Clinical Parasitology of small ruminants & camelids Flashcards
What main important parasites in cattle & sheep (GIT parasites)
Where do each sheep gut parasites affet?
Nematodirrus (Small intestine)
Ostertagia/Teladorsagia (Abomasum)
Trichostrongylus (Small intestine)
Haemonchus (Abomasum)
WHEN do sheep parasites happen?
Is nematodirus as significant in goats/ camelids as it is in lambs?
NO
describe Nematodirus timing & pathogenesis ?
- Hatching requires prolonged chill, then mean temp
>10oC (late spring)- outbreak May-June - Larvae cause disease (migrating and sheading in mucosa)
- Villous atrophy and fusion
Transmission of nematodirus?
- Lamb to Lamb- last years lamb infecting this years
- Eggs survive on pasture for a long time
Signs of Nematodirus?
- Diarrhoea
- Inappetence
- Reduced growth rates
- Death
- Mortality high if untreated
Detailed pathoG of nematodirus?
Last years lambs contaminate the pasture ->
Lambs are moved on, eggs rain and overwinter on pasture ->
New season lambs on same pasture ->
Activation of over winted eggs to larvae and consumed in sudden large numbers causing clinical disease ->
Disease in prepatent period = no eggs on FEC
When does Teladorsagia occur?
- July- October
Burdens of teladorsagia related to ?
weather patterns and previous Hw of pasture infestation
Transmission of Teladorsagia?
- Infection from ewes with an periparturient rise in FEC
- Eggs passed by lambs after ingesting overwinter larvae from last years lambs
- Eggs passed by lambs early in season infect lambs later in
same season - Eggs develop to larvae on pasture
What do we see with teladorsagia before vs after October?
- Before Oct= clinical disease (type 1)
- After Oct=Larvae arrested (type 2)
Signs of Teladorsagia & Immunity?
- Weight loss, intermittent diarrhoea, poor weight gain in lambs, ill thrift
- Immunity is acquired slowly (over 2 grazing seasons)
How does initial transmission / high burden happen with teladorsagia?
- SMall population of eggs overwintered ->
- Peripartum reduction in immunity = increased egg contamination from ewes around lambing ->
- Eggs develop into larvae about July
- Lambs now ingesting large numbers of larvae on pasture which were eggs from ewes/overwinter
- Larvae develop to adults PP-3 weeks so development of CS July-Oct
THEN
Lambs end up infecting the pasture for other lambs in the same cohort due to high burdens of adult worms
When does Haemonchus/ contortus become a problem?
Warm/wet weather
July/august
Transmission / high burdens of Haemonchus ?
- Overwintering in the host (ewe) as inactive L3
- Ewe is source of infection for lambs
- Outbreaks of disease rely on weather conditions and
pasture contamination so often sporadic and
unpredictable - No strong immunity by adult animals so any age
affected
acute dx haemonchus?
- Anaemia, loss of iron and protein in GI tract
- Submandibular oedema
- Inappetence, lethargy, high mortality
chronic dx haemonchus?
- Lower exposure over longer period
- Weight loss, weakness, inappetence
What is Hypobiosis?
The developmental adaptation that allows parasites to persist in their host for extended period of time. State of reduced metabolic activity caused by environmental parameters or host resistance.
Which parasites get arrested development?
- Teladorsagia/oestertagia
- Haemonchus
- Some Trichostrongylus spp
- Cooperia (cattle)
What stage will arrest?
L4 in autumn within immune host -> contributes to re-infection following year
Weather for coccidiosis?
Wet warm weather. Poaching of
ground around troughs
Who does coccidiosis affect ?
- Lambs aged 4-8 weeks old
- Younger animals affected as
season progresses
What does coccidiosis cause and what clinical signs ?
- Damage to the intestines
results in long term impact on
growth rates - Diarrhoea
- Straining
- Mucus or blood
What is the multiplier effect? what does this cause?
Lambs shed millions more oocysts of coccidia than they eat ->
Immunity increases with exposure. Naive lambs at risk of severe dx
What weather for fluke?
Increasing rainfall, acute
fluke in weaned lambs seen
autumn
Lifecycle of fluke ? which important intermediate host?
SNAILS
What faecal exam can we do for what worms?
How to interpret FEC for Nematodirus?
- Nematodirus= FEC not strongly linked to
worm burden- egg production/worm is higher
when there are fewer worms - Egg counts with N battus is usually low when
acute infection as the disease is from prepatent period - Low egg counts of N battus may still be
significant
FEC for haemonchus interpretation?
H contortus egg counts can be very highworms have very high fecundity.
General FEC interpretation ?
- FEC in older animals is a less reliable indicator
of burden - FEC are only representing the worms which
picked up 3-4 weeks ago and not current
ingestion/larval burden
Famcha chart for haemonchus?
What are the categories of ‘broad spec’ Anhelmintics?
Describe White drench?
- Broad spectrum
anthelmintics - Cover against
nematodes - Including lungworm
- Some cover against
Tapeworm - No ectoparasite cover
- Significant resistance seen
Which White Wormer has narrow spectrum?
Triclabendazole - liver fluke only
What do Levimasoles cover?
- Covers nematodes
- Including lungworm
- No cover against tapeworm
- No cover against fluke
- No cover against ectoparasites
- Limited efficacy against encysted larval stages (Ostertagia)
- Significant resistance seen
Therapeutic safety index with Levamisole?
- Therapeutic safety index is low
- Impacts on nerve ganglion causing salivation, bradycardia, muscle tremors
- It is not ovicidal (doesn’t kill eggs)
What wormers are MAcrocyclic lactones?
- Avermectins -> Ivermectin, doramectin
- Milbemycins -> Moxidectin
What do macrocyclic lactones cover?
NEMATODES
- Including lungworm
- Cover extoPs
NO COVER for:
- Tapeworm
- Fluke
SIG Resistance
WHat do orange (Amino-acetonirile derivates) wormers cover?
- Effective against NEMATODES * Even those resistant to other groups
NO cover for:
- Lungworm
- Fluke
- Tapeworm
- EctoP
What do Purple (Sporoindoles) wormers cover?
- Dual active preparation
- Abamectin + Spiroindole= Derquantel
- Covers nematodes
- Including lungworm
NO cover of:
- Tapeworm
- Fluke
- EcctoPs
What narrow spectrums Anthelmintics do we have?
- Phenols = Nitroxynil
- Salicylanilides =closantel and oxyclozanide
What are narrow specs effective against?
- Fluke
- Haemonchus
What else does Salicylanilides cover?
soem ectoPs
Closantel is an … formulation
oral
Nitroxynil is an …… formulation -> it ……. goats
Injectable ; It KILLS Goats !!!
WHat combination with triclabendazole?
2-LV, 3-ML
What combination wormer si common?
Closantel & 3-ML
USe of combination wormers?
- Often used as assurance even if not both required
- Leads to off target selection for resistance to broadspectrum anthelmintics in nematodes or fluke
- Some evidence that combination wormers may improve
efficacy on resistance fluke or haemonchus populations
What worms resistant to what wormers?
What is an FECRT?
Faecal egg count reduction test
How to do a FECRT?
- Day1 = dose with wormer, separate group and dose with each wormer if necessary
= take FEC - Day 7= if dosed with 2-LV = FEC
- Day 14=If dosed 1-BZ, 3-ML= FEC
When is resistance suspected with FECRT?
if less than 95% reduction in burden
What are the SCOPS Principles?
- Establish a parasite control strategy with your vet
- Avoid introducing resistant worms
- Quarantine treatments (monepantel + moxidectin)
- House on concrete for 24hrs
- Move to contaminated pasture - Annual test for anthelmintic resistance (FECRT / DTs)
- Administer anthelmintics effectively
- Check dosing equipment
- Dose for the heaviest sheep - Use anthelmintics only when necessary
Avoid treating immune animals
Do not dose routinely at tupping
ONLY dose poorly conditioned ewes at lambing - Selecting the appropriate anthelmintic
- Preserve susceptible worm population (in refugia)
DO NOT ‘dose-and-move’
Avoid routine dosing
Leave ~10% untreated - Reduce dependence on anthelmintics
How to AVOID introducing new worms?
How do we administer anthelmintics effectively?
When should we NOT dose animals?
AT TUPPING!
- Selective dosing - poor condition - low FAMSHA scores
Should we dose at turnout (peripartum) ?
- Complicated
- Peripartum relaxation of immunity (PPRI)
- FEC rise
- High FEC=Greater parasite challenge for lambs- want to reduce this
- BUT- dosing early in PPRI= no change in FEC rise
- Dosing late= prolonged period before reinfection of the ewe with in-refugia population= highly
selective for AR
Combination produts - what not to use together?
Broad spec wormer + flukicide in fluke only control
How can we reduce dependence on anthlemintics?
- Avoid conventional suppressive treatment strategies
- Use grazing management
- Use rams bred for resistance to worms to improve
genetic immunity in flock - Chose forage/leys that have anthelmintic properties
- Chickory
