Dermatophyte types
Dermatophyte infections in pets are caused almost exclusively by members of the families Microsporum and Trichophyton. The latter family also includes, despite its name, Arthroderma benhamiae, which occurs mainly in guinea pigs. All dermatophytes share the unique property to be able to digest keratin, the main component of hairs and skin cells.
NB: Dermatophytes are not host species specific. However, it is true that Microsporum species occur most often, not exclusively, in cats and dogs, and Trichophyton species in rodents. It is also important to know that young animals/people are much more sensitive to the infection than adults.
How does the infection occur?
In the vast majority of cases, the source of infection is another animal with which there has been direct or indirect ‘contact’. Trichophyton-infections in cats and dogs often result from playing with hedgehogs or prey animals. In horses, infections occasionally occur that originate from the soil.
So-called carriers occur very sporadically in cats, rabbits and guinea pigs. These animals have no visible abnormalities, but they do spread the infection. Visibly infected animals obviously do this too. Dermatophytes produce spores (comparable to plant seeds) that can ‘survive’ in the environment (house/stable, etc.) for a long time and can cause infections in susceptible individuals. The patient’s environment must therefore always be included in the treatment (see ‘Treatment,In general ‘).
Environment also ‘contaminated’
The fact that the environment is contaminated means that the coat of healthy animals in that environment may also be contaminated. This can lead to incorrect conclusions in the event of improper interpretation of test results.
Often difficult to recognise
Because the clinical picture of a dermatophyte infection is often not typical, further investigation is required to get a diagnosis. This is most reliably done by ‘old fashioned’ culturing or, more recently, by tests based on the polymerase chain reaction (PCR). For more information refer to Test