Parasitology: Principles Flashcards
What is the life cycle of the liver fluke
Fluke eggs in faeces which hatch to release miracidia
Miracidia infect snails and snails release infective cercariae which cyst and are ingested on the vegetation
Juvenile flukes energy from cysts and migrate to the liver where they chill in the bile ducts
What does finding worm eggs or larvae in faeces mean?
The life cycle has already been completed
Damage has already occurred
Environmental contamination has occurred
What are signs associated with parasitic infection?
» Liver flukes: weight loss, reduced appetite and diarrhoea, jaundice
» Lungworms: Persistent cough, lower head and stretch neck with mouth breathing
» GI worms: : weight loss, reduced appetite and diarrhoea anaemia
What are laboratory findings associated with parasitic infection?
- Liver flukes: y- glutamyl transpeptidase or transferase
- Lungworms: blood and tracheal washes- eosinophilia
- GI worms: plasma pepsinogen or gastrin
What are gross pathological findings associated with parasitic infection?
- Liver flukes:
- Lungworms:
- GI worms:
What benefits are associated with the farm owner being vigilant to changes in animal behaviour and surroundings
- Liver flukes: heavy rain/floods, snails, sudden death
- Lungworms: unpredictable, fast
- GI worms: spring rise, acute death of lambs
What risks or drawbacks can you think of associated with attentive farm owners?
Frequent use of antihelmetics
Give some examples of changing patterns of sheep parasitism
- Haemonchosis: Previously a problem confined to SE England, Haemonchus spp are now more widespread and found in Wales and Scotland
- Nematodirosis: It was seen as a spring problem, but it is now also seen in the autumn.
- Trichostrongylosis: was traditionally seen in the autumn in store lambs, but it is now encountered earlier in the summer, causing losses in younger lambs, or in mild winters, causing problems much later than previously described
How can Duddingtonia flagrans be used as a “biological Anthelmintic”
» It reduces the number of infective larvae on pastures to an economically acceptable level
» Aerobic fungus, not genetically manipulated
» Broad-spectrum
» No residues, no withdrawal period
» Active against drug resistance worms
How can we handle AR?
Change anthelmintic classes annualy (between benzimidazoles – levamisole – macrocyclic lactones) Farms with resistance against benzimidazoles: do not use this anthelmintic class for 5 years Do not underdose Keep the frequency of treatment as low as possible
- Resistance against benzimidazoles in most sheep farms
- Widespread resistance against levamisole and macrocyclic lactones
How to diagnose resistance?
Fecal egg count reduction test (McMaster): 2 faecal samples: first before and the second 7-10 day after treatment of the same animal
Larval hatch test: In vitro culture of larvae in the presence of anthelmintic compounds
What is refugia?
Only treat animals with heavy parasite burden or showing clinical signs (Use FAMACHA®)
Maintain a parasite population which is sensitive to anthelmintic treatment
What happens to parasite mutants that are able to tolerate treatment?
They reproduce and pass on their resistance
What is the Mcmaster calculation?
Number of eggs per g faeces = Number of eggs counted x total volume of liquid/ (0.3/ volume of counting chamber) x weight of faeces
What parasites are Insect: 6 legs, 3 body parts?
lice, flies and fleas
