Infection with Taenia solium (Porcine cysticercosis)

Article 15.4.1.

General provisions

Taenia solium(T. solium) is a zoonotic parasite of pigs and occasionally of other animals. T. solium is a cestode (tapeworm) that is endemic in large areas of Latin America, Asia and sub-Saharan Africa. The adult cestode occurs in the small intestine of humans (definitive host) causing taeniosis. The larval stage (cysticercus) occurs in striated muscles, subcutaneous tissues and central nervous system of pigs (intermediate hosts), causing cysticercosis. Other suids and dogs can be infected but are not epidemiologically significant. Humans may also become infected with the larval stage through the ingestion of eggs shed in faeces of infected humans. The most severe form of human infection by the larval stage is neurocysticercosis which causes neurological disorders including seizures (epilepsy) and sometimes death. Cysticercosis, although normally clinically inapparent in pigs, is associated with significant economic losses due to carcass condemnation and decreased value of pigs, and causes a major disease burden in humans.

In humans, taeniosis occurs following ingestion of pig meat containing viable cysticerci and can be prevented by avoiding consumption of raw or undercooked contaminated pig meat. In humans, cysticercosis occurs following ingestion of T. solium eggs and can be prevented by avoiding exposure to T. solium eggs through detection and treatment of human tapeworm carriers, community health education, appropriate sanitation, personal hygiene, and good food hygiene. Collaboration between the Veterinary Authority and the public health authority is essential in preventing and controlling T. solium transmission.

In pigs, cysticercosis occurs by ingestion of T. solium eggs from faeces, or environments contaminated with faeces of humans harbouring adult T. solium.

For the purposes of the Terrestrial Code, infection with T. solium is defined as an infection of pigs.

The aim of this chapter is to reduce the risk of infection with T. solium of humans and pigs and to minimise the international spread of T. solium. The chapter provides recommendations for prevention, control and surveillance of infection with T. solium in pigs.

This chapter should be read in conjunction with the Codex Alimentarius Code of Hygienic Practice for Meat (CAC/RCP 58-2005).

When authorising the import or transit of the commodities covered in this chapter, with the exception of those listed in Article 15.4.2., Veterinary Authorities should apply the recommendations in this chapter.

Standards for diagnostic tests are described in the Terrestrial Manual.

Article 15.4.2.

Safe commodities

When authorising import or transit of the following commodities of pigs, Veterinary Authorities should not require any T. solium-related conditions regardless of the status of the animal population of the exporting country:

1. processed fat;

2. casings;

3. semi-processed skins which have been submitted to the usual chemical and mechanical processes in use in the tanning industry;

4. bristles, hooves and bones;

5. semen, oocytes and embryos.

Article 15.4.3.

Measures to prevent and control infection with T. solium

The Veterinary Authority and other Competent Authorities should carry out community awareness and education programmes on the risk factors associated with transmission of T. solium emphasising the role of pigs and humans.

The Veterinary Authority or other Competent Authorities should promote the following measures:

1. Prevention of infection in pigs

   Transmission of T. solium eggs from humans to pigs can be avoided by:

   1. preventing the exposure of pigs to environments contaminated with human faeces;

   2. preventing the deliberate use of human faeces as pig feed or the use of pigs as a means of human faeces disposal;

   3. preventing the use of untreated sewage effluent to irrigate or fertilise land to be used by pigs for forage or for food crops;

   4. ensuring that any treated sewage effluent used to irrigate or fertilise land to be used by pigs for forage or for food crops has been treated in a manner shown to inactivate T. solium eggs;

   5. providing adequate toilet and sanitation facilities for people in areas and establishments where pigs are kept to prevent the exposure of pigs and their environment to human faeces.

2. Control of infection in pigs

   1. The Veterinary Authority should ensure that all slaughtered pigs are subjected to post-mortem meat inspection in accordance with Chapter 6.3., and with reference to Chapter 2.9.5. of the Terrestrial Manual.

   2. When cysticerci are detected during post-mortem meat inspection:

      1. if cysticerci are detected in a carcass of a pig in multiple locations (systemic infection), that carcass and its viscera, as well as all pigs from the same establishment of origin should be disposed of in accordance with Article 4.12.6.;

      2. if only localised cysticerci are detected in a carcass of a pig, the meat from that carcass and from all pigs from the same establishment of origin should be treated in accordance with Article 15.4.6. or may be disposed of in accordance with Article 4.12.6.;

      3. an investigation should be carried out by the Veterinary Authority and the public health authority to identify the possible source of the infection in order to target an intervention;

      4. post-mortem examination of pigs at slaughter from known infected establishments should be intensified until evidence has been obtained indicating that the infection has been eliminated from the establishment.

   An optimal control programme should include detection and treatment of human tapeworm carriers and control of sewage used for agricultural production.

Article 15.4.4.

Surveillance for infection with T. solium in pigs

Communication procedures on the occurrence of T. solium should be established between the Veterinary Authority and public health authorities.

The Veterinary Authority should use information from public health authorities and other sources on human cases of taeniosis or cysticercosis in the initial design and any subsequent modification of surveillance programmes.

Surveillance can be conducted by:

1. meat inspection at slaughterhouses/abattoirs;

2. tongue inspection of live pigs at markets provided that the methods used do not cause injury and avoid unnecessary suffering;

3. other diagnostic tests on live pigs.

The data collected should be used for investigations and for the design or amendment of control programmes as described in Article 15.4.3.

Animal identification and animal traceability systems should be implemented in accordance with the provisions of Chapters 4.1. and 4.2.

Article 15.4.5.

Recommendations for the importation of meat and meat products of pigs

Veterinary Authorities of importing countries should require the presentation of an international veterinary certificate attesting that the entire consignment of meat or meat products:

1. has been produced in accordance with the Codex Code of Hygienic Practice for Meat (CAC/RCP 58-2005);

AND

2. comes from pigs which have been slaughtered in an approved slaughterhouse/abattoir;

AND

3. either

1. comes from pigs born and raised in a country, zone or compartment demonstrated to be free from T. solium in accordance with Article 1.4.6.;

   or

2. comes from pigs which have been subjected to post-mortem inspections for T. solium cysticerci with favourable results;

   or

3. has been processed to ensure the inactivation of the T. solium cysticerci in accordance with one of the procedures referred to in Article 15.4.6.

Article 15.4.6.

Procedures for the inactivation of T. solium cysticerci in meat of pigs

For the inactivation of T. solium cysticerci in meat of pigs, one of the following procedures should be used:

1. heat treatment to a core temperature of at least 60°C; or

2. freezing to minus 10°C or less for at least ten days or any time and temperature equivalent.

nb: first adopted in 2015; most recent update adopted in 2016.