Steven J. Staal

Investigation of the risk of exposure to antimicrobial residues present in marketed milk in Tanzania.

Concerns about food safety are increasing in developing countries where urbanization and changing life styles are associated with greater dependence on marketed foods. Ensuring the safety of animal products supplied from smallholder and pastoral systems in these countries presents a great challenge. The risk of consumer exposure to marketed milk containing antimicrobial residues was investigated by testing 986 samples of unpasteurized milk collected in dry and wet seasons from market agents along milk supply chains in and around Mwanza and Dar es Salaam in Tanzania during 1999 and 2000 and estimating the frequency of consuming such milk. With the Charm-AIM screening test kit, antimicrobial residues were detected in 36% of marketed milk samples, suggesting an average risk of about 11 exposures per month for a daily consumer of milk. The higher prevalence levels of the residues were not significantly different by site or season, as had been hypothesized. Recommendations to address this problem are (i) creation of awareness among policy makers, who are currently unaware of the milk safety problem, and development of potential interventions to address the problem, (ii) testing for the residues at milk collection centers, and (iii) further investigation of milk production practices used by the predominantly smallholder producers and market agents. Risks should be characterized and estimated to provide a basis for designing appropriate extension messages and effective management strategies for protecting the health of consumers without unnecessarily jeopardizing the livelihood benefits derived from dairying by producers and market agents.

Risk of Exposure to Marketed Milk with Antimicrobial Drug Residues in Ghana

The study was carried out to determine the extent to which antimicrobial drugs may be translocated into milk and the associated risk of exposure by consumers. A total of 394 milk samples were collected in the study sites in dry and wet seasons, and from different categories of milk market agents, including producers (farmers), processors, wholesalers (assemblers) and retailers. The milk samples were screened for antimicrobial drug residues using the Charm Aim-96 an- timicrobial inhibition assay screening kit. Overall, 35.5% (140/394) of the milk samples collected were contaminated with one or more of the antimicrobial drugs screened. This translates into an average risk of exposure every third time a con- sumer drinks locally produced milk. There was no significant difference in contamination levels between season and area of sampling. Among market agents, contamination levels ranged from 16.6% (9/54) for wholesalers or milk assemblers to 54.2% (13/24) for milk processors. There were no significant differences in prevalence proportions of drug residues in milk from different types of traders between and within locations.

Risk factors in the hygienic quality of milk in Ghana

The study was carried out to identify risk factors associated with bacterial contamination of locally produced raw milk and its adulteration with water. A total of 419 respondents of different categories of milk agents in the study sites were sampled for data and milk collection in the dry and wet seasons. The data collected focused on milk marketing factors and handling practices likely to affect milk quality, while the milk samples were analysed to determine the extent of bacterial contamination and adulteration with water. The proportion of milk samples adulterated was 18%. While 23.5% of the milk samples had unacceptably high total plate count (>6.3 log10 cfu/ml), all the samples had unacceptably high coliform plate count (>0.7 log10 cfu/ml). Risk factors associated with high bacterial counts were related to milk mar- keting channels (p<0.05), milk market agents (p<0.01), and milk containers (p=0.06) as well as their mode of cleaning (p=0.06). The only risk factor identified for adulteration of milk was related to season (p=0.04). associated with poor hygienic quality. The findings would help in the formulation of appropriate recommendations to improve the hygienic quality of informally marketed milk in Ghana, which could go along way to stimulate growth of the dairy industry.