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Module 16 > Equine Parasites & Parasite-Associated Disease > Flashcards

Equine Parasites & Parasite-Associated Disease Flashcards

1
Q

what are the nematodes in horses (5)

A
  1. parascaris equorum
  2. small and large strongyles
  3. strongyloides westeri
  4. oxyuris equi
  5. dictyocaulus arnfieldi
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2
Q

what are the cestodes

A
  1. anoplocephala perfoliata
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3
Q

what are the arthopods

A

gastrerophilus

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4
Q

what is the lifecycle of nematodes

A
  1. adult parasites produce eggs or L1 in host
  2. eggs hatch L1 and
  3. moult to L2
  4. L3
  5. L4 ingested
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5
Q

which is the largest nematode

A

parascaris equorum

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6
Q

where do parascaris equorum reside in

A

small intestine

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7
Q

what age do parascaris equorum affect

A

foals, weanlings and yearlings

adults develop acquired immunity

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8
Q

how is parascaris equorum diagnosed

A

distinctive eggs in feces

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9
Q

what is the prepatent period of parascaris equorum

A

10 weeks

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10
Q

what is the parascaris equorum lifecycle (4)

A
  1. egg + L3 ingested
  2. hatching of L3 in the stomach and small intestine, penetration of intestinal veins
  3. larvae reach liver via portal vein, migration through liver tissue and penetration of liver veins
  4. larvae reach lung via vena cava and right heart, penetration into lung alveoles and migration via trachea and pharynx to small intestine (moulting to L4 and St5 prior to development into adults
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11
Q

what is the disease parascaris equorum in foal and weanlings

A

larvae can cause tissue damage during migration –> mirgrate through liver (areas of fibrosis)

2-4 weeks after infection migrate through lungs and cause cough

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12
Q

what disease does parascaris equorum cause in adult horses

A

cause ill thrift –> don’t attch to mucosa but compete for nutrients

can cause colic by luminal obstruction –> ascarid impaction, especially post deworming

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13
Q

how is parascaris equorum controlled (3)

A
  1. avoid using same paddocks for nursing mares and foals in successive years
  2. resistence to fenbendazole, ivermectin and pyrantel –> fenbendazole less resistance in UK vs ivermectin
  3. deworm from 1 month of age, treat every 4 weeks, until 6mo old
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14
Q

how is parascaris equorum treated (4)

A
  1. low bulk diet
  2. NGT with liquid paraffin (lubricate)
  3. treat with fenbendazole
  4. repeat FWEC 3 weeks after last dose
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15
Q

which has a faster mode of action between ivermectin, pyrantel and fenbendazole in killing parascaris equorum

A

ivermectin and pyrantel cause quicker worm death than fenbendazole

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16
Q

what is the dosing schedule in treating with fenbendazole in foals and weanlings

A

day 1: 2.5 mg/kg

day 4: 2.5 mg/kg

day 7-11: 10 mg/kg once daily for 5 days

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17
Q

what are the large strongyles (3)

A
  1. strongylus vulgaris
  2. strongylus edentatus
  3. strongylus equinus
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18
Q

where do adult strongylus vulgaris reside

A

in cecum and ventral colon attached to mucosa

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19
Q

how is strongylus vulgaris infection diagnosed

A

eggs easily detected in feces

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20
Q

what is the PPP of strongylus vulgaris

A

6-7 months

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21
Q

what anthelmintics are strongylus vulgaris sensitive to

A

macrocyclic lactone

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22
Q

what disease does strongylus vulgaris cause

A

associated with colic

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23
Q

what is the life cycle of strongylus vulgaris (10)

A
  1. parasitic phase: L3 taken up orally with grass, exsheathment in small intestine
  2. penetration into wall of large intestine
  3. moulting to L4
  4. migration on or in intima of arteries of large intestine
  5. migration to cranial mesenteric artery
  6. moulting to pre adult stage
  7. migration to intestine and peentration of intestinal wall to enter lumen where development to adults is complete
  8. free living phase: thin shelled eggs expelled with feces
  9. development to L1 within the egg
  10. moulting to L2
  11. infective stage L3
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24
Q

how do s. vulgaris develop in the horse

A
  1. L3 penetrate the intestinal wall and moult to L4
  2. migration of L4 into the cranial mesenteric artery
  3. moulting to St5 from 90th day post ingestion
  4. backwards migration from arteries to the gut
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25
Q

how does strongylus vulgaris cause disease

A

migration through mesenteric artieries leads to thrombosis, infarctions and necrosis of the intestine

non-strangulating infarction

surgical colic

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26
Q

how is strongylus vulgaris controlled

A

sensitive to anthelmintics

but possible increased prevelance due to selective deworming strategies

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27
Q

what are the small strongyles

A

cyathostomins

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28
Q

where do cyathostomins reside

A

cecum and large colon

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29
Q

what is the appearance of cyathostomins worms

A

<1.5cm long white to dark red

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30
Q

what do cyathostomins invade

A

mucosal lining

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31
Q

what do cyathostomins form once they invade the mucosal lining

A

encysted larvae

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32
Q

what is the life cycle of cyathostomins (7)

A
  1. eggs shed into feces –> L1, L2, L3
  2. oral uptake of L3
  3. exsheathment through gastric fluids
  4. passage of exsheathed L3 through small intestine
  5. invasion of mucosa/submucosa of colon and cecum
  6. moult to L4
  7. return to intestinal lumen and final moult before development to adult stage
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33
Q

where do the L3 of cyathostomins reside

A

ileum and travel to the cecum

34
Q

where do L4 of cyathostomins reside

A

develop from L3 in the cecum and travel to the ventral colon

35
Q

what disease do larval cyathostomins cause

A

sudden onset diarrhea in late winter/spring

synchronous emergence of L4 from mucosa (potentially large #s)

life threatening colitis/diarrhea

36
Q

at what age is colitis/diarrhea especially common from cyathostomins

A

< 5 years old

37
Q

how is cyathostomins disease treated (4)

A
  1. replace lost fluid and protein (enteral or IV fluids, plasma transfusion/synthetic colloids)
  2. anti-inflamamtories (corticosteroids?)
  3. deworming (moxidectin vs fenbendazole)
  4. supportive care and nursing
38
Q

how is cyathostomins controlled (2)

A
  1. encysted larval burden NOT detected by FWEC
  2. limited # of anthelmintics active against encysted larvae (treat in winter) –> moxidectin or fenbendazole (wide spread resistance)
39
Q

what does strongyloides westeri affect

A

sucking foals

40
Q

what is the PPP of strongyloides westeri

A

8-14 days

41
Q

how is strongyloides westeri transmitted

A

arrested larvae in dam abdominal wall mobilized and excreted in milk

foals infected immediately after birth

42
Q

what does strongyloides westeri cause

A

diarrhea in foals

43
Q

how is strongyloides westeri controlled

A

deworm dam

  1. moxidectin 4 weeks before parturition
  2. ivermectin around time of foaling
44
Q

what is the life cycle of strongyloides westeri

A
  1. ingestion of food
  2. free living L3 embed in ventral tissues of mare then called parasitic L3 which pass in milk to foal
  3. parasitic L3 develop to adults in foals
  4. two molts: L3 to L4 to L5
  5. adult females in small intestine of foal
  6. embryonated eggs (L1 inside) pass in foals feces
  7. L1 hatch
45
Q

what is oxyuris equi also called

A

pinworm

46
Q

where do adult worms of oxyuris equi reside

A

in lumen of colon

47
Q

where do oxyuris equi migrate to

A

gravid female mirgrates to anus, extrude anterior and lays her eggs in clumps

48
Q

what is the PPP of oxyuris equi

A

5 months

49
Q

what do oxyuris equi cause

A

irritation in perianal area –> tail rubbing

50
Q

how is oxyuris equi diagnosed

A

tape strip

51
Q

how is oxyuris equi controlled

A

difficult

scrub environment

washing perianal area can reduce itch

fenbendazole for 5 days or pyrantel

52
Q

what are dictyocaulus arnfieldi

A

lungworms

53
Q

what disease does dictyocaulus arnfieldi cause

A

patent infection in donkeys that rarely produce clinical signs

horses develop severe bronchial inflammatory response

54
Q

how are horses infected with dictyocaulus arnfieldi

A

by co grazing with donkeys

55
Q

how is dictyocaulus arnfieldi diagnosed

A

difiicult to diagnose

56
Q

what are cestodes

A

tapeworms

57
Q

what is the basic lifecycle of cestodes (tapeworms) (7)

A
  1. cysts ingested by final host
  2. adults in S.I
  3. gravid segments shed from worm and pass out in feces
  4. contain eggs which are resistent
  5. ingested by intermediate host
  6. embryo released from egg in IMH
  7. larva settles down and encysts
58
Q

what is the most common cestode

A

anoplocephala perfoliata

59
Q

where do anoplocephala perfoliata reside

A

in cecum

particularly adjacent to ileo-cecal junction

60
Q

what is the intermediate host of anoplocephala perfoliata

A

forage mites (orbiatidae)

61
Q

how is anoplocephala perfoliata diagnosed

A

eggs difficult to detect in feces

serum/saliva ELISA more sensitive

62
Q

what disease is anoplocephala perfoliata assocaited with

A

colic

63
Q

what is the life cycle of anoplocephala perfoliata (6)

A
  1. gravid proglotids filled with eggs are expelled with the feces
  2. eggs are released and taken up by box mites as IMH
  3. infective cysticercoids develop in IMH
  4. following oral uptake of infected mite with grass
  5. cystercircoids are released during digestion of the mite
  6. larvae attatch to intestinal mucosa and develop into adults
64
Q

what type of colic does anoplocephala perfoliata cause (3)

A
  1. spasmodic colic
  2. ileal impactions
  3. intussusception of cecum and colon
65
Q

how is anoplocephala perfoliata controlled (3)

A
  1. forage mites are widespread
  2. FWEC not helpful –> ELSA?
  3. pyrantel/praziquantel in spring and autumn, twice yearly if high ELISA, once yearly if low
66
Q

what are trematodes

A

fasciola hepatica

but rare in horses

may cause liver disease

67
Q

what are gasterophilus species (4)

A
  1. G. intestinalis: cardia of stomach
  2. G. nasalis: pylorus/duodenum
  3. G. hemorrhoidalis: rectum
  4. G. pecorum
68
Q

what are gasterophilus

A

athropod: bot files gast

69
Q

what are gasterophilus intestinalis transmitted

A

eggs laid on legs and hatch on contact with lips (grooming)

70
Q

what diesease does gasterophilus intestinalis cause

A

not generally associated with disease just irritation from flies laying eggs

71
Q

what is the disease that gasterophilus hemorrhoidalis/nasalis cause

A

attached to rectal mucosa and can cause rectal prolapse

72
Q

summarize the intestinal parasites and where they reside

A
73
Q

what parasite(s) resides in the cecum/ileocecal valves

A

a. perfoliata (tapeworm)

74
Q

what parasite(s) resides in the small colon/rectum

A

o. equi

75
Q

what parasite(s) resides in the stomach

A

G. intestinalis (bots)

76
Q

what parasite(s) resides in the small intestine

A
  1. P. equorum - young hroses
  2. S. westeri - foals
77
Q

what parasite(s) resides in the cecum/large colon

A
  1. large strongyles
  2. cyathostomins (small strongyles)
78
Q

what should parasite control strategy combine (3)

A
  1. chemical (anthelmintic dosing)
  2. non-chemical (pasture hygeine)
  3. all horses from grazing group should share same regimen
79
Q

how can pasture management reduce parasites

A
  1. regular removal of manure
  2. rotation grazing or mixed grazing with ruminants
  3. avoid high stocking density/young horses
80
Q

how should deworming be done

A

based on FWEC of all animals 3-4x per year in grazing season

anthelmintic treatment for positive horses (>200 epg)

Module 16 (26 decks)

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