PREVALENCE OF LISTERIA SPECIE IN LOCALLY PROCESSED MILK

(A CASE STUDY OF NASARAWA STATE, NIGERIA)

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Author

Presented To

Department of Medicine

ABSTRACT
Listeriosis is an emerging zoonoses requiring continuous surveillance in order to prevent outbreaks in humans. The disease can develop after consumption of a wide range of foods such as meat products, dairy products especially in ripened cheeses, delicatessen products, fish and seafood products and vegetables. It is a rare disease with high hospitalization rates for those who become ill and high mortality rate. Consumption of locally processed milk is becoming more popular among low and medium income earners in Nasarawa state and checking for possible disease agents that could be ingested in locally processed milk is essential for prevention. This research estimates the risks of listeriosis associated with consumption of milk products in Nasarawa State and establishes science-based intervention strategies aimed at reducing these risks. The study determines association between socio-demographic characteristics of milk vendors and the occurrence of Listeria species in locally processed milk in Nasarawa State, Nigeria. Four hundred and twenty (420) milk samples were collected from vendors after administering questionnaire on milk processing practices. Milk samples were processed in the laboratory by culture and isolation, biochemical characterisation, agglutination and Microbact test. Antibiotic sensitivity was also conducted on samples that tested positive for listeria. The socio-demographic characteristics of respondents showed that majoritywere within the age group 20-24 years, they were mostly females (92.4%), traders (53.1%), Muslims (99.5%); had no formal education (67.4%). Furthermore, majority of them earned between N6,000-N18,000 monthly (52.1%). Out of 420 samples collected and tested, 10.2% (43 samples) were positive for listeria through culture and isolation. Listeria species found in this study are 100% susceptible to enrofloxacin and doxycycline; 77.8% to kanamycin but resistant to Penicillin (93.7%) and Amoxicillin (80%) and Sulphamethazole/trimethoprim (60%). Borrowing/sharing of milk processing equipment and refrigeration/addition of ice to processed milk are factors significantly found to be associated with presence of listeria in milk sample (with odd ratio of 3.07 and 5.54 respectively). Conversely, training on food safety and supervision during milk processing were found to be significantly protective from listeria in milk sample (with odd ratio of 0.14 and 0.18 respectively). Processors of locally processed milk should be encouraged to undergo food safety training, observe strict supervision during processing of milk and be discouraged from the practice of adding ice to milk and borrowing or sharing of equipment.