Parasites

Question 1

4 main parasites of intestines

Answer 1

-anoplocephala paranoplocephala, strongylus vulgaris, small strongyles, parascaris equorum

Question 2

how parasites damage hosts

Answer 2

• competition for nutrients
• sucking blood
• tissue destruction
• physical obstruction
• immune mediated reactions
• abnormal migration patterns

Question 3

degree of harm depends on…

Answer 3

pathogenic potential of parasite

• concentration of parasites
• immune status of host
• general health of host

Question 4

cyathostomins or small strongyles

Answer 4

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

Question 5

clinical signs of cyathostomins

Answer 5

diarrhea, dehydration, inappetance, wasting, edema, sometimes death

Question 6

anoplocephala perfoliata tapeworm

Answer 6

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

Question 7

parascaris equorum

Answer 7

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

Question 8

parasite control aims to

Answer 8

-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

Question 9

factors of horse to consider

Answer 9

• susceptibility to infection differs between individuals
• horses <3years are more susceptible
• increasing antihelmintic resistance
• refugia, ability to survive and stay in host, important

Question 10

differing susceptibility

Answer 10

ie small strongyles

-20-30% of adult horses shed 80% of eggs, 90% are small strongyles

Question 11

antihelmintic resistance

Answer 11

• ability for parasite to survive treatments
• resistance is inherited
• once resistant the population cannot lose it, resulting in more resistant parasites

Question 12

refugia

Answer 12

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

Question 13

preventing resistance

Answer 13

• 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

Question 14

drugs used

Answer 14

fenbendazole "panacur"
pyrantel "strongid"
ivermectin "eqvalan"
moxidectin "quest"
praziquantel (mix of the others)

Question 15

do drugs kill larval stages? why is this a problem?

Answer 15

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

Question 16

use praziquantel for…

Answer 16

anoplocehala

Question 17

for parascaris larva use…

Answer 17

ivermectin and moxidectin

Question 18

which parasite has no evidence of resistance in NA

Answer 18

large strongyles

Question 19

tools for effective deworming

Answer 19

• fecal egg counts

- fecal egg count reduction test

Question 20

fecal egg count

Answer 20

• 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

Question 21

limitations of FEC

Answer 21

• 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

Question 22

FECRT

Answer 22

• 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

Question 23

deworming strategies for adults

Answer 23

• 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

Question 24

deworming for foals

Answer 24

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

Question 25

strategies via environment

Answer 25

proper composting of feces

• pasture rotation
• remove feces from pasture