Failure of passive zooprophylaxis: cattle ownership in Pakistan is associated with a higher prevalence of malaria.

To examine the possibility that domestic cattle kept in house courtyards might protect occupants against malaria through zooprophylaxis, parasite prevalence surveys were conducted of schoolchildren in Pakistani and Afghan refugee villages and analysed according to whether each child's family kept cattle. Parasite prevalence (15.2%) was significantly greater among children of families which kept cattle than among those which did not (9.5%). Comparison of prevalence between different villages revealed a positive correlation between parasite rates and the proportion of families owning cattle. The latter finding supports the prediction of the Sota-Mogi theoretical model that domestic animals can enhance rather than reduce malaria transmission when vectors are zoophilic, the infection rate low, and the human:cattle ratio high. All these conditions applied in the study area.