Prevalence and associated health risks of escherichia coli 0157:in urban smallholder dairy farming and non-dairy farming households in Dagoretti, Nairobi
A prevalence study of E.coli 0157:H7 was done amongst smallholder dairy farming and neighbouring non-dairy households in Dagoretti Division of Nairobi city, to determine the herd prevalence of E.coli 0157:H7, and to assess potential exposure pathways to household members. Two hundred and ninety smallholder dairy farmers and 136 neighbouring non-dairy farmers were interviewed. Several exposure pathways were assessed: (a) use of cattle faeces as manure (fertilizer) on farms, (b) consumption of raw vegetable salads (c) consumption of fermented (soured) raw milk, (d) Consumption of raw milk, (e) Household water source (f) water treatment (g) Handling of cattle faeces without protective gloves. The households were also interviewed on basic household characteristics such as (a) level of education for the household head (b) household land size (c) number of years lived in the location (d) number of members in a household. Community workshops and gender disaggregated focus group discussions were organised within the division. Proportional scoring was done by men and women on daily activities that are potential exposure factors in a dairy farming household. Cattle faecal and milk samples were used for culture and isolation of E.coli 0157: H7. Colonies of E.coli were isolated using standard microbiological methods. E.coli positive isolates were serotyped with 0157 antiserum and polymerase chain reaction done to detect genes coding for Verotoxin production. Hired male worker spends over 50% of his daily time doing dairy related activities. Seventy three percent of the dairy farming households were using cattle faeces as manure on vegetable farms, 85% were not using protective gloves while handling manure. Fifty three percent were consuming raw vegetable salads not washed in clean water. Twenty one percent were consuming fermented raw milk and 4% of both the dairy farming and non-dairy farming households were not boiling the milk and were therefore at risk of infection. Ninety six percent of both dairy and non-dairy households mitigated the risk of infection by boiling the raw milk before consumption, while household drinking water was boiled by 41% of the dairy farming and 47% of the non-dairy households. Other households also added chlorine to the drinking water (22.7% of dairy households and 6% of the non dairy households). Most of the households obtained water from the city council (78% dairy farming and 94.5% of non dairy households) which was considered to be chlorinated. Women had a lower level of education in both dairy and non-dairy households than men with an estimated proportions of (0.32; CI 0.219-0.436) for women having informal education compared to (0.11; CI; 0.07-0.16) for men in dairy households and a proportion of (0.04, 0.02) for women and men, respectively, in non-dairy households. Male headed dairy households also had a higher estimated proportion of secondary level of education (0.30; CI; 0.24-0.36; P<O.OOOl). There were 15 faecal E. coli 0157 sample isolates from dairy farming households and 3 milk E. coli 0 157 sample isolates from non-dairy households that agglutinated with the antiserum against 0157. Only one faecal E.coli 0157 isolate had genes for verotoxin 1 production. Of the 18 E.coli 0157, sample isolates 27.7% were resistant to Sulphamethoxazole and 11.1% to Tetracycline. The isolate that was amplified by primers of E.coli 0157:H7 on polymerase chain reaction was however sensitive to all the antimicrobials. The apparent prevalence of E.coli 0157 in cattle faeces and milk was determined as 5% (Cl; 3-8) and 2% respectively. However, the apparent herd prevalence of E.coli 0157:H7 was less than 2%. The study concluded that the risk of infection by E.coli 0157:H7 in urban dairy farming households was low, however, the presence of the E.coli 0157 at a prevalence of 5% indicates a potential health hazard because the E. coli 0157 can acquire the verotoxin producing gene by bacteriophage through conjugation. Therefore there is a need for continued surveillance to prevent any future outbreak in case the prevalence increases. The findings from this study and other studies on benefits of urban agriculture can be used by the policy makers to legalise urban dairy farming activities in Kenya.