Fungal infections overview
Synonym(s): Mycosis, Mycoses, Mycotic infections
Introduction
- Cause: fungal agents (either primary contagious, or opportunistic ubiquitous/commensal organisms).
- Signs: dermatological lesions, generalized illness, signs of systemic disease.
- Diagnosis: fungal cultures, histopathology, molecular analysis/PCR.
- Treatment: antifungals, treatment of secondary bacterial infections, analgesia, supportive care, correction of predisposing factors/husbandry deficiencies.
- Prognosis: poor to good (depending on agent and stage of progression).
Presenting signs
- Dermatitis.
- Cutaneous erosions/ulcerations.
- Cutaneous vesicles.
- Cutaneous granulomas/pyogranulomata.
- Pododermatitis.
- Cutaneous crusting.
- Cutaneous discoloration - yellowing in bearded dragons (Nannizziopsis guarroi) .
- Dysecdysis Ecdysis/dysecdysis.
- Lethargy.
- Anorexia Anorexia.
- Facial disfigurement (Ophidiomyces in snakes).
- Lingual multifocal abscessation (Chamaeleomyces in chameleons).
- Conformational deformities resulting from osteomyelitis Osteomyelitis.
- Death.
Acute presentation
- Usually slow-developing, but may present as mortality, lethargy, anorexia in systemic infection.
Geographic incidence
- Worldwide.
Breed/Species predisposition
- Former Chrysosporium anamorph of Nannizziopsis vriesii complex (CANV complex) agents:
- Ophidiomyces ophidiicola: snakes (terrestrial and semiaquatic species).
- Nannizziopsis spp: lizards and crocodilians.
- Nannizziopsis guarroi (Chrysosporium guarroi): especially green iguanas and bearded dragons.
- Paranannizziopsis spp: squamates and tuataras.
- Chamaeleomyces granulomatis: chameleons.
- Chamaeleomyces viridis: chameleons and bearded dragons.
- Opportunistic environmental fungi, eg Aspergillosis spp, Candida spp, Fusarium spp, Geotrichum spp, Penicillium spp, Trichophyton spp, Cryptococcus spp: most reptiles.
Public health considerations
- Zoonotic transmission from reptiles not reported, however immunocompromised individuals should remain cautious and the potential for zoonotic infection with fungal agents of reptilian origin cannot be completely excluded.
- Nannizziopsis hominis and Nannizziopsis obscura are both known to cause disease in humans, however these have not been isolated from reptiles.
Cost considerations
- Prolonged treatment, preferably with monitoring of blood parameters, will often be required.
Special risks
- Systemic/internal infections may infiltrate and affect any organs, with increased risk for anesthesia.
- Fungal infections often infiltrative into surrounding tissues, making surgical excision more challenging.
Pathogenesis
Etiology
Primary contagious fungal agents
- Former CANV complex agents:
- Nannizziopsis spp.
- Paranannizziopsis spp.
- Ophidiomyces spp.
- Chamaeleomyces spp.
Opportunistic (ubiquitous) fungal agents
- Aspergillosis spp.
- Candida spp.
- Fusarium spp.
- Geotrichum spp.
- Penicillium spp.
- Trichophyton spp.
- Cryptococcus spp.
- Purpureocillium lilacinum.
- Fusarium spp.
- Beauveria bassiana.
- Trichoderma spp.
- Mucor spp.
- Paecilomyces spp.
Predisposing factors
General
Contagious agents
- Open collections.
- Poor biosecurity.
- Substandard quarantine practices.
Opportunistic agent infections
- Overwhelming exposure.
- Immune compromise.
- Stress.
- Substandard husbandry/environmental conditions.
- Open skin lesions.
Specific
- Skin damage.
- Necrotic tissues secondary to cardiovascular/circulation issues.
Pathophysiology
- Primary agents
- Many of the opportunistic pathogens are commensals or environmental; pathogenicity requires damage to animal defenses (physical wound and/or immune compromise) to invade tissues.
Timecourse
- Typically slow-developing lesions.
Epidemiology
- Nannizziopsis guarroi ('yellow fungus disease'):
- Is an obligate fungal pathogen.
- It was first recognized in the early 2000’s.
- It is unclear as to what may have caused recent affinity for reptilian hosts.
- Climate change has been suggested as a potential contributing factor.
- Historical infections may have occurred and may have been misidentified.
- Most infections have been reported in the USA and Spain.
- It remains unclear which factors lead to susceptibility.
- Ophidiomyces ophidiicola (snake fungal disease (SFD) syndrome):
- Has caused widespread morbidity and mortality in wild snakes, reported especially in North America.
- Was incriminated in 2008 as cause of facial disfigurement in eastern massasaugas in Illinois.
- Has been observed in timber rattlesnakes in New England and Massachusetts.
- A wild black rat snake and several copperheads were subsequently confirmed to have O. ophidiicola infection in New Jersey.
- It has since been identified in Europe and Australia.
- Samples from wild snakes in the United Kingdom between 2010-2016 confirmed the presence of Ophidiomyces ophidiicola.
- Much information is still to be learned about this fungus and its impact on free ranging wildlife, the epidemiology of O. ophidiicola in ecosystems remains poorly understood.
- Free ranging snakes may clear the infection or remain chronically infected with variable clinical signs.
- Chameleomyces granulomatis:
- Was first reported more than four decades ago in 4 out of 50 jeweled chameleons imported to France from Madagascar.
- Was recently identified as the cause of disseminated mycotic infection in veiled chameleons in a Danish zoo.
- Has caused multiple mortalities in Jackson’s chameleons at a zoological collection in New Zealand.
- The source of the fungus and its means of dissemination throughout a collection remain unknown.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Lind C M, McCoy C M & Farrell T M (2018) Tracking outcomes of snake fungal disease in free-ranging Pygmy rattlesnakes (Sistrurus miliarius). J Wildl Dis 54 (2), 352–356 PubMed.
- Paré JA & Sigler L (2016) An overview of reptile fungal pathogens in the genera Nannizziopsis, Paranannizziopsis and Ophidiomyces. J Herpetol Med Surg 26 (1-2), 46-53 VetMedResource.
- Schmidt V (2015) Fungal infections in reptiles – an emerging problem. J Exotic Pet Med 24 (3), 267-275 VetMedResource.
- Mitchell M A (2011) Zoonotic diseases associated with reptiles and amphibians: An update. Vet Clin North Am Exotic Anim Pract 14 (3), 439-456 PubMed.
- Abarca M L, Castellá G, Martorell J & Cabañes F J (2010) Chrysosporium guarroi sp. nov. a new emerging pathogen of pet green iguanas (Iguana iguana). Med Mycol 48 (2), 365-372 PubMed.
- Van Waeyenberghe L, Baert K, Pasmans F et al (2010) Voriconazole, a safe alternative for treating infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii in bearded dragons (Pogona vitticeps). Med Mycol 48 (6), 880-885 PubMed.
Other sources of information
- Perry S M, Sander S J & Mitchel M A (2016) Integumentary System. In: Current Therapy in Exotic Pet Practice. Eds: Mitchell M A & Tully T N Jr. Elsevier Saunders, USA. pp 17-76.
- Paré J A (2014) Update on Fungal Infections in Reptiles. In: Current Therapy in Reptile Medicine and Surgery. Eds: Mader D & Divers S J. Elsevier Saunders, USA. pp 53-56.
- Pare J A, Sigler L, Rosenthal K L & Mader D R (2006) Microbiology: Fungal and Bacterial Diseases of Reptiles. In: Reptile Medicine and Surgery. Ed: Mader D R. Saunders Elsevier, USA. pp 217-226.
Organisation(s)
- British Veterinary Zoological Society (BVZS). Website: www.bvzs.org.
- Association of Reptilian and Amphibian Veterinarians (ARAV). Website: https://arav.org.