The epidemiology of Plasmodium falciparum malaria in two Cameroonian villages: Simbok and Etoa.

In support of ongoing immunologic studies on immunity to Plasmodium falciparum, demographic, entomologic, parasitologic, and clinical studies were conducted in two Cameroonian villages located 3 km apart. Simbok (population = 907) has pools of water present year round that provide breeding sites for Anopheles gambiae, whereas Etoa (population = 485) has swampy areas that dry up annually in which A. funestus breed. Results showed that individuals in Simbok receive an estimated 1.9 and 1.2 infectious bites per night in the wet and dry season, respectively, whereas individuals in Etoa receive 2.4 and 0.4 infectious bites per night, respectively. Although transmission patterns differ, the rate of acquisition of immunity to malaria appears to be similar in both villages. A prevalence of 50-75% was found in children < 10 years old, variable levels in children 11-15 years old, and 31% in adults. Thus, as reported in other parts of Africa, individuals exposed to continuous transmission of P. falciparum slowly acquired significant, but not complete, immunity.

Reduced levels of chloroquine resistant Plasmodium falciparum in selected foci of the South West Province, Cameroon.

OBJECTIVES: To evaluate the state of chloroquine resistant malaria in the South West Province of Cameroon. To estimate the prevalence of different species of Plasmodium in the area. DESIGN: A cross sectional study. SETTING: South West Province of Cameroon. SUBJECTS: 326 febrile patients. MAIN OUTCOME MEASURES: Chloroquine resistance studies using the WHO seven-day standard in vivo test. Speciation of malaria by polymerase chain reaction. Prevalence of falciparum malaria by light microscopy of thick blood smears. RESULTS: Prevalence of chloroquine resistance ranged from 4.3 to 13.2%. A total of six cases showed RIII resistance, and three cases showed RII resistance. Plasmodium falciparum was the predominant species, 96.8% of those testing positive for P. falciparum, 6.3% of cases showed mixed infections of P. falciparum and P. malariae. P. ovale accounted for 3% of cases. CONCLUSION: P. falciparum resistance to chloroquine may not be on the increase compared to earlier reports from the South West Province. The results have important implications in treatment of malaria in view of the low cost of chloroquine.

Detection of the Plasmodium falciparum antigen histidine-rich protein 2 in blood of pregnant women: implications for diagnosing placental malaria.

Pregnant women have an increased susceptibility to infection by Plasmodium falciparum. Parasites may be present in the placenta yet not detectable in peripheral blood smears by routine light microscopy. In order to determine how frequently misdiagnosis occurs, peripheral blood and placental samples were collected from 1,077 Cameroonian women at the time of giving birth and examined for the presence of malarial parasites by using light microscopy. Results showed that 20.1% of the women who had placental malaria were peripheral blood smear negative. Thus, malarial infection was not detected by microscopic examination of peripheral blood smears from approximately one out of five malaria-infected women. Since P. falciparum parasites secrete histidine-rich protein 2 (HRP-2), we sought to determine if detecting HRP-2 in either peripheral plasma or whole blood might be used to diagnose the presence of parasites "hidden" in the placenta. Samples of peripheral plasma from 127 women with different levels of placental malarial infection were assayed by HRP-2-specific enzyme-linked immunosorbent assay. HRP-2 was detected in 88% of the women with placental malaria who tested negative by blood smear. Additionally, whole blood was obtained from 181 women and tested for HRP-2 with a rapid, chromatographic strip test (ICT). The ICT test accurately detected malarial infection in 89.1% of P. falciparum-infected women. Furthermore, 94% of women with malaria were accurately diagnosed by using a combination of microscopy and the ICT test. Thus, detection of HRP-2 in conjunction with microscopy should improve diagnosis of malaria in pregnant women.