Checking for dead bees on the OMF

[Amari]

Today I removed the mouse excluders to check that dead bees were not accumulating on the OMF and maybe blocking the exits. I used the curved end of a long hive tool to 'sweep' the OMF. Five hives had few or no corpses, three hives each had more than 100 corpses. From two of these hives I took samples home and prepared Nosema slides (20 abdomens ground with 4ml water). Both samples revealed several scores of Nosema 'rice grains' per x400 field. All hives had been fed with thymolated Ambrosia in September preceded by ApilifeVar. Not surprisingly maybe the three colonies were among the weakest in the apiary of nine.
Disappointing that three colonies seem diseased despite my best efforts. I would be interested to hear of others' experiences. Has anyone else tested for Nosema on dead bees at this time of year?

 

[REDWOOD]

What type of nosema was it ?

 

[Amari]

Don't know. I was taught that x400 is insufficient to distinguish between the two species

 

[REDWOOD]

Apis is more rounded like pudding rice where as ceranea is more elongated, It is difficult to distinguish at that magnification, can you go up a bit ?

 

[Amari]

I've not tried an oil-immersion lens - if that's what you mean, since A level zoo/bot in 1959. Even so I would need an adjacent comparison. Anyway, what's the relevance of your query?

 

[drex]

Amari - Glad to hear you are getting on Ok with the scope. Nosema testing is very subjective, and it was only after I had done many such tests I started to get a feel for the degree of infection. When I sat my microscopy exam, the nosema slide we had to make up at the time was so heavily infected the examiner asked if he could keep it for teaching purposes. We chatted about it's chances of survival. I told him the hive seemed perfectly healthy - it was a thriving colony in a TBH. He felt it was doomed to die off over winter. However this summer it was a good strong colony again, with low nosema counts!
PS. The gallery on beebase has slide showing the differences between Apis and Ceranae, but I would still not feel confident to pronounce definitively

 

[Amari]

Thanks Drex. But are there any practical implications of differentiation?

 

[drex]

From bee base:

standard adult disease screen - under the light microscope the spores of N. apis and N. ceranae appear as white/green, rice shaped bodies. However, both species are virtually identical when viewed using conventional microscopy, but can be distinguished by an expert eye. However, more accurate discriminatory tests are available which detect differences between the two species using genetic methods.
Symptoms of Nosema
There are no outward symptoms of the disease. Dysentery is often seen in association with N. apis infections; this may be seen as 'spotting' at the hive entrance or across the frames. The dysentery is not caused by the pathogen, but as a consequence of infection and can be exacerbated during periods of prolonged confinement during inclement weather, especially during the spring. This can lead to the bees being forced to defecate in the hive, therefore contaminating it further.

In Spain it has been reported that N. ceranae infections are characterised by a progressive reduction in the number of bees in a colony until the point of collapse. The beekeeper may also see a significant decline in colony productivity. In the final phase of decline, secondary diseases frequently appear, including chalk brood and American foul brood. Eventually the affected colonies contain insufficient bees to carry out basic colony tasks and they collapse. Mortality in front of the hives is not a frequent symptom of N. ceranae infection. Dysentery and visible adult bee mortality in front of the hives are reported to be absent in N. ceranae infections. Colonnies can fail to build up and even dwindle away. This can sometimes be rapid or take place over several months.

Nosema is readily spread through the use of contaminated combs. The spores can remain viable for up to a year, it is therefore important not to transfer contaminated combs between colonies and as always to practice good husbandry and apiary management, maintaining vigorous, healthy stocks, which are better able to withstand infestations.

 

[Tom Bick]

It may not be all bad news. If you followed the thymol recipe from the forum then it may have an affect but will need time to work. First your bees will need to eat the thymol syrup and the bees may be preferring honey stores right now. Secondly the thymol is thought to work by blocking the spores from developing into nosema do you may see the spores in the dead bees for some time but the colony is not becoming more infected. It's a bit of a fingers crossed situation hoping the infection was not that high but you have probably done all you could given the time of year.

 

[Amari]

Thanks Drex and Tom

 

[alanf]

,,,But are there any practical implications of differentiation?

There was a lecture at the 2013 national Honey Show by Robert Paxton, "Nosema, a pervasive and persistent parasite of the honey bee" unfortunately not one that has been released as video, so I'm recalling what I can of it. One of the differences that I haven't seen summarised so well elsewhere is temperature/climate sensitivity. Nosema apis infections tend to vary seasonally, building up in winter confinement to peak in Spring but often clearing in summer (if the colony is otherwise healthy). Nosema ceranae is more persistent though seasons but reproduces best at warmer temperatures and reaches peak infections in summer.

N ceranae spores are more sensitive to freezing, so a week in a freezer would be a precaution if you had to use comb again. Acetic fumigation seems to be effective against both, and hives can be infected with both species. Robert Paxton's lecture included some distribution work, N. apis is a problem throughout UK, but relatively less prevalent as you go South - and that continues to colonies around the mediterranean. N. ceranae is more frequent the further South you go. First European discovery in Spain for instance but much rarer than apis in Scotland and elsewhere in North Europe.

 

[Amari]

Thanks for that.

 

[user 6228]

two papers indicate temperature effects nosema.

Nosema ceranae infection intensity highly correlates with temperature
Yue-Wen Chen a, Wei-Ping Chung a, Chung-Hsiung Wangb, Leellen F. Solter c, Wei-Fone Huang

10.1128/AEM.02908-08. 2009, 75(8):2554. DOI:
Appl. Environ. Microbiol.
Garrido-Bailón, Laura Barrios and Mariano Higes
García-Palencia, Pilar Marín, Cristina Botías, Encarna
Raquel Martín-Hernández, Aránzazu Meana, Pilar
Effect of Temperature on the Biotic Potential of Honeybee Microsporidia