Ringworm in Cats

Ringworm in Cats
Skin irritations such as ringworm, which is a fungus that is extremely common in rainy, damp weather. Ringworm is not a "worm" like the internal parasites roundworm and tapeworm; rather it is a fungus of the skin transmitted through spores in the environment from animal to animal or animal to people and people to animals. In cats it causes hair loss, much like a bald spot and is typically found on eartips and toes, as well as balding areas all over the body in severe cases. Ringworm does not form scabs. (If an animal has scabs on his or her body, this is usually dermatitis caused by allergies (most frequently allergic to flea bites). Dermatitis is not contagious.)

Be careful when treating animals or people for ringworm by wearing protective clothing such as long sleeved workshirts, surgeon gloves and washing yourself and all surfaces thoroughly with a 1:3 ratio of bleach and water or a strong veterinarian strength disinfectant solution prior to touching other people or animals.

Don't despair if it takes a long time for the ringworm to disappear as a case of ringworm can range from 4 weeks to 8 weeks and even longer, depending on the severity of the case and the particular cat's immune system. In some severe cases your vet may prescribe a medication such as Fulvicin that must be taken with fatty foods, such as canned food for cats and supplements such as Nutrical or Linatone to prevent liver problems down the road for the cat. There are baths available too, but special treatment is much simpler and easier to administer and works great!

The problem with most topical FUNGAL solutions is that they don't PENETRATE the deep tissues where fungus grows and most often, they don't work. The symptoms can go away for a few days, but then the itching and the ringworm spores continues to be active.

Ringworm in Cats

Ringworm is a skin disease caused by a fungus (plural: fungi). Because the lesions are often circular, ringworm was once thought to be caused by a worm curling up in the tissue. Ringworm has nothing to do with any type of worm.

Ringworm is also known as dermatophytosis. There are four species of fungi that can cause dermatophytosis in cats; it is most often caused by the organism called microsporum canis. Microsporum canis is so well adapted to cats that up to 20% of cats are thought to be asymptomatic carriers, meaning they have the organism but show no outward signs.

Ringworm is actually an infection in the dead layer of the skin, hair, and nails. The fungus is able to utilize this dead tissue (keratin) in the skin as a source of nutrition.

What cats are likely to get ringworm?

Genetic and environmental influences play an important role in feline ringworm infection. A significant amount of research remains to be done on this disorder. It appears that Persian cats are affected most frequently. In catteries, ringworm can be hard to control because of the numbers of animals involved.

What are the clinical signs?

The fungi live in hair follicles. As the organism invades and weakens the hair shafts, hairs break off at the skin line. Patches of hair loss tend to be round; as the fungus multiplies, the lesions may become irregularly shaped and spread over the cat's body. These patches may be associated with scaling and crusting of the skin. The lesions are sometimes pruritic (itchy), but this is not a consistent finding.

The incubation period is 10-14 days. This means that the exposure to the fungus and establishment of infection occurs 10-14 days before any lesions occur.

How is ringworm diagnosed?

Feline ringworm can be diagnosed by four different methods. In some cases, more than one technique is used.
  1. Identification of the typical "ringworm" lesions on the skin. This is the least accurate method since other skin diseases may have the same appearance.
  2. Examination of the scales and hair under the microscope. Some of the fungal elements, such as spores, can visualized with this technique.
  3. Fluorescence of infected hairs under a special light. This is a screening test which is useful because Microsporum canis will sometimes fluoresce as a bright apple green under ultraviolet light. Failure to fluoresce, however, does not eliminate ringworm as a potential diagnosis.
  4. Culture of the hair for the fungus. This method is the most accurate way to diagnose feline ringworm. After some hair is plucked from a lesion on the skin, it is placed on a special gel (culture media) to watch for growth of the fungus. Also, the color of the gel will change from yellow to red as the fungus grows. These cultures are checked daily. Most cats with ringworm will have a positive culture within 10 days, but in rare cases, growth may not occur for 14-21 days.
How is it transmitted?

Transmission occurs by direct contact between infected and non-infected individuals. It may be passed from dogs to cats and vice versa. It may also be passed from dogs or cats to people and vice versa. If a child has ringworm, he or she may have acquired it from a pet or from another child at school. Adult humans are relatively resistant to infection unless there is a break in the skin or there is suppression of the immune system (AIDS, chemotherapy, etc). Children are quite susceptible. Consult with your family physician if any family member develops suspicious skin lesions.

Transmission may also occur from the infected environment. The fungal spores may live in bedding or carpet for several months. They may be killed with a dilution of chlorine bleach and water (1 cup of chlorine bleach in a gallon of water) where it is feasible to use it.

How is it treated?

There are several methods for treating ringworm. The specific method(s) chosen for your cat will depend on the severity of the infection, how many pets are involved, presence of children in the household, and how difficult it will be to disinfect your cat's environment.

1. Griseofulvin. This is a drug, in tablet form, that is concentrated deep in the hair follicles where it can reach the site of active fungal growth. Griseofulvin should be given daily. Cats with active lesions should receive the tablets for a minimum of 30 days. At that time, the cat should be rechecked to be sure the infection is adequately treated. These tablets are not absorbed from the stomach unless there is fat in the stomach at the time they are given. This can be accomplished by feeding a high fat diet, such as a rich canned cat food or a small amount of fat trimmings from meats (often available at the meat departments of local grocery stores upon request of the butcher) or by allowing the cat to drink some rich cream. Griseofulvin is the most important part of the treatment. If you are not successful in giving the tablets, please call your vet for help. Griseofulvin is the only drug approved for systemic (oral) treatment of feline ringworm. It is very effective and has successfully treated the vast majority of affected cats. It does have some potentially significant side-effects.

a. Gastrointestinal signs of vomiting and diarrhea are the most common side-effects. These signs may stop if the dosage is divided over two or three treatments in a day.

b. It is a potent teratogen, meaning it can cause birth defects. As such, it should not be used to treat pregnant cats or cats which might become pregnant during the treatment period. It can potentially cause abnormalities in the breeding tomcat, as well, so may be best avoided for all reproductively-active cats. There are no reported effects for queens who become pregnant after griseofulvin therapy is completed.

c. Suppression of the bone marrow is a rare, but potentially fatal, complication of griseofulvin therapy. Toxicity cannot be predicted and may appear without warning.

2. Itraconazole is one of the newer drugs being used to treat ringworm. It is not approved for use in cats, but it is generally considered safe and effective. The cost of the drug is prohibitive in some cases. Some reports indicate that it is equal or possibly superior to griseofulvin in achieving a cure. It may offer the advantage of preventing fungal spores from adhering to the dead layer of the skin. For cats who cannot tolerate griseofulvin or are not cured by it, itraconazole is a good choice.

3. Baths using an antifungal shampoo. A bath should be given 3 times on an every other day schedule. Bathe exposed but unaffected pets once. These baths are important in getting the spores off the hairs so they do not drop into the environment and result in re-exposure. A lather should be formed and left on for 5-10 minutes before rinsing. Be aware that antifungal shampoos alone cannot be expected to provide a cure but are useful in the overall treatment plan.

4. Lime Sulfur Dip. This should be done twice weekly for the first two weeks, then once weekly for 4-6 weeks. Lime sulfur dip should also be applied to other pets (dogs or cats) in the household to prevent them from being affected. If they develop ringworm lesions, they should begin on griseofulvin. You should wear gloves when applying the dip and should remove jewelry before you start. Lime sulfur can change the color of some jewelry. This is an effective form of treatment, but the dip has an objectionable odor (rotten eggs).

5. Ringworm vaccine. This vaccine helps the cat develop immunity to the fungus. Other products are still used with it, but its use will hasten recovery. This is especially important if several other pets or children are exposed.

6. Shaving of the cat's hair. A total clipping of the cat's hair coat used to be considered standard practice. In some cases, this may still be advantageous; it may not be necessary in every case. Some studies have suggested that clipping may cause microscopic nicks in the skin and serve to further inoculate ringworm into the skin. Also, clipper blades can spread the fungus between cats. Clipping is most likely to be of help with long-haired cats and in households where more than one cat is infected.

Treatment will not produce immediate results; in fact, the areas of hair loss may get larger before they begin to get smaller. Within 1-2 weeks, the hair loss should stop, there should be no new areas of hair loss, and the crusty appearance of the skin should diminish. If any of these do not occur within two weeks, your vet should see your cat again.

Infected pets remain contagious for about 3 weeks if aggressive treatment is used. Contagion will last longer if only minimal measures are taken or if you are not faithful with the prescribed approach. Minimizing exposure to dogs, other cats, and your family members is recommended during this period.

When treatment is completed, ringworm should be cured. Although a carrier state can exist, this usually occurs because treatment is not long enough or aggressive enough or because there is some underlying disease compromising the immune system.

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.

How do you diagnose ringworm infection?

The majority of cases of feline ringworm will show up as a yellow green fluorescence when the skin and coat are examined in a dark room with a special ultraviolet lamp. Confirmation of ringworm requires culture of the fungus in a laboratory. For this a sample of hair, and skin are taken. Culture results take up to four weeks, but there is usually an indication within a few days if the result is positive.

Treatment of ringworm.

Two forms of treatment can be used for cats with ringworm.

Topical treatment: Occasionally topical therapy is used alone for the treatment of ringworm, but more commonly it is used in combination with oral dosing.

Oral treatment: For most cases of ringworm, effective treatment will require administration of an oral anti-fungal drug. The response of individual cats to treatment varies, and it is important that therapy is not stopped to soon, otherwise the disease may recur.

Environmental cleaning: Hairs infected with ringworm contain numerous microscopic fungal spores that can be shed into the environment. Infection to other animals and humans can occur, either with direct contact with an infected cat, or through the environmental contamination with these fungal spores. Thorough vacuum cleaning of rooms where the cat has access to is the best way to minimize environmental contamination. This should be done as frequently as possible. 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. The appearance of the lesions may not change much during the first week of treatment, some improvement should be evident within 2-3 weeks.

Ringworm can be transmitted to humans (particularly children) and it is important to take appropriate steps to minimize exposure to the fungus while the cat is being treated. If anyone in the household develop skin lesions, early medical attention should be sought.

What Causes it?

Microsporum canis accounts for 95% of all ringworm infections.

*The ringworm spores can live a long time.

*It infects growing hairs and skin.

*The incubation period is 7-14 days.

How are cats normally protected from it?

Intact skin


Antifungal substances in sweat and sebum

Who is most at risk?

* Young cats

* Ill or debilitated cats

* Pregnant or lactating queens

* Impaired immune function

* Persians or other long haired breeds

How do they get it?

Direct contact with spores from an infected cat

Indirect contact with spores

Soft material - clothing, bedding etc.

Grooming equipment

Feeding bowls

Litter trays

Cat's pen floors

Ventilation, filters, dust

What does it look like?

Ringworm has very variable signs

* Hair loss - patchy, irregular pattern, usually starts on face ears and muzzle

* Scales, mild reddening of skin

* Skin can become itchy

* It can infect nail bed, hairs and glands of chin and tail

* Ringworm can mimic many other skin diseases

How is it diagnosed?

Woods lamp. This only displays fluorescence in about 50% of M. Canis infections



How is it treated?

Most cases would resolve themselves if left untreated, but takes a long time. Treatment speeds recovery and reduces chance of spreading the infection. It also decreases contamination of the environment. Clipping reduces the number of spores, but can make the disease worse initially, as it puts a lot of fungal elements into the environment. Reserve this for severe, generalised cases with long hair Topical treatment reduces the spread of infection within the environment, but can increase recovery time. It can spread lesions if not careful and there is increased potential for spreading the infection to humans, when handling cats. There is also increased contamination of environment.

Examples of topical treatment: Malaseb®, chlorhexidine, povidine-iodine, Imaverol ® (off label), Nizoral® (off label)

There are no antifungal creams licensed for use on cats!

Systemic treatment

Griseofulvin - up until very recently has been the only drug licensed, give twice daily with fatty foods. Do not use on pregnant cats. Side effects include anorexia, VD, itching, liver damage, bone marrow suppression, loss of balance. Other (off label) drugs include Nizoral ®, Sporanox ®, Lamisil ®, Lufenuron (Program ®)

Treatment may take 8-14 weeks

When is a cat cured?

The clinical cure is when there are no visible lesions

The mycological cure is after 3 negative cultures, 1 week apart

The clinical cure happens first, so the cat will look cured before it really is

So, what does all this mean?

Cat(s) must be isolated

If no (or inadequate) isolation facilities, consider transferring the cat elsewhere

Disinfect anywhere the cat has been

Dedicate 1 person to care for infected cats

Deal with these cats last in the day

Use separate equipment

Do not move cats until cured

Use disposable litter trays and feeding bowls, towels only for bedding

Discard all soft material, blankets, brushes combs etc.

Use a footbath for going in and out of isolation

Clean and disinfect ALL SURFACES daily with e.g. Virkon ®, Trigene ®, Parvicide ®, Conficlean ®, 1:10 bleach.

Disinfectant wipes are good for wiping hairs up

Handling Griseofulvin

DO NOT handle if pregnant

Wear gloves, a double layer is better

Avoid crushing pills - wear face mask if crushing