Yellow Skin Disease or Yellow Fungus in Bearded Dragons & other Reptiles

Bearded Dragon lizards (Pogona vitticeps) have become extremely popular pets in recent years, perhaps the most popular and suitable reptile pet for beginning reptile keepers. And for good reason as they are relatively hardy, easy to cater for (as far as reptiles go) and have outgoing, engaging personalities akin to our more common mammal pets. They do, like other reptiles, require specialist knowledge and equipment to keep healthy and well however, and often the cost of providing appropriate lodgings and husbandry far exceeds to value of the animal itself. Because they are such common reptile pets, and also many beginner keepers start out with this species I frequently see them in clinic for a range of conditions, many of which can be attributed at least partly to shortcomings in their husbandry (how they are kept and managed) or nutrition. They can suffer from various infectious diseases caused by bacterial infections, various parasites and less commonly fungal infections.

Necrotic ulcer left after sloughing of lesion, with topical ointment

Necrotic ulcer left after sloughing of lesion, with topical ointment

One of the worrying trends being observed worldwide, but noticeably in the past several years in the UK is the spread of a specific fungal pathogen that can cause severe skin infections or fungal dermatitis and ultimately death in Bearded Dragons primarily, but also some other reptile species. The pathogen responsible is a fungal organism with the rather long-winded scientific name of Chrysosporium Anamorph of Nanniziopsis vriesii (CANV) which is colloquially known amongst hobbyists as ‘Yellow Skin Disease’ of Bearded Dragons. This is an aggressive fungus which invades the superficial and deep layers of the skin and causes discolouration of the skin, necrotic lesions which slough off revealing sensitive ulcerated tissues underneath the scales and diffuse painful subcutaneous swelling and inflammation. In severe cases the hyphae of the fungus, which are microscopic root like filaments, can extend deeper into the animals body cavities and internal organs often causing marked pathology and eventually death.

Beardie with ulcerating, hyperkeratotic necrotic lesions, skin swelling & discoloration

Beardie with ulcerating, hyperkeratotic necrotic lesions, skin swelling & discoloration

 

 

Transmission of the fungus responsible is thought to be from direct contamination with the fungal agent encountered in the environment, and is easily spread throughout reptile collections and other facilities housing large numbers of animals by keepers and on equipment. The incubation period from the time infection occurs to the development of visible signs can be several weeks to over a month so it is often difficult to pinpoint the exact source of infection, especially in newly acquired animals. Suboptimal husbandry conditions such as low temperatures and poor hygiene practices are often responsible for predisposing animals to this disease. However many well cared for and otherwise healthy animals can become infected if exposed to the pathogen also.

After infection, the early signs of disease usually present as dry, crusty, hyperkeratotic lesions and discoloration of the skin which can lead to patches of retained skin after shedding. Excessive or more frequent shedding is common at this stage of disease also. These lesions generally progress over several weeks to months and become necrotic and exudative meaning the skin starts to die and release infectious discharge. Wet, scabby lesions form on the surface of the skin and eventually slough off or can be lifted off when cleaned to reveal pustular discharge underneath and ulcerated inflamed soft tissue devoid of the superficial skin layers or scales. These ulcers are obviously very painful and prone to secondary bacterial infections. Once the disease has advanced this far it can be quite difficult to treat successfully. Recovery and regeneration of new skin takes a considerable period of time, and the animal is often left with extensive scar tissue if it survives. Lesions are commonly found on or near the mouth or head but can be found anywhere on the body. Other diseases which may be confused for this condition include bacterial dermatitis, stomatitis, thermal burns and indeed other fungal skin infections. Diagnosis is made based on clinical signs, appearance, and testing skin samples or tissue biopsy for the organism itself using PCR, microscopy or culture techniques.

Exudative, crusting lesion typical of Yellow Skin Disease of Bearded Dragons

Exudative, crusting lesion typical of Yellow Skin Disease of Bearded Dragons

 

 

Treatment is multimodal and involves the use of an oral antifungal drug called Itraconazole which needs to be given every day for 4-6 weeks in most cases. Antibiotics are sometimes used also to treat or guard against secondary bacterial infections. Topical cleaning with chlorhexidine is recommended as well as the application of topical antifungal agents such as miconazole or F10 ointment. Topical agents alone are not indicated for a successful outcome however, as it appears that most success is achieved using systemic antifungal treatment with oral itraconazole at the correct dose rate. For this reason it is crucial if you have an animal you think might be affected to seek the advice of an experienced reptile veterinarian. The disadvantage of using this drug is that it can have severe side effects with long term use however, especially with regard to liver function and particularly in already debilitated animals. It is crucial therefore that affected lizards are treated early, appropriately and that supportive care is given in the form of supplemental feeding and hydration if necessary. Monitoring of liver function during treatment may be necessary in some cases, which requires blood sampling. Aggressive surgical debridement of lesions is sometimes warranted also to reduce the presence of the fungal agent and aid in treatment. I have treated several suspected and confirmed cases of this disease in Bearded Dragons and one suspected case in a chameleon. Sadly not all of them have survived. In two cases where a single limb was affected I amputated the affected limb and the Beardie went on to live a very happy life.

If caught early, this disease can be treated successfully. It is critical to prevent the spread of the organism to other reptiles so isolation of the affected animal and great care to prevent mechanical transmission on owners hands, clothes or equipment is recommended. Rigorous cleaning and disinfection of cages, furnishings and equipment is also crucial in limiting spread of the organism or re-infection as well as discarding all contaminated substrate or porous materials from the affected animals vivarium. The disease is not zoonotic meaning it does not readily transmit to humans as it is primarily a reptile pathogen. However there have been a few reports of CANV isolated from severely immunocompromised human patients so sensible hygiene precautions that should be implemented with any ill pet need to be taken.

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The new thinking on neutering pet ferrets.

ferret scan

 

We have seen several ferrets in my clinic (www.richmondvets.co.uk) in recent months. One of the common questions from owners regards neutering and spaying pet ferrets. Ferrets are unusual creatures in that females, or Jills, are ‘induced-ovulators’. This means that they require mating to take place in order to ovulate, otherwise they can remain in season or oestrus for long periods of time. When this occurs high levels of oestrogen for months on end can lead to serious consequences including a fatal anaemia due to bone marrow suppression.

Traditionally, the solution to avoiding persistent oestrus was either to mate your Jill to a male ferret or Hob, to use a vasectomised (infertile) Hob to mate with the Jill thus avoiding an unwanted litter, spaying the Jill to remove the ovaries and therefore source of hormones, and finally the most popular method of using a ‘Jill-jab’ steroid injection to suppress oestrus each Spring before she came into season.

The problem however of spaying female ferrets is that removing the source of oestrogen creates a hormonal imbalance relating to the pituitary gland in the brain. Because there is a lack of oestrogen being produced, the pituitary gland starts to release excessive Gonadotrophin-Releasing Hormone (GnRH) in an effort to stimulate the now absent ovaries. Unfortunately, in many ferrets this overproduction of GnRH over time leads to changes within the adrenal glands and adrenal disease develops.

Male ferrets once sexually mature develop a pungent smell, greasy coat and often start spraying urine as a territorial behaviour, which makes living with them in the home quite difficult in some circumstances. Traditionally, castration was advised as a solution to these problems but again removing the testes disrupts the normal hormonal balance in the body and can lead to adrenal disease later in life. Vasectomised ferrets used for mating with females and reducing persistent oestrus problems are infertile yet retain their testicles so continue to produce testosterone and exhibit male behaviours.

Adrenal disease is reasonably common in older ferrets and can have serious side effects on other organ systems as well as being life-limiting in itself. Recent studies have shown a significant risk of adrenal disease in neutered ferrets, therefore the recommendation in recent years is to avoid surgical castration or spaying of male and female ferrets. Luckily, there is a hormonal implant developed for use in dogs which has now been licensed for use in ferrets also, therefore allowing all the benefits of surgical neutering in male and female ferrets including rendering them infertile without the added risk of future adrenal disease.

The implant itself contains a drug called Deslorelin and is slightly larger than a standard pet microchip. In most cases in order to ensure comfortable and safe insertion the ferret is given a small amount of anaesthetic gas so it is unconscious during insertion of the implant. Generally the process needs to be repeated every 18-24 months as the implant has slow release activity and eventually it’s efficacy runs out and it is absorbed by the body. There is also a stronger dose implant available which can last up to 4 years for an adult ferret.

Modern veterinary advice regarding control of reproduction in ferrets highly recommends using this implant technique rather than surgical neutering in order to reduce the incidence of adrenal disease later in life. The implant can be placed once your pet ferret has reached puberty and become sexually mature.

All the best,

Sean.

Lungworm in dogs, but what about in reptiles?

Throughout the UK we are seeing a rise in the number of lungworm cases in dogs, which is a life threatening condition if left untreated, and is carried by slugs, snails and foxes. More information here:

http://www.richmondvets.co.uk/slugs-snails-and-puppy-dog-tales/

However, I’ve recently been asked about the risks of lungworm for pet reptiles on an exotic forum I contribute to. Some reptile keepers were discussing feeding snails to their lizards and wondered if this parasite could be passed on considering slugs and snails in the UK are the intermediate host for canine lungworm (Angiostrongylus vasorum). I have to admit my answer was I didn’t know for certain what the risk was if any, but I did know that amphibians such as frogs could act as an intermediate host when preying on infected slugs and snails. I also knew of certain other parasites of the lungs and circulatory system that specifically infect reptiles so thought I would write a short blog post to clear up any concerns.

The canine lungworm (A. vasorum) requires that the eggs shed in faeces of the primary mammalian host (dog or fox) are ingested in the environment by an intermediate mollusc host such as a slug or snail. The parasite then undergoes a further stage of development in the snail host before shedding infective cysts into the environment in the hope that these are ingested again by a canine such as a dog or fox. However, there is evidence that UK common frogs act as a host for the parasite also, either as an intermediate host like the snail or as a paratenic host depending which infective stage it becomes infected by (http://link.springer.com/article/10.1007%2FBF00931834?LI=true).

Lungworm cycle with frogThe term paratenic describes a host which is not essential for the development of the parasite, but can maintain the parasite and shed infective stages until the next part of the life cycle can resume. So in this example the snail and canine host can continue the cycle from ingestion of infective stages in frog faeces. Similarly, frogs can infect dogs directly if they are ingested. In most paratenic hosts there are no discernible ill effects of infection, as they merely act as a vector of infective stages to the required hosts by environmental transmission. However, it is well recognised in the field of parasitology that intermediate and paratenic hosts can undergo subtle changes in behaviour and physiology engineered by the parasite itself, that ultimately lead to an increased likelihood of ingestion by the definitive or primary host. So for example, it has been shown that mice (intermediate host) infected with certain nematodes show increased diurnal activity and diminished predator avoidance behaviours leading to increased death by predation in infected individuals, thus aiding transmission to the mammalian or avian predator (definitive host). For these reasons, if we can avoid infecting our captive reptile pets with potentially harmful parasites we should make a substantial effort to do so. As an aside, this was the topic for my undergraduate dissertation, so parasitology and parasite behaviour is a fascinating area for me. Here’s some amazing evolutionary adaptations of parasites and their hosts if you are interested:

http://essaybank.degree-essays.com/biology/host-behaviour-manipulation-by-helminths.php

Anyway, back to canine lungworm and feeding snails to pet reptiles, or amphibians for that matter. There have not been many studies into the effects of this parasite on reptiles mainly because there are no apparent economic reasons to undertake such studies, although it has been recognised that they can act as paratenic hosts. Because the common frog has been proven to act as both paratenic and intermediate host, presumably with the subsequent changes associated with infection above, I would warn against feeding native wild caught slugs and snails to captive reptiles and amphibians as a result. If the frog can act as both intermediate and paratenic host then it is likely that native reptiles can, and by default I would suggest that non-native amphibians and reptiles could also be at risk. The likelihood is that even if captive reptiles do not have any ill effects, over time the parasite burden may become heavy resulting in debilitation or complicating other health issues, and could even act as a reservoir of infection for dogs in the household. Equally, as the effects of infection are not known it is better to be safe than sorry, and so finding alternatives to using wild snails and slugs is probably the safest option. One method would be culturing your own mollusc supply, using either Giant African Land Snails which are readily available and easy to culture, or obtaining a supply of edible snails from the restaurant supply trade and culturing these at home as a food source for your reptile pets, many of which specialise or at least are adapted to consuming such prey in the wild. Caiman Lizards, skinks, certain Chameleons, salamanders and frogs all relish snails and slugs in their diet. If you are considering feeding such items a captive bred clean supply is probably the best source. It is also important to beware feeding wild snails and slugs due to the risk of slug bait poisons and insecticide or herbicide residues, even if you don’t use them in your own garden. You would be surprised how far a hungry slug can travel, and can’t always be sure your neighbours are as environmentally-minded or pet-conscious with their use of chemicals.
Apart from the possible risk of infection with canine lungworm, reptiles and amhibians can become infected with specialised lungworm parasites of their own leading to ill health and even death in some cases. It is important to be aware of the risk of parasites in general in captive reptiles, and routine parasite screens should be carried out on any new additions to a collection as well as annual or biannual screening tests in large collections. Protozoan infections, roundworms, tapeworms and pinworms are the most common offenders, but lungworm infections are also being diagnosed more and more frequently in the reptile trade. Reptile lungworms include Rhabdias spp. in snakes and Entamelas spp. in lizards. They are spread by direct transmission, differing from the canine lungworm in that they have no intermediate host. Eggs shed in faeces are directly infectious to the host reptile and other uninfected individuals that come in contact with this environmental contamination. Infection occurs through ingestion of faecal contaminated material or direct penetration by the larvae through the skin of the host. This mode of transmission means it is extremely easy to unwittingly spread the parasite widely through a large reptile collection. The most common findings in infected individuals are respiratory signs such as gaping, wheezing, foamy secretions from the airway and respiratory distress resulting from pneumonia. It is important to consider this parasite as a potential factor in respiratory infections that are longstanding or do not respond to standard effective treatments. As with most parasites, the eggs of the parasite are easily found on routine faecal examination or sometimes by examining saliva and respiratory secretions under the microscope. Reptiles that show these symptoms should always be isolated from healthy animals. Quarantining wild-caught or new additions to a collection is always recommended. If any of the above symptoms are noticed or if your reptile is generally unwell and fails to thrive a faecal parasite screen and examination by a competent, experienced vet is recommended.

I hope this topic was of interest and if you have any other suggestions for blog topics please leave them in the comments or on our Facebook or Twitter pages at Sean McCormack Mvb and @ExoticPetVet.

All the best,

Sean.

Getting back to writing….

I’ve neglected this blog I started ages ago, mainly due to personal and professional time constraints and focusing on social media platforms to share quick snippets of information and photos of my work. My Facebook (Sean McCormack Mvb) and Twitter (@ExoticPetVet) contain lots of advice, interesting case studies and photos, so feel free to have a browse of each. However, I’ve been putting various writing projects on the long finger for quite some time, and have decided to dedicate a few hours on my day off from clinics towards writing articles of my own. I would be really interested to hear from you regarding topics you’d like me to write about. Please post in the comments or on my social media pages if you have a specific request. Would love to hear from you.

Currently I write for the wonderful US based publication, Herpetoculture House Digital magazine (http://herphousemag.com/), which I would encourage anybody serious about reptiles to subscribe to. It is well worth a read and if you enter my offer code ‘HERPVET’ at checkout it will get you a 30% discount! I also write occasional articles for some UK based publications.

But I wanted to focus on my own blog, where I can accumulate lots of interesting topics for exotic pet owners as well as other vets. Feel free to share and link to my blog, I would appreciate your help in reaching a wider audience. Here’s to a new start, and I hope you find my musings and ramblings entertaining and informative.

All the best,

Sean.