Anthrax

Agricultural Disaster Preparedness and Recovery November 04, 2011|Print
Dead cattle

Anthrax is a disease that infects people and livestock and is caused by the spores of the bacteria Bacillus anthracis. Anthrax spores can survive in soil for decades. Animals contract anthrax by ingesting or inhaling spores. Sheep, cattle and horses are especially susceptible to anthrax. Spores are shed in bloody discharges of infected animals and can spread throughout a herd.

Endemic Areas

Anthrax is found worldwide.

Outbreaks typically occur when livestock are grazing on neutral or slightly alkaline soil. Infection in animals usually is the result of grazing on infected pasture land. The organisms enter through an animal's mouth, nose or skin injuries. Following ingestion or inhalation, the organism spreads rapidly throughout the body.

 

burning cattle carcasses

Dead animals that have been opened but not burned or buried provide an ideal source for the organism. Cremating carcasses is imperative to prevent spread of the disease. If cremation is not possible, carcasses should be buried deep and covered with quicklime before covered with soil. Quicklime is calcium oxide (CaO) and should be used with extreme care because it can cause severe burns.


Flooding pastures with contaminated water or dumping infected carcasses in streams or ponds can spread anthrax spores. Flooding readily contaminates low-lying ground or marshy areas and resultant stagnant waterholes may serve as sources of infection. Hay infested with spores may account for winter outbreaks of anthrax. However, anthrax predominantly is a warm-weather disease.

The safest use of soil infected with the anthrax organism is to raise cultivated crops.

Anthrax may be spread through wounds from blood-sucking insects, dehorning, castration or other surgeries. Outbreaks have occurred because of contaminated feed, particularly bone meal, meat scraps and other animal protein products. However, current regulations of the manufacture and importation of such animal products virtually eliminates these sources of infection.

Humans can become infected by handling contaminated hides or wool (Woolsorter's Disease) or by examining infected carcasses.

 

Clinical Signs

Signs of illness associated with anthrax depend on the species involved and route of infection. When anthrax organisms enter via the nose or mouth, signs of illness occur quickly (acute form) and death follows rapidly. When infection takes place through the skin, the site of injury becomes hot and swollen, then cold and insensitive. Later, the infection can become generalized.

Anthrax usually is a fatal disease with no signs observed. Upon or near death, blood oozes from body openings of affected animals. This blood is heavily laden with anthrax organisms. Infected carcasses have marked bloating and decompose rapidly.

If the infection is less acute, animals may stagger, have difficulty breathing, tremble, collapse and die. Colic may be observed in horses. Edema and swelling can be seen over the body, particularly at the brisket. Illness is observed from one to five days. Signs are preceded by fever with a period of excitement in which the animal may charge nearby humans. This is followed by depression in cattle or sheep.

Sometimes the anthrax organism localizes itself in the throat area. The tongue, throat and neck are extremely swollen and a frothy blood-tinged discharge comes from the mouth. Although this is the typical form of anthrax observed in swine, it also may occur in cattle and sheep.

Cattle and Sheep

  • Sudden death
  • Staggering
  • Difficulty breathing
  • Fever
  • Disorientation
  • Abortion
  • Bloody discharge from mouth, nose and anus

Horses

  • Fever
  • Chills
  • Anorexia (poor appetite)
  • Depression
  • Colic
  • Bloody diarrhea

Pigs/Carnivores

  • Sudden death
  • Swelling of throat
  • Difficulty breathing
  • Difficulty swallowing

Diagnosis

Not all cases of "sudden death" are anthrax, but if livestock owners suspect anthrax, laboratory tests should be conducted.

If anthrax is suspected, do not open up the carcass and perform a necropsy. Using aseptic technique, a veterinarian should collect a venous blood sample and send it to a diagnostic laboratory in a sealed, sturdy, leak-proof, iced container with an accompanying history and identifying it as an anthrax suspect. Some veterinary diagnostic laboratories have special anthrax specimen collection kits available for veterinarians to use.

Isolation of the anthrax organism becomes very difficult if the animal has been dead for 48 hours or more because bacteria that invade dead tissue may overgrow Bacillus anthracis. Therefore, a negative diagnosis from an animal that died from anthrax is possible.

 

Treatment and Control

Anthrax sensitivity plate

Any animal suspected of having anthrax should be reported to the State Veterinarian or the USDA Area Veterinarian in Charge immediately.

Anthrax is highly fatal and treating affected animals is difficult. Penicillin is the antibiotic of choice. Response to treatment varies; best results are obtained when drugs are administered early during an outbreak. If using antibiotics, vaccination with an anthrax vaccine should be delayed for two to five days depending on the antibiotic used. The vaccine is a spore vaccine and antibiotics may interfere with proper immunization of the animal. However, when faced with an outbreak situation, administering an antibiotic and a vaccine concurrently has been effective. Consult your local veterinarian for recommendations.

An effective vaccine is available (nonencapsulated, Sterne 34F2 strain). Since anthrax is a reportable disease, details on the use of the vaccine should be coordinated through the office of the State Veterinarians. It is relatively safe and provides effective protection on most species of livestock. Use caution when administering it to horses. Cases of Clostridial infections have been reported in horses at the injection site where the horses were vaccinated during a rainfall or when the horses had wet hair coats.

If using an anthrax vaccine, follow all label directions for proper withdrawal times, including withholding of milk and meat products from the market.

Disposal

Burn pit
Figure A
Figure B
Figure C

The carcass and all materials associated with it should be destroyed and the ground should be disinfected. This can be very difficult. The preferred method of destruction is incinerating the carcass. If this is not possible, burying the carcass at least 6 feet deep and covering it with quicklime is acceptable.


The following are general recommendations for burning a 1,000-pound carcass: Dig a pit about 2 feet deep and exceeding the length and breadth of the carcass by about 1 foot on each side (Figure A). Dig a trench 1 foot by 1 foot along the length of the center of the pit extending beyond the ends of the pit by about 3 feet; this serves as an air duct for the fire under the carcass (Figure B). Fill the trench and cover the bottom of the pit with straw; soak it with an accelerant (kerosene or diesel fuel) (Figure C).

 

Cut heavy timbers such as railroad ties or pallets to fit across the trench and within the sides of the pit and place them on top of the straw. Add other pieces of wood or coal until the pit is filled to the level of the ground surface. Depending on the location of the carcass, environmental rules and extenuating circumstances, tires have been used with or in place of wood or coal. Saturate all of this with accelerant.

The carcass then can be lifted or drawn onto the pyre (combustible heap). Pour more accelerant over the carcass. Carefully ignite the fire at either end of the trench. Once the incineration is well under way (probably after the first hour), cover the pyre with corrugated metal or other metal sheeting to retain heat but not lose ventilation.

If blood and body fluids have contaminated the ground and material under the animal, they should be incinerated as well. Remove soil deep enough to collect any blood and body fluids that have seeped into it. This could be up to 6 inches. This material can be placed on top of the carcass prior to igniting the pyre (Figure C).

The approximate quantities of fuel that will be needed are 100 pounds of straw, 2½ gallons of accelerant and 2 tons of wood or ½ ton of wood and ½ ton of coal. Anecdotal evidence would indicate that at least 18 automobile tires are needed for good incineration.

If soil and other related materials cannot be incinerated, it can be disinfected with 5 percent formaldehyde solution at 50 quarts per square yard. WARNING: formaldehyde is toxic to fish and should not be used near water.

After incineration, cover ashes and contaminated soil with soil removed from pit.

Personal Protection

If producers suspect anthrax, have a veterinarian aseptically collect a jugular blood sample for culture. DO NOT NECROPSY THE ANIMAL.

Producers should take every precaution to avoid skin contact with the potentially contaminated carcass and soil. They should use protective, impermeable clothing and equipment such as rubber gloves, rubber apron and rubber boots with no perforations. Do not expose any skin, especially that compromised with wounds or scratches. Disposable personal protective equipment is preferable, but if not available, wash any exposed equipment in hot water and detergent to achieve decontamination. Burn and bury disposable personal protective equipment with the carcass.

To clean equipment used for digging the pit and moving the carcass, remove dirt, blood, hair and other materials with hot water and detergent. Divert the wash water from the equipment into the pit for incineration. A diluted bleach solution (one part bleach to 10 parts water) can be sprayed on the clean equipment to further decrease the likelihood of anthrax being present. Let this solution air dry on the equipment. The risk of anthrax being spread via equipment used to dig the pit is unknown, but most likely is very small. The site where the animal died is not necessarily where the animal acquired the infection.

The Bacillus anthracis organisms range from 0.5 to 5 micrometers in size. Veterinarians and producers working with anthrax suspects or confirmed cases should wear respiratory equipment capable of filtering this size of particle. They should use a National Institute for Occupational Safety and Health (NIOSH) and Mine Safety and Health Administration (MSHA)-approved high-efficiency respirator, such as a half-face disposable respirator with a high-efficiency particulate air (HEPA) filter, when conducting soil remediation and burial and applying quicklime to soil.

Public Health

cutaneous anthrax

 

cutaneous anthrax

Anthrax is zoonotic meaning it can be transmitted from animals to people. The most common form of anthrax in people is cutaneous (in the skin). This form of anthrax is characterized by a raised, itchy bump similar to a bug bite that develops into an ulcer with a black center. This characteristic ulcer gives the Anthrax bacteria its name (anthracis derives from the Greek word for coal, anthrakis). Cutaneous anthrax is easily treated and rarely fatal if treated early. If left untreated, cutaneous anthrax has a case-fatality rate of 30 percent.

The intestinal form of anthrax occurs by eating undercooked meat contaminated with the spores. The symptoms of intestinal anthrax include nausea, abdominal pain, vomiting of blood and diarrhea. This form of anthrax can be fatal in up to 60 percent of cases.

Inhalation of anthrax spores leads to the most severe form of the disease. However, inhalation anthrax is rare. Signs of inhalation anthrax are similar to a cold but can progress to severe breathing problems and shock. Inhalation anthrax is usually fatal.

People most likely to become infected with anthrax are those working closely with herbivores or their products, including hides and wool. Anthrax is not spread from person to person.

Anthrax may be used as a weapon for bioterrorism. If you suspect intentional anthrax contamination, contact local law enforcement immediately.

 

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