Glanders

Glanders is a contagious and fatal disease of horses, donkeys, and mules, and is caused by infection with the bacterium Burkholderia mallei (the name recently changed from Pseudomonas mallei and was previously classified as Pfeifferella, Loefflerella, Malleomyces or Actinobacillus). The disease causes nodules and ulcerations in the upper respiratory tract and lungs. A skin form also occurs, known as 'farcy'. Control of glanders requires testing of suspect clinical cases, screening of apparently normal equids, and elimination of positive reactors. It is transmitted to humans and all infected/contaminated or potentially infected/contaminated material must be handled in a laboratory that meets the requirements for Containment Group 3 pathogens. Identification of the agent: Smears from fresh material may reveal Gram-negative nonsporulating, nonencapsulated rods. The presence of a capsule-like cover has been demonstrated by electron microscopy. The bacteria grow aerobically and prefer media that contain glycerol. Unlike the Pseudomonas species and the closely related bacterium Burkholderia pseudomallei, Burkholderia mallei is nonmotile. Guinea-pigs are highly susceptible, and males can be used, if strictly necessary, to recover the organism from a heavily contaminated sample. Commercially available biochemical identification kits lack diagnostic sensitivity. Specific monoclonal antibodies and polymerase chain reaction (PCR) as well as real-time PCR assays are available. The latter have also been evaluated in recent outbreaks. Mallein and serological tests: Complement fixation test and enzyme-linked immunosorbent assays are the most accurate and reliable serological tests for diagnostic use. The mallein test is a sensitive and specific clinical test for hypersensitivity against Burkholderia mallei. Mallein, a water soluble protein fraction of the organism, is injected subcutaneously, intradermo-palpebrally or given by eyedrop. In infected animals, the skin or the eyelid swells markedly within 1-2 days. A rose bengal plate agglutination test has recently been developed in Russia; it has been validated in Russia only. Requirements for vaccines and diagnostic biologicals: There are no vaccines. Mallein purified protein derivative is currently available commercially from the Central Veterinary Control and Research Institute, 06020 Etlik, Ankara, Turkey.