Serodiagnosis of brucellosis in an organized swine farm in Coimbatore district of Tamil Nadu

Introduction

Brucellosis is an economically important and contagious infectious bacterial disease of livestock caused by members of the genus Brucella. In pigs, the disease is primarily due to Brucella suis, which has a wide host range and is also pathogenic to humans, causing significant public health concerns (Radostits et al. 2007; Olsen & Tatum, 2016) [6,4] . The infection in swine leads to reproductive failures such as abortion, infertility, orchitis, and stillbirths, resulting in considerable economic losses (Nicoletti, 2007) [3] . Accurate diagnosis is an essential part for control and eradication of brucellosis. Although isolation and identification of bacteria is the gold standard, it is hazardous, time-consuming, and requires well equipped laboratory facilities (Corbel, 2006) [1] . Therefore, serological tests remain the mainstay for large-scale screening of herds. Rose Bengal Plate Test (RBPT) helps for rapid screening at herd level, while Standard Tube Agglutination Test (STAT) and Enzyme-Linked Immunosorbent Assay (ELISA) provide confirmatory diagnosis (Gwida et al., 2010) [2] . Despite global efforts, brucellosis remains endemic in several developing countries, including India, where pig farming is gaining importance as a source of livelihood and protein security. This study was conducted to find out the occurrence of brucellosis in an organized swine farm which reported the higher incidences of abortion using standard serological methods.

Materials and Methods

Study area and animals:

The study was carried out in an organized swine farm located on the outskirts of Coimbatore, Tamil Nadu and housing approximately Large White Yorkshire (LWY) 120 female and 10 male pigs under intensive management practices. The herd comprised gilts, sows, boars, and growers of different age groups. Farmers followed standard management practices for housing, feeding, breeding management. The pigs were routinely vaccinated against classical swine fever, foot and mouth disease, and porcine circovirus. Feeding was based on the recommended nutritional requirements and the blood meal at the rate of 3 to 5 per cent occasionally supplemented to the diet.

Clean drinking water was provided ad libitum. The farmer reported abortion in ten gilts at around 60 days of gestation. The affected gilts were approximately 12 to 13 months of age at the time of abortion. Natural service was practiced on the farm and no routine screening and vaccination was followed against brucellosis. Apart from reproductive disturbances, no other major health issues were reported.

Sample collection

A total of 30 blood samples from aborted gilts as well as in contact animals were collected from different age group of pigs. Approximately 5 ml of blood was collected aseptically from the jugular vein into sterile vacutainers. Serum was separated by centrifugation at 3000 rpm for 10 minutes and stored at -20°C until use.

Serological Tests

Rose Bengal Plate Test (RBPT) antigen was purchased from Institute of Animal Health and Veterinary Biologicals, Hebbal, Bangalore and stored at 4⁰C until use. The sera were screened using the RBPT antigen for initial detection of antibodies against Brucella as per WOAH, 2021 [10] .

Results and Discussion

Out of the 30 serum samples tested, 12 samples were found positive for Brucella antibodies by RBPT (Fig. 1). Out of 12 positive samples, one sample was from boar which was used for breeding and newly purchased and introduced into the farm without screening against brucellosis. [9,8] . Previous studies have reported variable prevalence of swine brucellosis in India (Shome et al., 2016; Preena et al., 2024) [7,5] and worldwide, reflecting differences in management, biosecurity, and diagnostic approaches. The results of this study align with reports suggesting that brucellosis remains underdiagnosed in pigs due to lack of routine surveillance. Routine screening of newly introduced pigs and within the farms for removal of infected pigs is important to avoid the outbreaks of the. RBPT is an important screening test to identify the swine brucellosis in herd.

Conclusion:

The occurrence of brucellosis in organized farms highlights the importance of adopting preventive measures such as routine screening, culling of positive animals, strict biosecurity practices, and awareness programs for farm workers to minimize zoonotic transmission.

Acknowledgement

Acknowledgements:The author thank the farmers and animal handlers who have accepted to participate in this study

References

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