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EQUINE > 7.1.4: Equine GI parasites > Flashcards

7.1.4: Equine GI parasites Flashcards

1
Q

1

A

Small strongyles (a.k.a. cyathostominosis)

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2
Q

2

A

Large strongyles (S. vulgaris, S. endentatus, S. equinus)

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3
Q

3

A

Roundworms (Parascaris equorum)

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4
Q

4

A

Pinworm (Oxyuris equi)

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5
Q

5

A

Tapeworm (Anaplocephala magnum, Anaplocephala perfoliata)

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6
Q
A

Habronemiasis
* Mainly associated with skin sores and occasionally conjunctivitis
* Transmitted by flies
* Adult worms live and reproduce in the stomach
* Those who are deposited in the conjunctiva/in wounds can’t migrate so cause disease locally

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7
Q

Which horses are predisposed to this and when?

A

Habronemiasis
* Affects all ages of horse
* Typically seen in June-September (‘Summer sores’)

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8
Q

What disease do these worms cause in the stomach? How are they diagnosed?

A

Habronemiasis
* Adults in the stomach usually cause no disease
* Occasionally horses mount a response against the worms causing nodules of granulation tissue which also contains eosinophils
* Hard to diagnose on faecal analysis as eggs are very fragile and rupture
* Identify gastric lesions using gastroscopy

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9
Q

Prevention of habronemiasis

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
  • Habronemus spp. will be killed when the horse is wormed for other parasites.
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10
Q

What is this and which horses does it typically cause disease in?

A

Parascaris equorum
* Usually causes disease in horses less than 2 years old
* Immune response is more developed in older animals

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11
Q

Life cycle including reservoirs

A

Parascaris equorum
* Life cycle involves migration through the liver, vena cava, bronchi, trachea
* Eggs are coughed up and swallowed
* Reservoirs = adult horses. They carry small numbers but shed enough eggs to infect foals/youngstock
* Foals are NOT infected in-utero or via milk
* Disease is typically seen in horses <2 years old; older horses develop protective immunity

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12
Q

Clinical signs of Parascaris equorum

A
  • Some of the clinical signs are due to hypersensitivity reactions to the worm
  • Coughing and nasal discharge - may see as an outbreak
  • Poor coat
  • Weight gain
  • Dull
  • Anorexic
  • Occasionally colic inc bowel obstruction
  • Disorders of bone and tendons as the parasites consume lots of Ca, P, Zn, Cu
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13
Q

Treatment of Parascaris equorum

A
  • There is emerging multi-drug resistance to Parascaris equorum
  • Do not rotate drugs - this does NOT prevent resistance, it selects for MDR parasites. Stick to the drugs that work.
  • Use pyrantel
  • Be warned that we may see colic is we treat lots of adult worms with paralytic drugs e.g. avermectins, pyrantel
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14
Q
A

Anoplocephala perfoliate/magna
* Equine tapeworm (cestode)
* Usually affects young horses but can be any age
* These parasites have large suckers that attach to the intestinal mucosa

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15
Q

Clinical signs of Anoplocephala perfoliate/magna

A

Colic
* Ileal impaction - often very painful
* Intusseceptions
* Caecal impactions and motility disorders
* Spasmodic colic
* Diarrhoea
* Functional and physical blockages

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16
Q

Life cycle of Anoplocephala perfoliate/magna including prepatent period

A
  • Egg shedding is irregular; sometimes released from segments in L1 and sometimes after excreted frm horses
  • The eggs released are infective to oribatid mites
  • Mites live on the ground eating plant debris and lichens -> overwinter in the soil
  • Horses infected in spring when they eat grass and therefore mites
  • Prepatent period = 6-10 weeks -> can then shed large numbers of eggs
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17
Q

Diagnosis of Anocephala perfoliate

A
  • ELISA: semi-quantitative serological test. Good for populations but not individuals as lots of false positives.
  • Can be done on blood or saliva.
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18
Q

Treatment of Anocephala perfoliate

A

Drug options
* High dose pyrantel (double the dose required for other worms)
* Praziquantel (treat in autumn/winter)

Other measures:
* Stable horses for 48hrs after worming to prevent increased pasture contamination
* Can’t kill the mites (they are nature’s dustman)

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19
Q

Clinical signs of Strongylus vulgaris

A
  • In adults: protein losing enteropathy and anaemia
  • Colic
  • Diarrhoea
  • Ischaemia -> gut is dying off, requires surgery
  • Can form thrombi at aorto-iliac junction -> this can lead to lameness and poor performance
  • Occasionally can migrate aberrantly and end up in brain, kidneys, lungs, liver, and form granulomas
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20
Q

Which worm causes verminous arteritis?

A

Strongylus vulgaris
Verminous arteritis: an inflammatory process that occurs in the mesenteric artery due to large strongyle larval migration

21
Q

Which wormers is Strongylus vulgaris sensitive to?

A
  • Benzimidazoles and avermectins kill both larvae and adults
  • Pyrantel kills adults only
  • Otherwise, avoid overgrazing (eggs are often on the ground) and pick up faeces regularly
22
Q

True/false: it is best to use worm egg counts to guide worming protocols, including for large strongyles such as Strongylus vulgaris

A

False
* Strongylus vulgaris causes prepatent disease - the disease is caused by migration of larval stage
* There is no correlation between strongyle eggs and luminal worm counts
* It is not appropriate to wait for egg counts and use them to assess disease

23
Q

Which animals are the reservoir for Strongylus vulgaris?

A
  • Asymptomatic horses that shed large numbers of eggs
24
Q

What is the prepatent period for S. endetatus and what are clinical signs of infection?

A

PPP = 11 months
* Causes colic due to liver disease/peritonitis
* This is a hepatoperitoneal strongyle

25
Q

What is the prepatient period for S. equinus and what are the clinical signs of infection?

A

PPP = 9 months
* Mild colic; some association with pancreatic disease and primary diabetes mellitus (both these conditions are v rare in horses)
* S. equinus is a hepatopancreatic strongyle

26
Q
A

S. endentatus/S.equinus

27
Q

What is the prevalence and clinical relevance of cyathostominosis?

A
  • 80% prevalence
  • Currently the most important equine parasitic disease in terms of prevalence and severity of clinical signs seen
  • Cyathostominosis = small strongyles. There are 50 equine species.
28
Q

Encysted hypobiotic larvae of small strongyles are hard to kill. What can we use?

A
  • Moxidectin
  • But kill rates are poor 20-60% and yet this is still the best we have
29
Q

Describe the life cycle of small strongyles (cyathostominosis)

A
  • Larvae emerge in spring, often many at once
  • PPP = 6-14 weeks if no hypobiosis
  • Most larvae are on the pasture in autumn
30
Q

True/false: horses form immunity to cyathostominosis.

A

True
but forming immunity takes a long time and is never complete

31
Q

Describe the two clinical syndromes seen with cyathostominosis

A

Acute larval cyathostominosis
* First syndrome
* Seen in spring
* Due to mucosal damage caused by the emergence of the late L3
* Clinical signs: colic, weight loss, diarrhoea (both acute and chronic), wasting and death (either acute or chronic)

Autumn syndrome
* See when larvae are entering the intestinal wall
* Less common than syndrome in spring
* Clinical signs: colic, diarrhoea due to inflammation

32
Q

Diagnosis of cyathostominosis

A
  • Very difficult as PPP disease
  • Based on history and clinical signs: young animals with poor worming history, recent change
  • May see larvae in faeces/on glove after rectal in acute larval cyathostominosis
  • In future, hope to have ELISA against the larvae; currently we have have an ELISA for IgG antibodies against specific cyathostomin antigens (this can assess the probabilities of total worm burdens but not likelihood of disease)
33
Q

Which horses are predominantly affected by Oxyuris equi ?

A
  • Affects horses of any age
  • This is a disease of stabled horses; eggs don’t survive well outdoors
  • Reservoirs are other infected horses and the immediate environment
34
Q

Clinical signs of Oxyuris equi

A
  • Anal pruritus
  • Skin excoriation
  • ± Myiasis
  • Eggs in the perianal region on exam
35
Q

Diagnosis of Oxyuris equi

A
  • Sellotape test around tail -> put on slide and examine under microscope
36
Q
A

Oxyuris equi

37
Q

Treatment and prevention of Oxyuris equi

A
  • All anthelmintics should be effective; there is some resistance sometimes
  • Anal paste can be applied
  • Can use topical/systemic anti-inflammatories to decrease pruritus and keep area clean with disposable material
  • Good stable hygiene: water troughs, mangers
38
Q

What is our main aim in parasite management?

A
  • Prevent the development of resistance to anthelmintics where possible
  • Maintain parasites low enough to mitigate clinical signs -> achieve this through strategic use of anthelmintics and pasture management
39
Q

True/false: rotating different anthelmintic products is a good idea.

A

False
It is a bad idea! Do not do this and avoid resources >10 years old that tell you to do this.

40
Q

What should you use to treat larval cyathostominosis?

A

Moxidectin

41
Q

What should you use to treat a horse who has recurrent colic due to high Parascaris equorum burden?

A

Pyrantel

42
Q

What should you use to treat a horse who has colic and a high ELISA for Anapolcephala ?

A

Praziquantel
OR
Double the standard dose of pyrantel

43
Q

Describe how you could manage pasture to prevent parasitic disease

A
  • Appropriate stocking
  • Faecal collection - minimum 2x weekly - remember that larvae do not stay in faeces or recognise electric fencing
  • Keep dung heaps separate to grazing area
  • Rotate pastures - esp in hot dry conditions as larvae overwinter in mild winters
  • Grazing with ruminants
44
Q

What is the principle of an in refugia population?

A
  • It would be ideal to only treat horses with high parasite burdens (if only we knew)
  • This would minimise shedding and parasite contamination (10-20% of horses produce 80% of eggs)
  • Not treating all horses would mean a large percentage of parasites were not exposed to the anthelmintic
45
Q

What are some recommendations for how to select which horses to treat and when to do this?

A
  • Must have yard-wide approach
  • Treat if clinical signs
  • FWEC every 8-12 weeks in grazing season; treat if >250epg (give ivermectin or pyrantel)
  • Perform a faecal egg count reduction test ater 14 days to assess efficacy of treatment
  • Treat new arrivals at yard and hold away from turnout for a minimum of 3 days (or ideally until FWEC reduction)
  • For young horses, FWEC required more frequently
46
Q

1

A

Low risk

47
Q

2

A

Moderate risk

48
Q

3

A

High risk

49
Q

Describe which horses to treat and how over the course of a given year, with reference to risk

A

Low risk horses:
* No autumn treatment

Moderate/high risk horses:
* Moxidectin/ivermectin in autumn

Tapeworm
* Do ELISA in spring and autumn
* Treat if high antibody titre
* Treat with pyrantel (2x dose) or praziquantel

EQUINE (59 decks)

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