Psoroptid mites of the genus Caparinia affect hedgehogs and a few other mammals causing skin disease. The mite passes all stages on the host and feeds on sloughed skin cells and epidermal debris, similar to Chorioptes species [1]. Among 5 species of the genus Caparinia that have previously been classified, 2 species are known to infest hedgehogs; C. tripilis and C. erinacei. Among them, C. tripilis shows higher pathogenicity than C. erinacei and may burrow into the skin of the head, ears, flanks, and inner sides of the legs where they form clusters [2,3]. It can cause irritation, dermatitis, and self-trauma due to pruritus which can lead to a secondary infection and the host may eventually die [1,4].

First reported in England in 1889 by Michael who found very active mites on the surface of hedgehogs and described "running up and down the spines of hedgehogs with great rapidity", the mite was introduced to New Zealand but received little attention until Brokie examined 100 hedgehogs from Wellington between 1954 and 1957 [4,5]. In relatively recent years, C. tripilis has also been introduced to New Mexico, United States, through breeding colonies of African hedgehogs for sale as pets [6]. So far, the mite has not been reported in Asia, possibly because the animal has neither been popular as pet nor has been considered as endangered species.

Although there has been a great increase in the population of hedgehogs as pets, limited studies on the ectoparasitic diseases of hedgehogs are available. We report in this paper an outbreak of dermatitis in hedgehogs caused by C. tripilis with description of keys for the identification of the Family Psoroptidae and the genus Caparinia.

In February 2010, dermatitis characterized by scale and self-trauma due to pruritus was recognized in a group of 22 four-toed hedgehogs (A. albiventris Wagner, 1841) from a local pet shop in Gwangju, Korea. Three of the hedgehogs were males and the rest were females with an average weight of 339.3 g. The mantle of the skin was flaking, and scales and crusts were present. Many hedgehogs were scratching themselves leading to self-elicited trauma (Fig. 1). Upon otoscopic examination, the ear canal contained numerous live mites along with crusted exudate and scabs. Two of the severely affected hedgehogs died of self-trauma and secondary bacterial infections. For parasitological examinations, skin scraping samples from severely affected areas of the skin were collected and preserved in 70% methanol. For morphological comparison, adult male mites of Otodectes cynotis and of Chorioptes texanus were obtained from naturally-infested dogs and a Holstein cow, respectively. Mites were mounted on slides using Downs' PVA solution [7].

The identification of the genus Caparinia was based on the key provided by Lawrence [8] and description by Fain [9]. Body length and width of 5 mites per each developmental stage were measured (Table 1; Fig. 2). Morphologically, pedicels of adult mites were short and unjointed. Tarsal caruncles were bell-shaped on all legs of male while they were absent on legs III and IV of females. There were 3 long setae on the third pair of legs in both sexes (Fig. 2G, I). Adult males had a posterior end of the abdomen with a trilobate projection on each side, each lobe with a long seta (Fig. 3A). Average length and width of adult males and females were 313.6×240.5 µm and 418.6×287.1 µm, respectively. Based on these morphological features, the mite was identified as the genus Caparinia.

In adult males, the posterior dorsal scutum was wider than its length (Fig. 4), and the quadrilateral space (Fig. 3A, double-sided arrow) of the abdomen of males was wider than its length. The side of the body was rounded. In adult females, a distinctive feature was that they had 3 long setae both on the third and fourth pairs of legs. Two pairs of long setae which were present at the posterior end of the body were well separated from the posterior margin (Fig. 2I). Long humeral seta of the dorsal surface was inserted in a small distinct oval scutum (Fig. 5, arrows). Based on these features, the species of the mite was identified as C. tripilis.

This study reports the first outbreak of C. tripilis infestation in a colony of African pygmy hedgehogs in Korea. The genus Caparinia belongs to the family Psoroptidae and is closely related to Chorioptes except for the presence of a caruncle on leg IV of female mites [10] and to Otodectes except for the presence of posterior lobate projections in male mites (Fig. 3B). Caparinia spp. infest hedgehogs and some other mammals, including the cape polecat, hyena and European fox leading to skin diseases. Two species which have been isolated from hedgehogs are C. tripilis and C. erinacei. Since this is the first report of caparinic mite infestation in Korea, identification keys for the family Psoroptidae and the genus Caparinia that have been modified from Lawrence [8], Fain [9], and Michael [5] are provided at the end of the discussion.

The genus Caparinia have been classified into 3 well-documented species; C. tripilis, C. erinacei, and C. ictonyctis. Two additional species, C. setifera (Mégnin, 1880) and C. vulpis (Mégnin, 1880), were mentioned by Lawrence [8] but his description was based only on females and were too brief to differentiate between these 2 species and C. tripilis. For this reason, the diagnostic key provided in this paper includes features of female mites of 5 species, while features of male mites of C. setifera and C. vulpis are not provided. The taxonomic status of C. tripilis and C. ictonyctis is based on the mophological characteristics of adult male mites which differ from C. erinacei by the number of lobes on each laminate projection on the posterior end of the body and the number of the setae attached on each lobe. Male mites of C. tripilis and C. ictonyctis have 3 paired posterior lobes, each equipped with a long seta, whereas C. erinacei has 2 paired lobes with a long seta on each lobe. The presence of posterior lobate projections is also an important feature when it is needed to be distinguished from the genus Otodectes which does not have these lobate projections (Fig. 3B). The posterior dorsal scutum is wider than its length in C. tripilis, whereas that in C. ictonyctis is longer than its width (Fig. 4). Furthermore, while the 2 posterior projections of males enclose a quadrilateral space which is as long as its width in C. ictonyctis and wider than its length in C. tripilis (Fig. 3A).

Features of adult female mites of C. tripilis are very similar to those of both C. ictonyctis and C. erinacei. Legs III and IV do not have a caruncle, which is a characteristic feature to distinguish from Chorioptes spp. Female mites have 3 long setae at the end of the third and fourth pairs of legs whereas male mites have those on only Leg III. On the other hand, Otodectes has 2 long setae at the end of Leg III. Two pairs of long setae were present at the posterior end of the body of adult females (Fig. 2I, black arrow). Furthermore, 1 of the distinctive features of C. tripilis females is that the insertion of posterior abdominal setae is well separated from the posterior margin. By contrast, both C. ictonyctis and C. erinacei had posterior abdominal setae inserted on the edge of the posterior margin [8,9].

The life cycle of C. tripilis includes an egg, larva, protonymph, deutonymph (including pubescent female), and either an adult male or an adult female. Two bosses are present on the surface of an egg and are on the same side of the cleavage (Fig. 2A, B, arrows). By means of suckers, the adult males and pubescent females form an attachment pair which is more or less permanent up until the time of emergence of the adult females from the deutonymphal exuviae (Fig. 2H). Except for the presence of a couple of copulatory tubercles at the posterior end of a pubescent female (female deutonymph, Fig. 2F, arrow head), egg, larvae, protonymph, and deutonymph stages of Caparinia do not show sexual dimorphism. Observations suggest that the complete life cycle encompass about 3 weeks [10].

C. tripilis may burrow into the skin of hedgehogs, and symptoms may include pruritus, hair loss, spine loss, deformation of the ears, and scaly, encrusted skin lesions, leading to secondary infections. Severely infected animals become feeble, lose weight, scratch the affected skin, and may abandon their normal nocturnal behavior to become active in the daytime [4]. C. erinacei, on the other hand, has low pathogenicity and does not form clusters on its hosts [3]. A sarcoptic mange mite, Notoedres muris, may also be found in mixed infestations with C. tripilis [11].

One of the most common pet breed of hedgehogs is the African pygmy hedgehog or 4-toed hedgehog (A. albiventris). It is smaller than the Western European hedgehog, has a white abdomen, and is characterized by lacking the first toe of the hind leg. The animal had previously been classified in the genus Erinaceus (Macdonald, 1986) like Western European hedgehogs, but recently it has been reclassified as part of the genus Atelerix (Wilson, 1993). Hedgehogs are becoming popular pet animals but relatively little research has been carried out on their ectoparasitic diseases. As previously stated, this is the first outbreak of C. tripilis in a colony of hedgehogs in Korea. Some identification key aspects regarding the morphological features of the Family Psoroptidae and the genus Caparinia are provided. The identification keys in this article are adapted from Lawrence [8], Fain [9], and Michael [5].