Frequent Blood Poisoning

My 10 yr old Nephew has had blood poisoning 4 times now over the last 4 years. He gets it every time he is bitten by a leech. Each time it lands him in the hospital requiring interveiness ? antibiotics over multiple days. I don't think the poisoning comes from the leech just bacteria entering the open wound after it is removed. Each time we removed the leech quickly and the last couple of time have washed the area with antiseptic and covered it but it didn't help, by the evening or next morning his foot was swollen to twice its size. No one seems to have ever questioned why this keeps happening to him.  Isn't this odd? I think there must be something wrong with his immune system. Any thoughts - I think he should have his blood tested. I am scared one day the poisoning will get out of control or it will happen far from a health centre.  At least we know what to look for now, the swelling and the dark veins that start to travel up his leg.  ...and we do not let him play in lakes without knee-high thick socks on.

[Dr Sharma]

Hi there. Recurrent leech infestation may be due to you residing in a place  where an aquatic body/lake is close. These can cause anemia by secreting enzyme which act as anticoagulants, digest lots of blood and induce bleeding requiring blood transfusion. Once attached to mucosa, blood loss can be profound. Lower airaways, excessive bleeding and obstruction and must be removed immediately by bronchoscopy. It is not certain if aquatic leeches can transmit pathogens from fishes or aquatic organisms to humans.
It could be mere coincidence that he has been infested repetitively. Just protect him from going to the lake etc bare footed. His blood could be investigated for clotting abnormalities, anemia requiring Hb, B12 and folic acid assessment.
Hope this helps.