Seroprevalence, and molecular detection of Brucella abortus in cattle tissues from an abattoir in Namibia

ABSTRACT

Brucellosis is a worldwide zoonosis that is endemic in Namibia. This study estimated seroprevalence of brucellosis, and determined the presence of Brucella infection in slaughtered cattle using the genus-specific 16-23S rRNA interspacer PCR (ITS-PCR), and the species-specific AMOS-PCR. Between December 2018 and May 2019, sera (n = 304), pooled lymph nodes (n = 304), and individual spleen (n = 304) were collected from slaughtered cattle from 52 farms. Sera were tested for anti-Brucella antibodies using the Rose Bengal test (RBT), and the complement fixation test (CFT). Seroprevalence was 2.3% (7/304) (RBT) and 1.6% (5/304) (CFT). Prevalence of positive herds was 9.6% (5/52). Lymph node (n = 200) and spleen (n = 200) samples from seronegative cattle tested negative for Brucella spp. DNA on ITS-PCR, but Brucella spp. DNA was detected in lymph nodes (85.7%, 6/7) and spleen (85.7%, 6/7) from RBT positive cattle. ITS-PCR confirmed isolates from lymph node (51.4%, 4/7) and spleen (85.7%, 6/7) as Brucella spp.; while AMOS-PCR and Brucella abortus species specific (BaSS) PCR confirmed the isolates as Brucella abortus, and field strains, respectively. Provision of adequate protective gear, and the promotion of brucellosis awareness among abattoir workers is recommended to prevent zoonotic infection.

KEYWORDS:

• Seroprevalence
• abattoir
• cattle
• ITS-PCR
• AMOS-PCR
• Brucella abortus

Acknowledgments

The authors wish to thank the abattoir operator for permitting the study on their premises; the Chief Veterinary Officer (Directorate of Veterinary Services, Namibia) for authorising the study; the Central Veterinary Laboratory (Namibia) for providing access to laboratory facilities and the University of Pretoria (Department of Veterinary Tropical Diseases, South Africa) for laboratory facilities and some materials used during bacterial isolation and molecular characterisation. Ms Manga Neta and Suoma Moses assisted with the performance of the laboratory work. The University of Namibia provided time for the first author to carry out the study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

Conceptualisation: OM and HvH; Sample Collection and Laboratory Analysis: OM, GA, FK, FBK, JNK, GT-Z, SK; Writing-Original Draft preparation: OM, HvH, FBK, AM-S, FK, JNK, GT-Z, SK, GA; Writing – Review and Editing, OM, HvH, FBK, AM-S, FK, JNK, GT-Z, SK, GA.

Data availability statement

The datasets used and/or analysed during the current study are included in this manuscript.

Ethics approval and animal welfare

The study protocol was approved by the Chief Veterinary Officer, Ministry of Agriculture, Water and Land Reform (Namibia); Director of Animal Health (South Africa) according to Act 35 of 1984 (REF 12/11/1/1/6 (905); Research Ethics Committee (REC 056–20) and Animal Ethics Committee (V055–18) of the University of Pretoria. Samples were collected from cattle that were slaughtered humanely at the abattoir.

Additional information

Funding

The Institute of Tropical Medicine (ITM), Antwerp (Belgium) partly funded the laboratory reagents used in this study. The funding body was not involved in either the design of the study or collection, analysis, and interpretation of data, nor the writing of the manuscript.