PID 2

Question 1

pge acronym

Answer 1

parasite gastroenteritis, more than one parasite causing this diesease

Question 2

what kind of parasite is it associated with

Answer 2

nematodes, either alone or incombination

Question 3

signs

Answer 3

diarrhoea, weight loss (in clinical disease), LOP (loss of production), hypoalbuminea

Question 4

economic importance

Answer 4

grazing livestock, esp organic farm

Question 5

association of economic losses

Answer 5

replacement of stock, breeding programme, impaired productivity, treatment and prophylaxis

Question 6

nematodes in abomasum

Answer 6

ostertagia, trichostrongylus, haemonchus

Question 7

nematodes in small intestine

Answer 7

cooperia, nematodirus, trichostrongylus

Question 8

ostertagia

Answer 8

primary pathogen of cattle, adults 1cm long, cotton-like, brown (‘brown stomach worm’), found in glandular =/fundus abomasum

Question 9

lifecycle ostertagia

Answer 9

direct lifecycle:

Question 10

prepatent period (IMP)

Answer 10

3 weeks, time between infection and egg shedding (parasite visible) BUT, can be as long as 6 months

Question 11

why can it be as long as 6 months?

Answer 11

because larvae L3 can survive overwinter via overwintering (because L3 retain sheath the protects them against harsh conditions) + arrested development (hypobiosis) –> L3 undergo arrested development in the host

Question 12

what do L3 do

Answer 12

climb up the grass, survive in droplets, penetrate gastric glands in the fundus of abomasum

Question 13

what do they do in the host

Answer 13

emerge from the fundus –> causes trauma

Question 14

what is epidemiology (risk of disease) dependent on?

Answer 14

rate of infection (larvae cow ingests) vs host immunity

Question 15

so what determines rate of infection

Answer 15

appetite of cow, density of larvae

Question 16

what population most common?

Answer 16

calves, high stocking density

Question 17

how does pasture larval count evolve through the year? (IMP)

Answer 17

from january to june –> over-wintering L3, if not ingested die + turnout of cows around spring (btw March and May) –> cows start ingesting L3s –> 3 weeks later start shedding eggs –> end of summer: accumulation of L3s on pasture ==> auto-infection peak because larvae developed from eggs that the cows themselves have shed earlier in the season

Question 18

when does type 1 disease develop?

Answer 18

when nb of L3 exceed level

Question 19

when does type 1 disease develop (IMP)

Answer 19

at the end of the grazing season

Question 20

what happens after summer?

Answer 20

arrested L4s in abomasal mucosa –> L4s resume development and emerge in waves

Question 21

in beef herds, what is the difference that counts for epidemiology?

Answer 21

mums and calves put together, mums immune to the disease –> very unlikely in spring calving

Question 22

what happens in autumn calving in beef herds? (VERY IMPORTANT)

Answer 22

calves inside until spring when put on pasture –> put on larvae but because raised with mums –> mums ingest must larvae –> auto-infection peak not as high to cause disease

Question 23

immunity of ostertagia ostertagi

Answer 23

slow to develop (whole grazing season), may fall overwinter, re-established upon turnout (2nd grazing season), adults are solidly immune –> nb of eggs they shed is smaller

Question 24

how do we avoid clinical disease?

Answer 24

use clean pasture, not always available OR later turnout of calves because most wintering L3s would have died

Question 25

what does later turnout involve

Answer 25

use of concentrate feeding, economic losses

Question 26

if know when the turnout happens, what can you do?

Answer 26

worm them and move them to clean pasture 'does'n move)

Question 27

dose'n move sequence

Answer 27

let calves in spring and early summer --> move them to clean pasture in mid-summer (any overwintering L3s would have died)

Question 28

(2) problems with dose'n move

Answer 28

not solution for type 2 disease, increased risk of antihelmintic resistance

Question 29

strategic anthelmintic treatment

Answer 29

repeated treatment after mid-July (but temporary control only) OR before mid-July drugs that have residual activity

Question 30

when do you administer drugs with residual activity

Answer 30

one at turnout and one at 8 weeks post turnout

Question 31

why do you delay 2nd treatment by 8 weeks?

Answer 31

because residual activity is 5 weeks and pre-patent period is 3 weeks

Question 32

what period do you cover with 2 treatments

Answer 32

14 weeks

Question 33

what drugs can be administered once?

Answer 33

intra-ruminal boluses have residual activity of 12-14 weeks --> protect calves during whole grazing season

Question 34

examples of drugs

Answer 34

ivomec (withdrawn), paratect (withdrawn), autoworm, panacur bolus BUT expensive

Question 35

when is the treatment required?

Answer 35

when cattle exposed to high quantities of the nematode