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

Texas Outbreak 2019

Animal Cases

Texas Veterinary Medical Diagnostic Laboratory confirmed the first anthrax case of 2019 in an exotic antelope carcass from Uvalde County on June 19. Overall in 2019, the laboratory reported 25 culture-positive animals, including cattle, horses, white-tailed deer, antelope, and a goat, from Crockett, Kinney, Sutton, Uvalde, and Val Verde counties. The last confirmed animal case was reported on August 21. Unconfirmed numbers reported to DSHS staff suggest that >1,000 animal losses might be attributed to the 2019 outbreak (K. Waldrup, unpub. data).

Implementing control measures (i.e., vaccination and proper carcass disposal) was challenging; thin topsoil over bedrock, vast and inaccessible terrain, and burn bans triggered by hot, dry weather conditions made it difficult for livestock owners and landowners to identify and bury or burn dead animals. Livestock owners can sometimes cover dead animals with tarps if burial or burning is not an option. However, because properties in this area of Texas can be thousands of acres and not particularly navigable, reaching dead animals to cover and protect them from scavengers (that might further distribute B. anthracis–contaminated remains) is often not feasible.

Another obstacle to controlling the outbreak was the inability to address the contribution of wildlife to the initiation and perpetuation of disease spread (e.g., lack of a licensed vaccine and impracticality of using physical or chemical restraint to administer vaccine "off label" to wildlife species). In addition, reports of vaccine-associated adverse events among goats and horses[2,10] made some owners reluctant to vaccinate these species. Among confirmed animal anthrax cases in species for which vaccination is indicated (cattle, goats, horses, sheep, and swine),[11] a third are reported to have been vaccinated before illness. Of those, the median number of days from most recent vaccination to specimen collection was 8 days (range 3–82 days) (T. Sidwa, unpub. data). The frequency and effect of antibiotic use subsequent or simultaneous to vaccination was unknown.

Human Case Report

On July 23, 2019, a non-Hispanic White man in his 70s from the anthrax-affected area who had a history of cardiovascular disease and hypertension visited his physician for evaluation of 2 lesions near his right knee. Four days earlier, a small red spot had emerged and gradually enlarged and became painful. He reported no fever and used no over-the-counter medications. When asked about animal exposures because of where he lived, he reported that he and his daughter had moved 2 fly-covered deer carcasses from beneath his porch before lesion onset. He was wearing shorts and a shirt while moving the carcasses, and his affected leg was scraped by the velvet-covered antlers. He also reported being bitten by a fly. The deer carcasses were not tested for anthrax, and the patient disposed of them.

On examination at his physician's office, the patient's vital signs were as follows: blood pressure 177/87 mm Hg; heart rate 76 beats/min; and temperature 98.3°F. Below and lateral to his right knee was an indurated, raised, erythematous 5-cm lesion with small ulcerations that oozed serosanguinous fluid and was surrounded by a blanched halo. Just proximal to his right knee was a nonindurated erythematous macule (Figure 2). No popliteal or inguinal adenopathy was present. After 2 swab specimens were obtained from the larger lesion, the patient was given a cephalosporin intramuscularly, and a prescription for ciprofloxacin was called in to his pharmacy of choice more than an hour's drive from his home. Because it was too late to send the specimens anywhere for testing on that day, the swabs were mailed directly to the Texas Department of State Health Services Laboratory on Wednesday after a phone consultation with the state health department.

Figure 2.

Lesions on right leg of anthrax patient as seen on outpatient visit, Texas, USA, 2019.

The patient began his ciprofloxacin the next evening (July 24). On July 26, after having taken 4 doses of his antibiotics, he was feeling worse and sought additional care at the emergency department of hospital A, more than an hour's drive from his residence. Concurrently, the state laboratory notified his primary-care physician that a preliminary laboratory report for the specimen was PCR-positive for B. anthracis; this result was confirmed by culture the following week (August 1) (Figures 3, 4). His physician relayed the information first to the patient and then to hospital staff. Upon arrival to the hospital, the patient reported pain, difficulty walking, and nausea. He reported intermittent spontaneous drainage of a dark, jelly-like material from the larger wound. He reported no fever, chills, chest pain, shortness of breath, pain at rest, numbness, or tingling. He did not use tobacco products.

Figure 3.

Bacillus anthracis 24-hour growth on sheep blood agar from a swab of a cutaneous anthrax lesion from a patient in Texas, USA, 2019. Typical ground glass colony morphology and lack of hemolysis are shown.

Figure 4.

Gram stain from culture of a lesion of an anthrax patient, Texas, USA, 2019.

At hospital A, he reported that his exposure had been ≈3 weeks earlier. At examination, his vital signs were blood pressure 132/71 mm Hg; heart rate 91 beats/min; and respirations 24 breaths/min. He was afebrile. He had a nondraining, nonerythematous eschar 7.2 cm × 5 cm on the lateral aspect of the right calf and a painless, nondraining, nonerythematous 3.3 cm × 2 cm eschar on the lateral aspect of the right knee (Figure 5). His leukocyte count was 12,000 (103 cells/μL); hemoglobin, 15.5 g/dL; hematocrit, 46.9% g/dL; platelets, 83,000 (103 cells/mL); blood urea nitrogen, 35 mg/dL; and creatinine, 2.6 mg/dL. His antibiotic was switched to intravenous doxycycline (100 mg every 12 hours). He was discharged on hospital day 13.

Figure 5.

Eschars on right leg of anthrax patient as seen at hospital admission, Texas, USA, 2019.