Epidemiology of PGE Flashcards
What does PGE stand for?
Parasitic gastro-enteritis
What parasites are involved?
Telodorsagia circumcinta- primary cause
Trichostronglus spp and Cooperia worsen
What does the severity of the disease depend on?
Concurrent infection
Nutritional status of sheep
Development of immune response
When does PGE cause diarrhoea in lambs?
Late summer August- September
What are the influencing factors of PGE?
peri-parturient rise in ewes, hypobiosis of larvae, development of eggs to L3 in environment, host susceptibility
What is the main source of contamination of pasture?
Peri-parturient rise
How can overwintered larvae contaminate pasture?
L3 overwinter if they are present on pasture from the previous year therefore present on pasture when the lambs start to graze, but will gradually die out by June
What is the development of free living stages dependent on?
Temperature
Humidity
Dispersal from faeces (rain)
Why is there a peak in august?
Eggs passed earlier take linger to develop therefore both peak in august
What affects the lifespan of L3 larvae?
Ensheathed
Temperature
Moisture (defecation)
What are the host factors of PGE?
Age and immune status- lambs at risk
Over dispersion- small proportion of host carry majority of parasite
Adults acquire immunity following repeated exposure
When do ewes mainly contaminate pasture?
Up to 2 weeks before lambing till 6 weeks after
What happens from May- June?
Ewe contamination of pasture eggs shed and start development Lambs graze, ingest PPP 3 weeks Eggs shed from lambs to pasture
What happens from June- July?
As temp increases egg development increases
Large numbers of L3 on pasture by end
What is the peri-parturient rise?
increase in egg output just prior and for several weeks after parturition due to decreased immunity
