Dermatophytes in veterinary practice.

This article addresses the study on dermatophytes, a group of fungi causing ringworm in humans and animals and their characteristics such as penetrating hair and skin layers, producing spores around the hair shaft and possibly causing alopecia. The paper classifies these fungi into anthrophilic (affecting humans) and zoophilic (affecting animals and humans), and discusses factors contributing to susceptibility.

About Dermatophytes and the Infections They Cause

• The term dermatophytes refer to a group of fungi that invade hair, skin, and in humans, the nails. These organisms cause ringworm and other similar diseases.
• These fungi were recognized centuries ago, but it was not until 1839 that they were associated with skin diseases by a German doctor named Schoenlein.
• In animals, the primary characteristic of dermatomycoses (the diseases caused by these fungi) is the involvement of hair. In some cases, infection of nails has been reported in dogs and cats.

Infection Process of Dermatophytes

• These fungi initially invade superficial layers of the skin and then form thread-like structures called hyphae. The hyphae reach the hair follicle where they grow down between the hair and follicle wall, reaching midway and penetrating the hair’s cuticle, eventually growing towards the bulb.
• These fungi then give rise to spores forming a sheath around the hair shaft. Parasites belonging to the genus Microsporum produce small spores and those from the genus Trichophyton produce large ones.
• This process causes autolysis of the hair fibres, resulting in hair breakage and leading to alopecia which is hair loss. In the skin, this invasion causes inflammation, fluid exudation, leukocyte accumulation and sometimes scaling and the formation of thick, crusty scabs.

Types, Spread and Susceptibility to Dermatophytes

• Dermatophytes are not host-specific and can be split into two groups for an epidemiological perspective. The anthrophilic group is mostly confined to humans, while the zoophilic group can live as parasites in both humans and animals.
• They can spread via contact by the transfer of infected hair or skin fragments. Dental surgeon G. La Touche and microbiologist L.K. Georg have published extensive reviews on the epidemiology of these fungi.
• Youths are more susceptible to these infections compared to adults. Dietary deficiencies, primarily in vitamins, or prolonged antibiotic treatment can increase susceptibility to these fungi.