Ringworm in cats is caused by ringworm fungi (dermatophytes), in the vast majority of cases by Miocrosporum (M.) canis.
Cats often spread the infection without showing symptoms themselves, and a single seemingly completely unaffected cat can infect an entire herd.
Fungal spores are dispersed into the environment, where they can live for months to years.
The clearest and most common clinical signs of feline ringworm include the following: circular areas of hair loss, broken and stubbly hair, scaling or crusty skin, alterations in hair or skin color, inflamed areas of skin, excessive grooming and scratching, infected claws or nail beds, and dandruff.
Cleaning up ringworm infestation in a home and in a group of cats is costly, demanding, and takes time. Under normal circumstances, however, it is not impossible to implement, if you invest wholeheartedly, plan, and carefully think through all the steps that need to be carried out. In total, a ringworm cleanup usually takes between two and six months to complete. The time varies depending on how many cats you have, how many have been infected, the age of the cats, any pregnant cats, and how the premises to be cleaned look like (for example, a home environment with textiles that can hide spores very well compared to tiled walls and stainless steel cages steel).
A successful cleanup requires:
- A strategic sampling of all cats.
- A careful environmental cleaning ensures the cats are not re-infected from the environment.
- External treatment in combination with general treatment. External treatment (including bathing) reduces the spread of spores. General treatment (medicine given by mouth) speeds healing.
- Preventive measures to prevent infection from re-entering the herd.
- Contact a treating veterinarian with an interest in skin diseases in cats for investigation and treatment of your/your cats.
Strategic sampling
- Culture samples are taken from all cats, even those without symptoms. Sample response time varies between one to two weeks depending on how fast the ringworm fungus grows.
- The fact that ringworm fungus is not found in a cultivation is no guarantee that the cat is free from ringworm. In order to make sure as much as possible that a cat is free of ringworm, you should take at least two, preferably three, samples with at least a week between the samples. If none of the samples show fungal growth and the cat has not been exposed to infection during and after the sampling period, the cat may be free of ringworm.
- It is important that the laboratory can answer which type of ringworm fungus it is dealing with, because it determines whether and how decontamination should be carried out. See also the document Ringworm (dermatophytosis) in cats.
- Pending test results, cats that appear to be infected, or are suspected of being infected, must be isolated in a space that can be disinfected. For hygiene measures when staying in the isolation room, read under treatment of the cats below.
Decontamination of the Environment?
Environmental remediation of ringworm infestation is usually costly, laborious, and time-consuming, but it is necessary to remove the infection. Infected cats' fur is full of spores that spread everywhere. Spores in the environment are a very important cause of poor treatment results and reinfection. Above all, this applies to infection with M. canis, as this type seems to release more spores into the environment than T. mentagrophytes.
Good planning is essential; how should the cats be grouped, isolated, and moved around and how should each room be cleaned and disinfected? Discuss the plan with your attending veterinarian before the cleanup begins.
- All rooms including those used as insulation must be sanitized.
- Clean or throw away (burn) cat brushes, cages, and the like. Wash at 60ºC and use disinfectant.
- High-pressure washing with hot water is good if you have the opportunity/access to it.
- All textiles, including for example curtains, clothes, and blankets are washed. 43.3ºC is given as the temperature at which spores are killed. However, washing at 60ºC is recommended, as one should have a safety margin so that entire textiles are exposed to a sufficiently high temperature for a long enough time. The mechanical effect in the form of rinsing/rinsing is also important in addition to the temperature.
- Vacuum all surfaces, preferably every day. Burn the vacuum cleaner bag every time. If this is not possible, spray it and seal it well and throw it in the garbage. Make sure that the filter in the vacuum cleaner is intact so that spores do not come out of the vacuum cleaner again. A central vacuum cleaner is an advantage if available. Clean/disinfect the vacuum cleaner brush carefully between vacuums.
- Clean surfaces, walls, moldings, and floors at least once a week!
Don't forget to clean the underside of table tops/benches, inside drawers, behind the element, car, and more. - Disinfectants are also used in connection with cleaning. Ask your veterinarian which agent(s) is best suited for your type of cat behavior. However, always check that the agent really kills fungal spores. Some agents that state that they are effective against fungi do not take the spores very well. Sometimes special guidelines are specified for specific spores, then follow these. Before using disinfectants, all surfaces must be properly cleaned, the agents have a worse effect on dirty surfaces.
- Carpets often have to be removed as they are basically impossible to get rid of spores.
- Repeat the parts of the environmental cleanup where there are no time indications once per month for the entire treatment period.
Ringworm-free group: Asymptomatic cats, that are culture negative (that is, no ringworm fungus could be detected on culture).
Bathe with means prescribed by the veterinarian. The cat must wear a collar so that it does not get to lick the fur before it has dried. Repeat the baths one to two times per week.
Infected group: Cats with symptoms, as well as culture-positive cats (that is, ringworm fungus grew in the culture sample).
- Must be isolated in small groups or kept individually.
- Shave the fur, and burn the hair. If there is no possibility of burning the hair, it should be soaked in disinfectant and packaged very well sealed before it is thrown in the garbage. The use of disposable gloves and protective clothing is recommended when clipping the infected animal. The cutting should be done in a well-ventilated room that can be disinfected afterward.
Mechanical scissors can be difficult to clean and disinfect properly and they can cause damage to the skin that can worsen the infection. An ordinary pair of scissors is easy to clean, but cutting a recalcitrant cat using ordinary scissors can both give rise to major injuries and be practically impractical. A professional groomer, for example at a veterinary clinic/reception/animal hospital, can be helpful. Many clippers can be set to "stump cut" so that the risk of skin damage is minimized. PLEASE NOTE, that the person who will receive one or more cats for clipping must be informed about the ringworm infection beforehand, so that measures to prevent the spread of infection to other, perhaps sick and particularly susceptible cats can be prevented. - Bathe with means prescribed by the veterinarian. The cat must wear a collar so that it does not get to lick the fur before it has dried. Repeat the baths twice a week.
- Start general treatment in the form of tablets, capsules, or a mixture prescribed by the attending veterinarian. Tell your vet if the cat is pregnant, as this affects the choice of preparation.
- Use protective clothing, including shoe and hair protection in the isolation area, and wash hands thoroughly before and after staying in the area. Ask the pharmacy, for example, if they can recommend a hand disinfectant as a supplement. Disposable gloves can also be helpful.
- New culture samples are taken from all cats, for example, three to four weeks after treatment has begun. After that, samples for follow-up can be taken at intervals of two to four weeks.
- Asymptomatic cats that have become culture-negative during treatment (and have been culture-negative on at least two, preferably three, sampling occasions in a row with at least one week between samplings) are released to the ringworm-free cats after they have been bathed one last time in some kind of lock between isolated and non-isolated cats.If the culture from a cat does not show infection (that is, the test result is negative) in test one, but fungus grows in test two, the cat is still considered infected even if a third test is negative. Continued sampling is thus required.
- Treatment in the infected group continues until all cats are symptom-free and culture-negative according to the point above.
Cats that never become culture negative:
Review the treatment strategy/technique/environmental remediation.
Keep the cat isolated (it can easily reinfect the entire cattery again)!
Unfortunately, euthanasia may have to be considered, if constant re-infection cannot be accepted.
You can tell that your cat has recovered when the skin clears up. Any marks should leave, and you'll notice the re-growth of your cat's hair. If you're dealing with a severe case, you may need to take your cat back to the vet every 2 weeks so a culture sample can be taken.
- New cats to be brought into a herd should always be quarantined for two to four weeks due to the risk of infection; not only with regard to ringworm. Please note that asymptomatic cats with ringworm infection, which have been bathed with shampoo effective against ringworm before coming to the new home, may have a delayed onset of symptoms. It may then happen that you discover that the cat is infected only after the quarantine period has expired.
- Use protective clothing, including shoe and hair protection in the isolation area, and wash hands thoroughly before and after staying in the area. Ask the pharmacy, for example, if they can recommend a hand disinfectant as a supplement. Disposable gloves can also be helpful.
- If it is suspected that the animal may be a carrier of ringworm, a culture sample must be taken. Initiation of treatment may be relevant even before the test result is received, talk to the treating veterinarian. Leave the cat(s) in isolation until the cultural response is clear (and negative). The fact that mushrooms cannot be found in the cultivation is no guarantee that the cat is free from ringworm infection.
- In the event of a positive response to culture (that is, ringworm fungus grows in the culture sample), measures are taken against infection and the spread of infection in consultation with the attending veterinarian.
