[Image: Horse with swelling]What is anthrax?
Anthrax, often called charbon in south Louisiana, is a fatal, infectious disease of all warm-blooded animals including humans. Anthrax is a reportable disease that often occurs on many farms simultaneously. Prompt diagnosis is essential for alerting livestock and horse owners of the need for protective action.
History of anthrax in Louisiana
Anthrax has been recognized as an important disease of livestock in Louisiana for more than 200 years. Soon after the French arrived, anthrax was observed in deer in the salt marshes west of the mouth of the Mississippi River. The disease has occurred sporadically in coastal pastures of Louisiana and Texas.
Anthrax was occasionally seen along the Red River north of Alexandria before 1960. In 1919, a veterinarian described an outbreak in cattle grazing a swamp pasture along the Comite River north of Baton Rouge at Slaughter. A major outbreak occurred east of Bastrop after the great Mississippi River flood in 1927. In 1946 and 1958, outbreaks of anthrax killed livestock and horses along the Ouachita River east of Monroe. Drought in the Midwest caused the Mississippi River below New Orleans to recede in 1954 and an outbreak followed.
The last major anthrax outbreak occurred in the summer of 1971 in a 10-parish area south and west of Baton Rouge. In the mid 1970s, two smaller outbreaks appeared along U.S. 71 near Morrow. A horse exposed to soil in a pasture where a water well had been drilled recently was confirmed positive for anthrax in 1984, at Folsom. In the late 1980s, a small herd of cattle died of anthrax in Assumption Parish, the last reported case as of May 24, 2005.
What is the source of the infection?
In Louisiana, most outbreaks of anthrax occur during warm weather when the organism Bacillus anthracis is ingested by animals grazing areas previously contaminated by an animal dead or dying of the disease. Spores of the anthrax organism can survive for many years in soil that has a pH above 6.0. Contaminated soil from anthrax graves may be unearthed by ditch digging, bull dozing or similar activities.
The organism does survive in soil with a pH of neutral to alkaline that has been contaminated with blood. Soil contamination occurs when humans, vultures, coyotes or dogs have opened fresh anthrax carcasses or where blood has oozed from the anus or nostrils or from bloody feces.
It is thought that resistant spores remain until favorable conditions allow active growth and reproduction of the organism. Drought followed by heavy rains then dry hot weather often precede anthrax. The anthrax organism is thought to reproduce in decaying plant material at the edges of receding ponds or lakes during drought. Similar areas may be formed where water stands after heavy rains or flooding of pastures. Experts suggest that it is also possible that, during local flooding of pastures, spores are floated to the soil surface and then concentrated as floodwaters dry up.
Animals grazing short grass ingest a considerable amount of dirt, increasing their exposure. When conditions are just right, susceptible animals grazing through a contaminated patch of soil become infected. Signs of illness develop two to 10 days after exposure. These new cases can then be a source of infection.
Soil-borne exposure to humans is apparently of little importance
What signs of illness suggest that anthrax infection is present?
Often a cow, horse, sheep or goat is found dead, with dark blood oozing from the nostrils and anus. The carcass is bloated, with the legs distended shortly after death.
A sick animal may have a fever of 106 degrees or higher, appear depressed and is usually off to itself. Sometimes large swellings appear on the shoulder, brisket or side. A “blackberry jam” stool may be passed. Death comes within hours to two days after signs of illness develop.
Affected swine have difficulty breathing because of swelling in the throat, but they may survive longer than other species.
But how would I know if my animals have anthrax?
Prompt diagnosis of this disease is vital for protection of your animals, your neighbors’ animals and the people handling the sick or dead animals.
It is important that an anthrax carcass not be opened. A veterinarian will draw a small amount of blood from the jugular vein and submit this sample to the Veterinary Medical Diagnostic Laboratory for examination if he or she suspects anthrax.
The veterinarian may do a preliminary examination of the blood before sending it to the lab. Postmortem (necropsy) examination can be conducted if microscopic examination of the blood proves negative. This precautionary step is frequently used by veterinary pathologists receiving suspect animals at the laboratory.
Is there an effective treatment?
Procaine penicillin G intramuscularly or oxytetracycline IV or subcutaneously are known to be effective in animals found sick in the early stages of the disease. Antibiotic treatment should be continued for five days.
How are contaminated carcasses and body discharges disposed of?
If[Image: Recovering cow] carcasses are opened, exposing the anthrax organism to air, it will form resistant spores capable of surviving for years. The organisms die in unopened carcasses. Carcasses should be buried or burned where found, if at all possible, so that contaminated feces, urine and blood discharges will not be spread about. A 10 percent lye solution (sodium or potassium hydroxide) can be used as a disinfectant. Personal protection gear is necessary when this caustic agent is used.
Disposal should be supervised by a state or federal veterinarian. It is important that the carcass, blood and other discharges be burned or buried. Complete burning of the carcass and grass, soil contaminated by discharges requires a considerable amount of fuel (old tires, wood, kerosene). Deep burial of the carcass and contaminated soil, etc., is another approved method, where appropriate. The carcass should be at least 6 feet deep and covered with lime to discourage scavengers, before soil is added. During outbreaks, parish police jury backhoes have been used to bury dead animals.
How do I protect my animals when anthrax is diagnosed on my farm or in the area?
Vaccination using Sternes non-encapsulated spore vaccine will induce protection for most animals within eight days. This protection is strong, probably lasting one to two years. Supply could be limited during an outbreak.
Animals sick at time of vaccination should be treated with antibiotics for several days. They should be held separately from the herd, then vaccinated seven days after the last dose of antibiotic. The antibiotic will interfere with the action of the vaccine.
Sternes is a live vaccine that will not cause anthrax. Swelling may occur at the injection site. The vaccine is safe. Vaccinated dairy cattle or goats do not have to have milk withheld from market. It is suggested that vaccinated animals not be slaughtered for food for 60 days. Read the insert information sheet that accompanies the vaccine.
Are there other ways, other sources of infection?
Yes, there are. For this reason, anthrax positive cases should be investigated to determine the source.
Animal origin feed materials such as bone meal, meat byproducts, meat meal, possibly certain fertilizer materials, discharges or wastes from tanneries and carcasses fed to zoo animals have been sources of anthrax exposure in other regions of this nation and in other countries.
Large biting flies are capable of transmitting anthrax from sick animals, but this is apparently not a significant route of exposure.
Dogs feeding on anthrax carcasses have developed intestinal anthrax in previous Louisiana outbreaks. Their bloody stool material spreads the disease.
Skinning a carcass to “save the hide” has led to anthrax carbuncles in the skin of p[Image: anthrax pasture]eople. Veterinarians are obviously at risk while doing necropsies on animals.
What actions do the state animal health authorities take when anthrax is diagnosed?
The Office of the State Veterinarian, Louisiana Department of Agriculture and Forestry, is notified of confirmed anthrax cases. Veterinarians and animal owners are alerted. Recommendation is made for immediate vaccination of all livestock and horses in the area of the outbreak. People are urged to report sick or dead animals or to have a veterinarian collect specimens for diagnosis.
To stop movement of animals, quarantines may be placed on the premises where anthrax has occurred. This may be extended to a larger area if circumstances warrant. Road blocks may be established to restrict animal movement.
An investigation is made to determine if some source (feedstuffs, mineral mixes, etc.) other than soil is involved.
If the outbreak is large and widespread, the state police, sheriff’s departments and police juries may help control movement of horses and livestock and may help with proper burial of carcasses. Quarantines may be in place for two to three weeks after the last confirmed case. This should provide adequate time for animal owners to vaccinate their animals. Each outbreak may have a different set of circumstances and require different degrees of action.