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

Disclosures

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

In This Article

Abstract and Introduction

Abstract

The zoonotic disease anthrax is endemic to most continents. It is a disease of herbivores that incidentally infects humans through contact with animals that are ill or have died from anthrax or through contact with Bacillus anthracis–contaminated byproducts. In the United States, human risk is primarily associated with handling carcasses of hoofstock that have died of anthrax; the primary risk for herbivores is ingestion of B. anthracis spores, which can persist in suitable alkaline soils in a corridor from Texas through Montana. The last known naturally occurring human case of cutaneous anthrax associated with livestock exposure in the United States was reported from South Dakota in 2002. Texas experienced an increase of animal cases in 2019 and consequently higher than usual human risk. We describe the animal outbreak that occurred in southwest Texas beginning in June 2019 and an associated human case. Primary prevention in humans is achieved through control of animal anthrax.

Introduction

The zoonotic disease anthrax, caused by the bacterium Bacillus anthracis, has been known to humankind for thousands of years and is endemic to most continents.[1–3] It is a naturally occurring disease of herbivores that incidentally infects humans through contact with animals that are ill or have died from anthrax or through contact with B. anthracis–contaminated byproducts such as meat, hides, hair, and wool.[4] Transmission routes include cutaneous, ingestion, inhalation, and injection; cutaneous accounts for most (95%) cases worldwide.[2,4] In the United States, human risk is primarily associated with handling carcasses of hoofstock that have died of anthrax; the primary risk for herbivores is ingestion of B. anthracis spores that can persist in suitable alkaline soils in a corridor from Texas through Colorado, the Dakotas, and Montana.[5–7]

The 2 state agencies responsible for anthrax surveillance in Texas are the Texas Department of State Health Services (DSHS) and the Texas Animal Health Commission (TAHC). Samples that are culture-positive for B. anthracis at veterinary reference laboratories are reported to DSHS and TAHC. Veterinarians treating animals with illnesses compatible with anthrax must also report to DSHS and TAHC. Suspected cases of human anthrax are immediately reportable to DSHS. Samples or isolates from human cases are forwarded for identification to local public health reference laboratories. In Texas, animal anthrax cases are most commonly reported from the triangular area bounded by the towns of Uvalde, Ozona, and Eagle Pass (Figure 1), which includes portions of Crockett, Val Verde, Sutton, Edwards, Kinney, Uvalde, Zavala, and Maverick Counties in southwestern Texas.

Figure 1.

Counties with confirmed animal anthrax cases, Texas, USA, 2000–2019. The location of the "Anthrax Triangle" is indicated.

During 2000–2018, a total of 63 animal anthrax cases were confirmed by culture of B. anthracis in a reference laboratory (annual mean 3.3, range 0–20 cases/year) (T. Sidwa, unpub. data). Because only 1 animal per affected premise usually is reported in a given year, the number of cases is a substantial underrepresention of the total number of affected animals and properties. The last naturally occurring human case of cutaneous anthrax associated with livestock exposure in Texas was reported in 2001.[8,9]

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