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An epidemiologic survey on malaria endemicity levels, including entomologic, parasitologic, and immunologic indicators, was carried out in a village of the Madagascar highlands (Analaroa) at the end of the 1990-1991 rainy season. The results indicate that malaria is hyperendemic and Anopheles funestus is the main vector in the area. The prevalence of parasitemia decreased with age from a maximum level of about 60% in children less than five years of age to a minimum of about 16% among those more than 29 years of age. The prevalence of Plasmodium falciparum circumsporozoite antibodies (Ab-Cs) increased with age from a minimum level of about 10% in children less than five years of age to a maximum of 71.7% among those more than 29 years of age. An inverse correlation was observed between P. falciparum prevalence and levels of Ab-Cs and parasite prevalence. The study confirmed that prevalence and Ab-Cs levels are reliable indicators of malaria endemicity in hyperendemic areas. Schoolchildren between five and 14 years of age are considered the most practical and susceptible group for this kind of epidemiologic study.

Recently, we demonstrated that immunological castration of male mice can be obtained by immuninization with Luteinizing Hormone-Releasing Hormone (LH-RH) directly coupled to NAcMur- L -Ala- D -isoGln- L -Lys (MDP-Lys) without carrier and Freund's Complete Adjuvant (FCA) but in the presence of Polyvinyl-Pyrrolidone (PVP). In the present report, we have observed that: (a) immunization by the conjugate, LH-RH-MDP-Lys, was very effective even in absence of PVP, and this conjugate was more active than other conjugates containing MDP coupled to LH-RH fragments; (b) a strong secondary response could be observed by the administration of free LH-RH suggesting that the endogenous secretion of LH-RH might elicit a boosting effect; (c) administration of MDP-Lys coupled to LH-RH decreased the pyrogenicity of the glycopeptide; (d) such a conjugation also decreased the hormonal activity of the antigen although it enhanced its immunogenicity. These results show that a conjugate (2000 dalton) of a decapeptide hormone with a synthetic adjuvant glycopeptide can induce immunological castration in mice after administration in saline. The immunopharmacological properties of the conjugate and its conditions of efficacy suggest that such an approach could find clinical application.