Worm species in pigs and their control

This Note briefly describes the major worm parasites of pigs, their life cycles, their effect on the animal and their importance and control.

Large roundworm

The large roundworm (Ascaris suum) is found in the small intestine of pigs and can grow to 400 mm long and 7 mm thick at maturity. Heavily infested pigs may have up to 250 worms blocking the small intestines and the bile duct causing loss of appetite, vomiting and death. In less extreme cases there is reduced appetite, poor feed efficiency and slow growth. Pigs 6 to 12 weeks old are the most seriously affected, while mature pigs may carry the worms without ill effect. Growth rate and feed efficiency can be depressed by up to 10%.

The female roundworm is estimated to produce more than 300 000 eggs per day which are passed in the dung of infected pigs. The eggs can survive for years in moist conditions to infect other pigs.

Larvae (immature forms) reach the liver after hatching from eggs in the small intestine and passing through the gut wall. Liver damage is seen as white 'milk' spots on the surface of the organ. Entering the bloodstream, larvae reach the heart and then the lungs where they may cause a low grade pneumonia. After being coughed up and swallowed they mature in the small intestine.

The cycle from egg to egg production is completed within 2 months. The parasite is confirmed in a herd by presence of eggs in the faeces and evidence of liver damage (milk spot) at slaughter.

The large roundworm is the most common and the most economically important internal parasite of pigs in Queensland. Improved control methods have reduced its effect - now only approximately 3% of the pigs slaughtered in Australia show signs of having been affected by this parasite (as indicated by the Pig Health Monitoring Scheme ).

Kidney worm

The adult kidney worm (Stephanurus dentatus) grows to 50 mm in length and is located in fibrous cysts in the pig's kidneys, uterus, flare fat, loin muscles and sometimes the spinal cord. As well as the adult worms the cysts contain a greenish pus. The immature or larval form is often found in the liver.

The migrating larvae damage the liver. Where the damage is severe, affected pigs stop growing, build up fluid in the body cavity and may die of liver failure. When cysts develop in their spinal cord, adult animals may show paralysis of the hindquarters. Female worms in cysts with openings into the ureters and the kidneys can shed up to 1.5 million eggs in every urination. Blood is often passed in the urine.

Eggs hatch and after two moults the infective third stage larvae is reached in about 4 days. Both eggs and larvae are destroyed by sunny dry conditions or by extreme cold. Larvae can survive 3 to 5 months in warm moist soil sheltered from sunlight. If ingested by earthworms, larvae remain infective for long periods even under adverse soil conditions.

The pig is invaded by infective larvae via the skin, or the stomach wall after ingestion. After moulting in the stomach wall or the skin they reach the liver where they move around in the tissue for 3 months or more, causing considerable damage. They then migrate principally to the kidney and surrounding tissues where females lay eggs about 6 months after infestation.

Some larvae, following an erratic migration path reach maturity in the pancreas, spleen, brain, spinal cord and other organs. Unborn piglets can be infected in this way.

Infestations occur mainly in pigs kept in paddocks or dirt pens which have not been regularly and systematically spelled. Improvements in piggery sanitation have diminished the importance of the kidney worm in Queensland. Diagnosis is made at post mortem by examination of the kidneys. Eggs will be found in the urine.

Sparganosis

The zipper tapeworm, (Spirometra erinacei) is significant because the second larval stage causes Sparganosis in humans. Humans risk contracting the disease if they eat feral pork infected with the immature form of the parasite.

The immature stage (spargana) are small white structures 8 to 15 mm in diameter resembling pieces of fat and are found on the lining of the body cavity, the diaphragm and on the heart and lungs. The affected pigs are condemned at slaughter, being unfit for human consumption.

The life cycle is complex and not fully understood. Adult tapeworms are found in dogs, cats, foxes and dingoes: the life cycle involves a water flea and other intermediate hosts. The spargana may be found in tadpoles, frogs, snakes, pigs and humans. In some areas of Queensland the parasite is found in feral pigs.

Whipworm

The whipworm (Trichuris suis and T. trichuria) is found in the large intestine of the pig.

The name comes from the resemblance to a whip, the long forward part being threadlike, the shorter rear portion much thicker. An adult measures between 30 and 50 mm. The worm can cause severe disease involving bloody diarrhoea and shedding of mucus. Affected pigs lose weight (up to 20%) and there can be a 10 to 12% death rate about 3 weeks after weaning. Swine dysentery symptoms are similar: the parasite may be implicated in the development of this disease. Whipworm infection should always be considered when there is diarrhoea with blood and mucus.

The life cycle is direct: the ingested eggs hatch and the larvae reach the lower gut without migrating through other organs. The eggs do not pass through any other host before becoming infective. In Queensland the disease is mostly seen in heavily stocked extensive piggeries. Eggs can remain viable for many years outside the pig and are easily identified in pig faeces.

Nodule worm

Two species may infest pigs, of which Oesophagostomum dentatum is the more common. The larval stage produces nodules in the lower small intestine and the large intestine. The adult is greyish in colour measuring up to 25 mm in length.

Nodule worm infestation can cause slight diarrhoea and can reduce growth rate. The damage leaves the intestines unsuitable for use as sausage casings.

After being passed in the dung, eggs hatch and larvae reach the infective stage in a few days. When swallowed by the pig the larva sheds its protective sheath and burrows into the gut wall, causing a nodule. It grows to maturity in the intestine after a period spent in the nodule. It is not an important parasite of pigs in Queensland. Diagnosis is by identification of eggs in faeces.

Thread worms

The worms (Strongyloides ransomi and others) are about 4 mm long and are found in the upper part of the pig's small intestine. They can cause enteritis, severe diarrhoea (often bloodstained), anaemia, poor growth and death. Piglets up to 8 weeks of age are most susceptible and death rates up to 75% have been reported.

Larvae gain access by skin penetration or are taken in through the mouth. Suckling pigs can be infected by larvae in colostrum. Dry conditions are hostile to survival of the larvae. The parasite is uncommon in Queensland. Diagnosis is achieved by identifying eggs in fresh faeces.

Red stomach worm

This reddish coloured worm (Hyostrongylus rubidus) is about 10 mm long and burrows into the pig's stomach lining.

The worms cause the stomach lining to bleed: digested blood may be seen in the dung and stomach ulcers can develop. Affected pigs lose condition, have a ravenous appetite, become very thin and may die. Adult pigs can die following a sudden blood loss when such ulcers perforate. The parasite is thought to be involved in ill-thrift and the 'thin sow syndrome'. It is uncommon in growing pigs. The life cycle is direct: pigs are infected when eggs are taken in from contaminated pasture or soil. The red stomach worm is not common in Queensland. Diagnosis is by identifying worm eggs in the faeces and/or by post mortem examination.

Lungworms

Three are known, Metastrongylus apri, M. pudendotectus and M. salmi. These are long white thread-like worms up to 50 mm long and can be found in the trachea and bronchial tubes of affected pigs.

Light infestations have little effect but heavier concentrations in young pigs may cause pneumonia and loss of condition.

Eggs containing active embryos are passed in the dung. The larva hatches but must complete its development after being swallowed by an earthworm. The pig is infected by eating the earthworm. Infestations are rare in Queensland. Diagnosis can be difficult as eggs are not easy to find in faeces. Post mortem is a more reliable method.

Thorn-headed worm

The thorn-headed worm (Macracanthorhynchus hirudinaceous) is whitish in colour, the females growing to between 180 and 400 mm long. The parasite firmly attaches itself to the small intestine wall with a thorn-like part on its head.

Although infestations are now uncommon in Queensland, the worm can cause severe damage as it moves and re-attaches itself to different parts of the gut wall. Occasionally the intestines are holed, resulting in peritonitis and death of the host pig. Eggs passed in the dung hatch in beetle grubs which are eventually eaten by the pig. The worms develop while attached to the intestinal wall.

Other worm parasites

Large stomach worms (Ascarops strongylina and Physiocephalus sexalatus) have similar life histories involving beetles as intermediate hosts. Both are stout pinkish worms up to 20 mm long and develop near the exit end of the stomach. Dung beetles are the intermediate hosts. The worms must be present in large numbers to cause problems.

Rare instances of sheep liver fluke (Fasciola hepatica) have been reported in the livers of pigs.

While pigs are not known to carry adult tapeworms, three types of  'bladder worm' or tapeworm cysts can infect pigs. Cysticercus cellulosae (pork measles) is the immature stage of the human tapeworm Taenia solium. The thin-necked bladder worm, Cysticercus tenuicollis is the intermediate stage of Taenia hydatigena, a tapeworm of dogs. The third type is the hydatid cyst, the immature form of a small tapeworm of dogs, Echinococcus granulosus.

The larvae of Trichinella spiralis causes Trichinosis, a public health problem in many parts of the world: it is not found in Australia. It can infest pigs, rats, mice, dogs, cats and other mammals including man. Swill feeding (banned in Australia) helps to spread infection.

Management control and prevention

In indoor systems where all-in all-out procedures are used, internal parasites will not build up in sufficient levels to require routine treatment. Sows housed in stalls that have no access to faeces are usually only at threat from large roundworm infection. Parasite control in indoor loose-housed sows is less predictable and depends on hygiene, drainage and regular removal of faeces. In outdoor herds, parasite control is more difficult to achieve through hygiene and spelling paddocks, and regular chemical treatment is often required.

Table 1. Chemical control of worms in pigs (registered at time of note review). Always check the label before use of control product - follow the directions for use and the withholding period instructions.

Components	Product Name	Company Code	Pest	Application Rate	Whp (days)
abamectin
(10mg/mL)	AMEC ANTIPARASITIC INJECTION FOR PIGS	APX	Intestinal threadworm, Kidney worms, Large roundworm, Lungworm, Nodular worm, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	1mL/33kg bodyweight	21
(10mg/mL)	VIRBAMEC ANTIPARASITIC INJECTION FOR PIGS	VIR	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	1mL/33kg bodyweight	21
doramectin
(10mg/mL)	DECTOMAX INJECTABLE ENDECTOCIDE	PFI	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodule worms, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	0.3 mL/10kg bodyweight	35
ivermectin
(10mg/mL)	BOMECTIN ANTIPARASITIC INJECTION FOR CATTLE & PIGS	PHA	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	1mL/33kg bodyweight	28
(10mg/mL)	CEVAMEC ANTIPARASITIC INJECTION FOR CATTLE & PIGS	PHA	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	1mL/33kg bodyweight	28
(10mg/mL)	IVOMEC (IVERMECTIN) ANTIPARASITIC INJECTION FOR PIGS	MER	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	1mL/33kg bodyweight	28
(10mg/mL)	NOROMECTIN ANTIPARASITIC INJECTION FOR CATTLE AND PIGS	NOR	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Whip worm (also Pig louse and Scabies (Sarcoptic mange) mite)	1mL/33kg bodyweight	28
ivermectin
(6g/kg)	IVOMEC (IVERMECTIN) PREMIX FOR PIGS	MER	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Stomach worm (also Pig louse and Scabies (Sarcoptic mange) mite)	0.333-1.66kg/tonne feed (see label)	7
(6g/kg)	NOROMECTIN PREMIX FOR PIGS	NOR	Intestinal threadworm, Kidney worm, Large roundworm, Lungworms, Nodular worms, Red stomach worm, Stomach worm (also Pig louse and Scabies (Sarcoptic mange) mite)	100ug/kg bodyweight	7
levamisole as HCl
(14g/L)	AGROTECH AVISOL LIQUID PIG AND POULTRY WORMER	AGR	Kidney worm, Large roundworm, Lungworms, Nodule worm, Red stomach worm	5mL/10kg bodyweight (see label)	3
(14g/L)	COOPERS NILVERM PIG AND POULTRY WORMER	COO	Kidney worm, Large roundworm, Lungworms, Nodule worm, Red stomach worm	1mL/2kg bodyweight	3
(14g/L)	SYKES BIG L WORMER FOR POULTRY & PIGS	SYK	Kidney worm, Large roundworm, Lungworms, Nodule worm, Red stomach worm	5mL/10kg bodyweight (max: 70 ml)	3
morantel citrate
(30g/kg)	WORMTEC 30 PIG WORMER	PHIB	Large roundworm, Nodule worm	1kg/tonne feed	0
piperazine anhydrous
(172.5g/L)	INCA PIPERAZINE SOLUTION	INC	Large roundworm, Nodular worms	4mL/5kg bodyweight	0
piperazine citrate
(450g/L)	PHARMA-CHEMICAL PIPERAZINE SOLUTION FOR THE REMOVAL OF ROUNDWORMS FROM PIGS, POULTRY, PIGEONS & CAGE BIRDS	PHAC	Large roundworm, Nodular worms	15 mL/13.5 kg bodyweight	0
piperazine di-HCl
(530g/kg)	PIPERAZINE WORM POWDER	AGRIB	Large roundworm, Nodular worms	2.5 kg/10kg bodyweight	0

Company codes:

APX - Apex Animal Health

VIR - Virbac (Australia) Pty Limited

PFI - Pfizer Animal Health

PHA - Bomac Laboratories Limited (NZ) C/- Pharm Tech Pty Ltd

MER - Merial Australia Pty Ltd

NOR - Norbrook Laboratories Australia Pty Ltd

AGR - Agrotech Australia Pty Ltd

COO - Schering-Plough Pty Ltd

SYK - Sykes Vet International Pty Ltd

PHIB - Phibro Animal Health Pty Ltd

INC - Inca (Flight) Company Pty Ltd

PHAC - Pharma-Chem

AGRIB - Agribusiness Products Pty Ltd.

Acknowledgement

Greg Marr
Swine Management Services
56 King Street
KINGAROY  QLD  4160
Ph +61 7 4162 3840
Fax  +61 7 4162 5003
E-mail gregvmarr@bigpond.com

Further information

Infopest CD-ROM of registered pesticides - subscribe to receive updates.

DPI&F Business Information Centre from 8 am to 6 pm weekdays: Phone 13 25 23 (Queensland residents), non Queensland residents phone +61 7 3404 6999; e-mail callweb@dpi.qld.gov.au

DPI&F's web site www.dpi.qld.gov.au

As well as being published on DPI&F's pig industry web site atwww.dpi.qld.gov.au/pigs/, this DPI&F Note will be published on the DPI&FPrimeNotes CDROM  and will be published on DPI&F's national Pig Technotes CD.

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Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.

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Revised November 2004