Diseases and treatment of pet hedgehogs (Proceedings)

Hedgehogs are members of the family Erinaceidae in the order Insectivora. There are 16 species of hedgehogs; however, the most common pet species in North America is the African pygmy hedgehog (also referred to as the white-bellied, four-toed, or African hedgehog) (Atelerix albiventris). Average life expectancy in the wild is 1-1.5 years; in captivity, they generally live 3-5 years (but 6-10 years has been recorded).

Although hedgehogs are nocturnal, they will emerge from their nests during the day. Unfamiliar sounds or movements will often cause a hedgehog to assume its defensive posture. Contraction of longitudinal muscles along the thorax and abdomen act as a "purse string" and help the animal to roll into a tight ball. The snout and limbs are tucked close under the body and the spines are erected. Frightened hedgehogs may "puff up", spit, and/or emit high-pitched hissing sounds. An unusual behavior of the hedgehog is that of self-anointing (also called "anting"), an activity often elicited by the introduction of an unfamiliar object. They will lick the new object repeatedly, hypersalivate, create a frothy saliva, and then rub the saliva on to their skin and spines. Although African hedgehogs are bred commercially for the pet trade, their behavior remains that of non-domesticated animals. In addition to being nocturnal, many individuals do not interact with humans regardless of how much handling they received when they were young. However, they are cute, unique, and inquisitive pets, and generally do not bite. This presentation will review the captive management, common diseases, and medicine of the African hedgehog.

Restraint

The degree of physical and chemical restraint necessary for adequate examination of hedgehogs is highly variable and often depends on the degree of handling that is performed by the owner. Although some hedgehogs do not resist physical manipulation and can be easily examined, thorough physical examination can be problematic. The use of light leather gloves is generally recommended because they help prevent injury from the sharp spines and allow for adequate control of the animal. If a gloved hand is slipped underneath the body, some hedgehogs will eventually relax and unroll enough to permit physical examination; similar results may sometimes be obtained by heavy backward stroking over the rump. Scruffing the animal before it rolls up may also allow for a brief examination. However, without sedation or anesthesia, adequate physical examination is often difficult to impossible as many hedgehogs either refuse to unroll, or once unrolled, are resistant to physical manipulation. Therefore, to facilitate examination, hedgehogs are frequently sedated or anesthetized using an induction chamber or small face mask using an inhalant anesthetic agent. Isoflurane is the inhalant agent of choice. Once induced, the hedgehog can be maintained via face mask or endotracheal intubation.

Venipuncture

Venous blood is most easily collected from superficial veins: the lateral saphenous vein may be visualized below the stifle; and the cephalic vein can be found along the dorsum of the foreleg. If volumes greater than 0.5 ml are required, the jugular vein, while not readily visible or palpable, can be most easily accessed by lying an anesthetized animal on its back, gently holding the vessel off at the thoracic inlet, and inserting a needle at the same anatomic position that one would expect for a dog or cat. The cranial vena cava can also be used to collect a blood sample, but there is a greater risk of cardiac puncture due to the relatively cranial position of the hedgehog heart. Small length (0.5") and gauge (25 or 27 ga) needles should be used for hedgehog venipuncture, and sedation or anesthesia is almost always required for safe and reliable access.

Medical conditions

Obesity is a common problem in adult hedgehogs and may lead to inactivity, metabolic derangements, and health problems. Some animals, if allowed, will become so obese that they can no longer fully "roll up". Such animals should be placed on a slowly decreasing quantity of food (with a reduction of calories and fat) and should be encouraged to be more active.

In addition to obesity, a variety of diseases have been noted in captive hedgehogs. Gastrointestinal diseases include stomatitis, esophagitis, gastritis, enteritis, colitis, fatty liver disease, gastrointestinal neoplasia, and pyloric or intestinal obstructions (most often caused by rubber, hair, or carpet fibers). Fractured and abscessed teeth are common causes of weight loss, anorexia, and increased salivation. Radiography is often helpful in diagnosis; extraction of the affected teeth, with administration of systemic antibiotics, is often curative. Periodontitis is a common condition in adult hedgehogs and may be treated with traditional therapy. Also, oral neoplasms, particularly squamous cell carcinomas, are relatively common.

Hedgehogs seem to be prone to corneal ulcers and other ocular injuries. Diagnosis and treatment is as for other species; however, treatment may be difficult in cases where owners are unable to administer topical medication. Blind hedgehogs seem to navigate their captive environments with minimal detriment to their quality of life. Ocular proptosis was a relatively common presenting complaint in one report. The ocular sequela to proptosis was severe, and resulted in enucleation or euthanasia in all eight cases. Hedgehogs have a shallow orbit that may predispose them to proptosis, especially if excessive fat accumulation or orbital inflammation is present. In hedgehogs with a unilateral proptosis, tarsorrhaphy may be indicated as a prophylactic measure for the remaining eye.

Some respiratory pathogens have included Bordetella bronchiseptica and Pasteurella multocida. Clinical signs may include dyspnea, nasal discharge, and/or sneezing. Predisposing factors for upper and lower respiratory tract infection include sub-optimal environmental temperature, dusty or unsanitary bedding, malnutrition, concurrent disease and other causes of immunocompromise. Signs include nasal discharge, increased respiratory noise, dyspnea, lethargy, inappetence, and sudden death. As in other species, diagnostic testing includes radiographs, hematologic testing, and culture of tracheal or lung lobe aspirates. Treatment should include broad-spectrum antibiotics, supportive fluids, oxygen therapy, and nebulization as needed, and correction of husbandry problems. Trimethoprim-sulfa, enrofloxacin, and oxytetracycline are all good empirical choices for antibiotic therapy.

Dilated cardiomyopathy is common in pet hedgehogs, and necropsy findings from several cases have been described. Affected hedgehogs are typically greater than 3 years or older, although the disease may occur in animals as young as 1 year of age. Signs include dyspnea, decreased activity and weight loss, a heart murmur, ascites, and acute death. Radiographs typically demonstrate varying degrees of cardiac enlargement, pulmonary edema, pleural effusion, hepatic congestion, and abdominal fluid. The etiology of cardiomyopathy in hedgehogs is not known, but there may be a genetic or dietary component. When cardiac disease is suspected, full body radiographs and an echocardiogram should be obtained. Normal echocardiographic measurements have not been published, but a subjective evaluation of wall motion and chamber size is often sufficient to confirm a diagnosis of cardiomyopathy. A CBC and biochemical profile are useful to screen for concurrent problems and to serve as a reference to monitor effects of therapeutic agents. Therapy with digoxin, furosemide, and enalapril may be helpful initially, but the long term prognosis for hedgehogs in congestive heart failure is poor.

Trauma is another common finding in hedgehogs. Traumatic wounds are frequent sequelae to wire-floored cages. Wounds may also be caused by male-male or interspecific interactions. Culture and sensitivity of wounds should be performed where appropriate, and systemic and/or topical antibiotics should be administered. Hedgehogs tolerate a variety of splints and bandages very well, although anesthesia is usually required for application. Soaking the affected limb in topical disinfectants (i.e. dilute chlorhexidine) can be a very safe and effective adjunct therapy.

Hedgehogs, like many exotic animals, will often hide signs of illness. Currently there are no vaccines for pet hedgehogs.

Neoplasia

Neoplasias in African hedgehogs are common, and a wide variety of tumors and disseminated neoplastic processes affecting virtually every body system has been reported. In one retrospective study of 74 necropsies, neoplasms were diagnosed in 24 animals (32%); tumors were present in 40% of animals between 1-36 months and in 69% of animals over 3 years of age.

In a subsequent survey of 97 hedgehogs, 50 animals (52%) had neoplastic diseases. The body systems in which the tumors were found were: integumentary (18 tumors), hemolymphatic (12 tumors), alimentary (9 tumors), endocrine (8 tumors), genital (6 tumors), musculoskeletal (2 tumors), and nervous (1 tumor). The most commonly diagnosed tumors in this survey were: mammary gland tumor (9), lymphosarcoma (8), and oral squamous cell carcinoma (7). Four (8%) of the 50 animals had more than one type of tumor. The occurrence of tumors was unrelated to gender, and the median age at time of tumor diagnosis was 3.5 years (range 2-5.5 years). In the majority of cases, the neoplasms were malignant and usually carried a poor prognosis.

In retrospective studies of hedgehogs at necropsy, the prevalence of neoplasia has ranged from 29% to 51.5%. Numerous neoplasms have been reported in the hedgehog and include: squamous cell carcinomas (especially of skin, maxillary, oronasal area); cutaneous mast cell tumors; mammary gland tumors; cutaneous hemangiosarcoma; alimentary lymphosarcomas and plasmacytoma; a pancreatic exocrine carcinoma; endocrine tumors (including a pancreatic islet cell tumor, thyroid tumors, adrenal tumor, a pituitary adenoma, and a parathyroid tumor); gastric adenocarcinoma; spindle cell sarcomas; myelogenous leukemia; osteosarcomas; fibrosarcomas; cutaneous histiocytic sarcoma; malignant fibrous histiocytoma; nerve cell tumors (peripheral nerve sheath tumor, astrocytoma, neurofibroma, neurofibrosarcoma, and schwannoma); and wide variety of tumors of the reproductive system (including uterine leiomyoma, leiomyosarcoma, and adenocarcinoma). Certain types of sarcomas in hedgehogs have been associated with retroviral infection.

In addition to the general presence of masses, clinical signs of neoplasias may include chronic weight loss, anorexia, lethargy, diarrhea, dyspnea, and ascites. Cases of oral squamous cell carcinoma usually present as swelling of the maxillary or mandibular gingiva. Hedgehogs with oral squamous cell carcinomas are generally presented with loose teeth, swollen gingiva, and/or gingivitis. This tumor appears to be generally locally infiltrative.

Diagnosis of neoplasia is based on biopsy (needle, incisional, or excisional) or necropsy and histopathology. Radiographs for evidence of invasion or metastasis, a CBC and serum chemistry panel, and abdominal ultrasound may be useful in determining a long term prognosis. Treatment generally includes surgical excision. Prognosis and management depends on type and stage of the neoplastic process.

Hepatic lipidosis

Hepatic lipidosis is frequently a diet-related illness that is relatively common in hedgehogs. In one survey to identify common necropsy and histopathologic findings in 14 hedgehog cases, hepatic lipidosis was found in 50% of the animals. Causes of hepatic lipidosis include diet, starvation, obesity, toxicosis, and pregnancy, and can be a sequela to infectious or neoplastic disease. Hepatic lipidosis is the end result of disruption of normal lipoprotein synthesis and continual triglyceride synthesis within hepatocytes. In the aforementioned survey, 57% of hedgehogs with hepatic lipidosis had concurrent infectious or neoplastic disease which may have depleted ATP stores in the liver and/or caused decreased food consumption that may have resulted in depletion of hepatocellular stores of glycogen.

Ectoparasites

Hedgehogs are also susceptible to external parasites, especially acariasis. Mite infestations (i.e., most commonly Caparinia tripolis) are very common. Some hedgehogs may have sub-clinical infestations, which may account for the high prevalence of mites in the pet population. Infested bedding or fomites from pet stores may be another source. Signs include seborrhea, quill loss, and white or brownish crusts (mite droppings) at the base of the quills and around the eyes. Hedgehogs can scratch themselves with their hindlimbs or rub against stationary objects, but many individuals do not demonstrate obvious signs of pruritus. Ascariasis also causes non-specific signs such as lethargy and decreased appetite. Direct examination and routine skin scrapings with microscopic examination may be used for diagnosis. Ivermectin (0.2-0.4 mg/kg SC) treatment is usually effective if dosed at 7-14 days intervals for 3-5 treatments. Application of 1% permethrin has also been shown to be effective for mite infections. Amitraz (Mitaban®, Upjohn) dips and rinses (0.3%) administered at weekly intervals for 2-3 treatments have also been used safely and effectively in cases of acariasis. In addition, all bedding is removed, and cage furnishings are disinfected or thrown away. During the treatment period, the cage is lined with paper that is changed daily. Although uncommon, fleas and ticks may be observed on hedgehogs, and may be treated using flea powders that are safe for kittens.

Dermatophytosis

Although acariasis is the most common dermatopathy, dermatophytes (usually Trichophyton spp., but also Microsporum spp.) also cause dermatitis in hedgehogs. Dermatophytes usually cause a crusting dermatitis, especially around the face and pinna. Pruritis is generally not a feature of this condition. Diagnosis is confirmed by fungal culture. Treatment consists of topical antifungals with systemic antifungals as needed. Lyme sulfur dips and griseofulvin may also be used. Several cases of Trichophyton infections in humans have originated from contact with infected hedgehogs.

Wobbly Hedgehog Syndrome (Demyelinating Paralysis)

Since the mid 1990's, there has been an increasing number of cases of wobbly hedgehog syndrome (WHS) (also referred to as demyelinating paralysis) reported in African hedgehogs in the United States, a condition that has been previously described in European hedgehogs. Clinical signs of WHS begin with mild ataxia, progress to more severe neurologic signs, and ultimately lead to complete paralysis. Other clinical signs include significant weight loss, dysphagia in late disease, falling to one side, ascending paralysis, and tremors. The onset of WHS commonly occurs under 2 years of age, but can occur at any age. Progression rate is variable, and the majority of hedgehogs are completely paralyzed by 15 months after the onset of clinical signs. Death usually occurs within 18-25 months after the onset of signs. The diagnosis can only be determined postmortem. Gross lesions are not evident, but histopathologic lesions reveal a vacuolization of the white matter of the brain and spinal cord, and associated neurogenic muscle atrophy. There is no inflammation of the central nervous system associated with WHS. To date, there has been no histologic evidence of a viral or autoimmune cause. The etiology for this syndrome is unknown, but pedigree analyses from numerous animals suggest a familiar tendency to the disease. Numerous treatments for WHS have been attempted with little or no success; none have stopped the progression of the paralysis.

Zoonoses

Several strains of Salmonella occur in hedgehogs, and cases of transmission from pet African hedgehogs to humans have been documented. As with reptiles, it should be assumed that all pet hedgehogs can carry and transmit this pathogen, and animals should be handled accordingly (wash hands afterwards, do not allow animals or fomites to contact food or food preparation areas, etc.). Subclinically infected animals may shed intermittently, so cultures should not be used to rule out the carrier state. Treatment aimed at eliminating the carrier state is unlikely to be successful and should not be attempted, as resistance may result. Several cases of human dermatophytosis from pet hedgehogs have been documented. In addition, some people may be extremely sensitive to contact with African hedgehog spines and develop a transient but markedly pruritic urticaria within minutes of handling a hedgehog. People with cat allergies may be predisposed to this sensitivity.

References

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