Clinical parasitology (Yr 4)

Question 1

what would resistance to an anthelmintic be defined as?

Answer 1

<95% drug efficacy

Question 2

what are the main nematodes causing disease in sheep?

Answer 2

Nematodirus battus
Teladorsagia circumcincta
Trichostrongylus spp.
Haemonchus contorts
Dictyocaulus filaria

Question 3

what age is Nematodirus battus seen in sheep?

Answer 3

6-12 week old lambs in late spring

Question 4

what is the main clinical sign of Nematodirus battus?

Answer 4

acute severe diarrhoea

Question 5

what age is type 1 Teladorsagia infection seen?

Answer 5

first season grazing lambs from mid summer onwards

Question 6

what the is type 2 Teladorsagia seen?

Answer 6

yearling in winter months (due to emergence of hypobiotic larvae

Question 7

what age is Trichostrongylus seen?

Answer 7

lambs/replacements in late summer to autumn

Question 8

what is the main clinical sign of Trichostrongylus infection?

Answer 8

black scour

Question 9

what is the main clinical sign of Haemonchus contortus?

Answer 9

acute regenerative anaemia

Question 10

what nematodes have a typical trichostrongyle lifecycle?

Answer 10

Telodorsagia circumcinta
Trichostrongylus spp.
Haemonchus spp.

Question 11

what is the typical trichostrongyle lifecycle?

Answer 11

L3 (infective) is ingested
mature into L4 and adults
eggs passed in faeces
moult to L1, L2 and L3
L3 are eaten or overwinter

Question 12

what is the pre-patent period of nematodes with a typical trichostrongyle lifecycle?

Answer 12

3 weeks

Question 13

why does egg output from ewes rise around lambing?

Answer 13

peri-parturient rise (drop in immunity around lambing)

Question 14

where does most of the eggs come from for Haemonchus infections?

Answer 14

from the ewes (doesn’t overwinter very well)

Question 15

when do Trichostrongylus infections peak?

Answer 15

late summer

Question 16

what is the main way Haemonchus survive over winter?

Answer 16

hypobiosis

Question 17

how do lambs become infected with Nematodirus battus?

Answer 17

eggs shed by lambs previous year remain on pasture and will infect the next crop of lambs

Question 18

what causes hatching of Nematodirus battus?

Answer 18

prolonged period of chill followed by increased temperature cause mass hatching on master (this coincides with lambs being turned out)

Question 19

do sheep develop resistance to nematodes?

Answer 19

yes - if they have been exposed they will develop resistance at about 6 months old

Question 20

what are the classes of anthelmintics?

Answer 20

1. benzimadazoles (white)
2. levamisole (yellow)
3. macrocytic lactones (clear)
4. amino-acetonitrile (orange)
5. spiroindoles (purple)

Question 21

how do benzimadazoles work?

Answer 21

prevent glucose uptake (ovicidal)

Question 22

how does levamisole work?

Answer 22

causes paralysis of parasites (ovoidal)

Question 23

how do macrocyclic lactones work?

Answer 23

block GABA channels to cause paralysis

Question 24

what endoparasites will benzimidazoles kill?

Answer 24

nematodes
tapeworms
fluke (albendazole)
Nematodirus battus (little resistance)

Question 25

what parasites will macrocyclic lactones kill?

Answer 25

nematodes and mites (injectables)

Question 26

how can you test for resistance to anthelmintics?

Answer 26

faecal egg count reduction (compare faecal egg count before and after dosing, a reducing of <95% means that there is resistance) drench test (FEC after dosing)

Question 27

what are the SCOPS principles?

Answer 27

always make sure treatment is effective reduce dependance on anthelmintics through management avoid bringing in resistant worms through biosecurity minimise selection for resistant worms when treating

Question 28

what nematode do sheep not gain resistance to?

Answer 28

Haemonchus spp.

Question 29

if treating at lambing time for nematodes, should you treat all the ewes?

Answer 29

no, treat the ones that will have the highest worm output during their peri-parturient rise such as triplets, thin ewes, ewe lambs...

Question 30

what nematode is there a vaccine against?

Answer 30

Haemonchus (barbervax)

Question 31

what clinical sign can be used as a guide for dosing Hameonchus?

Answer 31

pallor of eye MM (anaemia) - this is called the FAMANCHA test

Question 32

how often should you sample lambs for FEC?

Answer 32

2-4 weeks

Question 33

what nematode can FEC not be used for a diagnosis tool to guide dosing?

Answer 33

Nematodirus battus

Question 34

why can't FEC be used as an accurate way of deciding to dose Nematodirus?

Answer 34

the larval stages cause disease, so FEC won't determine how many larva are present only adults

Question 35

how should quarantined sheep be treated for nematodes?

Answer 35

dose with class 4 or 5 and hold inside for 2 days then place on contaminated pasture so they pick up the infections of the farm

Question 36

how can selection for anthelmintic resistance be minimised?

Answer 36

worm when majority of worms are in the sheep and not on pasture (eg. don't dose at lambing) don't dose and move (leave on contaminated pasture for a few days) only treat thin, young or immunocompromised sheep avoid long acting products

Question 37

when do we want to dose sheep in relation to the amount of parasites on pasture?

Answer 37

when lowest number are on pasture, as this is a massive selection pressure

Question 38

which cestode is zoonotic?

Answer 38

Echinococcus granulosus

Question 39

what is the primary host for the majority of cestode infections?

Answer 39

dog

Question 40

what is the clinical significance of Taenia hydatigena?

Answer 40

cysts in liver causing condemnation

Question 41

what is the clinical significance of Taenia ovis?

Answer 41

cysts cause muscle damage and condemnation

Question 42

what is the clinical significance of Taenia muliticeps?

Answer 42

cysts cause neurological disease in sheep

Question 43

what is the clinical significance of Echinococcus granulosus?

Answer 43

cysts in liver/lungs cause condemnation zoonotic

Question 44

what is the control strategy for Monezia expansa?

Answer 44

worm sheep with benzimadzoles

Question 45

how are Taenia spp. and Echniocccus controlled?

Answer 45

treating dogs with praziquantel to kill adults no dogs faeces on pasture or scavenging of carcasses