Stephanurus or Kidney worm

Stephanurus

This is the 'kidney worm' of swine which is of economic importance in its endemic areas.

Major Species	Hosts	Location/Site	Distribution
Stephanurus dentatus	Pig.	Kidneys and perirenal tissues	tropical regions of the world ( Does not occur in western Europe)

Identification

• A large stout pinkish worm up to 4.5 cm long, with a promi­nent buccal capsule and transparent cuticle through which the internal organs may be seen.

Epidemiology

• Though the adult worms are neve numerous, they are very fecund, and an infected pig may pass a million eggs per day.
• The L₃ is susceptible to desiccation, so that stephanurosis is mainly associated with damp ground. Since it infects readily by skin penetration, the pigs' habit of lying around the feeding area when kept out­side presents a risk, as does damp, unhygienic accom­modation for housed animals. Such conditions, coupled with prenatal infection and the longevity of the worm, ensure continuity of infection through many generations of pigs.

Life Cycle:

The adult parasites live in Kidneys and perirenal tissues

Eggs passed in the urine and development of L₃ occurred in environment

Final host get infected by the ingestion of L₃ or

L₃ containing Earth worm (Transport host)

                                                                              Or percutaneous infection by L₃                            Blood stream             lungs      

After entering the body, immediately L₃ moult to L4 and travel to the liver through Portal system

Final moult (L₄ to L₅) occurred in liver and the young adults wander in the parenchyma of liver for3 months or more before piercing the capsule

The young migrating in the peritoneal cavity to the perirenal region and they enclosed in a cyst by host reac­tion, and complete their development

The cyst com­municates with the ureter either directly or, if it is more distant, by a fine connecting canal, allowing the worm eggs to be excreted in the urine.

PPP: 6-19 months

Note:

• Though the worm favoured the perirenal fat, some worms occur in the kidney itself, in the calyces and pelvis.
• Prenatal infection has been reported.
• Erratic migration is common in Stephanurus infec­tion, and larvae have been found in most organs and in muscle. In these sites they are trapped by encapsula­tion and never reach the perirenal area.
•  worms have a longevity of about two years

Pathogenesis

• The main pathogenic effect is due to the larvae which, by the late L₄ stage, have heavily sclerotized buccal capsules capable of tearing tissue and they cause much damage to the liver and occasionally other organs in their wanderings.
• In heavy infections there may be severe cirrhosis and ascites and, in rare cases, liver failure and death.
• In most infections, however, the effects are seen only after slaughter as patchy cirrho­sis, and the main importance of the worm is economic, from liver condemnation.
• adult worms, soon after arrival at the perirenal site, are encapsulated in cysts, which may contain greenish pus. In rare cases the ureters may be thickened and stenosed, with consequent hydronephrosis.
• Stephanurus may occasionally cause severe liver damage in calves grazing on contaminated ground.

Clinical Signs

• In most infections the only sign is failure to gain weight
•  in more severe cases, weight loss.
• In more extensive liver damage, there may be ascites, but it is only when there is massive invasion, comparable to acute fasciolosis in sheep, that death occurs.

Diagnosis

• Clinical History with epidemiology
• Clinical signs
• Urine examination

• The size and site are diagnostic.

Treatment

• Levamisole, the modern benzimidazoles and iver-mectin are effective.

Control

• Maintain hygienic environment to prevent percutaneous and prenatal infection
• Provision of impervious surface around the feeding areas for outdoor reared pigs and (to prevent earthworm)
• simple hygiene and ensure clean dry flood
• Isolation of young pigs from those of more than nine months of age which will be excreting eggs.

Regimes incorporating anthelmintic control recom­mend treatment of sows and gilts 1-2 weeks before putting to the boar, and again 1-2 weeks before far­rowing.