Preventing Nematodirus this spring
by Matt Blacklidge, Business Development Manager - Piercebridge
Nematodirus can cause high mortality in lambs and impact growth rates if not monitored and managed correctly.
Unlike other worms it has a different life cycle and in certain climatic conditions can strike very quickly, often with little or no warning. It is critical to remain vigilant and use an appropriate anthelmintic when necessary.
Nematodirus can strike rapidly because infective larvae develop within the eggs, meaning infection can pass from one lamb crop to another. Lower temperatures can delay egg hatching. When there is a period of cold weather followed by warmer weather of 10˚C or more, it can lead to a mass hatch. If this hatch coincides with lambs beginning to graze, the results can be devastating.
Assessing the risk
Unlike other sheep worms, faecal egg count tests are not as reliable because the damage is done by large numbers of immature larvae which aren’t producing eggs.
This means rapid action must be based on a risk assessment, as losses will occur once symptoms are visible.
The risk assessment can include the following:
1. Signing up for the Sustainable Control of Parasites in Sheep (SCOPS) Nematodirus Forecast will alert you of a risk in your area based on local weather conditions.
2. If you have lambs aged six to 12 weeks old and there’s a history of nematodirus on your farm, or you have bought in animals that may have been carrying nematodirus eggs, your stock could be under threat.
3. Lambs under stress, with triplets or additional parasite burdens like coccidiosis, could also be at risk.
Reducing the danger
Graze lambs on clean pasture not grazed by other lambs last year. If grazing low-risk pasture isn’t an option and your stock is at high-risk based on your risk assessment, then protect them with a suitable anthelmintic drench.
Most groups of sheep drenches are still effective against nematodirus, despite widespread resistance to other worm species detected for the oldest three groups of wormers on the market. However, white drench remains the most suitable option for nematodirus, in terms of saving the other anthelmintic groups for worms encountered later in the season. Stock may need to be treated more than once, depending on the spread of ages and risks in your area.
To safeguard the future use of all anthelmintics, stock must be wormed according to the manufacturer's guidelines, coupled with advice from your RAMA or vet.
It is advisable to regularly calibrate your dosing gun, even if it is brand new, to avoid the risk of over or under dosing.