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Parasitology #2 > Horse-helminths > Flashcards

Horse-helminths Flashcards

1
Q

Drascheia spp. vs. Habronema spp

A

-gastric nematodes
-spirurid stomach
-not in canada
-arthropod transmitted (Stomoxys calcitrans and musca domestica)

Drascheia spp=submucosa
Habronema spp= mucosa

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2
Q

Lifecycle Habronema/Drascheia

A
  1. Larvae ingested (L3) by horse DH
  2. Adults in stomach= no clinical signs
  3. Larvated eggs in manure
  4. Larvae develop in Fly IH (approx 1 week)
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3
Q

Summer sores

A

-Cutaneous habronemiasis
-occurs when worms get into wounds (Habronema/Drascheia)

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4
Q

Diagnosis of Habronema/Drascheia

A

-larvae in skin scraping or biopsy
-adults on gastric lavage/scoping
-not fecal float

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5
Q

Treatment of Habronema/Drascheia

A

ivermectin (macrocyclic lactones

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6
Q

Parascaris spp

A

-includes P. equorum and P. univalens

-large round worms of horses located in small intestines

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7
Q

Epidemiology of Parascaris

A

-primarily patent in foals less than 6mths of age
-occasionally present in adult horses, especially older horses (late teens, 20s)
-worldwide distribution
-pastured and stable animals
-eggs resistant and sticky
-quasi-vertical transmission (mechanical)

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8
Q

Parascaris spp lifecycle

A

PPP: 10-12 weeks
1.Adults in small intestines
2. Eggs with morula in feces
3. eggs with L1,L2 ->L3 (3 weeks)
4.Horse ingests Egg with L3
5. Hepato tracheal migration

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9
Q

Pathogenesis of parascaris

A

-Resp signs, coughing

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10
Q

Strongyloides westeri

A

-small intestinal nematodes
-equine threadworm

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11
Q

Epidemiology of Strongyloides westeri

A

-ainly patent in foals less than 6mths
-worldwide distribution
-warm humid climates (including BC)
-pastures or stabled animals with poor environmental hygiene
-eggs not really resistant

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12
Q

Strongyloides westeri life cycle of young horses

A

PPP:10-14days
1. Adults in small intestines
2. Larvated eggs in feces
3. Homogenic cycle (3 days)
-rhabditiform L1
-filariform L3 reinfect or reproduce with free living
4. Female L3= heterogonic cycle (7-10 days) ingested by horse DH

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13
Q

Strongyloides westeri life cycle older horses

A
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14
Q

Pathogenesis of strongyloides

A
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15
Q

Treatment of strongyloides

A
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16
Q

Large intestinal nematodes of horses

A

-migratory large strongyles
-virtually eradicated worldwide due to anthemintic use
-pasture transmitted

-Strongylus vulgaris= bloodworm
-Strongylus edentatus
-Strongylus equinus

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17
Q

Strongylus vulgaris life cycle

A
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18
Q

Migration sites of Strongylus vulgaris

A

-aorta and cranial mesenteric artery
**leads to Verminous arteritis

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19
Q

Buccal capsule of S. vulgaris

A
20
Q

Strongylus edentatus buccal capsule

A
21
Q

Strongylus edentatus life cycle

A
22
Q

Strongylye equinus buccal capsule

A
23
Q

Strongylus equinus life cycle

A
24
Q

Diagnosis of strongyle species

A

Strongyle type eggs in fecal flotation

25
Q

Pathogenesis of large strongyles

A

Strongylus vulgaris- migration into mesenteric artery and aorta

26
Q

Cyanthostomes

A

-small strongyles
-trichonemes
-large intestinal nematodes
-pasture transmitted

27
Q

Cyathostome buccal capsule

A
28
Q

Cyanthostomes life cycle

A

-ingested during grazing season
-hypobiosis during the winter where they become encysted in mucosa= often leads to colic and death

29
Q

Clinical signs of Cyathostomiasis in equine

A

-emergence of mucosal larvae (rare in canada if not treated with moxidectin)
-diarrhea, weight loss, protein losing enteropathy, edema
-mortality as high as 50%
-can occur in absence of any eggs shed in feces

30
Q

Diagnosis of Cyanthostomiasis

A

-subadult and adult worms in feces

-larval culture from eggs in feces

-thickened walls of large intestine on ultrasound

31
Q

Treatment of Cyanthostomiasis

A

-Egg reappearance Period following treatment varies with product. It is due to mobilization of inhibited larvae
-Moxidectin is only product effective against inhibited larvae

32
Q

Equine nemabiome egg count

A

-does not give a full picture of how sick the horse is
BUT if a horse only has strongylus vulgaris (even if it is a few), it can lead to death

33
Q

Horse anthelmintics

A

-no regulations and anyone can but it
-has lead to widespread resistance

34
Q

Large strongyles resistance

A

No resistance to benzimidazoles, pyrantel, or macrocyclic lactones

35
Q

Resistance of small strongyles

A

-Resistance to benzimidazoles, pyrantel, macrocyclic lactones

36
Q

Parascaris resistance

A

Resistance to Pyrantel and macrocyclic lactones
-no resistance to benzimidazoles

37
Q

How to prevent resistance

A
  1. Determine which horses contribute the most eggs
  2. Leave parasite refugia by using Targeted Selective Treatment (TST)
  3. Monitor drug efficacy (by FEC reduction test)
  4. Max effect and minimize shedding
  5. Use non drug methods to control (pasture and manure management)
38
Q

Which horses produce the most eggs?

A

Overdispersed or clumped distribution of parasite populations
-Smaller portion of the population (minority) are shedding the most amount of eggs

39
Q

Individual fecal egg counts

A

-Test adult horses at least twice a year (spring and fall)

-test at least 9 weeks post treatment (if pyrantel or benzimidazoles) and 12-16 weeks (macrocyclic lactones- ivermectin and moxidectin)

-Use McMaster, and categorize into low, medium and high shedders
OR create a herd specific frequency profile

40
Q

Targeted selective treatment

A

Treat the moderate to high fecal egg counts

Do not treat the low fecal egg counts

**Refugia- the resistant worms still coming from treated horses but still have non resistance worm from the low shedders = dilution

41
Q

Options for TST in a herd of 15 horses

A

Want to maintain refugia

42
Q

Fecal egg count reduction test

A

-test at least 6 horses per farm
-use horses with highest fecal egg counts
-treat highest, then re test in 14 days

43
Q

Calculation for Fecal egg count reduction test

A
44
Q

When to test and treat adult horses in W. Canada?

A

-Test and treat all horses in Fall
>moxidectin to get encysted larval stages of small strongyles and bots
>praziquantel if cestodes

-Test and treat moderate/high shedders in Spring and possibly again in 2-3mths

-Do FEC reduction test at least every 3yrs

45
Q

When to treat horses less than 3 years old

A

-treat up to 4 times per year
Strongyloides- foals at 1-2 weeks old
Parascaris- foals at 2-3mths and 6 mths

-Treat for small strongyles= ivermectin OK in SK
>9-12 mths, then every 3-4mths

-Do FEC reduction test yearly

Parasitology #2 (12 decks)

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