External Parasites in Dogs (NAVLE Notes)
External Parasites in Dogs (NAVLE Notes)
External parasites such as fleas, mites, and ticks pose various skin and systemic risks to dogs. Here is a NAVLE-focused breakdown of their signs, diagnosis, and treatment options.
Fleas
- Signs:
- Pruritus (itchiness)
- Crusts, scabbing, and hair loss around the hips and tail base
- +/- Anemia in severe cases
- Diagnosis:
- Visible fleas or flea feces (crumbly red-brown debris) on the coat
- Etiology: Ctenocephalides felis (most common), sometimes C. canis
- Treatment:
- Fipronil (Frontline® spray): Safe for puppies >8 weeks; kills adult fleas within 12 hours
- Selamectin (Revolution®): Safe for puppies >6 weeks; kills adult fleas within 12 hours (doses can be divided for smaller dogs by weight)
- Lufenuron (Program® flavor tabs): Safe for puppies >6 weeks; targets immature fleas
- Key Points:
- Dogs usually have cat fleas, not dog fleas.
- Fleas are intermediate hosts for tapeworms and can transmit rickettsial diseases.
- Fleas may be hard to find on dogs with flea allergy dermatitis due to self-grooming.
Mites
- Sarcoptic Mange (Scabies):
- Signs: Intense pruritus, bumps, crusts, and seborrhea on the abdomen, chest, ears, elbows, and legs
- Diagnosis: Skin scraping
- Etiology: Sarcoptes scabiei canis
- Treatment:
- Lime-sulfur dips
- Selamectin (Revolution®)
- Fluralaner (Bravecto®) – effective but not labeled for mange
- Ivermectin – effective but toxic for MDR1 mutation breeds (e.g., collies)
- Key Point:
- Sarcoptic mange can affect humans but is self-limiting.
- Cheyletiellosis (Walking Dandruff):
- Signs: Intense pruritus (sometimes absent), scaling on the back, “moving dandruff”
- Diagnosis: Observation and microscopy
- Etiology: Cheyletiella yasguri
- Treatment: Similar to sarcoptic mange (Lime-sulfur dips, Selamectin)
- Key Point:
- Cheyletiellosis is contagious to humans.
Ticks
- Signs:
- Attached tick on the skin
- +/- Redness around the bite
- +/- Tick-borne diseases (e.g., Rocky Mountain spotted fever, ehrlichiosis, Lyme disease) with symptoms such as:
- Fever, anorexia
- Lymphadenopathy, splenomegaly
- Polyarthritis, petechiae
- Coughing, vomiting, diarrhea
- +/- Lower motor neuron paralysis
- Diagnosis:
- Inspect areas such as ears, head, neck, perineal region, between toes, and under the tail
- Etiology:
- Ixodidae family (hard ticks): Commonly Amblyomma spp., Dermacentor spp., Ixodes spp.
- Argasidae family (soft ticks): Otobius spp.
- Treatment:
- Removal with forceps or hemostats close to the skin
- Fipronil and Fluralaner for prevention
- Key Points:
- Tick paralysis is often caused by Dermacentor andersoni (Rocky Mountain wood tick) and D. variabilis (American dog tick).
- Lyme disease is transmitted by Ixodes spp. (e.g., I. scapularis, I. pacificus).
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