You, Your Pet and Anthrax

Anthrax is caused by Bacillus anthracis, a bacterium that can form spores. These spores allow it to survive in the soil for long periods of time. Anthrax is primarily an animal disease, occurring most often in hoofed animals such as cattle, sheep, goats, camels and antelopes, which can ingest anthrax spores while grazing. Horses can also acquire anthrax while grazing, but the incidence is lower. Dogs, cats, lions and pigs can contract the disease by eating undercooked meat from infected animals. Birds, reptiles, amphibians and fish are not directly susceptible. Dogs who eat grass cannot contract anthrax.

The incidence of anthrax in the United States is low, due mainly to the effective control of the disease in animals. Areas of higher risk include Central and South America, Southern and Eastern Europe, Africa, Asia, the Caribbean and the Middle East.

Anthrax infection in animals can be respiratory, or intestinal and signs include fever, respiratory difficulty, excitement followed by depression, in coordination, vomiting, diarrhea, bloody discharges, convulsions and death. While Anthrax infections in humans is rare, most cases develop in people whose occupations place them in close contact with livestock or the contaminated products of livestock such as wool, goatskin and pelts. Direct human-to-human transmission of anthrax is extremely unlikely and most experts question if it is possible. Likewise, infected livestock do not infect each other.

Three types of anthrax are seen in people: cutaneous (skin), intestinal and inhalation. The incubation period for the disease is approximately 2 to 7 days. In people, cutaneous anthrax accounts for about 95% of all natural infections and develops when B. antracis enters the skin through existing cuts and abrasions. Without antibiotic treatment, the death rate from cutaneous anthrax is approximately 20%: if appropriately treated death is rare.
Intestinal anthrax results from consumption of contaminated and undercooked meat. Affected individuals may experience nausea, loss of appetite, vomiting and fever, followed by abdominal pain, vomiting blood and severe diarrhea. Mortality is estimated at 25-75%. Human intestinal anthrax has not been reported in the United States during the 20th or 21st centuries.

Inhalation anthrax may initially present as a flu-like illness. While a short period of improvement follows, the patient rapidly deteriorates with high fever, respiratory distress and shock. If left untreated within the first 48 hours, fatalities approach 95%.

A blood culture is the most widely available and useful diagnostic test. Biochemical and microbiologic tests can often provide a definitive diagnosis in 18 to 24 hours; Infection can be prevented and treated with antibiotics. Because the course of the disease is rapid, prompt administration is essential. Effective antibiotics include, ciprofloxacin, doxycycline and amoxicillin.
While vaccination is effective at preventing infection in animals and people, animal vaccines have not been approved for use and should not be administered to humans. A vaccine is available for humans, but population wide vaccination has not been recommended since risk has been considered to be low. Should anthrax become a public health threat, dogs are to be treated by veterinarians with appropriate antibiotics.

The use of B. anthracis as a biological weapon generally relies on aerosolization to cause inhalation anthrax. Fortunately, the aerosolization of infective doses of anthrax spores is not easily accomplished. Decontamination protocols are situation-dependent and are based on anticipated aerosolization risk, spore survival, and environmental conditions.