Bovine Brucellosis in India: Clinical Impact, Diagnostic Strategies, and Field-Level Challenges

Bovine brucellosis continues to be one of the most economically devastating and zoonotically significant diseases affecting livestock globally. Caused predominantly by Brucella abortus in cattle, and less frequently by Brucella melitensis and Brucella suis, the disease has far-reaching consequences not only for animal productivity but also for public health^1,2. In India, where dairy farming forms the backbone of rural livelihoods, the burden of brucellosis remains substantial despite ongoing control efforts. 

Clinical Manifestations: More Than Just Abortion 

While abortion is often the most recognized clinical sign, brucellosis presents as a multifaceted reproductive disorder. Infected bovines commonly exhibit: 

• Premature abortions  

• Repeat breeding  

• Retained placenta  

• Metritis  

• Stillbirths and weak calves  

• Reduced milk yield  

• Orchitis and epididymitis in males  

These manifestations significantly compromise herd fertility and productivity, often leading to chronic economic losses for farmers³. Importantly, veterinarians should note that many infections may remain subclinical, contributing silently to herd-level transmission. 

Zoonotic Relevance and Public Health Burden 

Humans act as accidental hosts, acquiring infection through direct contact with infected animals or contaminated animal products. With approximately 20% of cattle worldwide affected, brucellosis remains a persistent public health concern. In India, the lack of awareness among farmers, where less than 5% understand its zoonotic potential, further complicates control efforts¹. 

Epidemiology in the Indian Context 

India’s vast cattle and buffalo population ranks first and second globally, respectively, making disease control particularly challenging. Brucellosis is endemic, with higher seropositivity reported in states such as Karnataka, Maharashtra, Kerala, Delhi, and Kashmir¹. 

A study across 24 organized dairy farms in Karnataka revealed significant variability in seroprevalence¹: 

• Highest farm-level prevalence: 28.6%  

• Moderate prevalence: ~12% in some farms  

• Low prevalence (<3%): majority of farms  

This variation underscores the importance of farm-specific risk factors and management practices. 

Interestingly, buffaloes showed slightly higher seroprevalence (8.2%) compared to cattle (6.09%), although the difference was not statistically significant¹. 

Diagnostic Approaches: Combining Sensitivity and Specificity 

Accurate diagnosis is central to brucellosis control. Multiple serological tests are recommended, including: 

• Rose Bengal Plate Test (RBPT)  

• Buffered plate agglutination test  

• Complement fixation test  

• ELISA  

• Fluorescent polarization assay¹  

In field conditions, combining RBPT and indirect ELISA (iELISA) improves diagnostic accuracy. RBPT detects IgM and IgG1 antibodies typical of acute infection, whereas iELISA predominantly detects IgG, indicating chronic infection¹. This dual approach is especially useful for herd-level screening and epidemiological studies. 

Animal-Level Risk Indicators 

Contrary to common assumptions, age and sex were not significantly associated with infection risk in the study. However, specific factors showed strong associations¹: 

• Animals with 3–5 calvings had higher seropositivity (p < 0.01)  

• History of abortion, repeat breeding, and retained placenta increased risk significantly  

• Indigenous breeds like Gir cattle and Murrah buffalo were more susceptible  

These findings emphasize the need for veterinarians to closely monitor reproductive history as a key indicator of brucellosis. 

Transmission Dynamics in Dairy Farms 

Brucella organisms are primarily transmitted through: 

• Aborted fetuses  

• Placental tissues  

• Uterine discharges  

These materials serve as major infection sources, contaminating feed, water, and the environment. Improper disposal practices amplify disease spread within and between herds¹. 

Additionally, infected adult males can disseminate infection through semen, especially in natural breeding systems. 

Control Strategies: Beyond Vaccination 

India has implemented vaccination programs using the B. abortus S19 vaccine in calves since 2012¹. However, due to the absence of “test and slaughter” policies, control relies heavily on: 

• Vaccination of young stock  

• Improved farm hygiene  

• Early detection and isolation  

• Farmer education  

Mass vaccination, combined with sustained biosecurity measures, is essential to achieve long-term disease control¹. 

Practical Takeaways for Veterinarians 

For effective field management: 

• Prioritize reproductive history during herd health evaluations  

• Use combined diagnostic tests (RBPT + ELISA) for accuracy  

• Educate farmers on zoonotic risks and safe handling practices  

• Advocate for proper disposal of aborted materials  

• Encourage routine herd screening, especially in endemic regions  

Conclusion 

Bovine brucellosis remains a complex disease requiring an integrated approach involving diagnostics, vaccination, and farm management. For veterinarians, the challenge lies not only in identifying infected animals but also in addressing the systemic gaps in awareness, hygiene, and biosecurity. Strengthening surveillance systems and farmer education will be critical to reducing the burden of this persistent zoonosis in India. 

Reference 

1. Shome R, Natesan K, Kalleshamurthy T, Yadav C, Sahay S, Skariah S, Mohandoss N, Kumar OR, Shome BR, Rahman H. Management of bovine brucellosis in organized dairy herds through the identification of risk factors: A cross-sectional study from Karnataka, India. Veterinary World. 2023 May 30;16(5):1122. https://pmc.ncbi.nlm.nih.gov/articles/PMC10420698/pdf/Vetworld-16-1122.pdf 

2. Whatmore AM, Koylass MS, Muchowski J, Edwards-Smallbone J, Gopaul KK, Perrett LL. Extended multilocus sequence analysis to describe the global population structure of the genus Brucella: phylogeography and relationship to biovars. Frontiers in microbiology. 2016 Dec 21;7:2049. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.02049/pdf 
3. Kumar AV, Krishnaiah N, Rao LV, Reddy YN, Reddy KK, Narayana BV. Seroprevalence of brucellosis in buffaloes of Telangana state, India. Buffalo Bulletin. 2018 Sep 27;37(3):303-11. https://kuojs.lib.ku.ac.th/index.php/BufBu/article/download/82/1020