Clinical parasitology in grazing animals Flashcards
What are 4 important internal parasites in grazing animals?
Nematodes (all spp)
Liver fluke (ruminants including camelids)
Lungworm
Coccidia
What are important features of a NEMATODE lifecycle?
PPP 3 weeks
Best larval development when warm and moist (late summer/early autumn)
Larvae survive freezing, not dessication
Outline liver fluke/trematode LC.
Egg (in faeces) –> miracidium (enters snail) –> Sporocyct –> redia –> cercariae (out of snail, onto vegetation) –> metacercaria (encysts on vegetation) –> eaten and develops into mature fluke in liver.
What % of nematode population live within host?
Small amount as 95% larvae live in bottom inch of herbage.
N.b. 80% eggs are passed by 20% animals
What is ‘Targeted Collective Treatment’?
when you treat only the animals which are infected.
Outline the succession of species of worm in grazing animals
NOHT
Nematodirus battus, Teladorsagia (Ostertagia), Haemonchus, Trichstrongylus and fluke (acute, chronic)
Which worm has a barber’s pole appearance?
Haemonchus
When do you see acute and chronic fluke?
Acute = Sep-Dec Chronic = Jan-Mar
What are the major parasites of ruminants?
NEMATODES: Teladorsagia (sheep) Ostertagia (cattle) Haemonchus Trichostronglus Nematodirus
TREMATODES
Fasciola hepatica
CESTODES;
Moniezia
What is the ‘HOT’ acronym?
Reflects size of nematode parasites found in ruminant abomasum:
Haemonchus - 2cm
Ostertagia (cattle) - 1cm
Teladorsagia (sheep) - 0.5cm
Where are Trichostrongylus and Nematodirus found anatomically?
Small intestine
What are the harmful effects of nematodes?
CLINICAL - diarrhoea, weight loss, death
SUB-CLINICAL - reduced weight gain, all grazing animals, LOP
What is the mechanism of nematode harmful effects?
Reduced appetite (70% drop in DMI and weight gain) Altered gut structure and function Immune and inflammatory responses Malabsorption Energy cost of I.R.
Why does protein loss occur in PGE? 4
Increased secretion of mucous and IgA
Increased cell turnover in mucosa
Increased mucosal permeability
Local Ag/Ab reaction in gut –> local vasodilation
What is the FAMACHA Test?
provides a semi-quantitative assessment of anaemia (e.g. caused by Haemonchus). A colour chart is held up against MM to classiy level of anaemia. Aim is to decrease amount of ATHM. used to decrease resistance risk.
What effects can trematodes cause?
ACUTE - liver damage, high number of fluke
CHRONIC - blood and protein loss. Hyperplasia of bile ducts
How might the harmful effects differ between growing and adult animals?
GROWING: reduced weight gain/weight loss poorer FCR \+/- anaemia death
ADULT:
weight loss and poor BCS
+/- decreased reproductive performance
decreased milk/wool production and performance
Adult host immunity is good except in which instances? 4
Goats
If immuno-compromised
PPRI (due to IgA–> mammary gland, ewes especially)
Liver fluke (always poor immunity versus this)
What is the source of parasites in the spring?
over wintered larvae on pasture - major source
larvae from adult animals - minor source
What are the main parasite threats in spring?
N. battus (overwintered eggs)
Type 2 Ostertagiasis in young cattle (late winter really)
When do liver fluke eggs start to hatch?
Summer
What are the main parasite threats in summer?
Nematodes - calves, lambs, goats
Lambs/goats - primarily Telodorsagia
Subclinical effect of bovine PGE/bovine ostertagiosis
When do pasture larval levels peak?
Autumn
When do liver fluke metacercariae enter snails?
Autumn
What are the main parasite threats in autumn?
Nematodes (calves, lambs, goats)
Sheep/goat - primarily Trichostrongylus
Subclinical effects - PGE
What is acute fasciolosis?
From ingestion of millions of metacercariae –> immature fluke tracks in liver. If there are many of these, liver failure will ensue.
How can endoparasites be controlled? 4
Limit exposure of susceptible animals to large numbers of larvae
Anthelmintics to break parasite LC
‘Safe’ pasture
Minimise numbers of susceptible animals
What is SCOPS?
Sustainable Control of Parasites in sheep
Best advice to use, many farmers follow this
What is COW?
Control of Worms Sustainably
in cattle
What are the different classes of anthelmintics?
Yellow - Leavmisoles White - Benzimidazoles Clear - ML Orange - amino-acetonitrile derivatives Purple - spiroindoles
How can you detect anthelmintic resistance? 3
- ) Post-dosing FEC (‘drench tests’)
- ) FECRT
- ) LDTs and EHAs
For drench tests, how long after treatment do you need to wait to take a faecal sample from sheep?
7 days (2-LV)
10-14 days (1-BZ)
14-16 days (3-ML)
What does the drench test detect?
Anthelmintic inefficacy, no AR per se.
When is AR suspected after a FECRT?
When the percentage reduction in FEC of a test group compared with the controls is <95%
What happens in a simpliefied FECRT?
The pre-dose FECs aren’t performed, results are just based on percentage reduction in mean FEC in treatment groups versus controls.
What are LDTs and HEAs?
Larval Development Tests - for 1-BZ and 2-LV anthelmintics
Egg Hatch Assays - for 1-BZ anthelmintics
How does AR vary on a farm?
season, worm species present at time of teset and test’s specificity and sensitivity in detecting resistant alleles in worm population
What are the SCOPS guidelines?
Weigh and dose appropriately
Calibrate and maintain equipment
Drench and inject correctly
Storage (between 4-25 degrees, ensure you shake well - especially white products e.g. BZ).
Where to inject an anthelmintic?
SUBCUTANEOUS - skin of neck under ear by 10-15cm, 1.6cm needle
MUSCULAR - mid neck with 2.5-4cm needle aiming upwards and inwards
