The Effect of Bromhexine and Thyme Oil on Enhancement of the Efficacy of Tilmicosin against Pasteurellosis in Broiler Chickens

Pasteurella multocida is one of the commensal flora of the upper respiratory tract. Under stress conditions, it may be involved as a secondary agent in various respiratory syndromes and caused high mortality as well as significant economic losses in chickens. This study evaluated the effect of bromhexine or thyme oil on enhancement of efficacy of tilmicosin in treatment of avian pasteurellosis. A total of 63 adult chickens were infected by Pasteurella multocida and classified into seven groups and treated as follow; non-infected non-treated group (control negative), infected non-treated group (control positive), group infected and treated by tilmicosin alone, group infected and treated by bromhexine alone, group infected and treated by thyme oil alone, group infected and treated by tilmicosin+bromhexine, and group infected and treated by tilmicosin+thyme oil. Clinical signs, mortality rate, bacterial re-isolation, hematobiochemical and histopathological parameters were determined. The results showed a significant decrease in mortality, bacterial re-isolation as well as clinical signs in combined treated groups compared to tilmicosin group as well as improvement in hematobiochemical and histopathological parameters of combined treated groups. Furthermore, the combination of tilmicosin and bromhexine or thyme oil was more potent in the treatment of pasteurellosis in chickens than each treatment alone. Finally, the clinically observed damage in chickens infected with P. multocida can be ameliorated by a combination of tilmicosin with bromhexine or thyme oil. This protective effect could improve the use of antibiotics in poultry farms as well as reduce human exposure to antibiotic residues and bacterial resistance to antibiotics.