A cross sectional study to isolate and identify aerobic bacterial species from upper respiratory tract of horses was conducted from October, 2009 to April, 2010. Forty eight apparently healthy horses (APHH) and 56 horses with respiratory tract diseases (HRTD) brought to Society for protection of animals abroad (SPANA) clinics in Central Ethiopia were randomly selected. Swab samples were collected aseptically from nasopharynx of the horses. Isolation and identification of the bacteria was carried out following the recommended standard procedures. A total of 270 bacteria were recovered from the sample taken from both groups. Of the total isolates, 65.9% were Gram positives and the remaining 34.1% were Gram negatives. Bacterial species isolated in order of dominance include: Bacillus species, Streptococcus species, Staphylococcus species, Escherichia coli, Pasteurella species, Micrococcus species, Bordetella species, Pseudomonas species, Actinobacillus species and Rhodococcus equi. Actinobacillus species and Rhodococcus equi were only isolated from APHH. Despite the percentage variation of the isolates, there was no statistically significant (p>0.05) variation among the isolates with respect to altitude and health status of horses except significant variation of Staphylococcus species (p≤0.05) between low and high altitudes. In conclusion, the study showed that wide variety of aerobic bacterial species inhabiting the upper respiratory tract of horses with similar distribution of the bacteria in APHH and HRTD suggesting bacteria which reside in the URT of healthy animals might cause opportunistic infections. It is recommended that clinicians should consider the dominance of Gram positives primarily as a cause of upper respiratory tract diseases in horses.
Key words: Bacterial species, horses, respiratory tract, Central Ethiopia, SPANA.
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