1. Ectoparasites and Diagnosing and Collection
Parasitology
Ectoparasites and Diagnosing and Collection
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2. Order: Siphonaptera (Fleas)
Blood-sucking parasites
Vectors of several diseases
Bubonic plague and tularemia
Dogs and cats are host to only a few species of fleas
Ctenocephalides felis and Ctenocephalides canis
Intermediate host for Dipylidium caninum (tapeworm)
Heavy flea infestation – anemia
Saliva is antigenic and irritating
Causes pruritus and hypersensitivity
Flea bite dermatitis or miliary dermatitis
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3. Fleas
Fleas are laterally compressed, wingless insects with legs for jumping
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4. Flea Life Cycle
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5. Fleas (cont.) Larval and droppings
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6. Orders: Mallophaga and Anoplura (Lice)
Dorsoventrally flattened, wingless insects with clawed appendages for clasping the host’s hair
Three body parts
Head
Mouthparts and antennae
Thorax
Three pairs of legs – no wings
Abdomen
Bears reproductive organs
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7. Lice Two orders based on mouth parts Mallophaga – biting and chewing
Move rapidly over host
Broad, rounded head
Feed on epithelial debris
Smaller than sucking lice
Generally yellow in color
Anoplura – sucking
Larger
Long, narrow heads
Feed on blood and move slowly on the host
Red to gray in color
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8. Lice (cont.) Host specific
Lice glue their eggs or nits to the hair or feathers of the host
Nits hatch in approximately 5 to 14 days
Nymphal stage
Three stages
Last 2 to 3 weeks
Adult stage
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9. Lice (cont.) Life cycle takes 3 to 4 weeks to complete
Nymphs and adults only live 7 days or less if not on the host
Eggs hatch in 2 to 3 weeks during warm weather but rarely if off the host
Transmission – direct contact
Louse infestation – pediculosis
More severe in young, old, and poorly nourished animals
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10. Lice (cont.) Common biting lice of domestic animals
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11. Lice (cont.) Diagnosis Careful examination of hair coat or feathers
Magnifying lens
Grasp lice or nits with a forceps and place in a drop of mineral oil on a slide
Identification beyond order is difficult but not necessary
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12. Class: Acarina (Mites and Ticks)
Infestation of mites or ticks – acariasis
Blood-sucking arachnids
Dorsoventrally flattened
Head – capitulum; serves as an organ of cutting and attachment
Two types of ticks
Hard ticks (Ixodidae)
Soft ticks (Argasidae)
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13. Hard Ticks (Ixodidae)
Important vectors of protozoal, bacterial, viral, and rickettsial diseases
Saliva of female of some species is toxic
Ascending paralysis in animals and humans
Tick paralysis
Species associated with tick paralysis
Dermacentor andersoni (Rocky Mountain spotted fever tick)
Dermacentor occidentalis (Pacific Coast tick)
Ixodes holocyclus (Australian paralysis tick)
Dermacentor variabilis (wood tick)
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14. Hard Ticks (Ixodidae) (cont.)
Hard, chitinous covering (scutum)
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15. Hard Ticks (Ixodidae) (cont.)
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16. Soft Ticks (Argasidae)
Lack a scutum
Females feed often and lay eggs off host
More resistant to desiccation than hard ticks
Can live for several years in arid conditions
Three genera of veterinary importance
Argas sp., Otobius megnini, and Ornithodoros sp.
Argas sp. are ectoparasites of birds
Vector for bacterial and rickettsial diseases of birds
Ornithodoros sp. live in sandy soils and shady areas around trees
More important in people and rodents than domestic animals
Transmits the agents of foothill abortion in CA
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17. Soft Ticks (Argasidae) (cont.)
O. megnini – spinose ear tick
Housed stock, dogs, and people
Only larval and two of the nymphal stages are parasitic
External ear canal; produce waxy exudate
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18. Mites Arachnids that occur as parasitic and free-living forms
Some intermediate hosts for cestodes
Most parasitic mites are obligate parasites
Spend entire life cycle on the host and produce a dermatologic condition – mange
Sarcoptiform mites
Small – grain of salt
Bodies – round to oval
Tiny suckers are end of legs – pedicels
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19. Sarcoptiform Mites Two basic families
Sarcoptidae – burrow or tunnel in epidermis
Localized hair loss and inflammation
Spread rapidly
Sarcoptic mange – Sarcoptes scabiei
Zoonotic
Demodex sp. – Burrowing mites that live in the hair follicles and sebaceous glands of the skin
Normal flora in most mammals
Immunodeficiency is necessary for infestation to become clinically apparent
Hair loss, thickening of the skin, pustule formation
Diagnosis – deep skin scraping
Cigar-shaped mites
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20. Sarcoptiform Mites (cont.)
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21. Psoroptidae Mites Nonburrowing mites
Live on the surface of skin and feed on keratinized scale, hair, and tissue fluids
Species include Psoroptes, Chorioptes, Otodectes
Psoroptic mange is important in sheep
Chorioptes bovis – important species in cattle
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22. Psoroptidae Mites (cont.)
Cheyletiella and Otodectes are parasites of dogs and cats
Cheyletiella – walking dandruff
Otodectes cynotis – external ear canal
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23. Collection and Diagnosing of Samples
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24. Skin Scraping (cont.)
The scraping is performed with a No. 10 blade with or without a handle
A 165-mm stainless steel spatula may also be used
Hold blade between thumb and forefinger
Dip blade into a drop of mineral oil on a slide
Or a drop may be placed on the skin
Hold blade perpendicular to the skin
Scrape about 3 to 4 cm2
Multiple sites – increases chances of collecting the parasite
Depth depends on suspected parasite
Scrape until capillary blood oozes for Demodex
Spread debris into the drop of mineral oil, apply a coverslip, and scan at x4 objective
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25. Skin Scraping (cont.)
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26. Cellophane Tape Preparation
Diagnosis of surface mites
Clear cellophane tape is applied to the skin to pick up epidermal debris
A ribbon of mineral placed on slide; place tape sticky-side down on mineral oil
Additional mineral oil and a coverslip may be placed on the tape to prevent wrinkling
Examine microscopically
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27. Cellophane Tape Preparation (cont.)
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28. Flea Collection Brush hair with a fine tooth flea comb
Place collected debris on white paper towel
Spray debris with water
If redness appears, dried blood from fleas’ excrement is present
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29. Vacuum Collection
Parasites that are primarily present on the skin surface or on the hair can be collected by a vacuum
Gentle restraint – noise may stress patient
Place filter paper over end of vacuum cleaner attachment
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30. Sample Collection at Necropsy
Collect samples
Ensure they are properly contained, labeled, and shipped
Two methods for recovering samples from the digestive tract
Decanting or sieving
Either method: the different parts must be separated and contents worked with individually
Preserve in 70% alcohol or 10% formalin
Bladder worms – handle with care – maybe zoonotic
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31. Summary Ectoparasites include insects and arachnids
Immature and/or larval stages of nematodes and some adult stages may parasitize an animal’s skin or SQ tissues
Insects that parasitize animals are the orders Hemiptera, Mallophaga, Anoplura, Diptera, and Siphonaptera
Infestation by lice = pediculosis
Infestation by dipterans = myiasis
Infestation by fleas = siphonapterosis
Infestation by mites or tick = acariasis
Ticks are either hard or soft
Sarcoptiform mites burrow into epidermis – sarcoptic or demodex
Nonburrowing mites (Psoroptidae) survive on the surface of the skin
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