Efficacy of Tylosin Tartrate on Mycoplasma Infections and Eggshell Apex Abnormalities in Layer Hens Under Field Conditions

The aim of this report was to describe a clinical case of concurrent infection with Mycoplasma Gallisepticum (MG) and Mycoplasma Synoviae (MS) in layers, complicated with Escherichia coli and Pasteurella multocida, as well as to evaluate the efficacy of tylosin tartrate treatment (Pharmasin^® 100% WSG, Huvepharma) on Mycoplasma under field conditions. A flock of 18,500 ISA Brown pullets, 21 weeks of age and MS positive, showed an increase in weekly mortality, with no influence on egg production. At 24 weeks of age, post mortem was carried out and blood samples were collected, as well as samples for microbiological cultures from the lesions. In necropsy, several findings of pericarditis, airsacculitis of posterior thoracic sacs, prolapse and egg yolk peritonitis were found. Sporadic neurological signs were also apparent and post mortem examination revealed yellow caseous exudate accumulations in cranial bones. Although egg production was not influenced, Eggshell Apex Abnormalities (EAA) were increased with a significant number of both broken and misshapen eggs together with discoloration. Elisa serological examinations for Infectious Bronchitis Virus (IBV) and Newcastle Disease Virus (NDV) were within vaccination program limits, but MS, MG and Avian Rhinotracheitis (ART) results showed a significant seroconversion. Microbiology also revealed the presence of Escherichia coli and Pasteurella multocida. On week 25, a drug treatment with tylosin tartrate was applied at a dose of 105 mg kg^-1 body weight in drinking water for five consecutive days. Three days after treatment, misshapen, broken and discolored eggs were decreased. The mortality was also significantly decreased within a week since the beginning of tylosin administration and at 30 weeks of age was within acceptable levels. Post mortem evaluation confirmed the absence of previously gross lesions in primary organs. In summary, tylosin treatment in complicated Mycoplasma spp. infections under field conditions improved egg shell quality and decreased mortality, thus the economic losses linked to decreased egg production and labor costs were reduced.