Parasitology Exam 1 Study guide

Parasite

Smaller organism living at expense of a host.

Symbiotic relationships

Mutualism, Commensalism, and Parasitism

Mutualism

Both benefit

Commensalism

One benefits, other unaffected

Parasitism

Parasite benefits, host harmed

Endoparasite

Inside host (infection)

Ectoparasite

Outside/on skin (infestation)

Obligate parasites

Require host; facultative are opportunistic

Hosts:

Definitive, Intermediate, Paratenic, and Reservoir

Definitive

Sexual stages occur

Intermediate

Development of larval stages

Paratenic

No development, but parasite persists

Reservoir

Cycles parasite outside host of interest

Vectors:

Mechanical, and Biological

Mechanical

Contaminated transport only

Biological

Parasite develops in vector

• Epidemiology:

Prevalence, Incidence, Endemic/Zoonotic, and Epidemic/epizootic

Prevalence

Percent infected at a time

Incidence

New cases over time

Endemic/enzootic

Stable presence

Epidemic/epizootic

Outbreak above normal

Zoonoses:

Zoonosis, Anthropozoonosis, and Zooanthroponosis

Zoonosis

Animal → Human

Anthropozoonosis

Human → Animal (e.g., TB)

Zooanthroponosis

Human → Animal (reverse zoonosis)

Species (fleas)

Ctenocephalides felis (cat flea, most common), Xenopsylla (rat flea).

PPP (fleas)

Egg → adult 14–140 days depending on temp/humidity.

Lifecycle (fleas):

Eggs laid on host, fall into environment.

Larvae feed on flea feces (dried blood) & debris.

– Pupae develop in cocoons, emerge with host stimuli.

Environmental factors (Fleas):

55–90°F optimal, >95°F lethal to larvae/pupae.

Organs affected (fleas):

Skin – irritation, anemia in heavy infestations.

Clinical signs (fleas):

Itching, hair loss, anemia in small animals, flea allergy dermatitis.

Disease transmission (fleas):

Dipylidium caninum (tapeworm).

Bartonella henselae (cat scratch disease).

Rickettsia typhi, R. felis, Yersinia pestis (plague via rat flea).

Treatment (fleas):

Topical/oral insecticides: isoxazolines, fipronil, imidacloprid, selamectin.

Environmental control: vacuuming, wash bedding, boric acid in carpets, steam cleaning.

Zoonotic potential:

Plague, cat scratch fever, murine typhus.

Families (ticks):

Ixodidae (hard ticks), Argasidae (soft ticks).

PPP (ticks):

Weeks–months, varies by species and host availability.

Lifecycle

egg → larva → nymph → adult (all blood-feeding).

Feeding (ticks):

Cement-like substance secures mouthparts, risk of retained mouthparts.

Transmission (ticks):

Transovarial (female → eggs) or interstadial (stage to stage).

Organs affected (ticks):

Blood loss, bite sites, possible paralysis (neurotoxin).

Clinical signs (ticks):

Anemia, tick paralysis, irritation, secondary infections.

Important genera & diseases (ticks):

Ixodes, Rhipicephalus sanguineus, Dermacentor variabilis, Amblyomma americanum, and Haemaphysalis longicornis.

Ixodes (ticks)

Lyme disease (Borrelia burgdorferi), Anaplasma.

Rhipicephalus sanguineus (ticks)

Babesia, Ehrlichia, and RMSF.

Dermacentor variabilis (ticks)

RMSF, tularemia, and tick paralysis.

Amblyomma americanum (ticks)

Ehrlichia, Cytauxzoon felis, and red meat allergy (alpha-gal).

Haemaphysalis longicornis (ticks)

Theileria orientalis, and can clone itself (parthenogenesis).

Treatment (ticks):

Isoxazolines (afoxolaner, fluralaner, sarolaner), permethrin (not cats), amitraz, fipronil.

Control (ticks):

Pasture burning, acaricides, removal of hosts, and pet treatment.

Zoonotic potential (ticks):

Lyme disease, RMSF, ehrlichiosis, and tularemia.

Mosquitoes scientific name:

Culicidae

PPP (Mosquitoes):

egg → adult in 1–3 weeks depending on water temp.

Lifecycle (Mosquitoes):

eggs laid on water; larvae are aquatic; pupae free-swimming.

T/F: Only females feed on blood (protein for ovaries).

True

Diseases (Mosquitoes):

Heartworm, and arboviruses (WNV, Zika, etc.).

Organs affected (Mosquitoes):

Skin, blood, and transmit systemic disease.

Blackflies scientific name:

Simuliidae

Where do Blackflies (Simuliidae) breed?

In running water; females lacerate skin to pool blood.

Clinical signs (Blackflies):

Hypersensitivity, dermatitis, anemia, and death in nestlings.

Control (Blackflies):

Repellents, stabling animals, petroleum jelly on ears, and fly masks.

Horseflies & Deerflies scientific name:

Tabanidae

PPP (Tabanidae):

One generation per year; larvae overwinter.

T/F: (Tabanidae) Females require a nectar meal, males feed on blood.

False

Clinical signs (Tabanidae):

Painful bites, blood loss, and mechanical disease transmission.

Houseflies & Face Flies scientific name:

Muscidae

PPP (Muscidae):

Eggs hatch in <24h; adult in 2–3 weeks.

Where are Muscidae lay their eggs?

Eggs are laid in manure/organic material.

Transmission (Muscidae):

Mechanical vectors (pinkeye)

Control (Muscidae):

Insecticides, sanitation, and growth regulators in feed.

Blowflies scientific name:

Calliphoridae

• Cause myiasis (Blowflies):

Primary = obligate, secondary = opportunistic

What does do Blowflies cause?

Wool strike in sheep, wounds in dogs/cattle

Clinical signs (Blowflies):

Tissue destruction, foul odor, secondary infections.

Treatment (Blowflies):

Wound cleaning, insecticides, and ivermectin.

Botflies scientific name(s):

Oestridae, Cuterebra, Gasterophilus

T/F: Larvae migrate subcutaneously or to organs (stomach in horses).

True

Clinical signs (Oestridae, Cuterebra, Gasterophilus):

Swelling, oral lesions, stomach ulcers, rupture, and abscesses

• Treatment (Oestridae, Cuterebra, Gasterophilus):

Remove larvae carefully, ivermectin, and grooming.

• Sarcoptes scabiei (mites):

Causes scabies in dogs, humans, livestock (reportable in cattle). PPP: 10–14 days.

• Clinical signs (mites):

Intense pruritus, thickened crusty skin, secondary pyoderma.

Notoedres (mites):

Face mange in cats, rabbits, rats; signs = pruritus, crusts, self-mutilation.

Otodectes cynotis (mites):

ear mite in dogs/cats; signs = dark cerumen, scratching ears.

Demodex canis (mites):

Commensal in dogs; causes demodicosis in immunocompromised/puppies; alopecia around eyes/mouth.

Knemidokoptes (caused by mites):

Scaly leg in chickens.

Treatment (mites):

Selamectin, ivermectin, isoxazolines, and disinfect environment.

• Suborders (lice):

Anoplura (blood-sucking) vs Mallophaga (chewing).

T/F: Lice are not host-specific?

False

PPP (lice):

~3 weeks from egg → adult.

Clinical signs (lice):

Pruritus, anemia, poor coat, weight loss.

Transmission (lice):

Direct contact, crowding, and poor husbandry.

Treatment (lice):

Imidacloprid, fipronil, selamectin, and livestock dips (coumaphos, pyrethrins).

Zoonotic (lice):

Generally not zoonotic, but human lice transmit typhus.

What disease can insects carry?

Trypanosomiasis (tsetse), leishmaniasis (sandfly), myiasis (blowflies).

What skin disease can mites cause?

Sarcoptes scabiei = zoonotic mange.

What can human lice transmit that dog/cat lice cannot?

human lice transmit epidemic typhus (not dog/cat lice).