A Study of Milk Quality and Public Health Hazards in the Smallholder Peri-Urban Dairy Marketing System in Ghana

Abstract

Dairying is a young and developing industry in Ghana, and one of the major problems it faces is the low demand of the milk produced. This is partly due to public concerns over the safety and quality of the milk produced, and also the hygienic practices of informal agents. However, the extent of risks posed to human health by consumption of milk and dairy products in the country is not well documented. This project was therefore carried out to study the quality and the public health hazards inherent in marketed milk in Ghana. The study was conducted at two sites, namely Accra (Peri-urban Accra) and Kumasi (Peri-urban Kumasi) in Ghana. The areas or districts were chosen within these sites to represent a variation in consumer concentration, market access and dairy production intensity within each site. Data related to milk handling, and other market factors that affect milk quality, or pose a risk to public health were collected during the dry and wet seasons (1999-2000) from respondents selected by a stratified random sampling within each area. Milk samples were also obtained from the respondents for laboratory analysis for their quality and health risks. These involved the assessment of their bacteriological quality, determination of the bacterial flora, the evaluation of contamination with antimicrobial agents, and assessment of the compositional quality and adulteration. Laboratory data and the market level data were analysed to assess the milk quality and milk-borne health hazards, and their relationship with season, site, and marketing factors, including the handling and hygienic practices of market agents. Overall, 35% of milk samples were found to be contaminated with antimicrobial agents, and three factors were found to significantly influence the contamination of milk with antimicrobial agents. These were site, type of milk trade practiced, and source of milk. The most potent of these factors was milk source: milk sourced from the farm was found to be strongly associated (p<0.01) with high levels of antimicrobial agents compared with other sources. The milk traded in Accra was associated with high levels of antimicrobial agents (p=0.04), and likewise milk handled by farmers or producers (p=0.06). The mean coliform bacteria plate counts for raw and processed milk were 3.7 log, 0 cfu/ml and 3.5 log i0 cfu/ml respectively, while both types of milk had the same mean total bacteria plate count (5.9 log 10 cfu/ml). Bacteriological quality of milk was also significantly associated with milk pathways, type of milk trade, type of milk container, and mode of cleaning containers. High total bacterial counts were associated with use of gravels (p=0.04) compared with sponge for cleaning milk containers. High coliform counts were strongly associated with milk associated with wholesalers (p<0.01), and two milk pathways namely, Herdsman Processor (milk sourced from herdsman to processor) (p=0.03) and Trader/hawker Retailer (milk sourced from trader/hawker to retailer) (p=0.04). Plastic containers (p=0.06), and the use of soap (p=0.06) compared to detergent for cleaning containers, were also associated with high coliform counts. In terms of compositional quality, the means of butterfat, specific gravity, solids-not-fat, and total solids of milk samples determined were 3.25%, 1.030kg/litre, 8.833%, and 12.078% respectively. All the means determined fall within the expected ranges of the respective components or properties of normal bovine milk. On the whole, 18% of milk samples were found to be adulterated with water. Generally, adulteration was significantly higher in the wet season (p<0.10) than the dry season. Overall, the bacterial flora of milk sampled consisted of eight different potentially pathogenic bacteria, which were identified by culture or serology. The organisms so identified were Escherichia coli, Brucella abortus, Klebsiella spp., Yersinia spp., Mycobacterium spp., Proteus spp., Bacillus spp. and Staphylococcus spp. The bacterial flora of milk from Kumasi consisted of only the first four organisms enumerated above, while Klebsiella spp. was the only organism absent in milk from Accra. It was also observed that generally, a higher prevalence of bacteria was associated with milk samples from Accra than those from Kumasi, clearly indicating that milk from Kumasi was of better quality than those from Accra. The high level of contamination of milk with various antimicrobial agents has obviously very serious public health implications, since antimicrobial agents have been implicated in various health problems like drug resistance and hypersensitivity. Similarly, the presence of pathogenic microorganisms in milk is a cause for great concern as several of the organisms identified have been implicated in many human disease outbreaks. Adulteration of milk with water observed also requires attention as this practice could introduce several health risks into milk produced and marketed in Ghana.