Do the clinical findings correlate with the severity of the pneumonia in foals?

Abstract

Bronchopneumonia in horse-breeding plays a major role in the first few months of life in foals. The disease occurs worldwide and as prevention is difficult, early diagnosis and adequate monitoring are important in order to reduce losses. The actual study is expected to determine clinical parameters that indicate a worsening of pneumonia early in order to facilitate the monitoring of sick foals and to analyse the relationship between age at diagnosis, severity of the disease and prognosis. The prospective clinical study was designed four groups of foals with pulmonary lesions of different severity. The foals were monitored for two weeks after diagnosis. A subclinical or clinical pneumonia was diagnosed in 465 foals by means of ultrasonographic examination of the lung. Foals with findings in the ultrasonographic examination were tested at random for bacterial pathogens by microbiological culture. Tracheobronchial aspirates were sampled via endoscope. Clinical examination (rectal temperature, auscultation of trachea and lungs) and ultrasonographic examination of the lung were performed weekly for the two weeks following the day of diagnosis. A total of 135 foals had small pulmonary lesions and received no antibiotic treatment, 221 foals had a mild and were treated with sulfadiazine-trimethoprim, 92 foals had a moderate, they were treated with rifampin and tulathromycin and 66 foals a severe pneumonia, which were treated with rifampin and azithromycin. Of all 53 foals sampled for airway pathogens, in 14 foals Rhodococcus equi was isolated and in 40 foals Streptococcus equi zooepidemicus was identified. All recovered fully within a maximum of 9.5 weeks of treatment; 47 foals with mild to severe pneumonia needed a change of treatment, because the first choice of antibiotics failed to cure the foals. Fever was observed in 23 % of the foals with small pulmonary lesions, which is significantly less (p < 0.0001) than in the 60 % of foals with severe pneumonia. Auscultation findings in the lung and trachea were more frequent with the increasing severity of the pneumonia, but significantly different only between groups 1 and 4 (p < 0.018). The average age at diagnosis in all groups was 102 days, but foals which needed a change of treatment were significantly younger (80 days; p < 0.0001). Regarding the three signs studied, fever is the best indicator of a more severe progression of disease and worsening of the pneumonia that leads to a change of treatment. The age of foals at diagnosis showed no difference regarding the severity of ultrasonographic findings, but foals that needed a change of antibiotics were significantly younger than the others. Therefore, young foals with pneumonia need to be monitored closely, even if the age at diagnosis did not correlate with the severity of the pneumonia.