Ask the Vet

By Dr. Ken McMillan
DTN Contributing Editor

QUESTION:

I have a problem with ringworm in my feeder calves when I wean them in the fall. They are fine until I wean them, so I think they are being exposed to ringworm in the corrals and barns. What can I do to stop this cycle?

ANSWER:

It's important to remember ringworm spores can exist in the environment for months or even years. The first step in suspected cases of ringworm is to confirm that it is actually ringworm, then to evaluate individual affected animals and overall herd health. Treatment should initially focus on correcting any underlying health issues, including treatment for lice and other external parasites. In many cases, skin issues resolve without specific treatment for ringworm.

The only practical treatment of ringworm on cattle involves topical antifungal products. Various solutions, including Betadine, chlorhexidine and dilute bleach, as well as antifungal ointments, are used. For these to be effective, however, crusts and scales overlying the active infection must be removed by brushing, scraping or scrubbing. Merely spraying an antifungal on the animal does not produce consistent results. This essentially limits treatment to cattle that are easily handled like show or dairy animals. Stockers would certainly not fit into that category.

The first step in environmental treatment is to the remove any sharp or rough metal or wood that can cut, scrap or abrade skin. Fencing, trees, alleyways, chutes, halters, grooming equipment and tack used with horses can be sources of ringworm. Many products are labeled to treat ringworm in the environment, but several recent studies have shown they are not effective in barns and outside areas. These products were "proved" using a test tube or ringworm organisms, not in real-world situations.

On farms, many areas have organic material that protects ringworm organisms. It is important to remove as much of this material as possible by scrubbing with detergents and/or pressure washing. Steam pressure washing is better but does not consistently kill ringworm. After cleaning the areas, a few disinfectants have been shown to be effective.

Household bleach used at concentrations of at least 1:32 (½ cup per gallon of water) is the most available option. Other effective products include Virkon S (a detergent-peroxide-based product) and an accelerated hydrogen peroxide such as the Rescue line of products. An environmental spray containing enilconazole was also found to be effective. Any potentially contaminated area should be thoroughly sprayed and may even need repeat treatments.

(SK)

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