Hedgehog zoonoses

Emerging Infectious Diseases,  Jan, 2005  by Patricia Y. Riley,  Bruno B. Chomel

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Exotic pets, including hedgehogs, have become popular in recent years among pet owners, especially in North America. Such animals can carry and introduce zoonotic agents, a fact well illustrated by the recent outbreak of monkeypox in pet prairie dogs. We reviewed known and potential zoonotic diseases that could be carried and transmitted by pet hedgehogs or by wild-caught hedgehogs that have been rescued.

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Pets play an important role in societies throughout the world (1). They are important companions in many households, contributing to the physical, social and emotional development of children and the well-being of their owners, especially the elderly (1). Although pets offer significant benefits, potential hazards are associated with pet ownership (1). Exotic animals are increasingly being invited into homes as pets (2). However, neither pet owners nor nonveterinary healthcare providers are sufficiently knowledgeable about the potential of many of these animals to transmit zoonotic diseases (2).

Hedgehogs are small, nocturnal, spiny-coated insectivores that have been gaining popularity as exotic pets (3). These animals are considered to be unique, low-maintenance pets (4), and an estimated 40,000 households in the United States now own them (5). These animals originally arrived from Europe, Asia, and Africa, and although several species exist, 2 in particular are commonly seen as pets (3): the European hedgehog, Erinaceus europaeus, and the smaller African pygmy hedgehog, Atelerix albiventris (3). The importation of these pets from Africa to the United States has been prohibited since 1991 (Title 9 Code of Federal Regulations Section 93.701) due to their potential to carry foot-and-mouth disease, a foreign animal disease of serious economic concern to the livestock industry (6). In the United States, persons who sell hedgehogs are required to have a U.S. Department of Agriculture (USDA) license (http://www.nal.usda.gov/awic/newsletters/v9n1/ 9n1aphis.htm). In some states, such as Arizona, California (http://www.dfg.ca.gov/licensing/pdffiles/fg1518.pdf), Georgia, Hawaii, Maine, Pennsylvania, Vermont, and Washington D.C., owning a hedgehog as a pet is illegal (www.hedgehogwelfare.org), as is the case in some of New York City boroughs (Manhattan, Brooklyn, Queens, Bronx, Staten Island) (source: http://www.petfinder.org/ shelters/CT171.html).

Hedgehogs live in a variety of habitats where they dig their own burrows, spend most of the daylight hours asleep, and emerge at night to forage (3). Hedgehogs are characterized by short, grooved spines covering the entire dorsum of the body (3). When frightened by an unfamiliar sound or movement, the animal rolls into a tight ball (3). In this defensive posture, the hedgehog brings its snout and limbs close under its body, causing the spines to become erect (3). The spines, modified hairs having a spongy matrix and outer keratinous shaft (7), are not barbed (8). The spines rarely cause serious injury to handlers (8) but can readily penetrate the skin (7). However, 1 report described 3 patients in whom an acute, transient, urticarial reaction developed after contact with the extended spines of pet hedgehogs (7).

Hedgehogs display an unusual behavior called "anting" or "anointing" (7). When first encountering a new or interesting object or food, the animal will lick the substance repeatedly until a frothy saliva forms in its mouth (3). The animal then rubs the excess saliva and froth onto its skin and spines (3). This behavior may cause saliva to accumulate on the spines, making the hedgehog less palatable to predators (7).

In addition to the contact urticaria that has been reported in some hedgehog handlers (7), hedgehogs pose a risk for a number of potential zoonotic diseases (2). Major microbial infections associated with hedgehogs include bacteria such as Salmonella and Mycobacteria, as well as some fungal and viral diseases (2). Many disease conditions can cause immunodeficiency in humans; the most notable is ADS (9). Similarly, immunosuppressive strategies employed to prevent rejection of bone marrow or solid organ transplants render such patients extremely susceptible to viral and mycobactcrial infections (9). An increasing percentage of the population is becoming susceptible to severe diseases associated with exotic pet ownership, as illustrated by the recent monkeypox outbreak in pet prairie dogs (10). Immunocompromised persons may be at increased risk for infections from hedgehogs and should be particularly careful.

The following review focuses on the zoonotic or potentially zoonotic agents carried by hedgehogs (Table). The risks are particularly of concern for people rescuing wild-caught hedgehogs and adopting them as pets. We distinguished major established zoonotic infections, such as salmonellosis or ringworm, from other less common or potential zoonoses carried by hedgehogs.

Bacterial Zoonoses

Salmonellosis is the main zoonotic disease associated with hedgehogs, as well as several other exotic pet species (4). Although affected hedgehogs can display anorexia, diarrhea, and weight loss, [approximately equal to] 28% of hedgehogs are asymptomatic carriers (11). Several recent reports have shown that hedgehogs play a major role in the transmission of Salmonella Tilene, a rarely encountered serotype of humans (4,6,12). In 1994, Salmonella serotype Tilene infection was diagnosed in a 10-month-old girl in the state of Washington (6). The source of the organism was traced back to African pygmy hedgehogs raised by the child's family. Although the infant had no direct contact with the hedgehogs, the animals were handled frequently by 1 member of the family. Cultures from the child's asymptomatic parents were negative, and the breeding herd of 80 hedgehogs was apparently healthy, but a stool sample from 1 of 3 hedgehogs yielded S. Tilene. A second S. Tilene case was reported later that year from Texas (6). That patient's family also owned a hedgehog.