Ringworm is a fungal infection of the skin of all domestic animals (cattle, horses, mules, donkeys, pigs, dogs, cats and camels) and humans. It is NOT a worm infection!
It is caused by Trichophyton and Microsporum spp. The disease occurs worldwide.
Mode of spread
The infection is spread by direct or indirect contact. Licking with the tongue spreads the fungus.
Spores of the fungi can survive for prolonged periods off the host, however, and infection can arise from contact with contaminated stalls, ropes, utensils, etc.
Spores can also survive on animals without necessarily causing disease and such "carrier" animals are another source of infection.
It is more common where animals are housed or kept in close proximity to one another. A high humidity is known to be conducive to multiplication of the fungus. Animal susceptibility is largely determined by immunological status so young animals are most susceptible. Nutritional status may play a part, as may dietary deficiencies.
Transmission between species readily occurs and in rural areas 80% of cases of human ringworm are derived from animals.
Ringworm fungi only grow in keratinized tissue and advancing infection stops on reaching living cells or inflamed tissue. The fungi require oxygen and die out in the centre of the lesion leaving only the edge active. It is this mode of growth which produces the characteristic ring form of the lesions.
Generally speaking the disease is minor in its effect on the affected animal and little economic loss is incurred.
Zebu breeds appear to be less commonly affected than European breeds.
Signs of Ringworm
- Animals develop symptoms of ringworm 7 - 28 days after infection.
- Animals have a circular scab on the skin about 3 cm across. Scabs usually appear first around the nose, above and around the eyes, on the ears or under the tail. The skin under the dry scab is wet. Scabs soon join together and become thicker.
- After several days the scabs fall off. The skin underneath becomes dry with a heavy, gray-white crust raised above the skin.
- Animals do not scratch when they have ringworm. But they sometimes scratch if bacteria infect the scabs.
- The scabs fall off after a few weeks and leave patches with no hair.
- Animals slowly recover even without treatment. The hair grows back in about three months.
Prevention and control
- Isolate and treat animals with ringworm
- Failure to control an outbreak of ringworm is usually due to the widespread contamination of the environment before treatment is attempted.
- Use disinfectants to clean contaminated places and equipment before using them for healthy animals. Direct sunlight kills ringworm fungi.
- An attenuated fungal vaccine is available in some European countries and it has prevented the development of severe clinical lesions and greatly reduced the incidence of zoonotic disease in animal care workers. But vaccinated animals continue to shed spores for some time after vaccination and it is expensive.
- Animals that recover from ringworm do not usually get the disease again.
Animals usually recover spontaneously from ringworm with no treatment but it may take 2 - 3 months. They recover sooner when it is dry and sunny. The main advantage of any treatment is to prevent the extension of recent lesions and to limit the spread of infective material. Treatment greatly reduces contamination of the environment and as such is to be encouraged. To help recovery:
- Shave the hair around the place with ringworm. Burn the hair you have shaved off because it is infected.
- Scrape the scabs off gently using soapy water and a brush.
- Put antiseptic on the affected areas. Betadine povidone- iodine, Whitfield's ointment and chlorhexadine are effective. Animals treated like this can recover in 2 - 3 weeks.
- Give griseofulvin by mouth or apply to the affected area. Individual animals can be treated with miconazole or clotrimazole lotions. These medicines are expensive but animals treated with them start to recover in about 10 days
Common traditional practices
- Kipsigis (cattle): Crush a handful of Mexican marigold (stem, leaves and flowers) with a stone so the juice comes out. Collect the juice and rub on the affected spots once a day for 3 days.
- Luo (camels, cattle, donkeys, goats, sheep): Pound a handful of Otange leaves to powder and mix with half a cup of ghee. Smear on the affected skin until the patches disappear.
(Source: ITDG and IIRR, 1996)