10 - SR internal parasites
internal parasites
helminths
nematodes
trematode
cestode
protazoa
coccidia
giardia
cryptosporidium
strongyle lifecycle
21-day pre-patent period (longer if not perfect conditions)
5 days from L1 to L3
larvae encyst (hypobiosis) in wall of abomasum during summer or winter
haemonchus contortus
Needs 100% humidity at ground level (2 cm of rain per mo)
temps 60-95F
consums 0.05 mL of blood/day
periparturient rise
rise in number of eggs in pasture due to more shedding from stress
Begins 2-4 weeks before births
lasts 6-8 weeks
higher in multiple births
higher in lower protein diets
other worms
trichostrongylus
more hardy in cold and dry
telodosagia
likes cooler, temperate climates (40-68F)
strongyloides
low pathogenicity
ingestion or skin penetration
PPP = 9 days
lungworms
muellerius and Dictyocaulus
P. tenuis
meningeal worm
tapeworm
oestrus ovis
nasal bot
coccidia
economics
1/3 of sheep losses due to parasites
sustainable parasite control
prevent anthelmintic resistance
manage current resistance
reduce reliance on anthelmintics
prevention is better than treatment
anthelmintic resistance
permanent (except levamisole after 5 yrs)
not preventable, only slowed
absence of refugia
refugia
part of worm population which is not exposed to anthelmintics
external/free-living stage
portion of flock untreated
20% of the animals have 80% of the worms
reasons
frequent deworming
treating all animals regardless of disease status
deworming in drought
under-dosing → incorrect dose for species, incorrect weight
use of anthelmintics with residual activity
deworming for GI parasites when treatment is needed for meningeal worm or ectoparasites
rotating dewormers
Deworming targets
<80% reduction = resistance
80-95% reduction = clinically effective (leaves refugia)
>95% reduction = susceptible
how to measure resistance
clinical response to drenching
fecal egg count reduction test
DrenchRite assay (not commercially available in the US)
side resistance
if resistant to one benzimidazole, resistant to all
moxidectin has efficacy against ivermectin resistant parasites
anthelmintics
white
benzimidazole
clear
macrocyclic lactones → avermectins, milbemycin
yellow
levamisole
pyrantel
using dewormers
weigh each animals
store at safe temps
do not dose multiple times → except benzimidazole at 24 hours
hold off feed for 24 hours for white and clear dewormers
using multiple dewormers at once
do not mix
delays development of resistance
achieves clinical effectiveness
can use as quaratine treatment
copper oxide wire particles
use in ADDITION to good management
use only to kill adult worms
GOATS ONLY, HAEMONCHUS ONLY → toxic to sheep
determining who to treat
need some parasite load for immunity
not all worms are pathogenic
resilient animals will carry high loads and not be affected → infect pasture
resistant animals have low loads during high risk/heavy pasture load → genetically important
5-point test
eye/FAMACHA
only used for hamonchus
must use card → replace when faded, certification needed
deworm with score of 4-5 (sometimes 3 if young, lactating, poor BCS, high FEC, trending up, high-risk period)
back/BCS
females at parturition = 3.5/5
females at breeding = 3-3.5/5
Bucks at breeding = 4/5
bottle jaw (late stage infection)
low protein
tail/scours (DAG score)
check fecal
may be nutrition or coccidia if <1 yr
Treat if DAG score >/= 3
nose
oestrus ovis
may have other causes: dust, respiratory viruses, bronchopneumonia, stress
alternate to nose: coat condition
arbitrary score 1-3 (1 = shiny)
affected by nutrition/external parasites
quantifiable fecal testing
identify types of eggs
whips not very worrying goats unless >200 EPG; 100 epg very worrying in camelids
McMaster EPG → 28 ml solution + 2 g feces
Stolls/Wisconsin sugar
fecal egg count reduction test → perform 10-14 days after dosing; good = 95% efficacy, adequate = 85% reduction; DON’T POOL SAMPLES
must use in conjuction with 5 point scores to find genetically resistant/resilient animals
TP/PCV
confirms FAMACHA score and bottle jaw
preventing resistance
good nutrition
cull susceptible animals
keep resistant animals
pasture management
tannins
copper oxide particles
correct doage
correct anhelmintic
correct weight
leave refugia/targeted deworming
kidding and weaning management
biosecurity
mantra
monitory regularly
drench sparingly
cull religiously
targeted deworming
most susceptible
weaned kids
orphan kids
yearlings
high-producing females
late-born kids
geriatric animals
less susceptible
mature animals
dry females
pets
males
sheep compared to goats
large flocks
leave 10-20% of group untreated (dependent on resistance level
breeding for worm resistance
cull animals with high FEC
use high FEC rams/bucks for terminal sire flock
grazing pastures
rotation
every 1-3 days
rest a minimum of 60 days (6 mo in warm, wet conditions)
use modified sandhill calving system
move, then dose
tannins
increase in by-pass protein
reduced bloating
increased milk production
reduced internal parasite numbers, egg output, hachability
can be toxic in excess
biosecurity
dry lot new animals 48 hours
treat with 2 anthelmintics
turn out onto dirty pasture