Theoretical considerations in the vector control of filariasis.

In order to assist in assessing progress of vector control of filariasis a theoretical model is constructed, using retrospective data on infected persons removed to a vector-free situation. This shows that the decrease of microfilaraemia is not regular, but is gradual for the first 3 years and then more rapid, reaching zero at about 10 years. An estimate is made of the level to which the vector must be reduced before transmission of filariasis ceases, showing that the degree of efficiency required is considerably less than for malaria.