Anthrax in ND cattle
November 23, 2012
Livestock producers in North Dakota and surrounding states should be on the lookout for anthrax outbreaks in their livestock. The ancient disease was confirmed a few weeks ago in a Stark County cattle herd in southwest North Dakota.
Over the years, in northeast, southeast and south central North Dakota, anthrax has occurred more frequently because those river valley areas are susceptible to flooding, providing a habitable environment for anthrax to flourish.
In recent years, anthrax has also been confirmed in livestock in South Dakota, Minnesota, Nebraska, Mississippi, southwest Texas, Louisiana and California. In drought conditions, anthrax spores multiply. With the 2012 drought stretching from Ohio west to California and from Texas north to the Dakotas, conditions are well suited for anthrax outbreaks.
"There were more than 100 cattle in the herd where anthrax was diagnosed," Dr. Susan Keller, North Dakota state veterinarian said. "Only one animal death in the herd was confirmed as resulting from anthrax. There may have been more than one, but if more of the cattle died, the cause of death wasn't confirmed."
“If anthrax is confirmed, vaccinating the remainder of the herd often stops further death loss. Because all animals don’t respond the same to vaccine, we can’t say vaccination is 100 percent effective. However, we’ve seen very good results with anthrax vaccinations.”
Dr. Susan Keller
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Sudden death is the most significant symptom of anthrax. Once an animal contracts the disease, it is likely to die within 24 to 72 hours. Infected animals may display fever, lack of rumination, excitement followed by depression, difficult breathing, uncoordinated movements, convulsions and then death. Bloody discharges from natural body openings as well as edema in different parts of the body may also occur. If antibiotics are administered at onset of the disease, animals can survive.
"The best approach to anthrax is vaccination in late spring, before cattle go to pasture," Dr. Keller said. "If anthrax occurs in a herd, they have to be removed from the pasture where the disease broke out and receive a series of two vaccinations. The most effective practice is to vaccinate early ever year."
Anthrax commonly occurs in tropical countries such as Africa, South and Central America, southern and Eastern Europe, Asia, the Caribbean and the Middle East. However, outbreaks are not uncommon in the United States. It's theorized that areas along the great cattle drive trails of the 1800s were "seeded" with anthrax spores, which can lie dormant in soil for decades.
Bacillus anthracis is the spore-forming bacteria responsible for anthrax. It is a disease of warm-blooded animals,including humans. Swine and dogs are less susceptible to the disease, generally only contracting it through ingestion of heavily contaminated food such as the raw meat of animals that died from the disease or, in the case of swine, infected bone or meat meal given as a feed supplement.
Anthrax is found in two states: spore and vegetative. Spores, which are primarily found in alkaline soils that contain a high nitrogen level formed by decaying vegetation. Alternating periods of rain and drought with temperatures in excess of 60 degrees Fahrenheit serve as "incubator" areas. When animals graze aggressively, there is greater potential that they'll consume soil that contains anthrax bacteria.
The vegetative state of anthrax is found in the carcass of an animal that dies from the disease. If the carcass is opened during necropsy, by scavengers or decay, the vegetative state is exposed to oxygen, which results in formation of spores. Studies have shown the spores to remain viable for more than 50 years.
If a livestock producer suspects anthrax is the cause of animal death, they should not open the carcass. Discharges and blood from the deceased animal are highly infectious both to other animals and humans. An opened carcass will also deposit enormous quantities of bacteria on the ground which will prolong presence of the disease.
Humans can contract anthrax by inhaling spores, so producers should allow veterinarians to carefully handle any carcass when anthrax is suspected. Isolating carcasses from other livestock and pets and protecting it from scavengers is also recommended.
"If anthrax is confirmed, vaccinating the remainder of the herd often stops further death loss," Dr. Keller said. " Because all animals don't respond the same to vaccine, we can't say vaccination is 100 percent effective. However, we've seen very good results with anthrax vaccinations."
Anthrax vaccine for animals has been used for about 40 years. It's made form a nonpathogenic form of the disease, meaning it won't cause anthrax. It has a high margin of safety and good immunizing properties.
An anthrax vaccine for humans was developed in the 1950s and 1960s. It's currently only available to persons working directly with the anthrax organism in laboratory settings and to military personnel deployed to areas where there is a high risk for exposure to anthrax.
Because anthrax spores found in soil don't become airborne, they aren't typically inhaled or ingested by people. Most human anthrax infections occur when the bacterium enters a cut or skin abrasion when handling contaminated wool, hides leather or hair products of infected animals. Skin infection is manifested as an itchy bump similar to an insect bite.
In 2005, in one of the state's largest recorded outbreaks, anthrax killed more than 500 head of cattle, bison, horses, sheep, llamas and farmed deer and elk in North Dakota. Livestock owners are encouraged to check with their veterinarian regarding vaccination methods. A booster vaccination may be in order. Vaccination and antibiotic cannot be administered at the same time.
"Even loss of one animal is never minor to a producer," Dr. Keller said. "The best proactive approach is early vaccination. Check with your veterinarian to develop a prevention and treatment plan."
Additional information about anthrax, including anthrax maps and information about the disease in surrounding states, is available at this North Dakota Department of Agriculture website: http://www.nd.gov/ndda/disease/anthrax.