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Horsies > Gastrointestinal Parasites > Flashcards

Gastrointestinal Parasites Flashcards

1
Q

Are Cyathostomins small or large strongyles?

A

Small strongyles - have the most clinical relevance to illness in adult horses

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2
Q

Name the 3 large strongyles which commonly cause gastrointestinal disease in horses

A

Strongylus vulgaris
Strongylus equinus
Strongylus edentatus

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3
Q

What is the scientific name for the Equine Pinworm?

A

Oxyuris equi

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4
Q

Name a vector-borne equine parasite which lives in the stomach

A

Habronema and Draschia spp are vector-borne parasites using muscid flies as intermediate hosts
Adult parasites establish in the stomach upon ingestion of larvae deposited by flies around the mouth or by ingestion of dead flies
Within the stomach, parasites become adults in about 8 weeks

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5
Q

What is the scientific name for the equine roundworm?

A

Parascaris equorum

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6
Q

What are the scientific names of the 3 species of equine tapeworm?

A

Anoplocephala perfoliate
Anoplocephala magna
Anoplocephaloides mammillana

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7
Q

You are looking at a small, red worm which has come from a horse. Which worm is it likely to be?

A

Small strongyle - can also be white
Most common in the large intestine and mostly cause diarrhoea from hypoalbuminaemia, colic, weight loss, severe SIRS and death

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8
Q

You are looking at a medium sized collection of worms which are red and white. What species are they likely to be?

A

Large strongyles
S. vulgaris
S. edentatus
S. equinus

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9
Q

Which equine worms cause blood vessel wall damage, haemorrhage and infarction?

A

S. vulgaris (and other large strongyles)

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10
Q

Which equine worms cause coughing?

A

Round worms - Parascaris equorum

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11
Q

Which equine worms cause pruritis around the perineal region?

A

Pinworms - Oxyuris equi

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12
Q

You are looking at large worms up to 10cm which are fat and white. What worms are they likely to be?

A

Round worms - Parascaris equorum

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13
Q

Which worms are most normally found in the equine small intestine?

A

Round worms (Parascaris equorum) and Tapeworms (Anaplocephala magnum)
Strongyles found in the large intestine

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14
Q

Which equine worm is found in the ileocaecal area?

A

Tapeworms - Anaplocephala perfoliata

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15
Q

Describe the gross appearance of a pinworm (Oxyuris equi)

A

Up to 5cm, white, pointy tail like a beansprout

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16
Q

Describe the gross appearance of Anaplocephala magnum and perfoliata worms

A

Tapeworms - small, flat and white

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17
Q

Which equine gastrointestinal worms are most likely to cause colic?

A

Tapeworms - Anaplocephala magnum and perfoliata

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18
Q

You are doing a clinical exam of a horse in June and notice he has skin sores on his muzzle and conjunctivitis. Which gastrointestinal worm is most likely to be involved?

A

Habronemiasis
Caused in part by the larvae of the spirurid stomach worms in the genera Draschia and Habronema
If deposited in the conjunctiva or in wounds they can’t migrate, so cause local disease

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19
Q

Habronemiasis is caused by Habronema larvae. Where do the adults live?

A

In the equine stomach - mostly cause no disease, but occasionally horses mount a response against the worms, causing nodules of granulation tissue which also contain eosinophils.

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20
Q

True or False?
Faecal analysis is the best way to diagnose Habronemiasis?

A

False - eggs are very fragile and rupture
Can identify gastric lesions using gastroscopy

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21
Q

A client wants to know how to reduce the risk of Habronemiasis for her horses. What advice do you give?

A

Good fly control and muck heap management
Frequent replacement of bedding
Collection/Removal of droppings in paddocks
Cover wounds and treat ocular diseases causing ocular discharge
Keep general parasite control up to date as will be killed by most dewormers (not so much avermectins and benzimidazoles)

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22
Q

True or False?
Parascaris equorum has a lifecycle almost identical to Ascaris suum

A

True - both are ascarids

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23
Q

Is Parascaris equorum (round worm) more likely to cause disease in young or old horses?

A

Normally causes disease in horses under 2 - immune responses more developed in older animals.
Equine specific worm

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24
Q

What is the largest worm seen in horses?

A

Parascaris equorum - up to 10cm in length, cream and round

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25
Q

What is the becoming the most important equine gastrointestinal parasite and why?

A

Parascaris equorum - emerging resistance

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26
Q

Describe the lifecycle of Parascaris equorum

A

Horse ingests 2nd stage larvae on pasture
Larvae migrate via the small intestine through the liver, vena cava, alveoli, bronchi and trachea
Larvae then coughed up and swallowed
Adults live and reproduce in the small intestine
Eggs and sometimes adults found in faeces

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27
Q

A client is worried about spread of Parascaris equorum to her 2 week old foal. What do you tell her about spread?

A

Foals aren’t infected in utero or via milk
Reservoirs are adult horses - small numbers but shed enough eggs in faeces to infect foals/young stock

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28
Q

What are the clinical signs of Parascaris equorum?

A

Coughing and nasal discharge when larvae are in the lungs
Some of the coughing is due to hypersensitivity reactions to the worms
Poor coat and weight gain
Dull, anorexic
Occasional colicing, including bowel obstruction
Disorders of bone and tendons, as the parasites consume lots of Ca, P, Zn and Cu
Diagnosis can be difficult - very distinct eggs when present
Often mini outbreaks on farms

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29
Q

You have diagnosed a horse with Parascaris equorum. Which wormer will you prescribe?

A

Pyrantel

Multi-drug resistance to avermecting (only ascarid with MDR, which is likely due to treatment regimes)
Drug rotation selects for MDR parasites, so stick to drugs which work
Can see colic if you treat with paralytic drugs (avermectins and pyrantel) and there are lots of adults

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30
Q

When is Anoplocephala perfoliata/magna disease most commonly seen in horses?

A

Equine tapeworm - cestodes
Disease usually seen in young horses but can be any age

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31
Q

Do equine tapeworms (Anoplocephala perfoliata/magna) use hooks or suckers to attach to intestinal mucosa?

A

Large suckers

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32
Q

Which types of colic can Anoplocephala infections cause?

A

Ileal impactions - often very painful
Intussusceptions
Caecal impactions and motility disorders
Spasmodic (gas) colic
Functional and physical blockages

Also diarrhoea

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33
Q

What is the lifecycle of Anoplocephala perfoliata, the equine tapeworm?

A

A. perfoliata eggs are ingested by Orbatid mites
Eggs develop into larvae inside the mites
Infected Oribatid (Forage) mites on grass are ingested by the horse
A. perfoliata eggs are released and adults develop in the caecum
Adults shed mature segments containing eggs in the faeces
Segements break up and release eggs onto pasture

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34
Q

Where do Orbatid mites live (involved in A. perfoliata life cycle)?

A

On the ground, eating plant debris and lichens
Overwinter in the soil
Horses are infected in Spring when they ingest the mites

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35
Q

What is the prepatent period of A. perfoliata in horses?

A

6-10 weeks
Shed large numbers of eggs

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36
Q

What time of year is disease from tapeworms (Anoplocephala perfoliata) most commonly seen?

A

October and November
Infected in Spring when the mites proliferate
Overwinters to some extent in horses, but overwintering Oribatid mites are just as/more important

37
Q

How could you test for Anoplocephala perfoliata in a group of horses?

A

ELISA from serology - antibody tests so are historic and so false positives can occur = not good for individuals
Can be run from blood or saliva
Only about 25% of horses need treatment
Faecal tests aren’t reliable

38
Q

Which 2 drugs are effective at treating Anoplocephala perfoliata infections?

A

High dose of pyrantel (double dose compared to other worms)
Praziquantel - treat in Autumn/Winter
Praziquantel is the best treatment

39
Q

How can you prevent Anoplocephala perfoliata infections in horses?

A

Stable horses for 48 hours after worming to reduce pasture contamination
Can’t kill Oribatid mites as these are nature’s dustmen

40
Q

Which equine gastrointestinal parasite causes verminous arteritis?

A

Strongylus vulgaris - most clinically important large strongyle
Prevalence has fallen since the use of ivermectin wormers

41
Q

True or False?
Horses which have previously been infected by Strongylus vulgaris don’t ever have full immunity against re-infection

A

True - get some immunity but never enough to stop re-infection
Disease often most severe in young/underexposed animals

42
Q

What are the main reservoirs of Strongylus vulgaris infections?

A

Asymptomatic horses which shed large numbers of eggs

43
Q

You suspect a client’s 1 year old horse to be infected with Strongylus vulgaris. How can you confirm your diagnosis?

A

Pre-patent disease where the disease is caused by larval stages
Might be able to feel thrombi when performing a rectal examination

Faecal analysis isn’t always useful and doesn’t differentiate from other Strongyle eggs
No correlation between Strongyle egg counts and luminal worm counts
Unsure whether worm burden correlates with disease

44
Q

What time of year are Strongylus vulgaris most commonly found in equine arteries?

A

Autumn and Winter - high pasture numbers in Spring/Summer

45
Q

What are the most common clinical signs of disease due to Strongylus vulgaris infection?

A

Protein-losing enteropathy
Anaemia
Colic
Diarrhoea
Anorexia
Ischaemic, dying gut (need surgery for resection, SIRS)
Lameness, often associated with exercise and poor performance (thrombi at aorto-iliac junction)

46
Q

Strongylus vulgaris infections can cause granulomas. Where would these normally be found?

A

In the brain, kidneys, lungs and liver if abnormal larval migration occurs

47
Q

You have diagnosed a horse with Strongylus vulgaris infection. Which anthelmintic is most appropriate to give?

A

Benzimidazoles and avermecting kill larvae and adults
Pyrantel only kills adults

All drug groups are still ok to use, but identifying which horses need treatment is the same for small atrongyles

48
Q

What are the 2 main ways horse owners can prevent Strongylus vulgaris infections in their horses?

A

Pick up faeces regularly
Avoid overgrazing - eggs often on the ground

49
Q

Other than Strongylus vulgaris, name 2 Large Strongyles which are found in horses

A

Strongylus edentatus
Strongylus equinus
Less significant than S. vulgaris, but can still cause some forms of clinical disease

50
Q

True or False?
S. equinus is a hepatoperitoneal Strongyle

A

False
S. equinus is a hepatopancreatis Strongyle
S. edentatus is a hepatoperitoneal Strongyle

51
Q

What are the prepatent periods of Strongylus edentatus and Strongylus equinus?

A

Strongylus edentatus - 11 months
Strongulus equinus - 9 months

52
Q

Out of Strongylus vulgaris, Strongylus edentatus and Strongylus equinus, which doesn’t enter equine blood vessels? What is the significance of that?

A

Strongylus equinus - less likely to cause infarction and mesenteric disease than Strongylus vulgaris and Strongylus edentatus

53
Q

What clinical signs do you see in Strongylus edentatus and Strongylus equinus infections?

A

Strongylus edentatus - colic due to liver disease or peritonitis
Strongylus equinus - mild colic (extremely rarely pancreatic disease and primary diabetes mellitus)

54
Q

How can you diagnose infections of Strongylus edentatus and Strongylus equinus?

A

As for Strongylus vulgaris - feel for thrombi on rectal examination, faecal analysis (can’t differentiate between Strongyle species)

55
Q

What is the most important equine parasitic disease in terms of prevalence and clinical sign severity?

A

Cyathostominosis - causes severe, acute diarrhoea and colic, chronic diarrhoea and death

56
Q

Is Cyathostominosis caused by small or large strongyles?

A

Small strongyles - 50 different species of equine small strongyles

57
Q

True or False?
Most anthelmintics used to treat Cyathostomins target the larvae

A

False - larvae and encysted and hypobiotic, so are largely unaffected by anthelmintics

58
Q

What percentage of Cyathostomin larvae are hypobiotic?

A

50% of larvae are hypobiotic
Total Cyathostomin population made up of 10% adults and 90% larvae

59
Q

You have diagnosed a 3 year old horse with Acute Larval Cyathostominosis. What is the most appropriate treatment plan?

A

Larvicidal anthelmintic - single dose of moxidectin
Supportive care - fluids, acid-base correction and nutrition

60
Q

What is the prepatent period of Cyathostomins?

A

6-11 weeks if no hypobiosis

61
Q

When are most Cyathostomin larvae found on pasture?

A

Autumn

62
Q

Which age group of horses are most likely to have high burdens of cyathostomins?

A

Young adult horses - rarely in foals and older horses develop immunity
Immunity takes a long time to come and is nerve complete

63
Q

Is it easy or difficult to diagnose Cyathostominosis? Why?

A

Difficult as is a prepatent disease caused by synchronous emergence of larvae into the GIT lumen

64
Q

What diagnostic tests can you do to diagnose Cyathostominosis in horses?

A

Might see larvae in faeces or on glove after a rectal examination in horses with acute larval cyathostominosis
Can do an ELISA for IgG antibodies against specific cyathostomin antigens, but this looks at the total worm burdens and not clinical disease

Diagnosis mostly from history and clinical signs

65
Q

What are the 2 presentations of Cyathostominosis in horses?

A

Acute Larval Cyathostominosis - due to mucosal damage caused by the emergence of late L3; seen in Spring
Autumn Syndrome - due to larvae entering the intestinal wall; seen in Autumn

66
Q

What are the clinical signs of Acute Larval Cyathostominosis and Autumn Syndrome?

A

Acute Larval Cyathostominosis:
- Colic
- Weight loss
- Diarrhoea (acute and chronic, sometimes haemorrhagic)
- Wasting and death (bacteraemia, SIRS, oedema from hypoalbuminaemia)

Autumn Syndrome:
- Colic
- Diarrhoea due to inflammation

67
Q

Which age group of horses is most likely to be affected by Oxyuris equi?

A

Any age of horse - equine pinworm

68
Q

True or False?
Oxyuris equi infections are most commonly seen in stabled horses as eggs don’t survive well outdoors

A

True
Reservoirs are other infected horses and the immediate environment

69
Q

What are the most common clinical signs of Oxyuris equi infection?

A

Anal pruritis
Skin excoriation and/or myiasis in the anal region

70
Q

What diagnostic tests can you do to diagnose Oxyuris equi?

A

Sellotape test - put on a slide and examine under the microscope

71
Q

You have diagnosed a horse with Oxyuris equi. What is the most appropriate anthelmintic to use?

A

All anthelmintics should be effective (some resistance)
Anal application as a paste

72
Q

Other than giving anthelmintics, how else can you treat horses with Oxyuris equi infections?

A

Topical or systemic anti-inflammatories to decrease pruritis
Keep affected area clean with disposable material
Good stable hygiene (water troughs, mangers, etc.)

73
Q

Which equine gastrointestinal parasite has widespread resistance to fenbendazole?

A

Cyathostomes (Small Strongyles)

74
Q

True or False?
Large Strongyles aren’t generally resistant to ivermectin, moxidectin, fenbendazole or pyrantel

A

True

75
Q

Ascarids don’t have widespread resistance to which 2 of the following anthelmintics:
- Fenbendazole
- Moxidectin
- Pyrantel
- Ivermectin

A

Fenbendazole (anecdotal resistance)
Pyrantel (few published cases of resistance in the USA)

76
Q

You have done gastrointestinal parasite testing on a herd of 10 horses which are out at pasture together. 2 have clinical signs of disease, 3 are over 15 years old and the other 5 are under 2 years old. Which do you treat?

A

Only treat animals with clinical signs of disease

77
Q

You have diagnosed a 3 year old mare with larval cyathostominosis and a 2 year old gelding with Parascaris equorum. Both horses belong to the same client. What anthelmintic(s) will you use?

A

Larval cyathostominosis - moxidectin
Acute or chronic diarrhoea

Parascaris equorum - pyrantel
Younstock with ill thrift, dull coats and poor growth rates, or severe colic with physical small intestinal production

78
Q

You are treating a horse with recurrent colic and a high ELISA for Anaplocephala. What anthelmintic would be most appropriate?

A

Praziquantel
Or a double dose of pyrantel, but praziquantel is the best option

79
Q

True or False?
Rotation of anthelmintic classes helps prevent multi-drug resistance in parasites

A

False - selects for MDR, as does treating all horses

80
Q

What is the main goal of treatment and prevention of Cyathostominosis in horses?

A

Maintain parasite burdens low enough to mitigate clinical signs = strategic use of anthelmintics and pasture management

81
Q

How can clients manage pastures to minimalise Cyathostomin burdens?

A

Appropriate stocking
Faecal collection - must and at least twice weekly (larvae don’t stay in faeces)
Separate dung heaps from grazing areas
Pasture rotation - best in hot, dry conditions as larvae overwinter in mild winters
Pasture rest
Grazing with ruminants

82
Q

A horse has a faecal WEC of 180epg Cyathostomins. Does it need treating with anthelmintics?

A

No - only if over 250epg (based on testing every 8-12 weeks throughout the grazing seasons. Treat with ivermectin or pyrantel.

83
Q

What should you always do after giving anthelmintics to a horse with Cyathostominosis?

A

Perform a faecal egg count test after 14 days to assess efficacy of treatment (need to do one before treatment as well)

84
Q

You have a new horse arriving at the yard. You have been working on reducing the incidence of Cyathostominosis in the horses already there. What control measures will you put in place to ensure the new horse doesn’t pose a risk to those currently there?

A

Treat all new arrivals and hold away from turn out for a minimum of 3 days (or ideally until a FWEC reduction)
WEC counts required every month for young horses

85
Q

True or False?
Horses over 15 years of age are more at risk of parasitic infection than those 5-15 years old

A

True

86
Q

You are overseeing a yard which grazes 15 horses on one large field year round. All of the horses are 5-15 years old, and have repeated cohort negative WEC and tapeworm antibody levels. Faecal collection occurs daily, the population is stable and there is no history of colic. What anthelmintic controls can you put in place?

A

This is a low risk group.
No Autumn treatment, but do a tapeworm ELISA in Spring and Autumn to maintain levels

87
Q

You are overseeing a yard which grazes 15 horses on one large field all year round. Most of the horses have high WEC and tapeworm antibody levels, and there is no faecal collection. The horses are mostly 2-3 years old and there is frequent population change with no quarantine requirements. 3 horses have had colic within the last 6 months. Anthelmintic resistance has documented. What parasite controls can you put in place?

A

This is a high risk group (moderate risk treated similarly)
Moxidectin or ivermectin in Autumn to get the early L3 larvae of cyathostomins
Tapeworm ELISA in Spring and Autumn and treat high titres with pyrantel or praziquantel

Other GI parasites can be controlled with measures used to control Cyathostomins

88
Q

True or False?
A drop in adult Cyathostomin luminal numbers can result in an increase in hypobiotic larvae activation

A

True

Horsies (8 decks)

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