Fungal Culture for Ringworm in Dogs and Cats

Fungal culture is the lab test used to confirm ringworm in dogs and cats. Hair and skin scale from the affected patch are placed on a special growth plate, and the lab watches to see whether the ringworm fungus grows. Fungi grow slowly, so the result takes longer than most other tests. Ringworm can also pass to people.

What is ringworm, and does it need a lab test?

Ringworm is not a worm. It is a fungus that lives in the hair, skin and sometimes the claws. Common signs are round or uneven patches of hair loss, flaky or crusty skin and hairs that look broken off. Some pets itch a little, and some hardly seem bothered.

Many other skin problems look the same, including mange, bacterial infection and allergy. Even a vet cannot always tell them apart by eye, so a lab test helps. A registered veterinarian reads the result together with the pet's signs and history.

Ringworm can pass from dogs and cats to people, so handle affected pets with care. Wash your hands after touching the pet, wear gloves when handling the affected skin or the sample, and speak to a doctor if you or a family member get an itchy, ring-shaped patch.

How are hair and scale samples collected?

The vet usually takes the sample, though you may be shown how. Hairs are pulled gently from the edge of the patch, where the fungus is most active, using clean tweezers. Flakes of scale and crust are collected too. Some vets also comb or brush the coat with a clean tool and send what is collected.

Place the sample in a clean, dry container or a paper envelope, label it with the pet's name, and keep it dry. Please do not wash the patch or apply cream just before collection, and tell your vet about any skin medicine already used. These things can hide the fungus and give a false negative result.

Why is a fungal culture slow?

In a Fungal Culture, the sample is placed on a plate with food that suits fungi, and the plate is kept in a warm, controlled place. Ringworm fungi grow much more slowly than bacteria. The lab must wait, watch the plate and then look at the growth under the microscope to confirm what it is.

So the culture is not a quick test, and it is not meant to be. The lab confirms the reporting time when you book. While you wait, your vet may act on the signs and on the quicker tests below, and will tell you what to do about the pet and the home.

Which quicker tests come first?

Several simpler tests are often done alongside the culture or before it.

• A Fungus Examination Routine looks at hair and scale under the microscope for signs of fungus. It is quicker than a culture, but it can miss the fungus, so a negative result does not rule ringworm out.
• A Skin Impression Smear Cytology shows bacteria, yeast and inflammatory cells on the skin. It helps the vet see whether another infection is present, perhaps on top of the ringworm.
• A Skin Scraping (Mange Mite Examination) checks for mites, which can cause patches that look very much like ringworm.

Each test answers a different question. Your vet decides which ones your pet needs.

What does a negative culture mean?

A negative culture means that no ringworm fungus grew from that sample. It does not always mean the pet is free of ringworm. The sample may have missed the fungus, may have been taken after a wash or cream, or may have held too little to grow. If the signs still fit, the vet may repeat the culture or add another test.

A positive culture, read with the signs, supports a diagnosis of ringworm. The vet then decides on the next steps for the pet. Because the fungus can spread on bedding, brushes and hands, the vet may also talk to you about cleaning and about keeping other pets and children away from the patch. Please follow that advice and do not start medicines on your own.

Read next

If your pet is scratching and you are not sure whether the cause is a fungus, mites or something else, Itchy Pets: Skin Scrapings, Ringworm and Ear Tests walks through which skin tests answer which question. When the trouble looks like a bacterial infection, Skin Culture and Sensitivity: When a Skin Infection Needs a Culture explains how a germ is grown and checked against medicines.

Testing in Bhopal

Bring the dry hair and scale sample to C-200, C Sector, Shahpura in Bhopal, or ask for free collection from your home anywhere in the city. If you live in another district, send the sample by courier or bus parcel, or hand it to your own vet. Call or WhatsApp +91 88175 01118 and the lab confirms the method, sample needs and reporting time when you book.