Farm-Level Risk Factors Driving Bovine Brucellosis: Insights for Prevention and Biosecurity in Dairy Herds

Despite ongoing vaccination programs, bovine brucellosis continues to persist in organized dairy systems, particularly in endemic regions like Karnataka. While the pathogen is well understood, its sustained transmission is largely driven by farm-level practices and management gaps. Identifying and mitigating these risk factors is crucial for veterinarians aiming to implement effective control strategies. 

Understanding the Farm Ecosystem in Disease Spread 

Brucellosis is not merely an animal-level disease; it is deeply influenced by environmental, managerial, and biosecurity factors. Intensive and semi-intensive dairy systems, common in India, often create ideal conditions for disease persistence and transmission. 

In a study of 24 organized dairy farms, multiple farm-level variables were evaluated, revealing that management practices play a decisive role in disease dynamics¹. 

Hygiene and Housing: The Hidden Determinants 

Good hygiene emerged as a critical protective factor, while poor sanitation significantly increased infection risk^1,2. One of the most overlooked yet impactful findings was related to flooring: 

• Farms with stone flooring showed significantly higher seropositivity (p < 0.01)  

The uneven, porous surface of stone floors makes thorough cleaning difficult, allowing infectious materials to persist in the environment. In contrast, smoother cement floors are easier to disinfect and maintain. 

Veterinarians advising new dairy setups should strongly recommend infrastructure that supports hygiene. 

Manure and Waste Management Practices 

In many farms, dung is stored in pits near the shed before being used as fertilizer or for biogas production. However, when infected uterine discharges mix with dung: 

• Pathogens can survive for extended periods  

• Soil, water, and feed contamination becomes likely  

Improper waste handling thus becomes a continuous source of infection within the farm ecosystem¹. 

Aborted Material: The Primary Infection Source 

Aborted fetuses, placentas, and uterine discharges are the most potent sources of Brucella transmission. When these materials are: 

• Disposed of in open fields  

• Thrown into water bodies  

They significantly increase environmental contamination and disease spread¹. 

Strict protocols for safe disposal, such as deep burial or incineration, must be emphasized in veterinary advisory practices. 

Animal Movement and Purchase Practices 

Unregulated animal movement is a major driver of brucellosis introduction into herds. Key risk factors include: 

• Purchase of animals from unknown sources  

• Frequent herd replacement  

• Lack of quarantine measures  

Introducing even a single infected animal can seed infection across the herd¹. 

Veterinarians should advocate for pre-purchase testing and mandatory quarantine periods. 

Role of Dogs and Biosecurity Gaps 

An often-underestimated factor is the presence of dogs on farms. In the study: 

• 60.39% of farms had dogs  

Dogs may consume or carry infected aborted materials, becoming secondary vectors. Infected dogs can then transmit B. abortus back to cattle¹. 

Additionally, poor biosecurity practices such as: 

• Unrestricted visitor access  

• Presence of stray animals  

further amplify transmission risks¹. 

Milking Practices and Equipment Use 

Interestingly, the type of milking (manual vs machine) was not directly associated with infection risk. However: 

• Hand milking was identified as a significant risk factor in multivariable analysis  

Machine milking can be safer if proper hygiene is maintained, especially when milking infected and healthy animals separately¹. 

Veterinary Services and Awareness Gaps 

Access to veterinary care significantly influences disease control. Farms lacking regular veterinary support showed higher seropositivity rates³. 

Moreover, farmer awareness remains critically low: 

• Less than 5% are aware of zoonotic transmission⁴ 

This gap highlights the need for continuous education and extension services. 

Key Risk Factors Identified 

The study identified several statistically significant (p < 0.01) risk factors¹: 

• Animals with 3–5 calvings  

• History of abortion, repeat breeding, retained placenta  

• Purchase of animals from other farms  

• Presence of dogs  

• Improper disposal of aborted materials  

• Hand milking practices  

• Poor manure management  

• Inadequate veterinary services  

These factors collectively sustain disease transmission in dairy systems. 

Control Strategies: Practical Field Recommendations 

To reduce brucellosis burden, veterinarians should focus on: 

• Biosecurity: Restrict animal movement, control visitors, manage stray animals  

• Hygiene: Improve flooring, regular disinfection, clean calving areas  

• Waste Management: Safe disposal of aborted materials and manure  

• Surveillance: Routine herd screening using reliable diagnostics  

• Vaccination: Continued use of S19 vaccine in young stock  

• Education: Farmer training on zoonotic risks and preventive practices  

The Bigger Picture: Economic and Public Health Impact 

Brucellosis ranks among the top economically impactful diseases in India, alongside foot-and-mouth disease. Its indirect losses, infertility, reduced milk yield, and zoonotic transmission are often underestimated. 

Achieving a brucellosis-free status requires sustained efforts over several years, integrating vaccination, hygiene, and surveillance. 

Conclusion 

Farm-level practices are the cornerstone of brucellosis control. While vaccination provides a foundation, it is the day-to-day management decisions that determine disease persistence or elimination. Veterinarians play a pivotal role in bridging knowledge gaps, implementing biosecurity, and guiding farmers toward sustainable dairy practices. Strengthening awareness and improving farm hygiene can significantly reduce the burden of this enduring zoonotic disease. 

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. Bashitu L, Afera B, Tuli G, Aklilu F. Sero-prevalence study of bovine brucellosis and its associated risk factors in Debrebirhan and Ambo towns. J Adv Dairy Res. 2015 Feb 22;3(131):2. https://www.academia.edu/download/123097072/2329-888x.100013120250603-1-3sajv8.pdf 

3. Ebrahim WO, Elfadil AA, Elgadal AA. Seroprevalence and risk factors of anti-brucella antibodies in cattle in Khartoum State, the Sudan. Journal of Advanced Veterinary and Animal Research. 2016 Jul 25;3(2):134-44. https://banglajol.info/index.php/JAVAR/article/download/28864/19263 

4. Rajkumar K, Bhattacharya A, David S, Balaji SH, Hariharan R, Jayakumar M, Balaji N. Socio-demographic study on extent of knowledge, awareness, attitude, and risks of zoonotic diseases among livestock owners in Puducherry region. Veterinary world. 2016 Sep 26;9(9):1018. https://pmc.ncbi.nlm.nih.gov/articles/PMC5057023/pdf/VetWorld-9-1018.pdf