Snake Fungal Disease identified in wild British snakes for the first time

The IDEXX Anatomic Pathology department has been involved in a multi-institutional study, that has led to the detection of Snake Fungal Disease (SFD) in British and European snakes.

Date:
  1. What is Snake Fungal Disease?
  2. What are the clinical signs/lesions and how severe are they?
  3. Why Now?
  4. What to do if someone sees/finds a dead wild snake?
  5. REFERENCES
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What is Snake Fungal Disease?

Snake fungal disease (SFD) is an emerging disease of conservation concern in some populations of snakes in eastern and midwestern North America.1 Up to now, it has not been reported in wild snakes outside North America.
Fungal pathogens, such as Batrachochytrium dendrobatidis (causative agent of Chytridiomycosis) or Pseudogymnoascus destructans (causative agent of White Nose Syndrome in bats) are emerging in the past decades worldwide and in some cases pose a significant threat to wildlife health. 2

What causes Snake Fungal Disease?

Ophidiomyces ophiodiicola, the causative agent of SFD1,
was first recognised in North America about one decade ago.
Up to now, whilst O. ophiodiicola had been isolated from captive snakes outside North America, the pathogen had not been reported from wild snakes elsewhere. 

How was Snake Fungal Disease found in Europe?

In this study, the screening of 33 carcasses and 303 moulted skins for the presence of macroscopic skin lesions and O. ophiodiicola was performed. The study included wild snakes collected from 2010–2016 in Great Britain and the Czech Republic. The fungus was detected using real-time PCR and further confirmed with follow up culture and histopathologic analyses. 

What are the clinical signs/lesions and how severe are they?

The most consistent clinical signs of SFD in North American snakes, as reported by the USGS3, include scabs or crusty scales, subcutaneous nodules, abnormal molting, white opaque cloudiness of the eyes, or localized thickening or crusting of the skin. The disease severity varies by snake species, and mortality has been associated with some cases of SFD. In the set of European snakes, skin lesions were mild in most cases, but in some snakes, they were severe and were considered likely to have contributed to mortality. 

Snake Fungal disease

Figure 1. In this image taken from the paper you can see (a) typical macroscopic lesions at the scale edges on a grass snake (Natrix natrix); (b) typical histological findings, with thickening and necrosis of the epidermis and dermatitis and (c) Arthroconidia characteristic of Ophidiomyces ophiodiicolaScientific Reports 7, Article number: 3844 (2017) doi:10.1038/s41598-017-03352-1

What’s the impact on wild snakes?
Population-level impact is not yet widely known in some populations of North American snakes and in the population of European snakes.  However, in some areas of North America, SFD has been associated with a decline in certain populations of snakes3

Risk to human health, domestic animals and livestock?
Ophidiomyces ophiodiicola is only known to infect snakes therefore there is no known risk to human or other mammals. The fungal infection has been documented in captive snakes from multiple countries. The possibility that O. ophiodiicola may be transmitted between wild and captive snakes cannot be ruled out4.

Why Now?

Culture characterisations and phylogenetic analyses performed as part of this study indicated that isolates from European wild snakes are different to the North American isolates examined. There is no current evidence to indicate that O. ophiodiicola was recently introduced to Europe, or Europe acted as anintroduction source of the fungus to North America. In this study, it is hypothesized that O. ophiodiicola naturally has a Holarctic geographical distribution and that environmental change together with host factors might be implicated in the emergence of SFD.

What to do if someone sees/finds a dead wild snake?

If a member of the public finds a dead wild snake, the Garden Wildlife Health Project (http://www.gardenwildlifehealth.org/ ), with is part of the Zoological Society of London, can be contacted to discuss further post-mortem examination (email: gwh@zsl.org).

If suspicious skin lesions are noted in captive snakes, please contact us to discuss further testing. 

REFERENCES

1. Lorch, J. M. et al. Experimental infection of snakes with Ophidiomyces ophiodiicola causes pathological changes that typify snake fungal disease. MBio 6, 1–9, doi: 10.1128/mBio.01534-15 (2015).

2. Fisher, M. C. et al. Emerging fungal threats to animal, plant and ecosystem health. Nature 484, 186–94, doi: 10.1038/nature10947 (2012)

3. https://www.nwhc.usgs.gov/disease_information/other_diseases/snake_fungal_disease.jsp

4. http://www.gardenwildlifehealth.org/files/2013/06/Reptile-Snake-Fungal-Disease-factsheet-GWH.pdf