The Agri-Food and Biosciences Institute (AFBI) veterinary sciences division in Northern Ireland issued a spring 2025 nematodirus warning on Friday. “Using a forecasting system based on climate data, staff at the institute have determined that hatching of nematodirus eggs has already commenced and that 10 % of the annual hatch would have occurred during the second week of March 2025," the report stated.
The Agri-Food and Biosciences Institute (AFBI) veterinary sciences division in Northern Ireland issued a spring 2025 nematodirus warning on Friday.
“Using a forecasting system based on climate data, staff at the institute have determined that hatching of nematodirus eggs has already commenced and that 10 % of the annual hatch would have occurred during the second week of March 2025," the report stated.
"The current meteorological readings indicate that peak hatching would have taken place during the period from 25 March to 3 April 2025.”
The warning, compiled by Paul-Emile Kajugu and Bob Hanna from the AFBI parasitology section, advises sheep farmers of the likely risk of nematodirus worm infection in young lambs occurring at this time of the year.
Lambs grazing the same pasture in the previous year were the source of the contamination, with eggs hatching following a period of cold weather followed by warmer conditions.
It warned that affected lambs can develop profuse scour and die rapidly.
Alert
“Nematodirus normally only affects lambs between six and 12 weeks of age and clinical signs usually appear two weeks after ingestion of large numbers of larvae.
"Although rare, nematodirus infection can occasionally cause problems in young calves. Therefore, farmers should be on the alert for signs of scour in lambs (and possibly young calves at grass) from mid-April into May.”
The warning also cautioned farmers that nematodirus infection can be confused with coccidiosis, another disease which can cause severe scour in young lambs.
As such, it is important to accurately identify the cause of scouring with the veterinary section advising farmers to follow veterinary recommendations.
Two practices are highlighted to avoid or reduce the disease in young lambs by:
Not grazing lambs on the same fields as those grazed by lambs of a similar age last year.Using anthelmintic drenches every two to four weeks. The interval between doses depends on the particular anthelmintic used and the severity of infection. To date, only limited evidence has been found of drug resistance in nematodirus to any of the available classes of anthelmintic.Added concern
Additional concerns raised for sheep farmers include the possibility that Haemonchus infection may be prevalent among growing lambs in the summer months.
“Last year, an unprecedented localised increase in haemonchus infection in sheep was noted, likely linked to the mild wet climatic conditions.
"As a result, pasture in affected areas is likely to be contaminated by parasite eggs surviving from last season and yearling animals are likely to be carrying hypobiotic larvae, which will be a source of infection for growing stock later in the season.
"Haemonchus infection causes profound anaemia in lambs, often with scour which may be blood-stained. Animals succumb rapidly and numerous losses can occur in affected flocks.”
The AFBI recommends farmers contacting their veterinary surgeon “at an early stage".
"He or she is in an ideal position to provide advice on the prevention and/or treatment strategy best suited to your particular circumstances.
"[The] AFBI’s veterinary sciences division can test faeces samples from sheep or cattle to determine the level of worm eggs present. A minimum of 5g of faeces from each animal is required for this test.
"Any animals which die showing signs of bloody scour and/or anaemia should be submitted for post-mortem examination and testing for haemonchosis.”
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