Vets South 2015

Canine Demodicosis – some new ideasAnthony Chadwick BVSc CertVD MRCVSThe Webinar Vet

Diocletian’s Palace- Split

Old City- Dubrovnik

My Objectives

• Some understanding of aetiopathogenesis• Juvenile onset demodicosis• Adult onset demodicosis• MDR1 mutation gene• Treatments old and new - with my bias• Prognosis

The Enemy

• Demodex canis• Demodex injai• Demodex cornei

Demodex Life Cycle

• Lasts about 10-12 days• Obligate parasites• Feed mainly on scale and sebum not blood• Live in the hair follicles and sebaceous glands• Occasionally contagious (in the textbooks)• Transmitted from dam to pups during lactation• Eggs-larvae-protonymphs-deutonymphs-adults

Demodex Mites

Aetiopathogenesis

• Owen reported generalised demodicosis in pups receiving anti-lymphocyte serum

• Scott suggested a specific T cell functional defect• Affected dogs have decreased Th1 and increased Th2• Seems to be a defect in IL-2• An inherited autosomal recessive gene may be involved• In older dogs it is associated with generalised immunosuppression

caused by an underlying disease

Breeds

• Shar Peis• SBT• Boxer• English Bulldog• Dobermann• Newfoundland• WHWT• Pug

Clinical Signs

Localised demodicosis:• Alopecic, often circular areas up to 5 areas• Often will resolve without treatment• Usually not pruritic

Clinical Signs

Generalised demodicosis:• Pododemodicosis• Alopecia• Scaling, crusting and ulceration• Hyperpigmentation • Comedones and follicular casts• Pyoderma• Can be unwell

Clinical Pathology

Generalised demodicosis:• Anaemia• Increased wbc• Hyperglobulinaemia• Decreased thyroxine level

More significant in older dogs

Juvenile-onset Demodicosis

• Generally dogs under 2 years of age( maybe seen in older but missed earlier on)

• More likely to cure• May need treatment for 2-3 months minimum• Watch carefully for next year• Spay or castrate• Must not use to breed• Improve level of nutrition • Improve endo and ecto parasite treatment

Adult-onset Demodicosis

• Older dogs• Harder to treat• Look for underlying causes such as allergy, endocrine or neoplastic• Poorer prognosis• Often control rather than cure unless find underlying cause

Diagnosis

• Deep skin scrapings• Hair plucks• Biopsies

Clinical Presentation in Dogs

Clinical Presentation in Dogs

Clinical Presentation in Dogs

Clinical Presentation in Dogs

Clinical Presentation in Dogs

Treatments

• Amitraz• Ivermectin• Moxidectin• Doramectin• Milbemycin• Antibiotics• Shampoos• Supplements

Amitraz

• Formamidine - a monoamine oxidase inhibitor• Probably need at least 8-12 washes weekly at 250-500ppm• Quite toxic treat with antibiotics first• Health and safety and environmental concerns• Quite arduous to perform• ProMeris spot-on

Ivermectin

• Macrocyclic lactones• Potentiate the release and effects of GABA• May cross the blood brain barrier in certain breeds causing

neurological problems• Very effective in my hands potent adult and ovicidal effect• MDR1 defect test• Slowly increase dose upto 600mcg/kg/d orally• Informed consent

Moxidectin

• Bayer (Advocate)• Work done by Ralph Mueller in Germany• Dogs often look better but are not microscopically cured • 72 dogs in study 52 juvenile 20 adults• 23 juvenile into remission 3 adults• Meantime to remission 12.5 weeks• Can be used weekly to better effect• Some studies show better results

Doramectin

• Dectomax (Zoetis)• Used as a subcut injection weekly gave 100% success• 0.6mg/kg given weekly• When given orally success rate dropped to 72%• Relapses seen in both studies depends on previous tx• Treat beyond negative skin scrape at least 30-60 days• US product says not to be used on dogs

Milbemycin

• Interceptor Novartis or Milbemax• Cat tablets can be used because of large amount of milbemycin

and relatively small amount of praziquantal • 1-2mg/kg daily until remission and then 4-8 weeks• herding dogs homozygous for MDR1 gene can develop ataxia• Generally safer than ivermectin

Antibiotics

• Staphylococcus pseudintermedius has a symbiotic relationship with the demodex mite

• Can see Pseudomonas on occasions• I tend to treat most cases with antibiotics for at least 1 month

because of symbiotic relationship• Consider C&S for all cases of deep pyoderma

Shampoo

• Benzoyl peroxide shampoos recommended due to their follicular flushing activity

• Mites are easily desiccated when on surface of skin• Should use before amitraz

Supplements

• Vitamin E• Good nutrition• Flea• Worming treatment

How to Measure Success?

• Monthly skin scrapes• Several areas• Use pluckings, scrapings and biopsies as necessary• Count mites and different stages in cycle

Histopathology

Histopathology

Histopathology with Lucy

Histopathology

Histopathology

Histopathology

Histopathology

Chief Histopath findings

• Mites often seen in follicles or on S corneum• Interface mural folliculitis• Nodular dermatitis• Folliculitis/furunculosis

Some Clinical Cases

Arnie 7yo MN Dobermann• Presented with recurrent demodicosis and pyoderma 18m hx• On low dose ivermectin 300mcg/kg/day• Swollen feet and pruritic• Mild neurological signs?

Some Clinical Cases (cont.)

• Thyroid low and TSH high but normal borderline free T4• Treatment started and antibiotics given• Treated with promeris and MDR1 blood test taken• Mites seen on scraping• Pruritic so hypoallergenic diet instituted

1 Month Later

• Demodex positive with eggs• Ivomec 2.2mls per day• Post pill T4 still low increase soloxine dose• Continue cephalosporins• Only occasional mites• Losing weight but feet look better• T4 still low

A Further Month

• No mites• On soloxine 0.8mg bid but still low T4• Still slightly pruritic

1 Month Later

• Biopsies taken revealed no mites• Allergy testing positive for dust mites• Still some trauma of feet

• 1 month later presented with anaemia and possible splenic mass • PTS

Some Clinical Cases

Oscar, a 2.5 yo MN Bulldog• Oscar presented with swollen feet• On thyroxine and preds and epiphen• Epileptic• On advocate for flea control

• Advise stop thyroid and preds onto antibiotics and food trial• Skin scrape negative

• Very itchy off steroids and I was away• Dog put on cortavance and then preds• Re-seen and biopsied• Pododemodicosis and in chin and flank• Started aludex washes weekly for 8 weeks• Stopped steroids• MDR1 blood test performed• Re biopsied feet - mites still present

• Started ivomec after negative MDR1 test• 1 month later feet look good but dog had more fits and more excitable• Changed to milbemax cat• Stopped after 3 months• 3 months later it has returned• The treatment was re-started and no further recurrences• Died 2 years later because of brachycephalic syndrome

Any Questions?