Quarantine Zone (PQZ) established by the century-old Cattle Fever Tick Eradication Programme (CFTEP) in south Texas endanger its operations.
We describe a spatially-explicit, individual-based model that simulates interactions between cattle, white-tailed deer (WTD, Odocoileus virginianus), and nilgai (Boselaphus tragocamelus) to assess the risk for SCFT infestations across the pathogenic landscape in the PQZ and beyond. We also investigate the potential role of nilgai in sustaining SCFT populations by simulating various hypothetical infestation and eradication scenarios.
All infestation scenarios resulted in a phase transition from a relatively small proportion of the ranch infested to almost the entire ranch infested coinciding with the typical period of autumn increases in off-host tick larvae. Results of eradication scenarios suggest that elimination of all on-host ticks on cattle, WTD, or nilgai would have virtually no effect on the proportion of the ranch infested or on the proportions of different tick habitat types infested; the entire ranch would remain infested. If all on-host ticks were eliminated on cattle and WTD, WTD and nilgai, or cattle and nilgai, the proportions of the ranch infested occasionally would drop to 0.6, 0.6 and 0.2, respectively. Differences in proportions of the ranch infested from year to year were due to primarily to differences in winter weather conditions, whereas infestation differences among tick habitat types were due primarily to habitat use preferences of hosts.
Infestations in nilgai augment SCFT refugia enabled by WTD and promote pest persistence across the landscape and cattle parasitism. Our study documented the utility of enhanced biosurveillance using simulation tools to mitigate risk and enhance operations of area-wide tick management programmes like the CFTEP through integrated tactics for SCFT suppression.
一些蜱种具有入侵性，对公共卫生和兽医健康有重大影响。美国农村地区的社会经济发展部分得益于 1943 年通过根除牛热蜱（CFT，Rhipicephalus（Boophilus）annulatus 和 R.（B.）microplus）实现的。南方牛热蜱（SCFT，R.（B.）microplus）仍然对美国动物农业构成真正和当前的威胁，因为它们在墨西哥已经建立了种群。在德克萨斯州南部已有百年历史的牛热蜱根除计划（CFTEP）建立的永久性隔离区（PQZ）中，牲畜与野生动物的相互作用危及该计划的运作。
我们描述了一个空间显式的、基于个体的模型，该模型模拟了牛、白尾鹿（Odocoileus virginianus）和印度野牛（Boselaphus tragocamelus）之间的相互作用，以评估在 PQZ 及其以外的致病性景观中 SCFT 感染的风险。我们还通过模拟各种假设的感染和根除情景，研究了印度野牛在维持 SCFT 种群中的潜在作用。
所有感染情景均导致牧场受感染的比例从相对较小的比例过渡到几乎整个牧场受感染的比例，这与秋季非宿主蜱幼虫数量增加的典型时期相吻合。根除情景的结果表明，消除牛、白尾鹿或印度野牛上的所有宿主蜱几乎不会对牧场受感染的比例或不同蜱栖息地类型受感染的比例产生影响；整个牧场仍将受感染。如果消除牛、白尾鹿或牛和印度野牛上的所有宿主蜱，牧场受感染的比例偶尔会降至 0.6、0.6 和 0.2，分别。牧场受感染比例的年际差异主要归因于冬季天气条件的差异，而蜱栖息地类型的感染差异主要归因于宿主的栖息地使用偏好。
印度野牛中的感染增加了白尾鹿带来的 SCFT 避难所，并促进了景观和牛寄生虫病的害虫持续存在。我们的研究记录了使用模拟工具增强生物监测的效用，以通过综合策略来减轻风险并加强像 CFTEP 这样的全区域蜱管理计划的运作。
