Spring Advice From Our Veterinary Parasitologist Expert
Professor Jacqui Matthews, RCVS Recognised Specialist 

Spring Worm Control Advice

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Modern parasite control should focus on risk assessment, diagnostic testing and targeted treatments - but only when necessary. And any parasite control should always be supported by excellent pasture management.

 

Blanket worming should be avoided to protect horse health while helping to slow the development of wormer resistance.

 

Risk assessment

The first step in any spring parasite control plan should be a risk assessment. Factors to consider include the horse’s age, historic management and grazing practices, as well as previous parasite test results from the individual and any horses it grazes with. The free online tool What’s Your Worm Risk provides a structured and practical way for owners and professionals to assess the risk and support evidence based decision making.

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FEC testing

Horses with consistently low faecal egg counts (FECs) and good pasture hygiene are often at low risk of worm infection, while young horses, especially those grazing paddocks with high contamination, are particularly at risk of higher worm burdens and disease. As grazing increases in spring, rising temperatures in the UK have important 
implications for parasite transmission. Warmer conditions allow pre-parasitic stages of worms to develop more quickly on pasture, shortening the time between eggs being shed in dung and infective stages becoming available to grazing horses.

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This increases the risk of pasture contamination, making spring monitoring and test-led treatments particularly 
important. The main parasites of concern in spring are small redworms. FECs are recommended in early spring to identify horses actively shedding eggs onto pasture. Generally, horses shedding 200 eggs per gram (epg) or more in dung should be considered for worming, while those with lower counts do not require treatment. Treating horses based on FEC reduces pasture contamination without overuse of wormers. It is important to assess effectiveness of treatments, with follow up testing 10 to 14 days after worming to confirm efficacy and monitor ongoing risk. 

 

FECs have low sensitivity for detecting tapeworms but antibody tests of serum  and saliva are highly sensitive.

 

Tapeworm testing

Tapeworm development also increases in spring due to the activity of their intermediate hosts, oribatid mites, which become more active on paddocks. Spring antibody testing is therefore crucial and identifying infected horses early allows treatment of test-positive individuals, preventing egg shedding, reducing mite infection on pasture and breaking the tapeworm lifecycle. In the UK, of more than 300,000 horses tested using the tapeworm saliva test, EquiSal, only one in three tested required treatment, demonstrating that testing significantly reduces unnecessary wormer use.

 

Pasture management

Finally, good pasture management should underpin every parasite control programme. Regular poo-picking two to three times a week, avoiding overstocking and sensible grazing rotation can significantly reduce worm transmission. Effective pasture management means fewer horses will test positive, further reducing the need for wormers