Glanders is an infectious disease that is caused by the bacterium Burkholderia mallei.
Glanders is primarily a disease affecting horses, but it also affects donkeys and mules and can be naturally contracted by goats, dogs, and cats.
Human infection, although not seen in the United States since 1945, has occurred rarely and sporadically among laboratory workers and those in direct and prolonged contact with infected, domestic animals. For humans, it is life-threatening and painful. Without antibiotic treatment, the case fatality rate can be as high as 95%.
Some animals die acutely within a few weeks. Others become chronically infected, and can spread the disease for years before succumbing.
Why has glanders become a current issue?
Glanders was a worldwide problem in equids for several centuries, but this disease was eradicated from most countries by the mid-1900s. Outbreaks are now uncommon and reported from limited geographic areas. In non-endemic regions, cases may be seen in people who work with the causative organism, Burkholderia mallei, in secure laboratories. Burkholderia mallei is an organism that is associated with infections in laboratory workers because so very few organisms are required to cause disease. An infection was reported in a US researcher in 2000. The organism has been considered as a potential agent for biological warfare and of biological terrorism.
How common is it?
The United States has not seen any naturally occurring cases since the 1940s. However, it is still commonly seen among domestic animals in Africa, Asia, the Middle East, and Central and South America.
How is it transmitted and who can get it?
Glanders is transmitted to humans by direct contact with infected animals. The bacteria enter the body through the skin and through mucosal surfaces of the eyes and nose. The sporadic cases have been documented in veterinarians, horse caretakers, and laboratorians.
B. mallei is readily spread on fomites including harnesses, grooming tools, and food and water troughs. Although this organism is inactivated by heat and sunlight, its survival is prolonged in wet or humid environments.
B. mallei remains viable in room temperature water for up to a month. Some sources suggest that it might be able to survive for more than a year in the environment, under some circumstances. Others state that it may survive for up to a few months in favorable environments, but it is likely to be inactivated within two weeks in unfavorable conditions.
What are the symptoms?
The symptoms of glanders depend upon the route of infection with the organism. The types of infection include localized, pus-forming cutaneous infections, pulmonary infections, bloodstream infections, and chronic suppurative infections of the skin. Generalized symptoms of glanders include fever, muscle aches, chest pain, muscle tightness, and headache. Additional symptoms have included excessive tearing of the eyes, light sensitivity, and diarrhea.
Localized infections: If there is a cut or scratch in the skin, a localized infection with ulceration will develop within 1 to 5 days at the site where the bacteria entered the body. Swollen lymph nodes may also be apparent. Infections involving the mucous membranes in the eyes, nose, and respiratory tract will cause increased mucus production from the affected sites.
Pulmonary infections: In pulmonary infections, pneumonia, pulmonary abscesses, and pleural effusion can occur. Chest X-rays will show localized infection in the lobes of the lungs.
Bloodstream infections: Glanders bloodstream infections are usually fatal within 7 to 10 days.
Chronic infections: The chronic form of glanders involves multiple abscesses within the muscles of the arms and legs or in the spleen or liver.
Where is glanders usually found?
Geographically, the disease is endemic in Africa, Asia, the Middle East, and Central and South America.
How is glanders diagnosed?
The disease is diagnosed in the laboratory by isolating Burkholderia mallei from blood, sputum, urine, or skin lesions. Serologic assays are not available.
The incubation period varies from a few days to many months; two to six weeks is typical. Experimental infections can result in clinical signs after three days.
Can glanders spread from person to person?
In addition to animal exposure, cases of human-to-human transmission have been reported. These cases included two suggested cases of sexual transmission and several cases in family members who cared for the patients.
Is there a way to prevent infection?
There is no vaccine available for glanders. In countries where glanders is endemic in animals, prevention of the disease in humans involves identification and elimination of the infection in the animal population. Within the health care setting, transmission can be prevented by using common blood and body fluid precautions.
Animals that test positive for glanders are euthanized except in endemic areas. In an outbreak, the premises should be quarantined, thoroughly cleaned and disinfected. All contaminated bedding and food should be burned or buried, and equipment and other fomites should be disinfected. Carcasses should be burned or buried.
Whenever possible, susceptible animals should be kept away from contaminated premises for several months. In endemic areas, susceptible animals should be kept away from communal feeding and watering areas, since glanders is more common where animals congregate. Routine testing and euthanasia of positive animals can eradicate the disease. Vaccines are not available.
Is there a treatment for glanders?
In animals, some antibiotics may be effective against glanders, but treatment is given only in endemic areas. Treatment is risky even in these regions, as infections can spread to humans and other animals, and treated animals can become asymptomatic carriers.
Because human cases of glanders are rare, there is limited information about antibiotic treatment of the organism in humans. Sulfadiazine has been found to be an effective in experimental animals and in humans. Burkholderia mallei is usually sensitive to tetracyclines, ciprofloxacin, streptomycin, novobiocin, gentamicin, imipenem, ceftrazidime, and the sulfonamides. Resistance to chloramphenicol has been reported.
Sources: National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)
The Center for Food Security and Public Health, Iowa State University