The visits are in the morning when birds are most active. On each farm, Varriano stands at four different points and counts the number of birds, including those flying over, and the different bird species.
Smith meanwhile walks up and down the rows looking for bird feces on plants. If he finds a fecal sample, he collects it for lab analysis. He also swabs any fruit below the bird feces as well as swabbing up to two plants within 5 feet downwind. They also note landscape features, such as hedgerows or woods, next to each farm.
The lab analysis is actually two-fold. The first, which Shariat described as low-resolution, involves looking at the different Salmonella serotypes found in each sample.
“We know that certain serotypes are associated with different production systems or the environment,” she said.
Campylobacter is more difficult to assay in a laboratory. Several different species may exist in one sample, so the researchers have to identify each Campylobacter species.
“Some species have a greater association with different animals,” Shariat said. They then use molecular analysis of the feces itself to identify the bird species so that her team can correlate pathogen presence or absence with particular species.
This work is then followed by higher-resolution analyses.
“Our work will use new sequencing-based technologies to identify whether complex populations of different Campylobacter species or of different Salmonella serotypes exist in the same fecal sample.”
Identified isolates will then undergo whole genome sequencing. This allows the researchers to investigate whether there are any connections between Salmonella or Campylobacter found in animal production systems or human outbreaks to those found in the bird feces.
Although lab analysis is ongoing, she said they have yet to find any Salmonella or Campylobacter in swabs taken from fruit below bird feces or downwind from feces. “This preliminary data is exciting,” Shariat said. “It shows that on-farm transmission doesn’t occur very frequently.”
The team looks forward to sampling in year 2 of the study to see if these trends hold true.
The results of the farm surveys as well as the laboratory testing will be used to create a computer risk model. Together with results of the grower survey, Shariat said they plan to produce science-based wild bird risk-management materials for producers that will be shared through extension programs.
