Study design

Some questionnaires had to be discarded due to incomplete or missing information.

Sometimes prior information on the different species kept by a particular homestead was found to be incorrect see (Case Study 11). Thus, on reaching a homestead, supposedly keeping pigs and pre-selected as the primary species to be completed for the questionnaire, the enumerator may have found that the homestead kept other species, but not pigs.

More than 10 homesteads were interviewed in some dip-tank areas. Use of a modified random walk method for selection of homesteads sometimes led to additional homesteads being interviewed.