Descripción: “...For the effect 92 animals  were observed during 90 days in the Laboratory of Bioassays of the IALL in Villavicencio, Meta, Colombia, coming from 5 different sources, in which cases of evident illness  were presented:  Of the obser ved animals 43 developed clinical signs; 20 mature specimens were taken for anatomopathologic studies and 19  for microbiologic isolations. In the production systems were: high sowing density, bad water quality and indiscriminate  use of antibiotic drugs, factors that  can predispose to the presence of the disease. ...”