Risk Factors for Bovine Tuberculosis (bTB) in Cattle in Ethiopia

Abstract

Bovine tuberculosis (bTB) infection is generally correlated with individual cattle’s age, sex, body condition, and with husbandry practices such as herd composition, cattle movement, herd size, production system and proximity to wildlife—including bTB maintenance hosts. We tested the correlation between those factors and the prevalence of bTB, which is endemic in Ethiopia’s highland cattle, in the Afar Region and Awash National Park between November 2013 and April 2015. A total of 2550 cattle from 102 herds were tested for bTB presence using the comparative intradermal tuberculin test (CITT). Data on herd structure, herd movement, management and production system, livestock transfer, and contact with wildlife were collected using semi-structured interviews with cattle herders and herd owners. The individual overall prevalence of cattle bTB was 5.5%, with a herd prevalence of 46%. Generalized Linear Mixed Models with a random herd-effect were used to analyse risk factors of cattle reactors within each herd. The older the age of the cattle and the lower the body condition the higher the chance of a positive bTB test result, but sex, lactation status and reproductive status were not correlated with bTB status. At herd level, General Linear Models showed that pastoral production systems with transhumant herds had a higher bTB prevalence than sedentary herds. A model averaging analysis identified herd size, contact with wildlife, and the interaction of herd size and contact with wildlife as significant risk factors for bTB prevalence in cattle. A subsequent Structural Equation Model showed that the probability of contact with wildlife was influenced by herd size, through herd movement. Larger herds moved more and grazed in larger areas, hence the probability of grazing in an area with wildlife and contact with either infected cattle or infected wildlife hosts increased, enhancing the chances for bTB infection. Therefore, future bTB control strategies in cattle in pastoral areas should consider herd size and movement as important risk factors.

Survey of bovine tuberculosis in Nigerian beef cattle

“…Our study revealed the risk of having bTB to be significantly associated with the age of the animal. This finding agrees with the published observations made elsewhere in Africa (Dejene et al, 2016;Egbe et al, 2016). From our findings, female animals appear to have a higher risk of infection than males, similar to the findings of Worku et al (2016) in Ethiopia.…”

Risk practices for bovine tuberculosis transmission to cattle and livestock farming communities living at wildlife-livestock-human interface in northern KwaZulu Natal, South Africa

“…Consistent with other studies livestock keeping activities that were associated with bTB transmission to cattle involved uncontrolled movement of animals and introduction of animals into a herd without bTB pre-testing for social benefit, cultural or commercial purpose [7,15,35–37]. The free movement of cattle in communal farming within the village parameters is a common practice and movement to areas adjacent or into game reserves in search of pasture was attributed to the frequent drought conditions in the area.…”

“…Due to an increase in land use there is infringement of human activities into conservation areas that results in the sharing of natural resources with wildlife [14]. Studies in other countries have suggested that transmission of bTB to cattle from wildlife occurs either through direct contact at shared resources such as watering points or indirectly, when cattle graze on contaminated pastures [15]. Therefore, the wildlife-livestock interface has been defined as a high-risk area for bTB transmission from wildlife to cattle [16].…”

Perception and attitude of pastoralists on livestock-wildlife interactions around Awash National Park, Ethiopia: implication for biodiversity conservation

“…During such interactions, competition of livestock with wild grazers for pasture and water, predation of livestock by large carnivores, and transmission of zoonotic diseases between domestic and wild animals occur (Dejene et al 2016). According to previous studies (Prins 2000;Georgiadis et al 2007), competition for scarce grazing and water resources causes conflicts between pastoralists and wildlife managers, since pastoralists and agro-pastoralists migrate into the vicinity of national parks and protected areas during prolonged drought periods in semi-arid rangelands of Eastern Africa.…”