Randy writes
> Peter, have you posted to the List the recent paper about the different strains of nosema?

No, but I will tell you why. About two weeks ago I stumbled upon
several studies that seemed to contain some startling revelations. Not
wanting to overreact, I sent copies off to various people to stimulate
discussion, but nothing much came of it. SO, I'm thinking, maybe I'm
the only one interested by this stuff. Also, I can't really distribute
these papers, as they are copyrighted. I can only post excerpts.

What I am seeing is that nosema is a highly variable organism that can
infect multiple hosts. Traditional species distinctions were made on
the basis of observable physical, behavioral, geographic, or
pathological differences. Later species distinctions have been made on
the basis of genetic dissimilarities that are often subsequently
called into question.

Bottom line is: I am not sure that the new nosema is in fact new, or
if it has been here all along, or is another variation of nosema spp.
Also, I wonder if the PCR tests are distinguishing characters that may
or may not have meaning in terms of the behavior or pathology of the
various so-called species or varieties. Finally, I don't know if
anybody but you and me even cares about this stuff

Excerpts from recent research


Both species [N. apis and N. ceranae] infect the ventriculus of adult
honey bees and are transmitted horizontally via spore ingestion, for
example whilst workers clean combs of infected faeces.  Of great
concern is the apparently higher mortality we observed that N. ceranae
imposes on A. mellifera compared to N. apis.  Colony level infection
experiments in the field are now required to demonstrate a causal link
between N. ceranae infection and colony collapse.

N. ceranae and N. apis may have both existed in A. mellifera for quite
a long period. The morphological records of N. apis show high
variability and N. ceranae has been found in Europe and on Martinique
Island (unpublished data). The origin of N. ceranae will have to be
elucidated by further research.

* * *

The full length rRNA genes of N. ceranae has also been examined and
found identical to those of N. apis. Comparing the rRNA sequences of
the isolates from A. mellifera and A. ceranae, it showed no difference
in phylogeny, and it may represent no differentiation between the
isolates from different hosts. Moreover, the N. ceranae isolates from
different areas of the world were obtained through abroad researchers,
and these isolates showed little difference in IGS phylogenetic
analyses.

Recent researches showed that there may be more than two species
causing honeybee nosema disease, and it raised the questions about the
accuracy of records that attributed the Nosema species infection of A.
mellifera. Therefore, a multiplex PCR diagnosis method that could
discriminate N. apis and N. ceranae was established in this study.


* * *

The authors compared the morphological and ultrastructure characters
between N. apis and N. ceranae and found that the SSUrRNA sequences
differed between the two species. It is not known whether N. ceranae
is a new, emerging honeybee parasite or is a naturally occurring
species that had been overlooked due to its morphological similarity
to N. apis

In Spain, the ratio of N. ceranae infection in colonies infected with
nosema disease was reported to be as high as 90% (Higes et al., 2006).
In the samples from Taiwan and Martinique, only N. ceranae was
recovered.

An unidentified microsporidium from France shares 96% identity with N.
ceranae and 94% identity with N. apis. Moreover, the ITS region was
sequenced and aligned with the other ITS sequences (Fig. 3); there
were noticeable differences from both N. apis and N. ceranae. The
unique rDNA arrangement of N. ceranae was not found in this species.
The unidentified species found in France suggested that in addition to
N. ceranae and N. apis, other Nosema species might be infecting A.
mellifera. The rDNA sequence (including SSUrRNA and ITS) of the
unidentified species is an intermediate between those of N. apis and
N. ceranae, generating interesting questions about in nosema disease
research

* * *

Characterisation of microsporidian species and differentiation among
genetic variants of the same species has typically relied on ribosomal
RNA (rRNA) gene sequences. Our data on within-genome rRNA variability
call into question the usefulness of rRNA sequences to characterise
intraspecific genetic variants in the Microsporidia.

--
Peter L Borst
Danby, NY  USA
www.people.cornell.edu/pages/plb6

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