Broiler pulmonary hypertension syndrome. I. Increased right ventricular mass in broilers experimentally infected with Aegyptianella pullorum.

Infection with the obligatory intra-erythrocytic anaplasma-like rickettsia Aegyptianella pullorum in 4-week-old broilers at a moderate altitude of 1,200 m produced a significant increase in the mean relative right ventricular (RV) mass (RV: TV) from 0.23 in the controls to 0.31 in the infected group. This was accompanied by an increase in the number of birds suffering from severe RV hypertrophy from 14.3% in the controls to 50% in the infected group. Pulmonary hypertension and subsequent RV hypertrophy could have been caused by the severe anaemia experienced in the course of the infection or by metabolic or biochemical action of A. pullorum. As the agent does not occur on commercial broiler farms, it cannot play a practical role in the broiler ascites syndrome.