Nosema ceranae is a fungus that infests the honey bee gut, causing dysentery. Honey bees in the U.S. coexisted with Nosema apis for years, but Nosema ceranae has challenged our bees much more. For an excellent summary of how Nosema works, visit the university Extension's page titled "Nosema Microsporidia: Friend, Foe, and Intriguing Creatures" (click here, or visit:
http://www.extension.org/pages/31234/nosema-microsporidia:-friend-foe-and-intriguing-creatures#.Uin9mEbn_IU. Also, see our "Bee Losses" page: click here.
The Weaker Sex: Male Honey Bees More Susceptible Than Females to Widespread Intestinal Parasite”: 18 Jan 2014, Science Daily.
We knew it was rough being a drone. Now Swiss researchers have discovered that drones are “much more susceptible” to Nosema than workers. The “delicate nature of male honey bees” is owed partly to their haploid nature: with only one set of chromosomes, scientists hypothesize that they are more predisposed to disease because they can’t “mask mutated genes” on a matching chromosome copy, as females can.
The new finding may suggest a reason for the spike in queen failure that many beekeepers have observed. The researchers note that “Without strong, fit drones, the chance of successful matings with queens could be severely compromised,” in turn compromising colony health through queens’ failing to obtain “sufficient quantity and quality of sperm from drones during mating.”
“Swedish researchers develop medicine to protect bees from deadly diseases,” 29 Sept 2013, AFP / Fox News:
In Sweden, Lund University microbiologists have patented a new medicine called “SymBeeotic,” which they say “boost[s]” bees’ immune responses and may save beekeepers from suffering colony losses at the rates seen in recent years. SymBeeotic is synthesized from lactic acid bacteria, taken from “stomachs of healthy bees.” Dr. Alejandra Vasquez, co-creator of the drug, notes that "[t]he bacteria in this product is active against both American and European foulbrood disease." Using SymBeeotic as a preventative may relieve beekeepers of any need to treat with antibiotics and risk increasing antibiotic resistance.
“Pathogen webs in collapsing honey bee colonies,” 21 Aug. 2013, PLoS Pathogens
A new study by Jeff Pettis, Dennis Van Engelsdorp, and colleagues “suggest[s] a distinct pathogen signature” in honey bee colonies suffering CCD, marked by “higher levels of several RNA viruses.” These virus levels were significantly higher, as much as double the virus levels in colonies that died out from causes other than CCD. Further, the study suggests “synergistic impacts” on bee health when additional factors challenge the bees: specifically Nosema. The study “showed a significant positive correlation with a diverse set of RNA viruses” when Nosema was present. Finally, the study discovered two new “groups of RNA virus that clustered phylogenetically with Chronic bee paralysis virus (CBPV).”
To read more, visit: http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=267552
“Nosema ceranae Escapes Fumagillin Control in Honey Bees,” March 2013, PLoS Pathogens
Speaking of Nosema, those of us who use fumagillin – the sole antibiotic that enjoys FDA approval for treating Nosema – will be concerned by this study. Researchers found that since the drug becomes “diluted in hives over the foraging season, both the bees and the nosema spores continue to be exposed to it," though in smaller amounts. What’s new: even these smaller amounts may cause trouble in the form of resistance by the microsporidian: spore production grew “up to 100% higher than that of infected bees that have not been exposed to fumagillin.” Nosema ceranae rebounded faster following fumagillin treatment than did Nosema apis.
The study sampled bees treated with fumagillin at various levels of degradation: they did not find significant differences in colony death among those levels, but concluded that the persisting presence of fumagillin enabled greater long-term spore production. The researchers conclude that “the current application protocol for fumagillin may exacerbate N. ceranae infection rather than suppress it.” Since the usual practice is to treat with fumagillin every six months, and since that window gives Nosema ample time to rebound, beekeepers may have to decide whether they want to medicate more often to try to prevent this or stop using the antibiotic.
To read more, visit: http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1003185
Crop Pollination Exposes Honey Bees to Pesticides, Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae
On July 24, Jeffrey S. Pettis, Dennis vanEngelsdorp, and colleagues published a study showing how interactions between fungicides and pesticides weaken honey bees, making them less able to resist Nosema ceranae. The study explored how “field-relevant combinations and loads of pesticides affect bee health.” Researchers gathered pollen from bee colonies in seven major crops –almond, apple, blueberry, cranberry, cucumber, pumpkin, and watermelon – and studied the three strongest foraging hives in three fields of each crop. They then inserted pollen traps to sample from what crops bees were bringing back pollen and study the levels of pesticide and fungicide loads in that pollen.
Three major results have implications for beekeeping. First, just because honey bees were placed in a field of target crops didn’t mean they pollinated those crops. Often, they didn’t bring back any pollen from target crops, preferring weeds and wildflowers. However, the pollen they brought back still contained significant loads of pesticides and fungicides used on the target crops: therefore, beekeepers are urged to look not only at what is sprayed on crops to which they bring their bees, but also drift onto adjacent fields. The two target plants that honey bees did consistently pollinate were almonds and apples: the researchers commented that these are two plants that co-evolved with honey bees as their natural pollinators in the Old World, whereas crops native to the Americas made up a very small portion of the pollen trapped in this study’s samples. The study focused on pollen collected from bees’ corbiculae in traps, not nectar, though, so the bees could have come in contact with pesticides from target crops even when pollen from those crops didn’t show up in samples.
Second, fungicide showed up “at high levels” in both target and non-target plants. Two fungicides in particular, chlorothalonil and pyraclostrobin, and two miticides used against Varroa mites, amitraz and fluvalinate, had a significant impact on the bees’ resistance to infection by parasites. These fungicides also significantly increased bees’ susceptibility to Nosema: bees that consumed these fungicides were “more than twice as likely” to show Nosema infection than bees that hadn’t. A similar rate of susceptibility to Nosema appeared in bees who came in contact with the miticides, suggesting the importance of rotating old comb out of hives to minimize danger to bees and resistance by mites.
Last, this study is the first to document the impact of “real world pollen-pesticide blends” on honey bees. Even pollen from non-target plants was contaminated: 35 pesticides were found, including several whose concentrations were “higher than their median lethal dose.” 22 of the 35 pesticides were associated with a significantly higher than normal risk of Nosema infection in the bees. Also, though neonicotinoids only entered the sample bees’ colonies via pollen from apples, the interactions between fungicides and these pesticides caused problems. Also, when bees are exposed to multiple pesticides, the amount of each required to be a lethal dose drops; multiple exposure also increases queen supersedure. The researchers also noted the pesticides’ “sub-lethal effects on development, reproduction, learning and memory, and foraging behavior.”
To read the original study [PLoS ONE 8(7): 24 July 2013], visit: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0070182#authcontrib
Below, "U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) entomologist Jay Evans and postdoctoral research associate Ryan Schwarz use a microscope to look at spores of the honey bee fungal parasite Nosema ceranae, which can replicate in cells lining the honey bee gut on Oct. 25, 2011," Photo by Stephen Ausmus. Wikimedia Commons, license CC BY 2.0