| assessing infections at multiple levels of aggregation. | the patterns of sero-prevalence of antibodies to four infectious diseases, representing a broad range of pathogens (bacteria: brucellosis; mycoplasma: contagious bovine pleuropneumonia; viruses: infectious bovine rhinotracheitis; protozoa: trypanosomosis) were investigated at three levels of organization (farm, area and district). three contrasting districts in kenya were compared: an arid and pastoral area (samburu); a tropical highland area (kiambu), and a tropical coastal area (kilifi). cattl ... | 1997 | 9234402 |