Attack on the Vector of Filariasis in British Guiana

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Abstract
In British Guiana, during a study which began in April 1961, Wuchereria bancrofti was the only filarial parasite found to be causing elephantiasis, and Culex pipiens quinquefasciatus was determined to be the primary vector. The parasite developed readily in Mansonia titillans and Anopheles aquasalis, which were found infected in nature, and they were considered secondary vectors. No Brugia malayi was found. In the coastal Buxton control area, 11 miles east of Georgetown, C.p. quinquefasciatus bred primarily in the dirty water of pit latrines and secondarily in the clean, confined water of drums and barrels near latrines. No breeding occurred in the relatively clean, open water of trenches, ditches, and drains. In an 18-month period, about 21,000 C.p. quinquefasciatus, mostly females, were collected from houses in 28 villages. About 40% were found resting on walls, 35% on clothing and other hanging objects, and 23.4% on or under furniture. On dissection of the naturally caught vectors, about 9% were found to have Wuchereria bancrofti parasites. About 0.5% had infective larvae in their bodies, but generally only 1 or 2 of these larvae were found per mosquito. C.p. quinquefasciatus, hatched in laboratory, were coated with metallic dust and released. Their flight range was determined to be one-half mile. Resistance of the adult vector to DDT and dieldrin was confirmed. Effective control was achieved by spraying 23 ounces of gas oil, as a residual larvicide, once a month on the surface of each latrine''s contents. Complete elimination of breeding in pit latrines resulted in an associative reduction of breeding in barrels and drums. Before larviciding was undertaken, the vector infection rate in some parts of the control area was as high as 54%. After 1 year of larviciding, this rate dropped to 4.7%.