Lecture 3 Flashcards
What kind of life cycle to ascarids typically have?
Direct
What are the primary hosts of Toxocara cati?
Wild and domestic felids
What is the most common method of infection with T. cati in wild felids and feral cats?
Ingestion of paratenic (transport) hosts
Rodents, birds, chickens, earthworms, ruminants, etc.
Identify this species and describe how to differentiate it from another closely-related ascarid.
Toxocara cati
Note the broad, arrow-shaped cervical alae, which are much more distinct than those found in T. canis.
How would you tell the difference between the eggs of T. cati and T. canis?
T. cati eggs are very similar to those of T. canis, but are smaller.
How many modes of infection are possible with T. cati?
3
Ingestion of larvated eggs (fecal-oral)
Ingestion of paratenic host
Lactogenic
(Recall that T. canis can also move trans-placentally)
True or false:
After ingestion of a paratenic host with T. cati or after lactogenic transmission, it is possible for adults to develop directly in the host intestine instead of undergoing migration.
TRUE
Where do T. cati eggs hatch after being swallowed by the host?
Duodenum
(stomach in T. canis)
How long does it take for freshly-laid T. cati eggs to become infectious?
2-6 weeks
How long does it take for freshly-swallowed T. cati eggs to hatch and migrate to the lungs?
~4 days
True or false:
T. cati chooses whether to perform tracheal migration or somatic migration based on the host’s age, just like T. canis.
FALSE
In T. cati, tracheal migration predominates regardless of age.
This is why trans-placental infection is not a concern for this parasite.
What is the pre-patent period of T. cati?
8 weeks
True or False:
You would expect to see a lot of hypobiotic larvae in an adult cat with a T. cati infection
FALSE
Recall that T. cati does not usually undergo the Liver/Lung/Somatic migration.
True or False:
In the case of lactogenic transmission with T. cati, the pre-patent period is often reduced.
TRUE
In lactogenic transmission, the larvae will often directly develop in the small intestine without undergoing migration.
This can shorten the pre-patent period to as short as 3 weeks.
In the case of lactogenic transmission with T. cati, when are hypobiotic larvae re-activated in female cats?
Late pregnancy to early lactation
If a cat is infected with T. cati during gestation, where will the larvae end up?
Most will go directly for lactogenic transmission.
Would you expect there to be a lot of hypobiotic larvae in non-feline hosts infected with T. cati?
Yes
In paratenic hosts, the Liver/Lung/Somatic pathway predominates, resulting in hypobiotic larvae spread throughout the body.
What would you expect the minimum pre-patent period to be in the case of a cat that ingests a paratenic host infected with T. cati larvae?
3 weeks
The pre-patent period can be reduced from 8 weeks because many larvae will not migrate, but will develop directly in the small intestine.
Which animal serves as an important reservoir for T. cati infections?
Rodents
Important paratenic hosts.
How long do adult T. cati worms survive in feline hosts?
4 to 7 months
How long does it take for freshly laid T. cati eggs to become infective?
2 weeks or more.
List some clinical signs associated with Toxocara infections in cats and dogs.
Potbelly
Ill thrift, emaciation (poor doer)
Potentially sneezing/coughing
Vomiting +/- mucoid diarrhea
Kittens and adult cats are often asymptomatic
Which drugs could you use to treat T. cati infections?
The BIG THREE plus Emodepside
Note that there are fewer anthelmintic drugs approved for cats than there are for dogs.
What is the proper deworming regimen for a kitten infected with T. cati?
Every 2 weeks until 3-4 months old.
What drug could you use to prevent lactogenic transmission of T. cati to kittens?
Emodepside (Profender)
Treat mother 5-6 days before parturition.
Name an ascarid that infects both dogs and cats.
Toxascaris leonina
Is this Toxascaris leonina or Toxocara cati?
Toxascaris leonina
This species has cervical alae more similar to that of Toxocara canis.
Is this Toxocara canis or Toxocara cati?
Toxocara canis
Adult morphology of this worm is very similar to that of Toxascaris leonina
Is this Toxascaris leonina or Toxocara cati?
Toxocara cati
Note the broad, heart-shaped cervical alae.
List some characteristics of the eggs of Toxascaris leonina
Oval to ellipsoid
Shell is smooth, thick, and colorless
Eggs contain a single cell
Cell occupies less space in shell than Toxocara
Identify these eggs
Top: Toxocara
Bottom: Toxascaris
Note how the Toxascaris egg has a smooth shell. Also note that the cell in the egg takes up less space than in Toxocara.
How many modes of infection are there for Toxascaris leonina?
2
Ingestion of larvated eggs (fecal-oral)
Ingestion of paratenic host
How long does it take for newly-laid Toxascaris eggs to become infective?
6-10 days
What is the pre-patent period in a Toxascaris infection?
8-10 weeks
Would you expect to see hypobiotic larvae in a dog with a Toxascaris infection?
NO
Toxascaris does not undergo the Liver/Lung migration in the primary host. Larvae directly develop into adults in the small intestine.
Why is there no transplacental or transmammary transmission in Toxascaris infections?
Larvae do not undergo the Liver/Lung migration, and thus cannot deposit hypobiotic larvae in the tissues.
Why is Toxascaris typically less pathogenic than Toxocara?
No Liver/Lung migration
In the case of Toxocara, much of the disease in the host is caused by larvae migrating through the tissues.
What are the clinical signs associated with Toxascaris infection?
In the case of heavy infections:
Vomiting
Diarrhea
What drugs are used to treat Toxascaris infections?
Same as in Toxocara (the BIG THREE plus Emodepside)
Most are extra-label
What are the potential zoonotic complications with the ascarids of dogs and cats?
Can cause visceral and ocular larva migrans in humans
(humans serve as a paratenic host)
Identify these eggs.
Parascaris equorum
round to ellipsoid
thick, robust, pitted shell
90-100 micrometer diameter
sticky albuminous surface
How many modes of transmission are there for Parascaris?
Only 1
Fecal-oral transmission
What is the pre-patent period in Parascaris infections?
72-110 days
(10-14 weeks)
What is the life cycle of Parascaris once eggs are swallowed?
Hatch in small intestine
Liver/Lung/Tracheal migration
Coughed up, swallowed
Adults develop in small intestine
(No somatic migration)
Would you expect to see hypobiotic larvae in a host infected with Parascaris?
NO
Parascaris does not do somatic migrations.
This is also why there are no transplacental or transmammary transmissions in Parascaris infections.
List some clinical signs associated with Parascaris infections in the lungs of horses.
Verminous pneumonia (“summer cold”)
Fever, cough, increased respirations
Dirty white mucopurulent nasal discharge
History of relapses after antibiotic treatment
Spontaneous recovery after 3-6 weeks
List the clinical signs associated with low-level Parascaris infections in the GI tract of horses.
Enteritis
Pot-bellied appearance
Poor growth and weight gain
Decreased appetite
Colic
Diarrhea and pale, fetid feces
List the clinical signs associated with high-level Parascaris infections in the GI tract of horses.
Decreased or increased gut motility
Intussusception
Impaction with worms
Intestinal rupture and peritonitis, death
