Clinical parasitology in grazing animals

Question 1

What are 4 important internal parasites in grazing animals?

Answer 1

Nematodes (all spp)
Liver fluke (ruminants including camelids)
Lungworm
Coccidia

Question 2

What are important features of a NEMATODE lifecycle?

Answer 2

PPP 3 weeks
Best larval development when warm and moist (late summer/early autumn)
Larvae survive freezing, not dessication

Question 3

Outline liver fluke/trematode LC.

Answer 3

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.

Question 4

What % of nematode population live within host?

Answer 4

Small amount as 95% larvae live in bottom inch of herbage.

N.b. 80% eggs are passed by 20% animals

Question 5

What is ‘Targeted Collective Treatment’?

Answer 5

when you treat only the animals which are infected.

Question 6

Outline the succession of species of worm in grazing animals

Answer 6

NOHT

Nematodirus battus, Teladorsagia (Ostertagia), Haemonchus, Trichstrongylus and fluke (acute, chronic)

Question 7

Which worm has a barber’s pole appearance?

Answer 7

Haemonchus

Question 8

When do you see acute and chronic fluke?

Answer 8

Acute = Sep-Dec
Chronic = Jan-Mar

Question 9

What are the major parasites of ruminants?

Answer 9

NEMATODES:
Teladorsagia (sheep)
Ostertagia (cattle)
Haemonchus
Trichostronglus
Nematodirus

TREMATODES
Fasciola hepatica

CESTODES;
Moniezia

Question 10

What is the ‘HOT’ acronym?

Answer 10

Reflects size of nematode parasites found in ruminant abomasum:
Haemonchus - 2cm
Ostertagia (cattle) - 1cm
Teladorsagia (sheep) - 0.5cm

Question 11

Where are Trichostrongylus and Nematodirus found anatomically?

Answer 11

Small intestine

Question 12

What are the harmful effects of nematodes?

Answer 12

CLINICAL - diarrhoea, weight loss, death

SUB-CLINICAL - reduced weight gain, all grazing animals, LOP

Question 13

What is the mechanism of nematode harmful effects?

Answer 13

Reduced appetite (70% drop in DMI and weight gain)
Altered gut structure and function
Immune and inflammatory responses
Malabsorption
Energy cost of I.R.

Question 14

Why does protein loss occur in PGE? 4

Answer 14

Increased secretion of mucous and IgA
Increased cell turnover in mucosa
Increased mucosal permeability
Local Ag/Ab reaction in gut –> local vasodilation

Question 15

What is the FAMACHA Test?

Answer 15

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.

Question 16

What effects can trematodes cause?

Answer 16

ACUTE - liver damage, high number of fluke

CHRONIC - blood and protein loss. Hyperplasia of bile ducts

Question 17

How might the harmful effects differ between growing and adult animals?

Answer 17

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

Question 18

Adult host immunity is good except in which instances? 4

Answer 18

Goats
If immuno-compromised
PPRI (due to IgA–> mammary gland, ewes especially)
Liver fluke (always poor immunity versus this)

Question 19

What is the source of parasites in the spring?

Answer 19

over wintered larvae on pasture - major source

larvae from adult animals - minor source

Question 20

What are the main parasite threats in spring?

Answer 20

N. battus (overwintered eggs)

Type 2 Ostertagiasis in young cattle (late winter really)

Question 21

When do liver fluke eggs start to hatch?

Answer 21

Summer

Question 22

What are the main parasite threats in summer?

Answer 22

Nematodes - calves, lambs, goats
Lambs/goats - primarily Telodorsagia
Subclinical effect of bovine PGE/bovine ostertagiosis

Question 23

When do pasture larval levels peak?

Answer 23

Autumn

Question 24

When do liver fluke metacercariae enter snails?

Answer 24

Autumn

Question 25

What are the main parasite threats in autumn?

Answer 25

Nematodes (calves, lambs, goats) Sheep/goat - primarily Trichostrongylus Subclinical effects - PGE

Question 26

What is acute fasciolosis?

Answer 26

From ingestion of millions of metacercariae --> immature fluke tracks in liver. If there are many of these, liver failure will ensue.

Question 27

How can endoparasites be controlled? 4

Answer 27

Limit exposure of susceptible animals to large numbers of larvae Anthelmintics to break parasite LC 'Safe' pasture Minimise numbers of susceptible animals

Question 28

What is SCOPS?

Answer 28

Sustainable Control of Parasites in sheep | Best advice to use, many farmers follow this

Question 29

What is COW?

Answer 29

Control of Worms Sustainably | in cattle

Question 30

What are the different classes of anthelmintics?

Answer 30

``` Yellow - Leavmisoles White - Benzimidazoles Clear - ML Orange - amino-acetonitrile derivatives Purple - spiroindoles ```

Question 31

How can you detect anthelmintic resistance? 3

Answer 31

1. ) Post-dosing FEC ('drench tests') 2. ) FECRT 3. ) LDTs and EHAs

Question 32

For drench tests, how long after treatment do you need to wait to take a faecal sample from sheep?

Answer 32

7 days (2-LV) 10-14 days (1-BZ) 14-16 days (3-ML)

Question 33

What does the drench test detect?

Answer 33

Anthelmintic inefficacy, no AR per se.

Question 34

When is AR suspected after a FECRT?

Answer 34

When the percentage reduction in FEC of a test group compared with the controls is <95%

Question 35

What happens in a simpliefied FECRT?

Answer 35

The pre-dose FECs aren't performed, results are just based on percentage reduction in mean FEC in treatment groups versus controls.

Question 36

What are LDTs and HEAs?

Answer 36

Larval Development Tests - for 1-BZ and 2-LV anthelmintics | Egg Hatch Assays - for 1-BZ anthelmintics

Question 37

How does AR vary on a farm?

Answer 37

season, worm species present at time of teset and test's specificity and sensitivity in detecting resistant alleles in worm population

Question 38

What are the SCOPS guidelines?

Answer 38

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).

Question 39

Where to inject an anthelmintic?

Answer 39

SUBCUTANEOUS - skin of neck under ear by 10-15cm, 1.6cm needle MUSCULAR - mid neck with 2.5-4cm needle aiming upwards and inwards