Spread of infection Incubation period Gastrointestinal symptoms may appear 1–2 days after ingestion of infected meat; systemic symptoms usually appear 8–15 days (range 5–45 days) after ingestion of infected meat. Mode of transmission Humans become infected by eating raw or insufficiently cooked domestic or meat containing viable, encysted Trichinella larvae. Stomach acids degrade cysts encapsulating ingested larvae, resulting in maturation of adult worms in the small intestinal mucosa. Fertilised female worms produce hundreds of larvae over a period of 2–3 weeks and are then expelled in faeces. Newborn larvae migrate via the bloodstream to skeletal muscles, where they may remain viable for several years. The animal reservoir is perpetuated in carnivorous wild animals and in domestic animals (especially pigs) that are fed uncooked meat (for example, swill), eat infected rodent carcasses or cannibalise infected carcasses. Horses and pigs may also become infected through ingestion of larvae passed in rat faeces that contaminate feed. Period of communicability Not transmitted from person to person. Animals may remain infected for several Meat requires cooking, freezing or irradiation to kill the larvae. Freezing kills T. spiralis but not some other Trichinella spp. Notification procedure Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation. Management of case Investigation Ascertain if there is a history of travel and ingestion of inadequately cooked domestic or wild meat and the source of such meat. A definitive diagnosis is important given the potential implications for livestock and export markets. Liaise with an infectious diseases physician or microbiologist to ensure laboratory confirmation by serology has been attempted; antibodies may not become detectable until 3 weeks after infection. When a muscle biopsy is necessary (uncommon), it should be taken from a tender, swollen area of muscle. If infection is present, the uncalcified parasitic cyst will be demonstrated.
Spread of infection Incubation period Gastrointestinal symptoms may appear 1–2 days after ingestion of infected meat; systemic symptoms usually appear 8–15 days (range 5–45 days) after ingestion of infected meat. Mode of transmission Humans become infected by eating raw or insufficiently cooked domestic or meat containing viable, encysted Trichinella larvae. Stomach acids degrade cysts encapsulating ingested larvae, resulting in maturation of adult worms in the small intestinal mucosa. Fertilised female worms produce hundreds of larvae over a period of 2–3 weeks and are then expelled in faeces. Newborn larvae migrate via the bloodstream to skeletal muscles, where they may remain viable for several years. The animal reservoir is perpetuated in carnivorous wild animals and in domestic animals (especially pigs) that are fed uncooked meat (for example, swill), eat infected rodent carcasses or cannibalise infected carcasses. Horses and pigs may also become infected through ingestion of larvae passed in rat faeces that contaminate feed. Period of communicability Not transmitted from person to person. Animals may remain infected for several Meat requires cooking, freezing or irradiation to kill the larvae. Freezing kills T. spiralis but not some other Trichinella spp. Notification procedure Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation. Management of case Investigation Ascertain if there is a history of travel and ingestion of inadequately cooked domestic or wild meat and the source of such meat. A definitive diagnosis is important given the potential implications for livestock and export markets. Liaise with an infectious diseases physician or microbiologist to ensure laboratory confirmation by serology has been attempted; antibodies may not become detectable until 3 weeks after infection. When a muscle biopsy is necessary (uncommon), it should be taken from a tender, swollen area of muscle. If infection is present, the uncalcified parasitic cyst will be demonstrated.
communicable-disease-control-manual-2012.docx