Nematodes (Roundworms) Flashcards
Ascaroidea (Ascarids)
What are the Ascarids of dogs and cats?
Toxocara canis
Toxocara cati
Toxocara leonina
Where are Ascarids (roundworms) found?
Small intestine of dogs and cats
Most areas of the world
What do adult Ascarids look like?
3cm to 18cm in length
Usually tightly coiled when passed.
What do eggs of Toxocara spp. look like?
Spherical
Deeply pigmented center
Rough pitted outer shell
What is the prepatent period of Toxocara canis?
21 - 35 days
What is the prepatent period of Toxocara leonina?
74 days
What is the “equine ascarid” or the “equine roundworm?”
Parascaris equorum
What is the prepatent period of Parascaris equorum?
75 to 80 days
What do eggs of Parascaris equorum look like?
Oval
Brown
Thick shell
Finely granular surface
90 to 100um
Center of egg contains 1 or 2 cells
Recovered with fecal flotation
Where is Toxocara (Neoascaris) vitulorum found?
Calves
Where are Ascaris suum found?
Small intestine of swine
What do eggs of Ascaris suum look like?
Oval
Golden brown
Thick albuminous shell that bears prominent projections
70 to 80um by 37 to 40 um
What is the common name for Strongyloidea?
Hookworms
What is the canine hookworm called?
Ancylostoma caninum
What is the feline hookworm called?
Ancylostoma tubaeforme
What is a hookworm common to both dogs and cats?
Ancylostoma braziliense
What is the northern canine hookworm?
Uncinaria stenocephala
What is the hookworm of ruminants?
Bunostomum phlebotomum
What do eggs of all hookworms look like?
Oval or ellipsoid
Thin walls
Contain 8 to 16 cells when passed in feces
Recovered in standard fecal flotation
What is the general term for nematodes that parasitize the large intestine of horses?
Strongly es
What are the large strongyles?
Strongyloidea vulgaris
Strongylus edentatus
Strongylus equinus
What do strongyle eggs look like?
Contain an 8 to 16 cell morula
70 to 90um by 40 to 50 um
What is the nodular worm of swine?
Oesophagostomum dentatum
What is the prepatent period of Oesophagostomum dentatum?
50 days
What do eggs of Oesophagostomum dentatum look like?
trichostrongyle type = oval, thin shelled
Contain 4 to 16 cells
40um by 70um
Fecal flotation
Where are bovine trichostongyle nematodes found?
Within the abomassum and the small and large intestines of cattle and other ruminants.
What are the 7 genera of nematodes that produce trichostrongyle-type eggs?
Bunostomum Cooperia Chabertia Haemonchus Oesophagostomum Ostertagia Trichostrongylus
What do the eggs of bovine trichostrongyles look like?
Oval Thin shelled Contain 4 or more cells 70 to 120um long identification of exact species usually involves fecal culture and larval identification
What 2 species of trichostrongyles have much larger eggs?
Nematodirus
Marshallagia
What is the lungworm species of cattle?
Dictyocaulus
What are the lungworms of cattle called
Dictyocaulus viviparus
What are the lungworms of sheep and goats?
Dictyocaulus filaria
Where are adult Dictyocaulus found in the animal?
Bronchi
What is the equine lungworm called?
Dictyocaulus arnfieldi
What is the usual prepatent period of Dictyocaulus?
28 days
What is the ‘red stomach worm” of swine?
Hyostrongylus rubidus
What do the Hyostrongylus rubidus eggs look like?
trichostrongyle type
contain 4 or more cells
71um to 78um by 35um to 42um
recovered with fecal flotation
What is the prepatent period of Hyostrongylus rubidus?
20 days
What is the name of the “feline trichostrongyle?”
Ollulanus tricuspis
What is the main symptom of cats who have Ollulanus tricuspis?
vomiting
What are the names of the 3 “intestinal threadworms?”
Strongyloides stercoralis
Strongyloides tumefaciens
Strongyloides papillosus
What is Rhabditoidea?
Threadworms
How are the Strongyloides spp. unique?
Only a parthenogenetic female is parasitic
What does parthenogenetic mean?
Can lay eggs without copulation with a male
What is the parthenogenetic life cycle of female nematodes?
Produce eggs
Eggs hatch in the intestine of dog and release first-stage larvae.
What do larvae of Strongyloides look like?
280um to 310um long
Have a rhabditiform (club-shaped espphagus) with a club-shaped cranial corpus.
Have a narrow medium isthmus and a caudal bulb
What is the prepatent period of Strongyloides?
8 to 14 days
What is the intestinal threadworm of horses?
Strongyloides westeri
What do Strongyloides westeri eggs look like?
larvated
40um to 52um by 32um to 40um
How are Strongyloides westeri eggs recovered?
fecal flotation of fresh feces
What is the prepatent period of Strongyloides westeri?
5 to 7 days
What is the intestinal threadworm of pigs?
Strongyloides ransomi
Eggs of Strongyloides ransomi
larvated eggs
45um to 55um by 26um to 35um
How eggs of Strongyloides ransomi recovered?
fecal flotation of fresh feces
Prepatent period of Strongyloides ransomi?
3 to 7 days
Metastrongyloides?
Lungworms
What is the “hair lungworm”?
Muellerius capillaris
Where are adult Muellerius capillaris found?
In bronchioles (nodules in lung parenchyma) of sheep and goats
Where do eggs develop and how are larvae shed?
Eggs develop in lungs of definitive host
Larvae are coughed up, swallowed, and passed out in feces?
Muellerius capillaris larvae?
230um to 300um long
Tail has an undulating tim and dorsal spine
What are the Protostrongylus species?
Lungworms of sheep and goats
Where are Protostrongylus found?
small bronchioles of sheep and goats
Eggs and larvae of Protostrongylus?
Develop in lungs of sheep and goats
Larvae coughed up, swallowed, and passed out in feces.
What do Protostrongylus larvae look like?
250um to 320um
undulating tip
no dorsal spine
Diagnosis of lungworm in ruminants?
Baermann technique
What is the swine lungworm?
Metastrongylus apri
Where are Metastrongylus apri found?
bronchi and bronchioles of swine
Eggs of Metastrongylus apri?
oval
thick walled
60um by 40um
contain larvae
Recovery of Metastrongylus apri eggs?
fecal flotation using flotation medium with specific gravity of more than 1.25 or
fecal sedimentation technique
Prepatent period of Metastrongylus apri?
24 days
What are the 3 lungworms of canines?
Filaroides (Oslerus) osleri
Filaroides hirthi
Filaroides milksi
Where are canine lungworms found?
trachea
lung
parenchyma
bronchioles
Larvae of Filaroides?
232um to 266um long
short S-shaped tail
How are Filaroides species unique among nematodes?
Their first stage larvae are immediately infective for the canine definitive host.
No period of development is required outside the host.
Diagnosis of Filaroides?
fecal flotation or
Baermann technique
Nodules of Filaroides osleri found?
at the bifurcation of the trachea where they can be observed by endoscopic examination.
Prepatent period of Filaroides osleri?
10 weeks
What is the lungworm of feline?
Aelurostrongylus abstrusus
Where are Aelurostrongylus abstrusus found?
in the terminal respiratory bronchioles and alveolar ducts where they form small egg nests or nodules.
Eggs of Aelurostrongylus?
Eggs forced into lung tissue where they hatch
Larvae of Aelurostrongylus abstrusus?
360um long
tail with S-shaped bend
dorsal spine
Diagnosis of Aelurostrongylus abstrusus?
larvae found with:
fecal flotation
Baermann technique
tracheal washing
Prepatent period of Aelurostrongylus abstrusus?
30 days
Trichuroidea (Trichuris spp., Eucoleus spp., and Trichinella sprialis)?
whipworms
Canine whipworm?
Trichuris vulpis
2 feline whipworms?
Trichuris campanula
Trichuris serrata
Where do Trichuris spp. live?
cecum and colon of hosts
Which are more common? Canine or Feline whipworms?
Canine
What do whipworms look like?
thin, filamentous cranial end (lash of the whip)
thick caudal end (handle of the whip)
Egg of whipworm?
trichinelloid or trichuroid thick shell yellow-brown symmetric polar plugs at both ends unembryonated (not larvated) when laid
Eggs of Trichuris vulpis?
70um to 89um by 37um to 40um
Prepatent period of Trichuris vulpis?
70 to 90 days
Eggs of Trichuris campanula?
63um to 85um by 34um to 39um
What should vet tech’s be aware of when examining feline feces for Trichurids?
pseudoparasites
the eggs of trichurids or capillarids frequently parasitize an outdoor cat’s prey via hosts such as mice, rabbits, or birds. The eggs of these trichurids or capillarids may pass unaltered through the cat’s GI system, remaining intact and unembryonated, thus appearing to infect feline host.
Ruminant whipworm?
Trichuris ovis
Trichuris ovis located?
cecum and colon of ruminants
Eggs of bovine whipworms?
50um to 60um by 21um to 25um
Swine whipworm?
Trichuris suis
Trichuris suis eggs?
50um to 60um by 21um to 25um
Prepatent period of Trichuris suis?
42 to 49 days
What is the gastric capillarid of cats?
Aonchotheca putorii
Former name of Aonchotheca putorii?
Capillaria putorii
Eggs of Aonchotheca putorii?
easily confused with eggs of other trichinelloid nematodes
53um to 70um by 20um to 30um
netlike surface (similar to Eucoleus aerophilus, an upper respiratory capillarid)
dense
organized in longitudinal formation
flattened sides
contain a one or two cell embryo that fills the egg
Capillarid nematode found in trachea and bronchi of both dogs and cats?
Eucoleus aerophilus (Capillaria aerophila)
Prepatent period of Eucoleus aerophilus?
40 days
Eggs of Eucoleus aerophilus?
in standard fecal flotation, eggs are often confused with Trichuris (whipworm) eggs.
eggs are smaller than whipworm eggs (59-80um by 30-40um)
more broadly barrel shaped
lighter in color
has rough outer surface with netted appearance
Capillarid nematode found in nasal cavity and frontal sinuses of dogs.
Eucoleus boehmi
Eggs of Eucoleus boehmi?
smaller and have smoother outer surface than Eucoleus aerophilus eggs.
shell has pitted appearance
Diagnosis of Eucoleus boehmi?
standard fecal flotation
Nematode of urinary bladder of dogs?
Pearsonema (Capillaria) plica
Nematode of urinary bladder of cats?
Pearsonema (Capillaria) feliscati
Eggs of Pearsonema?
found in urine or feces contaminated with urine
clear to yellow in color
63um to 68um by 24um to 27um
flattened bipolar end plugs
roughened outer surface
may be confused with respiratory and gastric capillarids or with whipworm eggs
Nematode associated with raw or undercooked pork?
Trichinella spiralis
How do animals become infected with Trichinella spiralis?
they ingest infective larval stages (juveniles) in meat.
Life cycle of Trichinella spiralis?
larvae mature into adults in host’s small intestine within a few weeks
female worms give birth to larvae
males die after fertilizing the females
females die after producing larvae
larvae enter bloodstream of host and end up in pig’s musculature
within the muscles the larvae mature into infective encysted larvae
next host becomes infected when it eats the larvae
What is the pinworm family?
Oxyuridea
What is the pinworm of horses?
Oxyuris equi
Where are adult Oxyuris equi found?
cecum
colon
rectum
often seen observed protruding from horse’s anus with a sticky gelatinous material that produces anal puritus
Eggs recovered from Oxyuris equi?
feces
Oxyuris equi eggs?
90um by 40um
smooth, thick shell
operculated and slightly flattened on one side
may be larvated
Prepatent period of Oxyuris equi?
4 to 5 months
Diagnosis of Oxyuris equi?
finding characteristic eggs using microscopic examination of cellophane tape impressions or
scraping the surface of the anus
What is the human pinworm?
Enterobius vermicularis
Does Enterobius vermicularis parasitize dogs or cats?
No
What rule about pinworms should vet techs remember?
pinworms are parasites of omnivores (mice, rats, monkeys, humans) and herbivores (rabbits, horses) never carnivores (dogs, cats)
2 Nematodes found in stomach of horses?
Habronema species
Draschia megastoma
What 2 Habronema species are found on the stomach mucosa, just beneath a thick layer of mucus?
Habronema microstoma
Habronema muscae
Which Habronema species is associated with thickened, fibrous nodules within the stomach mucosa?
Draschia megastoma
What are “summer sores?”
Larvae of Habronema and Draschia that have parasitized skin lesions.
Prepatent period of Habronema and Draschia?
60 days
Recovery of larvated eggs or larvae in Spiruroidea (Habronema and Draschia)?
standard fecal floatation
Eggs of Habronema and Draschia?
elongated
thin walls
40um to 50um by 10um to 12um
What is the eyeworm of dogs and cats?
Thelazia californiesis
Recovery of adult Thelazia californiensis?
from conjunctival sac and lachrymal duct
What might lacrymal secretions reveal in parasitized dog or cat?
Thelazia californiensis eggs or first stage larvae
Eyeworm of horses?
Thelazia lacrymalis
Esophageal worm of dogs and cats?
Spirocerca lupi
Life cycle of Spirocerca lupi?
Adult worm forms nodules (granulomas) in esophageal wall.
Adult worms reside deep in these nodules
Expel eggs through fistulous openings in the granuloma
Eggs passed into lumen of host animal’s esophagus and passed out in feces
Eggs of Spirocerca lupi?
thick shelled
30um to 38um by 11um to 15um
contain larvae when laid
unique paperclip shape
Diagnosis of Spirocerca lupi?
standard fecal floatation
vomitus subjected to standard fecal floatation procedure
radiographic or endoscopic examination may reveal characteristic granulomas within esophagus or within stomach
Prepatent period of Spirocerca lupi?
6 months
What nematode species are stomach worms of dogs and cats?
Physaloptera species
Where are adult Physaloptera species normally found?
firmly attached to mucosal surface of stomach sucking blood
Diet of Physaloptera species?
blood
tissue derived from host’s gastric mucosa
Clinical signs observed in Physaloptera parasatizim?
vomiting
anorexia
dark, tarry stools
Adult Physaloptera looks?
creamy white
sometimes tightly coiled
1.3 cm to 4.8 cm long
How are adult Physaloptera often recovered?
vomit
Which nematodes are Physaloptera sometimes confused with?
ascarids
roundworms
How to differentiate between Physaloptera and ascarids/roundworms?
break open an adult specimen and if that specimen happens to be female examine the released eggs microscopically.
Eggs of Physaloptera?
small smooth thick shelled embryonated when passed in feces 30um to 34um by 49um to 58um contain a larva when laid
Recovery of Physaloptera eggs?
standard fecal floatation using solution with a specific gravity of more than 1.25
Prepatent period of Physaloptera?
56 to 83 days
What is the nematode kidney worm family?
Dioctophymoidea
What is the “giant kidney worm” of dogs?
Dioctophyma renale
Infection of Dioctophyma renale?
infects right kidney of dogs
gradually ingests renal parenchyma leaving only capsule of kidney
Recovery of Dioctophyma renale eggs?
centrifugation and examination of urine sediment
Dioctophyma renale eggs?
barrel shaped bipolar yellow brown shell has pitted appearance 71um to 84um by 46um to 52um
Prepatent period of Dioctophyma renale?
18 weeks
What is the swine kidney worm?
Stephanurus dentatus
Where is Stephanurus dentatus found?
kidneys
ureters
perirenal tissues of pigs
Stephanurus dentatus eggs?
strongyle type (i.e., oval and thin shelled)
contain 4 to 16 cells
90um to 120um by 43um to 70um
Recovery of Stephanurus dentatus eggs?
from urine by urine sedimentation
Prepatent period of Stephanurus dentatus?
9 to 24 months
What is the nematode family of heartworms?
Filaroidea
What is the name of the canine heartworm?
Dirofilaria immitis
Other animals that Dirofilaria immitis parasitizes?
cats
ferrets
Where can Dirofilaria immitis be found?
right ventricle
pulmonary artery
fine branches of pulmonary artery
Prepatent period of Dirofilaria immitis?
6 months
Life cycle of Dirofilaria immitis?
requires intermediate host to be transmitted from animal to animal
female adults mate in right ventricle and pulmonary artery where they can cause obstruction
male and female adults mate
females produce microfilariae
microfilariae released into host’s bloodstream where they are ingested by feeding mosquitoes
microfilariae grow and molt in mosquito until they reach infective stage
once infective they enter new host next time the mosquito feeds
once in new host, larvae migrate and molt through various body tissues on way to heart
Diagnosis of Dirofilaria immitis?
observation of microfilariae in blood samples with one of several concentration techniques (Modified Knott’s Test)
commercially available immunodiagnostic tests
Filariid often confused with Dirofilaria immits?
Acanthocheilonema (Dipetalonema) reconditum
Unsheathed microfilariae of horses?
Onchocerca cervicalis
Clinical signs of Onchocerca cervicalis?
recurrent dermatitis
periodic ophthalmia
blindness
Intermediate hosts of Onchocerca cervicalis?
Biting flies of genus Culicoides
