Ascaris suum

Causal agent	Ascaris suum – the large round worm of pigs The adult worm is large the female is 20-40 cm long and the male slightly shorter at 15-20 cm. The adult female may lay 2 million eggs per day. An adult can live 6 months
Life cycle		Day Zero 2-3 3-7 8-10 10-15 21-30 10 13-18	Egg+L3 stage ingested and swallowed L3 hatch from egg in intestines L3 penetrate intestine wall and migrate to liver L3 migrate from liver to lung L3 leave lung, coughed up and swallowed L3 develop to L3 in intestines Young adult develop Eggs are passed L1 develop in 10 days L2/3 develop in 13-18 days Prepatent period 40-52 days
Age group	Affects all age groups of pigs
Clinical signs
Normally	No clinical signs. May be some reduction in growth rates due to competition between pig and worm for food.
Acute pneumonia	Ascaris, during the lung phase, may result in an asthmatic cough and the pig may have problems breathing. Ascaris will exacerbate other pneumonic conditions, especially swine influenza.
Intestine	In young pigs severe infestation may results in intestinal blockage, rupture and death
Infectivity
	The eggs are very infective. They are extremely resistant and can survive for more than 7 years in the environment. Generally disinfectants have little effect on the eggs. However, steam cleaning and direct sunlight will kill the eggs.
Transmission
	The eggs are extremely sticky and will be easily transported onto the farm by pigs, insects, birds and equipment
	Note workers boots are a significant source

Post-mortem Lesions
Liver	“White spot” on the liver develop within days of infestation. However, they heal within 25 days
Lung	Small lesions may be seen in the lung, easier on histology
Intestine	The presence of the adult worms may be seen in the intestine lumen
“White spot” in the liver – severe case		Heavy worm infestation in the intestine – seen at slaughter
Diagnosis
	White spot on liver in the slaughterhouse or at post-mortem
	Presence of adult worms post anthelmintic treatment
	Worm eggs seen during faecal examination using flotation technique. Note Ascaris eggs require ZnSO4 flotation; normal salt solution will not work. In addition, they may still be difficult to find.
Egg in flotation			Adult worms seen after worming the pig
Treatment
Anthelmintics	Many anthelmintics work against Ascaris larvae and adults
	The problem with treatment is the rapid re-infestation and lesions heal within 25 days. Withdrawal times may preclude use prior to slaughter
	The adult worm in the gut does reduce the development of future larval migration
Common differentials
	Stephanurus dentatus (kidney worm) in the early stages may result in a “milk spot” liver. Later stages liver damage much more severe
Zoonotic
	No zoonotic implications. The human Ascaris lumbricoides worm is a separate species