A New Nosema
Bee Culture (February 2007) Vol. 135 (2): 18-21.
Dr. Malcolm T. Sanford
In the September-October 2006 issue of Vida Apícola, it is reported that beekeepers in Spain currently have been suffering a bout of disappearing disease (syndrome de despoblamiento de las colmenas). This means that for some unaccountable reason populations in beehives have been decreasing, but few symptoms exist other than the worker population simply has “disappeared.” The phenomenon is nothing new. It has occurred around the world, including the U.S., according to Dr. Hachiro Shimanuki, now retired from the USDA Agricultural Research Service (ARS) and is, "...a classic example of a misnomer. In the first place the bees disappear, not the disease, and in my opinion, the term is used as an umbrella for what may well be many maladies."1 Indeed subsequent extensive research has failed to isolate any disease organism in stocks that exhibited the condition. The symptoms are similar to other conditions described as "autumn collapse," "spring dwindling," "disappearing trick" (Australia), "mal de mayo" in some Spanish-speaking countries, and “May disease” in France.
The Spanish authors of the Vida Apícola article also report that several additional causal possibilities for large-scale losses exist, including pesticide-treated sunflower seeds. However, another possibility is being closely scrutinized, correlation with detection of Nosema ceranae. The name gives it away; the origin is Apis cerana, the same species that is the source of Varroa destructor. Thus, what the beekeepers of the world do not need, but has indeed been detected in Spain for the first time is a new kind of nosema disease. I say “new” because the symptoms appear to be different than for the traditional Nosema apis that is present in most, perhaps all, colonies of Apis mellifera worldwide. A summary of the 2005 article in Vida Apícola is also found on the World Wide Web.2
The authors conclude:
The November 2006 edition of The Beekeepers Quarterly3 takes up the story with a report by Dr. Robert Paxton, School of Biological Sciences, Queen’s University Belfast entitled “Nosema ceranae Spreads Rapidly Around the World.” An article currently under review for the Journal of Invertebrate Pathology will show that it is far more widespread than originally thought, and may be present in western honey bees across the New World, Europe and Asia.
A short history of the detection of this phenomenon is provided by Dr. Paxton. In 1995, Dr. Ingemar Fries of the Swedish Agricultural University visited China, where he described a new microsporidian, Nosema ceranae, in indigenous Apis cerana.4 The molecular sequence of Nosema ceranae has been published by the National Insitutes of Health (NIH).5 The ultrastructure and genetics were found to differ from Nosema apis, and Dr. Fries was able to experimentally infect Apis mellifera with this organism, but at the time little was made of this observation. However, in the Spring of 2005 Vietnamese researchers found both nosema types infesting western honey bees and this was confirmed by Dr. Paxton, who was able with colleagues to develop a rapid and accurate molecular detection system to differentiate the two species.
The activity above was followed by the report from Spain in Vida Apícola, indicating the parasite had “moved out of Asia,” and was being linked to massive colony losses. Subsequently, the organism has been found in France, Germany and Switzerland as reported at the 2nd European Apidology Conference in Prague.6
Dr. Paxton’s group solicited samples from around the world and found that Nosema ceranae probably “jumped host” from A. cerana to A. mellifera in the last ten years and has spread “remarkably rapidly.” It has now been found in North and South America, the Caribbean, across Europe and Asia, but not on the islands of Ireland and New Zealand. Definitive samples are still lacking from Africa, Australia and Great Britian. The conclusion: “However, given its rate of spread and occurrence even on isolated islands of the Danish archipelago, it is quite possible that N. ceranae is, or will soon be, spread truly worldwide.”
Dr. Paxton states that the implications for beekeeping with the western honey bee (Apis mellifera) are profound. He says we need to understand how virulent this organism is on its new host, and that correlation between N. ceranae and colony mortality in Spain is not proof it is the culprit. Many other factors could contribute to honey bee colony population decline as noted above by Dr. Shimanuki. The organism could also have multiplied in colonies dying from other causes, and there may be a synergistic relationship between the organism and other factors leading to increased colony mortality.
Questions put to Dr. Paxton by the editor of The Beekeepers Quarterly reveal that both nosemas can exist in an individual bee, and in quite high numbers. He believes that his first thought that N. ceranae was replacing N. apis is not correct, but that N. ceranae is being reported more readily, giving the appearance it is more abundant. In addition, control at the present time is unknown, although Spanish scientists appear to have used Fumidil B® with some success.
Dr. Paxton says that although the Spanish group of scientists that published in Vida Apícola is looking into control measures, much more needs to be done and now. Thus, he concludes: “I hope the relevant authorities and beekeepers take note. Forewarned is forearmed.”
Perhaps beekeepers can best prepare for the coming of a new nosema by reviewing what they know about the more common species, Nosema apis. Wikipedia.org has plenty of information on this organism, including sites linked to the Universities of Georgia and Florida.7
From the University of Georgia site:8 “Nosema is caused by the microsporidian Nosema apis, a small, unicellular organism that is unique to honey bees; it is the most widespread of the adult honey bee diseases. Nosema infects the epithelial cells of the honey bee ventriculus thereby causing dysentery. Queens, drones and workers are all susceptible to Nosema. The spore from the parasite must be ingested by the bee in order for infection to occur. The spore germinates in the midgut, penetrating the cell lining as it multiplies, reducing the life span of the honey bee. Nosema spores are spread to other colony members through fecal matter. Colonies in northern climates are more seriously affected than colonies in the south because of the increased amount of time bees are confined in the hive. Nosema, if left untreated, can cause queen supersedure, winter kills, reduced honey yields and dwindling populations. It is more common during times of confinement like winter and spring.
“The symptoms include: slow spring build-up (best indicator) disjointed wings, distended bloated abdomen, a lot of yellow streaks on the outside of colony and crawling bees outside of the hive. These symptoms may also be associated with tracheal mites.
“Do not overlook this disease just because it is not common in the south. Prevention is the best way to keep your bees free of disease. Some good beekeeping practices are to avoid placing hives in low spots and to provide ample ventilation. Treat with Fumidil-B® according to the manufacturer's instructions.”
And from the University of Florida:9
“Suggested feeding recommendations for fumagillin for nosema control are as noted on the label of the product (Ed note: check beekeeping catalogs for brand names of products containing the active ingredient fumagillin like Fumidil-B® or Fumigilin-B® ); feeding is generally preferable in the fall of the year. Fumagillin is active only in syrup; dusting is not recommended. Because nosema is more virulent in confined bee populations, it generally is considered much more of a problem in temperate areas.
Recommendations by the Minnesota State Inspection Service in 1980 as published in the Minnesota Beekeepers Magazine, Vol. 34, No. 3 suggest the following feeding schedule.
1. Feed every two or three years if a colony averages 0.11 to 1.0 million spores per bee; this level may result in decreased honey production.
2. Feed once every two or three years if a colony averages 1.1 to 5.0 million spores per bee; this level may result in reduced honey yield and increased spring and winter loss as well as queen supersedure.
3. Feed two years in succession if a colony averages 5.1 to 10.0 million spores per bee.
4. Feed every year if a colony averages in excess of 10.0 million spores per bee.
“Florida research over the years indicates a general infestation of 2 million spores per bee with maximum seen of 36 million per bee. Feeding fumagillin at even the lowest level can result in substantial increases in honey production.
“Nosema infected equipment can be decontaminated by use of heat (120°F for 24 hours). The temperature must not exceed this or the combs might melt. The technique must be used on empty comb only. Fumigation with acetic acid and ethylene oxide have also been reported and recommended.”
It may not be apparent to beekeepers in the United States, but over the last two decades beekeeping in Europe has developed into a dynamic, modern activity. Italy and France, where this author spent sabbaticals in the 1980s10 and 1990s,11 have always been leaders in apicultural affairs, but it now looks like Spain may be catching these traditional European leaders. Exposure to the influential Spanish journal Vida Apícola as revealed above shows some of this dynamism. In the January-February 2006 edition, the magazine’s director, Ms. Silvia Cañas, writes an editorial inaugurating a new section of the publication as part of the activities of the journal’s club. She provides ten reasons for becoming a member from receiving the bi-monthly magazine to free technical service. Included is free access the magazine’s recently-launched digital version.12 Some beekeeping associations and publications in the U.S. might benefit from studying this model as a way to attract readers and increase membership.
The same edition of Vida Apícola contains a calendar of beekeeping events across the country, including the regions of Seville, Tenerife (Canary Islands), Zaragoza, Cáceres and Córdoba. And in the March-April edition there is an extensive review of 8th Ibero-American Apicultural Congress at the 25th meeting of the beekeeping exposition at Castilla de la Mancha. For those with an interest in these events, I have published reviews of both the 5th and 6th Ibero-American congresses13 and the 1998 Spanish meeting in Castilla de la Mancha.14
Editor Flottum believes that this story may be a U.S. scoop, for he has not seen any description of a new nosema reported in other domestic publications. We are led to conclude that whereas in the past it might be possible to at best delay reading, or at worst ignore (because it appears in a foreign language) what is happening elsewhere in global beekeeping, this is no longer the case.