As veterinarians, we often deal with skin problems affecting dogs and cats; atopy, feline miliary dermatitis, flea allergy dermatitis and more. Our clinical training has prepared us for dealing with these problems, but we may not be as learned when it comes to diseases of the skin of exotics. Feathers and scales may be unique, but the principles of dermatology remain the same. Skin scrapings, biopsies, microbiological cultures and other ancillary diagnostics may be performed on birds, exotic mammals and reptiles to aid in the diagnosis of dermatological problems. Let's go through some of the more common problems associated with the skin, feathers and scales of some non-domestic pets.
Skin and feather problems are commonly encountered in avian patients, and there can be many causes. Many birds are presented with feather picking as a primary complaint, and although the pet bird owner comes in looking for, and hoping for a quick fix for the problem, in most cases, feather picking is frustrating for the avian practitioner. The cause if often multi-factorial, and even if the causes are uncovered, the picking may have developed into a bad habit, much like nail-biting is to humans. There is no magic bullet to cure feather picking in each and every case. The feather picking bird must be diagnosed and managed individually.
Feather pickers must receive a thorough work-up. A CBC, chemistry panel, Psittacine Beak and Feather Disease (PBFD) test, chlamydophila panel, fecal parasite exam, choanal and cloacal bacterial cultures, fungal isolation, radiographs, and polyomavirus testing should all be performed. In addition, a skin and follicle biopsy may be diagnostic, feather pulp culture and skin scrapings may also prove helpful.
New information indicates that chronic problems with lead or zinc toxicosis may be involved with feather picking. It seems that birds are quite sensitive to zinc toxicosis, and this may be manifested by feather picking, pruritis and dry, flaky skin. So, in addition to the standard battery of tests that should be performed on the feather picking parrot, serum zinc and blood lead levels should also be run. Several good chelating agents are available for use in birds, including both injectable and oral medications.
If organic causes of feather picking are ruled out, then the problem must be approached from a behavioral standpoint. Some veterinary practices now employ a bird behavior consultant, or recommend behaviorists who can set up phone consultations to offer suggestions for picking problems.
Feather problems not related to picking may occur. Feathers with stress bars may indicate a disruption in the normal metabolism of a bird during the time that those feathers were developing. In young birds, this may indicate previous illness, administration of medication, chilling of the bird, malnutrition, endogenous steroid release, administration of exogenous steroids or crop stasis. It may be important to note that administration of fenbendazole, metronidazole or other drugs may affect developing feathers and cause temporary feather abnormalities (which will resolve upon the next molt.)
Birds that survive polyomavirus infection will often have dystrophic feathers. This may mimic feather abnormalities seen with viral infection with PBFD. These two viruses may be differentiated by the DNA PCR probes that are commercially available.
Parasites may be involved with some cases of feather picking and pruritis. Giardia may cause intense itching, and a bird infested with giardia may yank feathers in frustration and squeal in pain as the feather is pulled. Definitive diagnosis may be difficult and may require repeated fecal saline wet mounts, ELISA testing or phase-contrast microscopy.
Another parasite may cause skin problems. The Knemidokoptes mite, also called the scaly leg and face mite, is most frequently found in the budgerigar, although it may occasionally occur in other psittacines and passerines. Usually, it causes a powdery appearance to the cere, beak, legs, feet and cloaca, but it may also be found around the eyes. It may cause beak deformities. Diagnosis may be made utilizing skin scrapings. It has been suggested that there may be a genetic predisposition to these mites or immunosuppression may be a factor in the development of clinical disease.
Skin disease in birds is often related to malnutrition or hypovitaminosis. This is most commonly seen in birds still consuming all-seed diets. Hypovitaminosis A may result in epithelial dysplasia or hyperkeratosis. Certainly, many conditions may result in dermatitis, but be sure to put zinc toxicosis on the list of differentials.
Poxvirus may occasionally be responsible for crusty skin lesions in canaries or psittacines. Poxviruses are often quite species specific, but certain groups of birds may be susceptible to some poxviruses.
It should be noted that some birds, especially lovebirds, may develop intense pruritis to the wing webs or back, resulting in chronic ulcerative dermatitis. Often there will be dry, hyperkeratotic skin at the periphery of open, bloody lesions, with intense itching and self-mutilation.
Some birds, most notably Moluccan cockatoos, may progress beyond feather picking to self-mutilation. A cockatoo that is mutilating flesh may require a collar to prevent further mutilation until the situation is under control. This is the only time that I recommend the use of a collar. Mutilation problems can be extremely frustrating, as well as dangerous and perhaps life-threatening. The mutilating parrot should receive the same work-up as for the feather picker, with the addition of the biopsy of any lesions and culturing of the lesion. Even if the fecal parasite exam is negative, it may be worthwhile to treat the bird for both ascarids and tapeworms. I have had some mutilators resolve after two injections with praziquantel to treat their cestodiasis infection.
It should be noted that occasionally a bird may be presented with dry skin and episodic illness. It is important to obtain a complete history, as I have recently had two separate birds that developed skin conditions and sickness as a result of the owners shampooing their birds with human products. Washing a bird with any type of soap should only be undertaken for specific reasons under the direction of an avian veterinarian. Bathing a bird with soap will strip the skin and feathers of natural oils and secretions from the uropygial gland. This may result in dry skin and having the bird develop problems thermoregulating. This stress may then precipitate secondary infections and perhaps mild signs of toxicity from ingesting the soap residue when the bird preens. Had I not asked about bathing their birds, I might not have figured out just what was making these two birds sick.
Skin problems are also not uncommon in reptiles. Novice herp owners may offer their snakes live rats or mice, and if they are not immediately consumed, the rodent may inflict bite wounds along the sides and back of the reptile. Herpers should be told that live rodents must never be left unattended with reptiles or amphibians, and if live prey is not consumed within 15 minutes, the reptile probably won't eat that day. Even if the prey is prehended, a live rodent may bite in self-defense, which may result in wounds to the head, lips, eyes or tongue. If at all possible, herps should be trained to accept pre-killed prey to avoid the possibility of bite wounds.
Bite wounds should all be considered contaminated. Sedation may be required to facilitate treatment. Wounds should be flushed with sterile saline. The major difference between herps and mammals is that it may take up to a year for some serious wounds to heal in herps. Defects should be sutured after infection has been controlled, if possible, or allowed to granulate in. Large defects may need to heal by second intention. Systemic antibiotics should be administered, based on culture and sensitivity results and most wounds should be bandaged. Silver sulfadiazine and povidone iodine are excellent choices for topical therapy. Dysectysis may occur as a result of the bite wounds, and it may take up to 10 shedding cycles before a large wound is completely healed. Soaking may be necessary to assist in a partial shed due to wounds. Large wounds usually result in scars and disruption of the normal scale patterns.
Green iguanas, Iguana iguana, especially imported hatchlings, may develop brown or black lesions on the skin. These may progress, and the baby iguana may become systemically ill, and may actually die as a result of the anorexia. For years, there has been speculation as to the cause of this condition, and this author has performed extensive testing on imported hatchlings to try and determine the etiology. Cultures of full-thickness skin biopsies of the lesions and histopathology have shown that this skin problem is the result of a yeast called Geotrichum candidum. The lesions in baby green iguanas usually occur during the rainy season, when conditions would favor the growth of this organism. Also, baby iguanas are often kept in crowded conditions, when it is likely that their skin could be scratched or punctured by their sharp toenails. Once the skin is compromised, the yeast could then begin causing disease.
Iguanas with skin lesions that stop eating should be given good support care, be treated for any parasitic infestations and be kept in a warm, dry location. Force-feeding may be advantageous. The diagnosis may be obtained by skin scrapings, culturing the lesions or histological examination of biopsy specimens.
Treatment may consist of both topical and systemic antifungal medications. Povidone iodine will kill superficial yeast, and ketaconizole cream is often quite effective. Systemic treatment with ketaconizole or fluconizole may be necessary, in addition to topical treatment. Once the baby iguana undergoes ecdysis, it will often shed off a significant portion of the lesions.
The most common parasites found on the skin of herps are ticks and mites. Ticks should be manually removed, if possible. Mites may be more problematic to eradicate. It is necessary to thoroughly disinfect the environment, in addition to treating the host, or reinfestation is likely. Five percent carbaryl dust may be effective, in addition to spraying the infested herps with an ivermectin spray. Pyrethrin sprays may also be effective. Please note that ivermectin should not be used in turtles and tortoises, as a fatal reaction may occur.
Turtles and tortoises suffering from hypovitaminosis A may present with swollen, edematous palpebra, and often have accompanying hyperkeratosis of the skin and mouth parts. Treatment consists of parenteral injections of vitamin A (2000 IU/kg IM every 3 days for two weeks, then once per week for two more weeks, in severe cases.
Unfortunately, thermal burns are still commonly encountered from "hot rocks," herps that have access to lightbulbs or overly hot heating pads. These burns usually result in large areas of necrotizing dermatitis. Often, large skin sloughs occur, and the herp often develops systemic bacterial infections. These wounds should be managed in a manner similar to that for bite wounds.
Vesicular dermatitis, commonly caused blister disease, is commonly observed in snakes and lizard housed in moist, dirty cages with too high of an ambient humidity. Initially, it presents as fluid-filled blisters. Left untreated, septicemia often results. This disease should be treated aggressively with systemic antibiotic therapy based on individual culture and sensitivity results. However, the herp's environment must be corrected to prevent reoccurrence. The cage must be kept dry and well ventilated to successfully manage this disease.
Other bacterial, traumatic and environmental problems may result in dermatological disease in herps, which are beyond the scope of this manuscript.
As a veterinarian, diagnosing and treating skin and feather disease in exotic animals requires the same basic skills that you learned in vet school for treating companion animals. And, of course, having colleagues that you can discuss cases with, attending exotic animal continuing education courses and having a good exotic animal pathologist to send diagnostic samples to will greatly help you in working with exotics.
Copyright © 2006 Margaret A. Wissman, D.V.M., D.A.B.V.P.
All Rights Reserved
Printer Friendly Page