Risk of human exposure to brucella pathogens through consumption of cultured milk in the southern province of Zambia.
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Date
2023
Authors
Thendji, Muila Lysa
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
Brucella is bacteria that causes Brucellosis, one of the most common zoonotic diseases in the world. The disease affects mainly animals but, in some cases, humans who are considered incidental hosts. Brucellosis is transmitted to humans through inhalation of aerosols or contact with skin sores, by the intake of infected animal products such as undercooked meat as well as consumption of raw milk or unpasteurised milk and dairy products. This study aimed to estimate the risk of human exposure to Brucella pathogens through the consumption of cultured milk in the Southern Province of Zambia. The specific objectives were to determine the consumption patterns of cultured milk by the population in the three districts of the Southern province and to estimate the likelihood of being exposed to Brucella spp. through cultured milk.
A survey was conducted using a structured questionnaire to interview traditional farmers at the milk collection centres and in selected households. Survey data were analysed in the STATA Statistical package to obtain frequencies on consumption patterns of cultured milk. A risk model was developed to estimate the risk of being exposed to Brucella spp. by consuming contaminated cultured milk using the Monte Carlo simulation in ModelRisk®.
The study had 236 males and 87 females, representing 73.1% and 26.9%, respectively. The proportion of farmers that fermented milk using raw milk was 65.3%. Boiled milk was used by 13.3%, and 21.7% purchased milk already fermented, not knowing if it was. The most common milk fermentation period was one day (40.9%), followed by those who fermented for two days (29.1%). Most respondents (63.8%) fermented milk at room temperature, and the majority (52.9%) consumed half to one litre of sour milk per person per day, while 47.1% consumed less than half a litre. The frequency of consumption was two-three times per day (60.7%), followed by one-two times per day (35.6%) and more than once per week (3.7%).
The surveys showed that there were four probabilities to be exposed to Brucella and the numbers of people likely to be exposed with the results are as follows: first probability (cultured milk prepared from raw milk obtained from an infected): 0.019 (90% CI: 0.059-0.022), number to be exposed was 17 (90% CI: 4-24). The second probability (cultured milk prepared from boiled milk obtained from an infected cow): 0.0184 (90%C I: 0.01265-0.037), the numbers to be exposed: 21 (90% CI: 11-39, the third probability (cultured milk prepared from raw milk obtained from a seronegative cow): 0.166(90% CI: 0.00135-0.0154), the numbers to be exposed was 15 (90% CI: 1-16). The fourth probability (cultured milk prepared from boiled milk obtained from a seronegative cow): was 0.023 (90% CI: 0.0029-0.02609), and the number to be exposed was 24 (90% CI: 2-29).
Most people consumed about 0.5 to 1.0 litres of cultured milk per day, made from raw milk fermented for one day. The consumption of cultured milk in the three districts was high and frequent. Moreover, consuming cultured milk from an infected animal exposed the population to Brucellosis and posed a risk to public health. To reduce the risk of humans being exposed to Brucella spp., there is a need to raise awareness among the farmers, the sellers, the consumers and the government about Brucellosis and associated risk factors. Furthermore, studies are required to assess the risk with a larger population.
Description
Thesis of Master of Science in Food Safety and Risk Analysis