EFFECT OF ISOLATION AND SANITATION ON THE RECOVERY OF F-STRAIN MYCOPLASMA-GALLISEPTICUM FROM CHRONICALLY INFECTED HENS HELD IN BIOLOGICAL ISOLATION UNITS

Two trials were conducted to determine if individual housing or improved sanitation would enable hens to clear Mycoplasma gallisepticum (MG) infection. In each of the two trials, 40 commercial leghorn hens were infected with F strain MG (F-MG) and confined in biological isolation units in two groups: 1) hens housed individually in each of eight isolation units and 2) hens housed in groups of four in each of eight other units. Each of these two groups was further subdivided into two groups: 1) non-sanitized, having the isolation unit interior cleaned but not sanitized once each 2 weeks; and 2) sanitized, having the isolator interior thoroughly cleaned and sanitized twice weekly. Choanal cleft swabs were obtained five times over a period of 16 weeks in Trial 1 and six times over 22 weeks in Trial 2. Isolates were identified as F-MG positive by agar plate fluorescent-antibody method. The incidence of isolation of FMG did not differ significantly between individually housed and group-housed hens, except that the percentage of positive isolations was significantly lower in individually housed/sanitized hens than group-housed/sanitized hens in Trial 1. Sanitizing had no consistent beneficial effect. The results do not support the theory that hens can clear F-MG infection if isolated from other infected hens.