Pig producers should maintain extra vigilance over their worming strategies during the coming months to combat the seasonal increase in Ascaris suum – the number one worm problem affecting both breeding and slaughter stock.

The incidence of “milk spot” in slaughter pigs – indicating worm infestation by spotting on pigs’ livers – has consistently shown this seasonal rise since monitoring began under the British Pig Health Scheme.

Ascaris suum

Ascaris suum, which is a white roundworm, is the pig producers’ primary and most virulent parasite. Its egg-laying capacity can run to several hundreds of thousands of eggs in one day, leading to rapid contamination of pasture and buildings.

The ability of the Ascarid eggs to survive for many years highlights the importance of maintaining a strict approach to worming, say vets.

Of the range of pig endoparasites – including kidney worm, lung worm, nodular worm, muscle worm and red stomach worm – the white roundworm Ascaris suum is the most virulent. It can cause poor growth, low food conversion, greater susceptibility to disease and, in some cases, death resulting from blockage of the bile duct.

And as we move into summer, Richard Pearson of the George Vet Group in Wiltshire emphasises the importance of pig producers assessing their worming policy and making sure it’s effective.

“If producers are running into problems now, at the start of the summer, things will only get worse unless they discuss their worming strategy with their vet and adopt a more-effective approach. The development of the oocysts of Ascaris suum on the ground, and the timescale needed to complete the life cycle, become much shorter during the summer.

“The challenge becomes greater as the weather gets warmer – and it’s pigs on high-welfare, outdoor systems that are most vulnerable to parasitic infection,” he says.

While Mr Pearson doesn’t believe that resistance to worming treatments is a major factor in individual herds suddenly finding they face an increased worm problem, he reckons it’s more often caused by a failure to regularly monitor and review worming policy.

“Things can easily get away from you if the worming policy isn’t carefully scrutinised. There’s no time for complacency with a worm like Ascaris suum – and if it gets a hold, it’s a very difficult job getting on top of things again. It can take years to bring the situation under control.”

Worm treatment

“Routine disinfectants are not effective against Ascarid worm eggs and for outdoor systems is important to keep pastures “clean” by maintaining worm-free pigs. Once pastures are contaminated and there is nowhere else to move pigs to, a producer can be in for a very hard time indeed,” says Mr Pearson.

But he says the biggest misconceptions among pig producers about Ascaris suum is an assumption that it can be “nailed” with worm treatment, when the problem has been initially highlighted by “milk spots” on condemned livers.

“The milk spot is scar tissue on the liver and is caused by the migration of the larvae through the liver, which happens within a few days of the pig ingesting infected eggs through the lining of the gut and ultimately into the liver. So if pigs are in infected buildings and on infected ground, unless they are on wormer permanently, milk spots will still occur.

“Identification of milk spots should trigger an intensive programme of worming and cleaning, but their occurrence means the pigs have been in infected buildings or on infected pasture within the preceding six weeks. The aim should be to stop the milk spot occurrence getting and worse and to beat it over time using hygiene.

“But a regular worming programme that treats pigs every five to six weeks is essential – that’s the length of time of the life-cycle of Ascaris suum – for growing and finishing pigs in an effort to break the cycle,” advises Mr Pearson.

Prevent buying in worms

The importance of isolating all incoming pigs to a unit is still not fully appreciated in terms of its impact on worm control, adds BPEX senior veterinary programme manager Katrin Turvey.

“Even though pigs may be regularly coming into a herd from a known and reputable source, there is still no guarantee they won’t be bringing worms on to your unit – and that’s still the case if the supplier has his own worming programme. A producer could just be unlucky and bring in a gilt with a heavy worm burden. The breeding companies have to rear gilts on straw and the welfare-friendly environments are ideal for parasites,” says Ms Turvey.

She admits it’s a message that is always being “hammered home” to pig producers, but stresses that it must not be underestimated in its ability to prevent an unexpected worm problem.

“Isolation should be for six weeks, depending on the diseases you are most concerned about, but we advise that pigs should be wormed before introduction into the herd and then when they come into the herd.”

The Pig Health Improvement Project provides producers with free British Pig Health Scheme reports from abattoirs, which identify parasitic infection through the milk spot scoring of condemned livers.

“All producers should study these reports and do a health check status of the herd, in readiness for consultation with the vet over worming policy. It isn’t difficult to achieve a good level of worm control, but that won’t be achieved by worming pigs once a year. Breeding sows need worming three times a year,” says Ms Turvey.

Case Study Jim Burling, Norfolk

Norfolk-based large-scale pig producer Jim Burling has been operating the same worming programme for 30 years – and it works.

“When we started this system it was at a time when we were buying in pigs from different sources and worms were a bigger problem. But we’ve stuck with it ever since,” says Mr Burling of East Anglian Pigs.

All sows – there are several indoor and outdoor herds – are wormed twice a year on a programme that works in close association with Elanco. The business produces weaners which are moved to contract finishing units at 10-12 weeks old and are wormed on arrival.

“If we take on a new finisher and there’s a worm problem, we’ll treat the pigs two or three times during the finishing stage,” says Mr Burling. All worm treatments are administered “in-feed”.

“The key to an effective worming programme is to set up a system that fits in with the life cycle of the worm, so that it can do its job. Providing it’s planned under the guidance of the vet, done at the right time and at the appropriate gap in the cycle of the worm, it will keep on top of the problem. Our milk spot levels are extremely low across all the pigs we produce,” says Mr Burling.