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The importance of carbohydrate moieties for the antigenicity of purified soluble Plasmodium falciparum antigens from the asexual blood stage was tested. Digestion of the soluble antigens with alpha-D-galactosidase clearly affected the ability of the antigen to react with malaria-immune sera from different geographical origins in crossed immunoelectrophoresis and immunoblotting. Antigens of 220, 180, 80, and 74 kilodaltons were affected by the enzyme treatment. Furthermore, the enzyme digestion reduced the ability of the purified soluble antigen to stimulate lymphocytes from malaria-immune donors. The results might have important implications for the strategy of developing a malaria vaccine.

This report presents results from a sample survey designed to investigate the possible role of Cryptosporidium spp. in childhood diarrhea in a developing country, Liberia, West Africa. During the four months of January to April 1983, a house-to-house study was carried out in two geographically and socially different communities--an urban slum and three rural villages. Stool samples from 374 children, aged 6 to 59 months, were tested for Cryptosporidium spp. Among the children with diarrhea 8.4% were Cryptosporidium spp. positive compared with a prevalence rate of 5.9% in asymptomatic children. Of the children living in a household with a Cryptosporidium spp.-positive index child, 8.6% had a positive stool sample. Of all children attending a clinic because of diarrhea, 14.6% were Cryptosporidium spp. positive. Cryptosporidiosis was more frequent in younger children; 24 of the total of 29 positive cases (83%) were below 2.5 years old. Actual or previous bottle feeding (formula) was a risk factor, particularly in children below 18 months old. Of the bottle-fed children, 28% were Cryptosporidium spp. positive versus 9.1% of children never bottle fed. Crowding is another possible risk factor. The prevalence of cryptosporidiosis was 13.5% in big urban households with more than 10 children, whereas the prevalence in the small urban households was 6.1%. Ethnic and religious differences were particularly evident in the rural area. No Muslim households had cryptosporidiosis, whereas the prevalence in non-Muslim tribes was 9%. The general belief that cryptosporidiosis is primarily a zoonosis is questioned in this study, partly because many carriers and asymptomatic household contacts were found.

In a community based prevalence study of HIV infection in Bissau, West Africa, 1987, the population in 100 randomly selected "houses" was asked to participate. 89% (1329/1499) were examined and had a blood sample taken. None was HIV-1 seropositive but 4.7% were seropositive for HIV-2 (0.6% in children, 8.9% in those aged 15 years and over, and 20% in those aged 40 years and over). There was no significant difference in seroprevalence between areas or ethnic groups or between individuals of different civil status when age was taken into account. Sexual contact and blood transfusions were the dominant transmission routes, and no case of vertical transmission was identified. The HIV-2 seroprevalence in spouses of HIV-2 seropositive index persons was 40%. For a history of blood transfusion the relative risk of being HIV-2 seropositive was 103.6 in children and 2.4 for adults. After exclusion of spouses, no clustering of HIV-2 seropositivity was seen. At follow-up, after a mean observation time of 325 days, there was an excess mortality for HIV-2 seropositives. The relative risk of dying for HIV-2 seropositive children was 60.8 and for adults 5.0.

Campylobacter was the bacterial pathogen most prevalent in 859 children, aged 6-59 months, examined in a house-to-house diarrhoea survey in two Liberian communities. 44.9% of the children from an urban slum and 28.4% from a rural area were excretors. Since the prevalence of diarrhoea was very high and consequently many convalescent carriers were found, it was not possible to evaluate the pathogenic role of campylobacter. The excretor rate increased with age and was significantly correlated to the use of supplementary feeding, inversely correlated to the quality of the water supply, and also associated with helminthic infestation. Results from re-examination of 172 children suggested a high intensity of transmission. The findings all indicate the existence of a heavy environmental contamination with campylobacter, probably of both human and animal faecal origin.