Prevalence and associated risk factors for Salmonella enterica contamination of cow milk and cottage cheese Ethiopia

Abstract

Animal sourced foods, such as dairy products, are common sources of Salmonella enterica, a foodborne pathogen of increasing global concern, particularly in developing countries. In Ethiopia, most data on the prevalence of Salmonella in dairy products is highly varied and limited to a specific region or district. Furthermore, there is no data available on the risk factors for Salmonella contamination of cow milk and cottage cheese in Ethiopia. This study was therefore conducted to determine the presence of Salmonella throughout the Ethiopian dairy value chain and to identify risk factors for contamination with Salmonella. The study was carried out in three regions of Ethiopia, including Oromia, Southern Nations, Nationalities and Peoples, and Amhara during a dry season. A total 912 samples were collected from milk producers, collectors, processors, and retailers. Samples were tested for Salmonella using the ISO 6579-1: 2008 method, followed by PCR confirmation. Concurrent with sample collection, a survey was administered to study participants to identify risk factors associated with Salmonella contamination. Salmonella contamination was highest in raw milk samples at the production (19.7%) and at milk collection (21.3%) levels. No significant difference in the prevalence of Salmonella contamination among regions was detected (p > 0.05). Regional differences were apparent for cottage cheese, with the highest prevalence being in Oromia (6.3%). Identified risk factors included the temperature of water used for cow udder washing, the practice of mixing milk lots, the type of milk container, use of refrigeration, and milk filtration. These identified factors can be leveraged to develop targeted intervention strategies aimed at reducing the prevalence of Salmonella in milk and cottage cheese in Ethiopia.

Seasonal Variation of Salmonella enterica prevalence in milk an cottage cheese along the dairy value chain in threee regions of Ethiopia

“…In SNNP, during wet season the prevalence of Salmonella was higher in pasteurized milk 3% (n = 6) but not signi cantly higher compared to raw milk and cottage cheese as shown in (Table 1). Even though the pattern detection of Salmonella is higher in raw milk 29.2% (n = 7) and pasteurized milk 25% (n = 6) in the dry season compared to cottage cheese 8.3% (n = 1) doesn't have a signi cant variation (χ2 = 2.00, P = 0.367) as it was outlined in Bedassa et al, (2023). The pattern of Salmonella prevalence in the Amhara region revealed that it was highly detected in raw milk 20% (n = 4) than in pasteurized milk 15% (n = 3) during the wet season but no signi cant variation has observed (Table 1).…”

“…2) value chains of the raw milk and processer 20% (n = 2) value chain of pasteurized milk during the wet season. The detection of Salmonella during dry season was highly detected in the producer 40% ( n = 4) value chain of raw milk and retailer 30% (n = 3) value chain of pasteurized even though no signi cant variation has been observed (χ2 = 2.7, P = 0.74) (Bedassa et al,2023).…”

“…The rainy (wet) and warm (dry) seasons of the nation's climate pro le were taken into consideration when designing a sampling plan to capture the seasonal differences. The selection criteria were based on the previously published data on prevalence of Salmonella in dry season (Bedassa et al,2023), which showed that samples taken from these sites had a higher prevalence of Salmonella than those taken from the other study sites, most notably Hawassa City. Second, the selected study locations had a complete set of value chain actors, including producers, collectors, processors, and retailers.…”

“…A total of 228 samples were collected in wet season (June, July, and August) from Debre Zeit (n = 120), Hawassa (n = 60), and Bahir Dar (n = 48). Previously published data from the dry season was used for the seasonal comparison (Bedassa et al, 2023). The dry season samples were collected from the same producers, collectors, processors, and retailers as during wet season (January, February, March, and April).…”

“…Salmonella isolates were con rmed utilizing PCR targeting the invA gene . The full detail procedure of Salmonella PCR conformation was outlined in our prior report (Bedassa et al, 2023). Each electrophoresis run included a 100 bp DNA ladder, as well as positive (Salmonella enterica ATTCC 35664) and negative controls (nuclease free water…”