Abstract
Background:
Brucellosis is a major zoonotic disease with significant implications for animal and human health worldwide. Bacterial culture remains the gold standard for diagnosis; however, it is labor-intensive, time-consuming, and poses biosafety risks. Molecular diagnostic methods offer rapid, sensitive, and safe alternatives for detecting Brucella infections, particularly in resource-limited settings.

Aim:
This study aimed to detect and partially characterize Brucella abortus DNA in sheep and goats from Punjab, Pakistan, using species-specific conventional polymerase chain reaction (PCR) targeting the bcsp31 gene.

Methods:
Whole blood (n = 16) and vaginal swab (n = 5) samples were collected from seropositive and recently aborted small ruminants. DNA was extracted and analyzed by conventional polymerase chain reaction targeting the bcsp31 gene of B. abortus and the IS711 element of Brucella melitensis. Positive polymerase chain reaction products were subjected to partial gene sequencing and nucleotide BLAST analysis for species confirmation.

Results:
B. abortus DNA was detected in 2 out of 5 vaginal swab samples (40%), whereas all whole blood samples tested negative for both B. abortus and B. melitensis. Partial sequencing of the bcsp31 gene from the positive samples revealed 99% nucleotide identity with reference B. abortus strains available in public databases.

Conclusion:
This study provides preliminary molecular evidence of B. abortus infection in small ruminants in Punjab, Pakistan, and highlights the utility of PCR-based diagnosis using vaginal swabs over whole blood. However, the findings should be interpreted cautiously due to the limited sample size, and larger-scale molecular surveillance is recommended to confirm these observations.

Key words: bcsp31 gene; Brucella abortus; Molecular epidemiology; PCR; Small ruminants.