Page 1046 - Problem-Based Feline Medicine

1038 PART 13 CAT WITH SKIN PROBLEMS

Clinical signs not licensed for this purpose. The systemic medication
is essential in cases (or suspected cases) of ectopic
Many cases present with a waxy otitis externa and
infestation, and because of the highly contagious nature
head-shaking due to irritation generated by the mites
of mites, all in-contact animals should also be treated.
feeding. Classically the debris has a brown “coffee
ground” appearance. However, the amount of debris Antibacterial treatment, with or without corticos-
can range from minimal to near complete obstruction of teroids, may be indicated to alliviate severe self-trauma.
the canal.
The ectopic infestations can cause pruritus, alopecia, Prognosis
miliary dermatitis and secondary infection which
Prognosis is excellent with appropriate treatment.
resembles other allergic disease, but is less common
than otic signs.
Prevention
Diagnosis Repeat treatment of the affected cat and all in-contact
animals is required to prevent reinfection.
Diagnosis is based on clinical signs and finding
the mites. Mites are often visible on otoscopic exami-
nation. Transmission
● Samples of exudate can be examined using magni-
Transmission occurs via direct spread from one cat to
fying glasses, or microscopically on slides to iden-
another in most cases, but mites may survive off host
tify mites.
for a short period.
Ectopic infestations may not be identified on cytology,
rather a presumptive diagnosis is made on response to NEOTROMBICULA AUTUMNALIS
systemic miticide therapy. (NEOTROMBICULOSIS)

Classical signs
Differential diagnosis
● Pruritus.
The aural manifestation of mites is quite distinct, but
● Erythema, papules and alopecia.
other infectious causes of otitis (including bacteria
● Feet, head and limbs commonly involved.
and malassezia) need to be ruled out.
● Larval stages appear as orange-red dots
The ectopic infestation may cause a pruritic dermatitis with the naked eye.
that can resemble flea allergic dermatitis, food hyper-
sensitivity, atopic dermatitis and various ectopara- Pathogenesis
sitic and microbial skin infections.
There are over 700 species of harvest mites, although
only approximately 20 have been identified as causing
Treatment
animal disease.
Otitis externa may be treated with drops containing
The adult stages are not parasitic and are free living,
agents such as milbemycin, pyrethrins/piperonyl
feeding on decaying vegetable matter. The six-legged
butoxide, thiabendazole or lindane. Fipronil and imi-
larval stages of the mites are parasitic of animals and
dacloprid have also been reported as effective topical
feed on surface debris.
therapies. If the discharge is marked, the ears may need
to be cleaned with a ceruminolytic first to allow ade- The resultant reaction may give rise to significant self-
quate penetration and dispersion of the miticide. trauma and in some cases a hypersensitivity response
may develop.
Systemic medications that are effective include sele-
mectin and ivermectin (200 μg/kg subcutaneously or More common in summer and autumn, particularly in
orally, repeated 2 weeks later). However, ivermectin is grassy areas or hedgerows.