Demodex musculi, a prostigmatid mite that has been reported infrequently in laboratory mice, has been identified with increasing frequency in contemporary colonies of immunodeficient mice. Here we describe 2 episodes of D. musculi infestation with associated clinical signs
in various genetically engineered mouse strains, as well as treatment strategies and an investigation into transmissibility and host susceptibility. The first case involved D. musculi associated with clinical signs and pathologic lesions in BALB/c-Tg(DO11.10)Il13tm mice,
which have a defect in type 2 helper T cell (Th2) immunity. Subsequent investigation revealed mite transmission to both parental strains (BALB/c-Tg[DO11.10] and BALB/c-Il13tm), BALB/c-Il13/Il4
tm, and wild-type BALB/c. All Tg(DO11.10)Il13tm
remained infested throughout the investigation, and D. musculi were recovered from all strains when they were cohoused with BALB/c-Tg(DO11.10)Il13tm index mice. However, only Il13tm and Il13/Il4
tm mice demonstrated persistent infestation after
index mice were removed. Only BALB/c-Tg(DO11.10)Il13
tm showed clinical signs, suggesting that the phenotypic dysfunction of Th2 immunity is sufficient for persistent infestation, whereas clinical disease associated with D. musculi appears to be genotype-specific. This
pattern was further exemplified in the second case, which involved NOD.Cg-PrkdcscidIl2r
tm1Wjl/SzJ (NSG) and C;129S4 Rag2tm1.1Flv Il2rgtm1.1Flv/J mice with varying degrees of blepharitis, conjunctivitis, and facial pruritis. Topical amitraz
decreased mite burden but did not eliminate infestation or markedly ameliorate clinical signs. Furthermore, mite burden began to increase by 1 mo posttreatment, suggesting that topical amitraz is an ineffective treatment for D. musculi. These experiences illustrate the need for vigilance regarding opportunistic and uncommon pathogens in rodent colonies, especially among mice with immunologic deficits.
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Document Type: Case Report
Section of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA. [email protected]
Section of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
Department of Veterinary Science, The University of Texas MD Anderson Cancer Center, Bastrop, Texas, USA
Department of Comparative Medicine, Mayo Clinic, Rochester, Minnesota, USA
Publication date: 01 August 2016
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Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.
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