What's new in dermatology (Proceedings)

Multiple new flea control products have been released in the past few years. Comfortis® (Lily) is a spinosad insecticide that is administered orally. It provides very rapid flea kill that lasts a month. It should be given with a full meal to ensure complete absorption. The flea must bite the host to ingest the insecticide and die; however, this is not a barrier to effectiveness in flea allergic animals due to the rapid speed of kill. Comfortis® is approved for use in dogs only. The most common side effect seen is vomiting. It should not be used together with daily high dose ivermectin (for treatment of demodicosis) as ivermectin toxicity results. The label recommends owners seek veterinary advice before administering this drug to epileptics.

Vectra 3D® (Summit) is a new spot on flea control product for dogs only. It contains dinotefuran (a neonicotinoid insecticide), pyriproxifen (juvenile growth hormone analog), and permethrin. The concentration of permethrin in this product is toxic to cats. Vectra® has good efficacy against fleas (rapid flea kill), ticks, and mosquitoes. Frequent bathing may necessitate more frequent application than once monthly as recommended on the label, especially when dealing with insect bite allergic patients.

Vectra® (Summit) is also available for cats as a once a month spot on. It contains dinotefuran and pyriproxifen. It provides rapid adult flea kill as well as larvicidal activity of the pyriproxifen.

Promeris® (Fort Dodge) is a once a month spot on for dogs containing metaflumizone and amitraz. Metaflumizone is a novel insecticide that provides rapid adult flea kill. Promeris® is labeled for flea and tick control. There is increased potential for drug interactions due to the amitraz (e.g. monoamine oxidase inhibitor use in patient and client). Promeris® has also been recommended as a treatment for generalized demodicosis. The "success" rate at day 84 of treatment was 42.9% with monthly application of the product and 62.5% with biweekly application of the product. Success was defined as a decrease in mite numbers. Longer term follow up was not reported in the study.

Promeris® (Fort Dodge) is also available as a monthly spot on for cats. The feline product contains metaflumizone only.

Older "new generation" flea control products we should not forget include Program® (lufenuron), Advantage® (imidacloprid), Frontline® (fipronil), Revolution® (selamectin), and Capstar® (nitenpyram).

True resistance of fleas to any of the above mentioned adulticides is extremely rare according to current monitoring efforts. What is seen as product failure is more likely to be inappropriate expectation of product performance on the part of the client or lack of a complete flea control program.

Simplicef ® (cefpodoxime proxetil) is a second generation cephalosporin for use in dogs. The dose is 5-10 mg/kg once daily. It is available in 100mg and 200mg coated tablets. It seems to cause less gastrointestinal upset than cephalexin so can be a good alternative for staphylococcal pyodermas. Cefpodoxime discs are available for sensitivity testing and should be used as sensitivity results for cephalothin do not equate to those for cefpodoxime.

Convenia® (cefovecin) is a third generation cephalosporin with good activity against staphylococcal organisms, but not Pseudomonas. It is approved for use in dogs and cats. The dose is 8 mg/kg given by subcutaneous injection every 14 days. Once reconstituted, the vial is good for 28 days if refrigerated (some discoloration is normal). Since superficial pyodermas should be treated for a minimum of 3 weeks, two injections of cefovecin are recommended. The drug is highly protein bound so some caution when using together with other highly protein bound drugs may be indicated.

Gastricalm® is a chelated zinc carnosine compound that protects the stomach lining and speeds repair of damaged gastric epithelium. It was designed for use with non-steroidal anti-inflammatories; however, it has demonstrated usefulness also in avoiding gastrointestinal upset caused by antibiotics (e.g. cephalexin) and cyclosporine.

3Vcaps HP: Eicosapentaienoic/docosahexanoic acid fatty acid supplement with free fatty acids. In humans these have been shown to have increased bioavailability.

There are several new avermectins being used off label for treatment of demodicosis in dogs. Doramectin is labeled for use in large animals in the US. It has been used at a dose of 600 mcg/kg SQ weekly with good effectiveness. It should not be used in ivermectin sensitive dogs. Moxidectin is available in the US as an oral once a month heartworm preventative and in combination with imidacloprid as a once a month spot on for control of fleas, heartworms, and several other parasites. The large animal injectable formulation has been used successfully at a dose of 200-400 mcg/kg orally daily. Moxidectin should not be used in ivermectin sensitive dogs.

Trilostane (Vetoryl®) was recently approved for the treatment of hyperadrenocorticism. It comes as a 30 and 60 mg capsule.

Genetic testing for the MDR1 mutation is now as simple as submitting a buccal mucosal swab to the Washington State University clinical pathology lab. This testing determines if an individual has the mutation in p glycoprotein, the protein that pumps various drugs out of the central nervous system, thereby preventing toxicity. Dogs can be normal/normal, mutant/normal, or mutant/mutant. This test is best known as a screening tool for susceptibility to ivermectin toxicity. Other drugs known to be a problem for dogs with this mutation include: loperamide, doxorubicin, vincristine, and vinblastine. Drugs that may cause a problem include cyclosporine, palitaxel (anticancer drug), mitoxantrone (anticancer drug), quinidine, digoxin, ondansetron (antiemetic), domperidone (antiemetic), acepromazine, and butorphanol. For more information about this testing, go to www.vetmed.wsu.edu/VCPL/

Two new species of demodex mite have been shown to cause skin disease in dogs. The short demodex mite, tentatively named Demodex cornei, lives in the superficial layers of the stratum corneum. This mite usually causes moderate to severe pruritus. Clinical signs may mimic classic demdodex infestations or may mimic allergic dermatitis as Demodex gatoi does in cats. This short demodex mite can be contagious so all dogs in the household should be checked and treated. Diagnosis is made by finding mites on superficial and deep skin scrapes or tape impressions. Finding one mite is probably diagnostic. Mixed infections with different species of demodex mite may be seen. Weekly dipping with lime sulfur for 4-6 weeks seems to be the most effective therapy. Daily ivermectin at 300-600 mcg/kg has also been effective in some cases. I have not seen any report on the effectiveness of amitraz. The longer mite, Demodex injai, lives primarily in the sebaceous glands. This mite usually causes a pruritic, greasy seborrhea primarily on the dorsum. It can be found on deep skin scrapes and on hair plucks. Mites are usually found in small numbers and the disease has been seen in multiple West Highland White terriers as well as several other breeds. This mite may be seen secondary to chronic steroid use. Treatment is the same as for Demodex canis.

Methicillin resistant staphylococcal infections are being seen with increasing frequency in veterinary patients. Methicillin resistant Staphylococcus aureus (MRSA), S. intermedius (MRSI), and S. schleiferi (MRSS) have all been reported. Initially hospital acquired infection with MRSA was the prevalent problem. Now, MRSA are widespread in the community. Transmission of MRSA from humans to animals seems to be more common than transfer of MRSI from animals to humans. Proper disinfection protocols are critical for preventing transmission of methicilllin resistant staphylococci in the hospital setting. A recent article in JAVMA (Jan 15, 2009, vol 234 No.2 p 187) had good recommendations for preventing transmission. Thorough hand washing before and after contact with each patient is critical. Disinfection of floors, counters, etc., as well as instruments that contact patients is also important. Patients infected with methicillin resistant staphylococci should be isolated. Information on educating pet owners on MRSA (screening, treatment, and prevention) is available at http://osufacts/okstate.edu and search for MRSA. If an animal in the household is diagnosed with MRSA, humans should be screened as possible source of the infection. Likewise if humans in the household have MRSA infections, animals in the house should be screened to ensure they are not also colonized/infected. Any skin infection that is not responding to appropriate antibiotic therapy should be cultured. Some antibiotics that may work for methicillin resistant staphylococci include chloramphenicol, clindamycin (resistance may develop rapidly), doxycycline, potentiated sulfonamides, and amikacin. Methicillin resistant staphylococci are often fluoroquinolone resistant. Ethical concerns may prohibit use of linezolid or vancomycin in animals as these drugs are used for serious MRSA infections in people.