parasitic nematodes Flashcards
important parasites in sm ruminants
haemonchus contortus- anemia
PGE- teladorsagia, trichostrongylus- d+
coccidiosis- eimeria sp
control of nematodes in sheep:
difficult due to resistance
variable knowledge
tailored to each farm
integrated approach to parasite control
- grazing management
- targeted tx
epidemiology of GI nematodes
two sources of infective L3
- overwintered on pasture
- from eggs deposited by animals
do nematodes overwinter in western Canada?
not haemonchus, but teladorsagia and trichostrongylus do
risk assessment of pastures
if it was grazed by sheep w poor parasite control- high risk
if in the summer/fall-> haemonchus is also a risk
monitoring risk
FEC to build picture of pasture contamination- 20 animals per group
ewes in spring, lambs in fall
rotational grazing
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!
antihelmintics
fenbendazole, albendazole- widespread resistance
ivermectin- resistance
moxidectin- resistance is rare- persistent activity (PO 3wks, inj 5wks)
closantel- h. contortus only, rare resistance
dosing in sheep
oral>injectable>pour on
injectable can lead to resistance
remember meat withdrawal
deworming protocol
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
refugia
portion of parasites that have not been treated (no resistance)
parasites in untreated host and environment
targeted selective tx
use FAMACHA (3-5) or BCS, growth rate, DAG score
quarantine dosing
hold from pasture 24-48h
combination tx
check FEC 10-14d
host genetics and breeding for parasite control
resistance- resist infection, high heritability
tolerance- tolerates infection effects (low heritability)
lower in goats and wool sheep
cross breeding, EBV, on farm selection
on farm selection for parasite resistance
individual ID, similar age
significant exposure to parasites
FECa
alternative methods for parasite control
alternative forages (trefoil, sulla)
nematode trapping fungi (duddingtonnia flagrans)
copper oxide wire particles (h. contortus)
native protein vx (aus)
coccidiosis life cycle
small number of infective oocysts-> massive multiplication-> lg number in feces
eimeria sp
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
coccidiosis pathogenesis, C/S
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
coccidiosis dx
C/S, risk factors (density, poor hygiene, stress, bad weather, diet change)
hx, necropsy, FEC (chronic 1000s, acute 10000s)
coccidiosis tx
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
coccidiosis prevention
- coccidiostats (28d), one dose toltrazuril
- sanitation
- spread out animals
- minimize weaning stress
- grazing management- avoid overgrazing, separate by age
