East African honeybees safe from invasive pests … for now

Several parasites and pathogens that devastate honeybees in Europe, Asia and the United States are spreading across East Africa, but do not appear to be impacting native honeybee populations at this time, according to an international team of researchers.The invasive pests include including Nosema microsporidia and Varroa mites.”Our East African honeybees appear to be resilient to these invasive pests, which suggests to us that the chemicals used to control pests in Europe, Asia and the United States currently are not necessary in East Africa,” said Elliud Muli, senior lecturer in the Department of Biological Sciences, South Eastern Kenya University, and researcher at the International Centre of Insect Physiology and Ecology, Kenya.The team first discovered Varroa mites in Kenya in 2009. This new study also provides baseline data for future analyses of possible threats to African honeybee populations.”Kenyan beekeepers believe that bee populations have been experiencing declines in recent years, but our results suggest that the common causes for colony losses in the United States and Europe — parasites, pathogens and pesticides — do not seem to be affecting Kenyan bees, at least not yet,” said Christina Grozinger, professor of entomology and director of the Center for Pollinator Research, Penn State. “Some of our preliminary data suggest that the loss of habitat and drought impacting flowering plants, from which the bees get all their food, may be the more important factor driving these declines.”According to Harland Patch, research scientist in entomology, Penn State, not only are flowering plants important for honeybees, but the insects are important for plants as well.”Honeybees are pollinators of untold numbers of plants in every ecosystem on the African continent,” Patch said. “They pollinate many food crops as well as those important for economic development, and their products, like honey and wax, are vital to the livelihood of many families. People say the greatest animal in Africa is the lion or the elephant, but honeybees are more essential, and their decline would have profound impacts across the continent.”In 2010, the researchers conducted a nationwide survey of 24 locations across Kenya to evaluate the numbers and sizes of honeybee colonies, assess the presence or absence of Varroa and Nosema parasites and viruses, identify and measure pesticide contaminants in hives and determine the genetic composition of the colonies.”This is the first comprehensive survey of bee health in East Africa, where we have examined diseases, genetics and the environment to better understand what factors are most important in bee health in this region,” said Grozinger. The results appeared today in PLOS ONE.The researchers found that Varroa mites were present throughout Kenya, except in the remote north. In addition, Varroa numbers increased with elevation, suggesting that environmental factors may play a role in honeybee host-parasite interactions. Most importantly, the team found that while Varroa infestation dramatically reduces honeybee colony survival in the United States and Europe, in Kenya, its presence alone does not appear to impact colony size.The scientists found Nosema at three sites along the coast and one interior site. At all of the sites, they found only a small number of pesticides at low concentrations. Of the seven common honeybee viruses in the United States and Europe, the team only identified three species, but, like Varroa, these species were absent from northern Kenya. …

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Parasites change bees brains, but not their behavior

July 17, 2013 — Honey bees Apis mellifera) infected with the parasitic mite, Varroa destructor, or the microsporidia, Nosema ceranae, have changes in the chemical profile of their skin and in their brains, finds research in BioMed Central’s open access journal BMC Ecology. Despite this, parasitized bees were not expelled from the hive, which, the authors say, supports the hypothesis that stressed bees leave the hive altruistically to prevent the spread of infection.Share This:This study from INRA (French National Institute for Agricultural Research) investigated the effect of parasitization on honey bees living in hives at Avignon. Individual bees were infected with either the ectoparasite Varroa, which lives on the bees, or endoparasite Nosema, which invades their bodies, and reintroduced to the hive. After a few days the effect of infection on bees and their behavior was monitored.Parasitization caused changes in the levels of active genes in the brains of infected bees. Varroa altered the activity of 455 genes, including genes involved in GABA and serotonin signaling, while Nosema affected 57. Twenty genes were common between the two infections and several of the up-regulated genes are involved in oxidative stress, neural function and foraging behavior. Parasitized bees also tended to have a higher viral infection as well, adding to their disease burden, — even if they did not have physical symptoms.Hydrocarbons on the cuticle of bees provide a ‘family’ scent allowing bees from the same hive to recognize each other. The levels of these chemicals was altered by infection with either the endo- or ecto-parasite nevertheless infected bees were treated as normal by other bees — social interactions including antennal contact, grooming, feeding, and vibration, continued — and they were not expelled from the hive.Dr Cynthia McDonnell who led this study commented, “Parasitized bees tend to leave the colony earlier to perform foraging activity, which could lead to a significant depopulation of the colony. However, very few studies have analyzed the impact of parasites on bee phenotypes, e.g. brain and behavior. …

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