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U.S. Department of Health and Human Services

Animal & Veterinary

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Mysterious Honeybee Deaths Leave Sting on Agriculture

by Walt D. Osborne, M.S., J.D., Assistant Editor
FDA Veterinarian Newsletter 2007 Volume XXII, No III

Scientists and researchers across the Nation are working diligently to try to understand why the number of honeybees has been declining recently at an alarming rate. As many as 35 U.S. States, as well as Canada and countries in Europe and Asia, have witnessed this mysterious decline this past winter (2006-2007). Experienced beekeepers are finding their once-thriving hives empty and abandoned. Investigations suggest that outbreaks of unexplained colony death of honeybees have been ongoing since 2004, and historical reports of similar losses indicate that such losses have occurred as far back as 100 years or more. The cause could be a parasite, a virus, a fungus, a bacterium, a toxin, or other stress; but for now, no one cause has been isolated. The phenomenon has been termed Colony Collapse Disorder (CCD).

Symptoms of CCD

A colony with CCD is generally characterized by all of these conditions occurring simultaneously: (1) complete absence of adult bees in colonies, with little or no build-up of dead bees in or around the colonies; (2) presence of capped brood (cells capped with wax over pupae) in colonies—bees normally will not abandon a hive until the capped brood have all hatched; (3) presence of food stores, both honey and bee pollen, which are not immediately robbed by other bees and which, when attacked by hive pests such as wax moth and small hive beetle, the attack is noticeably delayed. Precursor symptoms that may arise before the final colony collapse are the following: insufficient workforce to maintain the brood that is present; workforce seems to be made up of young adult bees; the queen is uncharacteristically evident outside the hive; and the colony members are reluctant to consume provided feed.

Importance of honeybees

Bees are vital for the pollination of more than 90 fruit and vegetable crops worldwide, including almonds, peaches, soybeans, apples, pears, cherries, raspberries, blackberries, cranberries, watermelons, cantaloupes, cucumbers, and strawberries. The economic value of these agricultural commodities is somewhere in the area of almost $15 billion in the United States alone. Aside from agricultural crops, many native plants are also pollinated by honeybees, thereby illustrating how the entire ecosystem is being affected by this serious malady.

What is killing the bees?

According to Feedstuffs Newspaper, up to 1 million out of a total 2.4 million honeybee colonies in the United States have died out this past winter. Both tracheal mites (Acarapis woodi) and varroa mites (Varroa destructor) have threatened the bee industry since the 1980s, with significant colony die-offs in the winters of 1995-1996 and 2000-2001. The mites feed on U.S. honeybees and act as a vector for a number of bee viruses. Miticides have been used to combat these pests, but over time, the mites develop resistance. Also, miticides can only be used at certain times of the year because, if used during a nectar flow, they could contaminate the honey crop. In addition, there is evidence that miticides can accumulate in the bees’ wax combs to levels that could be harmful to the bees themselves. Tracheal mites do not appear to be a factor in the current die-off. Varroa mites are still a problem, but bees appear to be equally affected in both weak and strong colonies.

In the spring of 2007, a team of scientists from Edgewood Chemical Biological Center and the University of California, San Francisco, identified both a virus and a parasite that could be behind the die-offs of honeybee colonies. Using a new technology called the Integrated Virus Detection System, which was designed for military use to rapidly screen samples for pathogens, the scientists isolated the presence of viral and parasitic pathogens. The extent of the problem is unknown and is still being studied, as are other detection activities.

Another possible culprit is a class of insecticides known as neonicotinoids, which have been widely detected on pollen at low concentrations in other countries experiencing die-offs of honeybees. Neonicotinoids are systemic pesticides used on plant seeds. When the seeds mature, the pesticide manifests itself throughout the plant. When an insect ingests any part of the plant, it gets a dose of the neurotoxin that can cause a quick and lethal breakdown of the insect’s nervous and immune systems. As a result, a bee’s ability to learn can become impaired, leading some scientists to suggest that exposed bees may leave the hive and literally not be able to find their way back. One of the chemicals in this class, imidacloprid, is marketed in the United States for use as an insecticide on food crops, as well as to control termites and fleas. Imidacloprid was banned in France in 1999 as a suspected cause of drastic and mysterious die-offs in honeybees. Differences of opinion abound in bee circles, and a direct causal link between the chemical and bee mortality has not been made.

But this said, there seems to be no one singular disease acting as a causal agent of colony deaths, and approximately 25 percent of the bee deaths cannot be attributed to mites or any other known pest. Such things as genetically modified foods, mites, pathogens, pesticides, and electromagnetic radiation from cell phones have all been suggested as possible causes of the bees’ demise, but the actual causes remain a mystery.

The Colony Collapse Disorder Working Group, a collaboration of researchers from around the country, including Pennsylvania State University, the U.S. Department of Agriculture (USDA), the Mailman School’s Greene Lab, the Florida Department of Agriculture and Consumer Services, the University of Illinois, the University of Delaware, North Carolina State University, and others are working to identify potential causal factors common to CCD colonies and devise preventive measures to disrupt the disorder, with the ultimate goal of ensuring strong honeybee colonies for pollination and honey production.

The role of FDA

Honey is regulated by FDA as a food, and as such, it cannot be marketed in this country unless it is shown to be safe, sanitary, wholesome, and labeled in a truthful manner. So, FDA’s interest in the bee industry is basically two-fold: ensuring the quality and purity of honey and ensuring the health of honeybees. Honey is different from most food products that may contain animal drug residues. Unlike seafood, meat, and milk that contain large amounts of protein and fats, honey contains mostly sugars. It also has natural antimicrobial properties. As a result, many of the traditional approaches used to isolate drug residues do not work for honey. In 2006, researchers from FDA’s Center for Veterinary Medicine developed a provisional multi-residue method for 17 drugs in honey. The method uses liquid chromatography-tandem mass spectrometry, both to confirm the identity of the drug and to determine the amount of drug residue present. The USDA Beltsville Bee Laboratory, in an ongoing collaboration with CVM, is generating needed biologically incurred residue samples for the drugs in the multi-residue method.

CVM’s Office of Research was also involved in analyzing protein supplements fed to some honeybee colonies to determine whether they could have been contaminated with melamine. Melamine was involved in a recent large-scale pet food recall. Preliminary results found no evidence of melamine in any of the samples tested. Again, this work was done in cooperation with the Beltsville Bee Lab.

Other CVM offices are following this problem closely and are ready to assist the country’s beekeepers however they can when the causative agent of this syndrome is identified. If a medical need is identified, recent legislation will enable the Office of Minor Use and Minor Species (MUMS) Animal Drug Development and the Office of New Animal Drug Evaluation to encourage pharmaceutical sponsors to obtain approvals for new treatments. The MUMS Health Act was enacted into law on August 2, 2004. It helps make more medications legally available to veterinarians and animal owners to treat minor animal species and uncommon diseases in the major animal species. Some animals of agricultural importance are also minor species, and these include honeybees.

American Foulbrood (AFB) is an infectious brood disease caused by the spore-forming bacterium Paenibacillus larvae. Although it is not believed to be responsible for CCD, it is the most widespread and destructive of the brood diseases, afflicting queen, drone, and worker larvae alike. Adult bees, however, are not affected by AFB. To date, FDA has approved two drugs to prevent and/or control AFB in honeybees: Terramycin® (oxytetracycline) Soluble Powder (for prevention and control) and Tylan® (tylosin tartrate) Soluble (for control). This latter drug is used only in cases of AFB that have been identified as resistant to Terramycin® by the State apiary inspection service.

FDA’s Office of MUMS and incentives from the MUMS Act could be helpful if it turns out that the cause of CCD could be addressed through a new animal drug approval.

Possible Funding for research

On June 26, 2007, Senators Barbara Boxer, John Thune, and Bob Casey introduced legislation to help research, protect, and maintain America’s bee and native pollinator population and ensure the viability of crops that rely on them for pollination. The Pollinator Protection Act would authorize $89 million in Federal funding for research and grant programs at the USDA over 5 years for work related to maintaining and protecting bees and native pollinator populations. This bill not only addresses CCD in honeybees, but also the decline of native pollinators in North America. This bill would enhance funding for research on the parasites, pathogens, toxins, and other environmental factors that affect honeybees and native pollinators. It supports research into the biology of native pollinators and their role in crop pollination, diversifying the pollinators upon which agriculture relies.


As the reader can see, the importance of honeybees cannot be taken for granted. Equally important are the collaborative efforts by government, academia, and the bee industry to try to determine the cause or causes of CCD and how best to tackle this mysterious problem as a means to ensure the continued health of the honeybee and, in turn, the health of the food supply so dependent on these amazing insects. While many of us may fear a bee’s sting, even scarier may be the “sting” on our Nation’s food supply if the honeybee population continues to decline.