With the term “Ringworm“one of the most common is indicated superficial mycoses of the cat and dog found all over the world. Ringworm takes the name of dermatophytosis if we refer to its pathogen: dermatophytes. They have a high capacity for transmission between animals and from animals to humans, becoming one of the most common zoonoses.
Ringworm, what is it?
Ringworm is one dermatological pathology caused by a mushroom filamentous capable of using the keratin present on the animal’s skin as the only source of energy. The fungus, arriving on the animal, invades the hair bulb and obtains the energy necessary for its proliferation in the form of fungal hyphae, called macroconidia; in particular conditions to facilitate its transmission it can assume more resistant forms: the spores or arthroconidia.
The dermatophytes that have been most isolated in dogs and cats are the Microsporum canis (especially in cats), the Trichophyton mentagrophytes, the Microsporum gypseum and the Microsporum (Ninnizzia) persicolor. The first two deserve particular attention as pathogens of zoonoses, therefore capable of being the cause of the dermatological pathology in the owners of infected dogs or cats.
How is ringworm transmitted?
There transmission of ringworm it can happen for direct contact with an infected person or for indirect contact environmental or inanimate objects on which spores have been deposited. Blankets, pet carriers, sofas, kennels, carpets, leashes must also be considered infected and disinfected for avoid a continuous reinfection of our dogs and cats and of ourselves.
Following contact with the animal’s skin, the fungal spore takes about 6 hours to activate and begin its reproduction.
It is important to know that fungi can cause disease when some are present predisposing factors which alter the immune system and make the subject more vulnerable.
The conditions that facilitate the proliferation of the fungus they can be:
- a immune system not still quite qualified, as in very young subjects, or debilitated, in elderly subjects
- the presence of skin lesions or parasites, which alter the skin barrier system and can cause itching with consequent self-trauma
- too frequent washing, which alter the sebum present on the skin for protective purposes
- the concomitance of immunosuppressive pathologies or debilitating. In cats, it may be associated with retrovirus infections, such as feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV).
- treatment with immunosuppressive drugs
- the lifestyle of the animal, being facilitated a transmission in environments of cohabiting cats and dogs
- environmental conditions of temperature and humidity
All breeds of dogs and cats are sensitive to the presence of dermatophytes, but dogs of Breed Dalmatian, Poodle, Jack Russel Terrier, Manchester Terrier and Yorkshire Terrier they can more easily develop a generalized symptomatological form. For the cats it is thought that i Persians and the other long-haired breeds help the proliferation of the fungus, even if a real breed predisposition has not been found.
How does it manifest itself?
The keratinolytic action of the dermatophyte can cause the formation of rounded alopecic lesions on the animal’s body, which can extend over larger areas causing a so-called “generalized” shape.
The “focal” form of the pathology see small lesions characterized by hair loss in the centrifugal direction. In fact, from the point of establishment the fungus will consume the keratin leading to hair loss and will move towards the still healthy peripheral hair. The lesions usually affect the front of the body: legs, muzzle and ears are the first sites of development, but it is easy to see lesions also in other places due to the transport of the fungus by the animal through licking.
A particular condition of the cat is to be able to develop asymptomatic forms, to be considered in cases of infection of cohabiting dogs / cats and dermatological lesions of the owner, in which the animal has the role of carrier of the fungus without developing dermatological symptoms.
Ringworm is not a primarily itchy disease: itching can occur due to secondary infections or predisposing factors. While this is the rule, itchy lesions can be found in adult cats with moderate to severe itching.
Additional symptoms of skin progression are often seen due to inflammation created by the fungus. They can be visible inflammatory scales and scabs, pustules or papules, until you get to wet lesions and exudative caused by bacterial sharing.
How is the diagnosis made?
After a first general examination and dermatological lesions the vet can diagnose the presence of dermatophytes through three techniques.
- A first screening exam is carried out using the Wood’s lamp. By illuminating the animal’s coat with its ultraviolet light from this lamp, it is possible to visualize the dermatophytes present, which take on a greenish-yellow fluorescent color. However, this technique does not totally exclude the presence of dermatophytes on the hair in case of non-fluorescence and has the limit of leading to a positive result even in the presence of chemical substances for local treatments.
- For this reason it is always advisable to confirm the first result with microscopic examination of the hair. The sample collected in the peripheral areas of the lesions (where the fungus is most active) is obtained by scarification of the skin and viewed under the microscope. The hair, in case of fungal infection, will present clusters or chains of fungal spores inside and on the surface.
- The third method that can be used is that ofcultural examination. The sample in this case can be obtained by skin scarification, pulling peripheral hairs from the lesions or passing a sterile brush over the entire coat of the animal. The collected material is then deposited in a special soil, above which fungal colonies can develop.
Which therapy is most effective?
The antifungal treatment it must be implemented not only for a resolution of the symptoms in the animal, but also to avoid the easy spread of the fungus in the environment and to other subjects. Infected material consisting of hairs and fungal spores remains active for up to 18 months in the environment.
Effective therapy sees the use of medications for systemic use associated with local treatment of lesions.
Medicines that can be used for systemically with antifungal action are:
- itraconazole, registered for cat in liquid formulation, it is the first choice for its safety of use. The therapeutic protocol is given by administering the drug every other week for at least three cycles.
- the ketoconazole, antifungal registered for the dog, but which has some side effects such as anorexia, vomiting and hepatotoxicity.
- there griseofulvin, no longer usable in Europe for adverse haematological, gastrointestinal and teratogenic effects in pregnant subjects.
THE topical treatments require the owner to be willing to perform sponging on alopecic lesions at least twice a week, focusing mainly on the peripheral hair. There are numerous products on the market in liquid form, spray or antifungal sponges, for which the hair clipping can be proposed for greater ease and effectiveness of action.
A treatment becomes effective if carried out for the right amount of time. These therapies antifungals in fact need a time of almost two months and it is important to finish after receiving the result of two negative cultures. If after 8 weeks the treatment has not yet had an effect, the veterinarian will evaluate the investigation of the case for any concomitant pathologies.
How to prevent ringworm?
- The main prevention is given by one minimization of contacts with infected animals. This concept applies both to cohabiting animals, for which a division of the living areas is necessary, and to people who may be more sensitive. After a diagnosis of mycosis in animals it is therefore necessary to avoid direct contact with elderly children and subjects with a compromised immune system, on which the fungus can more easily cause dermatological lesions.
- Also the environment has a great dissemination role. For this reason a valid environmental disinfection and contaminated objects can be carried out with the use of sodium hypochlorite solutions (household bleach) diluted in water with a ratio of 1:10 or with solutions of enilconazole. The latter exist in fumigant formulations, but are not authorized for domestic use or for use in catteries and kennels.