Malaria merozoite surface protein 1 (MSP1) is cleaved in an essential step during erythrocyte invasion. The responses of children to natural malaria infection included antibodies that inhibit this cleavage and others that block the binding of these inhibitory antibodies. There was no correlation between the titer of the antibody to the 19-kDa fragment of MSP1 and its inhibitory activity. These findings have implications for the design of MSP1-based vaccines.

Objective: To determine the prevalence of asymptomatic malaria among prospective blood donors and its effect on some hematological parameters. Subjects and Methods: Six hundred sixty-eight seemingly healthy individuals (501 men and 167 women) ≧16 years of age and without clinical symptoms in Iwo, Southwestern Nigeria, were screened for this study. A sample of 5 ml of blood was drawn from each participant for examination of malaria parasites and a full blood count. Thick and thin Giemsa-stained blood smears were prepared for malaria parasite identification and quantification. Estimations of hematocrit, hemoglobin concentration, and platelet and leukocyte counts were made using an automated Coulter counter (STKS model). Results: Out of the 668 participants examined, 141 (21.1%) were positive for malarial parasitemia. The parasite rate was significantly higher in men (25.5%) than in women (7.8%) (χ² = 23.29, p < 0.001) and it was significantly associated with age (χ² = 33.69, p < 0.001). Parasitemic participants had significantly lower mean values of hematocrit, hemoglobin concentration, and total leukocyte and platelet counts compared to aparasitemic individuals (t = 3.5, p < 0.001; t = 2.0, p = 0.04; t = 4.4, p < 0.001, and t = 5.3, p < 0.001, respectively). A low platelet count (<150 × 10⁹/l) was significantly associated with malarial infection (OR 4.0; 95% CI 2.6–6.1). A person with a platelet count <150 × 10⁹/l was 4 times more likely to have asymptomatic malarial infection than one with a count ≧150 × 10⁹/l. Conclusion: Asymptomatic malaria is prevalent among blood donors in the study area and is associated with thrombocytopenia.

SummaryThe current status of urinary schistosomiasis was assessed in Ibadan, an urban community in south-western Nigeria. Of 1331 children examined for eggs of S. haematobium in their urine, 17.4% were infected. Prevalence in postprimary schoolchildren was significantly (P Ͻ 0.01) higher (22.4%) than in primary schoolchildren (12.0%). Intensity of infection based on geometric mean egg count per 10 ml of urine was also higher in postprimary (36.7 eggs/10 ml urine) than primary pupils (29.9 eggs/10 ml urine). Boys had a significantly (P Ͻ 0.01) higher infection rate (24.1%) than girls (8.5%), and the intensity of infection was also higher (P Ͻ 0.01) in males (39.0 eggs/10 ml urine) than in females (22.1 eggs/10 ml urine). The overall geometric mean intensity of infection was highest (38.8 eggs/10 ml urine) in the 11-15 years age group. 42% of infected children excreted Ͼ 50 eggs/10 ml urine. 2.2% excreted S. mansoni eggs in urine. Water contact activities were more frequent (P Ͻ 0.01) in males (31.8%) than females (38.2%). Nine species of snails were encountered, with B. (p) globosus being the the most abundant and widespread. These results show that urinary schistosomiasis is still being actively being transmitted in Ibadan.

The prevalence of urogenital schistosomiasis among pregnant women in Nigeria was high, with younger women and primigravidae at the greatest risk. These data can be used to develop a schistosomiasis control program among pregnant women in the study area.

Primary infections with Plasmodium yoelii and Echinostoma revolutum in the mouse induced a significant increase in the heterologous Schistosoma mansoni challenge worm establishment, whereas S. mansoni worm establishment remained unaffected by primary infections with Trypanosoma brucei and Babesia microti. Concurrent infection in the mouse with P. yoelii or T. brucei, but not with B. microti, blocked the resistance to homologous E. revolutum challenge infection, and primary P. yoelii and T. brucei infections and corticosteroid treatment made naive, innately resistant mice susceptible to E. revolutum infection. Innate resistance to infection with E. revolutum, the pattern of expulsion of low-level E. revolutum infections, and resistance to homologous S. mansoni challenge infection remained unaffected by concurrent B. microti infection. Primary, heavy E. revolutum infections in the mouse resulted in the enhancement of subsequent infection with B. microti, whereas primary infection with S. mansoni suppressed subsequent B. microti infection in some but not all experiments. In a single experiment, P. yoelii infection was suppressed markedly by primary S. mansoni infection, whereas the enhancement of P. yoelii infection in concurrently E. revolutum-infected mice was seen in only one of the several experiments conducted. However, no interference with resistance to homologous B. microti and P. yoelii challenge infection was induced by concurrent infection with S. mansoni and E. revolutum. We suggest that the synergistic interactions demonstrated between protozoans and helminths in concurrent experimental infection in the mouse are induced by immunosuppression.

Objective: To determine the effect of self-medication with chloroquine and pyrimethamine on malaria infection and anaemia during pregnancy. Subjects and Methods: The study involved 210 women who attended Ade Oyo Maternity State Hospital, Ibadan, Nigeria. Of these, 156 were pregnant women while 54 were not pregnant (controls). Of the pregnant women, 66 were primigravidae, while 90 were multigravidae. History of treatment of malaria with antimalarial drugs was obtained from the subjects. Gravidity and gestation period were also documented. Two millilitres of blood was withdrawn from each subject, for haematological parameters. Thin and thick films were prepared for malaria parasite identification and quantification. Results: Of the primigravidae and multigravidae 68 and 16.4%, respectively, had taken antimalarial drugs prior to booking. Among primigravidae, only18% of those with drugs compared with 32% without drugs were malaria-positive. The parasite density was significantly lower among those who took antimalarial drugs than among those who did not (976 ± 60 versus 2,421 ± 78, p < 0.05). Similarly, among multigravidae, only 16.4% of those who took antimalarial drugs compared with 34% of those who were not malaria-positive. The parasite density was also significantly lower in multigravidae with drugs than among those without drugs (350 ± 45 versus 1,000 ± 65, p < 0.05). The prevalence of anaemia (packed cell volume, PCV <33) was high, 89% in primigravidae and 70% in multigravidae. Severe anaemia (PCV <21) was more common in malaria-positive primigravidae and multigravidae than in malaria-negative women. Conclusion: The findings indicate that self-medication with chloroquine and pyrimethamine at booking was able to reduce the prevalence of malaria and anaemia in pregnancy.

Schistosoma transmission is influenced by the interplay between various factors ranging from parasite to host associated factors. While many studies have focused on mass chemotherapy to reduce transmission in other populations, no study has examined the impact of social factors that favour transmission in pregnant women in Nigeria. The study was conducted to assess the impact of knowledge, attitudes and sociodemographic factors on schistosomiasis burden in pregnant women of rural communities of Nigeria. A cross sectional community-based field study was conducted to assess the association between Schistosoma haematobium burden and the associated risk factors among pregnant women in rural endemic communities of Nigeria. Structured questionnaire was used to gather information on participants' socio-demographic data, knowledge on schistosomiasis and water contact activities. Of the 237 respondents examined microscopically for infection, 50 (21.1 %) were infected with overall mean infection intensity of 69.6 ± 165.2 eggs/ 10 mL urine. Multivariate logistic analysis showed occupation of the women to be associated with infection with the artisans having the highest risk (OR 3.34, CI 1.67-6.69, P = 0.022). Contact with water and water usage patterns are also associated with prevalence of disease with fetching (OR 2.04, CI 0.19-3.51, P = 0.003) and multipurpose water usage (OR 4.31,, P = 0.0002) being the most predisposing variables respectively. Awareness about water borne diseases showed no association with infection (P = 0.382) with typhoid (23.7 %) and fever (2.6 %) constituting the most and least common water borne diseases mentioned by the women. Health education and provision of good water supply should be integrated into the control strategies in order reduce transmission in endemic areas.

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