RHS Parasitic Worms Quiz – the Answers!

By Jenni McIntyre

We hope you enjoyed the Royal Highland Show. Thanks for taking the time to do the quiz – please find the answers below. For anyone who missed the quiz or the show, here is the online version.

Parasitic gastroenteritis is arguably the primary production limiting disease of sheep in the UK. How much do you know about it?

1. Parasitic gastroenteritis is caused by:

a. Fluke (trematodes)

b. Viruses

c. Roundworms (nematodes)

2. What is the main nematode worm causing parasitic gastroenteritis in lambs in the summer?

a. Teladorsagia (Ostertagia)

b. Oesophagostomum

c. Trichostrongylus

3. In the Springtime which nematode worm can cause diarrhoea and sudden death in lambs?

a. Teladorsagia (Ostertagia)

b. Cooperia

c. Nematodirus

4. How can we diagnose parasitic gastroenteritis?

a. History and examination

b. Postmortem

c. Faecal egg count

d. Rule out other causes of diarrhoea

e. A combination of the above

5. How many anthelmintic classes are there available to treat parasitic gastroenteritis in sheep?

a. 1

b. 4

c. 5

d. 7

6. Worms are able to develop or acquire resistance towards anthelmintics, making them less effective. How many of the available classes of anthelmintics have had reports of resistance in Europe?

a. 1

b. 2

c. 3

d. 4

7. How can we assess the efficacy of an anthelmintic on a farm?

a. Do a faecal egg count

b. Do two faecal egg counts (faecal egg count reduction test)

c. See if diarrhoea stops after treatment

d. See if mites die after treatment

8. A faecal examination usually reports a Nematodirus egg count, a Strongyle egg count and notes any Coccidia species present. A strongyle egg count is what is used to help diagnose parasitic gastroenteritis in sheep. Strongyle eggs all look very similar. Roughly how many different species of strongyle worms are there?

a. 1

b. 3

c. 6

d. 9

9. ‘All strongyle species are equally likely to cause disease’

a. True

b. False

10. ‘A lamb with a high egg count may not necessarily need treatment’

a. True

b. False

Strongyle egg counts can be useful in confirming a disease suspicion and examination of faeces is very helpful in deciding, for example, between anaemia due to fluke and anaemia due to Haemonchus.

Every treatment given selects for resistant worms in the sheep. Worms on the pasture are ‘safe’ and are said to be ‘in refugia’ – they are not affected by the anthelmintic. However, over time the number of resistant larvae on pasture increases and the number of susceptible larvae decrease as the sheep are repeatedly treated with anthelmintic on the holding.

A faecal egg count reduction test can give some indication of how well an anthelmintic is performing, but it uses a strongyle egg count with no knowledge of which species are present – highly pathogenic species may not be affected despite a reduction in egg output! It is important to gain a fuller understanding of what is happening on the farm.

Some farmers are now tending towards breeding resistant or resilient lambs which are less affected by the parasites and require fewer treatments. Others are using Targeted Selective Treatment to reduce anthelmintic use and preserve susceptibility amongst the worm population on the farm so the anthelmintic remains better effective for longer. By recording treatments they are able to choose breeding replacements which are hardier and more productive, improving their flock.

It is time to think about controlling parasites this year in such a way that we can still control them next year too.

1. c (Roundworms), 2. a (Teladorsagia), 3. c (Nematodirus), 4. e (A combination of the above), 5. c(5), 6. d (4), 7. b (Do two faecal egg counts), 8. d (9), 9. b (False), 10. a (True)