Serologic tests with malaria parasites are basically epidemiologic tools and not specific enough to be used for diagnostic purposes. The fluorescent antibody technique has been used to measure the presence of antibodies to P. ovale. However, extensive studies have been limited due to limited availability of the antigen. The pattern of fluorescence for P. ovale was similar to that of P. malariae (26). In a study with patients that had induced infections with P. falciparum, P. malariae, and P. ovale, antibodies to P. ovale persisted for a period of 6 years after treatment (28). Meuwissen found a high degree of cross-reactivity of sera from patients with P. ovale infections and the monkey malaria parasite P. fieldi (72). In a later study, it was shown that such antisera also cross-reacted to P. cynomolgi bastianellii, but at a lower level than the homologous antigen or P. fieldi (73).
In an initial field study with 498 sera collected from Nigerians, 22.3% had positive responses to P. ovale (27). A serologic survey was conducted in Ethiopia using a strain of P. ovale from Ghana as the antigen (30). Maximum responses were highest to P. falciparum (45%), followed by P. ovale (41%), P. malariae (36%), and then, P. vivax (9%); this included individuals in whom maximum responses were equal for some species of Plasmodium. An indirect fluorescent antibody study was subsequently conducted to evaluate patterns of antibody response in remote populations of the New Hebrides, Solomon, and Western Caroline islands and New Guinea (13). Maximum titers to P. ovale occurred most frequently in the eastern and southern Solomon Islands, although P. ovale had never been reported in either the New Hebrides or Solomon islands. In West New Guinea (Irian Jaya) and Papua New Guinea, serologic responses were highest to P. falciparum, followed by P. ovale, P. malariae, and P. vivax, a pattern similar to that observed in the survey of samples from Ethiopia.
A serologic survey of urban and rural populations of Ghana indicated the proportion of positive titers against P. falciparum rose rapidly with age, with more than 50% of children 1 to 2 years old being positive (35). In comparison, titers against P. ovale rose more slowly, reaching 50% in the 7- to 8-year-old group. A survey was also made of a remote population living in the Star Mountains in the Western Province of Papua New Guinea (22). Highest responses were to P. falciparum, followed by P. malariae, P. vivax, and P. ovale; here, only 5 of 614 samples examined had the highest titers to P. ovale.
Answers to all your Biology Questions
