Over the last two weeks or so, the weather has finally become good and grass growth rates are on the rise.

This, in turn, has seen the majority of farmers let their ewes and lambs out to pasture and take their minds off what has been a terrible February and most of March in terms of weather.

However, despite the good weather, two parasites known as coccidia and Nematodirus can cause problems for young lambs at this time of the year.

These parasites can affect lambs at a similar age and stage of the year and can have serious health implications – in some cases leading to death – in lambs.


Nematodirus┬ácan cause problems for lambs that are between four and 12 weeks-of-age. Lambs can become infected when the eggs – of this parasite – overwinter on grass from the previous grazing season.

These eggs – when exposed to cold weather conditions followed by warm conditions – will hatch. By the time these eggs hatch, it coincides at a stage where lambs are consuming large amounts of grass – which makes them very susceptible to picking up this parasite.

Once a lamb is exposed to the parasite, the larvae will damage the lining of the intestine, resulting in diarrhoea, dehydration, weight loss and, if left untreated, death.

The best way to prevent lambs from becoming infected is through the use of anthelmintic drenches. According to Teagasc, there is no evidence of anthelmintic resistance in the case of Nematodirus to any of the drug classes on the market. Therefore, a white drench should be used to treat against the parasite.

Lambs will generally develop immunity once they reach 10 to 12-weeks-of-age.


Coccidiosis occurs when lambs become infected orally from faecal contamination of bedding, water troughs or feed troughs.

In most cases, coccidia affect lambs from three weeks-of-age up to eight weeks-of-age.

Lambs are protected by antibodies in the colostrum for the first three weeks of life and they develop resistance to attack – from this parasite – at about 10 weeks-of-age.

Lambs become infected when they ingest coccidial oocysts, which penetrates the gut wall where it burst and causes damage – leading to the lambs becoming sick.

Lambs that are infected will develop a scour – which may contain blood or is black in colour. Furthermore, lambs may show signs of straining and appear empty and dehydrated.

It is best to talk to your local vet about what treatment should be used to treat any infected lambs. Otherwise, a number of management practices can be carried out to limit the number of coccidial eggs present on pasture.

In terms of the lambing shed, it is vital that pens are kept clean and dry. As ewes and their lambs move outdoors, keeping areas around drinkers and feeders clean and dry will help to reduce the number of coccidial eggs present on pastures.

If possible, lambs that are similar in age should be batched together. However, this may not be practical to do on every farm.