Ducks are being unfairly blamed for spreading salmonella to stock, with some farmers even destroying wildfowl nests.
Fish and Game senior officer Matthew McDougall said there were occasional reports of farmers trampling duck nests because they thought the birds were responsible for salmonella outbreaks in stock.
"Large flocks of paradise shelduck are also
often unduly maligned as the cause of disease in domestic stock."
However, recent research indicates the birds may be more likely to catch the disease from livestock than to infect them.
"The issue of wildfowl infecting domestic stock crops up from time to time," Mr McDougall said.
"Some years back we commissioned a literature search and spoke with MAF's national animal health surveillance officer.
"The general consensus was that wildfowl were more likely to catch salmonella from domestic stock than the other way around.
"Gulls are known to have high levels of salmonella yet the number of salmonella produced by a flock of gulls is very low compared with what has been experimentally shown to cause disease in healthy animals."
Salmonella is a diverse bacterium with 900 serotypes (group of bacteria that share a common antigen).
It occurs naturally at low levels in many animals.
Outbreaks occur when animals are exposed to an infective dose, or an animal exposed to a carrier is stressed.
Mr McDougall said forms of stress included yarding, calves missing a feed, and previous sickness.
In New Zealand, 15 per cent of dairy cattle and 4 per cent of beef cattle were estimated to carry the bacteria.
Salmonella lasts up to three months in pasture and up to eight months in stored slurry.
Spraying effluent from the cowsheds on to pasture is therefore another risk.
Mr McDougall said Fish & Game could provide permits to move birds on if farmers were concerned about waterfowl.
