Indigenous weaning foods: Hygiene and diarrhoeal diseases in rural Ethiopian setting, Jimma Zone

Abstract: A community based Microbiological study of Weaning Foods was conducted from Nov. 1994 to August 1995 in six Peasant Associations, in Jimma Zone, South West Ethiopia. The results of the study indicate that infants and children in the study community are ingesting highly contaminated foods. Fifty five percent of the weaning foods harbored bacterial counts over 2x106/ml of samples, and coliform bacteria were isolated from over 50% of these foods. The invariably high contamination of weaning foods was significantly associated with unsafe water supply, storage at ambient temperature for long time, unsatisfactory methods of cleaning feeding utensils. Poor domestic and personal hygiene observed in the households surveyed could provide ample opportunity for communication of fecal organisms to food and water either directly or indirectly. There was no statistically significant association between bacterial contamination of weaning foods and diarrhoeal episodes in children (P> 0.05). Educating the rural community, and improving over all hygienic conditions in the home environment is crucial for improving food hygiene and reduce the risk of diarrhoea from contaminated foods. [Ethiop. J. Health Dev. 1997;11(2):149-156

Isolation and characterization of Bacillus thuringiensis from soils in contrasting agroecological zones of Ethiopia

Phenotypic and molecular methods were used to isolate and characterize B. thuringiensis from diverse agro-ecological zones of Ethiopia. Bioassays were used to test the insecticidal activity of B. thuringiensis strains against the major malaria vector, Anopheles arabiensis (Diptera).  B. thuringiensis were isolated from 32% of the total 503 soil samples collected from the 16 agro-ecological zones. All sequenced isolates were 99%–100% identical to each other and to B. thuringiensis entries in Genbank. B. thuringiensis with similar 16S rRNA gene sequences from these different zones were characterized with regard to maximum growth rate and temperature optima for growth to test if there was local adaptation in these functional traits. The result showed a narrow temperature range around 30°C for maximal growth rate, and there were no significant differences between agro-ecological zones. Of 110 Bacillus thuringiensis isolates analyzed for the presence of crystal protein genes,  7 tested positive for cry 4, cry 11, and cyt toxin genes. Sequencing of these genes in positive strains demonstrated 99–100 % homology to known mosquitocidal cry and cyt genes in Bacillus thuringiensis subsp. israelensis. The present study shows that this biotechnologically important species is wide spread in Ethiopian soils and that it does not demonstrate local adaptation to temperature regimes, at least not for basic functions such as growth-temperature response. Our finding also pointed the potential for exploiting this species in vector control programs.

Frequency and distribution of Bacillus Thuringiensis from Ethiopian soils

Search for B. thuringiensis with novel crystal proteins and effectiveness against insect pests from soils and other environments is underway worldwide. In the present study, B. thuringiensis were isolated from various agro-ecological soils of different zones in Ethiopia and larvicidal activity of isolates was determined using insect bioassay. Of the 503 soil samples examined, 32% yielded B. thuringiensis. B. thuringiensis was found to be distributed in all the studied agro-ecological soils. Tepid to cool semi-arid lakes and rift valley soils yielded B. thuringiensis more frequently, followed by cold to very cold sub-humid afroalpine and hot to warm perhumid lowlands. On the other hand, B. thuringiensis was least frequent in soils from hot to warm moist lowlands and hot to warm sub-moist midhighlands. It was also shown that vegetative cover influences the distribution of the bacteria in the soil. Two hundred and thirteen B. thuringiensis isolates were tested for larvicidal activity against An. arabiensis (Diptera) and Plutella xylostella (Lepidoptera) larvae. Of the tested isolates, 44 (21%) killed 50-100% of An. arabiensis larvae within 48 hours. Isolates that killed 100% larvae within 24 hours were all from tepid to cool moist midhighland soils whereas those which killed 100% larvae within 48 hours were from three other different agro-ecological soils. None of the 110 B. thuringiensis strains tested against Plutella xylostella larvae showed any larvicidal activity. Keywords/phrases: Agro-ecological soil, Anopheles arabiensis, Bacillus thuringiensis, Frequency of isolation, Larvicidal property, Plutella xylostella Ethiop. J. Biol. Sci., 7(1): 55-67, 200