Page 1514 - Clinical Small Animal Internal Medicine

1452 Section 12 Skin and Ear Diseases

not directly contact the solution or inhale it. Application PO, and sarolaner (Simparica® for dogs; Zoetis) given at
VetBooks.ir in a well‐ventilated area is important. 2 mg/kg PO. These products are labeled for monthly usage
Ivermectin is a therapy that is often very efficacious in
for flea and tick prevention and treatment. Fluralaner
treating demodicosis. Herding breeds should be assessed
age of 25 mg/kg PO has also been found to be very effica-
for a mutation of the ABCB1 (formerly MDR1) gene (Bravecto® for dogs; Merck) given once at a minimum dos-
which encodes for the cell membrane transporter cious at treating demodicosis. This product is labeled for
P‐ glycoprotein. This mutation can lead to severe toxicosis administration every 12 weeks for the prevention and
with avermectins. Some of the breeds reported to be pre- treatment of flea and tick infestations in dogs. Afoxolaner
disposed to this mutation include collies, border collies, (Nexgard®; Merial) given at the minimum dosage of 2.5 mg/
Shetland sheepdogs, Australian shepherds, Old English kg PO every 14 days for two months has been found to be
sheepdogs, white Swiss shepherds, long‐haired whippets, very effective. However, only one dose may result in deep
McNab, and silken windhound. This mutation is still negative skin scrapings. It is labeled for monthly usage for
possible in any dog breed, but less likely. The genetic test flea and tick control and can be used in dogs 8 weeks of age
for the mutated gene can be done through Washington and older, whereas fluralaner and sarolaner can only be
State University College of Veterinary Medicine. used in dogs at least 6 months of age. Lotilaner, like afox-
Possible side‐effects associated with ivermectin toxico- olaner, may be used in dogs as young as 8 weeks of age.
sis include lethargy, vomiting, diarrhea, anorexia, mydria- These parasiticides act by blocking insect GABA‐ and glu-
sis, and ataxia. In severe cases, seizures, coma, and death tamate‐gated chloride channels and are generally very safe
can result. Side‐effects can also occur in dogs that carry a but should be used with caution in dogs with a history of
normal ABCB1 gene and are often less severe and may seizures. Possible side‐effects include vomiting and diar-
resolve by lowering the dosage. Due to possible side‐ rhea. Sarolaner may cause tremors, unsteadiness, or sei-
effects, an incremental dose increase is strongly suggested. zures. Fluralaner may cause seizures in patients which do
The dosage range is 0.3–0.6 mg/kg once a day PO. The not have a history of seizures, but is labeled as safe for use
author determines dosing by calculating the dose desired in breeding, pregnant, and lactating dogs, and in those
in this range and starting at one‐third this dose. This is with the ABCB1 gene mutation. Lotilaner may also cause
given for one week, followed by two‐thirds the final dose an increase in blood urea nitrogen. Afoxolaner should be
for one week, then ending at the final dose desired. used with caution in dogs with a history of seizures.
Other macrocyclic lactones that can be used are Females or males that have been treated should be
moxidectin and doramectin. Moxidectin is dosed at 0.2– neutered due to the potential for passing the predisposi-
0.5 mg/kg/day PO. Again, gradual dosing is indicated. tion to develop demodicosis to offspring. In addition,
Possible side‐effects include those listed for ivermectin. females should be spayed because the stress of a heat
Moxidectin is also available as a topical product in combi- cycle or pregnancy could worsen the disease.
nation with imidacloprid (Advantage Multi® for dogs;
Bayer). This is an approved European treatment applied Prognosis
weekly for demodicosis. It is labeled for monthly usage in Overall, prognosis is good. Recurrence of disease can
the United States but has shown better results when occur, so following the treatment recommendation of
applied every 1–2 weeks, primarily for juvenile‐onset cases 30 days past two consecutive negative skin scrapings can
and mild forms of demodicosis. Doramectin can be given help prevent recurrences. Life‐long therapy may be
at 0.6 mg/kg subcutaneously (SC) or PO once a week. The needed in some cases. Long‐term glucocorticoids are
SC administration has resulted in better outcomes. not recommended in patients with demodicosis or that
Milbemycin oxime (Interceptor® for dogs; Elanco) is have had demodicosis. The author believes that any glu-
another efficacious product. This can be used at 0.5 mg/ cocorticoids or oclacitinib maleate (Apoquel; Zoetis)
kg PO once daily increasing by 0.5 mg/kg every seven should be used with great caution. A dog is not consid-
days to a final dosage of 2.0 mg/kg/day. This medication ered cured until one year after treatment is completed.
is generally well tolerated. Mild neurologic side‐effects With the advent of isoxazolines as maintenance flea and
have been noted. Breeds that do not tolerate ivermectin, tick preventtives, the likelihood of recurrence or even
including collies, may tolerate this medication but care is development of demodicosis will probably diminish.
recommended to ensure no adverse side‐effects ensue,
as neurologic effects are still possible. Ataxia has been Feline Demodicosis
noted in dogs homozygous for the ABCB1 gene muta-
tion at a dosage of 1.5 mg/kg/day PO. Etiology/Pathophysiology
The newest available therapies are in the isoxazoline Three species of demodectic mites have been implicated
class. These drugs are not labeled for treatment of Demodex in feline demodicosis. These include D. cati, D. gatoi, and
sp. but have been found to be very efficacious. These an uncommon, unnamed, morphologically distinct
include lotilaner (Credelio® for dogs; Elanco) at 20 mg/kg Demodex mite. Demodex cati spends its life cycle in the