External Parasites

External ParasitesSeveral invade all types of small and large animals

They live in hair coat, on skin, or within ear canals

Fleas

Ticks

Lice

Mosquitoes

Biting flies

Mites

Ringworm

FleasMost common external parasite of cat and dog

Small, wingless insect

Adults: reddish brown, hard shells

Lay 15-20 eggs a day; eggs hatch in fall

Flourishes in warm, humid environments of 65-80 degrees

Not host specific and will attack any animal for a blood meal

Intermediate host for the tapeworm

Transmits several diseases including Bubonic plague

Flea - TypesCtenocephalides canis

Ctenocephalides felis

Both species of flea will attack dogs and cats

Flea – Life Cycle Can be as short as 16 days or as long as 2 years

depending on environmental conditions

Female will take a blood meal from host and begin to lay eggs

Eggs are not sticky and fall off host

Depending on conditions, eggs take 2-12 days to hatch

Larvae grow and molt over 9-200 days as they feed on organic matter called “flea dirt” from adult fleas

“Flea dirt” falls off host with eggs

Larvae spin a cocoon and pupate for 7 days to a year depending on conditions

Adult emerges, cycle begins again

Adult fleas can survive several months without feeding

Flea – Clinical SignsFlea allergy dermatitis – severe skin irritation

and itching in some animals due to allergic reaction caused by flea saliva Itching, scratching, biting at skin, hair loss, scabs,

bumps

Anemia – loss of blood

Bartonella – bacteria spread by fleas; common in cats

Hemobartonella or Feline Infectious Anemia – caused by flea bite with bacteria, infects animal’s RBCs and immune system

Fleas - DiagnosisEasiest way to check for fleas is to place a white

piece of paper under the animal’s belly

Rub belly

“flea dirt” will fall from the coat onto the paper

Add water to “flea dirt”

It will turn a reddish

brown indicating fleas

LiceLouse is a small wingless insect

Stick to hair coat

Very host specific

Some species of lice will infest dogs and cats year round

Livestock animals such as horses and cattle are generally infested during the winter

Two types: Mallophaga (chewing) Anoplura (sucking)

Lice – Life Cycle3 – 5 weeks

Must live on its host at all times

Adult louse lays an egg called a nit

Nit is sticky so it attaches to coat

Nit develops into immature stage of the adult called a nymph and then into an adult

Lice – Clinical Signs and Treatment

Adult lice are visible to the naked eye

Louse cause intense itching and may cause hair loss

Treatment is available

MitesMicroscopic parasites

Host specific

Can only infect other animals by direct contact

An animal that has a mite infestation is said to have “mange”

Live on skin and hair coat

Many forms and invade several areas

Mange (Severe Case)

Mites - TypesEar Mites (Otodectes)

Sarcoptic Mange (Sarcoptes) – caused by infection with the Sarcoptes scabei miteCauses condition known as scabies in humansHighly contagious by direct contact

Demodectic Mange (Demodex) – another mite that invades the skin and all dogs raised normally by their mothers possess this mite

Ear Mites

Mite – Life CycleEach species of mite has a different life cycle

Length of life cycle is anywhere from 17 – 35 days depending on the species

All species go through the egg, larva, nymph, and adult stage

Some species of mite burrow into the skin while others live in the ear canal or in hair follicles

Mite – Clinical Signs & Diagnosis

Clinical Signs: Intense itching, oozing of skin, scaly patches without

hair on head and neck area and around elbowsEar mites will cause animal to scratch at its ears and

shake its head in irritation

Diagnosis: Skin scrapingA fold of skin is pinched and scraped with a scalpel

until area oozes with bloodScraping is placed on a microscope slide with a drop of

mineral oil and scanned for mitesFor ear mites, a swabbing of the ear canal is placed on

a slide with mineral oil and examined

TicksBlood-sucking arthropods

Seek heat and movement

Not host specific, although they do have a host preference

Located throughout US in grassy and wooded areas

Vectors for Borrelia burgdorferi, the organism that causes Lyme disease

Common species: American Dog Tick, Deer Tick, Brown Dog Tick, Lone Star Tick, the lxodes species

Ticks - TypesIxodidae – hard ticks

Argasidae – soft ticks

American Dog Tick – transmits disease known as Rocky Mountain Spotted FeverSigns: fever, joint pain, depression, anorexia

Deer Tick – transmits a common disease called Lyme diseaseCauses joint pain, lameness, fever, depression,

anorexia, lethargy, swelling of joints

Babesia – another disease spread by ticksSigns: anemia, jaundice, fever, vomiting

MosquitoesVery small flying insects

Survive on blood

Capable of spreading diseases from animal to animal

West Nile Virus – mosquito-borne disease that causes inflammation or swelling of the brain and spinal cord

Also carry heartworm microfilaria

Biting FliesCan cause lots of irritation

Equine Infectious Anemia – viral disease; no vaccine and no cureCoggins Test – screens for EIA virus

Prevention: use of fly sprays and manure,

waste control and waste removal

are helpful

RingwormDermatophytosis

Fungus on skin

Hair loss, with itching in large patches

Circular skin lesions

Contagious to humans and other animals