Efficacy of permethrin-impregnated bed nets on malaria control in a hyperendemic area in Irian Jaya, Indonesia III. Antibodies to circumsporozoite protein and ring-infected erythrocyte surface antigen.

A two years intervention study was carried out using permethrin impregnated bed nets in a hyperendemic area, in Irian Jaya, Indonesia. To assess the influence of this intervention on natural immunity, concurrent immunological studies to determine levels of antibodies to the circumsporozoite (CS) and ring-infected erythrocyte surface antigen (RESA) proteins were conducted. Prevalence and titers of immunoglobulins (Ig)G and IgG subclasses were periodically measured in 138 individuals (30 children under the age of ten and 108 villagers ten years old and older). In the younger group, seropositivity of total IgG against CS fluctuated according to the parasite infection rates; however, IgG seropositive reaction against RESA gradually increased. In the older age group, seropositivity of both kinds of antibodies was stable during the whole study period. Nevertheless, the geometric mean titers of total IgG against CS and RESA were significantly reduced in this latter group in individuals who contained these antibodies before and after intervention. The geometric mean titer of IgG3 subclass against RESA was decreased at a highly significant level (p = 0.0005), and that of IgG4 against the same antigen was also decreased although to a lesser extent (p = 0.02).

Newly transmitted plasmodium falciparum malaria in the central highland plateaux of Madagascar : assessment of clinical impact in a rural community

Plasmodium falciparum has recently reappeared in the central highland plateaux of Madagascar. To define its role in the overall malaria pathology occurring during the rainy season, we conducted a clinical and parasitological study among the 2776 consultants of a malaria field health centre which we established in the middle of the transmission area. From January to June 1988 the overall parasite rate was 63.2% and did not vary with age; the overall splenic rate was 46.9%, decreasing in individuals over 15 years of age. After the beginning of the main transmission season, an increase in parasite rates and parasite densities was observed, while febrile illnesses associated with malaria parasitaemia decreased. During the second part of the rainy season the parasite densities started to decrease, while parasite rates and malaria-associated fevers remained at the same level. The frequency