Birds May Spread, Not Halt, Fever-bearing Ticks30 November 2012
US - In Turkey, thousands of non-native guineafowl have been raised and released to eat ticks that carry the deadly Crimean-Congo haemorrhagic fever virus in people. Yet research suggests guineafowl eat few ticks and carry the parasites on their feathers, possibly spreading the disease they were meant to stop, says a biologist working at the University of Utah.
"They are introducing a species that is not eating many ticks, based on studies of stomach content, and is carrying the ticks, which are the best conduit for spreading Crimean-Congo hemorrhagic fever," says Çagan Sekercioglu, an assistant professor of biology at the University of Utah.
"They should stop these introductions immediately because there is a risk they may be doing the opposite of what they intended," says Dr Sekercioglu, an ornithologist or bird expert and founder of the Turkish environmental group, KuzeyDoga Society. "They want to stop this disease, but they may be helping spread it."
In a paper, set for publication soon in the journal Trends in Parasitology, Dr Sekercioglu reviewed existing scientific literature. He concluded that the idea guineafowl eat ticks and thus control disease is based on unconvincing evidence even though it achieved "cult status" after a 1992 study suggesting the birds could control ticks that carry Lyme disease bacteria in the US Northeast, at least on lawns.
Crimean-Congo haemorrhagic fever was identified as an emerging disease in Turkey in 2002. Between then and last May, the tick-borne virus infected 6,392 people there and killed 322 of them, according to statistics cited by Dr Sekercioglu.
It was first identified in Crimea in 1944 and then in the Congo in 1969, and now it is found in Eastern and Southern Europe, the Mediterranean region, the Middle East, northwest China, central Asia and the Indian subcontinent, says the US Centers for Disease Control and Prevention.
Cases of the disease did drop in 2011, leading some officials to call the guineafowl program a success. But Dr Sekercioglu says, "There is no published study in Turkey showing guineafowl are effective." He cites news reports in which doctors attributed the decline to increased public awareness that prompts patients to get to a hospital faster and obtain better diagnosis and treatment.
Guineafowl released to fight viral disease outbreak in Turkey
Some 300,000 birds, mostly native pheasants and chukars, have been released for a decade in Turkey, potentially to eat the ticks. In 2011, the government started raising thousands of guinea fowl for the same purpose, especially in north-central Turkey, although Dr Sekercioglu says there is no convincing evidence that any of the birds help control the tick-borne virus.
What little evidence exists came from a 1992 study in New England suggesting guineafowl eat ticks in that region and thus reduce the risk of tick-borne bacteria that cause Lyme disease, he says. That prompted people to start selling guineafowl for tick control, but a 2006 study concluded the 1992 study was unconvincing, Dr Sekercioglu says.
Nevertheless, Dr Sekercioglu was told by Turkish officials more than a year ago that they learned about the use of guineafowl to control ticks and started the program to raise and release the birds in Turkey.
Dr Sekercioglu expressed his doubts, even though at the time he was unaware that guineafowl carried ticks on their feathers.
"I told them I had not seen convincing evidence for this, and that introducing an exotic species in such large quantities without a detailed, controlled study would be dangerous and could have unexpected consequences," he says.
Dr Sekercioglu cites a 1993 study that examined 525 guineafowl, yet found only one tick each in the stomachs of four of the birds, and a study in 2006 from South Africa that found that a single guineafowl could carry more than 300 ticks on its feathers, he says.
He wants the Turkish government to stop introducing guineafowl and also to "conduct a very detailed controlled experiment with a large sample size of guinea fowl's effect on ticks, comparing them with pheasants and chukars. If pheasants and chukars are as effective as or more effective than guineafowl, then why introduce a species that does not belong to that ecosystem?"