A retrospective examination of the effect of fever and microgametocyte count on mosquito infection on humans infected with Plasmodium vivax.

A retrospective examination was made of archival data collected between 1940 and 1963 on the infection of mosquitoes with the St. Elizabeth strain of Plasmodium vivax. Patients were undergoing malariatherapy for the treatment of neurosyphilis. A total of 845 lots of Anopheles quadrimaculatus mosquitoes were fed during primary infections and 76 during secondary infections. Average percentage infection during the primary infection was 56.55% versus 49.83% during the secondary infection. There appeared to be no relationship between microgametocye density, asexual parasite count, and percentage infection. However, very high fevers appear to have a significant effect on infection rates. Persons with fever > or = 105 degrees F showed the lowest rates of infectivity regardless of parasitemia; persons with moderate (101-104.8 degrees F) fever produced somewhat higher rates, and persons with no fever had the highest levels of infection at all parasitemia levels greater than 1,500/microL