Ringworm is a poorly named skin problem. It has
nothing to do with worms. The causative agent in cats is one of
two fungi that have a prediliction for the hair follicle or the
hair shaft. In people, these fungi can cause a slightly raised,
reddish ring, which may or may not be itchy and/or scaly- hence
the ringworm misnomer.
In cats the fungus will cause spreading, symmetric hair loss- usually
a circular, growing bald spot. Often in cats, the area looks flaky.
Occasionally, it is mildly inflamed and may or may not be itchy.
Common sites of occurrence are the face, ears, paws, and nail beds.
Cats pick up ringworm from direct contact with infected cats, dogs,
birds, or people. It can also be spread indirectly by exposure to
the fungal spores, which can exist in the environment. You can pet
a dog or cat who has no lesions and if they are an symptomatic carrier
you can transfer the fungus to yourself or your cat.
Except in immune compromised patients, ringworm is usually not
dangerous, but it can be stubborn to knock out. Often, it is self-limiting
without treatment and after weeks the spots will stop growing as
immunity steps in. Treatment will greatly speed up its resolution.
Remember, the bald spot will persist from weeks to months depending
on whether the hair follicles are at rest or active. A lack of spreading
is an encouraging sign.
Ringworm can be easy or difficult to diagnose because it has many
appearances. One of the fungi- Microsporum canis will often fluoresce
under ultraviolet light. This makes for a rapid in office diagnosis.
Some M. Canis and all Trichophyton mentagrafides don’t fluoresce
and identification requires a Fungal Culture which can take 5-14
days to become positive.
Treatment initially, is usually just with antifungal ointments-
we like Miconazole. Lamasil is good ointment, but we do not want
the cat licking it. It either needs to be used sparingly and rubbed
in like a vanishing crème or used only on parts of the cat,
which he can’t lick like the head, ears or back of the neck.
If topical medications do not work we can use systemic pills either
Griesiofulvin or Itraconazole [Sporanox]. Blood tests are required
with these medications to make sure they are not causing liver or
kidney problems or bone marrow depression. This is why we usually
reserve the systemics for refractive, severe cases. Sometimes medicated
shampoos or dips are useful ancillary treatments.
There is no way totally protect your cat or yourself from ringworm.
Especially since it can be passed on via objects. An environment
can be contaminated and the spores may remain infective; how long
they remain infective, we are not sure. The good news is that if
you have had a fair amount of pets- you are likely to be immune
to ringworm from past exposure. However, petting strays could expose
your cat, especially if the strays have crusty bald spots- so be