Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
Department of Entomology, College of Agriculture and Life Sciences, Texas A&M University, College Station, Texas, United States of America.
PLoS Negl Trop Dis. 2023 Jan 24;17(1):e0011084. doi: 10.1371/journal.pntd.0011084. eCollection 2023 Jan.
Canine Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and transmitted by insect triatomine vectors known as kissing bugs. The agent can cause cardiac damage and long-term heart disease and death in humans, dogs, and other mammals. In laboratory settings, treatment of dogs with systemic insecticides has been shown to be highly efficacious at killing triatomines that feed on treated dogs.
We developed compartmental vector-host models of T. cruzi transmission between the triatomine and dog population accounting for the impact of seasonality and triatomine migration on disease transmission dynamics. We considered a single vector-host model without seasonality, and model with seasonality, and a spatially coupled model. We used the models to evaluate the effectiveness of the insecticide fluralaner with different durations of treatment regimens for reducing T. cruzi infection in different transmission settings.
In low and medium transmission settings, our model showed a marginal difference between the 3-month and 6-month regimens for reducing T. cruzi infection among dogs. The difference increases in the presence of seasonality and triatomine migration from a sylvatic transmission setting. In high transmission settings, the 3-month regimen was substantially more effective in reducing T. cruzi infections in dogs than the other regimens. Our model showed that increased migration rate reduces fluralaner effectiveness in all treatment regimens, but the relative reduction in effectiveness is minimal during the first years of treatment. However, if an additional 10% or more of triatomines killed by dog treatment were eaten by dogs, treatment could increase T. cruzi infections in the dog population at least during the first year of treatment.
Our analysis shows that treating all peridomestic dogs every three to six months for at least five years could be an effective measure to reduce T. cruzi infections in dogs and triatomines in peridomestic transmission settings. However, further studies at the local scale are needed to better understand the potential impact of routine use of fluralaner treatment on increasing dogs' consumption of dead triatomines.
犬恰加斯病由原生动物寄生虫克氏锥虫引起，通过称为接吻虫的昆虫三锥虫传播。该病原体可导致人类、狗和其他哺乳动物心脏受损和长期心脏病死亡。在实验室环境中，已证明用全身杀虫剂治疗狗可高度有效地杀死以接受治疗的狗为食的三锥虫。
我们开发了三锥虫在三锥虫和狗种群之间传播的隔室型矢量宿主模型，考虑了季节性和三锥虫迁移对疾病传播动态的影响。我们考虑了没有季节性的单一矢量宿主模型、具有季节性的模型和空间耦合模型。我们使用这些模型来评估不同治疗方案的杀虫剂氟虫腈在不同传播环境下降低 T. cruzi 感染的有效性。
在低和中传播环境下，我们的模型显示 3 个月和 6 个月的治疗方案在降低狗中的 T. cruzi 感染方面略有差异。在存在季节性和三锥虫迁移的情况下，这种差异会增加。在高传播环境下，3 个月的治疗方案在降低狗中的 T. cruzi 感染方面比其他方案更有效。我们的模型表明，迁移率的增加会降低所有治疗方案中氟虫腈的有效性，但在治疗的最初几年，有效性的相对降低幅度很小。然而，如果狗处理杀死的三锥虫中有 10%或更多被狗吃掉，那么治疗可能会增加狗种群中的 T. cruzi 感染，至少在治疗的头一年是这样。
我们的分析表明，每三到六个月对所有家庭周围的狗进行治疗，至少持续五年，可能是减少家庭周围传播环境中狗和三锥虫 T. cruzi 感染的有效措施。然而，需要在当地范围内进一步研究，以更好地了解常规使用氟虫腈治疗对增加狗对死三锥虫的消耗的潜在影响。
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