Abstract
Aim : The aim of this study was to investigate the incidence of bovine tuberculosis (BTB), an old chronic disease having zoonotic potential, covering four districts in Gangetic delta region of West Bengal, India, and to find the prevalence in organized as well as backyard herds and variation in relation to their age, sex, and breeds. Methods : The incidence of BTB in exotic and indigenous breeds of cattle (n=173) of various age groups was investigated employing tuberculin (single intradermal tuberculin and comparative cervical tuberculin) tests and gamma interferon assay. Further, milk samples (n=96) from milching animals and antemortem (n=519) samples (nasal swab, buccal swab, and aspirates from pre-scapular lymph nodes) were also screened employing bacteriological and molecular techniques. Results : In total, 36 (25.4%) animals from organized and one (3.2%) from backyard farming sector were found positive to BTB. Polymerase chain reaction (PCR) of milk samples based on 16S rRNA amplified the 1030 bp band in four samples indicating them belonging to genus Mycobacterium. Species-specific primers used to differentiate between Mycobacterium bovis and M. tuberculosis confirmed the presence of M. bovis. Prevalence of BTB in exotic crossbred animals (34.6%) was significantly higher (p<0.001) compared to indigenous cattle (10.5%). Further, gender-wise analysis of data with respect to BTB revealed higher positivity (p<0.05) among cows/heifers (25.8%) compared to bulls/bullocks (7.3%). Although BTBpositive cattle were detected in all the age groups, no statistical difference (p=0.779) was found among them. Conclusion : The findings indicate a higher prevalence of BTB in exotic crossbred animals in Gangetic delta and variation in breed susceptibility, thereby suggesting an urgent review of the present policy on adopting national crossbreeding program and implementation of “One Health” approach.
Highlights
Bovine tuberculosis (BTB), caused by Mycobacterium bovis, is a highly prevalent infectious disease of cattle, buffaloes, and many wild species worldwide [1,2]
A direct correlation between M. bovis infection in cattle and the disease in human population has been well documented in developed countries, very little information is available from developing countries [6]
HiPurATM multi-sample DNA purification kit (HiMedia, India) was used for the extraction of genomic DNA from antemortem samples, cultural isolates as well as reference strains of mycobacteria (M. bovis AN5 and Mycobacterium tuberculosis H37Rv) in LJ media as per manufacturer’s instructions
Summary
Bovine tuberculosis (BTB), caused by Mycobacterium bovis, is a highly prevalent infectious disease of cattle, buffaloes, and many wild species worldwide [1,2]. Due to its chronic and progressive nature, this disease causes a significant economic impact accounting 10-25% loss in productive efficiency in dairy cattle, often resulting in high morbidity in animals. The World Health Organization has classified BTB as one of the seven neglected zoonotic diseases having a potential to infect human beings, either by consuming raw milk, meat, and their products [3] or inhaling infective droplets or direct contact with infected animals [4]. The above data may not truly represent the epidemiological status of human tuberculosis caused by M. bovis in India due to lack of effective disease surveillance, non-availability of more sensitive and specific diagnostic test, and effective reporting systems
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