National Agricultural Biosecurity Center

Synopsis of Anthrax

Anthrax is a potentially fatal zoonotic disease that primarily affects livestock and other herbivores (e.g., cattle, sheep, goats, pigs, deer, and water buffalo). According to the Centers for Disease Control and Prevention (CDC), anthrax, along with botulinum toxin, hemorrhagic fever viruses, smallpox, and tularemia, pose the greatest hazard to public health, based on their death rates, ease of dissemination and transmission, and potential to inspire public panic. Bacillus anthracis, the causative agent for anthrax, is an encapsulated, gram-positive, nonmotile, aerobic, spore-forming bacterial rod which can be found worldwide. The spores are extremely stable and usually found in the soil; livestock and other herbivores usually contract anthrax from consuming contaminated soil. Prevalence of spores seems to vary with soil type, land use, and climate. For example, environmental persistence appears to be related to a number of factors, such as soil nitrogen and organic content, alkaline soil (a pH higher than 6.0), ambient temperature higher than 15°C, and dramatic changes in climate (e.g., drought causes livestock to forage much closer to the ground and heavy rains increases the concentration of spores caught in standing water). Anthrax is endemic in Asia, the Middle East, Africa, Central and South America, parts of Europe, and Mexico. Transmission can occur via several routes, such as ingestion, inhalation, and cutaneous; and, clinical signs are different depending on the route of infection and the species affected.

• Depending on the route of transmission and the species affected, anthrax, is characterized by fever, disorientation, depression, anorexia, weakness, muscle tremors, septicemia, dyspnea, colic, edematous swellings, congested mucous membranes, terminal convulsions, collapse, and death. Post mortem lesions include a rapidly decomposing, bloated carcass with incomplete rigor mortis, poorly clotted dark blood coming from the anus, vulva, nostrils, and mouth, multiple petechial hemorrhages, and an enlarged spleen with a 'blackberry jam' consistency.
• Mortality is very high in livestock and other herbivores but relatively low in carnivores.
• In humans, the cutaneous form is most prevalent due to exposure to infected animals or animal products through open wounds in the skin.

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Clinical Signs and Symptoms

Cattle and Sheep:

• Peracute course of illness that lasts approximately 1-2 hours. The first indication of disease may be sudden death of the animal.
• Signs and symptoms:
  • Fever
  • Anorexia
  • Diarrhea
  • Severe depression and listlessness
  • Local edema of the tongue with accumulation of edematous fluid in the throat, sternum, perineum, or flanks
  • Muscle tremors
  • Respiratory distress
  • Abortion
  • Decline in milk production
  • Convulsions
  • Death
• Post mortem lesions:
  • Bloody discharge from natural openings (e.g., nose, mouth, anus, etc.)
  • Rapid bloating
  • Lack of rigor mortis
  • Failure of blood to clot
• Click here for more information on livestock-related information on anthrax published in California Cattlemen, 2000.¹⁸

Horses and Related Animals:

• Acute course of illness that lasts approximately 96 hours.
• Signs and symptoms:
  • Fever
  • Colic
  • Enteritis
  • Septicemia
  • Localized, hot, painful, edematous and subcutaneous swellings
• Post mortem lesions:
  • Bloody discharge from natural openings (e.g., nose, mouth, anus, etc.)
  • Rapid bloating
  • Lack of rigor mortis
  • Failure of blood to clot

Swine, Dogs, and Cats:

• Sub-acute or chronic illness is most common
• Signs and symptoms:
  • Swellings of the neck and regional lymph nodes
  • Dysphagia
  • Dyspneas
  • Severe enteritis
• Post mortem lesions:
  • Bloody discharge from natural openings (e.g., nose, mouth, anus, etc.)
  • Rapid bloating
  • Lack of rigor mortis
  • Failure of blood to clot

Humans:

• Illness can be acute, peracute, or subacute depending on the route of infection (cutaneous, gastrointestinal, or pulmonary); however, if left untreated, death will result.
• Signs and symptoms:
  • Cutaneous: pruritic papules that enlarge and erode to eventually form a 'black eschar', regional lymph tenderness, and toxic septicemia
  • Gastrointestinal: pharyngeal lesions with sore throat, dypshagia, marked neck swelling, regional lymphadenopathy, fever, severe abdominal pain, massive ascites, hematemesis, blood diarrhea
  • Pulmonary: fever, chills, nonproductive cough, chest pain, headache, myalgias, malaise, hemorrhagic mediastinal lymphadenitis, hemorrhagic pleural effusions, severe dyspnea, hypoxia, and septic shock
• Click here for more human-related information on anthrax posted on the UAB Website for Bioterrorism and Emerging Infectious Education.⁴

• Click here for additional information provided on the Minnesota Board of Animal Health website, 2006.

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Diagnosis and Treatment

Diagnostic Samples:

• Samples for diagnostic purposes for animals include post mortem blood samples from peripheral veins (e.g., jugular vein, veins in the ears, etc.)
• If anthrax is suspected, a necropsy should NOT be performed (performance of a necropsy could result in environmental contamination with bacterial spores). Therefore, extreme care should be taken when collecting and handling samples due to the possibility of environmental contamination. For more information related to detection and response, click here (New Mexico State University's Cooperative Extension Service).¹⁹
• Samples for diagnostic purposes for humans include blood (essential), pleural fluid, cerebral spinal fluid, skin lesions, and ascetic fluid.

Differential Diagnosis:

• In animals, the differential diagnoses include blackleg, botulism, toxicosis, lightning strike, and peracute babesiosis.
• In humans, the differential diagnoses include other viral, bacterial, or fungal infections, chest-wall edema, hemorrhagic pleural effusions, and hemorrhagic meningitis.

Clinical Diagnosis:

• In herbivores, anthrax should be considered when sudden death occurs in livestock and unclotted blood from the nose, mouth, anus, or vulva is present. Localized edema of the neck area is suggestive of anthrax in swine and carnivores.
• In humans, consider a presumptive diagnosis based on signs and symptoms alone in the setting of a known or suspected outbreak.

Laboratory Tests:

• In animals, blood smears using McFadyean's polychrome methylene blue stain, culture of bacilli, are commonly used. Also, susceptibility to specific bacteriophages, sensitivity to penicillin, and animal inoculations of mice/guinea pigs to satisfy Koch's postulates are used.
• In humans, aerobic blood culture and gram stain

Treatment

• In animals:
  • Antibiotics are useful if given prior to the onset or immediately after the onset of illness
  • Vaccination to help prevent the spread
• In humans:
  • Supportive care
  • Antibiotics are useful if given prior to the onset or immediately after the onset of illness
    • Ciprofloxacin (400 mg IV q 12 hours) or doxycycline (100 mg IV q 12 hours) plus one or two other antibiotics (e.g., penicillin, rifampin, clindamycin, vancomycin, etc.)

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Economic Consequences and Disease Eradication

Economic Consequences:

• Loss of livestock
• Costs associated with eradication efforts
• International trade embargoes
• Increased costs to consumers

Disease Eradication:

• Immediate notification of state and federal health officials
• Good agricultural and industrial hygiene
• Click here to access biosecurity guidelines¹⁰
• Control measures in livestock in endemic areas:
  • Safe disposal of carcasses (incineration in a manner that ensures heat sterilization of the underlying soil)
  • Vaccination of all at-risk herds
• The carcass should NOT be opened because of potential exposure of the vegetative anthrax bacterium in body fluids to oxygen, which induces spore formation that can contaminate the environment and present a health risk to personnel and other nearby animals. For more information related to detection and response, click here (New Mexico State University's Cooperative Extension Service).¹⁹
• Inactivation: 100°C/10 minutes; calcium hypochlorite; sodium hypochlorite; hydrogen peroxide; formaldehyde; glutaraldehyde; ethylene oxide; chlorine dioxide; methylene bromide; UV radiation; and gamma irradiation.

Anthrax and Bioterrorism:

• The Working Group on Civilian Biodefense considers B anthracis to be one of the most serious biological agents for use as a weapon.¹⁶
• Several countries are believed to have offensive biological weapons programs which include B anthracis, such as the following:
  • The former Soviet Union
  • The United States
  • Iraq
  • Japan
  • South Africa
• Bioweapon potential:
  • B anthracis spores are extremely environmentally hardy and can survive for decades in ambient conditions. The spores are also odorless, colorless, and very small and would, therefore, be difficult to detect if aerosolized. However, an extremely large quantity would have to be manufactured in order to an effective weapon of mass destruction.
  • Once inside blood or tissues of animals or humans, B anthracis are able to rapidly multiply and flourish until local nutrients are exhausted.
  • Aerosol release of weaponized spores, which would primarily result in the inhalation form of anthrax, is the most likely mechanism for use as a biological weapon.
  • Inhalation anthrax would be expected to account for most serious morbidity and most mortality following the use of B anthracis as an aerosolized biological weapon.
  • Given the absence of naturally occurring cases of inhalation anthrax (last naturally occurring case occurred in 1976), early diagnosis, which is critical to survival, would be difficult and requires a high index of suspicion.
• Examples of weaponized anthrax:
  • The Sverdlovsk Outbreak in 1979 resulted from the accidental release of anthrax spores from a military microbiologic facility in the former Union of the Soviet Socialist Republics where it was being mass-produced as a weapon. Seventy-seven human cases (75 inhalation and 2 cutaneous) were reported, 66 of which died (case-fatality rate of 86%).
  • The United States Outbreak in 2001 predominantly involved direct exposure to mail that was deliberately contaminated with anthrax spores. Twenty-two cases (11 inhalation and 11 cutaneous) were identified. Of these cases, five patients with inhalation anthrax died (case-fatality rate of 45%).
• For more information on anthrax and bioterrorism, click on one of the following links:
  • Anthrax as a biological weapon, 2002, published in JAMA (2002).¹⁶
  • Bioterrorism-related inhalation anthrax: The first 10 cases reported in the United States, published in Emerging Infectious Diseases (2001).¹⁷

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Outbreaks

Animal outbreaks

• 2006: MN-6 animals. Click here to access further details on these outbreaks at the Minnesota Board of Animal Health website.
• 2005: Approximately 400 animals in North and South Dakota, Texas, and Minnesota. Click here to access further details on these outbreaks at the CIDRAP Website.¹³
• 2001: CA-21 (livestock) died at cattle ranch (spores in dirt); TX-1638 animals from 63 properties in 5 counties. Click here for more information on the CA outbreak located at the CA Farm Bureau Federation Website.¹¹
• 2000: ND-numerous animals; NV-30 head of cattle died; other animals vaccinated; MN-numerous steer; 2 human cases (gastrointestinal anthrax); ND-80 cattle/horses died; SD-9 cattle died; NV-32 cattle died; MN-11 cows. Click here for more information on the 2000 outbreaks located at the Federation of American Scientists Website.²⁰
• 1993: ND-8 animals; soil contamination
• 1984: CA-43 head of cattle and 135 head of sheep died
• 1979: IA-16 animals
• 1976: TX-more than160 animals; flies
• 1974: TX-more than 230 animals; positive sample from city water tap; WA-private game farm; 42 animals (cougars/other large felines) infected horsemeat
• 1971: PA-33 animals; hay and soil samples positive; LA-588 animals
• 1970: WY-8 animals
• 1968: CA-176 animals; CT-3 animals
• 1965: ND-19 animals
• 1962: MS0-multiple animals; involved many counties
• 1959: TX-125 animals; NJ-2 cows and many hogs; contaminated feed
• 1958: LA-15-20 animals; involved cows, sheep, and horses
• 1957: OK-400-500 animals
• 1956: WY-multiple animals; MS-more than 250 animals
• 1955: LA-1,404 animals
• 1952: OH-multiple animals in 5 counties ; contaminated feed/bone meal

Human cases

• 2001: 22 cases; 4 deaths (inhalation anthrax) intentional contamination; TX-1 case of cutaneous anthrax (infected animal exposure). Click here for more information on this outbreak published in the MMWR, 2001.⁸
• 2000: MN-2 suspected cases of gastrointestinal anthrax (infected animal exposure); ND-1 case of cutaneous anthrax (infected animal exposure)
• 1987: NC-1 case of cutaneous anthrax at textile mill (goat hair)
• 1978: NH-2 cases of cutaneous anthrax at textile mill (goat hair); NC-2 cases of cutaneous anthrax at textile mill (goat hair)
• 1976: CA-1 fatal case of inhalation anthrax (goat hair from Pakistan)
• 1974: SC-1 case of cutaneous anthrax at textile mill (goat hair); FL-1 case of cutaneous anthrax (goat-skin drums from Haiti)
• 1971: LA2 cases of cutaneous anthrax (necropsy)
• 1968: CA-1 case of cutaneous anthrax (infected animal carcass)
• 1966: NH-1 case of cutaneous anthrax (goat hair) and 1 case of inhalation anthrax (dust from neighboring goat hair mill)
• 1965: NJ-3 cases of cutaneous anthrax at gelatin plant (dry cow bones)
• 1964: OH-1 fatal case of cutaneous anthrax (goat hair)
• 1961: PA-1 fatal case of inhalation anthrax at textile mill (goat hair)
• 1960: SC-4 cases of cutaneous anthrax at textile mill (goat hair)
• 1959: TX-5 cases of cutaneous anthrax (necropsy (3), infected animal (2)); NJ-1 case of cutaneous anthrax (goat hair)
• 1957: OK-1 case of cutaneous anthrax (necropsy on infected cow); NH-4 cases of cutaneous anthrax & 5 cases of inhalation anthrax (4 fatal) at textile mill; PA-1 fatal case at factory (glue made from animal hides)
• 1956: NC-5 cases of cutaneous anthrax at textile mill (goat hair)
• 1955: LA-4 cases of cutaneous anthrax (infected animal exposure)
• 1953: NC-1 case of cutaneous anthrax at textile mill (goat hair)

• Click on the following hyperlink for the most recent outbreak information located at the Office International des Epizooties Website. http://www.oie.int/eng/info/hebdo/A_DSUM.htm.²¹

Threats:

• 1998: CA, IN, KY, TN; Evaluation of multiple telephone treats and letters alleged to contain anthrax; report included recommendations for response to bioterrorism threats Disease Eradication. Click here for more information on these threats published by the Anti-Defamation League, 2001.⁶

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Sources and Related Articles

Sources:

1. WHO. October 2001. Fact sheet: Anthrax. Fact sheet N°264 Available at http://www.who.int/mediacentre/factsheets/fs264/en/print.html.
2. CDC. March 21, 2005. Anthrax. Available at http://www.bt.cdc.gov/agent/anthrax/index.asp.
3. USDA, APHIS. November 2001. Anthrax: Clinical Signs and Diagnosis. Available at http://www.aphis.usda.gov/lpa/pubs/fsheet_faq_notice/fs_ahanthrax.html.
4. UAB: Bioterrorism and Emerging Infections Education. Anthrax Summary. Available at http://bioterrorism.uab.edu/CategoryA/Anthrax/summary.asp.←
5. CIDRAP. Anthrax: Current, comprehensive information on pathogenesis, microbiology, epidemiology, diagnosis, treatment, and prophylaxis. Available at http://www.cidrap.umn.edu/cidrap/content/bt/anthrax/index.html.

Related Articles:

6. Anonymous, 2001. Beyond Anthrax: Extremism and the Bioterrorism Threat. Published by the Anti-Defamation League. Available at http://www.adl.org/learn/Anthrax/beyond_anthrax.pdf.←
7. Anonymous. August 17, 2001. Human Anthrax Associated with an Epizootic Among Livestock - North Dakota, 2000. MMWR. 50(32). Available at http://www.cdc.gov/mmwr/PDF/wk/mm5032.pdf.
8. Anonymous. October 19, 2001. Update: Investigation of Anthrax Associated with Intentional Exposure and Interim Public Health Guidelines, October 2001. Morbidity and MMWR. 50(41). Available at http://www.cdc.gov/mmwr/PDF/wk/mm5041.pdf.←
9. Anonymous. November 2, 2001. Update: Investigation of Bioterrorism-Related Anthrax. MMWR. 50(43):941-948. Available at http://www.cdc.gov/mmwr/PDF/wk/mm5043.pdf.
10. Anonymous. February 2005. Biosecurity Guideline for the Farmer or Producer. Available at http://www.agrosecurity.uga.edu/annexes/Annex03_Procedures.pdf.←
11. Eric Brazil, October 31, 2001. 15 Exposed to Dead Cows Treated for Anthrax. Published at SFGate.com. Available at http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2001/10/31/MN66939.DTL&type=printable.←
12. Bales ME, Dannenberg AL, Brachman PS, Kaufman AF, Klatsky PC, and Ashford DA. 2001. Epidemiologic Response to Anthrax Outbreaks: Field Investigations, 1950-2001. Emerging Infectious Diseases. 8(10):1163-1174. Available at http://www.cdc.gov/ncidod/EID/vol8no10/pdf/02-0223.pdf.
13. Hatfield L. August 4, 2005. Bad Year for Anthrax Outbreaks in US Livestock. CIDRAP News. Available at http://www.cidrap.umn.edu/cidrap/content/bt/anthrax/news/....←
14. Hugh-Jones ME and de Vos V. 2002. Anthrax and wildlife. Office International des Epizooties. Rev Sci Tech. 21(2):359-383. Available at http://www.oie.int/eng/publicat/rt/2102/HUGH-JONES.pdf.
15. Inglesby TV, Henderson DA, Bartlett JG, Ascher MS, Eitzen E, et. al., 1999. Anthrax as a Biological Weapon: Medical and Public Health Management. JAMA. 281:1735-1745. http://jama.ama-assn.org/cgi/reprint/281/18/1735.
16. Inglesby, TV, O'Toole T, Henderson DA, Bartlett JG, Ascher MS, et. al., 2002. Anthrax as a Biological Weapon, 2002: Updated Recommendations for Management. JAMA. 287(17):2236-2252. Available at http://jama.ama-assn.org/cgi/reprint/287/17/2236.←
17. Jernigan JA, Stephens DS, Ashford DA, Omenaca C, Topiel MS, et. al., 2001. Bioterrorism-Related Inhalation Anthrax: The First 10 Cases Reported in the United States. Emerg Infect Dis. 7(6):933-944. Available at http://www.cdc.gov/ncidod/EID/vol7no6/pdf/jernigan.pdf.←
18. Kirk J and Hamlen H. October 2000. Anthrax: What Livestock Producers Should Know. Published in California Cattlemen. Available at http://www.cdfa.ca.gov/ahfss/ah/pdfs/Anthrax_hh_article.pdf.←
19. Parker R, Mathis C, Looper M, and Sawyer J. April 2002. Anthrax and Livestock: Guide B-120. New Mexico State University. Cooperative Extension Service. College of Agriculture and Home Economics. Available at http://www.cahe.nmsu.edu/pubs/_b/B-120.pdf.←
20. Preslar D. August 2001. Outbreak - Anthrax. Federation of American Scientist. AheadIliad. Available at http://fas.org/ahead/news/000825.htm.←
21. Click on the following hyperlink for the most recent outbreak information located at the Office International des Epizooties Website. http://www.oie.int/eng/info/hebdo/A_DSUM.htm.←

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