Week 1 Flashcards
Significance of ascarids (common roundworms- mostly SI)

Mammals, birds, other
* commonly usually young hosts <1 year unless immuno suppressed
* old animals can represent reservoirs
* Usually host and site specific (adults; mostly SI); other sites (larvae**)
* Some are zoonotic; can use paratenic/ transport hosts (e.g. earthworms)
* Production losses and clinical disease

Usually large adults 5-15 cm
Females and males (males 2 spicules)
Three lips
Some have alae (wings) and or bulbus
* oviparus- lay formed eggs without larvae in them
* All ascarids need the eggs to mature in the environment for them to be infective

Ascaris (thick-shelled) eggs (sticky)
Bottom egg has L3 and is infective to the host (once ingested parasite can migrate)

* Ascaris suum
* Direct LC
PPP=months
* females lay hundreds of thousands of eggs everyday
* Hepatopulmonary migration
* Can be transported by earthworms, but no development occurs in the earthworm.
* eggs are ingested–> eggs are pretreated in the stomach- loosens up the shell–> SI–> change in pH activates the larvae to come out–> transported passively in the blood stream to the liver–> migration in the liver about 5 days (move quick due to immune response is rapid in the liver)–> eventually up the trachea–> swallowed–> L4 ends up in stomach–> SI and establishes

Ascaris suum
* alpha-pepsin and alpha-trypsin enzymes
* maldigestion and malabsorption
* impaction can occur
* can sometimes perforate SI but rare

Hepatitis parasitaria multiplex of Ascaris suum
* Mechanical damage and eosinophilic inflammation > fibrosis (repair) > regeneration

* Ascaris suum
Mechanical damage to lungs as well, haemorrhage and eosinophilic inflammation (IgE/ histamine)–> rapid, shallow breathing with coughing; secondary infections (atypical host> anaphylactic response)
Effects and consequences of Ascaris suum


Parascariasis (impaction in horses)

Parascaris equorum

Parascaris equorum (Ascarid)
Ascarids of canids and felids
* Toxocara canis- also has transplacenta transmission, can have transmammary as well, oral, and hepatopulmonary
* Toxocara cati- transmammary or transcolostral transmission, oral, hepatopulmonary
* Toxascaris leonina- oral, intestinal wall




which one is which?

Toxocara canis LC
Young animal < 3 months–> oral infection route if not previously infected–> HP migration–> establishes in SI
* After 3 months dogs become more resistant. The parasite tends to be blocked from migration. Does not migrate up the trachea anymore.
** rodents MAY play a role- they carry L3s or premature L4s– larval establish directly in the gut
** Can undergo arrested development- sequester away in the muscle tissues and WAIT– no significance in the male dog because they don’t go anywhere.. but the female dog this plays a huge role in transmission (last 1/3rd of pregnancy- larvae become activated- come out of arrested state- migrate to the placenta via the umbilical cord get into the foetus in utero- undergo hepatopulmonary migration in the foetus)
** when eggs are excreted from the dog they are not directly infective, it takes 2-3 weeks of development
** zoonotic, cause ocular granulomas
** Larvae are not fussy, but Toxocara canis only want the SI of a canid host**
PPP of oral route= 4 weeks
PPP in puppy= 2-3 weeks


Canine toxocariasis

Canine toxocariasis
Toxascaris leonina LC
No HP migration, it does migrate in the intestinal wall, oral transmission
Toxocara vitulorum

Young animals infected orally BUT the main way it passes on to offspring is via milk
* Mainly in the tropics
Control “equation” general

Control of ascarids general considerations
* Prolific egg layers (heavy contamination)
* hygiene (host and environment)
* most disinfectants have no nematocidal effect
* young animals usually develop good immunity
* Some species are zoonotic
* Direct LC: oral transmission, migratory routes: HP, TP, TM, S, M > changes PPP
* Differential drug efficacy (adult vs. larval stage)
PPP in months? Migration?






































































































