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EQUINE VETERINARY EDUCATION / AE / march 2009
151
Clinical Commentary
Glanders and farcy: A re-emerging disease
M. Paar
Clinic for Horses, Alte Dorfstr. 43-45, 27367 Sottrum, Germany.
The Case Report by Elschner et al. (2009) of a Burkholderia
mallei infection in a horse imported from Brazil to Germany
shows the potential risk of an importation of glanders in
areas free from the disease in spite of all official regulations
for import. The International Animal Health Certificate of
the infected animal confirmed that the prescribed
complement fixation test (CFT) was negative and during
veterinary inspection at Frankfurt airport no clinical signs of
illness were registered. Clinical signs of illness were not
registered until 2 weeks after arrival of the horse in its
destination stable.
Knowledge of the disease is the best guarantee for
early recognition of this zoonosis and for epidemic control.
Glanders and farcy (the cutaneous form) are caused by
Burkholderia mallei (formerly Pseudomonas mallei), a short,
rod-shaped, Gram-negative, aerobic, facultative
intracellular, nonmotile and nonspore-forming bacterium
(Nicoletti 2007). The ability of the bacterium to survive
outside the host is relatively low. The infectious agent is
normally inactivated by sunlight, warm temperatures and
drying up in a few days. In dark and humid conditions the
bacterium may survive for months (Wittig et al. 2007).
Disease caused by B. mallei must be reported to the World
Organization for Animal Health (OIE, Office International
des Epizooties, Paris, France).
The principal hosts are horses, donkeys and mules.
Chronically infected equids are the natural reservoir.
Occasional cases of glanders occur in cats, dogs, goats,
sheep and camels. Mice and guinea pigs can be
experimentally infected (Nicoletti 2007). Human infections
arise by contact with secretions or products (meat) of
diseased animals. The portals of entry are usually the
mucous membranes or small lacerations. The disease is
frequently fatal in man if untreated (Wittig et al. 2007).
Glanders is thought to be endemic in parts of the Middle
East, Asia, Africa and South America. Between 1998 and
2007, cases were reported from Brazil, Turkey, the former
USSR, Eritrea, Ethiopia, Iran, Iraq, United Arab Emirates and
Mongolia. The disease may also exist in Pakistan (Anon
2007a). The infected horse reported by Elschner et al.
(2009) was imported from Brazil to Germany.
In equids, glanders is traditionally categorised into
nasal form, pulmonary form and cutaneous form (also
known as farcy). Clinical cases are usually a combination
of these forms, as in the reported case by Elschner et al.
(2009). They can occur as acute, chronic or subclinical
(latent) disease. Donkeys and mules are believed to
develop the more acute form of the disease whereas in
horses the chronic or latent form is more common. The
incubation period varies from a few days to many months;
2–6 weeks is typical (Anon 2007a). In the case reported by
Elschner et al. (2009) clinical signs arose 2 weeks after
arrival of the horse at its destination.
In the cutaneous form, subcutaneous tissues and
lymph nodes are affected. Cutaneous changes are more
common following bacteraemia than after local
contamination of a skin wound. Lymphatic vessels
become swollen and corded with development of farcy
buds, swellings that enlarge, ulcerate and drain an oily,
purulent yellow exudate. In addition there may be swelling
of the joints and painful oedema of the legs. Glanderous
orchitis is a common symptom in males.
In the nasal form, small nodules inside the nasal
passages develop into ulcers, resulting in a thick, purulent
yellowish to bloody unilateral or bilateral discharge.
Healed ulcers become stellate (starlike) scars. Submaxillary
lymph nodes become enlarged and indurated, and may
suppurate or drain. There may be severe congestion of the
liver and spleen. Orchitis may be present.
In the pulmonary form, nodules and abscesses
develop in the lungs. Some infections are inapparent,
others vary from mild dyspnoea to severe respiratory
disease with coughing, dyspnoea, high fever (41°C) and
septicaemia. Horses with glanders either die rapidly or live
for several years with chronic abscessation (most often
regional lymph nodes, lungs, liver, spleen). They may have
varying degrees of respiratory difficulty with no fever. Other
possible clinical signs in affected horses include mild
depression, decreased food intake and infrequent
defaecation (Anon 2007a; Nicoletti 2007; Wittig et al.
2007).
Differential diagnosis of Burkholderia mallei infection
includes other bacterial infections, including meliodosis
(Burkholderia pseudomallei) or diseases caused by
members of the genera Streptococcus, Rhodococcus,
Pasteurella or Mannheimia (Nicoletti 2007). As shown by
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EQUINE VETERINARY EDUCATION / AE / march 2009
Elschner et al. (2009) confirmation of the diagnosis requires
one or more test procedures. In the reported case the final
diagnosis was carried out by means of CFT and skin tests.
Serodiagnosis is hampered by the considerable number of
false-positives and -negatives of the internationally
prescribed tests (Anon 2007b; Elschner et al. 2009). The
major problem leading to low sensitivity and specificity of
the CFT and enzyme-linked immunosorbent assay (ELISA)
has been linked to the test antigens currently used, i.e.
crude preparations of whole cells. The development and
evaluation of serological test kits using well-characterised
single antigens may overcome this problem (Neubauer
et al. 2005). The Mallein tests (subcutaneous nonocular
injection, intrapalpebral injection or administration of
eyedrops of a heat-killed extract of B. mallei) show
hypersensitivity reactions in infected equids. Mallein tests
can give inconclusive results in acute glanders, or in the
late stages of chronic disease (Anon 2007a). Culture,
immunohistochemical staining for bacterial antigen and
polymerase chain reaction (PCR) assays may be used. If
necessary, B. mallei isolation can be attempted by
inoculation of material into guinea pigs which should be
highly susceptible (Strauss test). In the reported case the
diagnosis was supported by a positive PCR result for lung
tissue of the horse, the positive immunohistological results
for sections of subcutis of 2 guinea pigs and characteristic
histomorphological findings in sections of liver tissue.
Re-isolation of the agent failed. As stated by the authors,
the lack of glanders-positive reaction in the other PCRtested tissues and the negative immunohistological results
in the tissues of the horse underline the difficulties to
diagnose glanders.
Animals that test positive for glanders are subjected to
euthanasia in nonendemic areas. Treatment even in
endemic regions is risky, as infections can spread to man
and other animals and they can become asymptomatic
carriers (Anon 2007a).
In summary, the clinician must be aware that the clinical
symptoms of glanders are nonspecific, the incubation
period may be long and the serological tests for importation
may give false negative results. The best prevention for
spread of the disease is keeping it on the list of differential
diagnoses and proceeding with tests in suspicious animals
imported or reimported from endemic countries.
References
Anon (2007a) Glanders, Iowa State University, College of Veterinary
Medicine www.cfsph.iastate.edu/Factsheets/pdfs/Glanders.pdf.
Anon (2007b) Manual of Diagnostic Tests and Vaccines for Terrestrial
Animals. OIE, World Organisation for Animal Health, Paris.
www.oie.int/eng/normes/mmanual/A_00086.htm (16.08.07).
Elschner, M.C., Klaus, C.U., Liebler-Tenorio, E., Schmoock, G., Wohlsein,
P., Tinschmann, O., Lange, E., Kaden, V., Klopfleisch, R., Melzer, F.,
Rassbach, A. and Neubauer, H. (2009) Burkholderia mallei infection
in a horse imported from Brazil. Equine vet. Educ. 21, 147-150.
Neubauer, H., Sprague, L.D., Zacharia, R., Tomaso, H., Al Dahouk, S.,
Wernery, R., Wernery, U. and Scholz, H.C. (2005) Serodiagnosis of
Burkholderia mallei infections in horses: State-of-the-art and
perspectives. J. vet. Med. B, 52, 201-205.
Nicoletti, P.L. (2007) Glanders, In: Equine Infectious Diseases, Eds:
D.C. Sellon and M.T. Long, W.B. Saunders, Philadelphia. pp 345-348.
Wittig, M.B., Wohlsein, P., Hagen, R.M., Al Dahouk, S., Tomaso, H., Scholz,
H.C., Nikolaou, K., Wernery, R., Wernery, U., Kinne, J., Elschner, M.
and Neubauer, H. (2006) Glanders - a comprehensive review. Deut.
Tieraerztl. Woch. 113, 321-360.