Introduction
Beef measles are small parasitic cysts in the muscles of cattle. Their presence can lead to part or whole of a carcase being condemned.
Cattle get beef measles from humans, so the occurrence of beef measles in a district may also indicate a human health problem.
Cause
Beef measles (Cysticercus bovis) are the intermediate state in the life cycle of a human tapeworm (Taenia saginata). An affected person can remain that way for life unless treated. A human must get the tapeworm from cattle, and vice versa.
The tapeworm occurs in the small intestine of humans, and although it is generally 4–8 m long, it can measure up to 15 m. Like all tapeworms, it has a scolex (or head), which attaches to the bowel wall, and a number of body segments. There can be up to 2000 segments.
Each segment of the tapeworm in a person contains up to 80 000 eggs. From time to time the end segments become detached and are passed in the faeces. These segments may be seen as white fleshy capsules like small rice grains.
To complete the cycle, the eggs in the segments must find their way onto pasture where cattle are grazing. Once eaten by cattle, they hatch in the small intestine. The small embryos penetrate the bowel wall, reach the bloodstream and are carried throughout the body. Those that reach a suitable muscle develop into the cysts that are known as ‘beef measles’. Embryos that fail to reach a muscle do not survive.
Cysts may occur in any muscle of cattle, but tend to affect the heart, tongue, diaphragm and muscles of the jaws. Cysts that survive in the muscles generally do not have a long life. Most are overcome by the animal’s defences and remain as degenerated cysts. Some, however, have been known to remain infective for 2 years.
About 10 to 20 per cent of cysts found at abattoirs are alive.
Figure 1: Beef Measles Life Cycle
Figure 1: Beef Measles Life Cycle
Spread of beef measles
The important factors leading to infection of cattle with eggs are:
-lack of personal hygiene whereby human faeces reach grazing land; and
-the passage of viable eggs through public sewerage systems or private septic tanks and onto pasture with the effluent.
It is probable that soil moisture in irrigated paddocks helps the worm eggs survive and raises the infection level.
1. Live cyst passes to humans from poorly cooked meat and develops into tapeworm in the small intestine.
2A. Cycle is broken if humans use proper toilet hygiene.
2B. Cycle continues if human faeces containing tapeworm eggs are deposited on grass.
3. Cattle ingest tapeworm eggs from grass.
4. Eggs hatch into tapeworm embryos in intestine of cow; embryos penetrate wall of guts and spread through bloodstream. Cysts develop in muscles, especially jaws and heart.
5. Cysts survive in poorly cooked meat, and when eaten by humans, commence the cycle once again.
Why worry?
The meat condemned at abattoirs represents waste.
Undetected cysts may be found after cutting up the carcases. If this occurs after arrival of the carcase in another country, exports could be affected.
The tapeworm may affect the health of the person carrying it.
In rare cases the cystic intermediate stage may develop in the body of a person, and this can be serious if it lodges in an important organ such as the brain.
What to do?
Now is the time to act. Ensure that human faeces are not deposited on cattle pasture or crop that is to be used as fodder or hay.
The beef measles cyst is killed by cooking all parts of the meat at a temperature of at least 57°C, that is, until the meat is uniformly cooked through to the centre. Freezing for up to 10 days at –8°C to –10°C is needed to kill the cysts.
Tapeworms in humans can be treated. Anyone who thinks they might have a tapeworm should contact their doctor.
