cat demonstrating typical lesions of ringworm such as
and hair loss on the face and ears
is an infection caused by a fungus that grows in the superficial
layers of the skin, hair or nails. It has nothing to do with
worms. The scientific name for ringworm infection is dermatophytosis,
and fungi which cause the disease are called dermatophytes.
There are approximately 40 different species of dermatophyte,
each tending to cause infection in particular species of hosts.
In the cat, the cause of more than 90 per cent of cases of
ringworm is the dermatophyte Microsporum canis (M
canis). This organism can also cause infection in many
other species, including dogs and humans. Other dermatophytes
that may occasionally cause ringworm in cats are Trichophyton
mentagrophytes and M persicolor (acquired by
contact with infected wild rodents) and M gypseum, M fulvum and T terrestre (isolated from
do cats become infected with M canis?
is contagious. Spores are the infectious stage of dermatophytes
and are produced by M canis during an infection.
They are typically found in clusters around infected hairs
and can only be seen using a microscope. Infected hairs are
shed into the cat's environment. Cats may become infected
either by direct contact with an infected animal or by exposure
to a contaminated environment or object such as grooming tools,
clippers or bedding. Spores in the environment are very robust
and without treatment can remain infectious for up to two
years. Spores attach to the skin and germinate to produce
hyphae that invade abraided skin and hair. It is not known
how many spores are needed to start an infection. Self-grooming,
particularly licking, may be an effective way of harmlessly
removing spores from the skin and haircoat. Intact skin is
very resistant to infection. Mites and lice are generally
uncommon. The point being made here is that some degree of
self trauma is probably required to enable fungal infection
to develop and that ectoparasite infestation may be an additional
seems to be more common in young cats less than one year old,
and longhaired cats, particularly Persians. The reasons for
this are unknown. It is speculated that young cats may have
immature immune defence mechanisms which limit their ability
to resist infection. In long-haired cats grooming is less
efficient and the skin surface is more protected from exposure
to the sun (which dermatophytes don't like) than in short-haired
does a cat with ringworm look like?
appearance of cats with ringworm is very variable. Some cats
have severe skin disease while other cats have only very minor
lesions or no lesions at all and look completely normal. Typical
skin lesions are discrete, roughly circular areas of hair
loss, particularly on the head, ears or extremities of the
paws. The hairs surrounding affected areas appear broken.
The affected skin is often scaly and may look inflamed. However,
ringworm can look very similar to many other feline skin diseases,
including some of the clinical manifestations of flea allergy
dermatitis, and may present as symmetrical alopecia or even
feline acne. Some loss of hair is usually involved, but the
amount of inflammation, scaling and itchiness (pruritus) can
be very variable.
is ringworm diagnosed?
is impossible to diagnose a cat as having ringworm based on
its appearance alone because this is so variable and can easily
be confused with other skin diseases, or look like a normal
cat. Diagnostic tests are used to confirm the presence of M canis or other dermatophytes. Most veterinary dermatologists
will use at least one of these tests on any cat with skin
disease to investigate the possibility that ringworm might
be involved. There are three tests that can be used to diagnose
ultraviolet Wood's lamp can be used to examine cats
suspected of having ringworm. It is shone onto the haircoat
in a dark room and infected hairs may fluoresce with a characteristic
apple-green colour. The fluorescence is thought to be due
to a metabolite produced by M canis. Unfortunately,
not all dermatophyte species, or varieties of M canis,
fluoresce, so failure to demonstrate fluorescent hairs does
not rule out the possibility of ringworm. In addition, extraneous
substances may cause a similar fluorescence. For these reasons
the results of Wood's lamp examination is not definitive,
but it can provide a very useful method of selecting hairs
for further examination, either by fungal culture or microscopic
examination of suspect hairs can provide a very rapid
positive diagnosis. The observer looks for fungal elements
and spores associated with hairs. Interpretation can be difficult
and it is best performed by an experienced mycologist. It
is not possible to determine which species of dermatophyte
is involved using this method alone. A negative result is
unreliable and may only mean that the sample of hairs examined
was not representative and did not include infected hairs.
culture is the most reliable way of diagnosing ringworm.
Cat hairs are collected and used to inoculate plates of a
special culture medium, which are then incubated in a laboratory.
Hairs for culture can be selected because they are damaged
or closely associated with skin lesions or because they fluoresce
when examined with the Wood's lamp. Hairs are collected from
cats that look completely normal by whole body brushing using
a sterile toothbrush or massage brush. Culture enables precise
identification of the species of dermatophyte involved, but
because dermatophytes are slow growing it may take several
weeks for laboratories to report a result. A positive result
indicates that the cat is infected with ringworm or is carrying
dermatophytes on its coat (due to exposure to an infected
environment). If one cat in a household is diagnosed as having
ringworm then all the other animals will need to be examined,
even if they seem to be completely unaffected. In most cases
all cats in a household will be culture-positive and require
note that the absence of dermatophytes on microscopic examination
of a skin biopsy does not rule out dermatophytosis.
is ringworm treated?
in most healthy cats ringworm infection will resolve spontaneously
after many weeks, treatment is necessary in all cases to speed
this up because of the risk of infection of humans and contact
animals. Some cats will not eliminate infection unless they
are treated. In some cases, prolonged courses of treatment
will be needed to achieve a cure. Treatment can be broken
down into several elements, all of which are essential.
of predisposing conditions
pre-existing skin condition or ectoparasitic infestation (particularly fleas and cheyletiella mites) which causes skin
damage can predispose to ringworm and should be treated specifically.
of the affected animals
affected animals should be treated by administration of both
oral medication (systemic therapy) and by treatment applied
directly to the haircoat and skin (topical therapy).
principal product licensed for veterinary use in the cat is
Itrafungol (Elanco Animal Health), a liquid containing itraconazole.
The recommended regimen is one week of therapy followed by
one week off therapy, repeated for three weeks of treatment.
This approach is used because studies have shown incorporation
of the drug into the skin and slow break down, leading to
a depot effect or build up of the drug. The product is safe
to use in kittens from 10 days of age and caution should be
employed when considering treatment of pregnant queens.
griseofulvin has been the drug most commonly used for the
treatment of dermatophytosis. In recent years, the veterinary
licence has not been renewed for commercial reasons and only
human and farm animal versions are available.
Terbinafine (Lamisil; Sandoz) There are reports of the use of
this expensive product which is used for various
persistent human dermatophyte infections. There is a long
duration of activity and this may allow relatively short courses
of therapy followed by careful monitoring. The recommended
dose in cats is of the order of 10-30 mg/kg per day, with
two to six weeks of therapy. There is a persistent effect
for several further weeks.
Lufenuron (Program; Novartis) Lufenuron is available as a flea
control product. Lufenuron is a very safe product and very
unlikely to cause adverse effects - even at high dosages and
has been investigated as a treatment for ringworm. However,
carefully controlled experimental studies have failed to demonstrate
that lufenuron can prevent dermatophyte infection, or result
in faster resolution of infection, when cats are challenged
by direct inoculation or contact with an infected cat. In
some situations it may be useful as an adjunctive treatment.
therapy can play a very important role in reducing environmental
contamination. Spot therapy with one of the human anti-fungal
creams is not recommended because the area of infected skin
is often considerably wider than the skin lesions might suggest.
Topical therapy is best applied to the whole body by either
shampooing or dipping. Clipping of cats will make this much
easier, particularly for long-haired cats, and also reduce
environmental contamination. Clipping should be done with
care to avoid traumatising the skin, as this can spread infection
and make the skin lesions look worse for a short time. It
is advisable to repeat clipping several weeks after the start
of treatment with systemic agents, as by this time the drug
should be incorporated into the hair. If whole body clipping
is not chosen then local clipping around the lesions should
be done with care. It is recommended that clipping should
extend 6 cm around visible lesions. It is normally necessary
to sedate cats to clip them safely. Infected hair should be
disposed of by burning and clippers should be disinfected
only product licensed for the topical treatment of ringworm
in cats is a chlorhexidine and miconazole shampoo (Malaseb: Leo Laboratories).
It is usually applied twice a week. The coat is first completely
wetted and the shampoo is then lathered on and massaged well
down into the skin. The shampoo is left in contact with the
skin for 10 minutes (timed with a clock) before rinsing. Most
cats tolerate this remarkably well. Leo Laboratories have
produced a leaflet giving tips about shampooing cats. The
shampoo should be used with caution around the eyes and if
shampoo enters the eye it should immediately be rinsed with
large amounts of clean warm water. In order to obtain a veterinary
licence a product has to be both effective and safe and, unless
there is a very good reason for not doing so, such products
should be used in preference to unlicensed products. Other
products which may be suggested for topical therapy, but which
are not specifically licensed for use in cats, include:
Enilconazole (Imaverol; Elanco Animal Health) is used as a dip. It is
licensed for use in dogs, horses and cattle. There have been
some reports of cats suffering fatal toxic reactions following
its use. These have not been well documented. Limited experimental
work has failed to reproduce these effects. Enilconazole appears
to be effective at killing M canis spores on hairs.
Owners who decide to use Imaverol will be doing so at their
own risk. To reduce the risk of toxicity it is recommended
that cats have an Elizabethan collar fitted following dipping
until the coat has dried.
Chlorhexidine (eg, Hibiscrub) - recent studies suggest that some
other products, such as Malaseb, may be better at killing M canis spores on hairs.
Virkon (Germicidal skin cleanser; Antec) may be useful
as a topical treatment. It is applied as a spray or dip and
then rinsed off after 10 minutes. It is not a licensed veterinary
of the environment and objects
is much easier if infected cats can be restricted to one easily
cleanable room and this will reduce human exposure to the
cats and sources of infection. All areas of the house to which
infected animals have had access will require decontamination,
but the majority of effort can then be concentrated on the
room in which the cats are confined.
contaminated objects such as collars, baskets, igloos, bedding,
soft toys and grooming tools which cannot be disinfected should
be disposed of, preferably by burning. Cardboard boxes can
be used as temporary disposable beds and these should be disposed
of at least once a week.
source of environmental contamination is fungal spores on
shed hairs. The amount of contamination can be reduced by
topical therapy and clipping as discussed above.
is achieved by a combination of two approaches: physically
removing the infected hairs from the environment and the use
of chemical agents in the environment to kill the spores.
appearance of a ringworm-infected hair demonstrating
the presence of numerous tiny spores around the outside
of hair and hyphae invading the hair
vacuuming of contaminated rooms and/or cages on a daily basis
is recommended. Vacuum cleaners with a beating action are
best for cleaning spores from carpets. Heating and ventilation
ducts and fans often become contaminated and should be vacuumed.
Vacuum bags should be disposed of by burning. Under suitable
circumstances a blow-lamp can be used to burn hairs off wire
runs and cages. Steam cleaning is of limited use because the
temperature of water that contacts the item being cleaned
is unlikely to be sufficient to kill spores.
disinfectants that claim to be effective against dermatophytes
do not have very good activity against M canis spores on hairs. Recent experimental work has demonstrated
that there are two products that do work. These may not be
suitable for use on carpets and other soft furnishings.
- Bleach. The stronger the better,
but dilutions up to 1 in 10 of household bleach with
water have been shown to be adequate. Use for washing
all hard surfaces (floors, worktops, litter trays and
cages) at least twice a week.
- Virkon (Antec) is a disinfectant powder that
is made up with water to a 1 per cent solution. Use for
washing all hard surfaces at least twice a week.
regimes in particular cases
single cat household
affecting a cat in a single cat household is usually relatively
easily contained and managed. The problem of infection being
transmitted to humans is an important issue as in any outbreak
of M canis infection. However, once the cat is on
a programme of treatment and environmental contamination is
carried out the problem will usually resolve within a couple
situation where there is an outbreak in a multi-cat household
is very different, particularly if longhaired cats are infected
in a domestic environment. All cats in the unit could be tested
by fungal culture to identify those which are infected. However,
it is usual to find that all in-contact cats are culture-positive
and clearance is most rapidly achieved by treating all the
cats from the outset. In any case, separation and isolation
of cats is frequently impossible so treatment of all the cats
in the unit is the only practical option. If culture-negative
cats are separated this should be to an uncontaminated environment
and topical therapy is recommended, as is intermittent monitoring
by fungal culture. When cats on full treatment become culture-negative, ideally they should be kept as a third group until
a second or third consecutive negative culture result confirms
the permanence of this state. Complete resolution of the problem
can take from months to years and be very time consuming and
expensive to achieve. However, with commitment and determination
this is achievable. Throughout the period of infection the
household should be isolated, no cats should enter or leave
and breeding should cease.
are no systemic agents that can safely be used in pregnancy.
Queens should be isolated from other cats and clipped and
treated topically twice a week. Once the kittens are born
the itraconazole can be added to the regime from 10 days of
therapy can be used from about four weeks of age, taking special
care to keep the kitten warm when wet. Kittens should not
be rehomed until two negative fungal cultures have been obtained
at intervals of two weeks. The need to reduce direct contact
with kittens, particularly by children, to avoid human infection
should be stressed.
long will it take for cats to get better?
should be continued until all of the affected animals have
recovered and are negative on fungal cultures. Skin lesions
will often resolve before the cats have eliminated the fungal
infection, so it is necessary to monitor progress by taking
hair samples (whole body brushing) for fungal culture. If
treatment is stopped prematurely the ringworm may seem to
recur after a time, although in fact it was never eliminated.
In most cases cats will need treatment for a minimum of six
weeks and in some cases much longer. Typically, the more cats
in a household, the harder it is to resolve the problem.
cats are an important potential source of ringworm. To prevent
the introduction of M canis into a house or cattery,
new cats should be sampled for fungal culture and isolated
until the results of this are known. Any situations where
there is mixing with unknown cats carries a risk of exposure
to dermatophyte spores, even if there is no direct contact
between cats. Cat shows are a common example of this. There
should be no sharing of grooming equipment with other exhibitors
at shows. Bathing, spraying or dipping using an antifungal
agent after a show is the best available means of preventing
any dermatophyte spores on a cat from starting an infection.
Similar precautions should be taken whenever a cat returns
to the cattery from anywhere where direct or indirect contact
with other cats is a possibility, eg, other catteries or the
veterinary surgery. Although ringworm is dreaded by cat breeders,
by taking sensible precautions and using good husbandry it
can be avoided.
infection on human skin
canis infection in humans
can easily be spread from cats to people. Children are particularly
at risk. Direct contact with infected animals should be minimised.
Gloves and protective clothing should be worn when administering
treatment. Efficient environmental decontamination will reduce
exposure to dermatophyte spores. Dermatophytosis in humans
presents as circular patches of thickened, inflamed skin or
hair loss with scaling. These may be itchy. Lesions may occur
anywhere on the skin or scalp. If any skin lesions develop
the family doctor should be consulted. Ringworm in humans
usually responds well to treatment.
Governing Council of the Cat Fancy (GCCF) and ringworm
understanding of procedures regarding cat showing and breeding
required by the GCCF following notification or identification
of ringworm in a cat and the reasons for this is helpful.
If any skin lesions (remember that ringworm may be associated
with any type of skin lesion) are noted when a cat is presented
for vetting in at a show it can be given a section D rejection.
The exhibitor will then not be allowed to exhibit any cat
at that show or to attend the show. The cat should be presented
within seven days for a veterinary examination and fungal
culture. Until the results of the culture are known exhibition
or attendance at shows is prohibited. If the culture is negative
then a clearance certificate is given. If the culture is positive
or an owner self-reports that a cat has ringworm, then the
GCCF requires that all cats in the unit are presented for
veterinary examination, microscopic examination of hairs and
fungal culture from whole body brushings. No cats are allowed
in or out of the unit and all breeding should cease. The owner
is not allowed to exhibit at or attend cat shows or meetings.
These conditions remain in force until a clearance certificate
is issued. This will only happen when there are negative culture
results from two sets of tests taken eight weeks apart for
all the cats in the unit. Following the first negative result
no topical therapy should be used. This regime may seem harsh
but it is necessary to ensure that ringworm has been completely
eradicated and that cats are unlikely to pose a risk to other
cats or people.
the FAB office (01747 871 872) or e-mail firstname.lastname@example.org for contact details.