The buffalo population of Madhya Pradesh state as per the 20
th livestock census is 10.30 million. Brucellosis in different host populations is caused by one of the several members of the bacterial agent of
Brucella (B) species (
B. abortus,
B. melitensis,
B. suis,
B. ovis,
B. canis,
B. neotomae,
B. ceti and
B. Pinnipedalis)
(Quinn et al., 2011). It is an important bacterial disease posing an economic threat to livestock owners in Asia
(Bamaiyi et al., 2014). The disease is contagious in nature, spread fast and affects ruminants, wildlife and also human beings. The losses due to the disease can be counted as a) decreased milk production, b) weight loss, c) loss of young, d) infertility and e) lameness (
https://www.aphis.usda.gov/animal_health/animal_diseases/brucellosis/downloads/bruc-facts.pdf; Accessed on 1
st June 2023). Detailed reviews about the disease in animal populations had been published by several researchers emphasizing etiology, epidemiology, pathogenesis, immune response, diagnosis, vaccination and its control (
Smits and Kadri, 2005;
Gul and Khan, 2007;
Boral et al., 2009; Manish et al., 2013; Shoukat et al., 2017; Khurana et al., 2021). Several researchers have reported the presence of
Brucella species infection (
Kataria and Verma, 1969;
Isloor et al., 1998; Mehra et al., 2000; Gogoi et al., 2017; Gupta et al., 2017; Verma et al., 2019; Islam et al., 2021) and IBR infection
(Nandi et al., 2004, Nandi et al., 2007; Audarya et al., 2017; Patel et al., 2018) in the livestock population. Some of the researchers have also used molecular methods for the identification and characterization of the organisms
(Ghodasara et al., 2010; Pandey et al., 2014a).
The results of the present investigation are presented in Table 1, 2 and Fig 1, 2. A total of 147 unvaccinated buffalo serum samples collected from a livestock farm were tested by an agglutination test, RBT. Some of these buffaloes at a farm experienced abortion and also a drop in milk production during the year, mid-2015. This history of the animals pointed towards possible infection due to
Brucella species organisms and hence in that year in the late-2015 collected serum samples from these buffaloes were received for initial screening by agglutination test. On finding positive samples (27 positive samples out of 147 tested), it was advised to farm authorities to send and get tested those samples at Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh for further confirmation of individual animals by ELISA due to the unavailability of an ELISA kit at the laboratory. However, one of the sets of serum samples from these buffaloes was stored in the deep freezer and sent to Virus Laboratory at the Centre for Animal Disease Research and Diagnosis, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India. These serum samples were tested during the year 2018-2019 for the presence or absence of antibodies to the IBR virus since this virus is also implicated in reproductive failures including abortion. There are several tests available for the diagnosis of brucellosis in cows and buffaloes by using various clinical specimens namely isolation of the
Brucella species organisms, serological testing and advanced molecular detections
(Rahman et al., 2011; Sharma and Bist, 2012;
Jadav et al., 2022). Isolation of the agent is considered the gold standard for the diagnosis of brucellosis but this can be a time-consuming and laborious process besides posing a risk of infection to laboratory personnel. That’s why serological tests are generally preferred for their simplicity and low cost. In previous studies, high as well as lower percentages of anti-
Brucella antibodies from randomly collected or suspected/infected cases of bovines were reported in India and abroad by using different diagnostic tests
(Rahman et al., 2011; Shome et al., 2014; Priyanka et al., 2018). Bovine brucellosis in Madhya Pradesh was reported as early as 1969 (
Kataria and Verma, 1969) and continued to be reported in the state in large ruminants
(Gupta et al., 2017; Verma et al., 2019). Mehra et al., (2000) reported an overall prevalence of 6.3% in cattle and buffaloes irrespective of sex and age and higher seroprevalence rates in buffaloes (11.4%) than in cows (9.6%) in Madhya Pradesh state. The RBT is very sensitive. However, like all other serological tests, it could sometimes give a positive result because of vaccination, however, the buffaloes in the present study were unvaccinated against both of these diseases, brucellosis and IBR. Therefore, positive reactions in RBT can be reliable. Still, it can be further investigated using suitable confirmatory or complementary strategies (including epidemiological investigation). Since few of the pregnant buffaloes in the present investigation suffered from abortion in the late trimester of their first pregnancy, the RBT results could be supported by the history. False-negative reactions occur rarely in the case of RBT. RBT appears to be adequate as a screening test for detecting infected herds or to guarantee the absence of infection in brucellosis-free herds or flocks
(
https://www.woah.org/fileadmin/Home/fr/Health_standards/tahm/3.01.04_BRUCELLOSIS.pdf).
The present study reported a higher seroconversion rate (18.36%) by RBT testing of buffaloes with a history of abortion at the livestock farm due to the
Brucella species infection. Higher seroconversion could be due to the presence of infected aborted buffaloes and shedding of bacteria in large quantities and the transmission of the organisms to susceptible buffalo populations that were in close contact and unhygienic practices. Brucellosis is responsible for more than double the economic loss in an infected buffalo compared to an infected cow
(Jadav et al., 2022). Shome et al., (2014) reported a higher percentage of prevalence of brucellosis in buffaloes (39.32%) than in cows (4.33%) and also concluded that the disease was more prevalent in farms with a history of abortion and repeat breeding problems. Indian breeds of cattle (Hallikar, Ongole) and buffalo (Surti) were found negative except for 50% of Murrah buffaloes that tested positive in this study. Hence, it is important to assess the status of infection at a farm especially when unvaccinated buffaloes are experiencing abortion.
Trangadia et al., (2009) investigated organized dairy farms in India and concluded that
Brucella species organisms as well as the IBR virus were implicated in cases of abortions. However, in the present investigation, 18.36% (27 positive out of 147 tested) of buffalo serum samples tested positive in RBT and no detection of antibodies against the IBR virus at a livestock farm confirmed an outbreak of brucellosis in buffaloes of the farm. These findings and the history of buffaloes also revealed the
Brucella species organisms as the sole member that caused abortions in buffaloes at the farm under the study. Prevention and control of brucellosis is done by following standard biological practices related to the quarantine of infected/diseased animals from healthy animals and vaccinations of the remainder. Eradication and control of the disease are achieved elsewhere by following testing and slaughter of infected animals and vaccinations to susceptible livestock populations including buffaloes
(Puran et al., 2015) for minimizing economic losses to livestock owners. Brucellosis is also a zoonotic disease (
Yohannes and Gill, 2011). In pregnancy, the disease is associated with adverse outcomes such as spontaneous abortion, preterm delivery, chorioamnionitis and fetal death
(Vilchez et al., 2015). Hence screening manpower at farms and being involved with related activities and treatment of affected individuals if any is necessary. The study findings also highlight the importance of vaccinations to buffalo and other susceptible livestock populations of the country as envisioned in the Government of India policies to contain the losses incurred due to brucellosis. Newer strategies of control are also being investigated (
Saxena, 2021) elsewhere.
