Parasitism in Grazing Animals Flashcards
What are the 4 most important internal parasites in grazing animals?
- nematodes
- liver fluke (ruminants inc. camelids)
- lungworm
- cocciddia
What is the PPP of nematodes?
~ 3 weeks
When is the best larval development of nematodes? What can larvae not survive?
- Warm and moist late autumn/summer
- L can survive freezing but not dessication
Outline the liver fluke lifecycle
- eggs shed in feaces
- miracidium -> snail
- cercariea out of snail onto veg
- metacercariae encycts on veg and is eaten
- immature fluke migrates to liver
- mature fluke in liver
Where are the majority of the nematode population found?
- On pasture, 95% within bottom inch of herbage
- 80% eggs passed from 20% animals
What is the succession of species?
Order that helminth worm numbers are highest thoughout the season > April/July - N. Battus > June/Nov - Ostertagia > July/Nov - Haemonchus > Sept/Dec - Trichostrongylus > Sept/Dec - Acute Fluke > Jan/March - Chronic Fluke
What are the major nemotodes of the abomasum and SI in ruminants?
>Abomasum = HOT! Heamonchus contortus (2cm) Ostertagia (1cm) Teladorsagia (0.5cm) >Small Intestine Trichostrongylus Nematodirus
What is the major trematode affecting ruminants?
Fasciola hepatica (liver fluke)
Which is the main cestode to affect ruminants? Where does it live in GIT and how is it picked up?
Moniezia - SI from pasture mites
What clinical and subclinical effects may nematodes have?
> clinical - D+, weight loss, death > sub clinical - v weight gain - all animals affected - LOP
How do nematodes produce pathologic effects?
- reuced appetite most important
- change in GIT structure and function
- immune and inflam responses
- malabsoprtion
- energy cost of immune response
How does PGE -> protein loss?
- ^ secretion mucous and IgA
- ^ mucosal permeability allowing protein leakage
- local Ag/Ab reaction in gut - vasodilation
- ^ cell turnover in mucosa
What effects does haemonchus cause? What test can be used to quantify this?
- anaemia (blood sucking)
- FAMACHA test
What are the harmful effects of trematodes?
> Acute - liver damage
> Chronic - blood and protein loss, hyperplasia of bile ducts
Which age of animal are often affected by parasitism and why?
Young
- Adults develop an immunity (in most cases)
In which cases may adults not be immune from parasitism?
- goats
- immunocompromised
- ewes after lambing (PPRI periparturient relaxation in immunity)
- liver fluke
What is the main source of parasite infections/risk in SPRING?
> Nematodirus battus
- Mainly overwintered on pasture
- Some from adult animals
Type 2 ostertagiosis in young cattle
Is FEC useful in diagnosing spring problems?
NO! PPP = 3 weeks, nothing will be seen in faeces
What is the main source of parasite infections/risk in SUMMER?
> Subclinical effects of PGE/BOVINE OSTERTAGIOSIS
- young susceptable animals grazing
- larval no ^
- liver fluke eggs hatch
- autoinfection peak
- nematodes in calves, lambs and goats
- Teladorsagia mainly (sheep/goats)
What is the main source of parasite infections/risk in AUTUMN?
> SUBCLINICAL EFFECTS PGE
- peak in pasture nematode larval levels
- liver fluke metacercariae in snails
- nematodes in calves, lambs and goats
- Tricholstrongylus mainly (sheep/goats)
- acute fasciolosis (from ingestion of millions of metacercariea -> immature fluke tracks in liver)
What is the main source of parasite infections/risk in WINTER?
- immunity developing in young animals
- larval development halted
- liver fluke develpoing to adults
How can endoparasite related pathology be controlled?
- limit exposure of susceptable animals to large number of larvae (ie. avoid autoinfection peak)
- anthelmintics to break parasite lifecycle
- “safe” pasture (graze horses/other spp. graze adults, long pasture to dilute worm burden, hay/silage aftermath good)
- minimise no. susceptable animals (sell lambs early!!)
Who has provided guidelines for sustainable parasite control in sheep and cows?
SCOPS and COWS
What are the 5 main clases of anthelmintic?
- White Benzamidazoles
- Clear Macrocytic Lactones
- Yellow Levamisoles
- Orange Aminoacetonitrile derivatives
- Purple Spiroindoles
What are the main threats to ruminants from parasites in spring, summer/autumn and winter?
> Nematodes and liver fluke
- Spring: arrested and overwintered larvae
- summer/autumn: PGE
- winter: liver fluke
What is the equivalent of ostertagia in cattle in sheep?
Teladorsagia
What does N. battus cause?
Sudden death of lambs with no eggs on FEC as before PPP
Deinfe the pre-patent period
Time between ingestion and production of eggs in feaces
What must be remembered with parasite lifecycles?
Grazing periods and weather patterns are changing
What clinical sign may be associated with liver lfuke?
Bottle jaw
Is immunity to liver fluke good?
No
