Date Published: September 10, 2007
Publisher: BioMed Central
Author(s): Gete Hestvik, Monika Zahler-Rinder, Dolores Gavier-Widén, Ronny Lindberg, Roland Mattsson, David Morrison, Set Bornstein.
During the past decade, Chorioptes mites occupying the outer ear canals have been a common finding at routine necropsies of moose (Alces alces) in Sweden, but neither the taxonomy of the mites nor lesions from the infestation have been investigated. In this study, the mites are characterized by morphological and molecular techniques, and the histopathology of the skin of the outer ear canal is described.
External auditory meatuses from 53 necropsied moose were examined for the presence of Chorioptes, and samples from outer ear canals were taken for histopathological and microbiological examination. A proportion of the mites from each moose was identified to species. The DNA was extracted from mites from three moose, and their ITS-2 sequences were determined; these sequences were compared phylogenetically to sequences from other Chorioptes taxa.
Chorioptes mites were found in 43 (81%) of the 53 moose. The mites had morphological and genetic characteristics distinct from those of C. texanus and C. bovis, the two species generally accepted within the genus. Morphology also did not argue for a diagnosis as C. crewei, C. mydaus or C. panda. On histopathology, lesions were characterized by a hyperplastic perivascular to interstitial dermatitis with epidermal hyperkeratosis and crust formation. Dermal inflammatory infiltrates were composed of mixed T- and B-lymphocytes, plasma cells and macrophages, whereas eosinophils were notably uncommon. Staphylococcus aureus was grown from the infested epidermis of five of 14 examined moose.
Chorioptes mite infestation was frequently detected in the outer ear canals of moose in Sweden. The mites were evidently pathogenic, being associated with inflammatory lesions of the external auditory meatus. Our studies indicate infestations with a previously undescribed Chorioptes species.
Ectoparasites of the genus Chorioptes (Acari: Psoroptidae) are distributed worldwide, infesting domestic as well as wild herbivores [1,2]. These non-burrowing mites are commonly found on cattle, sheep, goats, horses and the New World camelids, where they are a common cause of mange and have considerable veterinary importance. The affected skin areas vary with host and degree of infestation, but the extremities or tail regions are commonly involved. The entire life cycle, from egg-laying through larval and nymphal stages to mature mites, takes place on the same host, and spans approximately three weeks .
Infested moose were found in all parts of the study area, covering the mid and south regions of Sweden. Of the 53 moose examined parasitologically, 43 (81%) were infested with Chorioptes sp. Five of those only had one ear infested. The degree of infestation was scored in 32 moose, in 7 it was low, in 8 mild, in 11 moderate and in 6 moose it was high. Twenty-eight moose had similar degrees of infestation in both ears, while in two moose the degree of infestation between ears varied, and two had only one ear infested.
This study showed that Chorioptes sp. was frequently detected in the outer ear canals of moose (Alces alces) in Sweden. In wildlife, localization of Chorioptes mites in the outer ear canals has also been described in reindeer, Rangifer tarandus , red-flanked duiker, Cephalophus rufilatus  and giant panda, Ailuropoda melanoleuca . In this study the skin of other parts of the body of the moose was not examined for mites and therefore it is not known if the Chorioptes infestation was restricted to the ear canals. Moreover, Chorioptes sp. have been found on alopecic areas of the skin in moose necropsied at SVA, and in one case Chorioptes were also demonstrated in the outer ear canals (pers. comm. C. Bröjer). However, these mites have not yet been closely compared to the Chorioptes sp. isolated from the external ear canals of the moose of this study.
Chorioptes sp. was frequently detected in the outer ear canals of moose (Alces alces) in Sweden. This mite has morphological and genetic characteristics distinct from those of C. texanus and C. bovis, the two species generally accepted within the genus. Morphology also did not unequivocally argue for a diagnosis as C. crewei, C. mydaus or C. panda, and thus we argue that the mites belong to a proposed new species. The mites were obviously pathogenic to the moose, evoking epidermal and dermal inflammatory lesions, the latter indicating immunological hypersensitivity reactions.
The author(s) declare that they have no competing interests.
GH carried out the histopathological examinations, and wrote the first draft of the manuscript. MZR carried out the morphological and molecular studies, and wrote the first draft of the manuscript. DGW conducted the preliminary histopathology, collected samples, blocked the tissues and contributed to the manuscript. RL contributed to histopathological description and to the manuscript. RM carried out the bacteriological and mycological investigations. DM contributed to the data analyses, and revised and edited the manuscript. SB initiated and coordinated the study, collected the samples, carried out the parasitological investigations, and contributed to the manuscript. All authors read and approved the final manuscript.