RINGWORM IN CATS (DERMATOPHYTOSIS)
What is ringworm?
“Ringworm” is the common name given to a fungal infection of the superficial layers of the
skin, hairs and nails. The name comes from the classical appearance of C-shaped red
raised ‘ring’ marking the boundary of inflammatory lesions of the infection in people. The
fungi responsible for ringworm belong to a specialized group known as dermatophytes,
and these can cause disease in both humans and animals. There are many distinct
species within the group. Some species of dermatophytes will only infect humans or only
infect certain animals, whereas others can be spread from animals to man.
In cats, one type (species) of dermatophyte called Microsporum canis is responsible for
almost all ringworm infections, and this species is infectious to both cats and dogs, and
also man. Occasionally ringworm infections in cats may be caused by species such as
Trichophyton mentagrophytes.
What does ringworm look like?
The lesions of ringworm in cats may be very mild or even undetected. A ‘cigarette ash’
scaling in the depths of the coat may be the only visible indicator. In other cases there are
discrete, circular, thickened plaques with hair loss (alopecia) that occurs due to the
increased fragility of infected hairs. The main sites for these lesions are the skin of the
head, chest, forelegs and along the ridge of the back to the base of the tail. These
lesions are not usually itchy. Occasionally infection of the claws (onychomycosis) may
occur. Claws become rough and pitted with a scaly base. The claw may become
deformed. Ringworm may sometimes cause a more generalized disease where a much
larger area of the body is affected often with patchy hair loss.
How do you diagnose ringworm infection?
The majority of cases of feline ringworm caused by M. canis will show-up as a yellow-
green fluorescence when the skin and coat are examined in a dark room with a special
ultraviolet lamp. However, not all cases show clear fluorescence and some other
dermatophytes like Trychophyton mentagrophytes do not fluoresce. In addition, some
skin ointments and other materials will fluoresce and may give a false positive result.
Confirmation of ringworm requires culture of the fungus in a laboratory. For this a sample
of hair and skin scrapings are taken. Culture results take up to four weeks but there is
usually an indication within a few days if the result is positive.
Because there are a number of causes of hair loss in cats these other causes may have
to be ruled out by additional tests.
Treatment of ringworm
Although in many cats ringworm is a self-curing infection (with resolution typically taking 3-
5 months), treatment of the disease is always indicated to minimize the risk of spread of
infection to humans (particularly children) and other pets.
Two forms of treatment can be used for cats with ringworm - topical therapy (application
of creams, ointments or shampoos) and systemic therapy (administration of anti-fungal
drugs by mouth). In addition, attention must also be given to cleaning the environment.
1. Topical treatment
Occasionally, topical therapy is used alone for treatment of ringworm, but more
commonly it is used in combination with oral dosing. Various creams and ointments are
available to apply to localized areas of the skin affected by ringworm, or if there is more
generalized disease your veterinarian may advise the use of a shampoo. It is extremely
important only to use preparations that have been specifically provided or recommended
by your veterinarian for topical treatment of cats.
2. Oral treatment
For most cases of ringworm effective treatment will require administration of an oral anti-
fungal drug. The most widely used drug for this purpose is griseofulvin, although newer
alternative drugs are becoming available. The response of individual cats to treatment
varies, and it is important that therapy is not stopped too soon, otherwise the disease
may recur. Treatment must usually be continued for a minimum of six weeks, and in some
cases much longer therapy is required. If there is more than one cat in the household, try
to separate infected from non-infected cats and just treat the infected ones. In some
situations, it may be preferable to treat all of the cats. Your veterinarian will be able to
advise you regarding your own circumstances.
3. Environmental cleaning
Hairs infected with ringworm contain numerous microscopic fungal spores that can be
shed into the environment. Infection of other animals and humans can occur, either by
direct contact with an infected cat, or through the environmental contamination with these
fungal spores. In addition to minimizing direct contact with an infected cat, it is therefore
also important to attempt to keep the environment free of spores. Topical treatment of
affected skin, and clipping of infected hairs (with careful disposal) may help to reduce
environmental contamination, and it is also worthwhile considering restricting the cat to
certain rooms of the house that are easy to clean. Thorough vacuum cleaning of rooms
where the cat has access to is the best way to minimize environmental contamination,
and this should be done as frequently as is possible (e.g. daily or every other day). In
addition, the use of diluted bleach is recommended in areas that can be readily
disinfected.
Will my cat recover?
The vast majority of cats, if treated appropriately, will recover from ringworm infection
within a few weeks. While the appearance of the lesions may not change much during the
first week or so of treatment, some improvement should be evident within 2-3 weeks.
Occasionally, despite appropriate treatment, the infection persists, and in this situation
your veterinarian may have to try alternative anti-fungal drugs.
The risk to humans
Ringworm can be transmitted quite readily to humans (particularly children) and it is
important to take appropriate steps to minimize exposure to the fungus while the cat is
being treated (see ‘Environmental Cleaning’ above). If any humans in the house develop
skin lesions (small patches of skin thickening and reddening, typically sharply
demarcated with raised scaly edges) early medical attention should be sought.
Ringworm in humans generally responds very well to treatment.
What is ringworm?
“Ringworm” is the common name given to a fungal infection of the superficial layers of the
skin, hairs and nails. The name comes from the classical appearance of C-shaped red
raised ‘ring’ marking the boundary of inflammatory lesions of the infection in people. The
fungi responsible for ringworm belong to a specialized group known as dermatophytes,
and these can cause disease in both humans and animals. There are many distinct
species within the group. Some species of dermatophytes will only infect humans or only
infect certain animals, whereas others can be spread from animals to man.
In cats, one type (species) of dermatophyte called Microsporum canis is responsible for
almost all ringworm infections, and this species is infectious to both cats and dogs, and
also man. Occasionally ringworm infections in cats may be caused by species such as
Trichophyton mentagrophytes.
What does ringworm look like?
The lesions of ringworm in cats may be very mild or even undetected. A ‘cigarette ash’
scaling in the depths of the coat may be the only visible indicator. In other cases there are
discrete, circular, thickened plaques with hair loss (alopecia) that occurs due to the
increased fragility of infected hairs. The main sites for these lesions are the skin of the
head, chest, forelegs and along the ridge of the back to the base of the tail. These
lesions are not usually itchy. Occasionally infection of the claws (onychomycosis) may
occur. Claws become rough and pitted with a scaly base. The claw may become
deformed. Ringworm may sometimes cause a more generalized disease where a much
larger area of the body is affected often with patchy hair loss.
How do you diagnose ringworm infection?
The majority of cases of feline ringworm caused by M. canis will show-up as a yellow-
green fluorescence when the skin and coat are examined in a dark room with a special
ultraviolet lamp. However, not all cases show clear fluorescence and some other
dermatophytes like Trychophyton mentagrophytes do not fluoresce. In addition, some
skin ointments and other materials will fluoresce and may give a false positive result.
Confirmation of ringworm requires culture of the fungus in a laboratory. For this a sample
of hair and skin scrapings are taken. Culture results take up to four weeks but there is
usually an indication within a few days if the result is positive.
Because there are a number of causes of hair loss in cats these other causes may have
to be ruled out by additional tests.
Treatment of ringworm
Although in many cats ringworm is a self-curing infection (with resolution typically taking 3-
5 months), treatment of the disease is always indicated to minimize the risk of spread of
infection to humans (particularly children) and other pets.
Two forms of treatment can be used for cats with ringworm - topical therapy (application
of creams, ointments or shampoos) and systemic therapy (administration of anti-fungal
drugs by mouth). In addition, attention must also be given to cleaning the environment.
1. Topical treatment
Occasionally, topical therapy is used alone for treatment of ringworm, but more
commonly it is used in combination with oral dosing. Various creams and ointments are
available to apply to localized areas of the skin affected by ringworm, or if there is more
generalized disease your veterinarian may advise the use of a shampoo. It is extremely
important only to use preparations that have been specifically provided or recommended
by your veterinarian for topical treatment of cats.
2. Oral treatment
For most cases of ringworm effective treatment will require administration of an oral anti-
fungal drug. The most widely used drug for this purpose is griseofulvin, although newer
alternative drugs are becoming available. The response of individual cats to treatment
varies, and it is important that therapy is not stopped too soon, otherwise the disease
may recur. Treatment must usually be continued for a minimum of six weeks, and in some
cases much longer therapy is required. If there is more than one cat in the household, try
to separate infected from non-infected cats and just treat the infected ones. In some
situations, it may be preferable to treat all of the cats. Your veterinarian will be able to
advise you regarding your own circumstances.
3. Environmental cleaning
Hairs infected with ringworm contain numerous microscopic fungal spores that can be
shed into the environment. Infection of other animals and humans can occur, either by
direct contact with an infected cat, or through the environmental contamination with these
fungal spores. In addition to minimizing direct contact with an infected cat, it is therefore
also important to attempt to keep the environment free of spores. Topical treatment of
affected skin, and clipping of infected hairs (with careful disposal) may help to reduce
environmental contamination, and it is also worthwhile considering restricting the cat to
certain rooms of the house that are easy to clean. Thorough vacuum cleaning of rooms
where the cat has access to is the best way to minimize environmental contamination,
and this should be done as frequently as is possible (e.g. daily or every other day). In
addition, the use of diluted bleach is recommended in areas that can be readily
disinfected.
Will my cat recover?
The vast majority of cats, if treated appropriately, will recover from ringworm infection
within a few weeks. While the appearance of the lesions may not change much during the
first week or so of treatment, some improvement should be evident within 2-3 weeks.
Occasionally, despite appropriate treatment, the infection persists, and in this situation
your veterinarian may have to try alternative anti-fungal drugs.
The risk to humans
Ringworm can be transmitted quite readily to humans (particularly children) and it is
important to take appropriate steps to minimize exposure to the fungus while the cat is
being treated (see ‘Environmental Cleaning’ above). If any humans in the house develop
skin lesions (small patches of skin thickening and reddening, typically sharply
demarcated with raised scaly edges) early medical attention should be sought.
Ringworm in humans generally responds very well to treatment.
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| Rockwall, Texas 75087 972-722-0066 |
| 1001 North W.E.Crawford (Highway 66 in Fate) Rockwall, Texas 75087 972-722-0066 |
| Dusty B. Goucher, DVM The Staff of the Animal Hospital of Fate |