Prevalence of mastitis and antibiotic resistance of bacterial isolates from cmt positive milk samples obtained from dairy cows, camels, and goats in two pastoral districts in southern Ethiopia

Authors: BALEMI, A - Mekelle University; GUMI, BALAKO - Addis Ababa University; AMENU, K - Addis Ababa University; GIRMA, S - Bule Hora University (BHU); GEBRU, M - Addis Ababa University; TEKLE, MULUKEN - Addis Ababa University; Agga, Getahun; RIUS, A - University Of Tennessee; D'SOUZA, D.H. - University Of Tennessee; KERRO DEGO, O - University Of Tennessee

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2021
Publication Date: 5/24/2021
Citation: Balemi, A., Gumi, B., Amenu, K., Girma, S., Gebru, M., Tekle, M., Agga, G.E., Rius, A., D'Souza, D., Kerro Dego, O. 2021. Prevalence of mastitis and antibiotic resistance of bacterial isolates from cmt positive milk samples obtained from dairy cows, camels, and goats in two pastoral districts in southern Ethiopia. Animals. 11(6). Article 1530. https://doi.org/10.3390/ani11061530.
DOI: https://doi.org/10.3390/ani11061530

Interpretive Summary: Mastitis is a disease of dairy animals manifested as inflammation of the udder in response to bacterial infections. It affects the welfare of the animal, public health, milk quality and production. Mastitis causing bacterial pathogens can cause human infection if raw milk is consumed or used for the production of other milk products. When milk from clinically sick animals is discarded or milk production is affected, it will result in economic loss to the farmer. Under poor resource settings such as pastoral production system, it reduces the availability of milk for household consumption whose main source of nutrition is milk. Farmers usually raise mixed herds composed of cows, camels and goats for milk production. The use of antibiotics leads to antimicrobial resistant bacteria which reduces the effectiveness of antibiotics for use in animals. Resistant bacteria can also infect humans through milk and milk products. We investigated the magnitude of mastitis in dairy cows, camels and goats raised under pastoral production system in Ethiopia. Between 15-20% of the milk samples examined were positive for mastitis. About 97% of milk samples cultured were positive for bacteria known to cause human infections. Overwhelmingly, 80% of the milk samples were positive for Staphylococcus species which are known to cause food poisoning. To treat and prevent infections, antibiotics are commonly used in dairy animal production. In the subset of bacterial isolates examined, all of them were resistant to at least four and up to nine antimicrobials suggesting the occurrence of multidrug resistant bacteria in the dairy animals in the pastoral communities. Our study clearly identified mastitis as a problem in the pastoral livestock production system and that multidrug resistant bacteria that can cause human infections are common. Infection control and antimicrobial stewardship can reduce the spread of antimicrobial resistant bacteria.

Technical Abstract: A study was carried out from August 2017 to February 2018 on lactating dairy cows, one-humped dromedary camels, and goats to determine mastitis in the Bule Hora and Dugda Dawa districts of in Southern Ethiopia. Milk samples from 564 udder quarters and udder halves from 171 animals consisting of 60 dairy cows, 51 camels, and 60 goats were tested for mastitis. Sixty-four positive udder milk samples were cultured, and bacterial mastitis pathogens were isolated and identified. The antibiotic resistance of bacterial isolates from milk with mastitis was tested against nine antimicrobials commonly used in the study area. Cow- and quarter-level prevalence of mastitis in dairy cows, camels, and goats was 33.3%, 26.3%, and 25% and 17.6%, 14.5%, and 20%, respectively. In cattle, the prevalence was significantly higher in Dugda Dawa than in Bule Hora. Major bacterial isolates were coagulase-negative Staphylococcus species (39.1%), S. aureus (17.2%), S. hyicus (14.1%), and S. intermedius and Escherichia coli (9.4% each). In camels, udder abnormality and mastitis were significantly higher in late lactation than in early lactation. Mastitis tends to increase with parity in camels. E. coli isolates were highly resistant to spectinomycin, vancomycin, and doxycycline, whereas most S. aureus isolates were multidrug-resistant. Most of the rural and periurban communities in this area consume raw milk, which indicates a high risk of infection with multidrug-resistant bacteria. We recommend a community-focused training program to improve community awareness of the need to boil milk and the risk of raw milk consumption.