Anthrax is an infectious zoonotic disease (could be transferred from animals to humans). It is primarily a disease of herbivorous animals particularly cattles sheep, goats, horses and mules. The disease naturally occurs among herbivorous animals through contaminated soil and feed; among omnivorous and carnivorous animals through contaminated meat, bone meals or other feeds; and among wild animals from feeding on anthrax infected carcasses. Infected animals shed the bacilli in terminal hemorrhage or spilt blood at death. Anthrax spores can persist in soil for many years.
Humans almost invariably contract the natural disease directly or indirectly from animals or animal products.
Anthrax is existed in many parts of the world, including Asia, southern Europe, sub-Sahelian Africa and parts of Australia. Anthrax also called Malignant pustule, Malignant oedema, Woolsorter’s disease, or Ragpicker’s disease
Bio terrorism and Anthrax:
Anthrax is considered an important biological warfare agent because:
(i) it is highly fatal and when transmitted through inhalation is almost always fatal,
(ii) anthrax spores can remain viable for several decades and can be easily produced in large quantities at a very low cost, and
(iii) it is easy to weaponize and disseminate anthrax as an odourless and invisible aerosol which can affect thousands of people at the same time.
Symptoms of Anthrax Infection
Anthrax infection occurs in three forms: cutaneous, inhalation, and gastrointestinal, depending on the mode of transmission. Cutaneous anthrax accounts for most of the cases in endemic situation.
Cutaneous, or skin, anthrax is the most common form. It is usually contracted when a person with a break in their skin, such as a cut or abrasion, comes into direct contact with anthrax spores. The resulting itchy bump rapidly develops into a black sore. Some people can then develop headaches, muscle aches, fever and vomiting. Cutaneous anthrax usually occurs after exposure to infected animals or their contaminated tissues and products such as hair, hides, wool, bones and skin.
Gastrointestinal anthrax is caught from eating meat from an infected animal. It causes initial symptoms similar to food poisoning but these can worsen to produce severe abdominal pain, vomiting of blood and severe diarrhea.
Pulmonary anthrax- The most severe form of human anthrax is called inhalation or pulmonary anthrax. Though the rarest, it is the form of human anthrax causing the most current concern. This form of the disease is caused when a person is directly exposed to a large number of anthrax spores suspended in the air, and breathes them in. The first symptoms are similar to those of a common cold, but this can rapidly progress to severe breathing difficulties and shock.
Anthrax is caused by gram-positive, rod-shaped bacteria known as Bacillus anthracis, an encapulated and spore-forming bacillus.
Humans generally acquire the disease from infected animals or as a result of occupational exposure to contaminated animal products. Infected animals shed the bacilli in terminal hemorrhage or spilt blood at death. On exposure to the air, the vegetative forms sporulate (formation of spores). Contaminated animal products and vultures who feed on anthrax infected carcasses also spread the organism from one area to another.
Incubation period of the disease is from a few hours to seven days. Most cases occur within 48 hours of exposure.
Laboratory confirmation is made by the demonstration of B. anthracis from the blood, skin lesions or respiratory secretions by direct polychrome methylene blue stained smears, although it is rapid and results are available in 2-3 hours, it is not specific.
Laboratory confirmation can be done by Culture or by inoculation of mice, guinea pig or rabbits. Culture and Identification takes 24-48 hours and gives presumptive diagnosis that needs to be confirmed by Polymerase chain reaction (PCR) or animal pathogenicity test.
PCR test recommended on suspected bacterial colonies. PCR can also be attempted from the direct sample. Thus, a total of 36 to 48 hours are required to confirm the diagnosis.
Anthrax responds well to antibiotic treatment. Antibiotics must be prescribed and taken with medical advice. Nobody should attempt to use antibiotics or any other drugs to treat or protect themselves without first getting medical advice.
Up to 20% of the cutaneous cases are fatal if not treated.
Gastrointestinal anthrax can lead to blood poisoning, shock, and death. Intestinal anthrax results in death in 25% to 60% of cases.
Pulmonary anthrax can cause severe breathing problems, shock, and often meningitis (inflammation of the brain and spinal cord covering).Pulmonary or inhalation anthrax is always fatal.
Antibiotics can prevent anthrax from developing in people who have been exposed but have not developed symptoms. People who have been exposed to anthrax must take antibiotics for 60 days.
Vaccination for humans-There is a vaccine against anthrax, but it is not approved for widespread use. The vaccine is sometimes given to people who are likely to be exposed to anthrax through their occupation, for example, tannery workers, military personnel, laboratory workers who work with anthrax, people who handle animals or animal products.
Anthrax vaccine is recommended for people 18 to 65 years of age. These people should get 5 doses of vaccine (in the muscle): the first dose when risk of a potential exposure is identified, and the remaining doses at 4 weeks and 6, 12, and 18 months after the first dose. Annual booster doses are recommended for ongoing protection.
Anthrax vaccine is also recommended for unvaccinated people who have been exposed to anthrax in certain situations. These people should get 3 doses of vaccine (under the skin), with the first dose as soon after exposure as possible, and the 2nd and 3rd doses given 2 and 4 weeks after the first.
Vaccine should not be given to any person with:
- Anyone who has had a serious allergic reaction to a previous dose of anthrax vaccine should not get another dose.
- Anyone who has a severe allergy to any component of the anthrax vaccine should not get a dose. Anyone with severe allergies, including allergy to latex, should tell their doctor.
- Anyone with a moderate or severe illness. People with mild illness can usually be vaccinated.
Pregnant women should not get the vaccine.
- Vaccination for animals-Anthrax vaccine is indicated for all the animals in the suspected herd, the animals on neighbouring premises and all susceptible animals if there is a reason to believe that they continue to be exposed in endemic areas. The protective effect of vaccine is limited to about 1 year and therefore the animals in enzootic areas must be immunized annually. Pregnant animals should not be vaccinated. Vaccination as a control measure must be applied together with other control measures.
- Subject experts must be consulted for actions to be taken and management of individuals exposed to suspicious letters/ packages laced with anthrax (bioweapon).