But we should not require newer methods of treatment for this old disease. We should be looking to prevent it, because the knowledge to do so is available. What has been lacking is the will to apply this knowledge. There are many sections of the population who have been too apathetic to use the control measures which could eradicate hydatids as a human health problem.

At the same time, by reducing its incidence in sheep, cattle and pigs, it could save the waste which occurs when organs or whole carcasses have to be rejected at abattoirs.

The presence of many tapeworms within the gut of a dog does not seem to influence its health.

Drugs are available which can kill the worms and repeated treatments of infected dogs, or those suspected of being infected, can reduce the risk of spread.

Most dogs are infected with tapeworm by being fed offal which contain cysts. Country dogs should never be fed on offal and any dead animals should be burned or deeply buried to prevent wild dogs or dingoes from eating an infected carcass.

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No age is immune but it is believed to be more common in children.

There may be a fever, headache, fatigue, enlargement of lymph glands and spleen and a raised red rash. The infection can be so mild as not to be noticed or it may be severe and require treatment in hospital.

Congenital infection is usually quite severe. In the past, most serious infections were in children and it was believed that the parasite affected children and adults differently. This distinction isn’t really true.

Toxoplasma gondii was first discovered in a small North African rodent, the gondi, in 1908 and human infection first recognised in 1923. It is an intracellular parasite and lives within the cells lining the gut, in some blood cells and in other tissues.

Laboratory workers have contracted the disease and so have veterinarians and those who work in abattoirs. The parasite is usually ingested but may be inhaled in dust or enter through small cuts or scratches on the skin.

The illness may involve the brain and spinal fluid and lead to major illness. The eye can be involved and the retina affected — this is the sensitive layer of nerve endings which receive the light stimulus and transmit it to the brain. Blindness can result.

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