PARASITE FORECAST December 2016 – Summary

Local farm conditions may change, consult your vet. Effective worm control should be part of your veterinary health plan.

For the full forecast please go to www.nadis.org.uk

On the first day of the month a shallow depression tracked east across Wales and then England, bringing some rain, but after that all parts of the UK became predominantly dry, as high pressure took charge. For much of the time the high was centred over Scandinavia, bringing easterly winds, and restricting temperatures to near the seasonal average but with plenty of sunshine, especially in western areas. As the second week of the month progressed, increasing numbers of showers encroached from the east, and around 15th-17th the weather was more generally unsettled with a depression making its influence felt. Thereafter there was again a build of pressure, giving mostly fine weather, though fog affected parts of England and Wales, particularly in the south, while frontal systems affected north-west Scotland as the month approached its end. The last four days of the month were notably mild over much of England & Wales (www.nadis.org.uk).

PARASITIC GASTROENTERITIS (PGE)

Outbreaks of trichostrongylosis in store and replacement lambs, and even gimmers, are a risk during mild wet weather in November and December. Heavy infestations cause black foetid diarrhoea and rapid weight loss.

As the weather becomes colder, most acquired Haemonchus larvae will arrest their development in the abomasal wall of the host sheep resuming development again in the spring if sheep are left untreated. Treatment will be indicated in those flocks with a history of haemonchosis; note that arrested larvae will not produce eggs so faecal examination may yield a negative result.

It would be prudent to test faecal worm eggs counts of rams after the mating period as weight loss may render them more susceptible to larval challenge/development.

Trichostrongylosis in store and replacement lambs is a risk after mild wet weather in early winter; the lamb on the right has a severe louse infestation. How would you classify the parasite control on this farm?

Weight loss over the mating period may render rams more susceptible to larval challenge. Consider testing faecal worm eggs counts of rams after the mating period, and supplementary feeding.

Liver fluke in sheep

Where a second triclabendazole treatment has been required in the higher-risk, western regions of the country, the next fluke treatment can probably be delayed until January when closantel or nitroxynil should be used.

Albendazole and oxyclosanide are effective from 10-14 weeks post infestation and can be used when treatment is recommended to remove adult flukes in late spring (often in May).

Liver fluke in cattle

Out-wintered cattle considered at risk should be dosed for fluke with a product with some activity against immature fluke.

Housed cattle, if not already dosed after housing, may be dosed with closantel or nitroxynil (when housed for 6-7 weeks or more) or a benzimidazole such as albendazole (when housed for 12 weeks or more), thereby avoiding the use of triclabendazole and reducing selection pressure for resistance.

There are benefits associated with treating cattle at housing as this will immediately remove the impact of developing and adult flukes on growth and feed efficiency. Where this approach is practised, cattle should be tested later in the housing period for the presence of adult fluke, or given a second treatment to ensure all fluke are removed. The interval between housing and testing or re-treatment will depend on the product used – seek advice.

Faecal egg counting, serum or bulk milk ELISA testing, and slaughterhouse liver reports, are practical methods of detecting fluke-infected herds.

Slaughterhouse liver reports are a practical means of detecting fluke-infected herds and flocks.

CATTLE NEMATODES

Autumn-born beef calves should not require anthelmintic treatment at housing.

Ostertagia larvae ingested by susceptible yearling stock during the autumn may have halted development and over-winter (as early L4) in the abomasal (stomach) wall.

These larvae resume their development in late winter/spring and can cause outbreaks of acute scour with subsequent death (type 2 ostertagiosis).

Susceptible animals exposed to contaminated pastures during the later grazing season will be at risk from type 2

ostertagiosis unless they have been dosed with a anthelmintic effective against inhibited larvae, at housing, or at least before late winter.

Lungworm outbreaks decrease significantly from November onwards. Coughing in unvaccinated susceptible cattle at pasture before housing, or in un-dosed stock after housing, should be investigated for the possibility of lungworm larvae in faecal samples.

Parasite Control should be part of your veterinary health plan, consult your vet

Parasite Forecast

December

NADIS

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