Ascaris Suum The Pig Farmers Enemy

The ascarid worm of pigs is Ascaris suum. Infestations are easy to recognize, especially at slaughter where the presence of these large worms with lengths of 15-41cm are easily detected in the small intestine. More obvious however are the white spots on livers called “milk spots” caused by migrating larvae of these worms.

The life cycle is interesting and complex. Adult females lay anything between 100 000 and 2 million eggs per day. These are extremely resistant and will survive for 5 years and longer in the environment. Eggs are voided in faeces and become infective after 30-40 days. They are taken up from the environment by mouth and hatch in the stomach and small intestine. Within hours the larvae migrate to the liver and cause haemorrhage there. Once a blood vessel is found, the larvae circulate via the right heart chambers to the lungs. From the capillaries the worms migrate across to the alveoli and are coughed up from the air passages and swallowed to develop into adults in the small intestine. Larval migration only takes 10 days, but egg laying adults are only present 7-9 weeks after ingestion of eggs. Eggs have a special ability to adhere to the skin and hair of sows especially to sow udders. This is obviously important for the mode of transmission to her litter.

A strong immune response is activated leading to appearance of milk spots. So by no means will all larvae develop into adults. These again disappear within 40 days of a single infestation. Obviously, these spots will continue to be present if worm eggs are taken up continuously.

The importance of this worm is the effect on Feed Conversion Rate (FCR) and Average Daily Gain (ADG) which are all negatively affected. The worst effects are seen as a result of larval migrations causing liver damage and pneumonia. Adult worms are usually not a problem provided the pigs are well nourished. In large numbers, the adults may cause bowel obstruction or they migrate up the bile duct to cause jaundice as a result of the obstruction to the bile flow.

Dutch figures comparing infested to non-infested pig farms across the whole country showed on average 33 grams carcass mass loss per day ie. almost 5kg over 150 days! In papers submitted to the 15th IPVS congress an improvement of 50grams live weight gain per day and an improved FCR of 0.24 was encountered 1 year after starting a deworming program. It is clear that the economic impact of worms on pig production is vast.


The normal control in most of our farms is to deworm sows roughly twice a year together with mange treatments. However, once weaner and grower accommodation has been contaminated, controls become more complex and costly.

A two pronged approach is necessary:

  • Removal of worms from the animals and preventing adult egg laying females from contaminating the pigs environment.
  • Killing off of worm eggs in the piggery with a suitable chemical in between batches and better hygiene by regular removal of dung.


It is important to note that deworming programs may vary depending on circumstances on different farms – Please consult your veterinarian.

Sows and Boars: an endectocide given by injection or in-feed every 6 months at least. It is important to treat replacement gilts and boars on arrival unless specifically done by the seller. (Endectocides – doramectin, ivermectin, abamectin)

Weaners: endectocide at weaning as for sows. In-feed premix is the most popular method and is given continuously for at least 7 consecutive days.

Growers at 10 weeks: endectocide injection 1ml per pig or flubendazole in ad-lib feed for 2 full days.

17 weeks of age: flubendazole in ad-lib feed for 2 consecutive days or other anthelmintics. (Discuss with your vet)

All of these products kill the migrating larvae and adult worms. As the life cycle is 7-9 weeks, no egg laying females can be present before the 25th week of age by which time your pigs should all be sold already. Beware of slow growers and replacement gilts selected on the farm. These should be treated again at 24 and 31 weeks of age.

Worm eggs are killed off by using “Neopredisan” as the final disinfectant between batches of pigs. With this combination of deworming of animals and disinfection to kill off the worm eggs, total control should be achieved within 2 pig cycles with a substantial return on investment and a huge knock to the erosive effects that worms have on your profit!

Date published: 2006-03-23

Dr EF Ortmann