Simian Malaria in Man

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  • U. S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Laboratory of Parasite Chemotherapy, Bethesda, Maryland


Anopheles quadrimaculatus and A. freeborni mosquitoes which had acquired their infection from monkeys infected with Plasmodium cynomolgi bastianellii were allowed to bite 7 Negroes and 13 white inmate volunteers. No volunteer received less than 25 infected bites. Observations were as follows: (1) parasitemia of low density was demonstrable in 12 of the 13 white subjects; (2) the prepatent period ranged from 15 to 30 days with an incubation period of 15 to 23 days; and (3) parasitemia was not demonstrated in any of the Negroes, although 3 exhibited signs and symptoms referable to malaria.

Of the 20 volunteers, 16 exhibited clinical responses with oral temperatures over 100°F, enlarged tender liver or spleen and other symptoms graded from moderate to severe. Two exhibited temperatures under 100°F with mild symptoms, and two were asymptomatic. The most frequent symptom was headache followed in decreasing frequency by anorexia, abdominal pain, joint pain, nausea, myalgia, vomiting, chest pain, chills, and cramping. The most significant physical findings were splenomegaly and hepatomegaly which appeared early in the infection and were transitory. In general, this disease was more benign than that generally encountered in vivax although the severity of the symptoms appeared out of proportion to the parasitemia.

Man to man transfer of infection with P. c. bastianellii was accomplished by allowing A. freeborni infected on man to feed on two human subjects. Each subject developed symptoms referable to malaria and one developed patent parasitemia on day 107. On that day blood transferred to another volunteer and to an uninfected rhesus monkey resulted in an infection in each. Blood transferred to man and to monkeys prior to day 107 gave negative results.

The results reported in this paper show that P. c. bastianellii qualifies experimentally as a zoonosis. In addition, we have demonstrated that man-mosquito-man transfer can also occur. Whether these findings will be significant in terms of malaria eradication will only be determined by further investigations.

Author Notes

Present address: University of Miami School of Medicine, Jackson Memorial Hospital, Miami, Florida.