Epidemiology of bovine tuberculosis in dairy herds in Henan and Hubei Provinces, China

Xiaojie Zhu Zhu

Bovine tuberculosis (bTB) is a zoonotic disease caused by Mycobacterium bovis (M. bovis) that can lead to significant economic losses to the cattle industry and result in serious public health concerns in humans. Although bTB is prevalent in central China, the epidemiological characteristics of its occurrence in this area were not known prior to this study. A multifaceted study was conducted on dairy cattle farms in Henan and Hubei provinces of China to provide epidemiological and social evidence on bTB as an initial step towards its control and eradication. In these studies, the prevalence of bTB (typical TB-like lesions) among culled adult dairy cows was 28.1% (95%CI: 21.5-35.4). On-farm follow-up studies demonstrated a high animal- (18.7%, 95%CI: 17.6-19.8) and herd-level (93.5%, 95%CI: 82.1-98.6) prevalence of bTB in dairy farms in Henan and Hubei provinces, central China. For animal-level factors, the result illustrated that testing cows with a higher age group (≥ 60 months old) (OR=1.6, 95%CI: 1.1-2.2, p=0.006) and within the early stage of lactation (DIM=60-120 day, OR=1.9, 95%CI: 1.2-2.9, p=0.006) and the later stage of lactation (DIM≥301 days, OR=2.1, 95%CI: 1.3-3.5, p=0.003) could maximize the odds of detecting seropositive animals. In addition, herd positivity was associated with the practice of introducing new animals (RR=1.7, 95%CI: 1.0–3.0, p=0.042), and changing the disinfectant water in the wheel bath at the farm entrance every three days or less (RR=0.4, 95%CI: 0.2-0.8, p=0.005). The evaluation of an ELISA milk test generated a sensitivity and specificity of 48.4% (95%CI: 31.0–85.2) and 97.1% (95%CI: 92.2–99.7), respectively. The LnS/P% of the milk sample ELISA was associated with parity, natural log-transformed Somatic Cell Count (SCC) and milk urea nitrogen (MUN). Adjusting the S/P% based on these factors has the potential to affect test interpretation, which will influence the decision on what to do with these animals. It is an economical and effective method to use bulk tank milk samples for screening lactating dairy cattle for bTB. The diseases considered by farmers to be of significance were different from those prioritised by the regional participating animal health experts. From the perspective of the individual farmers, the effects of zoonotic disease risks such as bovine brucellosis and tuberculosis appear to be less pronounced than “visible” losses at the farm level, contrary to the opinion of experts. Participating experts believed that poor on-farm biosecurity measures posed challenges to the control and eradication of priority endemic diseases; however, there are gaps in farmers' understanding of biosecurity principles. A questionnaire-based survey was conducted in 50 dairy farms to describe the biosecurity status in Henan and Hubei provinces, China and further differentiated biosecurity levels between the farms. The introduction of new animals, visitors and vehicles, and the lack of isolation of sick animals were the main biosecurity risks across the dairy farms in Hubei and Henan provinces. High biosecurity scores implying adequate biosecurity measures were recorded in larger farms and farmers with higher education backgrounds. In summary, bTB is endemic in Henan and Hubei provinces, central China, and improved on-farm biosecurity and changes to husbandry could decrease the burden of the disease. Besides, during the implementation of bTB control programs for dairy cattle, the combined use of milk ELISA and IFN-γ test can improve the monitoring efficiency and reduce the monitoring cost. In addition, there is a need to improve the biosecurity practices across dairy cattle farms in Hubei and Henan and educate the farmers on the importance of biosecurity measures. These research findings can help strengthen the control of bTB in Henan and Hubei provinces and provide support for future bTB control strategies throughout China.

Epidemiology of bovine tuberculosis in dairy herds in Henan and Hubei Provinces, China

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