Control and Prevention of Anthrax, Texas, USA, 2019

Tom Sidwa; Johanna S. Salzer; Rita Traxler; Erin Swaney; Marcus L. Sims; Pam Bradshaw; Briana J. O'Sullivan; Kathy Parker; Kenneth A. Waldrup; William A. Bower; Kate Hendricks


Emerging Infectious Diseases. 2020;26(12):2815-2824. 

In This Article

Public Health Implications and Conclusion

Anthrax is endemic to parts of the United States. Epizootics emerge with varying frequency when climatic conditions favor the uncovering of soilborne B. anthracis spores with subsequent consumption by susceptible herbivores. Humans contract cutaneous anthrax through contact with animals that are ill or have died from anthrax or contact with B. anthracis–contaminated byproducts; this risk is increased during epizootics. The outbreak we describe was confirmed in June 2019, but its actual start date is unknown; reliable recognition of epizootics might be impeded when they occur in vast, rough, and sparsely populated areas such as those in the anthrax-endemic areas of Texas. These same geographic characteristics create challenges in implementing the recommended disease control interventions, including appropriate carcass disposal and broad use of animal anthrax vaccine in species for which the vaccine is licensed, as well as off-label use in other species. Wild herbivores (e.g., white-tailed deer and exotic hoofstock) contributed to the 2019 Texas outbreak, but effective mitigation (carcass disposal or vaccination) of the risk they posed could not be adequately achieved.

The cutaneous anthrax patient associated with this outbreak was apparently exposed through a scratch on the leg from the antler of an untested deer carcass. The physician he visited in rural Texas included anthrax in the differential diagnosis, obtained and submitted diagnostic samples before treating the patient, and provided the patient with a prescription for oral ciprofloxacin. Anthrax was identified through PCR and confirmed through culture at the state reference laboratory from swab specimens of a leg lesion. The patient was treated as an outpatient with appropriate antibiotics until his condition worsened and required a 13-day hospitalization. The necessity for hospitalization might have been related to a few-week delay in seeking treatment. Despite the delay, the patient, like most patients with cutaneous anthrax, survived with antibiotic treatment.[4,32]

As soon as anthrax is recognized in an animal population, public health and animal health agencies must collaborate to heighten awareness among medical and animal health communities, as well as among ranchers and other inhabitants of at-risk areas. Timely delivery of information to ranchers on proper carcass disposal and appropriate use of personal protective equipment, as was done through various alerts, might reduce the number of exposures. If exposure is recognized, antibiotic PEP should be considered by medical providers. AVA may be appropriate for persons at high risk for exposure, such as veterinary staff and ranch workers in endemic areas; however, this process involves a long-term commitment to annual booster shots to ensure protection.

Ranchers and veterinarians should receive authoritative information on animal vaccine use to break the cycle of transmission (including emphasis on avoiding administration of antibiotics 10 days before or after vaccine administration). Even in the absence of a recognized anthrax outbreak, veterinarians and ranchers in endemic areas should keep anthrax in mind as they interact with ill members of susceptible species. Doing otherwise might result in inadvertent exposure to anthrax. A survey of ranchers in the outbreak area is planned by TAHC to assess knowledge, attitudes, and practices regarding anthrax, including information on livestock vaccination.

Recent federal anthrax guidance has focused on the treatment of systemic anthrax, including meningitis, rather than on the more common cutaneous form of the disease. Given that half the cases in the 2001 anthrax incident in the United States[37] were cutaneous anthrax and most sporadic cases in the United States and worldwide are cutaneous, this article provides an overview of prevention and control measures for animals and a single resource for the prevention, diagnosis, infection control, and treatment of naturally acquired cutaneous anthrax.