Revision Haemonchus & Ostertagia Flashcards
Outline a classification table?
Outline abomasal worms?
- Ostertagia ostertagi is the most important stomach worm of cattle in UK
- Teladorsagia (Ostertagia) circumcincta is an important parasite of sheep
- Haemonchus contortus is an important parasite of sheep-world wide interest due to anthelmintic resistance
All are trichostrongyle nematodes
Look at these images of ostertagia ostertagi (Brown stomach worm)?
Outline the ostertagi ostertagi life cycle?
- L2 sheath (covering L3) lost in the fore-stomach
- L3 migrates to the gastric glands where it moults to L4 inside of the gastric glands
- Immature adults emerge from the gastric glands ( The cause of pathology )
- Adults produce eggs and the cycle is complete
Discuss type 1 ostertagiasis?
- Type I Ostertagiasis: May occur in calves yearlings (younger animals) when enough L3 have been ingested
- Type 1 disease can occur in calves turned out on pasture in April/May
- Pasture which has been grazed previous year (especially by calves)
- L3 overwinter so that large numbers may already be present as the calves are turned out
- Peak of Ostertagia on grass is therefore Aug/Sept when many infected calves shed high numbers of eggs
- L3 which have not been ingested will over-winter on pasture for next year- Rotation is important!
What is type II ostertagiasis?
Type II Ostertagiasis: Occurs in animals which are old enough to have arrested larvae from previous grazing season.
NB: 100 000s worms may arrest per animals spring Peri-parturient rise (PPR) (Spring rise)
What are the effects on the gastric gland of ostertagia infection?
- HCl not produced (PH may change from ~2.5->5) [parietal cells]
- High PH prevents conversion of Pepsinogen to pepsin (protein digestion significantly affected)
- Pepsinogen and gastrin detected in increased levels in blood (abomasal pH stimulates production of gastrin)
- Blood proteins (e.g. albumin) increase in abomasum and in some distinct tissues
- Bacterial overgrowth in the abomasum also occurs
What is the pathology of ostertagia?
Discuss immunity to O. ostertagia?
- First immune response does not protect against re-infection with L3 (hence repeated re- infection occurs )
- Delays larval development, increases the number of inhibited worms (immune-induced hypobiosis), stunts adults, reduce fecundity/less egg production
- Believed to be IgA mediated
- Second immune response may take up to 2 years
- Reduces number of L3s infecting cattle
- Sterile immunity is never observed, thus even ‘immune animals’ will produce low numbers of nematode eggs
- Eosinophils and mast cells increase in intestine (suggests Th2 driven response)
- A stereotypical parasite induced Th2 response has not been reported with studies reporting both Th1 and Th2 cytokines Immunity to O. ostertagi
Control measures for O. ostertagia?
More difficult to treat hypobiosis but drugs such as Ivermectinwill kill the hypobiotic L4
In some cases very frequent drenching may be required around calving ( Type II )
Frequent drenching may be required during the first grazing season ( Type I ), especially for animals raised on pasture on which calves grazed previous season
- Lower stocking density
- Rotate calves and adults
- Rotate onto fresh pasture if possible Control measures
Look at haemonchus contortus?
What is the distribution haemnonchus contortus?
- UK-Typically South/South east where climate is slightly warmer and dryer
- World wide-Very important parasite of sheep and goats in tropical/subtropical regions
- In some cases resistant to all classes of current anthelmintics, which has made sheep farming in some regions non- sustainable
NB: Parasitic gastroenteritis (PGE) can be caused by many nematode species from early summer to autumn. Often anthelmintic treatment may be given and if it works PGE will simply be diagnosed
What is the haemonchus contortus life cycle?
What happens inside the sheep with H. contortus?
Look at the Famacha score?
Look at this?
