Pets infected by ringworm do not show symptoms. Thus, they remain as carriers, who infect other pets with the ringworm fungus. Around 95% of the ringworm infections in pets are due to three fungi species, namely, Trichophyton mentagrophytes, Microsporum gypseum and Microsporum canis. Despite the usually asymptomatic nature of ringworm in pets, veterinarians can use several tests to identify the infection as well as the species of the fungi.
Microscopic Test:
The veterinarian will take hair sample from the infected area and place it into a staining solution. The vet then views this under a microscope. The spores of the fungus may be visible on the hair shafts itself. This technique successfully identifies the infection in 40% to 70% of the cases. However, it cannot provide the vet with the type of fungus.
Culture Test:
This is the most time-consuming, but effective method of determining the presence of ringworm on pets. The vet takes either hair from the pet or fungal spores from the hair using a toothbrush or other appropriate tool. He/she then cultures this fungus. After culturing, the vet reads it under a microscope. Alternatively, the vet can send the culture to a pathological lab for reading. This test also identifies the type of fungus that caused the ringworm.
Woods Test:
This test uses ultraviolet light along with a microscope. Only half of the Microsporum canis will be visible in an apple-green fluorescent color on the shafts of the hair. This fluorescence is not the fungus. It is the excretion of the actual fungus. Infected skin also does not show up as fluorescence.
Microsporum canis affects mostly cats. Microsporum gypseum affects humans, dogs, rodents, cats, cattle, swine and horses. Trichophyton mentagrophytes affects mainly rodents, besides horses, dogs and pet rabbits. Simply identifying the fungus type in a pet infection can be useful in preventing the spread of the ringworm.