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Farm and Home Biosecurity
Consumer/General Public and Livestock/Row Crop Producer
Anthrax: Questions and Answers
What is anthrax? Anthrax is an acute infection of virtually all warm-blooded animals, including man, caused by
Bacilllus anthracis. Anthrax most commonly occurs in cattle, horses, mules, sheep, and wild animals, but it can also occur in humans when they are exposed to infected animals or tissues from infected animals.
How common is anthrax and who can get it? Anthrax occurs worldwide. Districts where repeated outbreaks occur exist in southern Europe, parts of Africa, Australia, Asia, and North and South America. In the U.S., there are recognized areas of infection in South Dakota, Nebraska, Arkansas, Mississippi, Louisiana, Texas, and California.
When anthrax affects humans, it is usually due to an occupational exposure to infected animals or their products. Workers who are exposed to dead animals and animal products from other countries where anthrax is more common may become infected with
B. anthracis (industrial anthrax).
How is anthrax transmitted? Anthrax infection can occur in three forms: cutaneous (skin), inhalation, and gastrointestinal. B. anthracis spores can live in the soil for many years, and humans can become infected with anthrax by handling products from infected animals or by inhaling anthrax spores from contaminated animal products. Eating undercooked meat from infected animals can also spread anthrax. It is rare to find infected animals in the United States.
After discharge from an infected animal or when an opened carcass exposes the bacilli to free oxygen, they form spores that are resistant to extremes of temperatures, chemical disinfectants, and desiccation. The spore may persist for long periods in dry products such as feed, animal byproducts, stored contaminated objects, or in soil.
Outbreaks of anthrax commonly are associated with neutral or alkaline, calcareous soils that serve as "incubator areas" for the organisms. Livestock may readily become infected when grazing such areas. Outbreaks originating from soil-borne infections primarily occur in warmer seasons when the minimal daily temperature is above 60° F.
What are the symptoms of anthrax (in humans)? The incubation period is typically 3 to 7 days.
Cutaneous: Most (95 percent) anthrax infections occur when the bacterium enters a cut or abrasion on the skin, such as when handling contaminated wool, hides, leather or hair products (especially goat hair) of infected animals. Skin infection begins as a raised itchy bump that resembles an insect bite but within 1 to 2 days develops into a vesicle and then a painless ulcer, usually 1 to 3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20 percent of untreated cases of cutaneous anthrax will result in death. Deaths are rare with appropriate antimicrobial therapy.
Inhalation: Initial symptoms may resemble a common cold. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is usually fatal.
Intestinal: The intestinal disease form of anthrax may follow the consumption of contaminated meat. It is characterized by an acute inflammation of the intestinal tract. Initial signs of nausea, loss of appetite, vomiting, and fever are followed by abdominal pain, vomiting of blood, and severe diarrhea. Intestinal anthrax results in death in 25 to 60 percent of cases.
In Livestock? The clinical course ranges from peracute to chronic. The peracute form is characterized by sudden onset and a rapidly fatal course. Staggering, difficult breathing, trembling, collapse, a few convulsive movements, and death may occur in cattle, sheep, or goats without any previous evidence of illness.
In acute anthrax of cattle and sheep, there is first an abrupt rise in body temperature and a period of excitement followed by depression, stupor, respiratory or cardiac distress, staggering, convulsion, and death. The body temperature may reach 107° F, rumination ceases, milk production is materially reduced, and pregnant animals may abort. There may be bloody discharges from the natural body openings.
The disease in horses is acute. They may show fever, chills, sever colic, loss of appetite, extreme depression, muscular weakness, bloody diarrhea, and swelling in the region of the neck, sternum, lower abdomen, and external genitalia. Death usually occurs within 2 to 3 days of onset.
In swine, some animals in a group may die of acute anthrax without having shown any previous signs of illness. Others may show rapidly progressive swelling about the throat, which in some cases causes death by suffocation. Many of the group may develop the disease in a mild chronic form and make a gradual recovery. However, some of these, when presented for slaughter as normal animals, may show evidence of anthrax infection in the cervical lymph nodes and tonsils.
Can anthrax be spread from person-to-person? Direct person-to-person spread of anthrax is extremely unlikely to occur.
How is anthrax diagnosed? Anthrax is diagnosed by isolating B. anthracis from the blood, skin lesions, or respiratory secretions or by measuring specific antibodies in the blood of persons with suspected cases.
Is there a treatment for anthrax? Doctors can prescribe effective antibiotics. To be effective, treatment should be initiated early. If left untreated, the disease can be fatal.
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