A tube latex agglutination test for the diagnosis of malaria

Abstract

Latex particles were coated with serum or erythrocytic antigens obtained from chickens acutely infected with Plasmodium gallinaceum. A suspension of the coated particles was used as an agglutinogen in a tube latex agglutination (TLA) test. Detectable antibodies against both antigens were found in the sera of infected chickens approximately 10 days after infection; a maximal titre of 1 : 640 was reached 2 months later and titres of 1 : 20 to 1 : 160 persisted for the remaining several months of observation. The persistence of serum agglutinins was correlated with the carrier stage of the infection as was revealed by subinoculating homogenates of brains from serologically positive chickens into susceptible chickens. The serum antigen, but not the erythrocytic antigen, was also found useful in detecting and titrating antibodies to heterologous plasmodial species. By using serum antigens of chicken origin in the TLA test it was possible to reveal reactions with sera of human beings infected with P. falciparum, P. vivax, P. malariae and P. ovale; monkeys infected with P. knowlesi and P. cynomolgi; and rats infected with P. berghei. The appearance and persistence of agglutinins in these species was independent of the presence of detectable parasitaemia. Sera from uninfected representatives of the above host species did not react with the TLA test with either of the antigens, nor were non-specific reactions observed in the test of sera from patients infected with Treponema pallidum, babesial and leptospiral organisms. On the basis of preliminary studies it appears that the TLA test with antigens of avian origin can be used to diagnose human malaria. It is suggested that the test be extended to include the use of serum antigens from simian and other malarias. Unique advantages of the TLA test are its simplicity and dependability, the stability of its reagents, the minimal amount of laboratory equipment and supplies required and the ready availability and inexpensiveness of the antigen.