I have forwarded the discussion about nosema to Ingemar Fries at the
Department of Entomology, when he has been working on the subject and
is able to give a view of the situation here in Sweden.
 
Here comes his answer;
 
 
There are no specific clinical symptoms connected with N. apis.
infections.
Heavy infections are often correlated with dysentery but the reason for
this is not that nosema infections cause dysentery, but rather that when
dysentery occurs, the disease is aggravated and effectively spread in
the
honey bee colony. To diagnose N. apis infections microscopical
examination
of crushed bees, the ventricular content, or the fecal matters is the
most
simple way. The often referred to technique to visually inspect the
midgut
may sometimes be deceptive. The midgut may look abnormal without having
N.
apis infections and it is only severe infections that can be detected
this
way. A visual test has been described that can detect heavy infections,
but
it requires special test tubes, staining, and over night storage of the
material. Thus, examination in the microscope remains the best way to
determine if nosema disease is a problem in the apairy. A composite
sample
of bees can be used for each colony to be examined. And for practical
purposes it seems to be sufficient to divide the infection level into a
few
broad classes where only the severe infections will prove detrimental to
colony development and honey yield.
 
>Has there ever been any fumagillan resistance noticed?
 
There has been one attempt to monitor if fumagillin resistance can be
provoked in N. apis (Gross, K P; Ruttner, F (1970) Entwickelt Nosema
apis
Zander eine Resistenz gegen|ber dem Antibiotikum Fumidil B? Apidologie
1:
401-422.). No increased tolerance to fumagillin in the parasite has been
seen after long term exposure. The fact that the product now has been in
use for several decades without loss of effect also indicates that the
parasite is very slow or unable to develop resistance to this drug.
 
>Is there any alternative treatment if resistance does develop?
>
>What biological control alternatives are available?  (I was under the
>impression that the bees would recover on their own, but with a reduction in
>strength and therefore yield that season.  I could be quite wrong,  and I do
>not know if untreated hives are more likely to harbour "spores" that will
>reinfect them in winter conditions.  Nosema is a "sporozoan" ??, so I assume
>it has spores?  :)
 
The spores of the parasite is transmitted on soiled comb and picked up
by
new bees as the combs are cleaned. The spores remain viable on the combs
in
fecal deposits long enough to be transmitted between seasons. A good way
of
decreasing the probability to maintain supplies of infective spores in
the
colonies is to ensure that the bees are not wintered on combs where bees
have been kept over winter before (the risk of fecal deposits is larger
on
such combs). And if such combs are used, the practice to decontaminate
the
combs with acetic acid or heat treatment is recommended. If nosema
disease
is a problem, we also have good results with the Norwegian practice to
winter the bees on comb foundation. This lowers the probability of
detectable disease the following spring.
 
<--My explanation--Norwegian beekeepers shake bees into a box with only
foundation and give them sugar syrup that makes them draw out the
foundation
and fill it with feed in clean combs.-->
 
>What is the situation in Sweden and New Zealand, where other antibiotics are
>banned? Is fumagillan banned as well?
 
Fumagillin is not allowed in Sweden, nor is any other antibiotic for use
in
bee hives. In our experience, even in a climate with long winters it is
possible to maintain healthy colonies without the use of drugs provided
that good apiary hygene is practiced. This includes frequent wax
renewal and feeding devices for winter feeding where the bees can not
deposit any feces.
 
Regards, Ingemar  59 degrees N
 
 
**************************************************************************
Department of Entomology            E-mail: [log in to unmask]
Swedish Univ. Agric. Sci.           Tel:    Int+ 46 18 67 20 73
Box 7044                            Fax:    Int+ 46 18 67 28 90
S-750 07 Uppsala
Sweden
**************************************************************************
 
 
 
--
Regards
 
P-O Gustafsson, Sweden
[log in to unmask]    http://www.kuai.se/~beeman/