Systemic Ringworm in Felines

The term "ringworm" confuses many cat owners because the disease is caused by several species of fungi, not worms. Clinically called "dermatophytosis," ringworm "is the most common infectious skin disease of cats," says Dr. Chick Newman of Newman Veterinary Medical Services in Seattle. Because ringworm is often difficult to cure on the cat and can be transferred to humans, Dr. Newman recommends extensive treatment with systemic and topical anti-fungal agents for infected cats and "painstaking hygiene and decontamination of the environment."

  1. Causes

    • Several fungi cause ringworm, including Microsporum canis (the most common type found in cats), Microsporum gypseum and Trichophyton mentagrophytes. Veterinarians diagnose ringworm primarily in young, long-haired breeds, with Himalayans and Persians being predisposed to the condition, says Dr. Mandy Burrows in "Treating Ringworm in the Cat" for The Veterinarian website. High-stress factors (shelters and catteries), immunodeficiency diseases (feline leukemia or FIV), and poor nutrition can suppress your cat's immune system enough to contract ringworm. Transmission of the disease occurs either by direct contact with hair or skin cells of an infected animal or by the spread of fungal spores in the environment, usually on brushes, clippers and pet cages.

    Symptoms

    • According to Dr. Arnold Plotnick of Manhattan Cat Specialists, cats with systemic and topical ringworms can present with a variety of symptoms, beginning with the typical round, crusty, scaly lesions and surrounding hair loss. Your cat may be intensely pruritic (itchy) to the point of forming sores from scratching, or not itch at all. Ringworm causes alopecia (hair loss) and may show as either round or oval hairless sections around the ringworm lesions. Some cats demonstrate skin darkening or redness around the sores, and young cats can develop itchy blackheads on the chin that become infected from scratching.

    Diagnosis

    • Veterinarians diagnose systemic ringworm using several methods, beginning with a Wood's lamp examination. The Wood's lamp causes the fungus to fluoresce in the dark, turning bright green wherever the spores are found on the skin and hair. Because not all species fluoresce, your vet may recommend a fungal culture. This involves pulling hairs from several parts of your cat's body out by the roots and placing them in a fungi-sensitive culture, where they are monitored for 14 days to check for fungal growth.

    Treatment

    • Many cats resolve ringworm disease without treatment, but administering systemic and topical medications to your infected pet hastens a cure, says Dr. Bari Spielman of Pet Place. Systemic oral medications include ketoconazole, itraconazole and, most commonly, griseofulvin. Your cat will need to have occasional blood tests during treatment with griseofulvin due to its tendency to suppress bone marrow function, and you should give the medication with food to avoid gastrointestinal upsets. Veterinarians typically recommend that topical treatments begin with weekly antiseptic or lime sulfur dips followed by a 2 percent chlorhexidine shampoo and application of anti-fungal cream to the lesions.

    Considerations

    • Veterinarians consider systemic ringworm a zoonotic disease, meaning it can be passed from an infected animal to humans. The vets at Medi-Vet Animal Health LLC say that, "People with the highest risk of catching ringworm from their pet are young children who have never been exposed, the elderly or people with a depressed immune system." The pruritic ringworm lesions on humans appear similar to those on animals, with a circular, raised, crusty edge and possible hair loss, and need to be treated both topically and systemically. Most humans develop immunity to a particular strain of ringworm once they have been exposed.