Sentence:  More insidious than malaria in its general manifestations, ankylostomiasis did not, at first, attract public attention, and it is feared that even now the leading classes do not quite realise its social and economical importance — yet, reviewing the disease in Health Problems of the Empire, the late Sir Andrew Balfour writes : — " Ankylostomiasis is perhaps the <WSD>Imperial disease</WSD> par excellence,  for even Malaria does not, day in and day out, produce such heavy economic loss ". 
Meaning of the word marked with <WSD> tags:  A disease that arises from colonial exploration and causes significant harm to an empire, especially the British Empire.