Mycobacterium spp

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Transmission electron microscopic view of M. bovis
Gross appearance of ferret lung at postmortem, showing tuberculous lesions throughout the lung parenchyma[1]

Mycobacterium spp are a fastidious, slow-growing aerobic, non-spore-forming, gram-positive bacteria which can cause zoonotic disease in humans.

This disease is commonly reported in ferrets across New Zealand, but rarely in Australia and Europe[2].

Infections are thought to be via airborne contamination from cattle pastures or spreading within the wild ferret populations. In New Zealand, there is a causal link between possum abundance and the prevalence of mycobacteriosis in feral ferrets in areas in which M. bovis infection is known to occur, suggesting that possum-to-ferret transmission of disease accounts for most of the disease evident in ferret populations[3].

Species which are pathogenic to ferrets include:

  • Mycobacterium abscessus[4]
  • mycobacterium avium complex[5]
  • Mycobacterium bovis[6]
  • Mycobacterium genavense
  • Mycobacterium microti
  • Mycobacterium celatum[7]
  • Mycobacterium chelonae[8]
  • Mycobacterium fortuitum
  • Mycobacterium florentinum
  • Mycobacterium interjectum
  • Mycobacterium intracellulare
  • Mycobacterium holsaticum
  • Mycobacterium septicum/peregrinum[9]

Localised nontuberculous mycobacterial infections have been reported in the skin and spleen[10], but systemic disseminated mycobacteriosis is more common.

In mycobacteriosis, ferrets show clinical signs of coughing, weight loss, lymphadenopathy, intermittent anorexia, vomiting, and mild diarrhea. Sudden deaths may occur due to rupture of pulmonary tubercules, but many ferrets display chronic wasting forms of the disease. Reports of concurrent mycobacteriosis and lymphoma have been recorded, suggesting an immunocompromised state in some animals[11].

Diagnosis is based on radiographic findings suggestive of pulmonary masses supported by culture of the organism in vitro. PCR assays are available in some reference laboratories.

A differential diagnosis would include other causes of pneumonia such as pasteurellosis.

Treatment of mycobacteriosis is problematic due to the hardiness of this bacterium and the extent of dissemination by the time a diagnosis is determined. Broad-spectrum multiple antibiotics such as enrofloxacin, rifampicin and azithromycin may assist in resolution of clinical signs.

References

  1. Ludwig E et al (2011) Risk for Mycobacterium celatum infection from ferret. Emerg Infect Dis 17(3):553-555
  2. Caley P (1998) Broad-scale possum and ferret correlates of macroscopic Mycobacterium bovis infection in feral ferret populations. N Z Vet J 46(4):157-162
  3. Caley P et al (2001) The relationship between prevalence of Mycobacterium bovis infection in feral ferrets and possum abundance. N Z Vet J 49(5):195-200
  4. Lunn JA et al (2005) Pneumonia due to Mycobacterium abscessus in two domestic ferrets (Mustelo putorius furo). Aust Vet J 83(9):542-546
  5. de Lisle GW et al (2008) Isolation of Mycobacterium bovis and other mycobacterial species from ferrets and stoats. Vet Microbiol 132:402–407
  6. Pollock C (2012) Mycobacterial infection in the ferret. Vet Clin North Am Exot Anim Pract 15(1):121-129
  7. Butler WR et al (1993) Mycobacterium celatum sp. nov. Int J Syst Bacteriol 43:539–548
  8. Iyengar KP et al (2012) Mycobacterium chelonae hand infection following ferret bite. Infection Aug 29
  9. de Lisle GW et al (2008) Isolation of Mycobacterium bovis and other mycobacterial species from ferrets and stoats. Vet Microbiol 132(3-4):402-407
  10. Piseddu E et al (2011) Detection and molecular characterization of Mycobacterium celatum as a cause of splenitis in a domestic ferret (Mustela putorius furo). J Comp Pathol 144(2-3):214-218
  11. Saunders GK & Thomsen BV (2006) Lymphoma and Mycobacterium avium infection in a ferret (Mustela putorius furo). J Vet Diagn Invest 18(5):513-515