Hair and wool of ruminants and canines as environmental vectors of Bacillus anthracis and potential human exposure in anthrax-endemic regions

Anthrax is an endemic and persistent zoonotic disease in Pakistan. This fact emphasizes the need for surveillance in high-risk endemic regions. The aim of this study was to assess the role of wool and hair of ruminants and canines in the transmission of Bacillus anthracis, the causative agent of anthrax, and to evaluate the exposure to anthrax in asymptomatic animals and humans. Samples from five districts were analyzed using microscopic methods, culture methods (on both PLET and blood agars) and PCR. Additionally, to check the exposure, ELISA was performed on animals and human samples. Interestingly, 114/441 (25.85%) samples exhibited Gram-positive rods and characteristic spore-forming bacilli. Culturing on selective media (PLET) and blood agar resulted in characteristic growth in 42 (9.52%) of samples. These 42 samples were confirmed for B. anthracis by PCR. The ELISA findings indicated exposure to anthrax in both animals and humans. The exposure rate in human samples varied across exposure groups, and the highest exposure was detected in humans exposed to the sheep (33%) and goats (33%), indicating zoonotic potential by small ruminants. The high degree of spore contamination indicated that the sole use of conventional microscopy may lead to an overestimation of anthrax prevalence. For accurate detection of anthrax, the present study suggests the need to integrate bacterial culture with molecular methods, e.g., PCR. These results highlighted the role of small ruminants as potential reservoirs and the need for strict biosecurity measures to mitigate the transmission of anthrax in endemic regions.