Asymptomatic Malaria Infection and Their Antibodies Against Malaria: A Study in Abra de Ilog, Occidental Mindoro, Philippines

Human malaria, caused by four species of Plasmodium, namely P falciparum, P vivax, P malariae, and P ovale, remains a health problem of global concern, with one to two million deaths annually and risking about two billion people worldwide. Alternative ways of controlling the incidence of malaria through understanding the host’s immune response to monoinfection and the detection of the presence of asymptomatic malaria infection are the factors being addressed in this study. The determination of the possible existence of cross-antigenic stimulation is a matter of great significance for future research and development. The isolation of these antigenic structures may give the first step to the development of better vaccines that may protect the general population who are at risk of developing malaria. Prior to blood collection, a memorandum of agreement was signed between the researcher and the Iraya-Mangyan leaders of Abra de Ilog, Occidental Mindoro. A Certificate Precondition was issued by the National Commission of Indigenous Peoples, which was required by the Graduate School Ethics Review Committee. Determination of the presence of malaria parasite on blood samples of residents of two barangays in Abra de Ilog, Occidental Mindoro, was performed using two methods: microscopic examination of stained blood smears for the presence of malaria parasite and polymerase chain reaction. Blood smears were prepared and eventually stained using Giemsa and Dip Quick stains. The detection of 5 positive cases of malaria infection with ring/schizont stage among the 53 cases was a clear indication of positive asymptomatic cases. Nested PCR using Plasmodium spp.–specific primer as well as P falciparum–specific and P vivax–specific primers showed the absence of bands so that one of the recommendations in this study is the performance of real-time PRC using more sensitive primers. Levels of P falciparum and P vivax–specific immunoglobulin were measured using an enzyme-linked immunosorbent assay revealing a higher level of PF-specific IgG than PV-specific IgG. Whole blood samples were saved for future determinations such as real-time PCR, immunophenotypic analysis, and possible parasitic culture. Further similar studies may also be done by increasing the number of respondents as well as the areas of concern for a more extensive scope.