Anthrax

Anthrax is an acute zoonotic infection of bacillus anthracis bacteria usually infecting grazing animals. The disease is caused by the exotoxins released once the spores germinate into mature bacilli inside the infected host’s macrophages. In Pakistan, the disease is locally termed sut or golle. Anthrax is among the top priority diseases of Pakistan according to the national epidemiological survey of important diseases of livestock.

Disease Status and Recent Outbreaks

Anthrax is endemic to hilly and desert areas of Pakistan. The last outbreak of anthrax was reported in 2017 when government sent vets to Kurram agency after the death of 43 cattle.  According to a 2015 study, 37% of soil from the Lahore district tested positive for anthrax spores. Soil samples from district Badin had an overall prevalence of 20% and 33.75% in soil, wool and hairs in district Tharparkar.  In eight out of nine districts of Punjab, all four species of domestic animals (cattle, buffalo, goat, and sheep) were tested positive for antibodies against the protective antigen of B. anthracis, with the highest seroprevalence found in Lahore (82.4%), and followed by Gujranwala (80.4%), Sahiwal (72.7%), Chakwal (63.6%), Sargodha (54.3%), Faisalabad (15.2%), Sheikhupura (14.1%), DG Khan (5.5%), and Attock (0%). A Cholistan study found anthrax to be the most serious bacterial infection in camels, with an overall prevalence rate of 1.80%. Pakistan has also experienced bioterrorism when anthrax spores were mailed to Pakistani Prime Minister, Yousaf Raza Gilani in 2012.

Zoonotic Potential

Anthrax can affect several mammalian species including humans. Humans can contact anthrax spores or blood discharges from infected animals, animal products, soils, contaminated water, and fodder. Anthrax spores can remain viable for up to 70 years and can survive extreme changes in temperature, pH, and other adverse conditions. Pakistan confirmed its first clinically confirmed human anthrax case in 2001.

Causative Agent

Bacillus anthracis is a gram-positive, aerobic, and non-motile bacteria that occurs in either vegetative or spore form. The spores can remain dormant for years until inhaled or ingested by the host. Inside the host, they germinate into vegetative cells releasing toxins like lethal factors, edema factors, and protective antigens. These toxins along with their vegetative cells hijack the immune system and dysregulate the signal transduction pathways of cells ultimately leading to cell death and edema. The vegetative cells also spread in the body and cause septicemia. The oxygen content of air induces sporulation of vegetative bacilli after they are released from an infected animal. The bloody discharges from natural openings of the infected animals are major contributing factors in the spread of anthrax.

Types of Anthrax

There are 4 forms of anthrax depending upon the mode of entry of bacteria/spores inside the host

It is the most common but least dangerous form of anthrax as most infected people with proper treatment survive. It happens when bacteria enter the host through a wound on the skin. This is usually common in veterinarians and people who handle infected animals or their products. The incubation period is 1-7 days after the infection. Common signs and symptoms include:

  • – Black centered painless sore
  • – Swelling in lymph glands
  • – Flu-like symptoms

Inhalation anthrax is the most fatal form of anthrax with an incubation time of 1 week. The survival rate of patients after aggressive treatment is about 55%. As the name suggests, the person who breathes in the anthrax spores can develop this form of anthrax. Because of it, anthrax is also termed wool sorter’s disease as this form is common among workers dealing with infected animals’ wool. Signs and symptoms are as follows:

  • – Flu-like symptoms
  • – Shortness of breath
  • – Trouble breathing
  • – Chest discomfort
  • – Nausea
  • – Painful swallowing
  • – Coughs with blood
  • – Shock
  • – Meningitis

This form of anthrax usually develops in people who eat raw or undercooked meat. Vegetative form of anthrax bacteria can be killed by cooking, but bacterial spores are highly resistant to heat and common disinfection methods. Therefore, it is necessary to identify infected animals before slaughter. Infection normally develops about 1 week after exposure. With proper treatment, 60% of patients can survive. Signs and symptoms of gastrointestinal anthrax are:

  • – Vomiting
  • – Headache
  • – Nausea
  • – Abdominal pain
  • – Fever
  • – Loss of appetite
  • – Swollen neck
  • – Difficulty swallowing
  • – Bloody diarrhea

This form of anthrax was first identified in heroin drug users of northern Europe. This form of anthrax can occur by subcutaneous injections contaminated with anthrax spores. This is similar to the cutaneous form except that infection can spread throughout the body in a shorter duration and is difficult to treat.  Signs and symptoms are:

  • – Severe swelling
  • – Organ failure
  • – Shock
  • – Meningitis

Learn More

References;

Anthrax outbreak. (2017). Retrieved from The Express Tribune: https://tribune.com.pk/anthrax-outbreak

Mari, A. S. (2017). Prevalence of Bacillus anthracis Spores in Soil of District Badin. Journal of Animal Health and Production.

Rashid, H. (2020). SEROPREVALENCE OF BACILLUS ANTHRACIS PROTECTIVE-ANTIGEN IN NINE DISTRICTS OF CENTRAL PUNJAB, PAKISTAN. Journal of Animal and Plant Sciences.

Ashraf, S. (2014). Prevalence of Common Diseases in Camels of Cholistan Desert, Pakistan. Journal of Infection and Molecular Biology.

Masood, S. (2012). Pakistan Says Prime Minister Was Mailed Anthrax Spores. Retrieved from The Newyork Times: https://www.nytimes.com/2012/02/02/world/asia/pakistan-reveals-prime-minister-gilani-was-sent-anthrax.html

FINKE, E.-J. (2020). Review: The risk of contracting anthrax from spore-contaminated soil – A military medical perspective. European Journal of microbiology and immunology .

DAWN. (2001). KARACHI: Pakistan’s first anthrax case. Retrieved from Dawn news: https://www.dawn.com/news/3494/karachi-pakistan-s-first-anthrax-case