Bovine cysticercosis

Infestation of cattle with the larval stage of the human tapeworm Taenia saginata.

T. saginata of humans and bovine cysticercosis occur virtually worldwide, but particularly in Africa, Latin America, Caucasian, South and Central Asia, and eastern Mediterranean countries. The infestation occurs in many countries in Europe and sporadically in the United States of America, Canada, Australia and New Zealand.

Humans are the definitive host of T. saginata while cattle are the intermediate host of bovine cysticercosis.

Humans and cattle are the only hosts in the bovine cysticercosis life cycle.

Cattle infestation

• Cattle become infested by consuming pasture, feed concentrate or water that has been contaminated with infested human faeces.
• Once ingested, the eggs hatch in the small intestine, develop into embryos and penetrate the bowel wall. They are carried through the bloodstream to various muscles, where they develop into Cysticercus bovis cysts.
• The cysts can remain infective for up to 2 years.

Human infestation

• Humans become infested   by ingesting raw or undercooked beef infested with the cysts.
• The cysts develop into T. saginata tapeworms in the small intestine and the heads (scoleces) of the tapeworms attach to the wall of the bowel.
• A tapeworm can grow to extraordinary lengths (typically 4–8 metres but sometimes up to 15 metres) and has up to 2,000 segments, each bearing up to 80,000 eggs.
• Usually T. saginata tapeworms do not affect human health, but they may cause gastrointestinal upset or in rare cases can spread systemically to cause serious disease.

Cattle reinfestation

• The life cycle is completed when infested people pass tapeworm eggs or segments to expose cattle to infestation.

Infested cattle do not exhibit any clinical signs. A build-up of cysts in the muscles of infested cattle may be detected at abattoir inspection.

If unmanaged, bovine cysticercosis could have significant impacts on human health as well as meat export markets. It causes economic loss through condemnation of infested meat and offal, which is unsafe for human consumption.

Eggs may spread directly from human faeces or be transported by hosts such as flies that have ingested eggs. Cattle become infested by consuming pasture, feed concentrate or water that has been contaminated by human faeces or inadequately treated human sewage.

Humans become infested by ingesting raw or undercooked beef that is infested with the cysts.

Prevention

Bovine cysticercosis is not harmful to cattle, but prevention of the disease is important to avoid:

• transmission to humans
• carcass condemnation at slaughter
• loss of export market access.

Avoid contamination of cattle feed (including fresh pasture, hay, silage and supplements) or water with human faeces or sewerage outfall.

Pasture can become contaminated from:

• overflowing domestic sewage systems
• irrigation with inadequately treated recycled water
• human defaecation into a grazing environment
• transfer of eggs from water birds who have visited nearby sewage treatment works.

Imported feed supplements may carry tapeworm segments laden with eggs.

Transfer of cattle

Written notification of disease risk should be provided when exposed cattle are consigned to a new owner or to slaughter. Exposed cattle are those that:

• have been exposed to inadequately treated human sewage or faeces
• originate from a herd in which bovine cysticercosis has previously been detected.

This helps to support meat inspection for safe food.

Treatment

Cysts in beef may be killed to protect humans from infestation of T. saginata tapeworm. Either:

• freeze the beef for 10 days at –8 to –10 degrees Celsius
  or
• cook it to a temperature of at least 57 degrees Celsius and until the meat is uniformly cooked through.

To help manage the risk associated with using recycled water, the Livestock Production Assurance program  introduced a warning system using:

• property identification codes
• animal devices.

This ensures agreed standards of meat inspection are implemented according to the risk.