12 - Focal-Multifocal Alopecia Part 2

Dermatophytosis

What major infection is one of the main causes of alopecia, and is also called ringworm? It is a superficial fungal infection of keratinized structures, using proteolytic and keratolytic enzymes to break down keratin. It is an important pathogen and is contagious, infectious, and zoonotic. Common species include M. canis (dogs/cats), N. gypsea (soil), and T. mentagrophytes (rodents/rabbits/hedgehogs). Any species can be involved in dog infections, while cats will most likely be infected with M. canis. Direct contact, fomites, and microtrauma can all be involved in infection spread, and clinical presentation usually occurs 1-3 weeks after exposure.

M. canis

Which species is the most common cause of dermatophytosis in cats? It is never part of the normal flora. If other dermatophytes are seen in cats, the animal is immunocompromised.

Yorkshire

Dermatophytosis is more common in dogs under 1 year old, in hunting/working dogs, and especially in which breed of terrier?

Yes

Can long-haired and Persian cats be asymptomatic carriers for dermatophytosis?

Adherence

Which stage of dermatophytosis occurs in the first 2-6 hours and is when the arthroconidia adhere to the corneocytes?

Germination

Which stage of dermatophytosis occurs in the first 4-6 hours, occurs second, and is when the germ tubes emerge from the arthroconidia to penetrate the stratum corneum?

Invasion

Which stage of dermatophytosis will occur within 7 days and is when the hyphae invade the keratinized structures?

Arthroconidia

Formation of what structures is the fourth stage of dermatophytosis and is when the hyphae segment to form these? This completes the cycle.

Alopecia

What sign is the number one clinical sign of dermatophytosis, specifically the circular-coalescing type, along with erythema, scales, and crusts? Dogs can also have kerions, but this is uncommon. Cats may have a pustular form of this, pseudomycetomas, and/or onychomycosis (nail changes). The face, ears, and muzzle will be the most common initial sites of this, and it is often asymmetrical.

Kerion

What is the term for a deep form of alopecia, sometimes seen in dogs with dermatophytosis?

M. canis

The Wood’s lamp test allows diagnosis for only which species of dermatophyte? Only 72% of cases of this species will show a positive result. Trichogram evaluation, fungal PCR, fungal culture (toothbrush), and biopsy should be done following this test. The positive result (green fluorescence) is produced by a metabolite, not by the fungus itself.

Miconazole

What antifungal, added with chlorhexidine, is the recommended treatment for all cases of dermatophytosis? It can be the sole treatment for focal lesions and is given twice weekly. These two agents produce a synergistic effect, and are good for decontaminating housemates and contacted animals.

Lime Sulfur

A dip in what chemical (Ca polysulfide) is one treatment option for dermatophytosis, and is given twice weekly? It has 100% sporicidal efficacy at recommended dilutions, is malodorous and staining, and often takes 18-30 days to cure even in combination with systemic therapy.

Itraconazole

What antifungal is a first-line option against dermatophytosis, is highly effective, has a good safety profile, is given in a non-compounded form, and takes 36-112 days to cure?

Terbinafine

Which antifungal is a first-line treatment option for dermatophytosis, has the lowest MIC against these fungi, has a good safety profile, and takes 21-158 days to cure?

Second

Are griseofulvine, fluconazole, and ketoconazole first or second line treatment options for dermatophytosis? Griseofulvine cannot be given to pregnant animals or to FIV + cats.

Yes

Has dermatophytosis been cured if there are two consecutive fungal cultures (2-4 weeks apart) and a negative PCR, OR a negative fungal culture, negative Wood’s lamp, and resolution of lesions?

Demodicosis

What infection is a major cause of alopecia, and is caused by Demodex mites acquired in the first 2-3 days of life through direct contact? These are controlled by the immune system but may proliferate in hair follicles to become an opportunistic parasitic disease. Dogs will often have D. canis or D. injai, while cats will often have D. cati or D. gatoi.

Juvenile

What type of onset of demodicosis in dogs is due to temporary immune aberrations (T-cell related), with a strong genetic component or immature immune system likely involved? Onset will be at 3-6 months old but up to 12-18 months. Breeds such as American Staffordshires, pitbulls, Shar-peis, french and english bulldogs, boxers, boston terriers, and others are predisposed.

Adult

What type of onset of demodicosis in dogs is associated with immunosuppressive conditions such as hyperadrenocorticism, hypothyroidism, diabetes, neoplasia, infections, immunomodulatory drugs, or underlying diseases? Onset is usually over 4 years old unless it is related to drug therapy.

Localized

What type of demodicosis infection is more commonly in juvenile-onset and is caused by transient and focal overpopulation of mites? There will be multiple small lesions with variable erythema and no pruritus, and lesions are usually located on the face, head, or front limbs. Most cases will resolve spontaneously.

Generalized

What type of demodicosis infection is associated with both juvenile and adult-onset, and will produce multifocal, patchy, or total alopecia, with erythema, pruritus (due to secondary infections), and systemic illness in some cases? Treatment is with miticidal drugs and antimicrobials if necessary.

D. canis

What species of demodex is the most common one affecting dogs, and will present with hypotrichosis, alopecia, mild erythema, comedones, and scaling? Advanced conditions will progress to papules, pustules, furunculosis, erythema, crusting, and ulceration, as well as lymphadenopathy, lethargy, and possibly septicemia. Pruritus will only occur if secondary bacterial infection occurs. The face, periocular areas, and feet are most commonly affected.

D. injai

Which demodex species is less common than D. canis in dogs, is a commensal species, and is primarily seen in terrier breeds? They occupy the follicles from orifice to sebaceous gland, cause greasy hair coat on the dorsal trunk, and have higher instances of secondary bacterial and malassezia infections with pruritus.

Deep

What type of skin scrapes, plus trichoscopy, can be used for diagnosis of demodicosis? The presence of high numbers of mites and eggs should be observed.

Isoxazolines

Which group of drugs is the treatment of choice for demodicosis? These include Fluorolaner and Sotilaner, as well as others. These are used off-label for this purpose.

Amitraz

Which drug is the only FDA approved treatment for demodicosis for dogs, although it is not the treatment of choice and is used as a dip? Macrocylic lactones can also be used.

1

Treatment for demodicosis should be continued for how many months beyond two consecutive negative monthly skin scrapings? Dead mites do not produce a negative scraping. A follow up should be done a year later.

D. cati

Which demodex species is found in cats as a commensal species, can cause localized or generalized forms, and produces erythema, alopecia, scale, crusting, and variable pruritus? It is often associated with underlying diseases or immunosuppressive drugs. Deep skin scraping, trichoscopy, and fecal flotation can all be used for diagnosis. It can resolve spontaneously if the underlying treatment is addressed.

D. gatoi

Which demodex species is found in cats and is a non-commensal species? It is contagious and inhabits the stratum corneum, presenting mainly with pruritus and secondary lesions due to self-induced trauma. The ventral abdomen and trunk are more likely to be involved. Superficial skin scraping and tape cytology can be used for diagnosis but false negatives are common.

Yes

Do cats receive the same treatments for demodicosis as dogs?