Guanajuato, Mexico - Mexican authorities have slaughtered 2.1 million chickens exposed to the latest outbreak of bird flu, which has spread to 18 farms in the central state of Guanajuato, government officials said on Monday.

Agriculture Secretary Enrique Martinez said at a press conference that since the outbreak was detected 519,000 egg-producing chickens have been slaughtered, along with 900,000 birds being fattened for their meat and 722,265 reproducing birds.

He said that the losses do not affect the national inventory of chickens, which totals 140 million laying birds and 300 million chickens being fattened for market.

Martinez also said that the outbreak is being controlled and is on the way to being resolved in the affected zone, "a complex task since it deals with a very pathogenic virus that requires great efforts to prevent its spread."

Senasica - Mexico's National Health, Food Safety, and Food Quality Service - said that its experts had inspected 35 chicken operations in Guanajuato and four million birds, of which 1.3 million were deemed not to be infected by the H7N3 bird flu.

Senasica director Enrique Sanchez Cruz said at a press conference that the virus is one against which Mexican chickens have no natural defense and thus their only protection is the vaccine produced in Mexico, which "has functioned extraordinarily well."

Some 22 million birds have been vaccinated since the outbreak was detected a week-and-a-half ago and this week alone 40 million more doses will be distributed.