CONTRIBUTION TO THE STUDY OF EXTERNAL OTI TIS OF DOGS

To determine the presence of microorganism in the external ear canal o f dogs, a study was carried out in Valdivia, Chile, between fall and w inter of 1990. A bacteriological, micological and parasitic examinatio n of the external ear of 100 clinically healthy dogs, as well as of 45 dogs affected by an external otitis was performed. Some predisposing factors of the disease were determined. Results showed that the normal microbiota of the external ear canal was composed of bacteria and/or fungi; mites were not found. In healthy ears the bacterium mostly isol ated was Bacillus sp. (27%) and the fungus mostly isolated was Malasse zia pachidermatis (11.53%). The most frequent aetiological agents of e xternal otitis were Staphylococcus aureus (36.2%) and Malassezia pachi dermatis (27.5%). The most important predisposing factors of the disea se were breed and ear type; the pendulous-ear breeds were the most aff ected (39.8%) and among the pure breeds the Cocker Spaniels (22.2%). S ex was not an important factor, and the greatest number of clinical ca ses ocurred in winter (66.6%). Finally, it is possible to say that ext ernal otitis is due to an association of factors which produce changes in the physiology and microbiology of the ear. It is very important t o specify the aetiological cause of the disease in order to obtain a p recise diagnosis and an efficient treatment.