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Equine Exam 3/Final > Parasites > Flashcards

Parasites Flashcards

1
Q

What is the prepatent period for large strongyles?

A

Ranges from 5.5 to 12 months

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2
Q

What are possible sequelae of large strongyles?

A

L4 larvae migrate through the abdominal blood vessels (cranial mesenteric artery) and cause “verminous arteritis” and thromboembolism.

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3
Q

What is important today about large strongyles?

A

Historically was an important cause of colic

Rarely seen today because of deworming strategies

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4
Q

What do small strongyles do in the GI tract?

A

L3 larvae invade the mucosa of the large colon and become encysted

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5
Q

What clinical signs do small strongyles cause once they leave their encysted stage?

A

Emergence of encysted L4 can cause colic, diarrhea, weight loss, colic, and rough hair coat

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6
Q

What is the prepatent period for small strongyles?

A

Encysted forms may last 2 years or longer

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7
Q

What anthelminthic choices are there for the encysted small strongyles?

A

Fenbendazole (double dose) and moxidection

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8
Q

What do ascarids do to establish themselves in the host?

A

Eggs are very hardy. They migrate through the lungs after about a week causing cough and respiratory disease

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9
Q

What clinical signs do ascarids cause?

A

Only in horses less than 2 years old

Weight loss, ill thrift, impactions in foals

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10
Q

What is the prepatent period for ascarids?

A

10 to 15 weeks

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11
Q

What anthelminthic concerns are there for ascarids?

A

Be very cautious with anthelminthics that paralyze or kill rapidly like moxidectin, ivermectin, and pyrantel. This could lead to impactions. Must be killed SLOWLY.

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12
Q

What is different about diagnosing cestodes as compared to other parasited?

A

Because they shed intermittently, normal fecal floats are unreliable

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13
Q

What is the intermediate host for cestodes?

A

Oribatid mites

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14
Q

What clinical signs do cestodes cause?

A

Adult parasites reside at the ileocecal valve area

Cause colic, impaction, intussusceptions, ill thrift, and weight loss

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15
Q

What anthelminthic choices are there for cestodes?

A

Only praziquantel is effective and approved. A double dose of pyrantel also works.

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16
Q

What is the prepatent period for cestodes?

A

6 to 16 weeks

17
Q

What form of the botfly is in horses?

A

Only the larval form

18
Q

What clinical signs do botfly larvae cause?

A

Potential oral irritation with larval migration but disease due to bots is rare

19
Q

What is the prepatent period for botflys?

A

Remain in the stomach for many months. They pass into the manure, pupate, and emerge as adult flies

20
Q

What anthelminthic choices are there for botflys?

A

Ivermectin or moxidectin

Deworm in the late summer or fall

21
Q

Lets have a DTR with benzimidazoles

A

Example: Fenbendazole

Do not induce rapid paralysis or death

Double dose recommended for treatment of ascarids or encysted cyathostomins (5 day treatment for cyathostomins)

22
Q

Lets have a DTR with tetrahydropyrimidines

A

Example: Pyrantel

Causes an irreversible rigid paralysis

Only treats adult parasites

Double dose can be effective against tapeworm

23
Q

Lets have a DTR with macrocyclic lactones

A

Example: Ivermectin and Moxidectin

Acts on chloride channels to cause flaccid paralysis. Do not use for ascarids.

Can kill migrating parasites, encysted cyathostomin, lice, mites, habronema, draschia, etc.

24
Q

Lets have a DTR with isoquinolones

A

Example: Praziquantel (only type used in horses)

Only effective in tapeworms

25
Q

What are the main goals for a parasite program?

A

A. Minimize the risk of parasitic disease
- Be okay with minimal levels
B. Control parasite egg shedding
C. Maintain efficacious drugs (decrease anthelmintic resistance(

26
Q

What are steps to dealing with parasites?

A
  1. Determine the shedding status of adult horses
    - 20% of the horses in the herd shed about 80% of eggs
    - Horses with a FEC of < 200 EPG are low contaminators
  2. Determine whether foals and weanlings have ascarids and/or ascarids
  3. Evaluate anthelmintic efficacy using FECRT
  4. Evaluate and monitor strongyle egg reappearance period after deworming
27
Q

What is a fecal egg count reduction test?

A

Used to determine if parasites are resistant to an anthelmintic

Collect a sample for FEC prior to and 10-14 days after deworming

Calculate the percent reduction for each horse and then the mean for all horses on the farm as an indicator of farm resistance

28
Q

How must you interpret a FECRT?

A

At the herd or population level and not based on an individual animal. Results will vary on an individual basis.

29
Q

What are the limitations of the fecal egg count testing

A
  1. Does not accurately reflect the total strongyle or roundworm burden
  2. Does not detect larval stages (migrating or encysted)
  3. Tapeworm infections are often missed or underestimated
  4. Pinworms are usually missed
30
Q

General principles for parasite control:
Adult horses

A
  1. One or two annual treatments for strongyles, tapeworms, bots with usually ivermectin or moxidectin with praziquantel
  2. Additional treatments should target the horses with FEC > 200 EPG
  3. Treat mainly during peak transmission like spring and fall
  4. Include praziquantel for tapeworms at least annually if tapeworms are present in the area
31
Q

General principles for parasite control:
Foals and weanlings

A

A. Minimum of four treatments in the first year of life
B. First treatment at 2-3 months with fenbendazole (slow kill so they don’t get an impact ion)
C. Second treatment just before weaning; can base drug choice on FEC
D. Third and fourth treatments at 9-12 months , including praziquantel for tapeworms
E. Yearlings and 2-year-olds should be treated as “high” shedders with 3-4 yearly treatments

32
Q

What are 3 scenarios in which gastrointestinal parasites could be present and causing weight loss, but the quantitative fecal egg count is negative?

A
  1. Tapeworms and intermittent shedding
  2. Encysted stage
  3. Ascarids have a long pre-patent period

Equine Exam 3/Final (5 decks)

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