Parasitology: Nematodes Flashcards
What are some common routes of infection for helminth parasites?
- ingestion of infective parasite
- ingestion of transport/ intermediate host
- maternal (transmammary/transplacental)
- skin penetration
- blood feeding arthropod vectors
- non-blood feeding arthropod vectors
T/F: Worm populations in animals are aggregated (overdispersed).
true, 70-30 rule
T/F: Infection equals disease
false
Which is worm phylum is the most succesful?
Nematoda
T/F: There are many free-living nematodes.
True
Is it possible to see soil nematodes in fecal samples?
yes. We need to be able to distinguish these from intestinal parasites
What is the nematode body made of? What kind of adaptations are present that allow the nematode to remain in the host?
cuticle, which is flexible, but not metabolically active.
- the cuticle may be modified to form several structures (spines, ridges, secondary sexual structures, etc.)
Describe the internal morphology of nematodes.
“it’s like a tube with two tubes running through it.”
- the body cavity is filled with hemolymph.
- the body wall has a layer of longitudinal muscle
What kind of skeleton do nematodes have? How does it work?
a hydrostatic skeleton. Flexing the muscles of the body changes the pressure of the hemolymph within the body, allowing the nematodes to move “like snakes”
T/F: Nematodes have several sensory structures that allow them to sense their environment.
true
What kinds of neurotransmitters are present in nematodes? which is more common?
- Acetylcholine (most common)
- GABA
T/F: Nematode diet depends on the worm and the location
true
Describe the digestive system of a nematode.
(From anterior to posterior):
- oral opening -> Buccal capsule -> esophagus (aka pharynx) -> intestine -> anus (females) or cloaca (males)
What is one way to differentiate worm species by their digestive system?
look at their esophagus.
Which sex of worm is bigger?
females
Which sex of worm has secondary sexual structures? What is their function?
males
primarily, these structures are used to stabilize the female during mating
Where may the vulva be on a female worm?
anterior, posterior, or in the middle?
Does a female worm strictly lay eggs?
no, some eggs may hatch before she lays them
How many molts will a nematode undergo before it reaches the adult form?
4
What is the L3 rule?
The L3 stage of nematode development is almost ALWAYS the infective stage for a definitive host
Describe the general life cycle of a nematode.
Egg -> L1 -> L2 -> L3 -> L4 -> Adult
What are the six orders of Nematodes covered in this course?
- Strongylida
- Asacardida
- Spirurida
- Enoplida
- Oxyurida
- Rhabditida
Which order of worm can be characterized as large, stout-bodied, and robust?
Order Ascaridida
What are Ascarids generally referred to as?
roundworms
Where do Ascarids generally live?
in the small intestine
What do ascarids feed on?
NOT THE HOST
- they feed on the lumen contents
T/F: Ascarids attach to the host.
false; ascarids do not attach, and must swim constantly to stay within the small intestine
How long do adult ascarids generally live?
a few months in a host
How is an ascarid infection diagnosed?
find eggs in feces
T/F: The ascarid egg is easily susceptible to environmental conditions.
false, its very resistant and hardy
How long does it take an ascarid egg to develop to the infective stage?
2-4 weeks
What are the two genera of Ascarids we are focusing this course?
Parascaris spp.
Toxocara spp.
What is the host of Parascaris spp.?
horses
What is the host of Toxocara spp.
cats and dogs
How long can Parascaris spp. get?
males: up to 30 cm
females: up to 50 cm
Parascaris equorum life cycle
- Eggs passed in manure. In a few weeks, there’s an infective egg.
- Horse comes along and ingests the infective egg, which hatches in the gut.
- Larva penetrates gut wall, gets into hepatic portal system, ends up in the liver, and then carried to the heart, and then lungs.
- Gets coughed up, and swallowed, then larvae end up in small intestine, where they develop into adults
What is hepatotracheal migration
the journey a nematode larvae undertakes when it travels from the GI tract through the liver to the lungs
What is the prepatent period of Ascarids? Why is this important?
- roughly 3 months
- because you won’t see eggs for nearly 3 months, it makes it difficult to diagnose an infection.
Clinical importance of Parascaris.
- common in young horses
- low worm burdens may be subclinical
Clinical signs of Parascaris infection.
- unthriftiness, poor condition
- pot belly
- a very heavy infection can lead to perforation or impaction
- the larvae in the lungs may increase host susceptibility to pathogens (many have permanent effects in severe cases)
- nasal discharge due to larval lung infection
T/F: as horses mature and their immunity develops, patent infections of Parascaris rarely occur.
True
How long do Parascarid eggs require to reach infectivity?
2 weeks
Treatmenta and control of Parascarids.
- nematodicidal antihelmintics
- feces removal and composting (best method)
- wash udders before foaling
T/F: all nematocidal equine anthelmentics are effective against both adults and larvae
false
all are effective against adults, only some against larvae
Why are small animal ascarids (toxocaras spp) called arrowhead worms?
they have anterior cervical alae (makes them look like arrowhead)
What is the species name of the ascarid that infects dogs and other canids?
Toxocara cani
What is the species name of the ascarid that infects cats and other felids?
Toxcara cati
Simplest Toxocara canis infection pattern
- Dog ingests infective eggs.
- Hepatotracheal migration
- Adult worms in small intestine.
- PPP 5 weeks
1st variation of simple Toxocara canis infection pattern
- Dog ingests infective eggs.
- Hepatotracheal migration
- Adult worms in small intestine OR larvae become distributed in blood from lung to tissues, become encysted. (AKA somatic migration)
What is a somatic reservoir of larvae?
a variation of T. canis infection in which the larvae become encysted in the host instead of being coughed up and swallowed.
2nd variation of T. canis
larvae in somatic reservoir activated in late pregnancy (~45 days), and enter pups transplacentally
- pups born with larvae in liver, which then complete the migration to SI and mature.
PPP: 3 weeks
3rd variation of T. canis infection pattern
- another animal consumes infective larvae, which then lay dormant in tissues. Dog eats intemediate host. becomes infected with parasite (which no longer has to undergo any migration)
What are some possible paratenic hosts of T. canis?
- rabbits
- birds
- rodents
- elephants (wut)
What aspect of the dog helps the Toxocara larvae determine which migration system its going to undergo?
the immune status of the dog
When is somatic migration more likely?
more likely in immune dogs and older dogs
Clinical signs of Toxocara canis in puppies
low burdens: no or few signs
moderate to heavy burdens:
- diarrhea/constipation
- colic and pot belly
- vomiting
- unthrifty, poor hair coat
- intestinal obstruction
- pneumonia
Why is it recommended to treat puppies every 2-3 weeks for up to 12 weeks?
the most commonly used drugs affect nematode adults, not the larvae. You need to get the larvae too.
Is there a commercial test available to test for a T. canis somatic reservoir?
nope
How can you control Toxocara canis infection rates?
- remove feces (eggs in environment take 2-4 weeks to become infective, and can survive for long periods of time in ideal conditions)
- wash surfaces w/ 1% bleach solution (doesn’t kill them, but it strips away the sticky outer protein coat on the egg, making them easier to wash away
Why is prevalence lower in the Western US than the Eastern US?
drier environment
Compare and contrast T. cati and T. canis.
T. cati similar in nearly all regards, except:
- transmammary transmission is more important than transplacental
- longer prepatent period
- higher prevalence because the cats are consuming more paratenic hosts
Can humans be paratenic hosts for Toxocara?
yes, but we’re still shitty hosts
Clinical disease syndromes of humans affected by Toxocara migration.
- visceral larva migrans
- ocular larva migrans
Which order of nematode is known as the “bursate nematode?”
strongylida
What is a bursa? which sex of strongylids have it and why?
- a bursa is a “skirt” that male nematodes have. It allows them to stabilize females during mating
Morphology of Strongylids
- a Buccal capsule at anterior end which the worm uses to suck in a plug of mucosa to attach to the host.
- size varies from barely macroscopic to about 15 cm
- pathogenic stage is dependent on the species
T/F: you can distinguish between strongylid eggs only.
false, most members of strongylida produce similar egs
Strongylida egg morphology
- ovular
- thin shell
- contain morula
How many layers of cuticle does an L3 Strongylida have?
2, it kept the previous cuticle
T/F: infective stages of the order Strongylida develop on the egg
false, they develop freely in the environment.
Where do Strongylida larvae develop?
in feces
What is the purpose the Strongylida L3 stage retaining the L2’s cuticle?
its a protective sheath
is it easier to kill a strongylid larvae in the host or the environment
environment
Can strongylid eggs and larvae withstand extreme temperatures or freezing/thawing cycles?
nope
Differentiate between the infective stages of Ascarids and Strongylids
- L3 of ascarids are in eggs
- L3 of Strongylids are free-living
In general, the ____ the temperature, the faster the development of strongylids
higher
T/F: many GI strongylids have a life cycle period in which they enter the gut wall and undergo further development before becoming an adult in the lumen
true.
they will remain in gut wall for a minimum period of time before emerging. Occurs between L3 and L4 stages
What is hypobiosis?
a period of dormancy, in which strongylid development undergoes arrest for a variable period of time in definitive host tissue.
What is one observation in regards to why larvae undergo hypobiosis
seasonal changes. You generally see number of adults peak in summer time and larvae peak in spring/winter time
What affects competence of the host’s immune response?
age and stress
T/F: host immunity develops over time, and is often expressed fully before maturity.
false, it is not fully expressed until maturity
What are the three superfamiles of Order Strongylida, and what are their preferred hosts?
- Trichostrongyloidea: ruminants
- Strongyloidea: horses
- Ancylostomatoidea: small animals
General characteristics of Trichostrongyloidea
- generally small, threadlike worms
- ID based on male bursa and spicules
- small buccal capsule
- GI parasites + 1 lungworm genus
How do you diagnose Trichostrongyloidea infections?
fecals
Prepatent Period of Trichostrongylids
3-4 weeks
T/F: if your ruminant is eating ANY grass, it has trichostrongylids.
true, there’s really nothing you can do about it
How long can the L3 stage survive in environment?
weeks to months, depending on the weather
What do all of the genera of Trichostrongyloidea contribute to?
parasitic gastroenteritis
What are the two most important Trichostrongyloids in the US and what are their preferred species of host?
- Ostertagia: cattle
- Haemonchus: small ruminants
Which part of the cattle stomach will you find Ostertagia?
the abomasum
What is the scientific name of the brown stomach worm of cattle?
Ostertagia ostertagi
Where does the Ostertagia larvae end up after ingestion? How long are they there?
- they enter the gastric glands.
- are in the gastric glands for a minimum of several days
- What is the minimum PPP of Ostertagia?
- What is the maximum PPP of Ostertagia?
- 21 days
- 4-6 months
What is the biggest impact of Ostertagia as larvae emerge from the gastic glands?
- cell dedifferentiation and hyperplasia; the changes lead to nodule formation.
- this dedifferentiation causes the stomach pH to go up. This more basic stomach acid diminishes the strength of the acid barrier of the stomach, leading to digestive issues due to failure to cleave pepsinogen into pepsin.
What is the clinical importance of Ostertagia?
- in Adults and young animals with light infection, there is little to no effect
- in young animals with moderate infection (subclinical), we see anorexia, decreased production (including weight gain)
- In heavy infections (clinical signs), we see:
- anorexia
- diarrhea
- weight loss
- unthriftiness
- hypoproteinemia (bottle jaw)
What is the most important Trichostrongylid in small ruminants of N. America?
Haemonchus contortus
Haemonchus placei can be a problem for which species and in which US region?
- bovine
- Southern US
Where would you find Haemonchus in the ruminant host?
- abomasum
what does Haemonchus feed on?
abomasal blood
How does Haemonchus access the abomasal blood of its host?
it pierces the stomach surface and causes capillary bleeding
T/F: Female Haemonchus are very prolific
true
What is the preferred climate of Haemonchus?
warm weather with high humidity
T/F: Haemonchus population can build rapidly, thus making it an extremely successful parasite
true
What is the PPP of Haemonchus
roughly 2-3 weeks
What is the clinical importance of Haemonchus in heavier infections?
- anemia (not diarrhea)
- failure to gain weight or weight loss
- anorexia
- bottle jaw
- death
What is the general rule for sheep/goats with anemia?
until proven otherwise, it has Haemonchus
When will Haemonchus and Ostertagia undergo hypobiosis?
during the winter
What is type 1 clinical syndrome for Trichostrongylids?
- represents accumulation of worms during the grazing season
- cattle-> usually low mortality, may see only subclinical effects
- small ruminants-> may become more seriously affected as season progresses. Severe anemia can develop in some animals
its more a gradual onset compared to type 2
What is Type 2 clinical syndrome Trichostrongylids?
- a synchronous emergence of arrested larvae in infected host, usually due to seasonal effects
- this can produce severe fatal disease due to severe inflammation or anemia
What are some general characteristics of the superfamily Strongyloidea?
- mostly parasites of the GI tract
- generally have a large buccal capsule
- are plug feeders
Where would you find adults Strongyles?
in the cecum and colon
What are the two types of equine strongyles?
small and large strongyles
What is another name for small strongyles?
Cyathostomins
Where do 3rd stage larvae go in hosts?
large intestine, where they enter the cryps of Lieberkuhn, and penetrate the mucosa
T/F: if a horse grazes, it has Cyathostomins
true
minimum PPP of Cyathostomins
2-3 months
length of adult Cyathostomins
roughly 2 cm
T/F: in the horse mucosa, you can see cyathostomins grossly
true, they appear are little red coils
How long can Cyathostomins remain under hyopobiosis?
up to 2 years
when do cyathostomins arrest/resume development?
- seasonal effects (adults in summer, larvae in winter)
- as adults die, new larvae emerge to replace them
What is the most pathogenic stage of Cyathostomins?
again, the larvae
What are some key clinical signs and symptoms of chronic Cyathostomiasis?
- accumulation of large worm numbers due to
> inflammation and thickening of gut wall
> possible protein losing enteropathy - clinical signs:
> digestive disturbance (intermittent diarrhea +/- colic)
>poor condition, unthriftiness
> hypoproteinemia and anemia
What are some key clinical signs and symptoms of acute Cyathostomiasis?
- when does it occur?
- rapid onset
- Fever
- Diarrhea
> dehydration - edema, hypoproteinemia
– simultaneous emergence of large numbers of arrested larvae
> drug treatment of horses with high worm burdens
> seasonal
how do you diagnose chronic and acute Cyathostomiasis?
Chronic: large numbers of Strongyle eggs in feces
Acute: may not be eggs in manure, but there will be larvae (they’re red)
T/F: adult horses can develop immunity to control cyathostomin populations.
true, just like other parasites
What is the only large strongyle of importance for this class?
Strongylus vulgaris
Where do S. Vulgaris adults reside?
large intestine
what is the PPP of S. Vulgaris?
6 months
Where does the infective S. Vulgaris larvae go after infection? When does S. Vulgaris return to large intestine after infection?
- it molts, and the L4 migrates through the arteries to reach the junction of cranial mesenteric artery and aorta, stimulating thrombus development
How long after infection does the Larvae return to the large intestine?
about 4 months
Which stage of the S. vulgaris is the most concerning? Why
the larval stage, L4
When it is in the junction of the cranial mesenteric artery and the aorta, it leads to thrombus formation, which can impair or block blood flow,
How does thrombus formation occur due to S. vulgaris?
What are the dangers of this thrombus formation?
The L4 larvae damage the blood vessels, causing a verminous arteritis.
- The thrombus can reduce blood flood and interfere with nerve transmission.
- it could also break off, and block distal bloodflow, leading to necrosis of portions of bowel in severe cases
Is it possible to treat verminous arteritis
to a degree yes, the lesions regress after the worms leave and with treatment
Strongylus vulgaris used to be the primary cause of what disease in horses?
colic
What is the common name used for the Superfamily Ancylostomatoidea?
hookworms
What do ancylostomatoids feed on?
blood, not tissue
General morphology of acylostomatidae
- typically 1-2 cm in length
- large buccal capsule
- teeth or cutting plates
What are some common canine hookworms?
- Ancylstoma caninum*** (most important in this region)
- A. braziliense (seen in southeastern coastal US and south)
- Uncinaria stenocephala (cold climate hookwarm (canada))
Differentiate between canine strongylids and cattle/horse strongylids.
- canine hooks like being on the soil, while horse and cow strongylids like grass
- vector of penetration:
> canine strongylids: skin penetration
> cattle and horse strongylids: ingestion
Where is development for Canine acylostomatidae best?
in moist, shaded, slightly sandy loam (think dog runs)
What are the routes of transmission for Ancylostoma caninum?
- skin penetration
- transmammary
- ingestion of larvae
- (minor) transplacental
- (minor) transport hosts
Once in the to tissues, where will hookworm larvae be carried to?
The lungs
What is the primary form of vertical hookworm transmission
transmammary
Once a hookworm larvae enters the dog, it can _____ or _____
- become an adult in the small intestine
- undergo hypobiosis in the gut or tissues
Where will adult hookworms develop?
- without arrest from mom in the milk
- with or without a period of arrest following infection from other routes
Is Ancylostoma more or less commonly found as an adult infection than Toxocara
more common
T/F: Low hookworm numbers generally appear asymptomatic.
true
What are some clinical signs of hookworm infection?
- diarrhea-> melena
- anemia, hypoproteinemia
- unthriftiness
- skin lesions
What are some susceptible hosts that you would predominantly see these symptoms in?
puppies, immunocompromised digs, or if the exposure were heavy
When does immunity develop against hookworms?
as always, after exposure
What is melena?
oxidized blood in stool, it looks dark and tarry
Diagnosis of ancylostoma caninum
fecal example (only common strongylid egg in small animal samples)
T/F: hookworm PPP is in independent of infection route
false, it is entirely dependent on infection route
What is the minimum PPP of a transmammary infection?
2 weeks
Treatment and Control of Ancylostoma caninum
- pick up the Poop!
- most canine anthelmintics are effective against adults, but there’s no good treatment for arrested larvae
What is the scientific name of the feline hookworm?
Ancylostoma tubaeformae
T/F: Ancylostoma tubaeformae has a higher prevalence than Ancylostoma caninum
false
T/F: A. tubaeformae has a high perinatal transmission rate
false
T/F: A. tubaeformae is not as pathogenic as A. caninum
true
T/F: A dog who eats cat feces will develop an A. tubaeformae infection.
false, the larvae need time to develop
Which species of canine hookworms is a”vigorous skin penetrator?”
A. braziliense
What are cutaneous larva migrans?
serpiginous tracks produced by A. brasiliense larvae migrating in the skin of people
T/F: A. braziliense infections are more likely to occur in those who are most frequently in lots of soil
true
What is the difference in strongylid tolerance between large and small animals?
Small animals have a zero tolerance policy regarding parasites. If its peresent we try to get rid of it.
Large animals have threshold that they try to stay under because it is all but impossible to eliminate the parasites because of all the grazing on grass
What is the goal of GI worm control in sustainable systems?
- to keep the worms at a level that doesn’t have detrimental health effects
What are the three tools to control parasites in grazing animals? What is the acronym?
RID
R- reduce parasite exposure on pasture (rotate field portions, etc.)
I- immunity level of host (keep them healthy, and keep young livestock off of recently used pasture)
D- drugs. Use anthelmintics where necessary to prevent infection
Which animals are most vulnarable to infection?
the young, periparturient, stressed, and high-performance animals
How can you reduce exposure to strongylid larvae?
- don’t let them on pasture
- reduce stocking density
- pasture rotation and rest
- alternate/mix grazing (change the grazing species, since the Strongylids are host-species specific)
- remove manure (works best in horses and camellids)
- respect host behavior (use their habits to your advantage)
What is a “ring of repugnance?”
the perimeter that surrounds a fecal mass that animals will not eat near
How do you get rid of a ring of repugnance?
harrow the ground after animals rotate of that part of pasture
What is the benefit of goats being browsers?
They spend less time grazing because they’re chompin down on plants above the ground and away from parasites. This prevents them from ingesting infective larvae
How does camelids defecating in community piles help reduce parasite transmission?
easier to clean up an isolated area of dung
T/F: there is a nematode-eating manure fungus.
true
Which animals should you cull or select for your herd?
- cull highly susceptible animals
- select highly resistant animals
How can you determine whether or not to deworm an animal?
- for horses, you can perform an egg count. If it goes over the threshold, deworm.
- use an anemia assessment tool. Depending on the level of anemia, it may be required/recommended.
Which animals will worm problems appear first?
- animals with “temporary” low immunity (young, lactating, or stressed animals)
- animals with inherited high susceptibility
Which order of nematodes has a common characteristic of needing an arthropod intermediate host
Order Spirurida
What do we generally call members of the superfamily Filaroidea?
filarids, filaroids
What kind of tissue do filarids parasitize?
- connective tissue
- blood vessels, lymphatics, etc.
- adults feed on lymph or plasma
Physical description of filarids
long slender worms, incredibly small
T/F: Females produce microfilariae, a stage between the egg and L1 stages
true
What is the definitive host of Dirofilaria immitis?
dogs and wild canids
- ferrets
What are some abnormal hosts of Dirofilaria immitis?
cats, humans, and other mammals
Where would you primarily find D. immitis in the host?
the pulmonary arteries primarily
What is the common name of Dinofilaria immitis
heartworms
What is the intermediate host of D. immitis
mosquitoes
T/F: heartworms are considered endemic in the US and worldwide
true
What is the prepatent period of D. immitis
6 months
How long can adult D. immitis live?
nearly 5 years
T/F: your dog can get heartworms from a blood transfusion from another dog.
false
The microfilariae produced by the adult female
Where does the microfilariae mature?
in the mosquito
How long can microfilariae circulate in peripheral blood?
1-2 years
How early do microfilariae appear in blood?
as early as six months post infection
How are infective D. immitis larvae transmitted to the host? Which stage?
by mosquito bites
L3!!!!!
Where does the L3 stage of D. immitis mature? How long does this take?
in the subcutaneous tissue of the host at the bite wound. Takes 1-3 days to mature
How long does it take an L4 to mature to an adolescent stage?
50-70 days
How long does it take a sexually immature worm to migrate to the heart and lungs from date of infection?
as early as 70 days
What is the biggest issue of disease in regards to heartworms?
The host reaction to the parasite
Villous lesions are formed from _____
endothelial hyperplasia
What is the BASIC pathgenesis of heartworm disease?
- to start, there is the physical barrier of the heartworm obstructing blood flow.
- a complex reaction occurs where the vessel wall comes into contact with the filarid. leads to villous lesions (villous endarteritis) forms due to endothelial hyperplasia. So now in addition to worm presence, the blood vessel wall is also messed up.
- can lead to progressive fibrosis in the vessel, and also has the potential for producing a thromboemboli
T/F: vessel damage is proportion to number of filarids present
true
T/F: more dogs die of heartworm than with heartworm.
false, more dogs die with heartworm than of heartworm
What happens as heartworm disease gets more severe?
- the heart now has to work harder to get past the obstruction.
- reduced cardiac output and compensatory right heart disease
- right heart enlargement and failure
Clinical signs of D. immitis
- low to mild
- mild to moderate
- moderate to severe
low to mild: Asymptomatic
mild to moderate:
- chronic cough
- dyspnea
- Decreased exercise tolerance
Moderate to high:
- syncope (fainting)
- hemoptysis (coughing blood)
- congestive heart failure
- ascites
What are some uncommon clinical signs of D. immitis infection?
- vena caval synodrome: occurs with very heavy infection. worms move back into heart, leading to severe passive congestion of the liver. can cause acute collapse
- abnormal migration leads to unusual problems. ex: a heartworm on a testicle.
Prevalence of D. immitis in US.
considered endemic in 48 states, but highest prevalence is in Mississippi and Eastern coast
T/F: coyotes are great reservoirs for heartworm in southern CA
true
How can you diagnose a D. immitis infection?
- antigen tests (you test for the antigen of the parasite, not the parasite)
Which sex of D. immitis generates the antigen primarily tested for in diagnosis?
the females
What are some limitations of antigenic D. immitis testing?
- the antigen chosen needs to not be present on other parasites, or it could cause a false positive
What tests can check for microfilariae?
- peripheral blood sample checks
- Knott’s test is best (its a concentration technique)
How do you treat heartworm disease?
- Prevention is much better than treatment
- may require surgery
T/F: by getting rid of the symbiotic bateria Wolbachia, can interfere with heartworm reproduction
true
Which drug is most commonly used to treat heartworm infections
doxycycline
T/F: you can treat a cat with heartworms.
false, what kills the worm kills the cat
Is heartworm disease likely to develop in cats?
no, most worms die soon after infection
What are some clinical signs of HW infection in cats?
(most of these are in response to dying worms or abnormal migration)
- respiratory signs
- vomiting
- exercise tolerance
- sudden death
- signs associated with migration to another part of the body
T/F: ferrets are immune to HW disease
false, they can get typical heartworm disease
What should you assume if you “see a long thin worm in necropsy that isn’t in the GI tract?”
its probably a filarial worm
General physical morphology of other species of Spirurida.
Eggs: elliptical, smooth, thick shell wall containing a coiled larva
Adults are small to medium in size, but not threadlike
- these require an intermediate arthropod host
Where do Habronema spp. live?
nodules of equine stomach
What are the intermediate hosts of Habronema spp.?
stable and house flies
- Which spirurid causes “summer sore?”
- what is “summer sore?”
- Can larvae continue development?
- what can summer sore be mistaken for?
- habronema spp. when it gets deposited in mucocutaneous junction wounds.
- A persistent cutaneous granuloma
- larvae cannot continue development
- can be mistaken for exuberant granulation tissue, neoplasia
What worms are associated with the Order Enoplida?
Trichuris, capillarids,
What are the characteristic factors of enoplida eggs?
- egg has to polar plugs, slightly elliptical in appearance
Which is the scientific name for whipworms in dogs
Trichuris vulpis
Where are Trichuris worms typically located in the host?
in the large intestine
physical morphology of Trichuris
- a whip-shaped body, the narrower anterior end is entwined within a layer of epithelial cells.
- What kind of life cycle do Trichuris spp. have?
- Where are eggs passed?
- where do infective larvae develop? how long does it take?
- direct life cycle
- in feces
- develop in the egg; takes at least 2 weeks
T/F: Trichuris eggs are highly resistant to environmental condtions.
true
What is the PPP of Trichuris vulpis?
3 months
Clinical symptoms of clinical T. vulpis infection
- smelly diarrhea
- vomiting
- anemia
T/F: Trichuris infections can occur in dogs of all ages
true
How wold you treat a T. vuplis infection?
- remove feces to prevent further infection
- treat with meds, then treat again in three weeks
What other species can you find Trichuris spp. in?
- pigs
- ruminants
- cats (only in Fl. and other countries)
- people (have their own species)
T/F: capillarid eggs look similar to whipworm eggs
true
Where would you find a Trichinella spp in the host?
what is the geographical distribution of Trichinella?
adult worms are in the small intestine of warm blooded animals
worldwide distribution
Why should you never eat undercooked pork?
you don’t want a Trichinella infection caused by encysted Trichinella larvae
How are pigs infected with Trichinella?
they eat garbage, rats, and each other
Where do you most commonly see Trichinella cases?
- in wildlife that consume pigs (pigs, bears, seals, etc.)
What are some symptoms and the causes of Trichinosis?
- enteritis caused by adult Trichinella
- migrating larvae cause inflammation
- myalgia, fever
- Respiratory and cardiac failure in heavy infections
What worm is associated with Order Oxyurida?
pinworms
Where would you see pinworm adults in the host species?
- large intestine
What species will you primarily find pinworms in? what other species can be infected?
mostly seen in horses.
other species include:
- horses, rodents, ruminants, reptiles, people
T/F: Pinworms are very pathogenic
false
Describe a pinworm egg.
one polar plug, often flattened appearance on one side
What is the scientific name of the equine pinworm
Oxyuris equi
Geographical distribution of Oxyuris equi
worldwide
How are hosts infeted with O. equi?
- ingestion of eggs
Where do fertilized females deposit their eggs?
The migrate from large intestine and rectum onto skin, then glue eggs to hairs in perianal area
How do the O. equi eggs end up in the environment?
- the glue and the worm movement are very irritating, so the horse rubs the itchy area, and the eggs fall off and into the environment
How can you diagnose O. equi?
“scotch tape test;” apply a piece of scotch tape to rear, then examine it under a microscope to find eggs
How do you treat O. equi infections?
- most modern nematocides work; also wash blankets, as eggs might have gotten onto them
T/F: Human pinworms are caused by animals
False; it is strictly human to human transmission
What animal parasite genus is associated with the Order Rhabditida?
Strongyloides
How are hosts infected with Strongyloides?
- skin penetration, transmammary transmission
Eggs are commonly seen in young ____, less often in ____ and ____, and are uncommon in_____.
- ruminants
- foals
- pigs
- dogs
What is are Strongylid eggs generally mistaken for?
Strongylids
