Are worms eating into your margins?

Worms are a well-recognised challenge in the pig industry and producers are all too familiar with the adverse side effects of parasitic burdens on herd performance, efficiency and overall farm profitability. Emer McCrum tells us more.

Worm control programmes are therefore well established with most units incorporating routine treatment and prevention measures as part of their herd health programme. However despite widespread awareness and ongoing management, slaughterhouse results continue to show evidence of roundworm or Ascaris suum infection in pig populations. Recent post-mortem inspection results from over thirty Irish herds collected during summer 2026 found 20% of livers examined had characteristic milk spot lesions. This raises an important question for producers: if the risks are well understood and treatment routinely administered, why are we still seeing evidence of infection at slaughter?

The crux of the issue lies in whether existing control programmes are consistently effective. To investigate your own situation, start with the breeding herd. Breeding animals play a critical role in the introduction and persistence of worms within the herd. Even if grower pigs are well managed, poor control in the breeding herd can act as a silent reservoir of parasites, continuously contaminating the environment and reinfecting younger pigs. To break this cycle and eliminate exposure of grower animals to infection, consider the following measures:

• Sows: Treat sows ideally in the service row or alternatively in the dry sow house a minimum of two weeks pre-farrowing. Sows carrying a worm burden into the farrowing house can contaminate the environment through the shedding of eggs, exposing piglets to infection from an early age. Treating sows upon entry to the farrowing house does not immediately eliminate this risk. Ensuring sows are treated in advance of farrowing is an essential step in reducing environmental contamination and limiting piglet exposure to worm eggs.
• Gilts: Maiden gilts must be treated in the finisher house a minimum of two weeks prior to transfer to breeding accommodation. This will eliminate the introduction of a fresh reservoir of worms to the breeding herd on an ongoing basis. Maiden gilts can act as a ‘canary in the coal mine’ when it comes to the existing worm burden. If there is evidence of infection in gilts, it is a good indicator of wider environmental contamination and a potential worm challenge for the growing herd.
• Boars: Don’t forget to routinely worm boars as while easily overlooked, boars can harbour and spread worms.

In terms of growers, while slaughter reports provide a useful indication of exposure, this is not the full story when it comes to worm burdens in the growing herd. Faecal egg count testing is a useful tool to establish the presence and level of infection and to determine the need for treatment. It is relatively straightforward to carry out with results available within a short timeframe. The findings can help inform targeted treatment and control programmes, ensuring interventions are appropriate to the level and type of infection while reducing the risk of anthelmintic resistance.

If a problem is identified in the growing herd, treatment may be necessary for a period to help break the cycle of infection. This however should be viewed as part of a wider control strategy rather than a permanent measure. Once the sow herd is effectively controlled and the introduction of worm eggs into the farrowing environment is minimised, the need for routine treatment of growing pigs may be reduced or in time eliminated. Consult with your veterinary practitioner to assess the specific situation on your unit.

Worm control programmes should not depend solely on anthelmintics. The biggest challenge with controlling worms in the pig environment is the exceptionally tough outer shell of the egg which enables survival for years in favourable environmental conditions. Operating houses all-in-all-out with thorough removal of organic matter, washing, disinfection, drying and ideally resting between batches is the gold standard. Washing alone will not kill worm eggs but the complete removal of organic matter using high pressure washing particularly in difficult to clean areas such as pen corners, feeders and drinker surrounds where eggs build up, is required to remove worm reservoirs. Worm eggs require moisture to survive so thorough drying of houses after washing while slow, is very effective. Some disinfectants are effective against worm eggs however applying disinfectants without thorough washing is largely pointless. Switching disinfectants regularly on farm (every six months) will help to minimise the development of resistance. Good manure management and control of fly and rodent populations is recommended.

A recent study estimated the cost of roundworm infection at €5 – €8/pig driven by reduced feed conversion and lean meat content, plus increased susceptibility to respiratory pathogens. With feed costs continuing to place pressure on production margins, these potential losses are simply too significant to ignore. Worm control is therefore not simply another veterinary expense. It is an investment in feed efficiency, growth performance, herd health and factory returns. The key question to consider is not simply whether you worm your pigs, but whether your current worm control programme is actually protecting your herd health and profitability.