Ringworm on dogs is fairly uncommon and develops when your dog's hair and skin becomes infected with the ringworm fungus.
Probably the most common type of ringworm fungus that affect dogs and puppies is a type known as Microsporum canis and a common way for the fungal infection to be passed to dogs is through another pet in the same property transmitting it to your pooch (often cats pass the infection to the dog - but it can also be seen in humans too, just look at the picture above).
What does Ringworm look like...? The characteristic 'ring' will occur when the infected hairs become weak and then start to break off at the roots causing the localised hair loss - leaving completely bald area free of hair.
Another type of ringworm fungus that can affect dogs and puppies is Trichophyton - other versions of this fungus can affect cattle, horses, rodents and even hedgehogs. This type of fungus can then be transmitted to dogs and humans if they come into contact with the infected animals.
Causes & symptoms of ringworm on dogs... The fungal ringworm spores are often found on the carpet, soil, toys and after being transmitted to your dog the infection will normally start to affect the head area (as you can see in the image above) and will then start to affect other parts of the body including the legs. The affected areas can then start to get larger and may become infected.
The fungal infection is actually not particularly itchy when the hair falls out - however as secondary infections start to take hold the area can become very itchy causing your dog to scratch the affected area which will perpetuate the symptoms causing more redness, hair loss and making the whole infected area much worst. After secondary infection has started the affected area can become crusty and scabby.
Ringworm on dogs is not just found on the skin area as it can infect and get beneath your dog or puppy's nails - this will leave the nails dry and more prone to breakage.
The fungal spores that cause the infection are very capable of surviving for some length of time in most environments (they can survive for up to twelve months before dying). To prevent your dog becoming infected you should wash any bedding, sterilize grooming tools, wash the floor, get rid of toys and vacuum the carpet - this will help to get rid of any spores that might be lying around. Remember that most dogs do have some resistance to the ringworm spores - but if you suspect tht your dog has been infected take him or her to the vet.
Dogs that are on certain steroids (over vaccinated) or have an immune system that has been suppressed for whatever reason are more prone to the condition.
Diagnosis & Treatment for ringworm on dogs... Most ringworm infections that have been caused by Microsporum will light up be fluorescent under a 'wood Lamp' this is not always the most accurate method to diagnose the condition as ringworm can be very similar in appearance to a number of other medical conditions (in fact when the bald areas become infected with secondary infections the condition can look very similar to demodectic mange).
If when the Wood lamp is used and the affected area does not appear fluorescent or if an accurate diagnosis and confirmation is needed then hair samples maybe taken to be examined and cultured in laboratory conditions. It might be possible to diagnose whether the hair sample has been invaded by the fungal spores (ringworm) but through the spores being cultured and allowed to grow (under laboratory conditions) after two to three weeks it will be able to tell if the hair samples have ringworm.
Although it is not always neccessary, by getting a confirmed diagnosis it will determine whether ringworm is present and therefore contagious to humans.
If you suspect that your dog has ringworm (you should take your dog to the vet) and you will need to be very careful when handling your dog (you should always wear gloves to protect your hands). The vet will normally cut and trim the area around the lesion - the skin will need to be thoroughly cleaned with an antifungal wash - any hair clippings should be disposed of and burnt.
Most cases of ringworm on dogs and puppies may heal on their own. However in more severe cases then a vet may prescribe a specific treatment. If your dog has a mild case of ringworm then the vet might prescribe an antifungal ointment or lotion which may treat the lesions and a secondary ointment (something like Griseofulvin) will be used to treat the fungal infection. However, more recent treatments will involve the vet prescribing Miconazole or Lotrimin ointment or cream. In more severe cases the vet may recommend an antifungal shampoo or dip alongside the antifungal topical treatments.
The vet may also brush your dog's coat to see if any further spores are present - several more tests under a Woods Lamp every two weeks will determine whether the treatment has worked.