By Tom Polansek and Leah Douglas
CHICAGO (Reuters) – Colorado began requiring dairies to test milk supplies for bird flu every week, the state’s veterinarian told Reuters on Tuesday, as a federal team arrived to help investigate an escalating outbreak in cows that has spread to chickens and humans.
The state’s new mandate aims to identify additional farms that could be infected and spread the disease to other dairy or poultry operations, after the largest cluster of human cases to date in the United States occurred this month at a farm in Colorado took place.
Bird flu infections linked to dairy cows have wiped out 3.1 million egg-laying chickens in Colorado in recent weeks, and poultry workers also tested positive.
Colorado has confirmed infections at 47 dairy farms since the U.S. outbreak in cows began in late March, with about 60% of cases detected in the past month, according to U.S. data. Nationally, 13 states have reported infections in about 168 herds since the spring.
In Colorado, the loss of millions of chickens led to a requirement that dairies with lactating cows test bulk milk supplies weekly, state veterinarian Maggie Baldwin said in an interview. According to U.S. data, about 70% of the state’s laying hens were eliminated.
“We really said that what we’re doing now is not effective and we need to change the strategy,” Baldwin said.
The U.S. Department of Agriculture has required testing for lactating cows transported across state lines since late April. The agency later launched a voluntary program to test bulk milk supplies.
A USDA epidemiological “strike team” arrived in Colorado this week to assess how the virus might be spreading among dairies there, Baldwin said. Workers or vehicles can transmit the virus from farms.
If mandatory testing reveals additional infections, Colorado could take further steps to contain the virus, Baldwin said.
Six farmworkers in Colorado tested positive for bird flu in July after culling chickens at a contaminated egg farm, the U.S. Centers for Disease Control and Prevention said.
According to the Colorado Department of Public Health and the Environment, more than 150 workers were exposed to the infected poultry, and 69 developed symptoms and were tested.
The Colorado Public Health Department reported a presumptive positive case in humans at another Colorado poultry farm on Friday. About 350 people were involved in culling chickens at that farm, where 23 workers developed symptoms and were tested, the department told Reuters. The CDC has not confirmed the presumptive positive case.
Testing is still being conducted, the Colorado Health Department said Tuesday.
