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MODULE 16 - Alimentary Tract Disease > PARASITOLOGY - Equine Gastrointestinal Parasites > Flashcards

PARASITOLOGY - Equine Gastrointestinal Parasites Flashcards

1
Q

What are the most significant equine nematodes?

A

Parascaris equorum
Large strongyles
Small strongyles
Strongyloides westeri
Oxyuris equi
Dictyocaulus arnfieldi

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2
Q

Describe the lifecycle for parascaris equorum

A
  1. Host ingests infectious L2 larvated eggs
  2. L2 moult into L3 and hatch within the small intestine
  3. L3 penetrate the small intestinal veins and travel to the liver via the hepatic portal vein
  4. L3 travel from the liver through the caudal vena cave to the right side of the heart and to the lungs
  5. L3 penetrate into the alveoli and migrate to the trachea where they are coughed up and swallowed
  6. L3 travel to the small intestine where they moult into L4 and then into adults
  7. Female adult worms produce eggs which are excreted into the faeces
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3
Q

What is the pre-patent period for parascaris equorum?

A

10 weeks

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4
Q

(T/F) Parascaris equorum eggs can persist in the environment

A

TRUE.

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5
Q

Which signalement is affected by parascaris equorum?

A

Parascaris equorum affects young horses such as foals, weanlings and yearlings. Adult horses develop resistance against parascarus equorum

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6
Q

How does parascaris equorum cause colic?

A

Adults parascaris equorum reside in the small intestine where they can cause small intestinal obstruction and colic

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7
Q

How do you diagnose parascaris equorum?

A

You can diagnose parascaris equorum using faecal egg flotation and egg counts. If one young horse is diagnosed, you should treat all surrounding young horses

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8
Q

How do you treat parascaris equorum?

A

Treat the adult parascaris equorum with fenbendazole or pyrantel and treat the larval stages with ivermectin

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9
Q

Which anthelmintic drugs should you avoid using in young horses with a high parascaris equorum worm burden?

A

Pyrantel
Ivermectin

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10
Q

Why should you avoid using pyrantel and ivermectin in young horses with high parascaris equorum worm burdens?

A

Pyrantel and ivermectin both cause rapid paralysis and death of the worms which can cause colic due to the increased risk of small intestinal obstruction

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11
Q

How should you treat young horses with a high parascaris equorum worm burden?

A

Treat with repeated doses of fenbendazole on days 1, 4 and 7 in combination with a low bulk diet and nasogastric liquid paraffin to help lubricate the intestines to improve worm excretion and reduce the risk of obstructions. Repeat the faecal flotation and egg count three weeks after the final dose of fenbendazole to ensure the worms have been excreted

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12
Q

How do you control parascaris equorum?

A
  1. Regular faecal monitoring
  2. Stable and pasture hygiene
  3. Avoid using the same paddocks for nursing mares and foals in successive years as the eggs persist and infect the foals
  4. Do faecal egg count reduction tests (FECRT) to determine if there is any anthelmintic resistance
  5. Regular deworming
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13
Q

Which anthelmintics are parascaris equorum resistant to?

A

Ivermectin

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14
Q

What is the deworming protocol for parascaris equorum?

A

To control parascaris equorum, administer anthelmintics to foals from 1 month old for every 4 weeks until they are 6 months old

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15
Q

What is the most significant species of large strongyles that affects horses?

A

Stongylus vulgaris

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16
Q

Describe the lifecycle for strongylus vulgaris

A
  1. Host ingests infective L3 larvae
  2. L3 penetrate the large intestinal mucosa and moult into L4
  3. L4 migrate via the large intestinal arteries to the cranial mesenteric artery where they moult into pre-adults
  4. Pre-adults migrate to the large intestine where they penetrate the large intestinal mucosa and enter the lumen where they moult into adults
  5. Female adults produce eggs which are excreted into the faeces
  6. L1 develop and moult into L2 and L3 in the environment
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17
Q

Where specifically in the large intestine do adult strongylus vulgaris reside?

A

Lumen of the caecum and ventral colon

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18
Q

What is the pre-patent period for strongylus vulgaris?

A

6 to 7 months

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19
Q

How does strongylus vulgaris cause colic?

A

When strongylus vulgaris L3 larvae migrate through the cranial mesenteric artery, this leads to thrombosis, non-strangulation infarction and large intestinal necrosis which results in colic which requires surgical correction

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20
Q

How do you diagnose strongylus vulgaris?

A

You can diagnose strongylus vulgaris using faecal egg flotation and egg counts

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21
Q

How do you treat strongylus vulgaris?

A

Treat the adult strongylus vulgaris with oxibendazole, fenbendazole or pyrantel. Treat the larval stages with ivermectin or moxidectin

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22
Q

(T/F) Strongylus vulgaris infection is very common in horses in the UK

A

FALSE. Strongylus vulgaris is no longer very common in the UK as it is very sensitive to anthelmintics so has become less prevelant due to routine deworming protocols. However there is a risk of re-emergence due to strategic deworming strategies

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23
Q

What is the most significant species of small strongyles that affects horses?

A

Cyathostomins (red worm)

Cyathostomins are the most prevalant and pathogenic nematodes in horses!!!

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24
Q

Describe the lifecycle of cyathostomins

A
  1. Host ingests infective L3 larvae
  2. L3 penetrate the large intestinal mucosa and moult into L4
  3. L4 migrate back into the large intestinal lumen and moult into adults
  4. Female adults produce eggs which are excreted into the faeces
  5. L1 develop and moult into L2 and L3 in the environment

Or the L3 larvae can encyst in the large intestinal mucosa and undergo arrested development for a period of 1 -2 years and eventually there will be synchronous emergence of L4 larvae into the lumen, damaging the intestinal mucosa

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25
Q

Where specifically in the large intestine do adult cyathostomins reside?

A

Lumen of the caecum and the large colon

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26
Q

Describe the pathogenesis of cyathostomins disease

A

When L3 encyst in the large intestinal mucosa and eventually there will be synchronous emergence of the L4 larvae into the lumen, damaging the intestinal lining which causes swelling, hindering digestion and nutrient uptake resulting in diarrhoea, life-threatening colitis and colic

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27
Q

What can trigger cyathostomins L4 emergence?

A

Synchronous emergence of L4 cyathostomins can be triggered when the adult worms are killed by anthelmintic treatment, which can cause a change in the intestinal environment which prompts the larvae to emerge

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28
Q

When is cyathostomins disease most prevalent?

A

Cyathostomins disease is most prevelant in late winter/spring

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29
Q

How do you treat cyathostomins disease?

A

IV or enteral fluids
Plasma transfusion or synthetic colloids
Corticosteroids
Deworming using moxidectin

30
Q

Why should you administer plasma/synthetic colloids to patients with cyathosyomins disease?

A

Plasma transfusions and synthetic colloids can be used to replenish protein loses as a result of severe diarrhoea

31
Q

Why is moxidectin the anthelmintic of choice when treating cyathostomins disease?

A

Moxidectin targets all stages of the cyathostomins lifecyle, including the larval stages within the large intestinal mucosa

32
Q

(T/F) You can use ivermectin to kill cyathostomin larvae

A

FALSE.

33
Q

How do you control cyathostomins?

A
  1. Control of cyathostomins is challenging due to the encysted larval stage of the lifecycle which will not be detected by faecal eggs counts so it is challenging to monitor for this parasite. However, you can use a serum ELISA which will detect antibodies against the larvae - which is especially useful if the faecal egg count is low but you still suspect cyathostomins based on the clinical history
  2. Deworming protocols with moxidectin
34
Q

Which anthelmintic are cyathostomins resistant to?

A

Fenbendazole

35
Q

(T/F) Strongyloides westeri is very common

A

FALSE. Strongyloides westeri is not very clinically significant

36
Q

Where do adult strongyloides westeri reside?

A

Adult strongyloides westeri reside in the small intestine of nursing foals

37
Q

How do strongyloides westeri enter the small intestine of nursing foals?

A

Strongyloides westeri larvae encyst in the abdominal wall of the dam and will be mobilised and excreted in the milk resulting in transmammary transmission to the nursing foals

38
Q

What is the main clinical sign of strongyloides westeri in nursing foals?

A

Diarrhoea

|Very uncommon cause of dirrhoea in foals

39
Q

How do you prevent strongyloides westeri?

A

Treat the dam with moxidectin 4 weeks prior to parturition

40
Q

What is the other name used for oxyuris westeri?

A

Pinworms

41
Q

(T/F) Oxyuris westeri is very common

A

FALSE. Oxyuris is not very common however it is beginning to become more prevelant due to anthelmintic resistance

42
Q

Where do adult oxyuris equi reside?

A

Adult oxyuris equi reside in the lumen of the colon

43
Q

What are the three main clinical signs of oxyuris equi?

A

Rubbing of the tail
Perianal alopecia
Eggs present in the perianal area

44
Q

Describe the pathogenesis of oxyuris equi

A

Adult oxyuris equi reside in the lumen of the colon. Gravid female oxyuris equi will migrate to the anus and deposit eggs in the perianal area, resulting in itching and perianal alopecia

45
Q

How do you diagnose oxyuris equi?

A

You diagnose oxyuris equi using an acetate tape sample of the perianal area and assessing for eggs under the microscope

46
Q

How do you treat oxyuris equi?

A

Treat oxyuris equi with fenbendazole or pyrantel

47
Q

How do you control oxyuris equi?

A
  1. Oxyuris equi is challenging to control as the eggs become well dispersed within the environment
  2. Clean the environment
  3. Deworming protocol (fenbendazole or pyrantel)
48
Q

Describe the lifecycle of dictyocaulus arnfieldi

A
  1. L3 larvae are ingested by host
  2. L3 larvae penetrate the intestinal mucosa and travel to the mesenteric lymph nodes where they moult into L4 larvae
  3. L4 larvae travel via the blood and lymphatics to the bronchioles where they moult into young adults
  4. Young adults migrate to the bronchi where they moult into mature adults and produce eggs
  5. Eggs are shed in the faeces
  6. L1, L2 and L3 develop in the faeces
49
Q

What is an important history question to ask if you suspect a horse has dictyocaulus arnfieldi?

A

Does you horse live with or has been in contact with any donkeys?

As donkeys are reservoirs for this parasite

50
Q

What are the most significant equine cestode?

A

Anoplocephala perfoliata

51
Q

What are the hosts for anoplocephala perfoliata?

A

Final host: Horse
Intermediate horse: Forage mites

52
Q

Describe the lifecycle of anoplocephala perfoliata

A
  1. Eggs are ingested by forage mites (intermediate hosts) where they develop into cysticercoids
  2. Horses ingest infected mites and the cystircercoids are released when the mites are digested
  3. Cystircercoids attach to the ceacal wall, particularly at the ileo-caecocolic junction where they will develop into adults
  4. Gravid proglottids filled with eggs are expelled within the faeces
53
Q

Where do adult anoplocephala perfoliata reside?

A

Lumen of the ceacum, particularly at the ileocaecocolic junction

54
Q

Describe the pathogenesis of anoplocephala perfoliata

A

Anoplocephala reside at the ileo-caecocolic junction causing inflammation, spastic colic, ileal impactions and even intussusception of the ceacum and colon

55
Q

How do you diagnose anoplocephala perfoliata?

A

Anoplocephala perfoliata is not detected on routine faecal egg counts but a serum or saliva ELISA can be used

56
Q

How do you control anoplocephala peroliata?

A

Deworm with praziquantel in Spring and Autumn

57
Q

What is the most specific species of arthropod in horses?

A

Gasterophilus

58
Q

Where in the gastrointestinal tract is gasterophilus intestinalis found?

A

Gasterophilus intestinalis is found in the lumen of the cardia of the stomach

59
Q

Describe the lifecycle of gasterophilus intestinalis

A
  1. Horses ingest eggs from their fur as they’re grooming
  2. Larvae (bots) reside within the cardia of the stomach
  3. Pupae reside on pasture where they develop into adult flies
  4. Flies lay eggs on the hair of the host
60
Q

(T/F) Gasterophilus intestinalis can cause colic

A

FALSE. Generally gasterophilus intestinalis don’t cause clinical disease, they eggs just cause irritation on the limbs

61
Q

What is the clinical significance of gasterophilus haemorrhoidalis?

A

Gasterophilus haemorrhoidalis larvae (bots) attach to the rectal mucosa and can cause rectal prolapse

62
Q

What are the goals of parasite control?

A

The aim of parasite control is not to eradicate all parasites, it is to limit parasite infections to prevent clinical illness, and to avoid further development of anthelmintic resistance as much as possible

63
Q

What pasture management can be used to control parasites in horses?

A

Poo-picking
Rotational grazing
Mixed grazing with ruminants
Avoid high stocking density

64
Q

What should you be aware of when carrying out mixed grazing between horses and ruminants?

A

Mixed grazing with ruminants increases the risk of liver fluke in horses

65
Q

What is the general anthelmintic protocol for horses?

A

Depending on the climactic conditions, one to two annual anthelmintic treatments using moxidectin and praziquantel should be sufficient. It is important to use a treatment effective against cyathostomins at a time when the larval mucosal burden will be at it’s peak - typically towards the end of grazing season (autumn)

66
Q

What is the general anthelmintic protocol for foals, weanlings and yearlings?

A

During the first year of life, foals should dewormed a minimum of four times. First deworming should occur at 2 to 3 months old, including a benzimidazole to target parascaris equorum. Second deworming should occur just before weaning. At weaning, feacal egg counts are recommended to determine if the worm burderns are primarily strongyles or parascaris equorum, to facilitate the right choice of drug classification. Third and fourth treatments should be considered at around 9 to 12 months old and the treatment should primarily target strongyes and cestodes

67
Q

When should you treat adult horses for parasites other than for regular deworming?

A

Treat adult horses for parasites if they have equal to or more than 200 eggs per gram (epg)

68
Q

When should you treat young (less than 2 years) and geriatric horses for parasites other than for regular deworming?

A

Treat young and geriatric horses for parasites if they have equal to or more than 100 eggs per gram (epg)

69
Q

Which test can be used to assess for anthelmintic resistance?

A

Feacal egg count reduction test (FECRT)

70
Q

What are the limitations of faecal egg counts?

A

Faecal egg counts do not reflect the total adult worm burden or detect the larval or encysted stages of the parasite. Furthermore, cestode and oxyuris equi infections are often missed or underestimated by faecal egg counts

MODULE 16 - Alimentary Tract Disease (7 decks)

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