Opinion has varied on the
validity of N. bombi as a species separate from N.
apis. Some authors have reported experimental
cross-infection of bumble bees with N. apis
(Fantham & Porter 1913; Showers et al. 1967 ) and
honey bees with N. bombi (Kudo 1924), but
Uspenskii (1949) and Eijnde & Vette (1993) have
provided evidence that bumble bees are not susceptible
to infection by N. apis. Weiser (1961) argued
that the morphological differences between the two
Nosema species were not sufficient to warrant claiming
N. bombi as a separate species, and suggested that
the two were synonymous. This view was subsequently
supported by Showers et al. (1967) and
MacFarlane (1974), and was adopted in the most
recent list of microsporidian species (Sprague 1977).

The epidemiology of N. bombi in bumble bees
also differs from that of N. apis in honey bees. In
the honey bees, infection of the queen is rare and
ultimately results in her death or supersedure
(Shimanuki et al. 1973) and the decline of the colony.

In bumble bees, the queen is the primary source of
N. bombi infection for the next generation, and infection
has seemingly little impact on her nest initiation
and egg laying (Fisher & Pomeroy 1989b).

N. bombi, with its low virulence and generation-to
generation transmission, seems well adapted to its
bumble bee host, which has an annual life cycle
(Alford 1978). Honey bee colonies, however, are
continually productive in most climates, and their
parasite, N. apis, tends to be endemic and cyclic in
its virulence (Bailey 1981).

-- 
Nosema bombi, a microsporidian pathogen of the bumble bee
CATHERINE A. McIVOR & LOUISE A. MALONE*
New Zealand Journal of Zoology, 1995, Vol. 22: 25-31

* * *

Bombus terrestris
was first used as a managed commercial
pollinator about a decade ago. The industry is now
flourishing worldwide. The natural area of distribution of
B. terrestris covers all of continental Europe, the south of
England, and the south of Scandinavia.

The main exporting countries worldwide
are the Netherlands, Belgium, and Israel; the main
importing countries are Mexico, Japan, China, Korea, Jordan,
Spain, and Italy.

In Japan, this species has been used for pollination of
tomato plants in glasshouses since 1991 (Ono 1998). More
than 40 000 colonies of B. terrestris are imported into Japan
from Europe each year.

The most serious impact is in carrying parasite
invaders. As an example, the varroa mite, Varroa jacobsoni,
which is a virulent parasite of the European honeybee,
Apis mellifera, is native to eastern Asia, where it parasitizes the
eastern honeybee, A. cerana. The mites
were introduced into the Western Hemisphere from Japan
through the transportation of European honeybee colonies.
The mite is now responsible for enormous losses of European
bee colonies worldwide.

Recently, we found an endoparasitic mite,
Locustacarus buchneri, in introduced colonies of
B. terrestris in Japan. However, we have so little information
about this mite that we cannot predict its impact on
Japanese native bumblebees.

Bumblebee commercialization will cause worldwide migration of parasitic mites
KOICHI GOKA, KIMIKO OKABE, MASAHIRO YONEDA and SATOMI NIWA

Molecular Ecology (2001) 10, 2095–2099
(c) 2001 Blackwell Science Ltd
Blackwell Science, Ltd

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