Glanders
The glanders is caused by Burkholderia mallei (previously known as Malleomyces mallei) and it is a serious contagious disease of equines. Infected equidae are the reservoir. The causative organisms are true parasite because these are unable to survive in nature for long periods without its host. B. mallei is a gram-negative, non-motile aerobic rod and it produces a carbohydrate capsule. B. malleii is diffetrentiated from B. pseudomallei by being non-motile organisms. B. pseudomallei causes “meliodosis”. B. mallei can be grown on media containing glycerol or blood. It does not grow on MacConkey agar or at 420C.
Glanders is zoonotic, and is transmitted to humans by direct contact with sick animals or infectious materials or through ingestion of glandered meat. Cases of human-to- human transmission have been reported.
Transmission: The disease is introduced into equine populations by infected animals. Ingestion of B. malleii, which is present in high numbers in secretions of infected individuals, is the most common route of infection. Skin invasion and inhalation are regarded as minor routes of transmission. Use of common utensils or watering troughs may transmit the disease.
Symptoms: Glanders usually manifests as a chronic infection in horses, and infected animals may survive for several years. Disease occurs in nasal, cutaneous (farcy), and pulmonary forms, all of which may occur simultaneously in one animals. Clinical signs include catarrhal nasal discharge from one or both nostrils, gray to yellow nodules on the upper respiratory mucous membranes, submaxillary lymphadenopathy, dyspnea, weight loss and nodules and or ulcers along the cutaneous lymphatics.
Diagnosis: Bacteriological culture of nodular contents on blood or glycerol agar is useful. Guinea pigs and hamsters are highly susceptible to fatal infection with virulent strains. Serologically, glander is diagnosed by complement fixation test (CFT), ELISA, direct hemagglutination and counterimmunoelectrophoresis using aqueous bacterial extract as antigen. Indirect fluorescent antibody test may be used. A polymerase chain reaction (PCR) using primers specific for B. mallei can easily detect and identify B. mallei infection. Male guinea pigs injcted intraperitonealy with infected clinical material develop orchitis if the inoculum contains B. mallei, the so called Strauss reaction (the exudative swelling of the scrotum in male hamsters and guinea pigs upon subcutaneous or intraperitoneal inoculation of Pseudomonas mallei). Mallein testing by intradermal inoculation of the antigen is recommended for diagnosing a case of glanders.
Treatment and control: Horses are screened using mallein inoculated intradermal palpebrally. The reactors may be destroyed. The mallein is manufactured and supplied by Division of Biological Products, Indian Veterinary Research Institute, Izatnagar (Utar Pradesh) for its supply. B. mallei is usually sensitive to tetracyclines, fluoroquinolones, gentamicin and sulfonamides. These antimicrobial agents may be used to treat human cases, however, treating infected equids is discouraged. There is currently no commercially available vaccine for glanders.