Studies on the life history and natural transmission of Plasmodium circumflexum kikuth, 1931

Meyer, Clinton Louis (1974) Studies on the life history and natural transmission of Plasmodium circumflexum kikuth, 1931. Masters thesis, Memorial University of Newfoundland.

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Abstract

A two year study was undertaken in 1972 to investigate various aspects of the epizootiology of Plasmodium circumflexum and other avian malarias in waterfowl on the managed wetlands of the Tantramar Marshes, New Brunswick. -- Mosquito studies provided information on 14 species of potential vectors, many of which were eliminated from consideration as vectors of avian malaria on the basis of their bionomics. Anopheles earlei, Culex restuans, C. territans, Aedes dorsalis, Ae. cinereus, Ae. fitchii, Ae. aurifer, Ae. excrucians, Ae. c. canadensis and Ae. punctor were captured only a few times in the baited traps and are not considered as potential vectors of avian malaria. Culiseta morsitans, Mansonia perturbans, Anopheles walkeri and Aedes cantator engorged frequently on bait birds and were considered as potential vectors. -- The strains of P. circumflexum and P. polare used in these experiments were isolated from Aix sponsa and Anas discors respectively. Thereafter they were maintained by blood transfers in hatchery-bred white Pekin ducklings (Anas boschas). Traps baited with infected ducks were set on the shore of Front Lake, Long Lake and in adjacent wooded areas in the late afternoon; mosquitoes were collected the following morning. In 1973, 7,235 female mosquitoes of which approximately 30 percent were engorged were collected in the traps. Overall mosquito abundance was noted to reach a peak in early July; Mansonia perturbans occurred in very large numbers. -- Dissection of mosquitoes from trap collections indicated a natural sporozoite rate of about 9 percent (7 of 75 dissected) in Culiseta morsitans. No natural infections were noted in other mosquito species dissected. -- Dissection of Anopheles walkeri and Aedes cantator which had experimentally fed on P. circumflexum and P. polare infected ducks show that these mosquitoes are refractory. Sporogony of both P. circumflexum and P. polare was observed in Mansonia perturbans but the one attempt to transmit P. polare via this mosquito was unsuccessful. Culiseta morsitans was shown to be susceptible to P. polare. Sporogony and transmission of P. circumflexum to waterfowl was achieved via Culiseta morsitans. Three of 10 attempts to transmit P. circumflexum via intraperitoneal inoculation of sporozoites from C. morsitans were successful. Prepatent periods of 14 and 19 days in ducklings and 31 days in a gosling were recorded. -- The course of P. circumflexum sporogony in C. morsitans was studied. Growth of the oocysts at an ambient temperature is fairly regular with sporozoites appearing in the salivary glands on the 8th post infection day. -- Laboratory study of the asexual cycle of P. circumflexum in a white China gosling indicates no periodicity is present and only slight variations in the numbers of different stage parasites are observed. A short term of infection and low parasitemia appears characteristic for P. circumflexum. -- The evidence indicates that Culiseta morsitans is a natural vector of P. circumflexum in the Tantramar area and while Mansonia perturbans may be a useful experimental host, there is no evidence it is a natural vector.

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