Toé L, Tang J, Back C, Katholi C R, Unnasch T R
DNA Diagnostics Laboratory, Onchocerciasis Control Programme in West Africa, Bouake, Ivory Coast.
Lancet. 1997 Jan 18;349(9046):163-6. doi: 10.1016/S0140-6736(96)05265-8.
In West Africa, there are two strains of the filarial parasite Onchocerca volvulus, which differ in their ability to induce ocular disease. Transmission studies have suggested that six sibling species of the parasite vector, the black fly Simulium damnosum sensu lato, allow development of the two strains of O volvulus with varying efficiency. We aimed to test the hypothesis of parasite-vector complexes, whereby the two parasite strains, known as forest and savanna, are preferentially transmitted by distinct groups of the species of S damnosum S l.
During 1993 and 1994, wild black flies were collected from 11 river basins within the area covered by the Onchocerciasis Control Programme (OCP). The flies were dissected and filarial larvae, ovaries, and malpighian tubules removed. Genomic DNA was extracted from larvae, and PCR amplification was used to classify O volvulus parasites as forest or savanna strains. PCR-amplified DNA from ovaries and malpighian tubules was used to distinguish sibling species of S damnosum s l. S yahense and S squamosum were distinguished by body colour.
214 of 105105 flies dissected were infected with filarial larvae; 84 of these were infected with mature O volvulus parasites. Of the 35 savanna-dwelling infected flies. 17 carried forest-strain parasites and 18 savanna-strain parasites. Of the 45 infected flies identified as the forest dwelling sibling species. 20 carried savanna-strain parasites and 25 forest-strain parasites. No significant differences were found in the numbers of mature larvae of each strain carried by the forest-dwelling species of fly or in the number of forest and savanna larvae in savanna-dwelling vector species.
Vector-parasite transmission complexes do not currently play a part in the biology of O volvulus transmission in the area of the OCP in West Africa. This finding has important strategic implications for the future of efforts to control onchocerciasis in West Africa.
在西非，存在两种盘尾丝虫寄生虫菌株，它们诱发眼部疾病的能力有所不同。传播研究表明，寄生虫载体——黑蝇指名亚种（Simulium damnosum sensu lato）的六个姊妹物种，使这两种盘尾丝虫菌株的发育效率各异。我们旨在验证寄生虫-载体复合体的假说，即两种已知为森林型和稀树草原型的寄生虫菌株，分别由不同的黑蝇指名亚种群体优先传播。
在1993年至1994年期间，从盘尾丝虫病控制计划（OCP）覆盖区域内的11个流域收集野生黑蝇。解剖这些黑蝇，取出丝虫幼虫、卵巢和马氏管。从幼虫中提取基因组DNA，并使用聚合酶链反应（PCR）扩增将盘尾丝虫寄生虫分类为森林型或稀树草原型菌株。从卵巢和马氏管中PCR扩增的DNA用于区分黑蝇指名亚种的姊妹物种。雅氏黑蝇（S yahense）和鳞黑蝇（S squamosum）通过体色区分。
在解剖的105105只黑蝇中，有214只感染了丝虫幼虫；其中84只感染了成熟的盘尾丝虫寄生虫。在35只感染的稀树草原栖息黑蝇中，17只携带森林型菌株寄生虫，18只携带稀树草原型菌株寄生虫。在45只被鉴定为森林栖息姊妹物种的感染黑蝇中，20只携带稀树草原型菌株寄生虫，25只携带森林型菌株寄生虫。在森林栖息型黑蝇携带的每种菌株成熟幼虫数量上，或在稀树草原栖息型载体物种中森林型和稀树草原型幼虫数量上，均未发现显著差异。
在西非OCP区域，载体-寄生虫传播复合体目前在盘尾丝虫传播生物学中不起作用。这一发现对西非未来控制盘尾丝虫病的努力具有重要的战略意义。
