Hedgehogs are small mammals that belong to the order Insectivora. There are several genera and species that are found throughout the British Isles, Europe, and Asia and Africa. Hedgehogs are not native to North America. The African pygmy hedgehog (Atelerix albiventris) originated in the African savanna, and is now widely bred in North America for the pet industry. The European hedgehog (Erinaceus europaeus) is a larger species, native to England and Europe and protected by law in many areas.

The African hedgehog is small, nocturnal, and spiny-coated. They vary in color from brown to almost black with a white ventrum. The adult ranges in weight from 300-600 grams. Life expectancy averages 3-4 years in the wild but up to 10 years in captivity.

Anatomy & Physiology

Hedgehogs are characterized by the short, grooved white and brown spines that cover the dorsum of the body. The face and ventrum are covered with soft, light-colored fur. The hedgehog can assume a defensive posture by rolling up and erecting the spines to resemble a tight ball of sharp spines.

The dental formula is typical of insectivores and consists of 36 teeth: I 3/2; C 1/1; P 3/2; M 3/3. The teeth are small with sharp, pointed cusps. The first incisor is usually larger than the others. Hedgehogs have a simple stomach and no cecum.

Gender is easy to identify in hedgehogs. The male has a ventral prepuce located midway along the abdomen. The testes are usually intra-abdominal and are not easily palpated. The female has a vulva located close to the rectal opening. African hedgehogs breed year-round. The gestation period is 34-37 days. Litter size ranges from 1-7 with an average of 3-4 pups. The young are born blind with soft white spines. New brown spines appear in 2-3 days and the eyes open in 2-3 weeks. Weaning occurs at 4-6 weeks.

In their native habitat, a hedgehog will dig its burrow under logs, leaves, among rocks, or tree roots and sleep most of the day. They are solitary and nocturnal, emerging at dusk to forage for insects. When undisturbed, it moves with an unsteady, waddling gait but can run quickly. The hedgehog has a keen olfactory and auditory sense making it an adept hunter and forager. The European species will hibernate in the winter and the African species will aestivate in the hot, dry season. Hibernation is not essential and is not recommended for captive hedgehogs.

Housing & Diet

Hedgehogs are usually caged alone but can be housed in groups if given enough space. Hedgehogs are excellent climbers, so cages should be smooth-walled and high enough to prevent escapes. Wire flooring should be avoided due to the potential for toe and limb injury. Newspaper or wood shavings (pine or aspen) can be used as bedding, but it must be changed frequently. A sleeping area can be made from cardboard boxes, hollowed logs, wooden boxes, or plastic flowerpots and filled with hay or leaves.

The native diet consists of a variety of insects, occasional small vertebrates, and carrion. Captive pets can be fed a diet of soaked low-fat dog or cat chow, smaller amounts of mealworms or earthworms, and a small amount of chopped fruit and vegetables. Because of the calcium-phosphorus imbalance, a diet solely of insects must be avoided. Hedgehogs should be fed once daily in the evening. Captive hedgehogs have the tendency to become obese; early evening exercise should be encouraged.

Physical Examination & Restraint

Hedgehogs typically roll-up making a full physical examination impossible without sedation. Light leather gloves are recommended to protect against the sharp spines. Some individuals can be successfully scruffed behind the ears if caught before they ball up, however, the majority of hedgehogs will need to be sedated.

The preferred method of sedation is isoflurane gas. The hedgehog is initially placed in an induction chamber and then switched to a face mask for maintenance. Endotracheal intubation is nearly impossible. Conversely, injectable agents can be used. Ketamine as the sole agent or in combination with diazepam can be administered intramuscularly. Tiletamine/zolazepam combinations can also be used (see Table 1 for doses). Halothane and methoxyflurane are reportedly safe to use for short procedures, but the author prefers isoflurane for its rapid induction, recovery and safety.

Clinical Techniques

Most procedures require sedation to perform, from toenail clipping to radiographs and venipuncture. Simple treatments for hospitalized individuals can be done by subcutaneous or intramuscular injection along the dorsum but oral administration may only be possible with weak hedgehogs. Large volumes of replacement fluids can be given intraperitoneally or through intraosseous catheterization. Intravenous catheters are difficult to place. Venipuncture can be accomplished in the sedated hedgehog through the jugular vein or cranial vene cava.

Common Conditions And Diseases

There is a paucity of information in the literature regarding the diseases of pet African pygmy hedgehogs. The following list of conditions represents a review of the literature as well as the author's own clinical experience. The best approach to hedgehog medicine is to apply basic medical common sense and keep in mind that this is a wide open field and anything is possible!

Integumentary Disorders

Mycotic dermatitis is caused by Trichophyton and Microsporum in hedgehogs. Disease can be subclinical or is manifested by scales, crusts, and the loss of spines. Treatment with oral griseofulvin and lime sulfur dips weekly are helpful. Diagnosis is by fungal culture of affected skin and scales.

Mites are the most important parasitic disease of pet pygmy hedgehogs. Mite infestatation is thought to be from Caparina sp. and can be subclinical or can produce extensive disease. Acariasis can result in a severe dermatitis characterized by scales, flaking, crusts, and loss of spines in protracted cases. Pruritus can be severe. Diagnosis is through routine skin scrapes and microscopic examination. Treatment with ivermectin or acaricidal dips (amitraz) is effective. Ivermectin is effective in treatment if the environment is appropriately cleaned.

Cutaneous nodules or masses are seen in hedgehogs and should be carefully evaluated. Papillomas, abscesses, and neoplasias have been identified. Granulomatous subcutaneous nodules and lymphadenitis caused by Mycobacterium has been reported. Lymphosarcoma with peripheral lymphadenopathy is another differential. All lesions should be biopsied and cultured.

Gastrointestinal disorders

Dental disease can be seen in hedgehogs on a soft food diet. Periodontitis and gingivitis have been diagnosed in both free-ranging and captive individuals. Oral cavity food "foreign bodies" can occur with inappropriately sized food items (shelled peanuts, e.g.).

Other gastrointestinal disorders are inflammatory in nature and include stomatitis, esophagitis, enteritis, and colitis. Viral stomatitis with ulcerative tongue lesions caused by foot-and-mouth disease is recognized in hedgehogs. Cryptosporidiosis can be fatal in pygmy hedgehogs. There is a high incidence of neoplasia in the gastrointestinal tract of hedgehogs, especially the oral cavity. Hepatic lipidosis is a common finding on necropsy.

Non-infectious causes of diarrhea must also be considered. Malnutrition and sudden diet changes should be evaluated. Antibiotic use does not seem to be a factor in inducing diarrhea in the hedgehog.

Respiratory Disease

Bronchopneumonia and catarrhal rhinitis caused by Bordetella bronchiseptica occurs in hedgehogs. Other etiologies of respiratory disease include Pasteurella multocida, Corynebacterium, verminous pneumonia in wild-caught individuals, and neoplasia. Heart disease is an important differential; dilated cardiomyopathies can present in failure with effusion and dyspnea.

Respiratory disease may not be apparent until advanced stages of the disease. Full body radiographs are indicated in all cases of respiratory distress or chronic weight loss. Antibiotics to consider include enrofloxacin, trimethoprim/sulfa combinations, chloramphenicol, and the aminoglycosides.

Neoplasia

Neoplasias are very common in hedgehogs over 3 years of age. Squamous cell carcinoma of the oral cavity seems to be over-represented and lymphosarcoma of any body part. Any system can be affected (skin, reproductive tract, liver, lymph nodes e.g.) All lumps and bumps seen in the hedgehog should be considered suspect and excsional biopsy is recommended. Other clinical signs to consider includes chronic weight loss, dyspnea, anorexia, and ascites.

Recommended Reading

1.  Allen ME: The nutrition of insectivorous mammals. In Proceedings of the Annual Meeting of the American Association of Zoo Veterinarians, Oakland, CA 1992, pp 113-115

2.  Done LB, Dietze M, Crnafield M, et al: Necropsy lesions by body systems in African hedgehogs: Clues to clinical diagnosis. In Proceedings of the Annual Meeting of the American Association of Zoo Veterinarians, Oakland, CA 1992, pp 110-112

3.  Hoefer HL: Hedgehogs. In Vet Clin North Am Sm Anim Pract 24 (1) pp 113-120, 1994

4.  Isenbugel E, Baumgartner R: Diseases of the Hedgehog. In Fowler, ME (ed): Zoo and Wild Animal Medicine, Current Therapy 3. WB Saunders, Philadelphia, 1993, pp 294-302.

5.  Reeve, N: Hedgehogs. T & AD Poyser, London 1997.