[chris (OP)]

A friend just came to the door to say that his daughter has ringworm on her face; she's been told she cannot come to college for 2 weeks until it's cleared up.

This seems ridiculous to me.

I thought this would be a useful opportunity to review ringworm infection including how you catch it, how it spreads, where it comes from and how to treat ringworm. This is an open invitation to @SquarishTriangle to give us the veterinary angle too!

[SquarishTriangle]

My understanding is that the numerous spores of ringworm fungus (including Microsporum spp. and Trichophyton spp.) are incredibly easy to spread between animals, and between the animal and the environment. In the environment, the spores are extremely resistant to desiccation and common household disinfectants when used at their normal concentration. So, in a clinical situation, we would consider infected animals to be a serious quarantine risk and would change clothes, disinfect the entire consultation room and all equipment before seeing the next animal. However, ringworm only really seems to clinically infect animals/people who are very young, very old, pregnant or otherwise immune compromised (stress, chemotherapy, corticosteroids etc.) . I have personally handled ringworm lesions with my bare hands numerous times (before making the diagnosis) without ever becoming infected, but I'm not in a high risk group.

I guess if it were a primary school situation, they would be worried about the "very young" population and the close contact between the kids at school. But you said "college", so are these people in their teens to 20s? The daughter could theoretically still carry infectious spores on her clothes and possessions, even once her face looks 100%. So, perhaps this rule is just giving a false sense of security?

Coincidentally, I had to take a ringworm-infected foster kitten back from a human GP yesterday, because we decided that we didn't want to potentially spread ringworm from his home to his patients.

[evan_au]

The first thing to say is that ringworm infection is not caused by a worm.
It is a fungal infection, similar to "athlete's foot".

For a quick overview, start here: https://en.wikipedia.org/wiki/Dermatophytosis

[SquarishTriangle]

What has been your experience in the human hospital setting, Chris?

[chris (OP)]

Alongside other fungal skin infections - or dermatophytoses - ringworm is seen pretty commonly in primary care settings, especially in children. The good news is that it is very easy to diagnose and treat and most people get better within a few weeks with simple topical treatment; Canestan (clotrimazole) cream is available over the counter and very effective.

However, what I would be interested in hearing is what risk infected humans pose to animals?

The detail I left out of the story above is that the girl in question is doing an animal care / management course at college, which includes a practical / hands-on element (which is almost certainly where she got the infection in the first place). But are human to animal transmissions of ringworm documented, or does this tend to be a one-way street?

[SquarishTriangle]

It would depend a bit on the species of fungus, as they can be a little host specific (some more than others), but there seem to be reports of transmission occurring in both directions. There has been a report of Trychophyton rubrum, the species most commonly associated with tinea pedis ('athletes foot') in humans, infecting a cat after the owner frequently rubbed their infected bare feet on the cat. Microsporum canis has also been recorded as being transmitted from humans to pets, although I haven't read the original papers.

For many diseases, animals are more commonly implicated as the source of human infection, rather than the other way around. Although, I tend to think there is a strong bias with these things. Humans naturally don't like to blame themselves for being the "disease carrier". They more commonly seem to blame their pet, even if their own clinical signs appeared first. Most textbooks that describe zoonotic diseases will list various animals as the "reservoirs" of infectious disease, but I've never seen anyone refer to humans as a "reservoir". And "Swine flu" is called swine flu, rather than "human-swine flu". So, when the clinical history is clouded with bias, it makes it harder to tease out what is really happening epidemiologically.

Ringworm lesions in animals tend to be highly variable in appearance, and frequently are not immediately recognisable as there is usually no "ring" and lesions may not even be remotely circular. Often systemic antifungals are required, unless there is only a single, small area affected.

[chris (OP)]

There has been a report of Trychophyton rubrum, the species most commonly associated with tinea pedis ('athletes foot') in humans, infecting a cat after the owner frequently rubbed their infected bare feet on the cat.

You have got to be kidding me?!

Ringworm lesions in animals tend to be highly variable in appearance, and frequently are not immediately recognisable as there is usually no "ring" and lesions may not even be remotely circular. Often systemic antifungals are required, unless there is only a single, small area affected.

So how do they present? Like dandruff?

[SquarishTriangle]

So how do they present? Like dandruff?

Well, sometimes, just some vague, patchy hairloss or thinning. Sometimes itchy, sometimes crusty or flaky, sometimes greasy, sometimes red, sometimes with papules, sometimes fluorescent under UV light. To diagnose it, you either need convincing UV fluorescence, trichograms (hair pluck microscopy), skin scapes (cytology), fungal culture, or all of the above.

[chris (OP)]

To diagnose it, you either need convincing UV fluorescence, trichograms (hair pluck microscopy), skin scapes (cytology), fungal culture, or all of the above.

Are most diagnoses made clinically and the treatment empirical (some antifungal ointment / shampoo) then? I wouldn't think most surgeries have all the gear, or the time, to pursue each case like that?

[SquarishTriangle]

Almost all veterinary surgeries would have a standard light microscope, microscope slides, some basic stains, a Wood's lamp, cotton swabs, and some sticky tape. Some will carry in-house fungal assays (which is usually just commercially prepared Sabouraud's dextrose agar with a pH indicator) to do an initial culture over a week, while others would send the sample directly to the lab.

The nature of veterinary practice is that clients expect a diagnosis on their first visit and they usually want it by spending as little money as possible; which means a lot of testing is done in-house during the space of a normal consultation. On average, in general practice, I would probably be doing microscopy for 50% of medical cases, and other lab work maybe 30% of the time (mostly skin and ear cytology, blood tests, blood smears, faecal exams, and urine exams). I would say that it's standard practice (ie. expected by the veterinary boards) here to do some kind of diagnostic work up, and in an increasingly litigious society, it's wise to have a demonstrable diagnosis behind a treatment plan. It's just a normal part of the day. Time is always an issue... Not everyone would do it that way.

In the cases where clients refuse to spend any money on any diagnostics, then yes, shampoos and creams are used. And the shampoos are usually safe enough to use on an initial treatment trial basis. But the trouble is, if the diagnosis is wrong and the shampoo doesn't help, people get really angry... Or they never come back for a follow up and the animal suffers for a prolonged period of time.

[SquarishTriangle]

I always have to make a sheepish joke about the sticky tape, because it really is the least technical-looking thing I could ever do!

[chris (OP)]

Almost all veterinary surgeries would have a standard light microscope, microscope slides, some basic stains, a Wood's lamp, cotton swabs, and some sticky tape. Some will carry in-house fungal assays (which is usually just commercially prepared Sabouraud's dextrose agar with a pH indicator) to do an initial culture over a week, while others would send the sample directly to the lab.

So do you do that as a "while you wait" service? And would you do that, or do you have someone else who can look at and prep slides while you keep seeing cases? Otherwise don't people end up waiting ages, or are you pretty nifty with a stain and microscope these days?!

[SquarishTriangle]

So do you do that as a "while you wait" service? And would you do that, or do you have someone else who can look at and prep slides while you keep seeing cases? Otherwise don't people end up waiting ages, or are you pretty nifty with a stain and microscope these days?!

We usually have 15 or 20 minute appointments. Or if you work for a cleverly-managed practice, you might be lucky enough to have 30 minute appointments for issues that are known to require multiple tests or long discussions.

I usually just explain that I'll be taking samples to look at under the microscope. After collecting the samples, I'll excuse myself from the consult room for a few minutes while I stain them up, examine them, and hopefully return with an answer and a treatment plan. I really like the time I get to spend looking down the microscope, because I get time to think alone without the client interrupting me with random questions, like how long they should cut their dog's nails...

[Karen W.]

This is interesting be ause I am a person who has had ring worm on multiple occassions my whole life.. as a child I tended to get it every time I was exposed to an infected pet, usually a cat who had picked it up.. At one point a cousin had a bad case and we played together for a couple days, as she had stayed with us. Shortly after, I came down with a couple of them and they were treated with antifungal cream, and were gone in no time at, it it seemed! A few occassions growing up I picked them up again and as Chris said they were easily treated; except when you get them on the scalp. It was harder to treat then, with the hair and all..but they never gave me a shampoo back in the 60's and 70 's.
Now another correlation to this is  that I have a compromised immune system, and have had most of my life, so perhaps that is why I so easily picked it up, I don't know for sure, but I can tell you for myself..if I handle a pet with ringworm, I can pretty much with probably 90% accuracy get it. I am curious if it has an incubation period from point of contact or not?  Is there a way to avoid it if you have had contact short of a antifungal treatment soap, or something, while washing up?
Is there something I can do to be less vulnerable to it?

[Petrochemicals]

Arnt you a doctor Chris, (i appreciate this is 2 years ago,)

[Jessicajohns]

Normally Eczema is not a serious disease. However it may lead to skin infection such as swelling, itching, sometimes leads to inflammation. Hence it is not a curable disease we can get instant relief by following some natural remedies.