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Y3 Parasitology S2 > Pig Nematodes > Flashcards

Pig Nematodes Flashcards

1
Q

Name 4 indoor and outdoor parasites of pigs

A
  • Acscaris suum
  • Strongyloides ransomi
  • Trichuris suis
  • Oesophagostomum spp
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2
Q

Name 2 outdoor parasites of pigs

A
  • Hyostrongylus rubidus

- Metastrongylus apri

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3
Q

What are some common characteristics of ascarid nematodes?

A
  • Large, white, fleshy worms
  • Direct life cycles (may include a paratenic host)
  • Infective stage = egg containing the L2/L3 (larvated)
  • Eggs highly resistant and long lived
  • Infections usually stimulate strong immunity
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4
Q

Describe Ascaris suum infections in pigs

A
  • Occur mostly in intensive and extensively housed pigs

- Similar to dog and cat Toxocara and Parascaris of horses

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5
Q

Describe Ascaris suum parasites

A
  • Large worms: males up to 25cm, females up 40cm
  • Females produce large numbers of eggs - 200,000 to 1 million/day per female
  • Eggs are thick walled, 70um diameter
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6
Q

Describe the life cycle of Ascaris suum

A
  • Eggs passed in faeces
  • Develop on the ground – temp dependent, ~4 weeks
  • Egg containing infective larvae (L2/L3) ingested
  • Hepato-tracheal/pulmonary migration, via liver to the lungs
  • Coughed up and swallowed
  • Larvae develop in small intestine through L4 – L5 (adult)
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7
Q

What is the paratenic host of Ascaris suum?

A

Earthworm/dung beetle

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8
Q

What is the PPP of Ascaris suum?

A

8 weeks

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9
Q

Describe the pathogenesis of Ascarid suum

A
  • Typically, don’t see a lot of clinical signs with infection
  • Worm causes strong immunity so is typically seen in younger animals
  • Hypersensitivity response to migrating larvae
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10
Q

Describe the two pathological findings of Ascaris suum due to the hypersensitivity response to migrating larvae

A
  • Liver – fibrous reaction ‘milk spot’: can be focal or multifocal. The liver can regenerate and these resolve, so these are indicative of a current infection
  • Lungs: transient pneumonia
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11
Q

What are the effects of Ascaris suum on pigs/economics?

A
  • Adults in small intestine: Poor weight gain and mechanical blockage in SI
  • Major economic costs: reduced weight gain and liver condemnation
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12
Q

How is Ascaris suum diagnosed?

A
  • Abattoir reports: identification of ‘milk spots’
  • Transient respiratory disease
  • Reduced weight gain
  • Patent infections - eggs in faeces
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13
Q

What is the importance of pigs being coprophagic?

A

They eat excrement so be careful when interpreting low FECs

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14
Q

How is Ascaris suum treated?

A
  • Anthelmintics: MLs (injectable, longer meat withdrawal period), BZs (in-feed formulations)
  • Non-anthelmintic control (to try and remove the eggs within the environment): Steam cleaning indoor pens
  • Control more difficult in outdoor units
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15
Q

Which spp of Strongyloides affects pigs?

A

Strongyloides ransomi

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16
Q

Describe the features of a Strongyloides ransomi infection

A
  • Typically affects very young animals

- Good immunity develops after exposure

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17
Q

Describe the features of adult Strongyloides ransomi

A
  • Small - ~6mm
  • Hair-like
  • No ovijectors (cf trichostrongylus)
  • The oesophagus takes up 1/3 of the length of the worm
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18
Q

Describe the eggs of Ascaris suum

A

50-70um

Thick, pitted outer wall

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19
Q

Describe the eggs of Strongyloides ransomi

A

40-50um
thin shelled
embryonated

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20
Q

What are the two life cycles of Strongyloides?

A
  • Parasitic asexual life cycle in pig

- Free-living sexual life cycle in soil & bedding

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21
Q

Describe the parasitic asexual life cycle of Strongyloides

A
  • L1 -> L3 on pasture
  • The L3 can be ingested or can penetrate across the skin (percutaneous infection) -> intestine where they burrow and develop
  • Can also further migrate to the udder: Transmammary infections -> lactogenic transmission
  • Larvae can remain dormant in the udder which infects consecutive litters
  • Only have female worms that reproduce by parthenogenesis
  • The embryo can develop from an unfertilised egg/oocyst (asexual)
  • Eggs are clones of the female adult worm
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22
Q

What is the PPP of the parasitic asexual life cycle of Strongyloides

A

Less than 15 days

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23
Q

Describe the free living sexual life cycle of Strongyloides

A
  • L1 – L3 is on pasture
  • L3 develop into L4 and L5 within the soil to become adults which then produce eggs and continue the free living cycle
  • Male and female adults worms
  • Feed on bacteria in the soil
  • Can get a real build up of parasites
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24
Q

What are the advantages and disadvantages of direct and indirect development?

A

Direct development:
- Rapid production of infective L3 ready to infect new hosts
- No sexual reproduction
Indirect development:
- Advantage of sexual reproduction
- Disadvantage needing to find a mate for sexual reproduction & slower route to produce L3

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25
Q

Which factors trigger the switch from direct to indirect and vice versa?

A

Genetic factors: different species and genotypes respond differently to environmental cues

26
Q

What are the environmental cues for intra-host development?

A

Host immune status, potential for over crowding

27
Q

What are the environmental cues for extra-host development?

A

Temperature, food availability

28
Q

Describe the disease in pigs caused by Strongyloides

A
  • Infection induces strong immunity - older pigs usually do not have clinical signs
  • Piglets: transmammary infection
    Heavy infections - diarrhea, anemia, and emaciation may occur in pigs up to 3 months old; death may occur, usually in piglets <2 weeks of age
29
Q

How is Strongyloides diagnosed?

A
  • Patent infections - eggs in faeces -> collected from rectum (not environment) & cooled to prevent hatching
  • Abattoir reports:
    Adults may be found in scrapings from the intestinal mucosa
    Immature worms - minced tissues using the Baermann technique
30
Q

How are Strongyloides controlled and treated?

A

Anthelmintics - MLs, BZs

Keep environment clean

31
Q

Which worm spp is known as the ‘whip worm’?

A

Trichuris spp

32
Q

Where is Trichuris spp found?

A

In the LI of pigs

33
Q

Describe the eggs of Trichuris spp

A
  • Lemon shaped with mucoid plugs
  • Highly resistant
  • Remain viable for up to 11 years
34
Q

Describe the morphology of adult Trichuris worms

A
  • Very thin head end which is in the mucosa of the LI

- Larger, fatter tail end which is in the lumen of LI

35
Q

Describe the life cycle of Trichuris worms

A
  • Egg development >16℃, 10-12 weeks
  • Infective stage - Egg containing L1
  • L1 – Adult all occurs within the mucosa of the LI
  • Short period of egg-laying period (2–5 weeks)
36
Q

What is the PPP of Trichuris?

A

PPP - 6-8 weeks

37
Q

Describe the disease and its control caused by Trichuris in pigs

A
  • Weight loss in pigs, diarrhoea, unthriftiness
  • Colitis ingrowing pigs not to be confused with Swine Dysentery
  • Resilient to many anthelmintics
  • Heat is effective for killing/removal
38
Q

Describe the adult worms of Oesophagostomum spp

A

2cm long, characteristic cephalic vesicle

Found in the LI

39
Q

Describe the life cycle of Oesophagostomum spp

A
  • Typical strongyle life cycle - direct
  • L3 = infective stage
  • L3-L4 develop in mucosa of the LI, form nodules
  • Adults move into the lumen of the LI
40
Q

What is the PPP of Oesophagostomum?

A

3-6 weeks

41
Q

Describe the pathology of disease caused by Oesophagostomum

A
  • Nodules: intestinal wall may be thickened and necrotic
  • Little damage in mucosa of large intestine by adult worms
  • Prevalence tends to be higher in older animals
42
Q

How is Oesophagostomum diagnosed?

A

Nodules and presence of adult worms at post-mortem

Faecal examination – may require larval culture to differentiate from Hyostrongylus rubidus

43
Q

How is Oesophagostomum treated and controlled?

A

BZs and MLs, good sanitation

44
Q

Which worm is known as the ‘red stomach worm’?

A

Hyostrongylus rubidus

45
Q

Describe adult Hyostrongylus rubidus worms

A
  • 6cm
  • Similar to ostertagia
  • Infect the stomach
46
Q

Describe the life cycle features of Hyostrongylus rubidus

A
  • Direct life cycle - similar to Ostertagia ostertagi
  • PPP: ~3 weeks
  • Hypobiosis (hypobiotic larvae found in older animals)
47
Q

Describe Hyostrongylus rubidus infections

A

Parasitic gastritis

Heavy infections - inappetance, anemia, or weight loss; contribute to “thin sow syndrome”

48
Q

How is Hyostrongylus rubidus diagnosed?

A
  • Faecal examination (patent infections): larval cultures

- Postmortem examination (prepatent infections): adults small

49
Q

How is Hyostrongylus rubidus treated?

A

BZs, MLs (doramectin & ivermectin) – effective against hypobiotic larvae too

50
Q

Which outdoor worm of pigs uses Earthworms as the intermediate host?

A

Metastrongylus apri

51
Q

Describe the life cycle of Metastrongylus apri

A
  • Larvated thick shelled eggs shed in faeces
  • Hatch, L1 infects earthworm
  • L1-L2-L3 in earthworm – true intermediate host
  • L3 survives as long as the earthworm (up to 7 years)
  • Earthworm ingested by pig
  • L3 released in gut, L3-L4 in mesenteric lymph node
  • L4 reaches lung via lymphatics and bloodstream
  • Matures to adult in the lungs
52
Q

Describe the disease of Metastrongylus apri

A
  • Typical in 4-7 month old pigs
  • Catarrhal and eosinophilic bronchiolitis
  • Exacerbates other respiratory disease, e.g. Staphylococcal infections
53
Q

What are the clinical signs of disease of Metastrongylus apri

A
  • Persistent cough, dyspnoea, nasal discharge

- Reduced weight gain and inappetence

54
Q

How is Metastrongylus apri diagnosed?

A
  • Adult worms visible in bronchi during patent phase of infection
  • Faecal examination (fresh faeces), may need to be supplemented with Baermann technique if eggs have hatched
55
Q

How is Metastrongylus apri treated and controlled

A

Anthelmintics - MLs, BZs

Minimising contact with intermediate host

56
Q

Which factors need to be considered when controlling nematodes in pigs

A
  • Longevity of eggs
  • Presence of an intermediate host
  • Indoor or outdoor pigs
  • Young/breeding sows
57
Q

A farmer has reports of liver condemnations in his pigs, back from the abattoir. What might be causing the condemnations, and what can he do about it?

A

Ascaris suum

  • L2 migrates though liver causing an inflammatory reaction that fibroses resulting in diffuse white lesions often called ‘milk spot’. - Control of A. suum can be problematic because the eggs, shed in faeces, commonly in sows who may harbour low levels of infection, build up and contaminate environment.
  • Treatment with in-feed BZ and control by steam clean building between batches of piglets, biosecurity – treat incoming piglets to prevent infection coming onto farm.
  • Easier to control in indoor than outdoor pigs.
58
Q

Why is the life cycle of Strongyloides ransomi unique?

A

Two life cycles: free-living sexual cycle with male and female worms and parasitic asexual cycle with only female worms. Free-living stages feed on bacteria. Parasitic female worms reproduce by parthenogenesis

59
Q

Which parasite forms nodules within the intestinal mucosa?

A

Oesophagostomum spp.

60
Q

Which nematode is resilient to anthelmintic treatment that might affect control?

A

Trichuris suis

61
Q

Name two parasites that could cause respiratory disease in outdoor pigs

A

Ascaris suum and Metastrongylus apri

62
Q

Name two parasites that may cause weight loss in (1) indoor and (2) outdoor pigs.

A

Indoors: Ascaris suum, Trichuris suis.
Outdoors: Ascaris suum, Trichuris suis, Hyostrongylus rubidus.

Y3 Parasitology S2 (13 decks)

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