Seroprevalence of brucellosis in caprine population of southern agro-climatic regions of Tamil Nadu

Introduction

Brucellosis is an economically important zoonotic disease caused by the gram-negative bacteria of Brucella species (Rossetti et al 2017 and Alton et al 1975) [11,2] . People contract Brucellosis by occupational exposures through handling of aborted fetus or placenta of infected animals [Corbel 2006) [4] , and inhalation of contaminated aerosol during the processing of the animal products (Dean et al 2007) [5] . Brucellosis creates significant economic losses to the livestock sector as it results in abortion, infertility, and decreased milk and meat production. The disease has been successfully managed or eradicated from several developed countries, but it is still endemic in livestock and human populations in resourcepoor countries (Mcdermott et al 2013) [9] .

Materials and Methods

A cross-sectional examination was directed to evaluate the prevalence of Brucella organisms in goats. Data were collected based on the previous history of abortion, retention of placenta, infertility and multiple breeding. Extensive rearing system and semi-intensive rearing system are pre-dominant, intensive rearing system is also noticed in the study area. The study was designed to collect samples and information from goat farmers in southern agro-climatic regions of Tamil Nadu. A total of 74 blood samples were collected, comprising D-I (Tirunelveli) (n = 22; buck:8, doe:14), D-II (Thenkasi) (n = 27; buck:8,doe: 19), D-III (Thuthukudi) (n =25; buck:6,doe: 19) by puncturing the jugular vein of goats using disposable 2 ml plastic syringes gently after wiping with 70% ethyl alcohol, collected blood transferred immediately to clot activator tubes(red vacutainer). After that, the collected blood samples were transported to the laboratory within a cool box containing an ice pack. The sera were separated through centrifugation at 4,500 rpm for 5 min at 15 °C, then decanted the clear serum into 1.0 ml Eppendorf tubes with labelling. For mentioning the identity of the animal such as sex and breed. Rose bengal plate test (RBPT) is carried out according to the information provided with the Ag kit. Antigen bottle refrigerated at 4°c was removed and left at room temperature for half an hour. Antigen was shaken to ensure homogeneous suspension. With a 100 μl micro pipette, 30 μl of coloured Ag was placed on each square of the plate. one drop 30 μl of serum was placed by the side of the antigen drop. With a spreader the antigen and serum drops were thoroughly mixed and spread to an area of about 2.5 cm diameter. The plate was manually rotated for 4 minutes. With each set of test sera, a known positive and negative control sera were also included. Definite clumping/agglutination to slight agglutination was considered a positive reaction, whereas no clumping/agglutination was regarded as a negative result.

Results and Discussion

Among the different samples of different regions of Southern agro-climatic regions of Tamil Nadu, the seroprevalence of Brucellosis was higher in District III by 4%, which was followed by 2.7% in D-II and 1.35% in D-I.High prevalence of infection associated with brucellosis in goat with a history of abortion highlights risks of human zoonotic infections by these pathogens. Therefore, special attention is required for further study and control program to counteract these infections in animals and humans. The table presents the distribution of goats by sex (buck and doe Overall, RBT positivity was slightly higher in bucks than does, suggesting a marginally higher exposure or susceptibility among bucks in the studied districts. Local goats did not show any RBT-positive cases in any of the districts, indicating absence or very low prevalence of infection in this group. Kanni goats showed consistent but low RBT positivity across all three districts (one positive in each district), suggesting widespread but limited exposure. Kodi goats exhibited higher RBT positivity, particularly in District III (two positives), followed by District II (one positive), while no positives were observed in District I. This indicates a relatively higher prevalence among Kodi goats, especially in District III. District III recorded comparatively more RBT-positive cases across sex and breed categories, followed by District II, while District I showed the least positivity. The results indicate a low but present seroprevalence of brucellosis among goats, with variation across sex, breed, and district. Bucks and Kodi breed goats, particularly in District III, appear to be more affected. The absence of RBT positivity in local goats suggests possible genetic resistance or lower exposure. These findings highlight the need for targeted surveillance and control measures, especially focusing on higher-risk breeds and districts. Like other studies, our study had some limitations. The complement fixation test (CFT) for confirmation of brucellosis in goat populations was not performed. Another limitation is that we could identify the factors that determines the source of occurrence of diseases in the flock and its transmission. The findings from this work provide better insight that could be utilized to improve management of brucellosis in small ruminants in the study area. Discovering such a substantial burden of brucellosis in small ruminants mandates the creation of awareness among the goat farmers about the zoonotic importance of Brucellosis.

Conclusion

Grazing of goats and flock mating may be a risk factor in the goat population for Brucella prevalence, and this needs to be studied thoroughly. However, it's suggested that further studies in the southern agro-climatic regions of Tamil Nadu to identify the associated risk factors for disease control. The present study revealed a low but definite seroprevalence of brucellosis among goats, with clear variations across sex, breed and district. RBT positivity was marginally higher in bucks compared to does, and among breeds, Kodi goats, particularly in District III which showed comparatively higher seropositivity, indicating greater vulnerability or exposure in studied population groups and geographical locations. A substantial proportion of farmers (41.99%) reported the occurrence of abortion in their animals, pointing towards inadequate reproductive health management. The occurrence of abortions among the studied group, when viewed alongside the detection of brucellosis antibodies, raises concerns about the possible role of infectious agents in reproductive losses. Management practices related to placental disposal and shed hygiene were found to be highly inadequate. Less than half of the respondents practiced proper placental disposal, while a considerable number either disposed of it improperly or left it on grazing land, posing a significant risk for the spread of zoonotic and contagious diseases such as brucellosis. Furthermore, the extremely low adoption of regular shed cleaning underscores poor hygienic practices, which can exacerbate disease transmission, reproductive disorders, and overall productivity losses. Overall, the findings underscore the urgent need for targeted interventions, including improved disease surveillance, farmer awareness programs on good management practices, and strengthening of reproductive health and biosecurity measures. Special emphasis should be placed on high-risk districts and breeds, along with promotion of proper biosecurity measures. Strengthening extension services and veterinary support is essential to mitigate reproductive losses, control zoonotic disease transmission, and enhance the sustainability of goat production systems.

References

1. Al Sekeit MA. Sero-epidemiological survey of brucellosis antibodies in Saudi Arabia. Ann Saudi Med. 1999;19(3):219-222.
2. Alton GG, Jones LM, Pietz DE. Laboratory techniques in brucellosis. 2nd ed. Geneva: World Health Organization; 1975.
3. Basavarajappa CM, Ramesh HA, Chandrasekhar CN, Patil JR. Seroprevalence of brucellosis in Davangere, Karnataka. J Clin Diagn Res. 2011;5(1):41-44.
4. Corbel MJ. Brucellosis in humans and animals. 1st ed. Geneva: World Health Organization, World Organisation for Animal Health, and Food and Agriculture Organization; 2006.
5. Dean AS, Crump L, Greter H, Schelling E, Zinsstag J. Global burden of human brucellosis: a systematic review of disease frequency. PLoS Negl Trop Dis. 2012;6(10):e1865.
6. Gwida M, Al Dahouk S, Melzer F, Rösler U, Neubauer H, Tomaso H, et al. Brucellosis: regionally emerging zoonotic disease? Croat Med J. 2010;51(4):289-295.
7. Indian Veterinary Research Institute. Rose Bengal plate test (RBPT) kit. Division of Biological Products. Izatnagar; 2001.
8. Koneman EW, Allen SD, Janda WM, Schreckenberger PC, Winn WC. Brucella species. In: Color atlas and textbook of diagnostic microbiology. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 1997. p. 431.
9. McDermott JJ, Grace D, Zinsstag J. Economics of brucellosis impact and control in low-income countries. Rev Sci Tech OIE. 2013;32(1):249-261.
10. Ran X, Chen X, Wang M, Cheng J, Ni H, Zhang X, et al. Brucellosis seroprevalence in ovine and caprine flocks in China during 2000-2018: a systematic review and metaanalysis. BMC Vet Res. 2018;14(1):393.
11. Rossetti CA, Arenas-Gamboa AM, Maurizio E. Caprine brucellosis: a historically neglected disease with significant impact on public health. PLoS Negl Trop Dis. 2017;11(8):e0005692.