Two for One – ivermectin and mosquitoes

Suppose that when mosquitoes bit you, they died. The possibility that a human blood meal can kill mosquitoes sounds far fetched, but has been observed as a by-product of mass community mass drug administration (MDA) of ivermectin for lymphatic filariasis in Senegal.

Researchers in Senegal compared villages where MDA was performed with a control set of villages and concluded that, “Ivermectin MDA significantly reduced the survivorship of An. gambiae s.s. for six days past the date of the MDA, which is sufficient to temporarily reduce malaria transmission. Repeated IVM MDAs could be a novel and integrative malaria control tool in areas with seasonal transmission, and which would have simultaneous impacts on neglected tropical diseases in the same villages.”

This is not the only time links have been made between malaria and lymphatic filariasis. A good example was community distribution of insecticide treated nets were provided in Nigeria, which curtailed the mosquitoes that carried both diseases.

In MDA programs for filariasis control “The goal is to treat 80% of the eligible, at risk population yearly, for at least 5 years, in order to interrupt transmission and prevent children from becoming infected.” The window of opportunity for collaboration between MDA and malaria control programs is therefor, very focused.

A smaller scale study reported in July of this year found that, “In mosquitoes feeding on volunteers given ivermectin the previous day, mean survival was 2.3 days, compared with 5.5 days in the control group (P < .001, by log-lank test). Mosquito mortality was 73%, 84%, and 89% on days 2, 3, and 4 in the ivermectin group." Since ivermectin started as a drug for veterinary parasites, it is useful to note that similar results on mosquitoes were found after cattle were given ivermectin. Researchers from Michigan State University* reported that, "Most (90%) of the An. gambiae s.s. that fed on the ivermectin-treated cattle within 2 weeks of treatment failed to survive more than 10 days post-bloodmeal. No eggs were deposited by An. gambiae s.s. that fed on ivermectin-treated cattle within 10 days of treatment." The authors concluded that, "Treatment of cattle with ivermectin could be used, as part of an integrated control programme, to reduce the zoophilic vector populations that contribute to the transmission of the parasites responsible for human malaria." community-ivermectin-distribution-in-buea-cameroon.jpgIvermectin distribution of course has been the major strategy of the the African Program for Onchocerciasis Control (APOC) for the past 15 years.  APOC’s efforts will continue much longer than those of lymphatic filariasis in over 100,000 communities throughout the continent.

More attention to joint planning and coordinating of malaria and other disease control efforts should be synergistic and mutually beneficial for the populations, who according to APOC, live beyond the end of the road.

*http://www.ingentaconnect.com/content/maney/atmp/2009/00000103/00000006

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