Viruses are commonly present
in the honeybee colony. However infection of honeybees
and the appearance of disease symptoms seems to depend
to a large extent on other stress factors on the colony,
such as lack of space, food or water, weather pattern
or infection by other means be they bacterial, fungal
or mite.
Certain viruses can cause dramatic paralysis of adult
bees, (notably Acute Paralysis Virus [APV] and Chronic
Paralysis Virus [CPV]).
Obvious signs of paralysis include adult bees at or
near the hive entrance, dark and shiny in appearance
and unable
to fly. They are often seen crawling and trembling
on nearby foliage and can appear in huge numbers.
The wings
are usually dislocated and held spread out from the
body in an unnatural posture and the abdomen can
also be swollen.
Accurate diagnosis of viral diseases in honeybees is
often not straightforward and seemingly healthy colonies
can succumb alarmingly quickly when other trigger/stress
factors such as varroa mite infestation appear. This
may typically occur with APV or CPV in the middle of
a good summer season when the varroa mite levels are
at their highest.
Honeybee colonies can exhibit a plethora of symptoms
simultaneously, a phenomena collectively termed as
Parasitic Mite Syndrome or PMS. Varroa mite infestation
is always
associated with PMS, which is also characterised by
diseased bee brood, infected with one or several
types of virus.
PMS in bee brood may at first glance be confused with
European foulbrood with the larvae dying stretched
or curled in their cells. When pressed with a matchstick
the cadaver is globular, as in EFB. Yet laboratory
analysis
show these symptoms to be to virus rather than foulbrood
bacteria.
There are many viral agents of disease in honeybees,
too many to cover comprehensively in this section.
Some of the more common viruses affecting honeybee
health
include sacbrood virus, Deformed Wing Virus (DWV),
Cloudy Wing Virus and Kashmir Bee Virus.
| Control Of
Viral Diseases |
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At present there are no available treatments for viral
diseases in honeybees. However, good husbandry and timely
treatment of other pest and disease organisms can help
to prevent any overt effects of viruses within the hive.
It has been shown that viruses + varroa can often be
a deadly combination in a beehive. However, if the varroa
infestation is controlled adequately, there are far fewer
incidences of viral diseases of the honeybees.
Bee colonies sometimes die if there is a dearth of foodsource
or if the brood is exposed for too long a period to low
temperature. Manipulation of hives in cold weather should
be minimised to avoid chilling the bee brood, especially
uncapped brood. If the colonies themselves cannot keep
the brood warm enough then the uncapped brood, which
are the most vulnerable stage perishes.
The small hive beetle, Athina
tumida, is a native of South Africa and although a pest
of honeybee colonies is not especially problematic in
South Africa.
This beetle and its larva however causes vast damage
to honeybee colonies in the United States where it
was discovered in 1998.
The small hive beetle larvae live in and feed on hive
debris, wax comb and pollen and there are also reports
that the beetle larvae and adults will eat bee brood
and eggs.
The destruction and contamination caused to honey
and wax by this prolific pest in the United States
is a
major concern especially for commercial bee farmers
there.
Exotic species, once accidentally introduced to
a new environment tend to become pests relatively
quickly
if not checked.
The range of the small hive
beetle is increasing in the USA and infestations of this
pest have been discovered
in Egypt and Australia. However,
the impact
of the beetle on beekeeping in these areas appears
to be less serious than in the USA.
