Bovine tuberculosis prevalence and risk factors in selected districts of Bangladesh

Abstract

A cross-sectional survey was conducted in selected districts of Bangladesh to estimate the prevalence of bovine tuberculosis (bTB), and to identify the risk factors for bTB. We included 1865 farmed cattle from 79 herds randomly selected from five districts. Herd and animal level data were collected using semi-structured interviews with cattle herd owners. The single intradermal comparative tuberculin test (SICTT) was used to estimate the prevalence of bTB. The risk factors were identified using mixed-effect multiple logistic regression analyses. The overall herd and animal level prevalences of bTB were estimated to be 45.6% (95% Confidence Interval [CI] = 34.3–57.2%) and 11.3 (95% CI = 9.9–12.8%), respectively, using the OIE recommended >4 mm cut-off. The true animal level prevalence of bTB was estimated to be 11.8 (95% Credible Interval = 2.1–20.3%). At the herd level, farm size, bTB history of the farm and type of husbandry were significantly associated with bTB status in univariable analysis. Similarly, age group, sex, pregnancy status and parity were significantly associated with bTB at cattle level. However, in multivariable analysis only herd size at the herd level and age group and pregnancy status at the cattle level were significant. Compared to a herd size of 1–10, the odds of bTB were 22.8 (95% CI: 5.2–100.9) and 45.6 times (95% CI: 5.0–417.7) greater in herd sizes of >20–50 and >50, respectively. The odds of bTB were 2.2 (95% CI: 1.0–4.5) and 2.5 times (95% CI: 1.1–5.4) higher in cattle aged >3–6 years and > 6 years, compared to cattle aged ≤1 year. Pregnancy increased the odds of bTB by 1.7 times (95% CI: 1.2–2.4) compared to non-pregnant cattle. Taken together, the results suggest high herd and animal level prevalence of bTB in these 5 districts, with the greatest risk of bTB in older and pregnant cattle within large herds (>20), and highlight an urgent need for continued surveillance and implementation of bTB control programs in Bangladesh.

Risk factors and true prevalence of bovine tuberculosis in Bangladesh

“…Our estimates are comparable to previous estimates but have the advantages that they adjust for the imperfect sensitivity and specificity of the diagnostic process [17][18][19]21]. In a previous study, the overall true prevalence of bTB was reported to be 11.8 (2.1-20.3%) which is also comparable to our result as the 95% credible intervals overlap [47]. Skin test results are often associated with the sensitization of the animals to M. avium subsp paratuberculosis and atypical mycobacteria [48].…”

“…Lack of adequate floor space, improper floor sanitation, and faulty ventilation system or confinement of the animals within the shed, inadequate management of farms may be the principle variables to increase the susceptibility of bTb in larger herds in the current study. Several reports supported this hypothesis that bTb is more prevalent in larger herds than smaller ones [23,27,47,[49][50][51][52][53][54][55][56].…”

Occupational exposure and challenges in tackling M. bovis at human–animal interface: a narrative review

“…The study also suggested that current dairy development programme focusing on the introduction of exotic and/or crossed animals could have influenced the epidemiological settings of bovine tuberculosis in the study area (Habitu et al 2019 ). A recently published cross-sectional study involving five districts in Bangladesh suggested that older and pregnant cows within larger herds are at heightened risk of bovine tuberculosis where continuous surveillance and implementation of bovine tuberculosis control program are urgently needed (Islam et al 2020 ). Collectively, most of studies discussed above show the significant association of M. bovis infection in livestock farmers with cattle being the possible source of infection to human although goats and other dairy animals can be infected by M. bovis as well (de la Rua-Domenech 2006 ).…”

“…Most of the data are generated from developing countries and the data from, in particular industrialized and developed countries, are limited. Further, majority of the available findings on occupational exposure and M. bovis infection are based on subnational data confined to a limited number of countries (Oloya et al 2008 ; Adesokan et al 2012 ; Khattak et al 2016 ; Nuru et al 2017 ; Ullah et al 2018 ; Vayr et al 2018 ; Kemal et al 2019 ; Islam et al 2020 ). Hence, the narrow breadth of currently available data restricted by geographical representative and the differences in the disease prevalence across different countries, sociodemographic and economical situations as well as food consumption habits and lifestyle may not be conclusive enough to present a global picture of the occupational exposure risk, where the true exposure dynamics could be far more complicated than anticipated in other parts of the world.…”

“…The risk factors associated with the transmission of M. bovis infection and the probable transmission routes involved for different occupational exposure should be carefully assessed at human–animal interface to reduce the zoonotic risk of M. bovis transmission to humans. The lack of veterinary health inspection to restrict M. bovis infection in herds coupled with a broad spectrum of breeding practices (Cleaveland et al 2007 ; Tigre et al 2011 ; Ameni et al 2013 ; Habitu et al 2019 ), working periods and health conditions of the workers (Adesokan et al 2012 ; Khattak et al 2016 ; Ullah et al 2018 ; Kemal et al 2019 ), food consumption habits such as drinking unpasteurized milk or eating raw cattle meat (Tigre et al 2011 ; Cordova et al 2012 ; Hambolu et al 2013 ; Nuru et al 2017 ) as well as the conditions of the cattle herds and the cattle status (Cleaveland et al 2007 ; Habitu et al 2019 ; Islam et al 2020 ) evident by different studies could possibly explain the heightened risk of M. bovis transmission in occupational-related setting. The primary transmission routes in accordance to discern occupational exposure mainly involved cutaneous, respiratory transmission, which are often related to wounds and to a lesser extent food consumption practices (Vayr et al 2018 ).…”