A two-year-old male pet mouse (Fig. 1) and a two-year-old female pet rat (Fig. 2), both diagnosed previously with neoplasia, were presented by different owners. The mouse was kept in a group of three mice; the rat in a group of five rats and four guinea pigs. Both animals had been increasingly restless and irritated for several days and were scratching their bodies. Although the mouse did not show any skin lesions, the rat had excoriations on the head and neck. In addition, the rat's owner reported that her pet had been difficult to handle over the past several weeks.

Figure 1
figure 1

A two-year-old male mouse with a history of pruritus.

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Figure 2
figure 2

A two-year-old female rat with pruritus and excoriations on the head and neck.

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Both animals demonstrated significant agitation and pruritus. The rat had moderate pruritus, resulting in alopecia and excoriations on head and neck. The integument of the mouse, however, did not show any irritation: its coat was intact and shiny. After parting the coat on the back, a close examination of the skin enabled the macroscopic identification of ectoparasites on both animals. No parasites were found on the abdomen. Appetite and nutritional status were good in both animals, despite their restlessness and irritation.

We took impression smears of the parasites at several locations using adhesive tape and applying the preparation to a glass slide. On microscopic examination of the samples, we identified several stages of parasites (Fig. 3). In addition, we saw parasite eggs glued to hair. We made a diagnosis based on the clinical signs and the microscopic identification of the parasites in the impression smears taken from both animals.

Figure 3
figure 3

Adhesive tape strip showing a gravid female parasite shortly after a blood meal.

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Based on the information provided, what do you think the parasite is? How would you treat it?

What's your diagnosis?