Honey Bee Viruses, the Deadly Varroa Mite Associates

xtension By Philip A. Moore, Michael E. Wilson, John Skinner     August 21, 2014


Varroa mites (Varroa spp.) are a ubiquitous parasite of honey bee (Apis spp.) colonies. They are common nearly everywhere honey bees are found, and every beekeeper should assume they have a Varroa infestation, if they are in a geographic area that has Varroa (Varroa mites are not established in Australia as of spring 2014). Varroa mites were first introduced to the western honey bee (Apis mellifera) about 70 years ago after bringing A. mellifera to the native range of the eastern honey bee (Apis cerana). Varroa mites (Varroa jacobsoni) in eastern honey bee colonies cause little damage. But after switching hosts and being dispersed across the world through natural and commercial transportation of honey bee colonies, Varroa has became a major western honey bee pest since the 1980’s. Varroa mites (Varroa destructor) are now the most serious pest of western honey bee colonies and one of the primary causes of honey bee decline (Dietemann et al. 2012). A western honey bee colony with Varroa, that is not treated to kill the pest, will likely die within one to three years (Korpela et al. 1993; Fries et al. 2006).

Varroa Life History

Varroa mites attack honey bee colonies as an external parasite of adult and developing bees, by...

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Honeybee Homing Hampered by Parasite

Phys.org    September 3, 2014

In an experiment at Rothamsted Research institute in Hertfordshire, 35 per cent of bees infected with Nosema ceranae never made it home. Among healthy foragers, the figure was less than ten per cent.

The findings are published in the journal PLOS ONE.

'This is obviously bad news for bees infected with the parasite,' says Dr Stephan Wolf, of Rothamsted Research, who led the study. 'But in some ways it's surprising that so many infected bees did so well.'

'We're talking about heavily infested animals, but we couldn't find any difference in their flight patterns - they didn't seem to get lost or confused. It seems some of them were just too exhausted to make it back to the nest.'

'This raises important questions about why some infected bees are able to function in exactly the same way as healthy bees, while others are unable to cope.'

Managed honeybees pollinate important commercial crops throughout the world, but in recent years they have been in decline.

In a study published in January this year, scientists said many European countries are now facing honeybee shortfalls. The problem is particularly acute in Britain, where there are only enough honeybees to pollinate a quarter of crops.

Alongside the unintended consequences of pesticides targeted at other species, diseases and parasites have shouldered most of the blame.

Nosema parasite spores invade cells in the gut, drawing energy for themselves while damaging the bees' ability to absorb food.

There are two species of the parasite - Nosema apis, native to Europe, and Nosema ceranae, an Asian species which in recent years has spread rapidly throughout the world, and is now widespread throughout Europe and the UK.

Nosema ceranae can be terminal for honeybee colonies, but its symptoms are typically subtle in individual bees, giving away very few signs of infection before death.

Previous research suggested that it affects bees' ability to find their way back to the colony. To investigate what happened to them, the team attached tiny radar transponders to the backs of a mixture of clean and infected bees.

Each transponder, just 16mm long and weighing less than the average pollen load, sent a distinct signal back to the radar, allowing scientists to track the position of each bee in real time.

The bees were released onto a field at Rothamsted some distance from the colony, challenging them both to find their bearings and to make it all the way back to the hive.

Although there was very little difference between the flight characteristics of clean and infected bees, some infected  seemed to become exhausted, taking longer stops before settling on the ground and disappearing from the radar.

The only available treatment for Nosema infections, a fungicide called fumagillin, is banned in the European Union over environmental safety concerns. And there is a debate among researchers about its effectiveness against the parasites.

Scientists continue to work on developing safe and efficient alternatives.

More information: Stephan Wolf, Dino P. McMahon, Ka S. Lim, Christopher D. Pull, Suzanne J. Clark, Robert J. Paxton, Juliet L. Osborne, 'So Near and Yet So Far: Harmonic Radar Reveals Reduced Homing Ability of Nosema Infected Honeybees', 2014, PLOS ONEDOI: 10.1371/journal.pone.0103989

Read more at: http://phys.org/news/2014-09-honeybee-homing-hampered-parasite.html#jCp

This story is republished courtesy of Planet Earth online, a free, companion website to the award-winning magazine Planet Earth published and funded by the Natural Environment Research Council (NERC).

The Weaker Sex: Male Honey Bees More Succeptible Than Females to Widespread Intestinal Parasite

Science Daily    1/18/14

Gender differences in nature are common, including in humans. A research team from Bern, Switzerland has found that male European honey bees, or drones, are much more susceptible than female European honey bees, known as workers, to a fungal intestinal parasite called Nosema ceranae. Originally from Asia, Nosema ceranae has rapidly spread throughout the world in recent years, and may contribute to the high number of colony deaths now observed in many regions of the northern hemisphere. These findings demonstrate the delicate nature of male honey bees, which are important to honey bee colony reproduction, to a well-distributed parasite.

Honey bees are complex social organisms that demonstrate haploid-diploidy. The two female castes, workers and queens, are diploid like humans. They contain two copies of each chromosome. Male honey bees, known as drones, on the other hand are haploid and contain only one chromosome set. The haploid susceptibility hypothesis predicts that haploid males are more prone to disease compared to their diploid female counterparts because dominant genes on one chromosome copy have the op- portunity to mask mutated genes on the other copy in diploid organisms.

A research team from the Vetsuisse Faculty of the University of Bern recently demonstrated in an article in the open-access journal PLOS ONE that male honey bees are significantly more susceptible (they die sooner and have poor body condition) to an exotic fungal intestinal parasite called Nosema ceranae compared to female worker honey bees. The parasite, originally from Asia, has recently spread to possess a near global-distribution during a period of high honey bee colony losses in many global regions. Because of its recent detection in honey bees outside of Asia, researchers are scrambling to understand the parasite.

Male honey bees: lazy, but important

The observation that male drone honey bees die much sooner and have a poorer body condition compared to female worker honey bees when infected with the parasite Nosema ceranae is particularly worrisome, say's doctoral student Gina Tanner: 'Although drones do not perform important colony maintenance functions like cleaning and feeding like the workers, they are responsible for mating with queens so that the next generation of honey bees can be produced within a colony. Without strong, fit drones, the chance of successful matings with queens could be severely compromised.' Recent studies, mainly coming out of the United States, suggest that queen failure is a major cause of colony death. Early death of queens could be the result of queens not obtaining sufficient quantity and quality of sperm from drones during mating.

Honey and pollination

Honey bees, as all insect pollinators, provide crucial ecosystem and economic service which is relevant for our food security. Annually in Europe, more than 24 million honey bee colonies contribute to the production of 130,000 tons of honey and to the pollination of a range of agricultural crops -- from carrots to almonds to oilseed rape -- that is valued at €4 billion.


Story Source: The above story is based on materials provided by University of Bern.