Ornithonyssus bacoti Dermatitis Incorrectly Diagnosed as Delusional Parasitosis

Yangyang Ma Department of Dermatology, Hangzhou Third People’s Hospital, Hangzhou, China

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Wenting Hu Department of Dermatology, Hangzhou Third People’s Hospital, Hangzhou, China

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A 70-year-old female patient was admitted with cutaneous pruritus and a reported parasite infestation over the past month. Previously diagnosed with delusional parasitosis at another hospital, dermoscopy and smears yielded no evidence of parasites or eggs. Physical examination revealed scattered erythematous papules on the trunk and limbs, accompanied by extensive scratch marks (Figure 1A). Despite prior negative findings, the patient insisted on the presence of parasite, claiming to catch more than 30 bugs daily. Upon closer inspection, bloodstains were found on her underwear, and shaking her clothes revealed the presence of parasites. Microscope examination confirmed Ornithonyssus bacoti, also referred to as the tropical rat mite (Figure 1B). The patient, who had a recent rat infestation at home, responded well to antiallergic treatment and environmental disinfection.

Figure 1.
Figure 1.

(A) Scattered erythema, papules, and scratch marks are visible on the patient's back. (B) Tropical rat mite under microscopy (×100).

Citation: The American Journal of Tropical Medicine and Hygiene 110, 5; 10.4269/ajtmh.23-0747

Tropical rat mite dermatitis, caused by O. bacoti, is a rat-origin parasitic disease. Unlike Sarcoptes scabiei or Trombiculidae, which inhabit human skin, O. bacoti is challenging to detect through routine dermatological examinations (scurf curettage and dermoscopy) due to its nonparasitic nature on human skin. Consequently, patients are often misdiagnosed with common dermatitis or delusional parasitosis when evidence of parasites is lacking.1 To improve detection rates, patients are advised to use tape to collect suspected insect for microscopic examination.2,3 We report here a rare case of O. bacoti infection, emphasizing the significance of bloodstains on underwear (resulting from crushed female mites after bloodsucking) and a history of rodent exposure are crucial diagnostic clues.

REFERENCES

  • 1.

    Beck W , Folster-Holst R , 2009. Tropical rat mites (Ornithonyssus bacoti)—Serious ectoparasites. J Dtsch Dermatol Ges 7: 667670.

  • 2.

    Nath AJ , Islam S , Sahu S , 2016. Use of scanning electron microscopy to confirm the identity of tropical rat mite (Ornithonyssus bacoti): The cause of rat mite dermatitis. J Parasit Dis 40: 161165.

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  • 3.

    Nazzaro G , Bortoluzzi P , Veraldi S , Berti E , 2019. Adhesive tape as the key to solve a case: A quiz. Acta Derm Venereol 99: 10631064.

Author Notes

Authors’ addresses: Yangyang Ma and Wenting Hu, Department of Dermatology, Hangzhou Third People’s Hospital, Hangzhou, China, E-mails: sendnote@126.com and m15990109182@163.com.

Address correspondence to Wenting Hu, Department of Dermatology, Hangzhou Third People’s Hospital, Hangzhou, China. E-mail: sendnote@126.com
  • Figure 1.

    (A) Scattered erythema, papules, and scratch marks are visible on the patient's back. (B) Tropical rat mite under microscopy (×100).

  • 1.

    Beck W , Folster-Holst R , 2009. Tropical rat mites (Ornithonyssus bacoti)—Serious ectoparasites. J Dtsch Dermatol Ges 7: 667670.

  • 2.

    Nath AJ , Islam S , Sahu S , 2016. Use of scanning electron microscopy to confirm the identity of tropical rat mite (Ornithonyssus bacoti): The cause of rat mite dermatitis. J Parasit Dis 40: 161165.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Nazzaro G , Bortoluzzi P , Veraldi S , Berti E , 2019. Adhesive tape as the key to solve a case: A quiz. Acta Derm Venereol 99: 10631064.

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