Infestivity of Demodex canis to Hamster Skin Engrafted onto SCID Mice

Abstract

ABSTRACT. We demonstrated that Demodex canis was transferred to skin xenografts of a dog and a hamster onto severe combined immunodeficiency mice. After the transfer of mites, the number of eggs, larvae, nymphs and adult mites per gram of canine and hamster xenografts increased, whereas no live mites were detected on murine allograft. These results indicate that D. canis proliferates in hair follicles of dog and hamster skins but not in murine allograft. Therefore, D. canis may have host preference but not strict host-specificity. [5,6,13]. These species from different hosts exhibit morphologic differences and they have been thought to be physiologically different and host specific. Cross infestivity of Demodex mites is important when immunosuppressive human patients keep a pet with demodicosis or when people need to keep their pet with other animals with the disease. However, the infestivity of Demodex mites has not been directly documented.A small number of Demodex mites are harmless residents of the skin of mammals [11,18]. Clinical disorders resulting in alopecia and erythema are known to be demodicosis associated with the presence of larger than normal numbers of Demodex mites [11,18]. The suggested predisposing factors of demodicosis include disorders of local defense responses of skin, suppression of cellular immunity, concurrent diseases et cetera. Differences in the virulence of Demodex strains have been considered but seem unlikely [18]. In some mammals including humans, the skin lesions of demodicosis are usually localized [11,15] and manifestation of generalized demodicosis has not been reported. The pathogenicity of Demodex species has remained controversial. Even under an immunosuppressive condition, the number of Demodex mites does not increase in humans [2]. In contrast, generalized demodicosis is frequently detected in dogs [18] and hamsters [19], indicating the relationship with immunodeficiency.Genetically immunodeficient mice have been used as a xenograft model as they fail to reject skin grafts. The absence of a functioning immune system allows xenogenic transplantation into severe combined immunodeficiency (SCID) mice without major graft rejection. Recently, Caswell et al. [4] succeeded in infecting D. canis on canine skin engrafted onto a SCID mouse. This mouse canine skin model would be useful for studying the biology of D. canis. They suggested host specificity of D. canis because they failed to infect murine skin with D. canis. However, demodicosis has been rarely reported in mice, and thus the host specificity of D. canis needs to be tested by using animals such as the hamster for which naturally occurring generalized demodicosis has been well recognized [19]. The purpose of the present study was to evaluate the infestivity of Demodex canis to hamster skin engrafted onto SCID mice.Clinically normal beagle dogs and hamsters (Djungarian hamster; Phodopus sungorus) were used in this study. Canine skin sheets obtained from the lateral thorax under general anesthesia were cut into 10/15 mm...

Diagnosis and treatment of demodicosis in dogs and cats

“…Treatment of puppies with anti‐lymphocyte serum led to generalized demodicosis in eight puppies whereas their untreated littermates remained healthy . Subsequently, a T‐cell exhaustion characterized by low numbers of circulating CD4 + T cells, together with increased serum concentrations of interleukin (IL)‐2, IL‐5, IL‐6 and IL‐18, and the immunosuppressive cytokines IL‐10 and TGF‐beta were reported in a number of studies comparing dogs with generalized demodicosis to healthy controls . By contrast, the proinflammatory cytokine TNF‐alpha was reduced in dogs with demodicosis .…”

“…Demodicosis is a common disease in canine practice caused by a proliferation of Demodex mites. These mites are normal commensal organisms in the hair follicles of many mammals . In the dog they are transmitted during the first days of life from the dam to the puppies .…”

Demodex: a skin resident in man and his best friend

“…However, the patients involved were younger than would be expected for detectable Demodex presence. In addition, D. canis was found to survive and reproduce in dog skin engrafted onto SCID mice, but did not spread to the surrounding mouse skin 29 …”

Study of Demodex mites: Challenges and Solutions

“…Mites survived longest (about 85 h) in the human serum medium. Tani et al . used xenografts of demodectic skin from dogs and hamsters onto immunocompromised SCID mice skin.…”

“…Mites survived longest (about 85 h) in the human serum medium. Tani et al 55 used xenografts of demodectic skin from dogs and hamsters onto immunocompromised SCID mice skin. After 90 days, recipient mice were killed and the mites were shown to be alive within the grafted skin.…”