Lecture 47 - Pasture-based nematodes Flashcards
what are the 3 modes of nematode transmission
- tracheal
- somatic
- mucosal
tracheal migration
migrate by the bloodstream to the liver and then to alveoli in the lungs which are coughed up and swallowed. adult worms mature in the small intestine
somatic migration
larvae will be transported to systemic circulation to various organs and somatic tissues where they encyst as arrested larvae
mucosal migration
after infection, larvae migrate to intestinal muscosa where they encyst as arrested larvae
premunition
parasitological feedback mechanism in which the adult population in the lumen inhibits reactivation and emergence of the arrested larvae
what is the danger of deworming
suddent death of the adult population allowing for arrested larvae to emerge and cause damage
why does resistance develop
too frequent dewormer use
underdosing of dewormer
refugia
portion of population of parasites that eludes the drug at the time of the treatment event that are still susceptible
what concept explains:
The portion of a population of parasites that eludes the dewormer at the time of a
treatment event. Also known as the portion of a worm population that is susceptible to a dewormer
refugia
what concept explains:
The ability of worms in a population to survive treatments that are generally effective against that species of worm.
resistance
what concept explains:
The loss of ________ may result in post-treatment pathology caused by the reactivation of arrested L4s after the elimination of adult worms via a deworming treatment
premunition
what concept explains:
An important biological event in the life cycle of Pasture-borne Nematodes, in which ingested larvae migrate to and may arrest in the wall of the host gut
mucosal migration
what concept explains:
A parasitological feedback mechanism in which the adult population in the lumen inhibits the
reactivation and emergence of the arrested larvae
premunition
what concept explains:
often caused by the overuse or underdosing of a dewormer
resistance
what is the goal of parasite control programs
- minimize the risk of parasitic disease
- delay further development of anthelmintic resistance
how are hosts infected by pasture-borne nematodes
ingest L3s on forage
what are 5 goals when controlling pasture-borne nematode
- promote refugia
- limit pathology
- reduce pasture contamination
- reduce the use of dewormers
- slow resistance
20% of the herd produces what percentage of pasture contamination
80%
In general, _____ are more likely to become heavily infected and seriously affected by parasites
young and naive hosts
what is salvage deworming
treatment to stop clinical pathology
what is selective/tactical deworming
treat hosts with subclinical pathology but not treatment of hosts showing no symptoms
strategic deworming
prevent future infections by reducing pasture contamination