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
scheduled deworming
deworm at regular intervals to eliminate maturing adults (spring and end of grazing season)
what type of deworming is:
A subclinical horse with a FEC* above specified threshold
selective
what type of deworming is:
Planned Deworming v/s the Periparturient Rise
strategic
what type of deworming is:
Host showing severe clinical pathology
salvage
what type of deworming is:
A subclinical goat with a FAMACHA score of D(4)
selective
what type of deworming is:
Calf with intense diarrhea and anorexia
salvage
what type of deworming is:
Has led to overuse of dewormers and resistance.
strategic
what type of deworming is:
Used to promote refugia and delay resistance
selective
what type of deworming is:
Deworming Based on PPP**
strategic
what information does a fecal egg count provide
- identifies hosts with high contamination potential
- end of grazing season to check efficacy of control program
what information does the fecal egg count reduction test provide
- informs about resistance/efficacy
why do you wait 10-14 days to collect a post-treatment fecal
to clear out dead worms/eggs and before new worms repopulate the gut
T/F: there should be treatment only once the FEC has reached a specific threshold
TRUE
what utilizes the McMasters technique
FEC and FECRT
what is used to identify Hosts with High Contamination Potential
FEC
Informs about the presence of Dewormer Resistance
FECRT
When is the best time to check the efficacy of one’s pasture-borne nematode control program?
A. Beginning of Grazing Season
B. Middle of Grazing Season
C. End of Grazing Season
C. end of grazing season
what larval stage is most susceptible to harsh conditions
L1 and L2
describe L3s
retains protective sheath (less susceptible) but cannot feed
what is a larval storm
rainstorm releases large numbers of L3 that have matured in fecal pat, pathology shows up in hosts soon after
what are the treatment methods for pasture management
- removal
- compost
- drag?
Which environmental conditions are most detrimental to the free-living stages (ova, L1s, L2s, L3s) of pasture-borne nematodes?
low humidity and high temperature
The release of large numbers of L3s from fecal pats, which cause pathology in hosts soon after a rainstorm event following a dry period.
larval storms
horizontal migration
across pasture
vertical migration
up grass blades
Which “Treat-&-Move Strategy” is most likely to produce a monoculture population of Resistant Nematodes?
treat & move
Which “Treat-&-Move Strategy” inhibits the development of Refugia?
treat & move
what pasture management:
Requires much fencing for multiple small pastures.
planned intensive grazing
which practice is best to limit contamination of new pasture
a. treat & move
b. move, wait, treat
c. treat, wait, move
c. treat, wait, move
interspecific co-grazing relies on what
host specificity
intraspecific co-grazing relies on what
age-related immunity
ex: cow-calf grazing, forward grazing (fresh pasture grazed by calves first)
what are two different types of pasture maintenance
- strip grazing
- rotational grazing
reactivation of arrested L4s can be caused by
- spring rise (winter stressors)
- periparturient rise (decrease in female host immunity due to pregnancy and lactation)
T/F: dewormers do not affect arrested L4 because they are metabolically inactive
TRUE
