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Introduction to the NHBS
The National Honey Bee Survey (NHBS) started in 2009 to establish baseline data for the presence or absence of invasive honey bee pests in the U.S. in response to declining colony health. The primary goal was to verify the absence of exotic threats to honey bees, including the Tropilaelaps mite, Slow Bee Paralysis Virus, and Apis cerana (Asian honey bee), as current U.S. international trade agreements state that import permits may only be rejected if a nation has a disease, parasite, or pest of honey bees that is not found in the U.S. Since then, the annual survey has capitalized on the information gathered to include other honey bee parasites and diseases known to be present in the U.S. This has allowed for the interpretation of ongoing and future epidemiological studies. While initially there were three participating states, there are currently 40 states and territories involved in the sampling effort.
This nationwide surveillance network is conducted under cooperative agreements between the USDA Animal Plant Health Inspection Service (APHIS) and the states, with sample collection coordinated by state apiary specialists and university scientists. Analyses are coordinated by the University of Maryland. Participation by commercial beekeepers is completely voluntary. Eight colonies are sampled from within an apiary to generate three composite samples: live adult bees are collected for the analysis of viruses; adult bees are collected in alcohol to detect and quantify varroa, Nosema, and A. cerana; and a sample of brood-frame debris to detect Tropilaelaps. Starting in 2018, brood comb samples were collected for wax pesticide residue analysis from five of the apiaries.
Hawaii’s Importance Nationally
Hawaii boasts the most productive honey bee colonies in the nation, producing twice as much honey as the national average, and is home to the world’s largest queen bee producers, exporting 75% of locally reared queens to Canada and 25% to the mainland U.S. (accounting for 70% of all queens in the mainland U.S.). Queen production alone is valued at $10 million annually in the state. This industry exists in Hawaii because Africanized bees are absent and the subtropical climate supports year-round queen rearing, allowing early spring shipments to quickly replace overwinter losses.
In addition to the economic value of Hawaii’s beekeepers to the U.S. as a whole, it is the only state that has varroa-positive and -negative regions (islands), providing a unique opportunity to study the dynamics of the viral landscape with and without varroa mites, which are notorious vectors of a number of viruses. The geographic location midway between the mainland U.S. and Asia also make the state an important sentinel for intercepting emerging exotic pests. The inclusion of Hawaii in the NHBS is critical for understanding disease dynamics in the state and broader disease and pest trends across the U.S.
More information about the Survey and summaries of national data are available at https://beeinformed.org/aphis-nhbs/.
Summary of 2009-2018 Results for Hawaii
Hawaii has been a participating state in the NHBS since its inception in 2009. Below are a summary of the results for Varroa destructor mite counts associated with the survey, Nosema, eight viruses, and pesticide residues from beeswax. Of note is that apiaries were not sampled from every island every year. Data are missing from some years, which are noted under respective parasites and viruses. Further, the same apiaries were not necessarily sampled in subsequent years. Thus, these data only represent a rough analysis of trends in parasite and viral landscapes in Hawaii.
Over 20 viruses have been reported to infect honey bees worldwide. The NHBS has evaluated the presence of Acute Bee Paralysis Virus (2009 – present), Black Queen Cell Virus (2011-2012), Chronic Bee Paralysis Virus (2009 – present), Deformed Wing Virus (2009 – present), Israeli Acute Paralysis Virus (2009-present), Kashmir Bee Virus (2009-2010, 2012-present), Lake Sinai Virus 2 (2013-present), Moku Virus (2017-2018), Slow Bee Paralysis Virus (2013-present), and Varroa Destructor Virus-1 (2016-present). Prior to 2013, viral loads were not quantified in bees, but recorded as presence absence only. Although the survey has not detected Slow Bee Paralysis Virus or the closely related Moku Virus in Hawaii, Mordecai et al. (2016), who first described the Moku Virus, did detect it in honey bees and Varroa mites on the Big Island.
Though there is more than one mechanism by which viruses are transmitted between honey bees, infections in colonies are often associated with infections and infestations of other pathogens and parasites, particularly varroa mites. Most viruses in honey bees persist as unrecognized infections and it is impossible to differentiate mixed infections from field observations alone. Detection and identification of viral infections requires laboratory based testing. Because viruses cannot be treated with drugs, effective viral treatments focus on minimizing other stressors in the colony so the honey bees may recover through good beekeeping practices. These include disinfecting hive tools between colonies with bleach, locating apiaries in areas with sufficient nutritious forage and supplementing during periods of dearth, replacing failing queens and old comb, and controlling parasitic mites. RNAi antiviral technology is a promising treatment, but products are not yet commercially available.
In the following figures, the proportion of colonies testing positive for the respective viruses are displayed as pie charts below the sampling year (x-axis). The number of viral copies per bee are displayed as bars per sampling year (y-axis), and colored by the island from which samples originated. Viruses were quantified in a lab at the University of Maryland, with one sample consisting of a homogenate of honey bees collected from eight colonies within a single apiary. Therefore, testing occurred at the apiary level. Because the national statistics represent an average of all samples from 2013-present, this is only displayed on the graphs for 2018. Solid lines above each sampling year indicate the Hawaii state average for that virus in that year. Low replication between locations precludes the ability to conduct statistical analyses on the data at this time.