6+8+11 Nematodes 1/2/3 Flashcards
What is a definitive host?
The host where adult/sexually mature parasites reside
What is a dead-end host?
A host where the progression of the parasite life cycle ends
What is an intermediate host?
A host that is required for immature or nonreproductive parasites to develop
What is a paratenic host?
An intermediate host where no development happens
What is a patent infestation/infection?
An infection where larvae/eggs are present and can be diagnosed
What is an occult infestation/infection?
An infection where eggs/larvae are not being produced, therefore the parasites are missing key diagnostic features
What is a vector?
An arthropod that transfers a parasite to the definitive host
What are the characteristics of nematodes?
-A pseudocoelom
-A GI tract
-Separate sexes
-A cuticle of varying thickness
What phylum of parasites has separate sexes?
Phylum nematoda
T or F: Most nematodes are pretty small
F - There is HUGE size variation and they can be tiny up to 30 ft long
How do most nematodes migrate in the definitive host?
GI tract –> liver –> lungs –> ascend trachea –> swallowed –> back to GI
What kind of lesions do Ascaris suum and other ascarids produce in the liver?
Milk spots (foci of fibrosis)
At what point are ascarid eggs infective?
Roughly 2 weeks after they are shed, once the eggs are embryonated
Where in the GI tract do Ascaris suum live?
The small intestine
How is Ascaris suum diagnosed?
Fecal float or worms on necropsy
What species does Ascaris suum effect?
Pigs
T or F: ascarid eggs are not hearty in the environment
F; they are very hearty
What species does Parascaris equorum effect?
Horses
T or F: most ascarids are density dependent.
True
What organism causes a “summer cold” (cough, nasal discharge) in horses?
Parascaris equorum
How is Parascaris equorum diagnosed?
Fecal float or worms on necropsy
T or F: Resistance for Parascaris equorum can be acquired.
T, foals are the most susceptible
How is Toxocara canis usually transmitted?
Transplacental or transmammary
How is Toxocara cati usually transmitted?
Transmammary or via infected prey
T or F: Kittens often have Toxocara cati infections.
False
At what life stage are dogs susceptible to Toxocara canis?
Puppies; immunity is reached by 3-6 months and larvae arrest in tissue
At what life stage are cats susceptible to Toxocara cati?
Their entire life
What are the clinical signs of Toxocara in dogs?
Unthrifty, pot belly, rough hair coat
Toxocara spp. (are/are not) zoonotic.
Are
How are Toxocara spp. diagnosed?
Fecal float, worms in vomitus or feces
What species are affected by Toxascaris leonina?
Dogs and cats
Immunity (can/can not) be developed against Toxascaris leonina.
Can not
How do Ancylostoma spp. gain entry to the host?
- Ingestion of infective largae
- Penetration into the skin, tracheal migration, follow lymphatics or vasculature to heart/lungs, coughed up and swallowed
- Transmammary transmission in dogs
What species is most commonly affected by hookworms, and what species affects them?
Dogs - Ancylostoma caninum
Do hookworm eggs hatch in the host or in the environment?
The environment – the larvae enter the host
Which eggs are more environmentally resistant, hookworm larvae or ascarid eggs?
Ascarids – hookworm eggs are susceptible UV and dessication
What are the clinical consequences of Ancylostoma caninum infection?
Hemorrhagic anemia, iron and protein loss, weakness, emaciation, diarrhea, melena
What parasite(s) encyst in the tissue of adult dogs and do not cause active disease?
Toxocara canis
Ancylostoma caninum
What parasite causes summer sores in horses?
Habronema megastoma
How are Habronema spp. transmitted?
Muscid fly maggots ingest eggs from manure and transfer Habronema larvae to lips or oral mucosa
What can infection with Habronema megastoma look like?
Summer sores (sores on skin)
Gastric nodules (larvae deposited on lips by flies are ingested and create nodules in the stomach; usually not causing active dz)
How is Habronema megastoma diagnosed?
Fecal flotation, biopsy, or necropsy
What is the common name of Oxyuris equi?
Pinworm
How is Oxyuris equi diagnosed?
Tape method
How will horses infected with Oxyuris equi present?
Pruritic, unkempt tail, patchy alopecia at tail head
What species do Strongyles most often affect?
Horses
How are cyathostomes transmitted and how do they cause disease?
Eggs are shed in feces and hatch into larvae in the environment. Larvae are ingested along with forage, and cause severe enteritis by emerging from cysts in the GI mucosa.
What are general mechanisms by which large strongyles cause clinical disease?
Larval migration
Blood loss from feeding
What clinical disease does Strongylus vulgaris cause?
Vasculitis
What species of strongyles tend to cause more bleeding?
Strongylus edentatus and Strongylus equinus
How will a horse with a cyathostome infection present?
Diarrhea, emaciation, weight loss
Describe the migration of Strongylus vulgaris within the host.
Ingested larvae –> travel along wall of cranial mesenteric artery –> enter cecum or colon when mature
What can Strongylus vulgaris cause during it’s vascular migration?
Thrombosis and aneurisms
Where do trichostrongyles reside in the host?
Abomasum
What species are most commonly affected by trichostrongyles?
Grazing ruminants
What species are included in the “HOT” complex?
Haemonchus spp.
Ostertagia spp.
Trichostrongylus spp.
What lesions and clinical signs do Haemonchus contortus cause?
Abomasal ulceration, chronic hemorrhage (leading to anemia and edema from hypoproteinemia), ill thrift, “bottle jaw” (edema of the neck d/t head position when grazing)
What is the McMaster technique used for?
Determining parasite burdens (eggs #/gram feces)
_________ __________ (genus and species) is the most important GI nematode of cows.
Ostertagia ostertagia
What does ostertagiasis do to the abomasum?
Interstitial inflammation, mucosal metaplasia and hyperplasia, thickened appearance (may be like “Moroccan leather”), nodules
Describe Type I ostertagiasis and what age/species it affects.
Acute, direct development of larvae, rapidly acquire a lot of larvae that mature at day 21 of the pre-patent period. Affects young cattle in pastures with high contamination.
Describe Type 2 ostertagiasis and what age/species it affects.
Postponed development; larvae go into hypbiotic arrested state in mucosa that later ends. Can occur in older cattle.
How can you differentiate between Thelazia and Ancylostoma when they are affecting the eye?
Thelazia will be on the eye, Ancylostoma will be in the eye
What clinical sign will Thelazia spp. cause?
Conjunctivitis, rarely uveitis
What is the intermediate host for Thelazia spp?
Flies
Halicephalobus gingivalis is a facultative parasite of which species?
Horses and humans
How does Halicephalobus gingivalis infect its host?
Enters via oral abrasions
What body system does Pearsonema plica infect?
The urinary tract
What clinical signs does Pearsonema plica cause?
Cystitis, occasional pyelonephritis
What is the intermediate host for Pearsonema plica?
Earthworms
What is the common name of Stephanurus dentatus?
Swine kidney worm
How are Staphanurus dentatus eggs shed, and what is their vector?
Shed in urine; earthworm is vector
Stephanofilaria stilesi causes what kind of clinical presentation in what species?
Midline dermatitis in cattle
How do you treat Stephanofilaria stilesi?
You don’t; it’s self limiting
What is the intermediate host for Staphanofilaria stilesi?
The horn fly
What species are affected by Onchocerca spp?
Horses and cattle
What clinical presentation does Onchocerca spp. cause?
Dermatitis
What species are MOST affected by Dioctophyme renale?
Dogs and mink
What organ(s) do Dioctophyme renale adults reside in?
The right kidney (because they migrate out of the duodenum. If you infect both kidneys, the host dies)
Dioctophyme renale requires an __________ (intermediate host species) and ___________ (paratenic host species).
Aquatic oligochaete; fish/frog/other small aquatic creature
What parasite species can cause zoonotic cutaneous larval migrans?
Ancylostoma caninum
What parasite species can cause zoonotic ocular larval migrans?
Toxocara canis and toxacara cati
Which parasite species can cause zoonotic visceral larval migrans?
Toxocara canis
Toxocara cati
Baylisascaris procyonis
Where are lungworms eggs or larvae shed?
Feces
How are lungworms diagnosed?
Baermann apparatus
Why is Parelaphostrongylus tenuis dangerous in aberrant hosts?
Larvae get lost in the CNS
Meningeal worms are a major issue in ______ (wildlife species) and can cause infections in ________ (domestic species).
White tailed deer; camelids
What do Muellerius capillaris lesions look like?
Small granulomatous nodules on the dorsal aspect of the lungs
What is the intermediate host for Muellerius capillaris?
Snail or slug
What species is affected by Muellerius capillaris?
Goats
What species are affected by Dictyocaulus spp?
Ruminants and horses
What clinical disease does Dictyocaulus viviparous cause?
Bronchointerstitial pneumonia and bronchitis, atelectasis, edema, emphysema
Where do Dictyocaulus viviparous live in their host species?
In the mainstem bronchi or distal trachea
Describe the lifecycle of lungworms.
Adult worms lay eggs in the lungs, which are then coughed up and swallowed. Larvae pass in feces then leave the fecal matter to crawl onto vegetation in their infective L3 stage. After ingestion, larvae migrate back to the lungs and mature.
What age of animal is most likely to present with dictyocauliasis, and how will they present?
Young animals present with tachypnea, splayed-leg posture, and dependent head position
What species are infected with Aeleureostrongylus abstrusus?
Cats
What species of intermediate hosts do lungworms require?
Slugs or snails
What clinical disease does Aeleurostrongylus abstrusus cause?
Multifocal interstitial pneumonia
T or F: Dirofilaria immitis are lungworms.
T
Describe the life cycle of heartworm.
Adult worms in pulmonary arteries produce microfilaria that enter vasculature –> mosquito takes bloodmeal from infected animal –> L1 larvae migrate to the mosquito’s midgut and develop to L3 –> L3 larvae migrate to head/proboscis –> L3 larvae enter new host when the mosquito takes a blood meal –> adult worms live in pulmonary artery
What is the difference between a cat with 1-2 adult heartworms and a dog with 1-2 adult heartworms?
This amount of worms can be fatal in the cat
Heartworm infection in cats is typically _______ (patent/occult).
Occult
What types of lesions and clinical disease can heartworms cause?
Arterial endothelium and smooth muscle thickening, possible thromboembolism, pulmonary hypertension, R sided heart failure, coughing/dyspnea, ascites, exercise intolerance
How long can Dirofilaria immitis microfilaria survive in the vasculature?
Up to 2 yrs
Can you treat a cat for heartworm?
No, due to the thromboembolic implications
If you were to transfuse microfilaria-infected blood from one dog into a recipient dog, would the recipient dog develop a heartworm infection? Why or why not?
No, because the microfilaria MUST pass through the mosquito to be infective
Why is it important to know about Dipetalonema reconditum?
Because it is non-pathogenic, but looks like heartworm microfilaria on blood smears
What is the common name of Trichuris spp.?
Whipworms
Where do adult and larval Trichinella spiralis live?
Adult –> small intestine
Larvae –> encysted in muscle
How do you get trichinellosis?
Ingestion of encysted Trichenella spiralis larvae in meat
T or F: Ancylostoma caninum migrates through the liver.
False
