SUMMER MANAGEMENT OF BOVINE DERMATOPHYTOSIS

Pashu Sandesh, 04 April 2023

Poonam Shakya, Anju Nayak and Ajay Rai

NDVSU, Jabalpur (M.P.)

Dermatophytosis or ringworm is an infection of the superficial, keratinized structures of the skin and hair of animals and humans caused by the colonization of dermatophytes on keratinized tissue. It is mainly caused by the colonizing dermatophytes, i.e., Trichophyton, Microsporum and Epidermophyton. It primarily affects working bullocks. A higher incidence of dermatophytosis can also be seen in younger and immuno-suppressed animals. It is mainly transmitted by direct contact with infected animals or indirectly by contaminated fomites. High temperatures with humidity, overcrowding and close confinement during summer are predisposing causes to dermatophytosis.

Although it is a superficial skin infection, ringworm in cattle may significantly impact management and economics in affected herds. Once the disease is introduced into a herd, it spreads easily from one animal to another. Overcrowding may predispose the animals to come in close contact. The infection may also spread through indirect contact with fomites such as harnesses, grooming utensils, beddings, coverings etc. Infection may spread through animal attendants by mechanical transmission of infective materials through their hands. Animals have been found to carry the dermatophytes on their healthy skin and thus remain as a transmitting agent to susceptible animals. Spores may survive in the environment for 2 to 3 years and calves or purchased animals introduced into the herd are likely to contract the infection. The inflammation of the skin is associated with unthriftiness and general discomfort in affected animals. In addition, secondary bacterial infections may occur.

Ringworm can be diagnosed based on clinical signs such as white circular asbestos-like lesions on the forehead, around the eyes, ear, neck and shoulder, mild or intense pruritus, multifocal alopecia, scaling, crusting, formation of follicular papules etc. The affected areas of the skin become erythematous and the hairs over the areas fall off thus giving a picture of alopecia. The lesions are discrete and almost circular. The borders are raised having thick greyish crusts. The lesions tend to extend peripherally with central healing.

Laboratory diagnosis includes direct microscopic examination of clinical materials like skin scrapings, hair, nails, etc. For this purpose, materials are soaked in a few drops of 10% KOH solution on a slide and examined under the microscope by putting cover slips over them. The fungal elements are observed as refractory hyphal fragments. Spores/arthroconidia may be noted. Arrangements of spores on the hair are suggestive of infection with keratinophilic fungus. A cultural examination of Sabourauds dextrose agar can be done. The addition of antibacterial agents to the media may be required to cut down the growth of other bacterial contaminants. Examination of culture is to be carried out from time to time as most of the fungi have got slow growth rate. For further diagnosis, the slide culture technique may be done. Different stains such as Lacto phenol cotton blue, Haematoxylin and Eosin, Gomori’s methenamine silver technique, Gridley’s fungus stain and PAS etc. are also used for staining and diagnosis.  When hairs infected with certain fungal spores are examined under an ultraviolet light (Wood's lamp) they often emit an apple-green fluorescence. This fluorescence is due to tryptophan metabolite produced by fungi that had actively growing hairs. 

Treatment of clinical ringworm in cattle is expensive and time-consuming. While the disease is often described as self-limiting, resolution may take four to nine months, during which other in-contact animals become infected because of the contamination of the animal's environment. There is a need for effective prevention against the disease as hygienic and other preventive measures often fail. Humans can contract ringworm by handling an animal with the condition or sharing a living area with them. Ringworm in animals can be prevented by proper management of animals, especially during summer. The following measures can be taken:

1. Clip the affected hair, clean the area and remove the crust.

2. Wash or spray- Povidone-iodine (1%) / lime sulfur (4%) / chlorhexidine (0.5%).

3. Local application of Tincture Iodine or Povidone iodine or white field lotion (Benzoic acid + salicylic acid) BID for 20 days.

4. Inpidual lesions can be treated with miconazole/clotrimazole lotion BID locally.

5. Application of Karanja oil and Neem seed oil locally BID for 20 days.

6. Chlorpheniramine maleate @ 0.5 mg/kg BW IM for 3-5 days.

7. Confinement in the shed and the area that can easily be cleaned.

8. Prevent the introduction of other/new animals.

9. Quarantine all bought-in animals for a minimum of two weeks.

10. Disinfection of shed and premises with household bleach diluted 1:10 in water.