Parasites (Camila) Flashcards
what are the 2 disease syndromes we worry about with gastrointestinal nematodes?
haemonchosis and parasitic gastroenteritis (PGE)
what does each line refer to?
black: eggs in ewe feces
blue: eggs in lamb feces
red: infective L3 on pasture
what are the 2 sources of infective L3?
on pasture from previous grazing and from eggs deposited by animals on the pasture
do some ovine parasitic nematode larvae over the winter in western canada?
some do YES! especially teladorsagia and trichostrongylus! (less so haemonchus)
_____ is needed to build up a picture of pasture contamination and help inform grazing management
regular monitoring with fecal egg counts
how long does it take for infective larvae to appear on a pasture?
as little as 1 week for haemonchus under the best conditions, or as much as 1 month or longer in worse conditions. it tends to happen faster in mid summer compared to spring or fall.
true or false: it is a good idea to alternate sheep and goats on a pasture to control GIN?
FALSE!
what are the two main categories of antihelmentic drugs?
fenbendazole, albendazole (benzimidazoles)
ivermectin (macrocyclic lacton)
BOTH have lots of resistance
what is closantel used for?
this is a drug newly lisenced in canada and it has narrow spectrum for haemonchus only, and resistance to it is likely rare
what route of drug is preferred for antihelmentics?
oral dosing>injectable>pour on
true or false: recipe based approaches are preferred to prevent parasitic disease in sheep
false! they are not sustainable and not effective, they are BAD practice
instead of recipe based approaches for parasite treatment, what are better alternatives
only treat animals that need it when they need it
use evidence based approaches that include monitoring of parasite burdens
assess drug efficacy and dose correctly: based on heaviest animal (goats need higher doses)
list some tips for good antihelmentic drug use
minimize doses;only treat when needed
always use full dose; do not under dose
fo fecal egg counts every 2 weeks to check if drugs are working
use targeted selective treament, especially when refugia is low
annual rotation of the drug doesn’t do anything!
explain the concept of refugia
the portion of parasite population not exposed to drug treatment is said to be in refugia, so the more refugia, the less selection pressure by drug treatment
in order for refugia to be high, you should treat when?
when there are many larvae on pasture and only treat SOME animals, not all! aim to treat no more than 1/3 the flock
how do you decide who to treat with antihelmentics?
haemonchus: clinical anemia–>treat 4s and 5s, sometimes 3s depending on situtation, can also use fecal egg count as adjunct
teladorsagia or trichostrongyles: condition scoring for ewes, growth rate for lambs, diarrhea assessment (DAG score)
what are 3 important things to remember about ovine coccidiosis?
some species are pathogenic and some are not
they all live in different parts of the GI tract
they are highly host specific
true or false: ovine coccidiosis can occur indoors
true! both indoor and outdoor
what age is commonly affected with coccidiosis?
3 weeks to 3 months
why are the oocysts such a problem in coccidiosis?
they are very resistant in the environment and can survive months up to a year and can survive freezing!!
what are some risk factors for coccidiosis in sheep?
high stocking density, poor hygeine, moisture, stress, other diseases, poor nutrition, (shipping or relocation, shearing, other parasites, etc)
what is unique about anti coccidial drugs?
they act at different parts of the coccidia life cycle
drugs that act on early stages: only useful for prevention and doesn’t allow any immunity to develop
drugs that act on later stages: useful for treatment and prevention and allow immunity to develop
what is the best anti coccidia drug
Toltrazuril (single oral dose) or Amprolium (in water 5 days)
how is treating coccidia different than treating gastrointestinal nematodes?
coccidia treatment: should treat all animals in a group not just those affected
remove animals from contaminated environment
if any are severely sick separate them to treat them
