Demodex injai is a species of parasitic mite of the Demodex genus that infests hair follicles of mammals of the Canis genus. In veterinary medicine, the species has been the subject of study due to being one of the primary parasites known to cause red mange, a common skin disease among domestic dogs.
D. injai was first described in the 1990s, and was assumed to be a subspecies of D. canis.[1] In 2003, it was proposed by Clifford Desch and Andrew Hillier that D. injai was a separate species.[1] This classification was based solely on morphology and conjecture until genetic sequencing in 2012 confirmed that D. injai was a fully distinct species.[2]
Description
D. injai is a long-bodied Demodex mite.[3] The species is the largest Demodex mite found in carnivores.[4] The general appearance of D. injai can be described as worm-like.[4] Consistent with other species in its family and genus, D. injai has a small, thin, usually elongated body, with four pairs of legs. The body plan of the mite consists of three distinct sections; the gnathosoma, podosoma, and opisthosoma.[1] The gnathosoma is trapezoidal in shape with distinguishing doubled-tined spinal growths.[1] The spacing of legs along the podosoma is typical, and the legs are "wedge-shaped" with spurred claws; another spur is present at the legs midpoint.[1] The ventral opening towards the back of the opisthosoma is flared, and has the reproductive organs extending outside of this opening in the form of a narrow tube.[1] The reproductive organs are visually identical between the two sexes.[5] The opithosoma of D. injai is significantly longer and wider than similar species.[6]
Larva of the species are six-legged, and eventually develop into eight legged nymphs after several molts. The adults have eight legs.[7]
A study of Polish specimens in 2008 concluded that males of the species ranged from 309 to 411 µm in length, and females ranged from 282 to 396 µm long.[8] These lengths are three times longer than the closely related Demodex cornei and Demodex canis, which are also known to infest dogs and serve a similar ecological niche.[4]
D. injai is morphologically adjacent to other canine-infesting Demodex mites; but is also similar to Demodex mites inhabiting non canine species. D. injai is extremely similar to the goat inhabiting Demodex caprae, which is only distinguished by slight genetic differences and its host animal.[9] The species is also comparable in form and general behavior to feline-infesting mites such as Demodex gatoi and Demodex murilegi.[10] In general, D. injai is comparable to Demodex mites living on ungulates and bats.[6]
D. injai is a parasitic mite living inside the hair follicles of canines.[1] Despite the species being most common in domestic canines,[1] infestations of the species are also known to occur in wild canines; primarily the Golden Jackal.[4] The species is rarely ever found alone, and is almost always found among other related species of hair follicle parasites.[11] Notably, the species appears to completely avoid Sarcoptes scabiei, as the species has never been observed simultaneously using the same dog as a host.[12] Though the species is only confirmed to live in dermal tissue, an unclassified mite from venezuela theorized to be a subspecies of D. injai is present on the outer sections of the skin.[13]
Development from egg to adult occurs over the course of a cycle lasting approximately 20 to 35 days. The cycle occurs in its entirety within the glands infested by the mite.[7]
A dog suffering from a severe instance of demodicosis.
The species is known to cause demodicosis, also known as red mange or demodectic mange, following intense proliferation into the pilosebaceous glands which host the mite.[4] Demodicosis is characterized by a folliculitis, furunculosis, erythema, hyperpigmentation, alopecia, comedones, and a distinct unpleasant odor.[4] While sarcoptic mange similarly involves the a harmful infestation of parasitic mites, infestations of D. injai and other Demodex mites differ in that they are not considered contagious and also tend to be of greater severity.[14] Historically, submerging a dog in motor oil was a common pseudoscientific treatment for demodicosis; however this practice risks kidney and liver damage to the dog being bathed, while also failing to prevent mange,[15] and is discouraged by veterinarians.[16]
The related species, Demodex canis, is the primary cause of demodectic mange in canines.[17] Demodicosis primarily driven by an infestation of D. injai differs significantly from the most prevalent form of demodicosis. D. injai is observed to infest older adults in a manner uncommonly seen with most instances of demodicosis.[18] Infestations of D. injai are also distinguished by the presence of additional symptoms not typically associated with Demodicosis. These include extremely greasy fur due to seborrhea, ulcers, hematic crusts, and long-term bleeding.[18][19] In some cases, seborrhea induced keratosis had fully adhered to the skin and fur.[18]D. injai caused demodicosis is more frequently comorbid with other skin conditions, such as atopic dermatitis.[18] Despite these differences, infestations of D. injai can be treated the same as any other instance of demodicosis.[18]
Unlike other canine-infesting Demodex species, D. injai is observed to have a preference for specific breeds of dog; among specimens collected from domestic dogs, the species is particularly common among terriers.[20] The association between D. injai and terriers has been observed since the earliest documentation of the mite.[21] In terriers, the mite's presence is often localized in the dorsal trunk of the dog's body.[21]
↑Zhao, Y. E.; Hu, L.; Ma, J. X. (1 September 2013). "Phylogenetic analysis of Demodex caprae based on mitochondrial 16S rDNA sequence". Parasitology Research. 112 (11): 3969–3977. doi:10.1007/s00436-013-3586-x. PMID23996126.
↑Izdebska, J. N. (June 2023). "Demodex murilegi and Demodex obliquus, two new specific skin mites from domestic cat Felis catus, with notes on parasitism". Medical and Veterinary Entomology. 37 (2): 263–274. doi:10.1111/mve.12628. PMID36461721.
↑Alvarez, L. (2007). "First report of an unclassified Demodex mite causing demodicosis in a Venezuelan dog". Annals of Tropical Medicine & Parasitology. 101 (6): 529–532. doi:10.1179/136485907X193888. PMID17716436.
↑Brooks, Wendy (8 August 2017). "Demodectic Mange in Dogs". Veterinary Partner. Archived from the original on 23 November 2025. Retrieved 7 February 2026.
↑Mason, K. V. (1993). A new species of Demodex mite with D. canis causing canine demodicosis: a case report. Ninth Proceedings, Annual Members Meeting of American Academy of Veterinary Dermatology and American College of Veterinary Dermatology. San Diego. p.92.
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