Dr Davis lives in Waimate and regularly visits his Bremner Bay holiday home, where he has conducted unfunded duck itch research since the 1980s.
Few people research duck itch but a neuropathic avian schistosome hosted by the native New Zealand scaup and lymnaeid snails in Lake Wanaka has recently been identified.
Dr Davis said yesterday this "new" parasite, Trichobilharzia regenti, is similar to the parasite Trichobilharzia longicaudia, which has been researched for many years.
"T.regenti's mode of infection is through the nerves, rather than through the blood vessels.
Both parasites are attracted to human skin," he said.
He is asking duck hunters in the Wanaka area to supply him with the frozen heads of at least six mallards, grey ducks, shovelers, paradise shelducks and Canada geese when he is in town from May 5-12.
Dr Davis said the newly identified parasite was a "pretty scary one" because in birds it affected the brain. The parasite also causes paralysis in mice.
Because its impact on humans is unknown, Dr Davis believes research should be funded in this country.
He does not think he would get any funding but is trying to encourage Otago University's zoology department scientists to become involved.
Zoology prof Robert Poulin, of Otago University, said yesterday Dr Davis's passion for identifying duck itch parasites had produced "exciting" information but he had not been able to recruit a full-time PhD student to work alongside him.
It was difficult to recruit to the study of duck parasites because students had personal preferences for other bird species, such as kiwis, he said.
Prof Poulin cannot apply for more research funds from the Marsden Fund until 2015.
Czech studies into T.regenti had shown a measurable neurological impact on birds and it was conceivable it could affect humans, Prof Poulin said.
From a biological perspective this was "very exciting" but it was probably "very far-fetched" and a "long shot" that the parasite could affect humans, although it was important to find out.
The T.regenti parasite is a flatworm which typically reaches 1mm-2mm long when adult.
Suggested forms of controlling duck itch include applying sunscreen containing Deet before swimming. Showering or towelling off immediately after swimming also helps.
Dr Davis is a former US Navy pilot and flight instructor who has lived in New Zealand since 1974. He obtained his PhD in zoology from Otago University in the 1990s.
He became interested in duck itch parasites after noticing how miserable children were getting from itching skin welts after swimming in the lake.
