Nashik: Bird flu infections continue to spread in Navapur, with samples from two more poultry farms testing positive, prompting authorities to initiate fresh culling operations and expand surveillance beyond previously identified epicentres.Dr Sanjay Khachane, the district deputy commissioner of the animal husbandry department, said the latest detections indicate the infection has spread outside earlier containment zones.“The department had carried out the surveillance of the poultry farms beyond the epicentres that involved two different sets of poultry farms. Samples from them were sent to the laboratory, where those from two farms in different areas tested positive. This is the third set of farms, and both farms are beyond the infected zones surrounding the earlier farms. This means that the infection is still rising,” he said.Authorities have now declared the two farms as new epicentres and launched a re-survey of poultry units in surrounding areas. Birds within the affected perimeters will be culled to contain the spread.“Currently, the number of birds to be culled is around 50,000 in both farms. The survey will establish the exact number of farms and the birds,” Khachane said.In the first outbreak, birds in nine farms across three epicentres were culled. In the second phase, four farms across three epicentres were affected. In the latest instance, two new epicentres have emerged, indicating the infection has spread beyond the 1km radius of previously affected zones.So far, around 3.9 lakh birds have been culled, while 21.6 lakh eggs and 4.99 lakh tonnes of feed have been destroyed by Rapid Reaction Teams engaged in containment efforts. Officials said the latest culling operations at the newly identified farms will begin on Thursday as part of intensified measures to control the outbreak.Despite the decline, Navapur remains a critical food artery. About 12 lakh layer birds currently produce an estimated 10 lakh eggs daily.