Straelensiosis in dogs: a newly described nodular dermatitis induced by Straelensia cynotis

Abstract

A distinctive nodular dermatitis induced by Straelensia cynotis, a newly described trombidioid larval mite which resides in hair follicles, was identified in 12 dogs living in France. They all had scattered, small (1 to 3 mm in diameter), pale, firm skin nodules, variable in distribution but always affecting the dorsal regions of the head and trunk; they were distributed over the whole body of seven of the dogs. The animals were otherwise healthy except for three severely infested fox terriers which had a decreased appetite, were lethargic, and whose skin nodules were painful to the touch. The nodules did not induce pruritus. The lesions usually began as erythematous papules which developed into firm pale nodules. The dermatitis resolved within two to 12 months. Topical acaricides were ineffective but the skin nodules regressed after treatments with systemic avermectins. Histologically, each nodule was composed of a dilated follicular ostium containing a well-preserved larval mite, and showed a pseudoepitheliomatous follicular hyperplasia and an abundant perifollicular mucinosis. The larvae were identified as belonging to the genus Straelensia (Acari: Leeuwenhoekiidae). It was clearly established that the three fox terriers had become infested within a fox's den. The nymphs and adults of this species of mite are believed to live in foxes' dens; foxes are considered to be the natural host for the larval stage, and dogs a permissive but occasional host.

Straelensiosis in two cats and ten dogs from Israel

“…The present 12 cases, diagnosed in Israel, occurred mostly in mountainous areas in Israel, in which ambient temperatures are cooler. All affected pets were free to roam the environment, in agreement with previous reports, which documented straelensiosis in rural and hunting dogs (Le Net et al 2002, Ramirez et al 2009).…”

“…The high frequency of marked pruritus in the present cases is interesting, and was often the chief complaint at presentation, in contrast to several previous reports (Le Net et al 2002, Degorce-Rubiales et al 2008, Ramirez et al 2009). These concluded that (Ramirez et al 2009).…”

“…In one dog (case 1) there was a blood-filled mass, consisting of irregular squamous epithelial cells, with neovascularisation in the surrounding tissue. The combination of these histopathological features is highly characteristic of straelensiosis, and was described only in such cases (Le Net et al 2002, Ramirez et al 2009).…”

“…While the nymphs and adults are either free-living scavengers or parasitise plants or are predators of other arthropods, the larvae (also known as "chigger mites" or "harvest mites") are parasitic in mammals, birds and reptiles (Kettle 1984, Takashi et al 2004, Yager et al 2007. In contrast with most trombidioid infections, where larvae attach to the epidermis (Le Net et al 2002, Yager et al 2007, Miller et al 2013, S. cynotis larvae are found in hair follicles (Fain & Le Net 2000, P. Bourdeau, unpublished data).…”

“…Straelensia cynotis was shown to cause a distinctive nodular dermatitis in hunting and outdoors dogs in France, Portugal and Spain (Fain & Le Net 2000, Le Net et al 2002, Seixas et al 2006, Ramirez et al 2009. The biology and life cycle of this newly-recognised parasite is currently unknown, but the dogs' lifestyle seemingly has a major role in this accidental infection, as the disease occurs in rural and hunting dogs (Le Net et al 2002, Ramirez et al 2009). The parasite is present deep in hair follicles and shows a pathognomonic his-a typical brown-yellow colour and a relatively elongated opisthosoma.…”