DefinePK

Abstract

Background: Brucellosis remains a major zoonosis undermining cattle productivity and posing public-health risks through occupational exposure and consumption of unpasteurized dairy. This study estimated the prevalence of brucellosis and identified associated risk factors in cattle kept around Karachi, Pakistan. Methods: A cross-sectional survey was conducted in which 125 samples were collected: 100 blood samples (72 crossbreed, 28 indigenous) and 25 vaginal swabs from clinically suspect animals. Sera were screened using an indirect ELISA. Vaginal swabs were cultured on Brucella selective agar and isolates identified by microscopy and standard biochemical tests. Risk factors, locality, age groups (<4 years, >4 years) and sex were assessed using chi-square tests in SAS 8.1; significance was set at p<0.05. Results: Overall seroprevalence was 8.0% (8/100). Prevalence was higher in crossbreeds cattle (12.0%) than in indigenous breeds (4.0%). By sex, females showed 14.0% positivity versus 2.0% in males (χ²=11.77, p=0.0082). By age, prevalence was 12.0% in >4-year animals and 4.0% in <4-year animals (χ²=5.42, p=0.1434). Locality-wise seroprevalence was highest in Cattle Colony (16.0%), followed by Gulshan-e-Hadeed (8.0%), Sohrab Goth (4.0%) and Malir (4.0%); differences were not significant (χ²=13.14, p=0.1564). Brucella abortus was isolated from 1/25 (4.0%) vaginal swabs but not from blood. Isolates exhibited catalase-, oxidase- and urease-positive, and indole-, methyl-red- and Voges–Proskauer-negative profiles, consistent with B. abortus. Conclusions: Brucellosis is present in Karachi’s cattle population with an 8.0% overall seroprevalence, disproportionately affecting females, older animals and crossbreds. Although locality differences were not statistically significant, the burden concentrated in the Cattle Colony warrants targeted interventions. Surveillance using ELISA, biosecurity improvements (testing of replacements, safe disposal of abortus materials), hygiene at calving, education, and milk pasteurization are recommended to reduce transmission. Future studies with larger, stratified samples and multivariable analyses are needed to quantify the independent effects of husbandry practices and to evaluate vaccination and test-and-segregate strategies suitable for peri-urban dairy systems.