Human anthrax in a non-epizootic area: epidemiological investigation and response based on One Health-Chengdu, China

Anthrax, caused by Bacillus anthracis, is endemic in western China's pastoral regions. Urban areas adjacent to these regions face a growing threat from the unregulated or poorly monitored livestock trade. This study reports the first documented outbreak of cutaneous anthrax in Chengdu, a non-epizootic city, which originated from the slaughter of infected cattle imported from an epizootic area.

A multidisciplinary team applied the "One Health" approach to investigate the outbreak. The investigation included case details, symptoms, laboratory results, potential sources of infection, suspected contaminated environments, local natural landscapes related to animal husbandry practices, disease incidence rates, slaughtering process, and vaccination history. A risk assessment focused on human, animal, and environmental factors to guide containment measures.

Two cutaneous anthrax cases were confirmed, epidemiologically linked to the unprotected handling of cattle imported from Aba Prefecture. B. anthracis was detected via qPCR in samples from a patient's skin lesions, beef, viscera, and forage; environmental samples were negative. Blood cultures showed no bacterial growth. Interventions included disinfection (10,000 mg/L chlorine), livestock culling, and incineration of traced beef. Approximately 30% of sold meat remained untraceable due to cash transactions, indicating surveillance gaps. Initial misdiagnosis as "insect bites" delayed confirmation by 4-6 days. Both patients recovered following antibiotic treatment, developing eschars with no fatal outcomes. Environmental assessments indicated ongoing risk due to unsealed soil and poor biosecurity.

This outbreak underscores the systemic risk of anthrax in non-epizootic urban areas due to unregulated or poorly monitored livestock trade and poor farm biosecurity. While the One Health approach enabled effective containment, it revealed critical gaps in market oversight and diagnostics. Key recommendations include implementing integrated surveillance, mandatory electronic tracing, training for healthcare workers, and stricter quarantine enforcement to prevent zoonotic spillover.