How common is anthrax?
The following information was taken from the Centers for Disease Control: Web site is: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/anthrax_g.htm#, " How common is anthrax and who can get it?"
What is anthrax? Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. Anthrax most commonly occurs in wild and domestic lower vertebrates (cattle, sheep, goats, camels, antelopes, and other herbivores), but it can also occur in humans when they are exposed to infected animals or tissue from infected animals.
Why has anthrax become a current issue? Because anthrax is considered to be a potential agent for use in biological warfare, the Department of Defense (DoD) has begun mandatory vaccination of all active duty military personnel who might be involved in conflict.
How common is anthrax and who can get it? Anthrax is most common in agricultural regions where it occurs in animals. These include South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East. 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). Anthrax in wild livestock has occurred in the United States.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. Anthrax can also be spread by eating undercooked meat from infected animals. It is rare to find infected animals in the United States.
What are the symptoms of Anthrax? Symptoms of disease vary depending on how the disease was contracted, but symptoms usually occur within 7 days.
- Cutaneous: Most (about 95%) 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 1–2 days develops into a vesicle and then a painless ulcer, usually 1–3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20% 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 and is characterized by an acute inflammation of the intestinal tract. Initial signs of nausea, loss of appetite, vomiting, fever are followed by abdominal pain, vomiting of blood, and severe diarrhea. Intestinal anthrax results in death in 25% to 60% of cases.
Where is Anthrax usually found? Anthrax can be found globally. It is more common in developing countries or countries without veterinary public health programs. Certain regions of the world (South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East) report more anthrax in animals than others.
Can Anthrax be spread from person to person? Direct person–to–person spread of anthrax is extremely unlikely to occur. Communicability is not a concern in managing or visiting with patients with inhalational anthrax.
Is there a way to prevent infection? In countries where anthrax is common and vaccination levels of animal herds are low, humans should avoid contact with livestock and animal products and avoid eating meat that has not been properly slaughtered and cooked. Also, an anthrax vaccine has been licensed for use in humans. The vaccine is reported to be 93% effective in protecting against anthrax.
What is the anthrax vaccine? The anthrax vaccine is manufactured and distributed by BioPort, Corporation, Lansing, Michigan. The vaccine is a cell–free filtrate vaccine, which means it contains no dead or live bacteria in the preparation. The final product contains no more than 2.4 mg of aluminum hydroxide as adjuvant. Anthrax vaccines intended for animals should not be used in humans.
Who should get vaccinated against anthrax?
The Advisory Committee on Immunization Practices has recommend anthrax vaccination for the following groups:
- Persons who work directly with the organism in the laboratory
- Persons who work with imported animal hides or furs in areas where standards are insufficient to prevent exposure to anthrax spores.
- Persons who handle potentially infected animal products in high–incidence areas. (Incidence is low in the United States, but veterinarians who travel to work in other countries where incidence is higher should consider being vaccinated.)
- Military personnel deployed to areas with high risk for exposure to the organism (as when it is used as a biological warfare weapon).
The anthrax Vaccine Immunization Program in the U.S. Army Surgeon General's Office can be reached at 1–877–GETVACC (1-877-438-8222). http://www.anthrax.osd.mil
Pregnant women should be vaccinated only if absolutely necessary.
What is the protocol for anthrax vaccination? The immunization consists of three subcutaneous injections given 2 weeks apart followed by three additional subcutaneous injections given at 6, 12, and 18 months. Annual booster injections of the vaccine are recommended thereafter.
Are there adverse reactions to the anthrax vaccine? Mild local reactions occur in 30% of recipients and consist of slight tenderness and redness at the injection site. Severe local reactions are infrequent and consist of extensive swelling of the forearm in addition to the local reaction. Systemic reactions occur in fewer than 0.2% of recipients.
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.
Editorial Note from JP: With the recent news from Florida about the gentleman who died from anthrax, I thought some cattle background on this subject may be appropriate. The following was taken from a Nebraska Extension publication and was written by Dr. John Gamby, Veterinarian, Dr. Roger Sahara, NE Dept. of Ag. Field Veterinarian and Dr. Dale Grotelueschen, Extension Veterinarian
Anthrax killed 23 head of cows and calves on a Sheridan county Nebraska ranch in June 1994. Bacillus anthracis was confirmed on culture by the Panhandle Veterinary Diagnostic Laboratory, Scottsbluff, Nebraska and the National Veterinary Services Laboratory, Ames, Iowa. The following observations from this case are offered to veterinary practitioners encountering herds where anthrax is a part of the differential diagnosis. Please consult textbooks for specifics regarding this disease.
Postmortem Diagnosis
If anthrax is suspected in any fresh dead animal, collection of blood in a lavender (EDTA) or yellow (Heparin) vacutainer tube from any peripheral blood vessel is suggested. A blood smear should be prepared with Gram or Giemsa stain, and if anthrax is the cause of death large numbers of typical Gram–positive bacilli will likely be present. In this case the local hospital laboratory prepared slides and provided a tentative diagnosis within hours of collecting the sample.
Blood samples should be forwarded to a UNL Veterinary Diagnostic System Laboratory for confirmation by culture. Tissues may be cultured for confirmation if a necropsy has been done. However, opening the carcass, if anthrax is a likely diagnosis, is not advisable. Precautions against personal exposure must be taken.
Clinical Diagnosis
The predominant clinical sign in affected cattle was a progression from normal appearing to dead in a matter of hours. A number of cattle were found dead. Intermandibular swelling extending into the jugular furrow was noted on most of the animals. Severe dyspnea, with head held low and outstretched, was common. Tremors and rapid progression to sternal or lateral recumbency was noted. One animal walked the fenceline constantly with head outstretched, dyspnea and anxious expression.
Blood samples were obtained from slightly affected, severely affected, and freshly dead animals. All contained large numbers of the bacteria on stained blood smears.
Treatment with Anthrax as Tentative Diagnosis
Animals appearing to be affected or having high temperatures were given high dosages of antibiotics (50 ml of long-acting Penicillin — 300,000 IU/ml). Response to antibiotic therapy was very good if given early, appearing to stop the septicemia in clinically ill cattle. All exposed cattle should be given prophylactic long–acting antibiotics as soon as possible. The State Veterinarian’s office must be contacted to report the disease and request approval to order and use anthrax vaccine. Thraxol (Miles Laboratories) and Anthrax Spore Vaccine (Colorado Serum) are both available.
Cattle were moved to a different pasture immediately and vaccine was given as soon as possible. The vaccine provides protective immunity starting about day 3–5 following vaccination. A booster vaccination was given according to label directions. Close observation and antibiotic therapy appears to stop death loss until the vaccine can provide immunity. No adverse side effects to the vaccine were noted.
Disposal of Dead Animals
Animals which may have died of anthrax should not be picked up by the rendering truck. The State Veterinarian’s office should be notified and will supervise disposal of carcasses. A burial pit should be dug and dead animals should be buried as soon after death as possible under direction of state regulatory personnel. Remember that this organism sporulates if the carcass is opened or allowed to decompose above ground.
Human exposure
A physician should be contacted for the best preventative measures for all exposed or potentially exposed persons. Remember, this is a potential human pathogen that can be fatal, so appropriate measures must be taken to protect all personnel.
Laboratory diagnosis
Bacillus anthracis can be presumptively identified by Gram stain or Giemsa stain of blood smears in affected cattle. In blood smears the organism appears as single to short–chained, Gram–positive, square–ended bacilli. Spore formation also will be present. However, culture is required for a definitive diagnosis. Blood cultures from three of three affected animals were positive in this outbreak. Blood was collected in lavender (EDTA) tubes for transport to the Laboratory. Positive cultures from necropsy tissue specimens were also obtained.
Summary
The case discussed was the first confirmed anthrax outbreak in Nebraska since 1979, according to most reports. Spores are known to survive for extremely long periods of time so veterinarians should include anthrax in differential diagnoses whenever appropriate. Please consult textbooks and other literature for other information about anthrax.