Sera from individuals infected with Plasmodium vivax were tested for the presence of malarial antibodies using the indirect fluorescent antibody (IFA) and the indirect hemagglutination (IHA) tests. The primary infection resulted in the conversion of all sera to a positive response in the IFA test, whereas only 50% gave a positive IHA response. There was a direct relationship between the duration of the primary parasitemia and percentage giving positive IHA response. Relapse resulted in high level positive IFA and IHA responses.
Present address: Vector Biology and Control Division, Bureau of Tropical Diseases, Center for Disease Control, Atlanta, Georgia 30333.