Search

In 1992, the prevalence of hepatitis B virus (HBV) markers was evaluated in 1004 subjects aged one to 76 years living in urban and rural areas in Tanzania. The overall prevalence rates of hepatitis B surface antigen (HBsAg) and of any HBV marker were 4.4% and 37.0%, respectively. No statistically significant difference by sex was found. The HBsAg prevalence among pregnant women was 4.3% (20/463). The proportion of HBeAg positive among HBsAg positive pregnant women was 10% (2/20). The HBsAg age-specific prevalence was 2.1% in the 1-5 year age-group; peak prevalence (12.1%) occurred in the 6-15 year age-group. Markers of HBV infection were 4.1% by age five years; they increased with advancing age (P < 0.01). Subjects residing in urban areas had statistically significant higher HBV exposure than those residing in rural areas (43.9% vs 27.4%, P < 0.01). Subjects belonging to the largest family size (seven or more members) showed increasing risk (OR 2.9; 95% CI = 1.96-4.28) of HBV exposure. Because maternal HBV transmission early in life appears to be of minor impact and children are mostly infected later in infancy, HBV vaccination at birth is not indicated, while vaccination of all infants at 2-3 months of age with other paediatric vaccinations is the first priority.

The chemical composition of the stomach contents and the digestibility of organic matter, proteins and energy of three planktivorous fish species (Oreochromis niloticus, Sarotherodon galilaeus and Citharinus citharus) were studied in Batamani Pond (Mali, West Africa) during the dry and wet seasons. The diet contents of O. niloticus and S. galilaeus presented high levels of organic matter and proteins during the wet season (ash-free dry weight (AFDW): 753 mg.g(-1) dw and 703 mg.g(-1) dw, protein contents: 479 mg.g(-1) AFDW and 449 mg.g(-1) AFDW, respectively). In the dry season, the chemical composition of the food was characterized by high proportions of inorganic material (73% and 68% for O. niloticus and S. galilaeus, respectively). The chemical composition of the food of C. citharus was characterized by low seasonal variation. The levels of AFDW (396-461 mg.g(-1) dw) and proteins (65-86 mg.g(-1) AFDW) in its diet were generally low, reflecting a high proportion of mineral content. During the wet season, the digestibility of AFDW (52% and 58%), total amino acids (68% and 76%) and energy (63% and 56%) increased significantly for O. niloticus and S. galilaeus, respectively. Nutrient and energy digestibility for C. citharus showed no significant seasonal variations (AFDW: 36-45%; total amino acids: 57-64%; energy: 31-39%). The marked seasonal character of the pond, in terms of both hydrology and trophic conditions, had a low impact on the availability and quality of nutritive resources for the two tilapia species O. niloticus and S. galilaeus, while C. citharus appears to have the capacity to adapt its regime to the available food quality, whatever the season.