Prevalence and risk factors of bovine tuberculosis in slaughtered cattle, Malawi

Abstract

Bovine tuberculosis (bTB) is an infectious disease with significant socioeconomic, animal, and public health impacts. However, the prevalence of bTB remains largely unclear in Malawi due to a paucity of information. Additionally, the existence of multiple risk factors is postulated to enhance bTB transmission in animals. A cross-sectional survey to estimate the prevalence of bTB, animal characteristics and identify associated risk factors was conducted from slaughtered cattle at three major regional abattoirs (southern, central and northern regions) in Malawi. Out of a total of 1547 cattle examined, 154 (9.95%) had bTB-like lesions in various visceral organs and lymph nodes; one sample per animal was collected, processed, and cultured in the in the BACTEC Mycobacterial growth indicator tube (MGIT) 960 system. From the 154 cattle that showed tuberculous like lesions, only 112 were positive on MGIT and 87 were confirmed to have M. bovis based on multiplex PCR. Cattle from the southern region (odds ratio (OR) = 1.96, 95% CI: 1.03-3.85) and central region (OR = 2.00, 95% CI: 1.16-3.56) were more likely presented with bTB-like lesions at slaughter than from the northern region. The risk of having bTB-like lesions was higher in females (OR = 1.51, CI: 1.00-2.29), older cattle (OR = 2.17, CI: 1.34-3.37), and crossbreeds (OR = 1.67, 95% CI: 1.12-2.47) than in males, younger animals, and Malawi Zebu breed, respectively. The high prevalence of bTB is of critical concern and necessitates active surveillance and strengthening of the current control strategies under a One Health (OH) approach at the animal-human interface.

Keywords: Bovine tuberculosis; Malawi; Mycobacterium bovis; Regional abattoirs; Slaughtered cattle.

Fig. 1

Map of Malawi showing the location of the three major regional abattoirs where sampling took place (star). Tissue samples with granulomatous bTB-like lesions were collected from cattle slaughtered at an abattoir in Blantyre city (Southern region), Lilongwe city (Central region), and Mzuzu city (Northern region).

Fig. 2

Distribution of the raw counts of bTB-like lesions from cattle slaughtered in the three regions of Malawi: Southern region – 32 lesions, Central region – 104 lesions, and Northern region – 18 lesions.