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249 Cards in this Set

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true or false: worms are usually highly host specific and can only live in its specific host?
False

Worms are highly adapted to the DEFINITIVE host, but in many cases can also have an intermediate host.
true or false: worms do not undergo asexual multiplication in the definitve host?
false.
Most worms multiply sexually. Some are parthenogenic.
what age group is most at risk for worm infection?
young
why, in many cases, do we accept worm control versus complete eradication?
because they are very hard to eradicate completely and small numbers are usually not very pathogenic.
true or false: an individual animal's susceptibility to a high worm burden is highly dependent on external conditions such as nutrition and exposure to other infections agents?
False. An individual's susceptibility to a large worm burden is by-and-large a heritable trait.
what type of immune response is typical of a worm infection?
Th-2, eosinophilic (recall: IgE)
compare the treatment objectives for helminth infection in small animals versus food animals versus horses.
Small animal:
- Elimination
- Best products from vet
- Cost less important

Food animals:
- Control
- Product usually not from veterinarian
- Cost very important

Horses:
- Aspects of both
which organization(s) regulate anthelmintics?
FDA
What are the NINE types of anthelmintics that we are studying in this course?
1. Benzimidazoles
2. Imidazothiazoles (levamisole)
3. Tetrahydropyrimidines (pyrantel, morantel)
4. Macrolides or macrocyclic lactones (antiparasitics not antibacterials)
5. Isoquinolones (praziquantel and epsiprantel)
6. Cyclic depsipeptide (emodepside)
7. Benzenesulfonamide (clorsulon)
8. Amino acetonitriles (monepantel)—not in US YET
9. Spiroindole (derquantel)—not in US
name some benzimidazoles and their mode of action
albendazole, fenbendazole, febantel, oxibendazole

affects tubulin
name some macrocyclic lactones and their mode of action
Ivermectin, doramectin, eprinomectin, selamectin,
moxidectin, milbemycin

affects glutamate gated chloride channels
name an imidazoithiazole and its mode of action
levamisole

Acetylcholine agonist
name some tetrahydropyrimidines and their mode of action
pyrantel, morantel

Acetylcholine agonist
name some isoquinolones and their mode of action
praziquantel, epsiprantel

affects cell membrane permeability
name a cyclic depsipeptide and its mode of action
emodepside

affects lactrophilin receptor
name a benzenesulfonamide
clorsulon
name an aminoacetonitrile and its mode of action
monepantel

affects acetylcholine receptor
name a spiroindole and its mode of action
derquantel

selective cholinergic agonist
resistance to one member of a group of anthelmintics, resistant to all in that group
side resistance
resistance to one group of anthelmintics conferring resistance to another group of anthelmintics
cross resistance
what word MUST you use in an essay regarding pesticide resistance?
refugia
what benzimidazole is approved for use in the most species?
fenbendazole
comment on the administration of benzamidazoles
- Need to stay around for awhile to work (multiple doses in non-ruminants)
- fenbendazole needs to be given with food in small animals
- Rumen acts as reservoir in ruminants
which benzamidazole is likely to be given to dairy cattle to manage a routine worm infestation and why?
fenbendazole

no milk withdrawal time. Others are not approved for lactation or have long withdrawal times.
what is the spectrum of action of benzimidazoles?
- nematodes: all life stages
- albendazole and fenbendazole also have activity against tapeworms and flukes
imidazothiazole and tetrahydropyrimidines
- examples (species)
- spectrum of action
- mode of action
- administration
- withdrawal time
- safety
- levamisole (ruminant, pig); pyrantel (horse, dog, cat, pig); morantel (bovine, Goats)
- adult nematodes
- cholinergic agonists: depolarizing of neuromuscular junctions
- oral, injection
- meat, days; morantel has no withdrawal; the rest not for dairy
- good; levamisole has most problems
macrolides
- examples
- spectrum of action
- mode of action
- administration
- withdrawal time
- safety
- avermectins: ivermectin, doramectin, eprinomectin, selamectin; milbemycins: milbemycin, moxidectin
- nematode adults and larvae; arthropods
- binds to glutamate gated chloride channels: hyperpolarization of nn. and mm.
- oral, SubQ, topical, sustained release (moxidectin)
- withdrawal zero to weeks for meat; eprinomectin & moxidectin have no milk withdrawal; others not for dairy
- safe. exceptions: ivermectin in collie breeds and moxidectin in horses; eco: ivermectin can delay fecal processing but low with interval dosing
isoquinolones
- examples
- spectrum of action
- mode of action
- administration
- safety
- praziquantel, epsiprantel
- tapeworms and some flukes
- tetanic contraction of muscles, probably from change of permeability of tegument to calcium
- oral
- safe
cyclic depsipeptidases
- examples (species)
- spectrum of action
- mode of action
- safety
- emodepside (cats only)
- nematodes
- binds to presynaptic lactrophilin receptor causing flaccid paralysis
- safe
benzene sufonamides
- examples (species)
- spectrum of action
- administration
- withdrawal time
- clorsulon (bovine); often combined with ivermectin
- bovine liver fluke
- oral and injectible
- not for dairy
piperazine
- species
- spectrum of action
- mode of action
- pigs, birds, horses
- pigs and birds: ascarid nematodes; horses: small strongyles (not common)
- anticholinergic: paralyze worms
amino acetonitriles
- example (species)
- spectrum of action
- mode of action
- moneprantel (large animals) (not yet available in US)
- nematodes (especially those resistant to other anthelmintics)
- AcCh receptor on muscle; hypercontraction of body and spasmodic contraction of pharynx
spiroindoles
- example
- spectrum of action
- mode of action
- derquantel (in combination with ivermectin)
- nematodes
- selective cholinergic anatagonist in mucsle; flaccid paralysis
benzimidazoles
- examples (species)
- spectrum of action
- mode of action
- administration
- withdrawal time
- safety
- fenbendazole (bovine, dog, horse, goat, pig); albendazole (bovine, sheep); oxibendazole (horse); oxfendazole (bovine); febantel (dog; cat product no longer available)
- nematodes; adult, larvacidal over longer periods, ovidical; tapeworms and flukes (albendazole, fenbendazole)
- prevent microtubule assembly; secondary effect on some enzymes
- oral
- meat withdrawal days to weeks (albendazole longest at 27 d); milk: fenbendazole has no withdrawal time, but others not for dairy
the "skin" of a nematode is called what?
cuticle
what is the basic anatomy of a nematode?
- cuticle surronded by hypodermis and longitudinal muscles
- pseudocoel with hemolymph (hydrostatic skeleton)
- gut tube and sex organs seen in cross-section
describe the structure, organs, and neurotransmitters of the nematode nervous system
- ganglia with longitudinal nerve cords
- papillae as tactile receptors
- acetylcholine and GABA
describe the nematode digestive system
- food depends on worm and location
- oral opening
- buccal capsule
- pharynx (important in taxonomy and ID)
- intestine
- anus in female; cloaca in male
describe nematode reproduction and sexual dimorphism
- most dioecius (separate sexes)
- some are parthenogenic (diploid eggs that don't need fertilization to become an embryo)
- females usually larger
- males have spicules (used in ID)
- females release eggs or larvae
how many molts does a nematode go through to become an adult?
four: L1-L5
note, no molt for L5-->adult
name four superfamilies order strongylida
Trichostrongyloidea
Strongyloidea
Ancylostomatoidea
Metastrongyloidea
name three genuses of order ascaridida
1. Toxocara
2. Parascaris
3. Ascara
- Baylisascaris (racoon)
- Ascarida (avian)
- Heterakis (avian)
Name 7 genuses of Trichostrongyloidea
Oestertagia, Haemonchus, Trichostrongylus, Cooperia, Nematodirus, Dictocaulus, Hyostrongylus
name four clinically important types of Strongyloidea
Equine Strongyles, Cyathostomes, Strongylus (vulgaris), Oesophagostomum
comment on the passage, development, and morphology of the ascarid egg
- passed in fresh feces as a single cell
- larva develops up to L3 in the egg
- take 2-4 weeks
- the only worms with a thick shell and a single egg inside
pig ascarid genus and species, common name
Ascaris suum
roundworm
Ascaris suum
- location of adult in the host
- how long before egg becomes infective?
- prepatent period
pig ascarid (roundworm)
- small intestine
- at least 3 weeks. (egg can be viable for years)
- 6-8 weeks
Ascaris suum
life cycle
pig ascarid (roundworm)
- eggs-->L3 in the environment
- L3 is the infective larva in the egg
- L3 hatches in the intestine and burrows through intestinal wall
- hepatic portal to liver
- burrow thorugh liver to bloodstream
- bloodstrream to lungs
- coughed up, swallowed
- become adults in small intestine
- eggs shed in fresh feces
- prepatent period is 6-8 weeks
Ascaris suum Dx
pig ascarid (roundworm)
Fecal exam
Ascaris suum clinical importance
pig ascarid (roundworm)
- inflammation of liver ("milk spots")
- liver condemnation
- lesions regress after 4-6 weeks
- dyspnea
- secondary lung infection
- low productivity
- (rarely) block bile ducts, obstruct/perforate BVs
who is most at risk of developing disease from Ascaris suum infection and why?
pig ascarid (roundworm)
- young pigs that are heavily infected.
- immunity develops during 1st infection
Ascaris suum control and treatment, including drugs
pig ascarid (roundworm)
- remove feces
- kill eggs (very difficult: need flame, steam, lye)
- treat prefarrowing sows
- BZDs, pyrantel, macrolides, lavamisole, dichlovos
Ascaris suum zoonosis
- respiratory disease in calves
- can infect humans
human ascarid Genus and species
Ascaris lumbricoides
ascarid of horses and other equids Genus and species
Parascaris equorum
Parascaris equorum
- prepatent period
- most susceptible animals
- clinical signs
(horse ascarid)
- PPP 11-14 weeks
- foals and young horses
LARVAE
- damage lungs through mechanical damage and inflammation
- 2ndary infections
- nasal discharge
- unthrifty
- may be permanent in severe cases

ADULTS
- low levels, no signs
- unthrifty
- pot belly
- perforation or impaction in very heavy infection
Parascaris equorum Dx and Tx
horse ascarid
- eggs in fecal float
- numbers used to evaluate drug efficacy
- all nematocidal anthelmintic effective
- macrolides and FBZ for 5 days is larvacidal
Parascaris equorum environmental and drug control
horse ascarid
- remove feces
- clean stalls with 5% phenol solution
- wash udders before foaling
- treat at 8 weeks of age and monthly to every six months
how long do Parascaris equorum eggs require to be in the environment before they are infective?
2 weeks
what is the genus of the small mammal ascarids?
Toxocara
(roundworms)
What is the prepatent period of Toxocara canis? How long do eggs take to become infective?
(roundworms)
PPP is 5 weeks and 3 weeks after birth in congenital infections
eggs infective after 3-4 weeks
how can Toxacara canis adults become dormant in the host and what predisposes the host to this condition?
(roundworms)
- adults can migrate to tissues and become dormant in granulomas
- older hosts with immunity have a higher prevalence
Why is the Toxocara canis prepatent period only 3 months in newborns, but 5 months in adults?
(roundworm)
Because the somatic reservoirs activate 40-45 days after pregnancy, migrate transplacentally, and infect the liver of the developing fetus.
If puppies are infected with Toxocara canis at birth, why is the mother at risk?
(roundworm)
The dam can acquire infection through coprophagia because she needs to lick her pups to stimulate defecation.
What are three common transport hosts of Toxocara canis
(roundworm)
Rodents, birds, earthworms
Comment on the clinical signs with respect to worm burden in puppies infected with Toxocara canis
(roundworm)
Light infections - no clinical signs
Moderate to heavy:
- diarrhea and constipation
- colic and pot belly
- vomiting
- unthrifty, poor hair coat
- death with heavy infection
what is the preferred drug for treatment of Toxocara canis in puppies and why
(roundworm)
pyrantel because it is easy to administer and usually requires only one dose
what drugs are effective in the treatment of Toxocara canis infection?
(roundworm)
pyrantel, macrolides, fenbendazole, febantel
Comment on the treatment of pregnant dams for Toxocara canis
(roundworm)
It is off-label use
- fenbendazole or macrolides
Toxocara canis Tx and control
(roundworm)
- Treat lactating dams
- Off-label treatment of pregnant dams
- treat other dogs as needed or routinely
- remove feces
- wash surfaces with 1% bleach (doen't kill eggs, but removes sticky surface)
low long do Toxocara canis eggs take to develop in the environment to become infective?
(roundworms)
3-4 weeks
Genus and species of cat roundworm
Toxocara cati
What are ways that cats can become infected with Toxocara cati
(roundworms)
- direct from infective eggs
- transport hosts (e.g. rodents)
- transmammary (minor)
- NOT transplacental
How is Toxocara cati treated and controlled?
(roundworm)
same as Toxocara canis
comment on the zoonosis of Toxocara canis and T. cati
can be transmitted to humans:
- visceral larva migrans
- ocular larva migrans
what are the two syndromes of human toxocariasis?
(roundworms)
- Visceral larva migrans (VLM)
- Ocular larval migrans (OLM)
what are the symptoms of visceral larval migrans syndrome in human toxocariasis? Risk factors?
- eosinophilia, fever
- hepatomegaly
- respiratory signs
- encephalitis (rare)

Risk factors: age, pica
what are the symptoms of ocular larval migrans syndrome in human toxocariasis?
- endophthalmitis
- chorioretinitis
- badness
what are the major socioeconomic risk factors for human toxocariosis?
- soil related occupation
- non-U.S. birth
- poverty
- educational level
- lead level
- household crowding

take-home message: poor people
what is the role of contact with infected dogs in human toxocariasis?
probably not great
what is another less prevalent genus of roundworm that infects dogs and cats besides Toxocara?
Toxascaris
raccoon ascarid
- Genus and species
- clinical importance and zoonosis
- control
- Baylisascaris procyonis
- causes visceral larval migrans in many species
- severe CNS signs with fatailities in human puppies
- rarely patent in dogs
- treat captive raccoons
Name two avian ascarid genuses, their location in the host, and clinical signs
1. Ascarida
2. Heterakis - transport host of blackhead in turkeys

- weight loss
- ruffled feathers
- depressed
what is the common Stongylida superfamily in ruminants?
Trichostrongyloidea
what is the common Stongylida superfamily in Horses
Strongyloidea
what is the common Stongylida superfamily in small animals and humans?
Ancylstomatoidea
which superfamily of Strongylida does not have direct life cycles?
Metastrongyloidea
what does a stongylid egg look like?
oval, thin shell, ball of cells inside
what is the life cycle of most strongylids?
- eggs laid in fresh feces
- L1 develops inside egg
- L2 and L3 develop outside egg in the fecal mass and distributed into the environment by rain and other mechanical forces
- L3 is ingested by host
- does not migrate like ascarids
- L3 - L5, adult in host
what factors favor the development of strongylid eggs from egg to L3? What factor favor the survival of L3?
Development:
- warm temp (> 50 ºF)
- moisture

Survival:
- cool temp
- moisture
Explain hypobiosis in strongylids
- L3 or L4 in the definitive host may become dormant after infection
- may be due to environmental factors or immunity
- might be a part of the life cycle to adapt to seasonal climate changes
what is the "HOT complex?"
common strongylids of large animals:

- Haemonchus
- Ostertagia (Teladorsagia)
- Trichostrongylus
what is the most important helminth that infects cattle?
Ostertagia ostertagi (strongylid)
brown stomach worm of cattle Genus and species
Ostertagia ostertagi (strongylid)
brown stromach worm common in small ruminants
Ostertagia circumcincta
What is the life cycle, including minimum and maximum prepatent periods, for Ostertagia spp.?
(strongylid in ruminants)
- ruminant ingests L3 from pasture
- larvae enter gastric glands for a minimum of several days
- emerge into lumen and become adults
- prepatent period of 21 days (max 4-6 months)
what are clinical signs of Ostertagia infection?
(strongylid in ruminants)
- damage the abomasal wall
- cell dedifferentiation and hyperplasia
- nodules in gastric glands
- loss of normal gastric gland function

- Anorexia with moderate infection
- Heavy infection: diarrhea, anorexia, weight loss, unthriftiness, hypoproteinemia (bottle jaw)
what are the two syndromes of Ostertagia infection and what causes each?
(strongylid in ruminants)
- Type 1: accumulation of worms past pathogenic threshold
- Type 2: large amount of worms emerging from hypobiosis
Type 1 Ostertagiasis:
- incidence risk
- time of year
- mortality risk
- clinical signs
(strongylid in ruminants)
- many susceptible animals affected
- mid to late grazing season
- few fatalities
- diarrhea, weight loss
Type 2 Ostertagiasis:
- incidence risk
- time of year
- mortality risk
- clinical signs
(strongylid in ruminants)
- few animals affected
- before major transmission season (when arrested larvae emerge)
- high mortality
- acute, severe diarrhea and dehydration
what are risk factors for disease resulting from Ostertagia infection?
(ruminant strongyles)

Stressed animals:
- nutritional
- diseased
- periparturient
- other stresses (e.g. car broke down on I-81)
what is the most important small ruminant strongylid in the world?
Haemonchus contortus
(strongylid)
If upon necropsy, you find worms in the abomasum of a cow, what worm is it likely to be?
Haemonchus placei
(strongylid)
If a sheep or goat has anemia, what infection should be on your rule-out list?
Haemonchus infection
(strongylid)
Haemonchus life cycle:
- prepatent period
- effect of weather
(strongylid of small ruminats and cattle)
- 2-3 week PPP
- likes humid, warm weather
- hypobiosis in cold weather
what strongylid species can can infect the stomach/abomasum of horses, pigs, and cattle?
Trichostrongylus axei
where in the host do most species of Trichostrongylus spp. infect? Clinical signs?
- small intestine
- diarrhea in heavy infection
what strongylid species stays in the egg until L3?
Nematodirus spp.
(a trichostrongylid)
lung worm Genus and type of worm
Dictyocaulus spp.
trichostrongylid
trichostronglyid of the pig intestine
Hyostrongylus
equine strongyles are of what order and superfamily?
Order Strongylida
Superfamily Strongyloidea
what are the two subfamilies of equine strongyles and their common names?
- Strongylinae: large strongyles
- Cyathostominae: small strongyles
where do equine strongyles typically reside in the host?
cecum and large intestine
what is the life cycle of small strongyles (Cyathostomes), including the prepatent period?
- L3 go to cecum, colon when ingested
- enter crypts of Liberkuhn and penetrate mucosa
- develop or become hypobiotic
- return to lumen to mature (up to 2 cm long)
- without hypobiosis, PPP is about 6-14 weeks
Small strongyles--Cyathostomes clinical importance, including syndromes, signs, Dx
- low numbers, no apparent effect
- larvae cause problems, not adults

Acute (Type 2) cyathostomiasis:
- rapid onset, fever
- diarrhea
- edema, hypoproteinemia
- Dx: difficult; may see larvae in feces, but often negative fecal
- hard to treat if there are large numbers of worms
- double dose of fenbendazole for 5 days
- moxidectin
- not fully effective against hypobiotic larvae

Chronic (Type 1) cyathostomiasis:
- accumulation of large numbers in gut wall
- inflammation and thickening of gut wall
- colic
- intermittent diarrhea
- unthriftiness
- Dx: high fecal egg count
what is unique about Strongylus vulgaris compared to other large stongyles? Pathogenesis and clinical signs?
- L4 circulates in the blood stream
- can cause embolism
- can damage vessel walls
- thrombembolism
- bowel necrosis
- colic
what is the prepatent period for Strongylus vulgaris?
6 months; 2 dewomings per year is enough
what worm causes "pimply gut" in the large intestine of cattle, small ruminants, and pigs?
Oesophagostomum spp
(strongyloidea)
what is the best management practice for GI worm control in sustainable systems?
- don't eradicate worms
- keep worms at a low level
- this keeps refugia up and resistance low

Tools:

RID:
- Reduce parasite exposure on pasture
- Immunity of the host
- Drugs
what are some ways to reduce stongylid parasite exposure on pasture?
- reserve pasture with fewest larvae for the most vulnerable animals
- reduce stocking density
- remove manure
- after grazing, harvest regrowth for hay
- pasture rest
- MIXED GRAZING
how can you use the immunity of the host to control stongyles?
- selective deworming - only use it on animals that need it the most
- culling (remember that worm burden is heritable)
- select resistant animals
- good nutrition
what anthelminthics are used most commonly in cattle and small ruminants?
- macrolides
- benzimidazoles
- levamisole
what anthelminthics are used most commonly in horses?
- macrolides
- pyrantel
- benzimidazoles
what superfamily and family do hookworms belong to and what are their hosts?
Superfamily Ancylostomatoidea
Family Ancylstomatidae
hosts: small ruminants, ruminants, humans, other vertebrates
Ancylostomatoidea morphology:
- mouthparts
- length
- egg
- large buccal capsule with teeth or cutting plates for bloodsucking
- 1-2 cm in length
- typical strongylid egg
name three species of canine hookworms
1. Ancylostoma canium***
2. A. braziliense
3. Uncinaria stenocephalia
name three species of feline hookworms
1. Ancylostoma tubaeformae
2. A. braziliense
3. Uncinaria stenocephalia
Ancylostoma canium:
- site of infection in host
- time from egg-->L3
- four routes of transmission
(canine hookworm)
- small intestine (jejunum)
- 2-7 days depending on temperature

Routes of transmission:
1. Skin penetration
2. ingestion of larvae
3. Ingestion of transport host
4. Transmammary
Ancylostoma canium name three fates of the larvae in the dog.
(canine hookworm)
1. Become adult in small intestine
2. Enter intestinal wall and later emerge
3. join somatic reservoir
Who is at most risk for Ancylostoma canium infection and what are the clinical signs?
(canine hookworm)
- most often seen in puppies
- low worm numbers asymptomatic
- diarrhea-melena
- anemia, hypoproteinemia
- unthriftiness
- skin lesions
comment on Ancylostoma canium immunity
(canine hookworm)
- most exposed adults will develop immunity
- there will be no disease unless immunocompromised, overwhelming parasite numbers, or malnourished
Ancylostoma canium Dx and Tx
(canine hookworm)
Dx: fecal float. It is the only common strongylid egg in small animals
Tx: canine anthelminthics except for piperazine. Repeat in 2-3 weeks.
Ancylostoma canium prepatent period
(canine hookworm)
about 2 weeks after transmammary infection
what is Ancylostoma tubaeformae: host and common name?
feline hookworm
what is the importance of Ancylostoma braziliense?
- hosts
- how to they get into host
- diseases
- dogs, cats, and humans
- penetrate skin
- cutaneous larva migrans
hookworm of ruminants:
- genus
- how do they get into host
- diseases
- Bunostomum spp.
- penetrate skin
- cutaneous larva migrans
- large numbers can cause anemia, death
what is the common intermediate host for metastongyloides?
molluscs
name two species of metastongyloides and:
- hosts
- where in the host is infection
- disease
1. Aleurostrongylus abstrusus
- many hosts
- in the lungs
- subclinical to serious respiratory disease
2. Parelaphostrongylus tenuis
- white-tailed deer (preferred), camelids, sheep, goats
- infects meningeal veins and venous sinuses
- infects spinal cord and brain
what are the two most effective ways to control metastrongyloidea?
- anthelminthics
- control mollusks (snails, slugs)
what order and superfamily include heartworms?
Order Spirurida
Superfamily Filaroidea
what is the typical intermediate host of the filaroids?
arthropods, such as insects
how could you tell a male adult heartworm from a female?
males have a coiled tail
what is the genus and species of heartworm?
Dirofilaria immitis
what geographic location will you typically find Dirofilaria immitis?
anywhere there are mosquitoes, especially the Gulf Coast. Mid-Atlantic, and Mississippi River states
how long can microfilaria survive in the blood of the definitive host?
1 year
what is the life cycle for Dirofilaria immitis?
- mosquito bites dog and L3 crawl into bite wound, entering the host's bloodstream
- adults in the right heart and pulmonary arteries
- females release microfilaria into the blood
- mosquito takes a blood meal and the microfilaria develop up to L3 in the mosquito GI tract.
- the cycle repeats
Dirofilaria immitis:
- how do L3 reach the arteries?
- how long does it take them to reach the pulmonary arteries?
- what is the prepatent period?
- how long can adults live in dogs?
- L3 migrate through the tissue and abdominal wall to thorax and enter the bloodstream
- Takes about 70 days to reach the pulmonary arteries
- PPP = 190 days (about 6 months)
- adults can live 5+ years in the dog
true or false: microfilariae produced in a dog must go to a mosquito to develop?
True
what are the two major tests for heartworm infection?
- ELISA antigen test
- Knotts test (see microfilariae in the blood; only good for patent infections)
how long after Dirofilaria immitis infection is antigen detectable by an ELISA test?
5 months
if a dog is not on heartworm medication and over 7 months of age, why should you test for heartworm infection before starting a prophylaxis regimen?
because if microfilariae are in high abundance, the heartworm preventative may kill them and cause significant problems such as anaphylaxis.
how do monthly heartworm preventatives control heartworm infection?
They kill larvae acquired in the previous 45-60 days
why could doxycycline be effective at treating a heartworm infection?
doxycycline kills Wolbachia, an obligate symbiont o fDirofilaria immitis.
how do macrolides affect Dirofilaria immitis for the following life stages?
- microfilariae
- L3
- "early" L4
- "late" L4
- adult
- microfilariae: kill
- L3: kill
- "early" L4: kill in 1-3 doses
- "late" L4: kill with chronic monthly administration
- adult: sterilizes most; NOT a treatment
why is heartworm testing in cats problematic?
- cats are rarely microfilariae-positive
- antigen test may be negative due to low worm numbers or immature worms
- antibody tests have been developed
what is the most common manifestation of heartworm disease in cats?
HARD - heartworm associated respiratory disease
why is heartworm difficult to treat in cats?
because the arsenicals are fatally toxic
besides dogs and cats what other pet can get typical heartworm disease?
ferrets
what causes "summer sore" in horses?
Habronema, a spiruid parasite of the equine stomach
what is Thelazia, what does it infect, and where in the body of the host does it infect
Thelazia is a spiruid parasite of horses, ruminants, and dogs that infects the eye
Physocephalus and Ascarops: what are they, what do they infect, where in the host do they infect, and what diesase to they cause?
spiruid parasites of pigs that infect the stomach and cause catarrhal enteritis
Physaloptera:
- type of parasite
- hosts
- site of infection in the host
- life cycle
- Dx
- spiruid parasite
- dog, cats, various wild animals
- infects the stomach
- beetle, cricket intermediate host
- diagnose eggs in the feces
Habronema
- type of parasite
- hosts
- site of infection in the host
- life cycle
- clinical signs
- spiruid
- infects horses
- lives in nodules in the stomach
- flies deposit larvae around mouth or other moist areas
- larvae cause "summer sore" in other locations; can be mistaken for exuberant granulation tissue, neoplasia
Thelazia:
- type of parasite
- hosts
- site of infection n the host
- life cycle
- treatment
- type of parasite: spiruid; "eye worm"
- hosts: horses, cattle, dogs
- site of infection n the host: eye
- life cycle: fly intermediate host
- treatment: removal of worm
if a client finds dark brown worms in their toilet bowl, what are they likely to be?
Horsehair worms, which are not parasitic to mammals
what is the genus name of whipworms and what is their location in the host?
Trichuris, located in the large intestine
Trichuris vulpis
- location in host
- life cycle
- prepatent period
- Dx
(canine whipworm)
- infects the cecum and colon
- eggs develop infective stage in environment
- dogs infected by ingesting infective eggs
- 3 month PPP
- eggs found in a fecal float, but this may be difficult because of the long PPP and intermittent egg shedding
canine whipworm genus and species
Trichuris vulpis
Trichuris vulpis
- Tx
- Control
(canine whipworm)
- Fenbendazole, febantel
- give now, 3 weeks, and 3 months
- remove feces
- expose eggs to desiccation
comment on the zoonotic potential of Trichuris
(whipworm)
very host specific
name three Genuses of capillarid worms (Order Enoplida)
1. Eucoleus
2. Pearsonema
3. Aoncotheca
what are three species of capallarids that infect dogs and where in the body to they infect?
Eucoleus aerophilus - bronchial parasite (also cats)
Eucoleus boehmi - nasal
Pearsonema spp - bladder (also cats)
what are three species of capallarids that infect cats and where in the body to they infect?
Eucoleus aerophilus - bronchial parasite (also dogs)
Pearsonema spp. - bladder (also dogs)
Aoncotheca putorii - intestine
which capillarid species infect ruminants?
Aoncotheca spp.
What is the basic life cycle of Trichinella?
- adult worms in SI or warm blooded animals
- females produce larvae that encyst in skeletal muscle of the same host
- infection is from carnivorism of the tissue cysts
in what domestic animal in particular is Trichinella important?
pigs
how are Trichinella cysts killed in meat so that they are not infective?
cooking and freezing
what is the most common source of human Trichinella infection in the US?
Bear meat
what is the genus and species name of equine pinworm, how is the host infected, how is it diagnosed and treated?
- Oxyuris equi
- infected by ingestion if eggs
- fertilized females glue eggs to the perianal area
- irritation from worm movement and egg glue
- pruritis, "rat tailed" appearance
- do the scotch tape test for eggs
- treat with anthelmintics and clean blankets, etc.
Strongyloides stercoralis
- type of parasite
- host
- life cycle
- Dx
- a nematode of order Rhabditida
- dog small intestine
- parthenogenic females release L1
- L1-->L3 in environment
- infection through skin penetration
- diagnosis with the Bearmann test
comment on the reproductive capability of tapeworms and flukes
They are hermaphrodites, but prefer to mate when possible
what is the common name for Cestodes?
Tapeworms
What are the two Orders of Class Cestoda?
Order Cyclophyllidea
Order Pseudopyllidea
with regards to the cyclophyllid type of tapeworms, comment on the following:
- mouth parts
- number of intermediate hosts
- egg morphology
- prevalence
- mouth parts: suckers
- 1 intermediate host
- egg has hooks
- prevalence: the most common type of tapeworm
with regards to the pseudophyllid type of tapeworms, comment on the following:
- mouth parts
- number of intermediate hosts
- egg morphology
- prevalence
- mouth parts: bothria
- 2 intermediate hosts
- egg does not have hooks
- prevalence: the less common type of tapeworm
what are the 3 regions of the body of the tapeworm and what is their appearance and function?
1. scolex - skinny part with suckers/hooks/bothira; attaches to gut wall
2. neck: distal to the scolex; region of cell division and production of stobila
3. strobila: collective term for all of the segments of the tapeworm, which are produced by the neck
from what do the stobila of a tapeworm grow and how are older/younger stobila positioned on the worm?
- the stobila (segments) grow from the neck

- the oldest segments are most distal to the scolex and neck
what are the three stages of devlopment for a tapeworm segment?
1. immature
2. mature (has repro organs of both sexes)
3. gravid: contains fully developed eggs
what is the general term used for a larval tapeworm in an intermediate host?
metacestode
what is the most important Family of tapeworms?
Taeniidae
comment on the eggs of Taeniidae:
- fecal exam
- appearance and contents of egg
- how they differ in appearance from genus to genus
- may or may not be present in feces because they are passed in segments
- a thick brown "shell" with radial striations that look like a sunburst
- contains an embryo called an oncosphere or hexacanth with 6 hooks
- all eggs in this family are identical
what are the intermediate hosts and definitive hosts of Taeniidae?
- intermediate host is an herbivore or omnivore mammal
- definitive host is a carnivore
what are the four metacestode stages of Taeniidae in order of increasing complexity?
1. cysticercus
2. strobilocercus
3. coenurus
4. hydatid
what is a cysticercus and what is its gross appearance? What is an infection with them called?
a larval stage of the Taeniidae tapeworms

- fluid filled bladder
- inverted, invaginated scolex
- cysticercosis
comment what happens when a cysticercus is ingested? What does it produce?
(Taeniid tapeworm larva)

- the cyst is lysed, releasing the scolex, which attaches to the intestinal wall
- one cysticticercus produces one adult becuase it has only one scolex
name the two genera of Taeniid tapeworms in the US that infect small animals
1. Taenia
2. Echinococcus
name seven species of Taeniid tapeworms with small animal definitive hosts.
1. Taenia pisiformis
2. Taenia taeniaeformis
3. Taenia hydatigena
4. Taenia ovia
5. Taenia multiceps
6. Echinococcus granulosis
7. Echinococcus multilocularis

(5 Taenia and 2 Echinococcus)
what is the life cycle for Taenia pisiformis:
- eggs
- intermediate host
- larval stage
- adult size
- eggs shed in segments
- rabbit intermediate host
- cysticercus in rabbit
- adults up to 70 cm
what is the life cycle for Taenia taeniaeformis:
- eggs
- intermediate host
- larval stage
- adult size
- eggs shed in segments
- rodent intermediate host
- strobilocercus in rodent
- adults up to 2 m
comment on the clinical significance, Dx, and Tx of Taenia taeniaeformis and Taenia pisiformis
- minor, if any signs
- undesirable for clients
- Dx: segments on animal or in environment
- Tx: praziquantel, epsiprantel, FBZ; restrict hunting
Taenia hydatigena:
- definitive host
- intermediate hosts
- larva
- practical importance
(tapeworms)
- dog is definitive host
- wild and domestic ruminants and pigs are intermediate host
- larva are large cysticerci attached to peritoneal membranes
- may cause concern at slaughter of food animals
Name the intermediate and definitive host for the following:
- Taenia ovis
- Taenia serialis
- Taenia multiceps
(tapeworms)
- Taenia ovis: IH = sheep; DH = dog
- Taenia serialis: IH = rabbit; SH = dog
- Taenia multiceps: IH = sheep; DH = dog
comment on the importance of Taenia ovis
(tapeworms)
- cystecerci in sheep muscle
- causes carcass condemnation
- cases found in Canada and western US
Taenia multiceps
- hosts
- larval stage
- geographic location
(tapeworms)
- IH = sheep; DH = dog
- coenurus is the larval stage (fluid-filled bladder with many scoleces; 1 coenurus gives rise to many adults)
- very rare in the US
what is a coenurus?
larval stage of a Taeniid comprising fluid-filled bladder with many scoleces. 1 coenurus gives rise to many adults
Echincoccus:
- two important species
- size of adults
- comments on larvae
(tapeworms)
- Echincoccus granulusis and Echincoccus multilocularis
- very small adults (compared to large Taenia)

LARVAE:
- mestacestodes undergo asexual mulitplication
- hyatid cyst (like coenurus, but can form small cysts inside of the primary cysts)
- thousands of scoleces can form
Echinococcus granulosus
- hosts
- location in definitive host
- geographic location
- how are eggs passed?
- type of metacestode
- location of metacestode in intemediate host
(tapeworms)
- IH = sheep; DH = dog
- location: rare in US, but common in sheep producing areas
- in SMALL intestine of canid
- eggs passed in tiny tapeworm segments
- unilocular hyatid cyst, usually in the liver or lung of sheep
what is a hyatid cyst?
a fluid-filled membrane containing many cysts. Like a coenurus, but can form small cysts inside of the primary cysts that can contain thousands of scoleces.
how is Echinococcus granulosus treated in sheep? Dogs?
- sheep: difficult to treat, usually surgical
- dogs: praziquantel
comment on the zoonisis of Echinococcus granulosus
(tapeworms)
- infective to humans by ingestion of eggs
- larval stages can be found in multiple organs, including brain, lungs, liver, spleen, intestines, and bone marrow
Echinococcus multilocularis
- geographic location
- definitive hosts
- intermediate hosts
- larva
- northern US and Canada
- IH = small rodents and humans
- DH = fox, sometines dogs, rarely cats
- larva is a multilocular hyatid cyst (grows by budding chambers, like cancer)
what two species of Taeniidae have human definitive hosts?
- Taenia saginata
- Taenia solium
Taenia saginata
- hosts
- larvae
- prevalence
- Dx and Tx in intermediate host
- Dx and Tx in definitive host
(tapeworms)
- IH = beef; DH = humans
- larvae are cysticerci in bovine muscle
- low prevalence in the US, but increased risk of infections from immigration and occasional contamination of cattle feed (infected guy takes a dump in pasture)
- Dx in cattle: slaughter inspection
- Tx in cattle: none
- Dx and Tx in humans: send them to a "real" doctor
Taenia solium
- hosts
- location in definitive host
- geographic distribution
- larvae in normal intermediate host
(tapeworms)
- IH = pig; DH = human
- small intestine of human
- worldwide, especially developing countries
- larvae are cysticerci in pig muscle
comment on the zoonosis of Taenia solium and Taenia saginata
(tapeworms from pigs and beef)
- if humans ingest eggs, they will host cysticerci
- "cysticercosis, neurocysticercosis"
- symptoms develop when cystecerci die in the nervous system
- headache, confusion, seizures
- leading cause on adult onset epilepsy
- major problem in Mexico and Latin America
In the US, what is the most common way that Taenia solium is trnsmitted?
usually human-human, not from pigs.
Non-Taeniad cyclophyllidean tapeworms:
- intermediate hosts
- metacestode stage
- IH = arthropods
- metacestode is called a cysticercoid (small cyst with invaginated single scolex)
Dipylidium canium
- hosts
- location in host
- how is it acquired by definitve host?
- prepatent period
- Dx
- clinical importance
- Tx and control
(non-Taeniid tapeworm)
- IH - fleas (rarely lice); DH = dogs and cats
- in dog and cat small intestine
- animal eats the flea and becomes infected
- 2 week PPP
- Dx: tapeworm segments in arianal area; rarely, egg packets in fecal
- scooting, owners repulsed by moving segments, zoonotic (young children at greatest risk)
- Tx: praziquantel
- control: get rid of fleas
Ruminant and Equine Tapeworms:
- Genera and hosts
- location in host
- intermediate host
- how does infection occur?
- Anoplocephala: horses
- Moniezia: ruminants
- located in small intestine
- cysticercoid in pasture mites after they ingest the eggs shed in feces of definitive host
- definitive host infected when the mites are ingested while grazing
Anoplocephala perfoliata
- definitive host
- intermediate host
- prevalence
- location of adults
- clinical signs
- Dx and Tx
(non-Taeniid tapeworm)
- DH = horse, IH = pasture mite
- very common infection
- adults in the cecocolic junction of horse
- usually asymptomatic, but can cause inflammation and ulceration
- Dx: fecal often negative; antibody test of limited use
- Tx: praziquantel or 2X dose of pyrantel (part of a normal horse deworming schedule)
Moniezia spp.
- definitive host
- intermediate host
- Dx
- Tx
(non-Taeniid tapeworm)
- DH = cattle; IH = pasture mites
- Dx: segments in manure of young animals; eggs in fecal
- Tx: benzimidazoles
what is the usual intermediate host for avian tapeworms?
arthropods
for the pesudophyllidea tapeworms, what type of intermediate host is rquired?
an aquatic animal such as fish, amphibians, and reptiles
what do the eggs of pseudophyllidea look like in a fecal exam?
they look like fluke eggs except they have a cap
Spiometra spp.
- definitive host
- common name
- common intermediate hosts
- geographic location
(pseudophyllid tapeworm)
- DH = cats and sometimes dogs or wild animals
- "zipper tapeworm" (because of the dots along the middle of its segments)
- infected by eating amphibians or reptiles
- common in SW US (where you find lots of amphibians and reptiles)
Diphyllobothrium spp.
- common name
- definitve hosts
- intermediate hosts
- prevalence
(pesudophyllid tapeworm)
- broad fish tapeworm
- DH = dogs, cats, humans, wildcarnivores
- IH = fish
- no longer seen in US except on House
what is the common name for Trematodes?
flukes
how many orders of trematodes are clinically important?
(flukes)
2
for the trematodes relevant to mammals, comment on:
- morphology
- segmentation
- mouthparts
- egg morphology
- intermediate hosts
(flukes)
- flat, leaf-shaped
- unsegmented
- usually 2 suckers
- eggs with caps ("operculated")
- usually 2 intermediate hosts
- first intermediate host is always a snail
for the trematodes important to mammals, what is the first intermediate host?
(flukes)
always a snail
when a trematode egg hatches, what is released and what distinguishing anatomical feature do they have?
(flukes)
the egg hatches a miricidium, which has cilia

note: this is what is ingested by the snail
when a trematode leaves a snail, what is it called?
(flukes)
cercaria
what is the name of the 2nd larval stage of Fasciola hepatica that is in or on the second intermediate host?
(flukes)
metacercaria
what is the name of the trematode larval stage that the host ingests?
(flukes)
metacercaria
what is the name (taxonomic and common) of the most clinically important trematode in the US?
(flukes)
- Fasciola hepatica
- the liver fluke
Fascolia hepatica:
- hosts
- location in host
- geographic distribution
(liver fluke)
- ruminants
- also dogs, cats, horses, humans, rodents
- worldwide distribution
Fasciola hepatica life cycle:
- adult location and egg release
- egg --> larval stages
- infection of adult
- larval development
- prepatent period
(liver fluke)
- adults are in bile ducts, where they release their eggs
- eggs deposited in water
- eggs hatch into a miricidium
- miriciduim infects snail
- resulting cercaria encysts on vegetation and debris and become metacercaria
- host infected by ingesting the metacecaria
- once ingested, migrates through the intestinal wall and to the liver
- they can crawl all over the liver and end up in bile ducts
- PPP = 10-12 weeks
what are the three areas in the US with the highest prevalence of Fasciola hepatica?
(liver fluke)
- gulf coast
- pacific northwest
- hawaii
Clinical signs of Fasciola hepatica in cattle in sheep.
(liver fluke)
Cattle:
- "chronic poor doing"
- anemia, hypoproteinemia
- weight loss
- lower milk production
- gradually develops immunity

Sheep:
- more severe disease, which can be fatal, because they don't develop good immunity
Fasciola hepatica Dx
(liver fluke)
- history, clinical signs
- SEDIMENTATION fecal exam (not very sensitive)
- liver enzyme levels
- sometimes, ELISA antibody test
Fasciola Hepatica Tx and control
(liver fluke)

Tx:
- routine Tx where common
- treat when transmission is low, when worms are adults and smails are dormant
- albendazole (not fenbendazole) and clorsulon

Control:
- management of premeses: drain, fence out marshy areas
- near impossible to control snails
besides Fasciola hepatica, what three other animal flukes are seen in the US?
Fascioloides magna:
- midwest
- liver fluke of whitetailed deer
- infects shep and goats
- Dr. Zajac wants to fry one and eat it if one is found by a deer hunter

Paramphistomum spp.:
- rumen fluke occasionally seen in cattle and in jars in the MDL lab

Paragonimus kellicotti:
- cysts in the lung parenchyma of wild animals, dogs, and cats
Paragonimus kellicotti
- geographic distribution
- hosts
- location in the host
- intermediate hosts
(a lung fluke)
- North America
- wild animals, dogs, cats
- cysts in the lung parenchyma
- 1st IH = snail (obviously)
- 2nd IH = crayfish/crawfish/crawdaddy
- transport hosts may be involved
Paragonimus kellicotti
- clinical importance
- Dx
- Tx
(a lung fluke)
- may be asymptomatic or cause clinical respiratory disease (don't eat raw crayfish)
- Dx: fecal - eggs may float but often distorted; sedimentation is the best
- Tx: we don't need to know. Just look it up.
what are Schistosomes?
A family of flukes that live in the veins of definitive host. Snails release cerceriae that can penetrate human skin, leading to "swimmer's itch"
what parasite causes "swimmer's itch?"
Schistosomes (a type of water-borne fluke)
Heterobilharzia spp.:
- hosts
- how infection happens
- location of parasite
- clinical signs
- Dx
(a fluke)
- wild animals, occasionally dogs
- eggs pass through SI tissues
- infects mesenteric veins of the SI and liver
- diarrhea, melena, hematochezia (frank blood in the feces), vomiting, lethargy
- Dx: tricky. PCR available
Name two species of flukes that act as disease vectors and information regarding them.
Nanophyetus salmincola
- intestinal fluke of carnivores in the Northwest
- 2nd IH = fish
- fluke carries Rickettsia, which causes "salmon poisoning" in dogs

a fluke of bats is a vector of Ehrlichia risticii, which causes Potomac Horse fever. Horses are innocent bystanders
what is the syndrome in human primates in which they think that they have parasites on their skin that makes them itch?
delusional parasitosis