School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, 5371, Australia; Vertebrate Pest Research Unit, NSW Department of Primary Industries, Orange, NSW, 2800 Australia.
School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, 5371, Australia.
Vet Parasitol. 2020 Dec;288:109306. doi: 10.1016/j.vetpar.2020.109306. Epub 2020 Nov 5.
Rodents comprise a major component of cat (Felis catus) diets in many ecosystems, and life cycle diagrams of Toxoplasma gondii typically depict small rodents as quintessential intermediate hosts. Counter-intuitively, small rodents often experience a lower T. gondii seroprevalence than do larger sympatric mammals. This observation has repeatedly caused confusion about the relative importance of small rodents to the ecology of T. gondii. To address this confusion, we modified the Reed-Frost epidemic model to develop a simple binomial equation to model T. gondii transmission from prey to feline predators. This equation takes into account variations in prey seroprevalence and the frequency with which they are consumed by felids. Even when T. gondii seroprevalence in prey is < 1%, computation reveals that the risk of feline exposure to T. gondii can easily exceed 50 % annually. For example, if cats eat an average of 1 mouse per day, a seroprevalence of 0.2 % (1/500) in mice will cause 51.9 % of cats to be exposed to T. gondii annually. Our simple equation demonstrates that both prey seroprevalence and the rate at which prey are consumed are of approximately equal importance to the ecology of T. gondii. When inferring the importance of various prey species to the ecology of T. gondii, researchers must consider the predation and dietary habits of felids from within their study system. Our simple binomial equation could also be used to predict T. gondii exposure rates of humans or other carnivorous animals from various dietary sources or be applied to other predator-prey parasite life cycles.
啮齿动物是许多生态系统中猫（Felis catus）饮食的主要组成部分，刚地弓形虫的生命周期图通常将小型啮齿动物描绘为典型的中间宿主。与直觉相反的是，小型啮齿动物的刚地弓形虫血清阳性率通常低于体型较大的共生哺乳动物。这一观察结果反复引起了人们对小型啮齿动物对刚地弓形虫生态学相对重要性的混淆。为了解决这一混淆，我们修改了里德-弗罗斯特传染病模型，开发了一个简单的二项式方程来模拟刚地弓形虫从猎物向猫科捕食者的传播。该方程考虑了猎物血清阳性率的变化以及它们被猫科动物消耗的频率。即使猎物的刚地弓形虫血清阳性率<1%，计算结果显示，猫科动物暴露于刚地弓形虫的风险很容易每年超过 50%。例如，如果猫每天平均吃 1 只老鼠，那么老鼠的血清阳性率为 0.2%（1/500），将导致 51.9%的猫每年暴露于刚地弓形虫。我们的简单方程表明，猎物的血清阳性率和猎物被消耗的速度对刚地弓形虫的生态学具有大致相同的重要性。在推断各种猎物物种对刚地弓形虫生态学的重要性时，研究人员必须考虑其研究系统内的猫科动物的捕食和饮食习惯。我们的简单二项式方程还可以用于预测人类或其他肉食性动物从各种饮食来源暴露于刚地弓形虫的比率，或应用于其他捕食者-猎物-寄生虫的生命周期。
