parasitic nematodes

Question 1

important parasites in sm ruminants

Answer 1

haemonchus contortus- anemia
PGE- teladorsagia, trichostrongylus- d+

coccidiosis- eimeria sp

Question 2

control of nematodes in sheep:

Answer 2

difficult due to resistance
variable knowledge
tailored to each farm

Question 3

integrated approach to parasite control

Answer 3

1. grazing management
2. targeted tx

Question 4

epidemiology of GI nematodes

Answer 4

Question 5

two sources of infective L3

Answer 5

1. overwintered on pasture
2. from eggs deposited by animals

Question 6

do nematodes overwinter in western Canada?

Answer 6

not haemonchus, but teladorsagia and trichostrongylus do

Question 7

risk assessment of pastures

Answer 7

if it was grazed by sheep w poor parasite control- high risk

if in the summer/fall-> haemonchus is also a risk

Question 8

monitoring risk

Answer 8

FEC to build picture of pasture contamination- 20 animals per group
ewes in spring, lambs in fall

Question 9

rotational grazing

Answer 9

how long does it take for infective larvae to appear? 1wk-1m, faster in summer

grazing hx
higher risk if return to the same pasture that season
avoid overgrazing!

Question 10

antihelmintics

Answer 10

fenbendazole, albendazole- widespread resistance

ivermectin- resistance

moxidectin- resistance is rare- persistent activity (PO 3wks, inj 5wks)

closantel- h. contortus only, rare resistance

Question 11

dosing in sheep

Answer 11

oral>injectable>pour on
injectable can lead to resistance

remember meat withdrawal

Question 12

deworming protocol

Answer 12

dont use recipe based
targeted tx, evidence based w monitoring
assess drug efficacy

minimize number of doses, use full dose TST
dose new sheep with combination

Question 13

refugia

Answer 13

portion of parasites that have not been treated (no resistance)
parasites in untreated host and environment

Question 14

targeted selective tx

Answer 14

use FAMACHA (3-5) or BCS, growth rate, DAG score

Question 15

quarantine dosing

Answer 15

hold from pasture 24-48h
combination tx
check FEC 10-14d

Question 16

host genetics and breeding for parasite control

Answer 16

resistance- resist infection, high heritability
tolerance- tolerates infection effects (low heritability)

lower in goats and wool sheep

cross breeding, EBV, on farm selection

Question 17

on farm selection for parasite resistance

Answer 17

individual ID, similar age
significant exposure to parasites
FECa

Question 18

alternative methods for parasite control

Answer 18

alternative forages (trefoil, sulla)
nematode trapping fungi (duddingtonnia flagrans)

copper oxide wire particles (h. contortus)
native protein vx (aus)

Question 19

coccidiosis life cycle

Answer 19

small number of infective oocysts-> massive multiplication-> lg number in feces

Question 20

eimeria sp

Answer 20

many species, some arent pathogenic
infect different parts of GI
highly host specific
oocysts arent infective right away- resistant and take 2d-wks

sheep- crandallis, ovinodallis
goats- arlongi, caprina, christenseni, hirci

Question 21

coccidiosis pathogenesis, C/S

Answer 21

indoors and outdoors, 3wks-3m
lysing of epithelial cells-> severe damage to lg intestine

acute- abd pain, straining, watery d+, dysentery, fever, lack of appetite, death

chronic- chronic d+, poor growth, thin. can be subclinical

Question 22

coccidiosis dx

Answer 22

C/S, risk factors (density, poor hygiene, stress, bad weather, diet change)

hx, necropsy, FEC (chronic 1000s, acute 10000s)

Question 23

coccidiosis tx

Answer 23

coccidiostats:
decoquinate, monensin, lasalocid- prevention (sporozoites, merozoites)

amprolium- tx (schizonts)
toltrazuril- tx and prevention

tx all animals in group-> amprolium 5d (water)
toltrazuril-> single oral

remove from contaminated pasture, separate sickest for supportive care

Question 24

coccidiosis prevention

Answer 24

1. coccidiostats (28d), one dose toltrazuril
2. sanitation
3. spread out animals
4. minimize weaning stress
5. grazing management- avoid overgrazing, separate by age

Question 25

5 star worm plan

Answer 25

1. manage pasture contamination
2. use dewormer appropriately
3. monitor and treat selectively
4. quarantine and tx new sheep
5. investigate tx failure