External parasites 1

What phylum do external parasites discussed in clinical pathology belong to?

Phylum Arthropoda

How large is the phylum Arthropoda?

One of the largest phyla with over 1 million species

Name examples of arthropods.

Spiders, mites, fleas, ticks, lice, crabs, lobsters, beetles, ants, mosquitoes

What does "arthropod" mean?

Jointed foot

What do all adult arthropods have?

Jointed appendages

What substance makes up the arthropod exoskeleton?

Chitin

What is hemolymph?

Blood-like fluid that bathes internal organs

What is the function of the dorsal tube in arthropods?

Acts as the heart

Describe the digestive system of arthropods.

Complete system with ventral mouth and terminal anus

What types of respiratory systems do arthropods have?

Gills, lungs, or tracheal tubes

What is unique about arthropod reproduction?

Dioecious (separate sexes) with high reproductive capacity

Why are arthropods important in veterinary medicine?

They can cause disease, serve as intermediate hosts, or act as vectors

What class do mites and ticks belong to?

Arachnida

How many body segments do arachnids have?

Two

How many pairs of legs do arachnids have?

Four pairs

Are mites and ticks insects?

No

What order do mites and ticks belong to?

Acarina

What is acariasis?

Infestation of mites or ticks

What are the two body components of mites and ticks?

Capitulum and body

What is the capitulum?

Mouthparts used to attach and feed

What features do mites and ticks lack?

Antennae, wings, and eyes

What are the four life stages of mites and ticks?

Egg, larva, nymph, adult

What class do lice belong to?

Insecta

What are the two orders of lice?

Mallophaga (chewing) and Anoplura (sucking)

What is the body shape of lice?

Dorsoventrally flattened

Do lice have wings?

No

What structures are on the head of lice?

Mouthparts and antennae

What is found on the thorax of lice?

Three pairs of legs, no wings

What hosts do chewing lice (Mallophaga) infect?

Mammals and birds

Are chewing lice zoonotic?

No

What distinguishes chewing lice from sucking lice?

Smaller size, large round head wider than thorax

What are chewing lice mouthparts adapted for?

Chewing/biting

How do chewing lice move on hosts?

Rapid movement and clasping hair/feathers

What hosts do sucking lice (Anoplura) infect?

Domestic animals (not cats or birds)

Are sucking lice zoonotic?

No

What distinguishes sucking lice?

Larger, narrow head, red/gray color depending on blood

What are sucking lice mouthparts adapted for?

Piercing and sucking

How are lice transmitted?

Direct contact or fomites

What is a nit?

Egg stage of lice attached to hair or feathers

How long do lice eggs take to hatch?

5-14 days

How long is the nymph stage of lice?

2-3 weeks

How long can lice survive off the host?

Less than 7 days

What is pediculosis?

Lice infestation

Which animals are most susceptible to lice?

Young, old, malnourished, stressed, overcrowded

What severe condition can sucking lice cause?

Anemia, possibly fatal

How are lice diagnosed?

Hair clippings, visual exam, microscopy

What is the goal in lice identification?

Determine chewing vs sucking lice

What is Diptera?

Order of two-winged flies

What is myiasis?

Infestation by fly larvae in tissues

What animals are the primary hosts of Cuterebra?

Rabbits, rodents, squirrels

What animals are accidental hosts for Cuterebra?

Dogs, cats, ferrets

What do adult Cuterebra flies look like?

Large and bee-like

How do Cuterebra larvae enter the host?

Through mouth, nose, or wounds

Do Cuterebra larvae create their own wound?

No

Where do Cuterebra larvae develop?

Subcutaneous tissue

How do larvae breathe?

Through a breathing pore

How long before Cuterebra larvae exit the host?

About 30 days

What happens after larvae leave the host?

Pupate in soil

Do adult Cuterebra flies feed?

No

What are common signs of Cuterebra infestation?

Subcutaneous cyst with breathing hole

How is Cuterebra treated?

Remove larvae intact

What are fleas physically like?

Small, laterally compressed, wingless

What allows fleas to jump?

Powerful hind legs

What do fleas feed on?

Blood

What is the most common flea species?

Ctenocephalides felis

How long can adult fleas live on a host?

60-100 days or longer

How many eggs can fleas lay?

Thousands in a lifetime

What do flea eggs look like?

Small, white, oval, non-sticky

What do flea larvae feed on?

Organic debris and flea feces

What triggers flea emergence from pupae?

Heat, vibrations, air pressure

What is flea dirt?

Flea feces (digested blood)

What is flea allergic dermatitis?

Allergic reaction to flea bites causing itching

What diseases can fleas transmit?

Mycoplasma, tapeworms, bubonic plague

How do fleas cause anemia?

Blood loss from feeding

How are fleas controlled in the environment?

Yard sprays, house treatments

What are common flea treatments for animals?

Monthly preventatives, Capstar

What are sarcoptiform mites known for?

Causing dermatitis and pruritus

What are the two families of sarcoptiform mites?

Sarcoptidae and Psoroptidae

What do Sarcoptidae mites do?

Burrow into skin

What do Psoroptidae mites do?

Live on skin surface or ear canal

What is Sarcoptes scabiei?

Scabies (mange) mite

Is Sarcoptes scabiei zoonotic?

Yes

What is pseudoscabies?

Temporary human infestation

What is sarcoptic mange?

Skin disease caused by Sarcoptes mites

What are clinical signs of sarcoptic mange?

Intense itching, alopecia, sores

How is sarcoptic mange diagnosed?

Skin scraping with microscopy

What is the life cycle length of Sarcoptes?

2-3 weeks

What treatments are used for sarcoptic mange?

Selamectin, moxidectin, imidacloprid

What is Demodex?

Mite normally found in hair follicles

Is Demodex zoonotic?

No

Where does Demodex live?

Hair follicles and sebaceous glands

When does Demodex cause disease?

When populations overgrow

What are forms of demodectic mange?

Localized and generalized

What are signs of localized Demodex?

Patchy alopecia

What are signs of generalized Demodex?

Diffuse alopecia, infections

How is Demodex diagnosed?

Deep skin scrape with bleeding

What treatments are used for Demodex?

Isoxazolines (Nexgard, Bravecto, Simparica), amitraz dips

What are side effects of amitraz?

Sedation, incoordination, bradycardia, seizures