Sero - Prevalence of Mycoplasma gallisepticum Infection in Chicken Ross 308 and Colour ISA Raised in Some Provinces in The North of Vietnam

Abstract

A study was conducted in chicken Ross 308 and colour ISA in some provinces in the North of Vietnam (Bac Ninh, Ha Tay and Hai Phong) to dertermine the sero-prevalence of Mycoplasma gallisepticum. Results showed that the average level of M. gallisepticum infection in the studied flocks was 37.83%; there was no difference between the rate of M. gallisepticum in the 2 breeds (Ross 308 -  37.47% and ISA - 38.40% with P>0.05). The M. gallisepticum infection rate tended to increase with the age of chicken. In the group of chicken under and above 35 days old, the rate was 32.42% and 42.33%, respectively (P<0.05). The highest infection rate in the flocks occurred in the period of Octorber - December (45.88%) and the lowest rate was from April to June (30.36%). The range of sero prevalenve of M. gallisepticum was from 34.42% to 41.02% in the studied places. In the flocks with a high rate of sero-positive, the time for the first clinical symptoms occurred earlier in comparision with those with a low rate of infection. In the flocks with a sero-positive rate below 50% the first symptoms were found  from 4.67 to 5.55 weeks in Ross 308 and from 5.57 to 6.76 weeks in the coulor ISA . In the flocks with a sero-positive rate higher than 50%, the first symptoms could be seen from 3.46 to 4.73 weeks of age in Ross 308 and from 3.61 to 6.10 weeks in the coulor ISA