A good deal of my bees died during winter 2009-2010. They did survive this
winter (smaller colonies), except in one yard, where again 50% died. As I
could diagnose, by the *behaviour during summer*, it was caused by Nosema
Ceranae. I changed my Varroa treatments, that was the only change in
management. Treatments were done at the same time of the year (end of july).
Since then I am very interested in publications which may lead to a better
understanding. Sceptical remarks from people that were lucky enough and
obvious did not suffer from Nosema c. so far, are of rather (un)academic
nature and are noncommittal to me.
For the moment I am visiting Niguaraca. I understood that also the Afrobees
have Nosema c., but it seems that this does not affect the bees,
Geert Van Eizenga
My latest finding about Nosema ceranae are the following:
ACCORDING BY THE WORLD ANIMAL HEALTH ORGANIZATION VARROA AND NOSEMA CERANAE
ARE THE MAJOR PROBLEMS OF EUROPEAN BEES (January 2011)
The ad hoc group in charge of OIE diseases of honey bees has proposed to
revise the global distribution and Nosema health status, in light of the
spread of Nosema ceranae. The group also proposed that pending the outcome
of the review and view the relative risk associated with N. ceranae
correction of the chapter on this and be reinserted in the Code. The group
also discussed the health situation of the hives in the world. Looking to
Europe, the group noted that the problem of beekeepers years is the varroa
mite. The treatment is often applied too late or incorrectly, resulting in
mortality of the entire colony of bees, mainly in autumn and winter. In
spring, however, the most common cause of loss of colonies is Nosema. Nosema
apis has been replaced almost entirely by Nosema ceranae, imported from
Asia.
Breeding disease resistant honeybees - Fries and Lindström, 2010
He (Fries) states, p.7 A range of different pathogens are described from
adult honeybees. However, none *except* the nosema parasites appear to have
the capacity to strongly impact colony vitality.
p.8 Reports from Spain suggest that N. ceranae is much more virulent than
N. apis, killing infected colonies within a year if not controlled. However,
it appears that this level of virulence
may not appear in many other areas.
Quotations from: Manual Breeding disease resistant honeybees, which is part
of the Specific Targeted Research Project BEE SHOP (Contract no. PL 022568)
financed by the European Commission 6th Framework Programme.
Ingemar Fries in California.
Dr. Ingemar Fries, of Sweden, gave an overview of what we know and don’t
know about Nosema ceranae at the January Mega-Meeting in Galveston, TX.
California. Where he stated: Caged bee experiments show little difference in
virulence. With inoculations containing mixed spores, N. ceranae produces
spores in about four days, while N. apis takes about six. Maximum numbers of
spores are pretty similar. …… In the bees, N. ceranae could develop over a
wider temperature range than could N. apis. There are still questions about
strain differences and whether or not pesticides and virus pressures will
impact nosema development, he said.
Interesting (in California) were the findings of Brenna Traver, Virginia
Polytechnic Institute. She found: Using PCR (analyzes for nosema DNA), they
found peak levels of infections in workers and drones from March through
June. Levels were highest in hive drones in June, but highest in flying
drones in July. In a small number of instances, PCR suggested that pupae can
become infected before emerging from their cells. Grace Mulholland, also
from Virginia Tech, examined bees for nosema infections using spore counts
and PCR. She found that spore counts miss about 50 percent of low-level
infections. In three different 100 individual bee samples, she found 82, 18,
and 44 percent of the bees infected by PCR. By spore count, those same bees
were 60, 8, and 4 percent infected, respectively. Can this be a reason why
we tend not to get nosema treatments applied in a timely fashion, using
spore count criteria? Could this be the reason that colonies in Spain
collapse completely by the time that spores can be found in the brood nest
workers?
--
Green Bee Consultancy
Drs.Geert Van Eizenga
Marnelaan 41
9727 DS Groningen/Holland
Tel.+31 505278909
Mob. +31616424299
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