KOLKATA, India (Reuters) - Bird flu spread to two newdistricts in an eastern Indian state, officials confirmed onSaturday, as veterinary staff struggled to cull thousands ofbirds in the face of resistance from farmers.

The H5N1 virus was found in dead birds in Burdwan andNadia, taking to five the number of infected districts in WestBengal state.

The virus was also spreading to new areas within alreadyinfected districts.

India, which is witnessing its fourth bird flu outbreak inpoultry since 2006, has not reported any human infection.

Officials said they were immediately extending cullingoperations to the newly affected areas. West Bengal beganculling more than 400,000 chickens and ducks in three districtsthis week.

So far, only about 50,000 birds had been culled.

"This news is indeed distressing and we are looking tointensify culling in both districts from tomorrow," AnisurRahaman, West Bengal´s animal resources minister, said.

But containment efforts continued to be hampered becausefarmers insisted that their chickens and ducks were healthy andrefused to hand them over for culling.

Scant respect for hygiene among poor and illiteratevillagers was also a stumbling block, said veterinaryvolunteers who collected dead birds dumped in village wells andponds by villagers ignorant about the risks from the H5N1virus.

Rahaman asked health workers to intensify an awarenessdrive.

Health workers were watching for people with flu symptomsin the affected areas.

The virus has killed more than 45,000 chickens and birds inWest Bengal in the past two weeks.

Bird flu has begun taking a toll on India´s poultrybusiness with Oman banning the import of all Indian poultryproducts. Domestic sales have also been affected.

(Writing by Krittivas Mukherjee)