Livestock, pathogens, vectors, and their environment: A causal inference-based approach to estimating the pathway-specific effect of livestock on human African trypanosomiasis risk.
Livestock, pathogens, vectors, and their environment: A causal inference-based approach to estimating the pathway-specific effect of livestock on human African trypanosomiasis risk.
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DOI：
10.1371/journal.pgph.0002543
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发表时间：
2023
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牲畜是许多人畜共患病的重要宿主，然而牲畜对人类和环境健康的影响远远超出了疾病的直接传播。在这项回顾性生态队列研究中，我们使用预先存在的数据和参数g公式（该公式估算了潜在结果以量化中介）来估计牲畜可以影响人类非洲锥虫病（HAT）风险的三种假设机制：水库效应，其中受感染的牛和猪是人类感染的来源;动物预防作用，即HAT的采采蝇媒介对牲畜宿主表现出的偏好意味着它们的存在保护人类免受感染;以及环境变化效应，即牲畜饲养活动改变了环境，降低了采采蝇栖息地的适宜性，从而降低了人类感染风险。我们在四个高负担国家进行了这项研究：在乌干达，马拉维和刚果民主共和国（DRC）的点级，以及南苏丹的县级。我们的研究结果表明，牛和猪在乌干达的罗得西亚形式（rHAT）中发挥着水库作用牛的RR为1.68，95% CI为0.84，2.82; RR 2.16，95% CI 1.18，3.05（猪）），然而，在马拉维，动物预防超过了rHAT的这种效应（牛RR 0.85，95% CI 0.68，1.00;猪RR 0.38，95% CI 0.21，0.69）。对于冈比亚型（gHAT），我们发现有证据表明猪可能是一个有能力的储库（乌干达RR 1.15，95% CI 0.92，1.72;刚果民主共和国RR 1.25，95% CI 1.11，1.42）。马拉维（猪和牛）和乌干达（仅猪）的rHAT以及刚果民主共和国（猪和牛）的gHAT达到统计学显著性。我们没有发现环境变化效应的令人信服的证据（所有效应量接近1）。
Livestock are important reservoirs for many zoonotic diseases, however the effects of livestock on human and environmental health extend well beyond direct disease transmission. In this retrospective ecological cohort study we use pre-existing data and the parametric g-formula, which imputes potential outcomes to quantify mediation, to estimate three hypothesized mechanisms by which livestock can influence human African trypanosomiasis (HAT) risk: the reservoir effect, where infected cattle and pigs are a source of infection to humans; the zooprophylactic effect, where preference for livestock hosts exhibited by the tsetse fly vector of HAT means that their presence protects humans from infection; and the environmental change effect, where livestock keeping activities modify the environment in such a way that habitat suitability for tsetse flies, and in turn human infection risk, is reduced. We conducted this study in four high burden countries: at the point level in Uganda, Malawi, and Democratic Republic of Congo (DRC), and at the county level in South Sudan. Our results indicate cattle and pigs play a reservoir role for the rhodesiense form (rHAT) in Uganda (rate ratio (RR) 1.68, 95% CI 0.84, 2.82 for cattle; RR 2.16, 95% CI 1.18, 3.05 for pigs), however zooprophylaxis outweighs this effect for rHAT in Malawi (RR 0.85, 95% CI 0.68, 1.00 for cattle, RR 0.38, 95% CI 0.21, 0.69 for pigs). For the gambiense form (gHAT) we found evidence that pigs may be a competent reservoir (RR 1.15, 95% CI 0.92, 1.72 in Uganda; RR 1.25, 95% CI 1.11, 1.42 in DRC). Statistical significance was reached for rHAT in Malawi (pigs and cattle) and Uganda (pigs only) and for gHAT in DRC (pigs and cattle). We did not find compelling evidence of an environmental change effect (all effect sizes close to 1).