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New honeybee parasite found in Scotland

Researchers unsure of threat posed to key crop pollinators by widespread fungus.

February 2013

A parasitic organism affecting bees has been spotted in Scotland for the first time, potentially posing a new threat to the UK’s battered bee population.

The new study, published in Parasitology Research, found the Nosema ceranae parasite was already widespread in bee colonies throughout mainland Scotland. N. ceranae is a single-celled microsporidian, now classed as a fungus but previously considered a protozoan, and is related to the N. apis fungus found in honeybee populations worldwide and implicated in colony collapses, although not usually as a sole factor.

Image: Chris Connolly, University of Dundee

Image: Chris Connolly, University of Dundee

The discovery adds to a growing picture of bee vulnerability, but scientists are keen to stress that we don’t yet know how serious the threat posed by the parasite is.

“There are two possibilities,” says Dr Christopher Connolly of the University of Dundee, one of the study’s authors. “Either the parasite came in a long time ago and has gone unnoticed because it’s fairly innocuous. Or it has come in more recently, spread very rapidly and could be a more serious problem. At the moment it’s an unknown threat.”

Bees play a vital role in the global economy, pollinating the crops on which our agriculture depends. “Bees are an important pollinator for us,” says Connolly. “They provide billions of pounds of pollination services to the world economy, and they’re in trouble.”

Unseen infection

Bee populations around the world are collapsing under the weight of habitat change and disease. The EU recently proposed a ban on neonicotinoid pesticides after research suggested they may also be affecting bee numbers. Two if the UK’s 25 bumblebee species have been declared extinct, and the number of managed honeybee colonies has fallen by more than half in 20 years.

Our increasingly joined-up world also allows diseases and parasites to spread more easily between borders and continents. And Connolly thinks a dwindling variety of bee species, in an increasingly uniform world, leaves the honeybee more vulnerable to future challenges. “The problem is globalisation,” he says. “We have more or less the same species all over the world – there’s very little variety – so if you get a problem, it is a global problem.”

The UK team of researchers, supported by Natural Environment Research Council (NERC) grants, worked with the Scottish Beekeepers Association to investigate 71 honeybee colonies throughout Scotland; they found the N. ceranae parasite in 55.

They found it’s more well-known cousin N. apis in 52 of the colonies, while 50 colonies showed signs of both.

The N. apis variety is known to cause diarrhoea and sickness in honeybees, while the N. ceranae strain has appeared to be symptomless. But recent research has suggested that, over longer periods, the N. ceranae parasite may disturb queen-bee laying patterns and honey production, eventually leading to population decline and colony collapse.

Connolly believes that more research is needed to understand its full effects, but he is nevertheless concerned about a recent EU ban on an antibiotic for treating Nosema infections. The EU removed it from the market amid concerns about parasites building resistance to antibiotics.

Connolly is anxious that the consequences for bee health are carefully monitored. “The EU have removed this antibiotic from the market and now there is no medication for Nosema infections. It could have a serious impact on beekeepers,” he says. “The consequences for bee health need to be monitored. Science and policy need to be more in touch.”

This story appeared originally in Planet Earth Online.

References

  1. The microsporidian parasites Nosema ceranae and Nosema apis are widespread in honeybee (Apis mellifera) colonies across Scotland (external link)