A cross-sectional study on prevalence of bovine tuberculosis in Indian and crossbred cattle in Gangetic delta region of West Bengal, India

Seroprevalence and risk factors associated with bovine tuberculosis in cattle in Eastern Bhutan

Bovine tuberculosis (bTB) is a chronic zoonotic disease affecting cattle of all age groups including wild animals. It poses a significant threat to public health and high economic losses to dairy farmers. While the disease has been eradicated from most of the developed countries through extensive surveillance, testing and culling strategy, it is endemic in Africa, Asia, and the Middle East countries. Currently, there is limited research regarding the prevalence of bTB in cattle in Bhutan. This study aimed to determine the seroprevalence of bTB in cattle in six districts of eastern Bhutan. A two-stage probability proportional to size (PPS) sampling strategy was used to determine the number of animals from which serum samples needed to be collected in each district and sub-district. All farms and cattle for sampling were randomly selected from the data in the annual livestock census of 2020. The samples were tested using bTB ELISA test kit. The seroprevalence and their 95% confidence intervals were calculated. Logistic regression models were constructed to assess the influence of various individual animal and environmental risk factors (breed, age, sex, source of animal, body condition scores of animals, respiratory system status) associated with sero-positivity in animals. The study revealed an apparent seroprevalence of 2.57% (25/971 cattle; 95% CI:1.58-3.57), with an estimated true seroprevalence of 0.91% (95% CI: 0.0-2.81). However, none of the variables were found to be significantly associated with bTB seroprevalence in cattle. We recommend, further sampling and employment of confirmatory testing to fully ascertain the extent of bTB in the cattle herds in eastern Bhutan for prevention and control.

Divergent proinflammatory immune responses associated with the differential susceptibility of cattle breeds to tuberculosis

Tuberculosis (TB) in the bovine is one of the most predominant chronic debilitating infectious diseases primarily caused by Mycobacterium bovis. Besides, the incidence of TB in humans due to M. bovis, and that in bovines (bovine TB, bTB) due to M. tuberculosis- indicates cattle as a major reservoir of zoonotic TB. While India accounts for the highest global burden of both TB and multidrug-resistant TB in humans, systematic evaluation of bTB prevalence in India is largely lacking. Recent reports emphasized markedly greater bTB prevalence in exotic and crossbred cattle compared to indigenous cattle breeds that represent more than one-third of the total cattle population in India, which is the largest globally. This study aimed at elucidating the immune responses underlying the differential bTB incidence in prominent indigenous (Sahiwal), and crossbred (Sahiwal x Holstein Friesian) cattle reared in India. Employing the standard Single Intradermal Tuberculin Test (SITT), and mycobacterial gene-targeting single as well as multiplex-PCR-based screening revealed higher incidences of bovine tuberculin reactors as well as Mycobacterium tuberculosis Complex specific PCR positivity amongst the crossbred cattle. Further, ex vivo mycobacterial infection in cultures of bovine peripheral blood mononuclear cells (PBMC) from SITT, and myco-PCR negative healthy cattle exhibited significantly higher intracellular growth of M. bovis BCG, and M. tuberculosis H37Ra in the crossbred cattle PBMCs compared to native cattle. In addition, native cattle PBMCs induced higher pro-inflammatory cytokines and signaling pathways, such as interferon-gamma (IFN-γ), interleukin-17 (IL-17), tank binding kinase-1 (TBK-1), and nitric oxide (NO) upon exposure to live mycobacterial infection in comparison to PBMCs from crossbred cattle that exhibited higher expression of IL-1β transcripts. Together, these findings highlight that differences in the innate immune responses of these cattle breeds might be contributing to the differential susceptibility to bTB infection, and the resultant disparity in bTB incidence amongst indigenous, and crossbred cattle.

Prevalence of bovine tuberculosis and analysis of risk factors among the dairy farms in and around Guwahati metropolitan city, India

Bovine tuberculosis (bTB), a neglected zoonotic disease caused by Mycobacterium bovis is being reported worldwide. The present work was carried out from December 2020 to November 2021 to assess the prevalence and risk factors of bTB in peri-urban and urban dairy farms of Guwahati, Assam, India. A questionnaire was used to collect data on knowledge about bTB on 36 farms, and ten animals per farm were screened by single intradermal comparative cervical tuberculin test (SICCT) to determine the prevalence of bTB, giving a total of 360 animals. The demographic data of the farmers revealed that 61.1% respondents were illiterate, 66.7% had no awareness about bovine tuberculosis and 41.7% consumed unpasteurised milk and milk products. SICCT showed that 38 cattle from 18 of the farms were positive reactors for bTB, yielding an overall animal level prevalence of 10.55% (95% confidence interval (CI = 7.58-14.2%) and a 50% herd prevalence (95% CI 32.9-67.1%). Animals 5 years and above were found to be more likely to be positive for bTB (17.18%). The study highlighted the widespread prevalence of bovine tuberculosis in peri-urban and urban dairy farms of Guwahati which gives a picture also about other major cities of India. Hence, it is of utmost importance to undertake a comprehensive epidemiological study in such cities for effective control and prevention of bTB in a one health approach.

Prevalence of Mycobacterium bovis in milk on dairy cattle farms: An international systematic literature review and meta-analysis

Bovine tuberculosis, caused by Mycobacterium bovis (M. bovis), is a globally distributed chronic disease of animals. The bacteria can be transmitted to humans via the consumption of unpasteurised (raw) milk, thus representing an important public health risk. To investigate the risk of zoonotic transmission of M. bovis via raw milk, this study systematically reviewed published studies to estimate the prevalence of M. bovis in on-farm bulk-tank milk (BTM) and individual cow's milk (IM) by meta-analysis. In total, 1,339 articles were identified through seven electronic databases and initially screened using titles and abstracts. The quality of 108 potentially relevant articles was assessed using full texts, and 67 articles comprising 83 studies (76 IM and 7 BTM), were included in the meta-analysis. The prevalence of M. bovis in IM and BTM was summarised according to the diagnostic test used, and the tuberculin skin test (TST) infection status of the individual cows (for IM) or herds (for BTM). Heterogeneity was quantified using the I-squared statistic. Prediction intervals (95% PIs) were also estimated. For IM, the overall prevalence was summarised at 5% (95%CI: 3%-7%). In TST positive cows, prevalence was summarised at 8% (95%CI: 4%-13%). For BTM, the overall prevalence independent of individual herd TST infection status was summarised at 5% (95%CI: 0%-21%). There was considerable heterogeneity evident among the included studies, while PIs were also wide. Inconsistency in the quality of reporting was also observed resulting in missing information, such as the TST infection status of the individual animal/herd. No study reported the number of M. bovis bacteria in test-positive milk samples. Several studies reported the detection of M. tuberculosis and M. africanum in milk. Despite international efforts to control tuberculosis, this study highlights the risk of zoonotic transmission of M. bovis via unpasteurised milk and dairy products made using raw milk.

Risk factors and true prevalence of bovine tuberculosis in Bangladesh

Bovine tuberculosis (bTb) is endemic in Bangladesh but the true prevalence has not yet been reported. Our objectives for this study were to determine the true prevalence and identify risk factors for bTb at the animal- and herd-level in Bangladesh. A total of 510 cows were randomly selected during January 2018 to December 2018. Caudal fold (CFT) and comparative cervical tuberculin tests (CCT) were serially interpreted. Animal- and herd-level risk factor data were collected using a pre-tested questionnaire. The hierarchical true prevalence of bTb was estimated within a Bayesian framework. The herd- and animal-level risk factors were identified using mixed effects logistic regression. The apparent prevalence of bTb was 20.6% [95% Confidence Interval (CI): 17.3; 24.3] based on CFT. The animal-level true prevalence of bTb was 21.9 (13.0; 32.4). The herd-level true prevalence in different regions varied from 41.9% to 88.8%. The region-level true prevalence was 49.9 (13.8; 91.2). There is a 100% certainty that herds from Bhaluka and Mymensingh Sadar upazilas are not free from bTb. The odds of bTb were 3.9 times (1.2; 12.6) higher in herds having more than four cows than those with ≤ 4 cows. On the other hand, the risk of bTb was 3.3 times higher (1.0; 10.5) in non-grazing cows than grazing cows. Crossbred cows were 2.9 times (1.5; 5.9) more likely to be infected with bTb than indigenous cows. The risk of bTb in animals with cough was 2.3 times (1.2; 4.3) higher than those without cough. Crossbred, non-grazing cows with cough should be targeted for bTb surveillance. Herds of the Mymensingh, Sadar and Bhaluka regions should be emphasized for bTb control programs. Estimation of Bayesian hierarchical true prevalence facilitates identification of areas with higher prevalence and can be used to indicate regions that where true prevalence exceeds a pre-specified critical threshold.

Epidemiological Study of Mycobacterium bovis Infection in Buffalo and Cattle in Amazonas, Brazil

Bovine Tuberculosis (BTB) is an endemic disease in about one hundred countries, affecting the economy causing a decrease in productivity, condemnation of meat, and damaging the credibility on international trade. Additionally, Mycobacterium bovis the major causative agent for BTB can also infect humans causing a variety of clinical presentations. The aim of this study was to determine BTB prevalence and the main risk factors for the Mycobacterium bovis prevalence in cattle and buffalos in Amazonas State, Brazil. Tissue samples from 151 animals (45 buffalo and 106 cattle from five herds with buffalo only, 22 herds with cattle only, and 12 herds with buffalo and cattle) were obtained from slaughterhouses under State Veterinary Inspection. M. bovis were isolated on Stonebrink medium. The positive cultures were confirmed by polymerase chain reaction (PCR) testing. The apparent herd and animal prevalence rates were 56.4 and 5.40%, respectively. Regarding animal species, the apparent prevalence rates were 3% in cattle and 11.8% in buffalo. Generalized Linear Mixed Models (GLMM) with random effect were used to assess the association with risk factors on the prevalence. Species (buffalo), herds size (>100 animals) and the presence of both species (buffalo and cattle) in the herd were the major risk factors for the infection by Mycobacterium bovis in the region. The findings reveal an urgent need for evidence-based effective intervention to reduce BTB prevalence in cattle and buffalo and prevent its spread to the human population. Studies are needed to understand why buffalo are more likely to be infected by M. bovis than cattle in Amazon. Recommendations for zoning, use of data from the inspection services to generate information regarding BTB focus, adoption of epidemiological tools, and discouragement of practices that promote the mixing of cattle and buffalo, were made.