Duane Miksch, Food Animal Extension Veterinarian, University of Kentucky
(Previously published online as Vet 30, Agriculture Veterinary Publications)
Club Lamb Fungus Disease is of increasing concern in exhibited sheep. It is highly contagious in fitted sheep, and also is easily transmitted to people who groom and care for sheep.
Club Lamb Fungus Disease is an atypical moist ringworm of sheep. It has sometimes been referred to as lumpy wool, which is a misnomer, because lumpy wool is a skin disease caused by a species of filamentous bacteria that also causes strawberry footrot. Lumpy wool occurs frequently in Africa, Europe, and Australia, but not in North America.
A better understanding of Club Lamb Fungus Disease and the conditions that favor its spread willhelp you keep your sheep and yourself free of this serious fungal skin disease.
Cause of the Disease
The club lamb fungus, Trichophyton verrucosum, is apparently a variant of T. verrucosum, the fungus that causes ringworm of cattle. Ringworm fungi are referred to as dermatophytes (plants that grow and produce lesions on animal skin). They are unique fungi for two reasons: they cause contagious infections and they require keratin as a nutrient source. Keratin is the principal protein of the skin surface, and of hair and wool.
The diseases caused by dermatophytes are generally referred to as ringworm (from the circular nature of the lesion) or tinea (from the Latin word for the clothes moth, whose feeding habits result in circular holes in woolen cloth).
Nature of the Disease
Trichophyton verrucosum enters the skin through abrasions or other disruptions of cells in the surface layer. The fungal spore germinates and fungal filaments invade the walls of hair or wool follicles. They then grow downward between the shaft of hair (or wool) and the wall of the follicle. As the hair or wool grows, the fungal elements are carried out of the follicle and above the skin surface. Many of these hairs fall out or are broken off.
The fungal invasion spreads outward in a circular pattern, resulting in a ring-shaped lesion. The greatest inflammatory response is at the outer edge of the circle.
The fungus does not invade living skin, but its presence in the dead layers provokes an active inflammation of the underlying living layers. This provides a favorable environment for invasion of living tissues by secondary bacterial infections.
There are usually a number of separate lesions. Except initially, there is rarely a solitary lesion, and generalized body involvement is also rare. Individual lesions vary considerably in size.
The progress of the disease involves matting of wool, followed by loss of wool, scaling, and crusting. Early lesions may not be readily seen, but the thickened nodules can be felt. There is usually little evidence of itching. However, infected sheep will rub along fences and feed bunks, contaminating the structures with fungal spores.
Spread of the Disease
Dermatophyte infections are seen mostly in young animals with immature immune systems that are kept in close contact. High humidity, high environmental temperature, and insults to the skin are common predisposing factors. Abrasions from clippers, brushes, and other grooming activities are therefore important influences in the occurrence and spread.
Transmission of ringworm is usually from animal to animal by direct contact or indirectly through people’s hands, grooming tools, blankets, walls, fences, or feed bunks.
Club lambs are especially susceptible to ringworm because they are frequently subjected to washing and clipping. Lanolin, the natural oil of the wool, may be a defense to invasion by the fungus; much of it is removed in washing. Close clipping tends to abrade the skin and aid in spreading the disease.
Lesions appear in 1 to 6 weeks (typically about 2 weeks) after the animal comes in contact with the fungus. The fungus will grow and spread over the skin for the next 2 to 8 weeks. After 4 to 12 weeks the lamb’s immune system will respond sufficiently to clear up the infection. The recovered lamb will be resistant to reinfection, usually immune for life.
While the fungus is active the infected lamb will rub on posts, gates, feed bunks, and walls. The fungal spores deposited on these objects may remain infective, keeping the premises contaminated if untreated. Lambs chewing on boards may provide moisture needed to nurture the fungus and allow it to live in pens for prolonged periods.
Spores that contaminate buildings may be the most important means by which the infection is maintained from one season to the next. The spores will survive freezing but are killed by drying and by heating to 125° F.
The club lamb fungus is readily transmitted to people who groom or care for sheep. The lesions in people are reported to be more severe than those caused by ringworm of cattle.
Here are a few tips for prevention:
- Wear gloves when handling infected sheep, or using contaminated equipment, or working in a contaminated environment, as they offer a measure of protection.
- Wash your hands, arms, and other exposed body areas with an iodine soap or a 10% chlorine bleach solution (1 part bleach to 9 parts water); this may help prevent infection.
- Avoid direct contact with lesions when handling infected sheep.
If you or a member of your family contracts Club Lamb Fungus Disease, be sure to tell your physician that the fungus is different from other ringworm and may not respond well to traditional treatment.
There is no FDA-approved treatment for fungal infections of sheep. Therefore, any treatment must be under the supervision of a veterinarian who has examined the sheep, made a diagnosis, and prescribed the treatment. Overtreating with irritant preparations can result in crusty, weeping skin lesions that are not unlike Club Lamb Fungus Disease.
Research suggests that most treatments have little effect on individual lesions. Most reported cures are probably due to treatment administered just prior to spontaneous recovery. However, an advantage of treatment is that it greatly reduces contamination of the environment by infected animals.
For surface applied treatment, the crusts should be removed by scraping or brushing with a soft wire brush. The medicament should be brushed or rubbed in vigorously. Take care to remove and burn the scrapings.
Prevention and Control
- Immediately isolate animals with active lesions.
- Provide separate grooming equipment and feeding utensils.
- Clean and disinfect all items before using with other animals.
- Clean and disinfect contaminated pens and stables.
Use a commercial detergent and a 2.5-5% solution of a phenolic disinfectant, 2% cresol, 5% formaldehyde or a 2-5% solution of sodium hypochlorite (equal parts of bleach and water or full strength bleach). Bleach should not be used on clippers and other metal objects since it will cause them to rust. Nolvasan® solutions can be used to sanitize clippers and other equipment without rusting the metal.
Recommendations and Rules for Fairs & Shows
- Do not bring infected sheep to fairs or shows. Active fungal lesions will render health papers null and void. Also, do not bring recently treated sheep to fairs or shows. They are a serious source of infection to other animals.
- Do not loan or borrow grooming equipment or feeding utensils.
- If you think your sheep may have been exposed to the club lamb fungus, a mild solution of chlorine bleach (1 part bleach to 9 parts water) may be used as a body rinse when you return home (if bleach contacts metal equipment it will cause rust).
- Sheep for exhibit must be penned and equipment moved in only during specified hours. This allows show officials to maintain surveillance for infected sheep. All sheep will be processed through designated doors at specified times.
- At the Kentucky State Fair and other major shows each sheep will be individually inspected by a representative of the State Veterinarian. Animals suspected of having ringworm will have skin scrapings and wool collected for microscopic examination to determine if fungus is present. Suspect animals must be isolated by the exhibitor until test results are available.
- Animals testing positive for ringworm must be removed from the fairgrounds or placed in a common quarantine area until the show is completed. Positive animals cannot be penned individually during the show. Surveillance at county and district shows will be as strict as available resources will allow.
Club Lamb Fungus Disease can be controlled and its spread prevented, if all concerned work together. Here’s what you can do:
- Make your lambs less susceptible by washing them less frequently, using mild soap in order not to remove the lanolin, and clipping less closely and more carefully.
- Don’t show infected sheep.
- Don’t loan or borrow equipment.
- To protect your flock, keep newly purchased sheep, and sheep you have shown, in quarantine at home for up to 6 weeks.