4 main parasites of intestines
-anoplocephala paranoplocephala, strongylus vulgaris, small strongyles, parascaris equorum
how parasites damage hosts
- competition for nutrients
- sucking blood
- tissue destruction
- physical obstruction
- immune mediated reactions
- abnormal migration patterns
degree of harm depends on…
pathogenic potential of parasite
- concentration of parasites
- immune status of host
- general health of host
cyathostomins or small strongyles
one of most common parasites
pre-patent period 2-3 months inside host, eggs come out in feces and ingested by horses
-can infect host after one week in ideal conditions
-mild unless have large numbers
-larvae undergo inhibited development in gut mucosa, remain as third stage larva until spring
-need access to pasture, cause GI disturbance
clinical signs of cyathostomins
diarrhea, dehydration, inappetance, wasting, edema, sometimes death
anoplocephala perfoliata tapeworm
pre-patent period 1-2 months
- immediately infective eggs; develop in host in 2-4 months
- can cause infection colic
- indirect lifecycle, infection occurs in infected mites
- needs pasture
- egg counting difficult due to egg shedding
parascaris equorum
worldwide distribution
- major pathogen in FOALS AND YEARLINGS
- pre-patent period of 10 weeks
- infective in 3 weeks
- infective in confiement and pasture
- deworming can cause acute small intestinal impaction
- can cause poor growth, airway inflammation, cough, and nasal discharge
parasite control aims to
-minimize risk of parasitic disease
-control parasite egg shedding
-maintain effective drugs and avoid resistance development
ultimate goal is to LIMIT parasite infections to keep animals healthy, not to eliminate parasites from individual
factors of horse to consider
- susceptibility to infection differs between individuals
- horses <3years are more susceptible
- increasing antihelmintic resistance
- refugia, ability to survive and stay in host, important
differing susceptibility
ie small strongyles
-20-30% of adult horses shed 80% of eggs, 90% are small strongyles
antihelmintic resistance
- ability for parasite to survive treatments
- resistance is inherited
- once resistant the population cannot lose it, resulting in more resistant parasites
refugia
portion of population that avoid treatment due to being larvae, encysted stages, free-living parasites on pasture, or simply weren’t treated
-they DILUTE the population of resistant worms
preventing resistance
- prevent resistance from developing and reduce accumulation of resistant genes
- fecal egg count reduction test FECRT is only method used for detecting resistance
- fecal egg counts FEC also used for checking parasite loads on horses
drugs used
fenbendazole "panacur" pyrantel "strongid" ivermectin "eqvalan" moxidectin "quest" praziquantel (mix of the others)
do drugs kill larval stages? why is this a problem?
NO; and larval stages can cause most of the disease
- can prevent this by killing worms before pass large number of eggs into the environmen
- only necessary in spring or summer, where conditions are good for egg development
use praziquantel for…
anoplocehala
for parascaris larva use…
ivermectin and moxidectin
which parasite has no evidence of resistance in NA
large strongyles
tools for effective deworming
- fecal egg counts
- fecal egg count reduction test
fecal egg count
- measure amount of eggs of parasite in horse manure
- determine as low or high shedders
- used to evaluate deworming program effecacy
- target drug to parasite, esp in foals
limitations of FEC
- cannot tell the species, or large or small strongyles
- not accurate reflection of some parasites
- does not detect immature or larval stages including migrating large strongyles
- tapeworm egg shedding inaccurately detected
- pinworms rarely shed in feces
FECRT
- used to determine if strongyles or ascarids are resistant to given anthelmintic
steps: collect fecal sample prior to deworming - administer anthelmintic
- collect fecal sample 14 days following
goal: 90-98% reduction
deworming strategies for adults
- treat every horse 1-2 times
- all other treatments target high shedders of strongyles; higher frequency of FEC and treatment
- treat during times with peak transmission (spring and fall) and when refugia present
- treat tapeworms in late fall/winter
- evaluate efficacy of dewormers at minimum every 3 years
deworming for foals
DO NOT USE FEC
=focus on Parascarus, which cause poor growth, colic, airway inflammation and nasal discharge
-2-3 months fenbendazole, note: ivermectin note for foals
-6months/weaning=FEC
9 and 12 months=strongyles and tapeworms
