The Ringworm Battle Plan

by Lorraine Shelton

Published January 2002

Whenever the subject of Ringworm arises in a conversation amongst cat breeders, many questions are asked about what a person should do to get rid of it - once and for all time.

Ringworm is a determined and aggressive enemy.
To defeat it, you must be be equally determined and aggressive.
And you need to have a battle plan!

The First Step: Treatment with Program (lufenuron)

Because of its extremely low toxicity, the first step in your battle against ringworm is administering Program (lufenuron) at 40-50 mg per pound every two weeks.

  • It is better to "overdose" than to underdose.
  • All adult cats should receive one of the largest dog tablets (I get mine, as well as other non-prescription items described in this article, from California Veterinary Supply.
  • Kittens can be treated anytime over the age of eight weeks and should receive half of a large dog tablet or one complete liquid dose of the large cat size size suspension.
  • Treatment of kittens under eight weeks of age is off-label, but there is no reason to believe it would be harmful.
  • Program is safe in pregnant and nursing queens.
  • Program is only absorbed if given with a LARGE meal. The fattier, the better. Mix the crushed tablet up with a treat your cat will gobble up and then follow it immediately with your cat's favorite meal.
  • Continue to treat until two cultures of every cat in the cattery come back negative, done at least one or two weeks apart.
  • For high risk catteries (I consider ALL Persian catteries "high risk"), continue to dose once a month indefinitely.

For many, if not most cats, treatment with Program alone is not sufficient.

There is NO "one step" solution
to eliminating fungus from your cattery.
You need use all the weapons at your disposal
to defeat this most persistant of enemies.


Next Step: Other Anti-fungal Drugs Options

  • Griseofulvin (Fulvicin)
  • Itraconazole (Sporonox)
  • Fluconazole (Diflucan)
  • Terbinafine (Lamisil)

Griseofulvin (Fulvicin) is the most commonly used antifungal drug. Treatment must continue for at least 12-16 weeks. Some cats, in particular Persians, can experience a deadly form of bone marrow suppression or liver damage when treated with Fulvicin. This reaction is independent of the dose received.The dose for Fulvicin is 7 mg per pound of the microsized formulation twice a day, or 3.5 mg per pound of the ultra-microsized formulation twice a day. Fulvicin must be given with a fatty meal to be absorbed. Fulvicin should not be used in breeding males, pregnant queens, or within less than two months of breeding a queen.

Safer and more effective antifungal drugs include itraconazole (Sporonox) at 5mg per pound once a day, fluconazole (Diflucan) at 5 mg per pound every other day, and terbinafine (Lamisil) at 10mg per pound once a day.

Mycological clearance with these drugs usually takes about half to 2/3 the time of treatment with Fulvicin.

These drugs should not be used in pregnant queens, but do not affect males like Fulvicin does. No controlled studies have been found to find out which of these three newer drugs is more effective. Ketoconazole (Nizoral) is far more toxic than any of the other drugs mentioned and should not be used in cats.

Topical treatments The only topical treatment proven to be efficacious in controlled laboratory studies is lime sulfur dips (1:32 or 1:16 dilution).

  • Persians should be shaved, off the premises if possible to prevent contaminating the environment with spores.
  • Throw away the clipper blade and immediately dip the cat in lime-sulfur afterwards.
  • Lime-sulfur is safe in kittens, pregnant, and nursing queens.
  • Do not allow the cat to lick itself until the dip has dried (collar if necessary).
  • After the lime sulfur has dried, wash the nipples of nursing queens before reintroducing kittens.
  • Dip at least once a week.
  • Other shampoos claim to be fungicidal, but none have demonstrated efficacy by independent laboratory testing as yet.

Efficacy against the fungus itself is insufficient, it is the SPORES that cause reinfection. Shampooing cats can make them worse, as the hairs break off from scrubbing and infect the surrounding skin. Dipping is better. Clipping also opens up the hairs and releases spores, but for longhaired cats the advantages of clipping outweigh the disadvantages.

TREAT EVERY CAT IN THE HOUSE Not doing so will only create a cattery with chronic carriers of ringworm and recurrent infections.

The Environment Cleaning up the environment is the hardest part. The spores are almost unkillable, only concentrated bleach, highly carcinogenic chemicals that you don't want in your home, and enilconazole are effective in fighting the spores. Some folks have reported success fogging with solutions such as Virkon, but their efficacy has not been demonstrated in controlled laboratory studies. Bleach only works on a CLEAN surface, it does not work in the presence of organic material, so dipping cats in bleach is worthless. Enilconazole is toxic to cats and is no longer recommended to be used around or on them.

  • Discard all carpeted/fabric surfaces if possible.
  • Bleach all surfaces (1:10 bleach is a good workable solution and must be applied multiple times).
  • High temperature steam may also be effective. This is not the normal steam cleaning offered by your local furniture and carpet cleaner... you need HIGH TEMPERATURE steam.
  • Vacuum, vacuum, vacuum, discarding the bag each time and spraying down the vacuum with 1:10 bleach after each use.
  • Buy a true HEPA filtered vacuum.
  • Blow torching metal cages is an excellent approach if you have the resources to do so.

Vaccination The ringworm vaccine is worthless as a preventative, but may help individual cats clear their lesions faster.

How long do you treat? This is the question I get asked most often. There is only one answer: AS LONG AS IT TAKES TO ACHIEVE MYCOLOGICAL CLEARANCE. There is no "magic time" after which your cats will be cured. You can only determine whether your cats are cleared of the infection through CULTURING.

Culture Testing The Mackensie Brush Technique is used to screen for ringworm. A new, sterile toothbrush is combed through the entire coat of the cat and then pressed into culture medium. Multiple cats can be cultured on one culture "slant" to help keep costs down when screening an entire cattery. Isolate cats that still culture positive from cats that culture negative. Keep treating and culturing until two cultures come back negative, done at least a week or two apart. DO NOT assume a cat is "cured" simply because the lesions are gone. Cats with no lesions whatsoever can be your most potent carriers and sources of reinfection. A cat that cultures clean twice will no longer be contagious.

Wood's Lamp (Black Light) Not all ringworm can be visualized with a Wood's Lamp. Do not rely on this as a diagnostic tool.

When is Ringworm not Ringworm? Other diseases CAN mimic ringworm, most notably body mites. If treatment with antifungal drugs is not working, treat with ivermectin. Not all ringworm looks the same. Ringworm can be completely asymptotic, exhibit itself as a mild case of "dandruff", skin discoloration, subcutaneous "tumors", or large weeping lesions. Some cats are more susceptible to ringworm than others and this susceptibility can be inherited. Ringworm outbreaks can be a symptom that a cat has a weakened immune system. Healthy, adult, shorthaired cats can clear this infection themselves with no treatment whatsoever in about 16 weeks. But kittens, cats with poor immune systems, cats under stress, and longhaired cats require aggressive treatment. This is a zoonotic disease (transmittable to humans), so it should not be taken lightly.

Prevention To prevent infection in the first place: culture all incoming cats before and after their quarantine period. Isolate all show cats and bath them upon returning from a cat show. Despite your best efforts, reinfection *is* common. Ringworm has been described as "an extremely well evolved parasite of feline keratin". It isn't easy to avoid.

The most successful warriors in this battle
are the most AGGRESSIVE and the most DETERMINED

Good luck!


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