Glanders and melioidosis (also called pseudoglanders) are related infectious diseases caused by bacterial species in the Burkholderia genus. Both diseases produce similar symptoms and are diagnosed, treated, and prevented similarly. However, glanders and melioidosis differ with respect to where they originate and how they spread.
Glanders primarily infects horses, but can also infect donkeys, mules, cats, dogs, sheep, and goats. Such infected animals pass the infection on to humans either directly or indirectly. Melioidosis is found in contaminated water and soil. It spreads to humans and animals (the same ones as with glanders) by contact with such contaminated sources.
Glanders is caused by the bacterium Burkholderia mallei. The bacterium is found only in infected host animals and is not found in plants, soil, or water. Melioidosis is caused by the bacterium Burkholderia pseudomallei. Most animals that contract melioidosis do so by ingestion of contaminated food, soil, or water. Humans become infected with both glanders and melioidosis through openings in the skin, mucosal surfaces, and by inhalation.
Glanders is transmitted by direct contact with infected animals, and the bacteria enter the human body through breaks in the skin or through the mucosal surfaces of the eyes and nose. Melioidosis is transmitted by direct contact with contaminated soil and surface waters, and the bacteria are thought in enter the body through breaks in the skin, inhalation of contaminated soil, and ingestion of contaminated water. Person-to-person transmission of both glanders and melioidosis also have been documented. Symptoms depend on the amount of bacteria in the human system. A few bacteria inside the body rarely cause any symptoms, however, more symptoms appear when more organisms are present.
In glanders infection, symptoms appear in about one to five days, while melioidosis symptoms may not develop for years. When symptoms occur, their characteristics depend on the mode of transmission (skin or mucosal surfaces) into the body and the form of the infection (acute or chronic).
An acute localized infection with glanders results in swollen lymph glands, fever, sweats, muscle pains, and coughing. Other symptoms include eye tearing, light sensitivity, and diarrhea. Entrance into the body through the eyes, nose, and respiratory tract causes excessive and sometimes infectious mucus. The infection may also enter the bloodstream. This more serious bacterial infection in the bloodstream is called septicemia. Septicemia caused by B. mallei will usually cause death within seven to ten days.
An acute localized infection with melioidosis causes respiratory problems, headache, diarrhea, fever, pusfilled skin lesions, muscle soreness, and confusion. Usually the infection is resolved in a short period of time. However, people with unrelated serious illnesses such as renal failure, diabetes, and HIV (human immunodeficiency virus) infection can go into septic shock, resulting in multiple organ collapse and death.
Acute pulmonary infections in both glanders and melioidosis can cause symptoms ranging from mild bronchitis to severe pneumonia. Symptoms include fever, headache, anorexia, pulmonary abscesses, and muscle soreness.
Chronic infections of both diseases cause multiple abscesses within the arm and leg muscles or in the spleen or liver. For glanders, nasal and subcutaneous nodules (small lumps) form, followed with ulceration. Death can follow within a few months. Symptoms of chronic melioidosis are often similar to tuberculosis. Lung or spleen abscesses often cause abdominal pain and fever, while brain abscesses often cause neurological problems. Melioidosis infection also may travel into the bones, brain, lungs, and joints. It usually causes death when it infects the bloodstream, but is non-fatal in other areas. However, the severity of the infection and the timeliness of treatment is critical in the prognosis.
WORDS TO KNOW
ABSCESS: An abscess is a pus-filled sore, usually caused by a bacterial infection. It results from the body's defensive reaction to foreign material. Abscesses are often found in the soft tissue under the skin, such as the armpit or the groin. However, they may develop in any organ, and they are commonly found in the breast and gums. Abscesses are far more serious and call for more specific treatment if they are located in deep organs such as the lung, liver, or brain.
ACUTE: An acute infection is one of rapid onset and of short duration, which either resolves or becomes chronic.
MORTALITY: Mortality is the condition of being susceptible to death. The term “mortality” comes from the Latin word mors, which means “death.” Mortality can also refer to the rate of deaths caused by an illness or injury, i.e., “Rabies has a high mortality.”
NODULE: A nodule is a small, roundish lump on the surface of the skin or of an internal organ.
Both diseases are rare in the United States. According to the Division of Bacterial and Mycotic Diseases (DBMD), of the U.S. Centers for Disease Control and Prevention (CDC), glanders has not appeared in the United States since 1945, and there are between zero to five cases of melioidosis annually, most often in travelers and immigrants.
Glanders is frequently found in Africa, Asia, Central and South America, and the Middle East. The disease has been controlled in North America, Australia, and most of Europe. Melioidosis is commonly found in parts of Southeast Asia (especially Thailand, Singapore, Malaysia, Myanmar, and Vietnam) and northern Australia. It is also occasionally found in Brunei, China, Hong Kong, India, Laos, Taiwan, and several countries in Africa, Central and South America, the Middle East, and the South Pacific.
Diagnosis of glanders and melioidosis is made with cultures of blood, sputum, or urine. A pus culture from an abscess also is used with melioidosis. Detecting and measuring the number of bacterial antibodies is another means to diagnosis.
Treatment for acute glanders is limited. According to the DBMD, the antibiotic sulfadiazine has been found to be effective. Other antibiotics used include amoxicillin-clavulanic, azlocillin, aztreonam, ceftazidime, ceftriaxone, doxycycline, imipenem, penicillin, and ticarcillin-vulanic acid. Statistics for glanders are difficult to obtain, but medical professionals contend that a large percentage of people infected still die when antibiotics are not given. The best way to prevent glanders is to eliminate the infection in animals.
Treatment of acute melioidosis includes intravenous cephalosporin antibiotics, often ceftazidime. According to the CDC, other antibiotics used include amoxicillin clavulanate, meropenem, and imipenem. Antibiotics are given for 10–14 days. After the initial course of anti-biotics is completed, the antibiotic pair co-trimoxazole and doxycycline is prescribed for 12–20 weeks to prevent another occurrence.
IN CONTEXT: TERRORISM AND BIOLOGICAL WARFARE
The Division of Bacterial and Mycotic Diseases at Centers for Disease Control and Prevention (CDC) states that with regard to Burkholderia mallei “very few organisms are required to cause disease.” For this reason, Burkholderia mallei “has been considered as a potential agent for biological warfare and of biological terrorism.”
CDC classifies glanders and melioidosis in the Category B Diseases/Agents, a classification reserved for “second highest priority agents, which include those that:
- are moderately easy to disseminate;
- result in moderate morbidity rates and low mortality rates; and
- require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance.”
SOURCE: Centers for Disease Control and Prevention (CDC), Coordinating Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases.”
Before the use of antibiotics, acute melioidosis had a death rate of about 90%. Today, antibiotics have reduced the percentage to about 10% for simple cases that are early treated. However, untreated and severe cases still have a mortality rate of about 80%. Repeat occurrences of melioidosis happen about 10–20% of the time. In countries where melioidosis is prevalent, contact with soil, mud, flood waters, and surface waters should be avoided to prevent infection.
Medical researchers are still trying to develop a vaccine for both glanders and melioidosis.
According to the DBMD, both glanders and melioidosis are considered potential biological weapons in warfare and terrorism due to the high incidence of death in infected humans. In the past, both have been studied intensively by the United States, the U.S.S.R. (now Russia), and other countries for use as military weapons. In addition, only a small number of the organisms need to be used to develop an effective biological warfare weapon. In wartime, enemy soldiers, civilians, and animals have been deliberately infected with them.
Glanders and melioidosis are also classified by the CDC in the Category B disease/agent grouping, the second highest grouping assigned to dangerous biological organisms.
Glanders is a major concern for the safety and health of people who regularly work around experimental or domestic animals. Therefore, people with high risk of glanders infection include those who are in close and frequent contact with infected animals such as animal caretakers, laboratory personnel, and veterinarians.
Melioidosis may remain dormant for many years before producing symptoms. Thus, it can be contracted without any visible signs of infection. As a result, travel to countries where melioidosis frequently occurs is considered risky. People with a higher than normal incidence of melioidosis infection include those engaging in frequent sexual activity with multiple partners and intravenous drug users.
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Raja, N.S., M.Z. Ahmed, and N.N. Singh. “Melioidosis: An Emerging Infectious Disease.” Journal of Postgraduate Medicine 51 (2005): 140–145. Also available online at: <http://www.jpgmonline.com/article.asp?issn=0022-3859;year=2005;volume=51;issue=2;spage=140;epage=145;aulast=Raja>.
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