Order Ascaridida Flashcards
What are the general features of the Order Ascaridida?
Large White, opaque stout bodied Three lips around mouth Very prolific Eggs have thick shell, one cell Larvae reach infective stage inside eggs Located in the small intestine Some are zoonotic
What species infects pigs?
Ascaris suum
What species infects horses?
Parascaris equorum
What species infect cattle?
Toxocara vitulorum
What species infects dogs?
Toxocara canis
Toxocaris leonine
What species infects cats?
Toxocara cati
Toxocaris leonine
What species infects birds?
Ascardiia galli
Heterakis gallinarium
Heterakis isolonche
What are the main features of Ascaris suum?
Infects pigs
Most common GI parasite in pigs
High prevalence for pigs less than 6 months old
Females are very prolific
Worm is short lived
Very large worm
Adults within large intestine but can also be in bile and pancreatic ducts and stomach with heavy infestations
Is zoonotic
Larvae migrate
Can infect humans and cause VLM
Three lips
Posterior end of males is bent with 2 spicules
Eggs are brown/yellow colour and are mammilated (rough edges) with one cell inside
What is the lifecycle of Ascaris suum?
Females can lay up to 200 eggs per day
Eggs shed in the faeces, eggs are very resistant due to thick shell - can survive long time in environment
Infective larvae (L3) develops in the eggs
Eggs ingested with L3
Larvae released from eggs, travel to liver, enter caudal vena cava, heart, pulmonary capillaries, alveoli, trachea, bronchi, swallowed, mature in small intestine.
Infection via ingestion of Embryonated L3
What are the main features of Parascaris equorum?
Infects horses Located in small intestine Whitish Very large Strout appearance Three conspicuous lips Eggs are brownish with very thick shell, one cell inside.
Lifecycle same as ascaris suum –> L3 within eggs are ingested, larvae break out of shell, move to liver, heart, lungs, swallowed, small intestine to mature.
What are the main features of toxocara vitulorum?
infects calves
Located within small intestine
Three defined lips
Eggs –> thick shelled, one cell, outer layer pitted (strawberry but circular)
Eggs pass into faeces, Infection via ingestion of embryonated L3, larvae break out and move to the visceral tissues and enter hypobiosis. Around parturition, the larvae are activated and transmit via transmammary and the parasites mature within the small intestine of the calves.
What is the infection route of the parasite toxocara vitulorum?
Infection of host, hypobiosis until parturition, larvae travel via milk into newborn’s small intestine and mature.
Infection of mother occurs via ingestion of embryonated L3 eggs
What are the main features of toxocara canis?
Most common canids parasite Adults located in small intestine Zoonotic potential --> VLM and OLM Three defined lips Cervical alae present - small Terminal appendage (digitiform) Eggs are similar to toxocara vitulorum --> thick shell, once cell, looks like strawberry (pitted) and dark brown colour.
What are the routes of transmission for Toxocara canis?
Adults:
Ingestion of embryonated L3 eggs
Immature parasites from vomit / faeces of pups
Paratenic hosts - humans, cats, birds, earthworms, etc
Puppies:
Transmammary
Transplacental
What is the lifecycle of Toxocara canis?
Females are very prolific
Eggs shed in faeces
embryonated L3 are ingested.
Tracheal migration –> under 3 months old –> travel from liver to lungs to the small intestine where they mature
Somatic migration –> dogs older than 3 months –> travel from liver to visceral tissues (muscles, kidney, brain), enter hypobiosis and remain forever
Pregnant females signal hormones which reactivate larvae and they migrate to foetus via transplacental or offspring via transmammary infection and infects intestine.
Males will destroy the parasites if healthy, if immunosuppressed the larvae can reactivate and travel to small intestine and mature
contains paratenic hosts = humans, etc.
