Risk of contamination of cattle carcasses with Escherichia coli O157 from slaughterhouses in Nairobi, Kenya
The study was carried out in three abattoirs supplying meat to butcheries in Nairobi and its environs. The objectives ofthe study were to assess the level of contamination of carcasses with Escherichia coli 0157 in the slaughterhouses, determine the critical control points and train the slaughterhouse managers on practices that would reduce carcass contamination. Three slaughterhouses with different levels of hygiene control, classified as 'export', 'improved local' and 'typical local', were selected. Three hundred cattle were tracked along the slaughtering process to sample faeces and carcass. A rectal faecal sample was taken from each animal after stunning. Two carcass sites, flank and brisket were swabbed after flaying, evisceration and washing. Thus, in total seven samples were taken from each animal. E. coli 0157 was isolated by culture and serotyped using card agglutination test. The isolates were further tested for verotoxin production. Monte Carlo simulation was run to determine the risk of carcass contamination. A Hazard Analysis Critical Control Point (HACCP) model was developed for one of the abattoirs. Interviews were done with slaughterhouse workers to test their knowledge, attitudes and practices towards slaughtering hygiene. Identified gaps on hygiene from slaughter personnel questionnaire were used to develop training materials for slaughterhouse managers and staff. E. coli 0157:H7 was recovered from faecal and carcass samples at different stages of carcass dressing. Two hundred and eighty (280) out of 2,100 samples (13.3%) yielded sorbitol MacConkey negative E. coli isolates (IMViC .( ++~-) which were presumptive E. coli 0157. After serotyping with 0157 antigen, 92 out of 280 (or 4.3 % of the total 2,100 samples) isolates, were positive for E. coli 0157. Forty-two isolates of the 92 were tested for verotoxin production, eight were positive for VTl only while two were positive for both VTl and VT2. The risk of a carcass being contaminated with E. coli 0157 on the abattoir was 29, 38 and 48 carcasses per 1000 slaughtered animals for the export, the typical local and the improved local abattoirs respectively at 90% confidence interval. There were significant differences in prior training received by the workers in the typical local abattoir and the improved local (p=0.001) with the typical local slaughterhouse having more trained workers than the improved local, but there was no significant difference between the export and the typical local slaughterhouse and between the export and the local improved slaughterhouse. More workers were significantly (p=0.025) washing their hands before, during and after slaughtering each animal in the typical local than the improved local slaughterhouse. The number of workers playing more than one role in the slaughter process was also significantly (p= 0.027) higher in the improved local than the typical local slaughterhouse. These factors may have contributed in the differences in carcass contamination in the three slaughterhouses. Slaughterhouse owners and staff were trained on good hygienic practices, food borne illnesses and risk of contamination of carcasses. Evaluation done one month after the training showed no change in the hygiene practices of the workers. This may have been the result of inadequate facilities like hot water, soap and disinfectants in typical and improved local slaughterhouses. Lack of motivation by the management and paying of the workers depending on the kill may affect the hygiene levels and workers attitude towards hygiene. This study shows that there is a risk of carcass contamination with E. coli 0157 in all the different categories of slaughterhouses. Workers and operations hygiene are important factors contributing to this risk.