Brucellosis is Significantly Associated with Reproductive Disorders in Dairy Cattle of Punjab, Pakistan

For this study, samples were collected from three different private dairy farms of crossbred cattle (Sahiwal×Friesian), in Gujranwala Division, Punjab province. A total of 384 blood samples, calculated by using formula for unknown prevalence with 95% confidence interval as described by Thrushfield et al. (2007), were collected through random sampling method at the farms. Information regarding animal age, sex, parity, lactation, pregnancy status and reproductive disorders were recorded on a structured questionnaire. Approximately 5 ml of blood was drawn from jugular vein of each animal in a syringe, allowed to clot, serum separated in an 1.5 ml Eppendorf tube and stored at -20 ºC till further analysis.

Serum samples were screened initially by RBPT and then were evaluated by indirect-ELISA (iELISA) using SVANOVIR® Brucella-Ab iELISA kit (Uppsala, Sweden) as per manufacturer recommendations. Samples with Percent Positive (PP)≥40 were considered positive.

The data on different variables, e.g. age, sex, parity, lactation and pregnancy sero-prevalence were evaluated by Chi-square test. To determine the level of significance, P value < 0.05 was considered as cut off.

*P-value <0.05 considered as significant association.

A total of 384 bovine sera were tested by RBPT and iELISA for brucellosis and were found 111 (28.90%) and 107 (27.86%) sero-positive, respectively. The two tests did not show any statistical significant association (P>0.05) for detection of the sero-prevalence.

Abortion was the most frequently found 12/25 (48%) reproductive disorder among seropositive amimals. Overall, the reproductive disorders associated statistically significant (P=0.0056) with seropositivity for brucellosis (Table I).

Individual livestock parameters such as age, parity, sex, lactation staus and preganancy staus did not show any statistical significant (P>0.05) association with the seropositivity of the disease (Table II).

*P-value <0.05 considered as significant association.

Brucellosis is considered endemic in ruminant animals in Pakistan (Farooq et al., 2011; Ali et al., 2014). Previous studies have indicated seroprevalence of 3-6% depending on the area and animals whereas B. abortus found as main etiology of brucellosis in the country (Ali et al., 2014, 2015, 2017; Abro et al., 2017; Ahmad et al., 2017). The two diagnostic tests did not reveal a significant difference in seropositive animals, may be because of relatively low number of samples. Reproductive disorders, especially repeat breeding and previous abortion history have been found significantly associated with bovine brucellosis (Al-Hassan et al., 2014; Lindahl et al., 2014; Patel et al., 2014; Chaulagain and Bowen, 2016; Geresu et al., 2016; Pathak et al., 2016). However, to the best of our knowledge, only one study in India did not find significant association (Asmare et al., 2013). While breed was foud to have significant association with brucellosis, cross bred cattle are considered more prone to the infection (Asmare et al., 2013; Patel et al., 2014; Chaulagain and Bowen, 2016; Kaleem et al., 2016; Ali et al., 2017). Sex, age and lactation status did not show any significant association in our study, however previous reports do associate sex and lactation status of the animal with the infection (Ibrahim et al., 2010; Ali et al., 2017).

Further studies in different areas of the country coupled with confirmatory diagnosis e.g. isolation and identification of the etiology could help in better understanding the epidemiology of the disease. The isolates could be then analysed further for antibiotic resistance, gene characterization and molecular epidemiology. Vaccination could provide a potential solution. So far, there is no drug of choice against brucellosis in animals , hence culling remains the only choice. Animal movement should be regulated with strict health certificate programmes. Pasturised milk is recommended to avoid transmission to humans. Nationwide public awareness especially in herd’s people is very necessary as they are at the first risk of infection (Ullah et al., 2015). Routine screening of the herd is essential for prevention and control of the infection in the herd.

The study concludes the seroprevalence of the infection in the area and a potential threat in animals at any age, sex and lactation status. Preventive measures an public awareness remain the only hope to control and prevent the infection in animals as well as in humans.

The authors are thankful to the Higher Education Commission (HEC) of Pakistan for their financial support to this study under HEC Indigenous M.Phil leading to Ph.D. fellowship programme. Financial support from German Federal Foreign Office through Friedrich-Loeffler-Institute (FLI), Jena, Germany (Project # je-0113, titled “Brucellosis in Pakistan) is highly appreciated.

The authors declare no conflict of interest.