Understanding Anthrax: Expert Insights on Transmission, Treatment, and Prevention of a Persistent Zoonotic Threat
Key Insights
Anthrax (search), caused by Bacillus anthracis (search), remains a dangerous zoonotic disease with spores capable of surviving in the environment for decades, posing ongoing risks in endemic regions including Thailand.
Inhalational anthrax (search) carries a mortality rate as high as 95% if a large number of spores are inhaled, making it the most alarming form of infection.
Effective antibiotic treatments exist, including penicillin (search), doxycycline, and ciprofloxacin, with treatment duration ranging from 7 days for cutaneous anthrax (search) to 60 days for inhalational cases.
Thailand has reported sporadic anthrax (search) cases over the years, with the most recent outbreak occurring during April–May 2025 in Don Tan District, Mukdahan Province, resulting in one fatality. Since 1991, a total of 19 deaths among Thai people have been attributed to anthrax infection, underscoring the persistent threat posed by this zoonotic disease despite its relatively infrequent occurrence.
Asst. Prof. Dr. Taradon Luangthongkum from the Faculty of Veterinary Science, Chulalongkorn University, has provided expert guidance on the risks, clinical manifestations, treatment approaches, and prevention strategies for anthrax (search), emphasizing that preparedness and accurate knowledge remain the best forms of protection.
The Pathogen and Its Resilience
Anthrax (search) is caused by Bacillus anthracis (search), a Gram-positive bacterium with a critical survival advantage: the ability to form spores. These spores can persist in suitable environments for decades, contaminating soil, animal hair, hides, and meat. "Thailand has reported sporadic cases of anthrax from time to time, such as in Don Tan District, Mukdahan Province, last year. In addition, outbreaks have previously been reported in other provinces, including Tak, Kanchanaburi, Phitsanulok, Chiang Mai, and Phichit. However, these outbreaks have not been continuous," explained Asst. Prof. Dr. Taradon.
The disease most commonly affects herbivorous and ruminant animals, including cattle, buffaloes, goats, and sheep. In cattle and buffaloes, infected animals often die suddenly, with dark-colored blood oozing from natural body openings such as the nose, mouth, eyes, and anus. The carcass typically does not undergo normal rigor mortis and may become bloated and decompose rapidly. Other animal species, including pigs, horses, dogs, and cats, can also become infected, though dogs and cats demonstrate notable resistance. In most cases, pets acquire the infection by consuming raw meat from animals that have died of anthrax (search).
Three Routes of Human Transmission
Anthrax (search) can infect humans through three distinct routes, each with varying degrees of severity:
Cutaneous anthrax (search), acquired through skin contact, is most commonly seen in individuals involved in animal slaughter or those with abrasions or wounds who handle infected meat or carcasses. The characteristic lesion is an eschar—a swollen area with a darkened center resembling dead tissue, similar to a cigarette burn.
Gastrointestinal anthrax (search) results from consuming raw or undercooked meat from infected animals. Initial symptoms include abdominal pain, nausea, vomiting, fever, loss of appetite, and in some cases, bloody diarrhea.
Inhalational anthrax (search) occurs when microscopic spores are breathed in, most commonly affecting workers in textile manufacturing facilities handling animal wool or hides from outbreak areas. "The severity of anthrax generally depends on the route through which the infection enters the body. However, inhalational is the most alarming form because it can cause severe pneumonia if a large number of spores are inhaled. In such cases, the mortality rate can be as high as 95%," Asst. Prof. Dr. Taradon stated.
At-Risk Populations
Several occupational and behavioral groups face elevated risk: farmers and livestock raisers in close contact with infected animals; workers involved in animal slaughter and meat processing, particularly those handling carcasses of animals that died suddenly; workers in the wool, hide, and leather industries in areas with previous outbreaks; and individuals who consume raw meat dishes such as larb, koi, or other foods containing raw animal blood.
Treatment: Antibiotics Remain Effective
Asst. Prof. Dr. Taradon affirmed that anthrax (search) remains treatable with antibiotics, and Bacillus anthracis (search) continues to be susceptible to commonly used medications. For human patients, effective options include penicillin (search), doxycycline, and fluoroquinolone-class antibiotics such as ciprofloxacin.
Treatment duration varies significantly by infection route. Cutaneous anthrax (search) typically requires approximately seven days of treatment. In contrast, inhalational anthrax often necessitates treatment for up to 60 days, as spores that remain in the lungs may germinate and develop into active bacteria during that extended period.
For animals, the same antibiotic classes are used, but prevention takes priority. An anthrax (search) vaccination program is recommended for livestock in high-risk areas, administered after weaning with booster vaccinations every six months for five consecutive years.
Prevention and Control Strategies
Effective anthrax (search) management demands cooperation from both farmers and consumers. When an animal dies suddenly—especially with dark-colored blood oozing from natural body openings—anthrax should be suspected. Critically, carcasses must never be moved, butchered, or cut open, as exposure to air triggers spore formation, leading to environmental contamination that can persist for extended periods.
Proper carcass disposal involves either burial at approximately two meters depth with quicklime spread over the carcass, or incineration in a properly enclosed system. Contaminated areas should be treated with disinfecting chemicals such as formalin or highly concentrated sodium hydroxide.
For the public, key preventive measures include avoiding direct contact with animal carcasses without protective gloves, thorough handwashing after any contact, and avoiding consumption of raw meat—particularly from animals that died under unusual circumstances. Meat should be cooked to at least 75°C (167°F); while this may not destroy spores, it kills vegetative bacteria and reduces infection risk. Workers in textile factories processing animal wool, hair, or hides should wear protective clothing and face masks, and facilities should ensure adequate ventilation and proper disinfection of materials originating from outbreak areas.
Although anthrax (search) is not encountered in everyday life, it remains a serious zoonotic disease, particularly when infection occurs through the respiratory tract. Any unusual or unexplained animal deaths should be reported to livestock authorities immediately, and vigilance for signs and symptoms, avoidance of high-risk behaviors, and proper hygiene practices remain essential protective measures.