A one health-focused literature review on bovine and zoonotic tuberculosis in Pakistan from the past two decades: challenges and way forward for control

Abstract

Bovine tuberculosis (bTB), caused by Mycobacterium bovis (M. bovis), is a globally prevalent zoonotic infectious disease. World Organization for Animal Health (WOAH) estimates indicate that up to 10% of the total human TB cases in developing countries are attributed to M. bovis. Pakistan ranks 4th in global milk production with a livestock population of over 212 million animals. Over 8 million families are involved in raising these animals as a means of livelihood. To date, there is an absence of national-level data on the prevalence of bTB and an effective control program is still lacking. The multifaceted impacts and substantial economic losses render addressing bTB a daunting, but highly important challenge. In this review, we summarise all the freely available literature on M. bovis infection from Pakistan using Google scholar and PubMed databases. A total of 40 animal studies were identified using search terms: "bovine tuberculosis in Pakistan, bTB, Pakistan, Mycobacterium bovis in Pakistan, M. bovis in Pakistan"; while seven human studies were identified using the terms: zoonotic tuberculosis in Pakistan', 'M. bovis in humans Pakistan', 'zTB in TB patients in Pakistan". We have summarized all these studies to identify critical risk factors involved in transmission of bTB among animals and humans. Despite lack of comprehensive and geographically representative studies, the literature suggests a varying prevalence of bTB in animals, ranging from as low as 2% to as high as 19%. Regarding zTB prevalence in humans, estimates range from 1.5% to 13% in high-risk group of farm and abattoir workers, with notably higher percentages in extra-pulmonary TB cases. The review also addresses the challenges that Pakistan faces in formulating an effective policy for the control and eradication of bTB. We conclude with one-health based recommendations as a way forward for controlling TB caused by M. bovis in cattle and humans.

Keywords: Bovine tuberculosis (bTB); Mycobacterium bovis (M. bovis); Pakistan; Public health; Zoonotic tuberculosis (zTB).

Fig. 1

Flow chart depicting the structure of this review. Aim and the data search strategy has been described with the categories of information summarized from all the identified studies. Comprehensive analysis of risk factors, current challenges and control recommendations have also been included.

Fig. 2

The maps demarcate the political borders of Pakistan. Left): The blue location icons represent the cities in which the 40 studies were conducted. Bovine tuberculosis prevalence studies were performed in 19 districts, with most districts targetted multiple times over the course of two decades. Right): Data points of 40 studies. Each location icon is represented by either a cow or a deer icon with different background colours. Blue colour represents studies that tested only cattle, black colour represents studies that only tested buffalos, pink colour represents studies that tested buffaloes, cattle, goat and (or) sheep, orange colour represents studies that tested both buffaloes and cattle. Green colour deer icon represents studies that tested different wildlife species. The large circles represent the three clusters of studies identified in this review paper. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

Fig. 3

Zoomed images of the three clusters created by the 40 studies performed in Pakistan to evaluate prevalence of bovine tuberculosis. Cluster 1: Top left, Cluster 2: Top right, Cluster 3: Bottom left. Note that the location represented on the maps by each icon is that of the city and not the exact farm where the animals were tested.