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Equine > Parasites > Flashcards

Parasites Flashcards

1
Q

How do internal parasites damage a host?

A
  • competition for nutrients
  • sucking blood
  • tissue destruction
  • physical obstruction
  • immune mediated reactions
  • abnormal migration
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2
Q

What does the degree of harm depend on?

A
  • pathological potential of the parasite
  • concentration of parasites
  • immune status of host
  • general health of host
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3
Q

What is the life cycle of cyathostomins or small strongyles?

A

eggs with morula are defecated out of infected horse onto the ground. -> reaches L3 on ground -> ingested by horse -> becomes an adult in the intestine of the horse -> process repeats

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4
Q

What is the time until infective of horse having ingested cyathostomins?

A

1 week in ideal conditions

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5
Q

What are cyathostomins? (characteristics)

A
  • mild pathogens unless in large numbers
  • larvae can undergo inhibited/encysted development in the gut mucosa, remaining as early third-stage larvae and emerging in spring
  • requires access to pastures to spread effectively
  • can cause GI disturbances
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6
Q

What are the clinical signs of a cyathostomin infection?

A

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

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7
Q

What is the life cycle of anoplocephala perfoliata? (tapeworm)

A

egg with hexacanth larvae pooped out (immediately infective) -> Mite ingests egg -> free living mite with cysticercoid -> ingested by horse -> become adults inside horse
repeats

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8
Q

What are the characteristics of anoplocephala perfoliata, or tapeworm?

A
  • indirect life cycle
  • infection is from ingesting infected mites
  • requires access to pastures
  • difficult to diagnose using common egg counting since eggs are passed only intermittently with shedding and proglottids disintegrate
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9
Q

What can a anoplocephala perfoliata cause?

A
  • ileal impaction and spasmodic colic but no evidence in canada
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10
Q

What is the life cycle of Parascaris equorum?

A

egg with morula pooped out -> egg with L1 -> egg with L2 -> ingested by horse -> tracheal mucosa -> adults in intestine
repeats

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11
Q

What are the characteristics of Parascaris equorum?

A
  • can infect horses who are in confinement and pasture

- deworming heavily parasitized foal can cause small acute impaction of intestine

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12
Q

What are the effects of parascaris equorum?

A

risk for small intestinal impactions, ill-thrift and poor growth and migrating larvae can cause signs of airway inflammation, cough and nasal discharge

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13
Q

What horses are most effected by parascaris equorum?

A

foals due to developing immune system

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14
Q

What is parasite control?

A
  1. minimize risk of parasitic disease
  2. to control parasite egg shedding
  3. to maintain efficacious drugs and avoid further development of anthelmintic resistance as much as possible
    NOTE: goal is to LIMIT parasite infections so animals remain healthy and clinical illness does not develop, NOT to eliminate parasites from an individual
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15
Q

What are some new factors to consider with regards to parasite control?

A
  1. individuals differ in their innate susceptibility and therefore the amount of eggs shed
  2. Horses <3 years old are more susceptible and require different treatment strategies
    3, increasing antihelmintic resistance
  3. refugia important
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16
Q

What is resistance?

A

the ability of worms in a population to survive treatments that are generally effective against the same species and stage of infection

17
Q

Is resistance inherited?

A

yes and resistant parasites never loose their resistance

18
Q

What is resistance prevalence related to?

A
  1. selection

2. worms surviving treatment and breeding

19
Q

What is refugia?

A

portion of a population of parasites (or stages of parasites) that escapes selection with the drug at the time of treatment

  • larvae, encysted stages, free-living parasites on pasture, parasites that did not get treated
  • NOT selected for resistance and dilute population of resistant worms
20
Q

What is the only test/method used for detecting resistance?

A

Fecal Egg Count Reduction Test (FECRT

21
Q

What test evaluates parasite loads in horses?

A

Fecal egg count (FEC)

22
Q

What is the parasite control program?

A
  1. to minimize the risk of parasitic disease
  2. to control parasite egg shedding
  3. to maintain efficacious drugs and avoid further development of antithalmintic resistance as much as possible
23
Q

What is the problem with drugs?

A

they kill adults in the lumen of the GIT but not all drugs kill larval stages which cause the most disease

24
Q

How is the Larval stage problem fixed?

A
  • kill worms before they start to pass large number of eggs into the environment
  • treatments only necessary when environmental conditions are conductive to egg and larval development and survival (usually spring and summer)
25
Q

What are the various treatments/drugs used on parasites?

A
  1. Fenbendazole (panacur)
  2. Pyrantel (Strongid)
  3. Ivermectin (Eqvalan)
  4. Moxidectin (Quest)
  5. Praziquantel (Usually mixed with others)
26
Q

What are the most effective drugs?

A

Ivermectin and Moxidectin

27
Q

What are the tools for effective deworming?

A
  1. Fecal Egg Counts

2. Fecal Egg Count Reduction Test

28
Q

What is the Fecal Egg Count?

A
  • measures the amount of eggs of parasites in the horses manure
  • classify into low and high shedders
  • used to evaluate effectiveness of deworming program
29
Q

What are the classifications of Low, Moderate and HIgh shedders based on Strongyle Egg shedding?

A 
Low = 0-200 eggs/gram, 50-70% adult population
Moderate= 200-500eggs/gram, 10-20% adults
High= >500eggs/gram, 20-30% adults
30
Q

What are the limitations of fecal egg count?

A
  • cannot distinguish species of strongyles
  • do not accurately reflect adult strongyle or parascaris burden
  • do not detect immature or larval stages of parasites including migrating large strongyles and ascarids, and/or encysted cyathostomins
  • tapeworm shedding is intermittent
  • pinworms rarely shed in feces
31
Q

What is the Fecal Egg Count Reduction Test?

A
  • used to determine if strongyles and/or ascarides are resistant to a given anthelmintic
32
Q

What are the steps of the Fecal Egg Count Reduction Test?

A
  1. collect a fecal sample prior to deworming
  2. administer the anthelmintic
  3. collect fecal sample 14 days following treatment
    - GOAL= 90-98% reduction in eggs counted
33
Q

What are the deworming strategies for adults?

A
  • treat every horse 1-2 times
  • all other treatments target the high shedders of strongyles. higher frequency of FEC and treatment
  • treat during times of peak transmission (spring/fall_and when refugia present
  • treat tapeworms in fall/winter
  • evaluate efficacy of dewormers at minimum of every 3 years (FERCT)
34
Q

What are the deworming strategies for yearlings/foals?

A
  • do NOT use FEC
  • Focus on Parascarus
  • 2-3 month - fenbendazole (ivermectin not liscensed for foals)
  • 6 months/weaning - FEC
  • 9 and 12 months - strongyles and tapewroms
35
Q

What are some environmental strategies for treating parasites?

A
  • proper composting of feces
  • pasture rotation
  • remove feces from pasture

Equine (9 decks)

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