Ringworm is the most common transmissible infectious skin disease of animals. It occurs in all species of mammals including cattle & man. (Zoonotic)
Also known as: Dermatophytosis
Etiology
Caused by Trichophyton Verrucosum (responsible for more than 90% of the cases), Microsporum spp. of fungi. Invasion of cutaneous keratinized epithelial cells and hair fibers by dermatophytes.
In dogs, about 70% of ringworm cases are caused by the fungus Microsporum canis, 20% by Microsporum gypseum, and 10% by Trichophyton mentagrophytes.
Epidemiology
Carrier animals are the source; spread is via direct contact or contact with infected inanimate objects. Housed animals most susceptible. The spores of ringworm can remain alive for years in a dry environment, even a barn can remain infective for years.
Clinical Signs
Circumscribed areas of hairless skin; thick gray crumbly crusts (cattle) or shiny, bald areas (horses); heavy pityriasis; common locations where infection likely to contact (e.g., neck, sides).
- Lesions are typically circular, up to 3cm in diameter. Initially, the skin is moist and reddened; later it is dry, scaly and grey.
- Hair loss
- Poor growth
Clinical Pathology
Spores and mycelia in skin scraping, or in culture.
Collection of samples :
For the collection of samples there are two procedures:
1)- By forceps, epilation of hair from areas of active infection.
2)- Scrapings of crust, hair and scale using a scalpel blade.
The material (sample) obtained is collected in a paper envelope, sealed and labeled for transmission to the laboratory.
What If culture is contemplated? : Swabbing the area with 70% alcohol prior to collection may reduce contaminants in the specimen.
Necropsy Lesions
Mycelia : identifiable in skin sections.
Diagnostic confirmation
Laboratory typing of fungus in scraping. (skin scraping test) Microscopic examination reveals the constituents of the fungi on the skin and hair fragment.
Differential diagnoses
- Warts
- bovine herpes mammillitis virus (bovine herpesvirus-2)
- dermatophilosis
- stephanofilariasis
- Lumpy skin disease,
Treatment
"In Accordance with Vet-Endorsed Practices."
Usually heal itself without treatment but take several months. The Topical treatment, application of the medication directly onto the skin lesion, is the common practice. Medications may not penetrate the crusts; the crusts should be removed by brushing or scraping. Scraped mass should be collected & burned to avoid further contamination. Lesions should be treated at least twice, three to five days apart.
Topical application of a 2% solution of iodine, Whitfield’s ointment (also used to treat athlete’s foot in man), or thiabendazole paste are all suitable. Oral griseofulvin may be used but the prolonged treatment and expense of the drug make it impractical in all but valuable animals.
Treatment with imidazole spray may stop progression of lesions and slow the spread to other animals. Chlorine and iodine based compounds are much less effective
Vaccination & Control
Prophylaxis is by vaccination & environmental disinfection.
Disinfectants require high concentrations of chlorine, up to 4%. OR By solution of 1 gallon of household bleach diluted with 3 gallons of water does a good job.
- Reduce the density of animals.
- Increase sunlight exposure.
- Regular disinfection of halters and grooming equipment with bleach or a 4% solution of formaldehyde OR By using cationic alkyl dimethylbenzyl ammonium halides.
- Quarantine all bought-in animals for a minimum of two weeks.
Why ringworm a big deal?
A potential zoonotic disease.
The main loss associated with ringworm is due to the reduced value of the hide and the delay in sending cattle with active lesions to market
References
- https://www.farmhealthonline.com/US/disease-management/cattle-diseases/ringworm/
- https://www.thecattlesite.com/diseaseinfo/233/ringworm-in-cattle#:~:text=Ringworm%20is%20one%20of%20the,mammals%20including%20cattle%20and%20man.
- https://www.extension.purdue.edu/extmedia/VY/VY-56.html
- https://www.msd-animal-health.ie/species/cattle/ringworm/
- Veterinary Medicine, 11th Edition
The Veterinarian 