Study design

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

Sometimes prior information on the species kept by a particular homestead was found to be incorrect. Thus, on reaching a homestead, supposedly keeping pigs and the species that had been pre-selected as the primary one for the survey at this particular homestead, the enumerator may have found that the homestead only kept goats. 

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