areas of contact and stroking habits of the pet owners, but are generally found on the upper body, arms and neck.
 Chronic, excoriated lesions of human skin associated with
infestation with Cheyletiella.
Not all humans are equally susceptible to Cheyletiella. Statistically the rate of infestation for in-contact humans is 30 to 40 % for Cheyletiella mites.
Fleas
Flea bites causing itchy skin lesions occur in and are recognised by many people. They appear as small papules, mostly in clusters, that are intensively pruritic.
The main cause of flea bites in humans is Ctenocephalides felis, and many pet owners treat their animal for fleas if they experience itchy skin lesions themselves.
In most cases, flea infestation occurs through newly hatched, hungry adult fleas. They occur at the surfaces of carpets, for example, and wait for a host. They can jump up to 60 – 70 cm high, thus lesions are found on the legs and up to the knee area of adults, and higher up on children.
Fleas suck blood several times in the same area, which causes the lesions to be arranged in groups. If there is direct transmission from a flea-bearing animal, human lesions are found mostly on the forearm or other body regions where the pet comes into contact.
 A cluster of flea bites on human skin.
|  | DermatophytesMicrosporum canis and Trichophyton mentagrophytes
Microsporum canis is a zoophilic dermatophyte that most commonly affects cats, dogs, small mammals and humans. Dermatophytes are exclusively found in keratinised tissue: hair, claws and stratum corneum. Signs of a dermatophytosis include broken, stubbly hair, hair loss (often circular areas) and scaling. Onychomadesis and other signs of nail damage are seen in onychomycosis. The principal transmitters of Microsporum canis are cats. This dermatophyte is excellently adapted to this species, and infected cats often show only mild lesions or no signs when infected. Especially longhaired cats tend to be asymptomatic carriers and can be a permanent source of infection. Another source for dermatophytosis in humans that is sometimes underestimated are small mammals. A high percentage of them can be asymptomatic carriers of Trichophyton mentagrophytes. Commonly rabbits and guinea pigs are either asymptomatic carriers, or show only mild skin lesions. The lesions can be erythematous or crusty, and are often located on the nose or the bridge of the nose. They are often mistaken for injuries from the cage or bite marks.
Human infection happens through direct contact with the diseased animal, and can also happen indirectly (via infectious spores in the environment). Skin lesions in children commonly affect face, neck, arms, legs and the upper body, through close contact with the animal in those areas. The lesions in humans tend to be localized or affect certain regions of the body (e.g. head, “Tinea capitis”). They are much larger than the papules caused by ectoparasites.
 Erythematous circular lesion caused by Microsporum canis infection in human skin.
The “classical” ringworm lesion in humans is well circumscribed, more or less round (ring-shaped), with erythematous and scaly edges and shows a distinct pruritus. It lasts for weeks, if untreated, and often new lesions develop in other areas of the skin. Dermatophytosis necessitates an intense treatment regimen: the animal and the affected owner should be treated. Thorough treatment of the environment is strongly recommended since spores in the environment can remain infectious for years. Treatments in humans have unsatisfactory results if re-infections cannot be avoided.
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