The passive case detection involves reporting from institutions, like PHCs,
dispensaries,  district  hospitals  etc.    However,  such  cases  represent  those
patients who seek treatment from the government institutions and have access to
them.  There are many patients who prefer to seek treatment from the private or
non-governmental sector or who may not seek any treatment at all for want of
resources.    To  liquidate  all  foci  of  kala-azar,  cases  not  reporting  to  the
government institutions must be detected.  For achieving this objective, door to
door searches, and enquiries from the community are necessary to find out the
total case load in the community.  Thus active case detection in the endemic
areas is needed for demarcating all areas for organizing intervention measures. 
In the case of kala-azar elimination programme active searches are all the more
necessary, since post-kala-azar dermal leishmaniasis, which manifests in the
community as painless disease condition  is often overlooked by  the patient
himself.    PKDL  is  an  extremely  potent  reservoir  for  further  transmission  of
disease, and all such cases must be detected and completely treated.