NOSEMOSIS OF BEES

SUMMARY

To date, two microsporidian parasites have been described from honey
bees: Nosema apis (Zander) and Nosema ceranae (Fries). Nosema apis is
a parasite of the European honey bee (Apis mellifera) and Nosema
ceranae of the Asian honey bee (Apis cerana) and the European honey
bees). The latter has recently been detected in several geographically
separated populations of European honey bees in Europe, South and
North America and Asia.  The pathological consequences of Nosema
ceranae in Apis mellifera are not well known. In the following
chapter, only Nosema apis is described. Both types are presumably very
similar.

The microsporidium Nosema apis (Zander) is a parasite of the adult
honey bee that invades the epithelial cells of the ventriculus.
Infections are acquired by the uptake of spores during feeding or
grooming. The disease is transmitted among bees via the ingestion of
*contaminated comb* material and water, and by trophallaxis; honey
stores and crushed infected bees may also play a role in disease
transmission. Spores are expelled with the faeces where they may
retain their viability for more than 1 year. Spores may also remain
infective after immersion in honey and in the cadavers of infected
bees; however they may lose viability after 3 days when submerged in
honey at hive temperature. The relative importance of faeces, honey
and cadavers as reservoirs of infective spores is not fully
understood.

It is likely that faecal contamination of wax, *especially in combs*
used for brood rearing, or other hive interior surfaces, provides
sufficient inoculum for N. apis to be successfully transmitted to the
next generation of bees. The relative importance of faeces, honey and
cadavers as reservoirs of infective spores is not fully understood and
it seems that temperature may have a marked effect on the rates at
which spores lose viability, regardless of their medium (14) The
spores are inactivated by acetic acid or by heating to 60°C for 15
minutes. To be effective, these treatments, which inactivate spores on
hive surfaces, need to be combined with feeding colonies with the
antibiotic fumagillin to suppress infections in live bees.

Identification of the agent: In some acute cases, brown faecal marks
are seen on the comb, with sick or dead bees in the vicinity of the
hive. The majority of Nosema-infected colonies will appear normal,
with *no obvious signs of disease* even when the disease is sufficient
to cause significant losses in honey production and pollination
efficiency. Autoinfections can occur at the same time as new
infections. After a short interval, spores develop in large
quantities. Infected bees are unable to fly and have been shown to be
infected with up to 500 million spores.

NOSEMOSIS OF BEES
http://www.oie.int/eng/normes/en_mmanual.htm
http://www.oie.int/eng/normes/mmanual/2008/pdf/2.02.04_NOSEMOSIS.pdf

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