Pig Nematodes Flashcards
Name 4 indoor and outdoor parasites of pigs
- Acscaris suum
- Strongyloides ransomi
- Trichuris suis
- Oesophagostomum spp
Name 2 outdoor parasites of pigs
- Hyostrongylus rubidus
- Metastrongylus apri
What are some common characteristics of ascarid nematodes?
- 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
Describe Ascaris suum infections in pigs
- Occur mostly in intensive and extensively housed pigs
- Similar to dog and cat Toxocara and Parascaris of horses
Describe Ascaris suum parasites
- 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
Describe the life cycle of Ascaris suum
- 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)
What is the paratenic host of Ascaris suum?
Earthworm/dung beetle
What is the PPP of Ascaris suum?
8 weeks
Describe the pathogenesis of Ascarid suum
- 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
Describe the two pathological findings of Ascaris suum due to the hypersensitivity response to migrating larvae
- 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
What are the effects of Ascaris suum on pigs/economics?
- Adults in small intestine: Poor weight gain and mechanical blockage in SI
- Major economic costs: reduced weight gain and liver condemnation
How is Ascaris suum diagnosed?
- Abattoir reports: identification of ‘milk spots’
- Transient respiratory disease
- Reduced weight gain
- Patent infections - eggs in faeces
What is the importance of pigs being coprophagic?
They eat excrement so be careful when interpreting low FECs
How is Ascaris suum treated?
- 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
Which spp of Strongyloides affects pigs?
Strongyloides ransomi
Describe the features of a Strongyloides ransomi infection
- Typically affects very young animals
- Good immunity develops after exposure
Describe the features of adult Strongyloides ransomi
- Small - ~6mm
- Hair-like
- No ovijectors (cf trichostrongylus)
- The oesophagus takes up 1/3 of the length of the worm
Describe the eggs of Ascaris suum
50-70um
Thick, pitted outer wall
Describe the eggs of Strongyloides ransomi
40-50um
thin shelled
embryonated
What are the two life cycles of Strongyloides?
- Parasitic asexual life cycle in pig
- Free-living sexual life cycle in soil & bedding
Describe the parasitic asexual life cycle of Strongyloides
- 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
What is the PPP of the parasitic asexual life cycle of Strongyloides
Less than 15 days
Describe the free living sexual life cycle of Strongyloides
- 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
What are the advantages and disadvantages of direct and indirect development?
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
Which factors trigger the switch from direct to indirect and vice versa?
Genetic factors: different species and genotypes respond differently to environmental cues
What are the environmental cues for intra-host development?
Host immune status, potential for over crowding
What are the environmental cues for extra-host development?
Temperature, food availability
Describe the disease in pigs caused by Strongyloides
- 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
How is Strongyloides diagnosed?
- 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
How are Strongyloides controlled and treated?
Anthelmintics - MLs, BZs
Keep environment clean
Which worm spp is known as the ‘whip worm’?
Trichuris spp
Where is Trichuris spp found?
In the LI of pigs
Describe the eggs of Trichuris spp
- Lemon shaped with mucoid plugs
- Highly resistant
- Remain viable for up to 11 years
Describe the morphology of adult Trichuris worms
- Very thin head end which is in the mucosa of the LI
- Larger, fatter tail end which is in the lumen of LI
Describe the life cycle of Trichuris worms
- 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)
What is the PPP of Trichuris?
PPP - 6-8 weeks
Describe the disease and its control caused by Trichuris in pigs
- 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
Describe the adult worms of Oesophagostomum spp
2cm long, characteristic cephalic vesicle
Found in the LI
Describe the life cycle of Oesophagostomum spp
- 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
What is the PPP of Oesophagostomum?
3-6 weeks
Describe the pathology of disease caused by Oesophagostomum
- 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
How is Oesophagostomum diagnosed?
Nodules and presence of adult worms at post-mortem
Faecal examination – may require larval culture to differentiate from Hyostrongylus rubidus
How is Oesophagostomum treated and controlled?
BZs and MLs, good sanitation
Which worm is known as the ‘red stomach worm’?
Hyostrongylus rubidus
Describe adult Hyostrongylus rubidus worms
- 6cm
- Similar to ostertagia
- Infect the stomach
Describe the life cycle features of Hyostrongylus rubidus
- Direct life cycle - similar to Ostertagia ostertagi
- PPP: ~3 weeks
- Hypobiosis (hypobiotic larvae found in older animals)
Describe Hyostrongylus rubidus infections
Parasitic gastritis
Heavy infections - inappetance, anemia, or weight loss; contribute to “thin sow syndrome”
How is Hyostrongylus rubidus diagnosed?
- Faecal examination (patent infections): larval cultures
- Postmortem examination (prepatent infections): adults small
How is Hyostrongylus rubidus treated?
BZs, MLs (doramectin & ivermectin) – effective against hypobiotic larvae too
Which outdoor worm of pigs uses Earthworms as the intermediate host?
Metastrongylus apri
Describe the life cycle of Metastrongylus apri
- 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
Describe the disease of Metastrongylus apri
- Typical in 4-7 month old pigs
- Catarrhal and eosinophilic bronchiolitis
- Exacerbates other respiratory disease, e.g. Staphylococcal infections
What are the clinical signs of disease of Metastrongylus apri
- Persistent cough, dyspnoea, nasal discharge
- Reduced weight gain and inappetence
How is Metastrongylus apri diagnosed?
- 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
How is Metastrongylus apri treated and controlled
Anthelmintics - MLs, BZs
Minimising contact with intermediate host
Which factors need to be considered when controlling nematodes in pigs
- Longevity of eggs
- Presence of an intermediate host
- Indoor or outdoor pigs
- Young/breeding sows
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?
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.
Why is the life cycle of Strongyloides ransomi unique?
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
Which parasite forms nodules within the intestinal mucosa?
Oesophagostomum spp.
Which nematode is resilient to anthelmintic treatment that might affect control?
Trichuris suis
Name two parasites that could cause respiratory disease in outdoor pigs
Ascaris suum and Metastrongylus apri
Name two parasites that may cause weight loss in (1) indoor and (2) outdoor pigs.
Indoors: Ascaris suum, Trichuris suis.
Outdoors: Ascaris suum, Trichuris suis, Hyostrongylus rubidus.
