Shereni William, Anderson Neil E, Nyakupinda Learnmore, Cecchi Giuliano
Tsetse Control Division, Department of Livestock and Veterinary Services, Ministry of Agriculture, Mechanization and Irrigation Development, Harare, Zimbabwe.
The Royal (Dick) School of Veterinary Studies and the Roslin Institute, University of Edinburgh, Easter Bush Campus, Roslin, UK.
Parasit Vectors. 2016 Nov 25;9(1):605. doi: 10.1186/s13071-016-1879-5.
In Zimbabwe, cases of human African trypanosomiasis (HAT) are caused by the unicellular protozoan Trypanosoma brucei, sub-species T. b. rhodesiense. They are reported from the tsetse-infested area in the northern part of the country, broadly corresponding to the valley of the Zambezi River. Tsetse-transmitted trypanosomes, in particular T. congolense and T. vivax, also cause morbidity and mortality in livestock, thus generating poverty and food insecurity. Two species of tsetse fly, Glossina morsistans morsitans and G. pallidipes, are known to be present in the Zambezi Valley, although their distributional patterns and densities have not been investigated in detail. The present study tries to address this gap by providing some insight into the dynamics of trypanosomiasis in humans and livestock.
Tsetse distribution and trypanosome infections were studied using traps and fixed fly rounds located at 10 km intervals along a 110 km long transect straddling the southern escarpment of the Zambezi Valley. Three km long fly rounds were conducted on 12 sites, and were repeated 11 times over a 7-month period. Additional traps were deployed and monitored in selected sites. Microscopic examination of 2092 flies for trypanosome infections was conducted.
Surveys confirmed the presence of G. morsitans morsitans and G. pallidipes in the Zambezi Valley floor. Moving south, the apparent density of tsetse flies appears to peak in the vicinity of the escarpment, then drops on the highlands. Only one fly was caught south of the old game fence separating protected and settled areas. A trypanosome infection rate of 6.31% was recorded in tsetse flies dissected. Only one infection of the T. brucei-type was detected.
Tsetse fly distribution in the study area appears to be driven by ecological factors such as variation in land use and altitude-mediated climatic patterns. Although targeted control of tsetse flies have played a role in determining distribution, no major control operations have been implemented in the area for 15 years. Trypanosome infections in tsetse flies are consistent with HAT epidemiological data, which considers the situation to be generally 'low risk'. Nonetheless, underreporting is likely to conceal the true epidemiological picture, and efforts are needed to strengthen the diagnostic capacities of health facilities.
在津巴布韦，人类非洲锥虫病（HAT）病例由单细胞原生动物布氏锥虫罗德西亚亚种引起。这些病例报告于该国北部采采蝇滋生的地区，大致对应赞比西河河谷。采采蝇传播的锥虫，尤其是刚果锥虫和活泼锥虫，也会导致牲畜发病和死亡，进而造成贫困和粮食不安全。已知赞比西河谷存在两种采采蝇，即莫氏采采蝇和淡黄采采蝇，不过它们的分布模式和密度尚未得到详细研究。本研究试图通过深入了解人类和牲畜锥虫病的动态情况来填补这一空白。
沿着横跨赞比西河谷南麓的一条110公里长的样带，每隔10公里设置诱捕器和固定的采采蝇巡查路线，以此研究采采蝇分布和锥虫感染情况。在12个地点进行了3公里长的采采蝇巡查，并在7个月内重复进行了11次。在选定地点额外部署并监测了诱捕器。对2092只采采蝇进行了显微镜检查以检测锥虫感染情况。
调查证实赞比西河谷底部存在莫氏采采蝇和淡黄采采蝇。向南移动时，采采蝇的表观密度似乎在悬崖附近达到峰值，然后在高地上下降。在分隔保护区和定居区的旧狩猎围栏以南仅捕获到一只采采蝇。在解剖的采采蝇中记录到的锥虫感染率为6.31%。仅检测到一例布氏锥虫类型的感染。
研究区域内采采蝇的分布似乎受土地利用变化和海拔介导的气候模式等生态因素驱动。尽管有针对性的采采蝇控制措施在决定其分布方面发挥了作用，但该地区已有15年未开展重大控制行动。采采蝇中的锥虫感染情况与人类非洲锥虫病的流行病学数据相符，该数据认为总体情况为“低风险”。尽管如此，报告不足可能掩盖真实的流行病学情况，因此需要努力加强卫生设施的诊断能力。
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