Parasitology

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created 5 years ago by Anne_Hensley89
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Parasitology
updated 5 years ago by Anne_Hensley89
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1

Nematodes

"Roundworms"; cylindrical; multicellular; one straight tube from mouth to anus

2

Nematode Life Cycle

Egg, 4 larval stages, sexually mature adult

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Infective Stage

Egg containing a larva, free living larva, or larva within an intermediate host

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Direct Stage

No intermediate host is needed for development to the infective stage

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Indirect Stage

Intermediate host is required for development to the infective stage

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Once a nematode gains entry to a new host:

Development may occur in the area of its final location or may occur after extensive migration through the body of the definitive host

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Diagnostic stages

Most found in feces, blood, sputum, or urine
Some in lungs, kidney, urinary bladder, or heart

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"Somatic migration"

larva reside or hibernate in muscle tissue; once pregnancy occurs, the larva reappear

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Ascarids

Toxocara canis, Toxocara cati, Toxascaris leonina

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Toxocara canis

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Dogs: thick & mamillated

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Toxocara cati

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cats

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Toxascaris leonina

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both dogs and cats "ground glass" appearance
smooth outer shell; T. leonina development to adults takes place in the intestines w/o a migratory phase
Eggs can be embryonated or non-embryonated

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Parascaris equorum

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equ caninumine roundworm

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Toxacara vitulorum

cattle roundworm

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Ascaris suum

swine roundworm

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Strongyloids: small intestine parasites

Hookworms; attach to the small intestine

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Ancylostoma caninum

canine hookworm; most common; widest range; WARM/HOT regions

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Ancylostoma tubaeformae

feline only hookworm

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Ancylostoma braziliense

both canine & feline hookworm

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Uncinaria stenocephala

northern canine hookworm; COOLER regions; require less blood than Ancylostoma
Treat w/ ivermectin, milbemycin oxime, pyrantel pamoate, dichlorvos

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Bunostomum phlebotomum

ruminant hookworm

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Strongyloid Lifecycle

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oval/ellipsoid w/thin walls & 8 - 16 cells; lives in the cecum & lg intestine; may damage the MESENTERY ARTERY

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Hookworms produce...

severe anemia (by draining the RBCs of the host) in puppies and kittens. Are found throughout the world, but are common in tropical and subtropical regions if North America

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Large intestine strongyles of the horse include

Strongylus vulgaris, S. equinus, S. edentatus,

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Trichuris vulpis

canine whipworm

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Capillaria plica AKA Pearsonema plica

bladderworm of both dogs & cats

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Oxyuris equi

horse pinworm

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Pinworms are parasites of omnivores and herbivores, but never

carnivores

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Thelazia californiensis

eyeworm of the dog

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Dioctophyma renale

giant kidney worm of dogs

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Stephanurus dentatus

swine kidney worm

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Dirofilaria immitis

most important parasite of the vascular system in domestic animals in the US

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Common nematode parasites of dogs and cats are

Toxocara, Ancylostoma, Trichuris, and Dirofilaria immitis

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Nematodes are most commonly found in the

digestive, respiratory, & circulatory systems

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Visceral larval migrans

when humans ingest Toxocara eggs

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Toxocara lifecycle

Ingestion of the egg containing L2 larva; transplacental migration; digested in sm intestine & penetrate wall; larvae are carried to the liver & lungs via circulation. This forms infection & tracheal migration.

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Somatic migration lifecycle

Occurs in dogs > 3 mos of age; carried by pulmonary circulation; female larvae are mobilized in the last 3 weeks of gestation, migrate into the vasculature, cross the placenta, and infect the lungs of the fetus. Infected pups can pass eggs in feces @ 3 wks and can sere as a source of infection for other animals.

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Lactogenic and paratenic infections

Thru the milk; no migration is involved

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Toxocara canis head is shaped like

an arrowhead

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Treatment for T. canis:

fenbendazole, mebendazole, ivermectin, piperazine, pyrantel (yellow from MAC), dichlorvos

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Visceral Larva Migrans

few in the liver = no or overt symptoms
few in the eye = blindness or neurological disorders

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Baylisascaris procyonis

raccoon roundworm; can cause visceral larval migrans

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Ascarids of dogs and cats

Toxocara canis, Toxocaris felis, Toxascaris leonina

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Toxocara cati lifecycle

differs from T. canis: paratenic host (ie mice) plays a more significant role; prenatal infection does NOT occur; more tracheal migration; main transmission route is TRANSMAMMARY

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Whipworms

Trichuris spp.; lives in colon's mucus

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Trichuris vulpis

canine whipworm disease

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Feline whipworm

is very rare

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Trichuris suis

swine whipworm

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Trichuris egg appearance

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polar plugs @ each end; tan; harder to float; sentinel

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Trichuris treatment

fenbendazole, albendazole, febantel paste. PYRANTEL CANNOT TREAT WHIPWORMS

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Ascaris suum

pig roundworm; one of the most common and one of the largest; migrating larva in the liver cause "MILK SPOTS"

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Parascaris equorum

equine roundworm; found in sm intestine of horses/zebras. Infections are mainly found in nursing and weaned foals. Can be passed transplacentally.

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Strongylus vulgaris treatment

invermectin (larva & adults), thiabendazole (larvae), and fenbendazole (adults)

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Ancyclostoma

more common in the temperate and tropical regions; can infect humans through cutaneous larval migration; somatic migration;

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Ancyclostoma when percutaneous infection occurs,

larvae migrate to the lungs. Very rarely does transplacental infection occur.

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Ancyclostoma: transmammary only for

Ancyclostoma caninum

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Ancyclostoma: @ the time of delivery, the larvae develop

in the pup's intestine & can cause hemorrhagic anemia. Clinical signs: black tarry stool or melena, indicating blood in the stool

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Hookworm =

anemia

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Ancyclostoma treatment:

ivermectin, milbemycin xoime[Interceptor], pyrantel pamoate [strongid], dichlorvos

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Which is more severe w/blood loss?

Ancylostoma

61

Which requires a cooler temperature?

Uncinaria stenocephala

62

Heartworm meds & tradenames

Advantage Multi: imidacloprid
Heartgard: ivermectin
Heartgard Plus: ivermectin + pyrantel
Interceptor: milbemycin oxime
Iverhart Max: ivermectin, praziquantel, pyrantel pamoate
Revolution: selamectin
Sentinel: milbemycin oxime and lufenuron