Transmission of Three Strains of Plasmodium falciparum from Monkey to Man

Abstract

Infections of 3 different strains of Plasmodium falciparum in the Aotus trivirgatus monkey were shown to be infectious to 6 different species of Anopheles. The A. freeborni were more readily infected. Transmission of the infection to 20 men was obtained by the bites of infected A. freeborni mosquitoes after extrinsic incubation periods of 13 to 26 days. The prepatent periods in the men ranged from 9 to 13 days with a mean of 11.2 days. It has been reported previously that human malaria in the Aotus trivirgatus monkey is infectious to mosquitoes and that the infections can be subsequently transmitted back to man. Five different strains of Plasmodium vivax, all from Central America, have been transmitted from these monkeys to man via the bites of infected Anopheles albimanus and A. freeborni mosquitoes (Young et al., 1966; Collins et al., 1972). Previously, we had reported the successful transmission of the Malayan IV strain of P. falciparum to two human volunteers (Contacos and Collins, 1968; Collins et al., 1968). Reported here are the results of additional studies on the transmission of three strains of P. falciparum from Aotus monkey to man. MATERIALS AND METHODS The 3 strains of P. falciparum used were (1) the Malayan IV which was isolated from a Peace Corps volunteer who contracted the infection while working in the Central Perak area of Peninsula Malaysia (Chin et al., 1966), (2) the Cambodian I which was isolated from an American parasitologist who contracted the infection while working in the Paillin District of Western Cambodia (Eyles et al., 1963), and (3) the Panama II which was isolated from an 11-year-old Panamanian national residing on the Atlantic side of the Republic of Panama (Collins et al., 1973). The Malayan IV and the Panama II strains have been shown to have some degree of resistance to Received for publication 14 May 1973. * National Institutes of Health, LPD, Building 5, Room 114, Bethesda, Maryland 20014. t Center for Disease Control, Malaria Program, 1600 Clifton Road, Atlanta, Georgia 30333. Mayo Clinic, 4023-18th Avenue, N.W., Rochester, Minnesota 55901. chloroquine. The Cambodian I strain is sensitive to this drug. Aotus trivirgatus monkeys, obtained commercially, had their origin in Colombia, South America. Prior serologic and parasitologic examination indicated that the animals were free of natural malarial infection. The A. freeborni mosquitoes were the F-l strain originally isolated from Marysville, California (Hardman, 1947) and maintained in our laboratory since 1944. The A. maculatus were obtained from the Institute for Medical Research, Kuala Lumpur, Malaysia (Ow Yang et al., 1963) in 1964 and maintained in our laboratory since then. The A. quadrimaculatus were the Q-1 strain which was obtained from Technical Development Laboratories, CDC, Savannah, Georgia, and maintained in our laboratory since 1959. The A. stephensi were from Delhi, India, and were obtained from the London School of Hygiene and Tropical Medicine, London, England, in 1963. The A. balabacensis balabacensis were originally from Thailand and obtained from the Walter Reed Army Institute of Research, Washington, D. C. (Esah and Scanlon, 1966). Three strains of A. albimanus were examined. Two, the Apastepeque and the Melara strains, were established in El Salvador by the Central America Malaria Research Station, CDC, San Salvador, El Salvador; we obtained the colonies from them in 1971. The other strain of A. albimanus was the A-1 strain from Panama which was obtained from the Gorgas Memorial Laboratory in 1972. This study was performed in prisoner volunteers at the Atlanta Federal Penitentiary as part of a research program on evaluation of antimalarial drugs. The technique used for the feedings on the monkeys and on the human volunteers are those previously reported (Collins et al., 1968).