Arthropods

VMP 930Veterinary Parasitology

Arthropods Largest, Most Diverse Animal Phylum Jointed appendages Chitinous Exoskeleton Important Parasitic Groups

Arachnids cephalothorax + abdomen + 8 legs Simple Metamorphosis (Hemimetabolous)

Egg, larvae, nymph, adult (all similar in appearance)

Insects Head, thorax, abdomen + 6 legs Simple Metamorphosis (Hemimetabolous) OR

Egg, nymph, adult (all similar in appearance)

Complex Metamorphosis (Holometabolous) Egg, larvae, pupae, adult (are not similar in appearance)

Arachnids: Mites

Arachnids: TickIxodes

scapularis

Rhipicephalussanguineus

Dermacentorvariabilis

Amblyommaamericanum

Insects: Lice

Mallophagan (chewing) Louse Anopluran (sucking) Louse

Insects: Fleas

Insects: True Bugs

Insects: Flies

Insects: Flies

Arachnids General Arthropod Characteristics Cephalothorax + abdomen + 8 legs Simple Metamorphosis (Hemimetabolous)

Egg, larvae, nymph, adult Groups of Parasitic Arachnids (Subclass Acari)

Mites Mesostigmatid mites -- Dermanyssus, Ornithonyssus Astigmatid mites -- Sarcoptes, Notoedres, Otodectes Prostigmatid mites -- Demodex

Ticks Metastigmatid

Argasid – Soft ticks Ixodid – Hard ticks

Mesostigmatid Mites Stigmata (respiratory pores) in the

middle of their bodies

Dermanyssus and Ornithonyssus bloodsucking mites

Mites hide in environment during daytime, feed on birds during night

Blood loss leads to decreased production Heavy infestations may cause death

Control with environmental acaricides, as well as treating birds

Dermanyssus gallinaeRoost mite or Red mite

Dermanyssus gallinaeRoost mite or Red mite

Spends most of time on birds Decreased production, feed conversion Matted feathers, esp. around vent Treat birds, environment Carried on fomites (egg crates, clothing, etc.) May feed on other hosts (horses, dogs,

man if birds unavailable)

Ornithonyssus sylviarumNorthern Fowl Mite

Ornithonyssus sylviarumNorthern Fowl Mite

Astigmatid mites

Lack stigmata - respiration is through integument

Includes the ‘Mange’ mites Family Sarcoptidae

Sarcoptes scabiei - scabies mite (dogs, pigs, man, sheep, goats, cattle, horses) –

different subspecies for various hosts Notoedries cati - cat mange

S. scabiei & N. cati Entire life cycle on host in burrows in skin -

transmission via direct contact Pathology includes skin lesions, secondary infection,

irritation

Mange mites

Sarcoptesscabiei

Sarcoptesscabiei

Canine Scabies

Sarcoptes scabiei

Scabies mite eggs from skin scraping

Cats harbor Notoedresrather than Sarcoptes

Feline scabies

Sarcoptes scabiei in humans

Treat with topicals: Selamectin (Revolution®)

Imidacloprid + Moxidectin (Advanatge multi®) is most often used

Bath topicals lime-sulfur, carbaryl, malathion, carbamates (not

kittens/puppies), organophosphates (caution with cats)

Systemics Ivermectin - subcutaneous injection In-feed ivermectin for confinement-reared pigs

Sarcoptes & Notoedres

Scaly leg mite of birds(not on exam)

Knemidokoptes mutans Production birds and pet birds Burrow into epidermis of legs causing

scales to lift up, legs become thickened and deformed

Treat with topical acaracides, also oral or IM ivermectin (0.2mg/kg) or 50% topical

Cover affected area with Petroleum Jelly

Scaly leg mites -Knemidokoptesmutans

Otodectes spp.Ear mites (cat, dog, rabbit)

Copious cerumen production mites observed on swabs of ear canal

swab ear with cotton swab and place under warm light

Also visualize with an otoscope

Head trauma in cat due toOtodectes cynotis

Otodectes

Prostigmatid mites

Stigmata (respiratory pores) in anterior of their bodies

Includes the Follicle mites Family Demodicidae

Demodicidae: Demodex spp.

Demodex canis -- red mange

Demodex cati

Demodex bovis - cattle follicular mite Normal fauna, but if disease

develops (nodules on neck and forequarters); then usually incurable

Demodex folliculorum , D. brevis -- humans

Demodex canis -- red mange

Mites live in hair follicles and sebaceous glands

Red mange --Inflammation and scab formation

Types of Demodectic mange

Localized demodicosis face, skull, ear canal, forelegs, trunk alopecia, scaling, hyperpigmentation,

erythema Dz of young dogs

most resolve spontaneously ~ 10% progress to generalized demodicosis

Generalized Demodicosis large areas of body involved erythema, crusting, rancid seborrhea,

lymphadenopathy inherited immune defect chronic DZ

Demodectic Pododermatitis digital and interdigital disease

Types of Demodectic mange

Generalized Demodicosis - lesions

Demodex canis: Diagnosis Diagnose and monitor using deep skin

scrapings, trichogram (plucked), biopsy

Photos - Mueller et al, 2012

Deep Skin Scrape

Demodex canis: risk factors

Immune suppression, malnutrition, neoplasia and chemotherapy, endocrine disease Especially with adult-onset demodicosis – cure

immunosuppressive issue and demodicosis should resolve.

Genetic connection to Generalized Demodicosis Part of normal flora but affected adult dogs should

not be bred

Topical moxidectin (weekly) Daily oral milbemycin, moxidectin or ivermectin Amitraz rinses (weekly or biweekly) Topical or oral antibiotics for pyoderma

Monitor treatment success with skin scraping Continue treatment 4-8 weeks post-remission

Clinical cure w/o Parasitic cure = recurrence Neuter dogs with Generalized Demodicosis

Demodex canis: Treatment