Schistosomiasis can be recognised in the majority of instances, although in many the demonstration of eggs is not easy. The diagnosis rests ultimately on the finding of ova or of certain conclusive or highly suggestive signs of the disease.
Diagnostic criteria, such as the intradermal reaction, the blood eosinophilia and the formol gel test, occupy a useful place in its recognition. Nevertheless, it is my experience that they are of limited value and their results in any particular case should only be accepted after careful consideration of the clinical data available.
The blood eosinophilia is a pointer to the presence of the disease but its absence should not exclude it. In my experience, about 50 per cent of bilharzial cases do not show an eosinophilia. Further, even when it is present it may be due to other causes.
The intradermal skin test, if positive, is a factor pointing to the presence of the disease.
Physician, Salisbury Native Hospital, Government Medical Service, Salisbury Southern Rhodesia.