Parasitology 6.08-6.14

What is the common name for phylum nematoda?

round worm

What is the common name for phylum platyhelminths?

flatworm

What is the common name for phylum Acanthocephala?

thorny-headed worms

What is the common name for class monogenea and what is it under?

• under phylum platyhelmiths (flat worm)

• Anchor worms

What is the common name for class trematoda and what is it under?

• under phylum platyhelmiths (flat worm)

• flukes

What is the common name for class cestoda and what is it under?

• under phylum platyhelmiths (flat worm)

• tapeworm

what is this in terms of cestodes (tapeworms)?

procercoid

what is this in terms of cestodes (tapeworms)?

plerocercoid

what is this in terms of cestodes (tapeworms)? where is it found and describe it.

• cysticercoid

• found in arthropodan IH

• enclosed scolex, not inverted

what is this in terms of cestodes (tapeworms)? where is it found and describe it.

• cysticercus

• found in vertebrate IH

• single invaginated

what is this in terms of cestodes (tapeworms)?

• coenurus

• found in vertebrate IH

• multiple invaginated

what is this in terms of cestodes (tapeworms)? where is it found

• hydatid cyst

• found in vertebrate IH

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• Taenia pisiformis adult

• rabbit tapeworm

• scolex with four suckers and a rostellum with two rows of hooks

• rectangular segment

• shiny white strobila

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• taeniid type egg

• taenia pisiformis (rabbit tapeworm)

• thick radially striated shell

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• cycticercus pisiformis

• cysticercus of Taenia pisiformis (rabbit tape worm) (larva)

• fluid filled bladder with an invaginated scolex

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• larva of rat tapeworm

• strobilocercus of Taenia taeniaeformis

• partially developed cysticercus with evaginated scolex and small strobila

What is this egg and species have this egg?

• taeniid type egg

• Taenia pisiformia

• Taenia taeniformis

• taenia spp.

• echinococcus granulosus

what is this in terms of cestodes (tapeworms) and what is the structure shown

• Taenia crassiceps

• budding cysticercus

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• Taenia saginata adult

• beef tapeworm

• unarmed scolex with four suckers

what is this in terms of cestodes (tapeworms)? how can you tell?

• Echinococcus granulosus adult

• 3 or 4 sefments with the posterior segment greater than one half the length of the parasite

(scolex with four suckers and a rostellum with 2 rows of hooks)

what is this structure in terms of cestodes (tapeworms) and what species is it?

• Echinococcus granulosus larva

• hydatid cyst

What caused this and how?

• echinococcus multilocularis

• massive replication (exogenous budding and metastasis)

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• dipylidium caninum (flea tapeworm) adult

• double pored tapeworm of dogs

• fresh segments look like cucumber seeds

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• dipylidium caninum (flea tapeworm) larva

• double pored tapeworm of dogs

• cysticercoid encysted in hemoceol of insect IH

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• dipylidium caninum (flea tapeworm) egg

• double pored tapeworm of dogs

• eggs (oncosphere) in packets

• each oncosphere in thick unstriated shell or embryophore

how do you know which segment belongs to which species?

• trapezoidal is taenia spp.

• cucumber seed is dipylidium caninum

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• anoplocephala perfoliata adult

• creamy white, wedge shaped

• scolex has lappets (bib like structure)

what is this in terms of cestodes (tapeworms)? how can you tell?

• anoplocephala perfoliata egg

• chocolate covered cherry shaped

• thick shelled

• a spair of pring like processes (pyriform apparatus)

what is this in terms of cestodes (tapeworms)? how can you tell?

• moniezia spp. eggs

• triangular to square

• thick shelled

• pyriform apparatus

what is this in terms of cestodes (tapeworms)? what is the common name and how can you tell?

• Diphyllobothrium latum adult

• scolex has a pair of bothria (groove)

• large strobila

what is this in terms of cestodes (tapeworms)? how can you tell?

• Diphyllobothrium latum eggs

• operculate, light brown egg

• ciliated hexacanth embryo called a coracidium

Describe major characteristics of cyclophyllidean cestode egg

• spherical or oval

• 30-50 um

• thick, usually striated outer shell

• shell surrounding hexacanth embryo

• no operculum

• ingestion is the mode of transmission

How do humans become infected with Taenia crassiceps? and what is the medical importance?

• ingestion of tapeworm egg from dog feces

• cysticercus can occur in the eye and cause blindness

Describe the zoonotic and human medical importance of Taenia saginata and the means through which humans become infected?

• normal human parasite

• infection through eating uncooked beef containing cysticercus

Is Echinococcus granulosus zoonotic?

Yes

Describe the zoonotic and human medical importance of echinococcus granulosus and the means through which humans become infected

• people can have hydatidosis after ingestion of an egg passed in the feces of the dog

• expanding hydatid is a space occupying lesion causing pressure necrosis

• rupture of hydatid can cause anaphylactic shock and death

Describe the zoonotic and human medical importance of echinococcus multilocularis and the means through which humans become infected

• people can have alveolar hydatidosis after ingesting and egg passed in the feces of the dog.

• expanding and invasive alveolar hydatid.

• metastases act as a space occupying lesion which causes pressure necrosis of surrounding tissue

• general fatal in spite of treatment

Whats the DH and IH of Dipylidium caninum?

• DH: Dogs, cats, rarely humans

• IH: primarily fleas, also biting lice

Describe the zoonotic and human medical importance of Diphyllobothrium latum and the means through which humans become infected

• 1st IH is copepod (procercoid) → 2nd IH is fish (pleurocercoid) → DH is fish eating mammals including humans

• competition between parasite and host for Vitamin B12, cause anemia in host

which species have taeniid type eggs?

Taenia spp. and Echinococcus granulosus

Which of the species with taeniid type eggs are zoonotic?

• Taenia solium

• Taenia saginata

• Echinococcus granulosus

what is the clinical implication for the dog if we find a taeniid type of eggs in the dog feces?

• indicate an active tapeworm infection

• dog is a definitive host

what is the clinical implication for the human if we find a taeniid type of eggs in the dog feces?

• need to differenciate between Taenia spp. (low zoonotic risk) vs Echinococcus spp. (high zoonotic risk)

What’s the life cycle of Taenia pisiformis (rabbit tapeworm)?

• predator-prey life cycle

• eggs released from segments are ingested by the IH (rabbit)

• hexacanth larva hatches and migrates to the peritoneal cavity or liver to mature to a cysticercus

• when a dog eats the rabbit, the scolex in the cysticercus evaginates, attaches to the gut and begins to form strobila

• PPP 6-8 weeks

How do you control and treat Taenia pisiformis (rabbit tapeworm)?

• specific cestodicides - praziquantel (Droncit), nitroscanate (Lopatol), epsiprantel (Cestex)

• prevent hunting to block transmission

What’s the life cycle of Taenia taeniaeformis (rat tapeworm)?

• typical predator-prey life cycle

• eggs released from segments are ingested by the IH (rat)

• hexacanth larva hatches and migrates to the peritoneal cavity or liver to mature to a cysticercus

• when a cat eats the rat, the scolex in the cysticercus evaginates, attaches to the gut and begins to form strobila

• PPP 6 weeks

How do you control and treat Taenia taeniaeformis (rat tapeworm)?

• specific cestodicides - praziquantel (Droncit), nitroscanate (Lopatol), epsiprantel (Cestex)

• prevent hunting to block transmission

What’s the life cycle of Taenia saginata (beef tapeworm)?

• eggs released from segments are ingested by the IH (cattle)

• hexacanth larva develops and penetrate small intestine to skeletal and cardiac muscle

• second stage larva (cysticercus) are infective in 10-12 weeks and remain viable for 9 - 24 month.

• People ingest uncooked meat and gets infected.

• cysticercus evaginates and attaches to the small intestine and begin to from strobila

• PPP 3.5 months

How do you control Taenia saginata (beef tapeworm)?

• full cook the meat before eating

describe the life cycle of Taenia crassiceps

• predator-prey cycle (foxes and groundhogs)

• zoonotic threat if dog becomes infected through hunting

what is the control of Taenia crassiceps?

• specific cestodicides - praziquantel (Droncit), nitroscanate (Lopatol), epsiprantel (Cestex)

• precent hunting to block transmission

describe the life cycle of Echinococcus granulosus

• predator and prey cycle

  • Sylvatic moose and wolf

• adult infect the small intesine of the wolf

• immature stages found in the liver and other organs of the moose

• PPP: 6 weeks

What is the control and treatment of Echinococcus granulosus for both dog and human

• Dog

  • praziquantel

• human

  • cyst usually identified radiographically and commonly misdiagnosed as tumour

  • surgical intervention + anhelmintics

describe the life cycle of Echinococcus multilocularis

• predator prey cycle

  • sylvatic fox and rodent

• adult infect the small intestine of the fox

• immature stages found in the liver and other organs of the rodent

• PPP: 6 weeks

What is the control and treatment of Echinococcus multilocularis for both dog and human

• Dog

  • praziquantel (Droncit)

• human

  • cyst usually identified radiographically and commonly misdiagnosed as tumour

  • surgical removal of alverolar hydatid cyst is difficult and can be unsuccessful (fatal disease)

Describe the life cycle of Dipylidium caninum (flea tapeworm)

• eggs usually passed within segments (MOTILE)

• liberated eggs are ingested by flea larvae

• hexacanth embryo hatches from embryophore and penetrates into body cavity of flea

• cysticercoid matures there (survive metamorphosis)

• When adult flea is ingested, scolex attaches to gut and strobilla matures

• PPP: 2-3 weeks

How to control and treat Dipylidium caninum?

• cestocides - e.g. praziquantel (droncit), epsiprantel (Cestex)

• flea control to reduce transmission

Describe the life cycle of Anoplocephala perfoliata

• eggs released from segments are ingested by the IH (oribatid mite)

• hatches and the hexacanth larva develops into second stage larva (cysticercois)

• equid ingest infected mite, scolex from immature tape worm attach to mucosa of the intestine and forms strobila

• PPP: 6 weeks

Describe control and treatment of Anoplocephala perfoliata

strongid P or strongid T

describe the life cycle of moniezia spp.

• eggs (feces) → oribatid mite → ruminant

• PPP: 6 weeks

what is the treatment of moniezia spp.

albendazole

Describe the life cycle of Diphyllobothrium latum

• 1st IH copepod (procercoid) → 2nd IH fish (pleurocercoid) → DH fish eating mammals

What is the treatment of Diphyllobothrium latum

No cestodicides have label claim but can try praziquantel

what is the common name for Nematoda?

roundworms

What is this

female nematodas (roundworms)

What is this?

male nematodes (roundworms)

What is this and why?

• adult Toxocara canis

• Large and white

What is this and why?

• Toxocara canis egg

• thick shelled

• pitted egg containing a single larva

• dark brown

this is from a dog with painful stomach, worms are foudn at bile ducts, what species can this be?

Toxocara canis

What is this and why?

• toxocara cati

• cervical alae (arrow head)

What is this and why?

• toxocara cati

• cervical alae (arrow head)

What is this and why?

• eggs of toxocara cati

• thick shell

• outter shell finely pitted

• dark brown

What is this and why?

• toxascaris leonina

• oval and light coloured

• smooth thick outer shell

• ruffled appearance of inner shell

whats shown in the image?

• Left: toxascaris spp. egg

• right: Toxocara spp. egg

what does it mean if a species name has “ascaris” in it?

there is no vertical transmisison

What is this and why?

• parascaris equorum

• dark egg

• thick finely pitted outer protein shell

• if the protein layer is lost during flotation procedure, the egg is smooth, colourles, middle layered shell exposed

What is this and why?

• ascarid suum

• ovoid and yellow

• thick shelled

• irregularly mamillated outer shell

Which species would this be if this was found in the intesine of chickens, pigeons and turkeys?

Ascaris galli

cecal leision caused by mucosal migration of the larvae, what could this be?

Heterakis gallinarum

what is this and why?

• Baylisacaris procyonis

• dark or amber

• embryo more or less completely fill the shell

If this larva migrate in the brain and cause neurological issue, what could this be?

Baylisascarid procyonis larva

What is the biological characteristics of Ascarid eggs?

• highly resistant to environmental eggs

• eggs mature to contain L3 in the environment before becoming infective

• eggs remain infectious for extended periods

what is the morphological characteristics of Ascarid eggs?

Shape	Round to oval
Size	Varies by species (typically 60–90 µm in diameter)
Shell	Thick, multi-layered shell
Outer Surface	Often rough or pitted (Toxocara spp.) or smooth (Parascaris spp.)
Color	Yellow-brown
Contents	Single-celled zygote

How do humans get infected with Ascarids

usually fecal oral infection

Describe the zoonotic and human medical importance of ascarid nematodes

• humans can become paratenic host with larva migrating through the body

• ascarid larval migration can give rise to the syndromes of visceral larva migrans (VLM) and ocular larva migrans (OLM)

• species particular important: toxocara canis of dogs and Baylisascaris sp. in racoon

in which species that vertical transmission is esp important when it comes to Ascarid infection.

• Toxocara canis

• Toxocara cati

what types of vertical transmission does toxocara canis use?

• pups are primarily infected in utero by transplacental transmission

• some larval can be transmitted through transmammary transimission

what types of vertical transmission does toxocara cati use?

• young kittens are infected primarily by transmammary passage of larva

Describe the role of vertical transmission in the epidemiology of ascarid infections in small animals

• High Prevalence in Neonates

  • almost 100% of puppies from infected mother with toxocara canis are infected.

• high environmental contamination

  • infected neonate shed within a few weeks

  • eggs are environmentally resistant

• increased risk of zoonotic transmission

  • early infection of puppies and kittens shed a large number of eggs

• difficult to eradicate in breeding population

Describe a general ascarid lifecycle

• direct life cycle

• prolific (as many as 200k eggs per female)

• eggs mature to contain L3’s in the environment before becoming infective - oral infection usually

• L3 penetrate small intestine and undergo migration

• many alternate routes with hypobiosis as well as transmammary and/or transplacental transmission

• larvae eventually reach the small intestine and rapidly mature to adults and begin to produce eggs

• PPP variable but usually long if the larvae undergo significant migration

• paratenic hosts may be involved

• eggs remain infectious for extended period

How does toxocara canis’s life cycle vary from the general ascarid life cycle?

life cycle in pups

• less than 3 months (tracheal migration with PPP of 4-5 weeks)

• 3-6 months (increasing somatic migration)

• 6 months or older (only somatic migration)

• most pups infected in utero by transplacental migration of larvae from bitch to fetus

how does the transplacental and transmammary transmission work for Toxocara canis?

• some (not all) arrested (hypobiotics) larvae are mobilized by pregnancy

• enter liver and lung of fetus and wait for birth of pup

• finish (do not undergo complete) tracheal migration and form adults - PPP shortened to 3 weeks

• some larvae may enter milk and infect pups by transmammary route (rarely)

how does other routes of transmission work for Toxocara canis?

• bitch may get infected by ingesting larvae in feces of pups

• ingestion of paratenic hosts containing larvae may give rise to short-lived patent infections in adult dogs (no migration)

How does taxocara cati’s life cycle vary from the general ascarid life cycle?

• L3 undergo tracheal migration in kittens

• L3 undergo somatic migration in older feline

• transmammary infection is most important

• paratenic hosts may give rise to short lived infections in older cats with oppotunity to hunt

How does toxascaris leonina’s life cycle vary from the general ascarid life cycle?

eggs release L3 in intestine and they undergo a mucosal migration (NO tracheal migration)

How does parascaris equorum’s life cycle vary from the general ascarid life cycle?

direct life cycle with tracheal migration through liver and lungs

How does Ascaris suum’s life cycle vary from the general ascarid life cycle?

direct life cycle with tracheal migration through liver and lungs

How does Ascaridia galli’s life cycle vary from the general ascarid life cycle?

• L3 enter mucosal and undergo mucosal migration

How does Heterakis gallinarum’s life cycle vary from the general ascarid life cycle?

• larva migrate to CECA and enter mucosa

• larval moves to lumen again after 3 molts to become adults (mucosal migration)

How does Baylisascaris procyonis’s life cycle vary from the general ascarid life cycle?

• visceral larval migrans in paratenic host