Question: who are affected more by the parasite, children or adults?

Anouk Gouvras answered on 18 Jun 2012:

Hi tallulah,

this is a difficult question to answer, it really depends on the parasite. But short answer – both.

Perhaps if I give some examples;

starting with schistosomes, the worm parasites I study. Scientists have found that the majority of infections occur at a young age, between the ages of 4 and 16. Children harbour the largest number of schistosome worms. As the worms get older they start to die (they actually live several years) and as the child gets older a bit of immunity to infection starts to develop. So by the time they reach adult-hood there are fewer worms infecting them. However when you look at the disease, the damage is caused by the eggs, as the eggs try to get out they cause damage to the tissues, children often pee and poo blood from this damage. However a large amount of the eggs (it is not known for sure just how many) get stuck in the organs of the child. The immune system reacts to these eggs continuously. As the child gets older this reaction damages more of the healthy human cells around the eggs. The more eggs in the organs the more damage, and with age the damage gets worse. Until the adult starts suffering from renal, liver, bladder damage, lesions in the genital tract making them more vulnerable to sexually transmitted diseases and chronic abdominal pain. At this stage you can not cure the infection. You can stop new infections but the damage has already been done. At least with children if you treat you can prevent the damage. But adults suffer a lot from schistosome damage. In fact it is one of the leading causes of bladder cancer in sub-Saharan Africa, and that’s in adults.

Another example is malaria, a protozoan blood parasite transmitted by the bite of a female mosquito; around 800, 000 children under the age of 5 die of the disease every year. Malaria does still affect adults, they get a temperature and flu like symptoms, but unless the are immuno-supressed, adults tend to recover. However young children do not have fully developed immune systems and hence are very vulnerable to the disease.

And finally on an sociological, human level, if a child is ill you can be sure that this effects the parents!