As elsewhere around the world, when Varroa mites reached England, so
did many cases of colony collapse that could not be explained simply
by nutrient drain by parasitic mites. In fact, the article, Varroa and
Viruses in the U.K. "Bee Biz, No. 7, February 1998), states that under
hygienic conditions, mite feeding only temporarily reduces the protein
level of the host bee, with no further consequences to the bee. Thus,
the mortality associated with mite feeding appears to be pretty much a
mite vectored, viral disease problem.
However, as in most biological cases, the story is not simply black
and white. Some colonies with high virus levels survive while others
don't. This suggests that selection and breeding programs could have
real value in this battle to protect bees from mites. But, how do you
determine which stock or stocks have the complex of desired traits?
Usually when you select for one or two traits, you lose or modify
others for the worse. Bees don't go along with being manipulated
genetically very well at all.
FROM
Eric Mussen
Apiculture Newsletter
January/February 1998
* * *
The exoskeleton and its cuticular surface are a pretty formidable
barrier against microbes. The outer layer of the exoskeleton is
covered with a waxy layer that includes unsaturated fatty acids.
Besides preventing loss of water (prevents dehydration) and
penetration of water (prevents tissues from becoming "water logged"),
the waxy layer makes it difficult for microbes to become attached to
the surface. It also resists enzymes (chitinases) secreted by microbes
that might other-wise be able to eat their way into the insect. While
we think of the exoskeleton as protecting the outside of the bee, it
extends well into the tracheal system and lines the fore gut and hind
gut of the intestinal tract. It has to be sloughed each time the bee
molts.
Despite that protection, microbes do make their way into honey bees.
In the case of fungi, a number have been listed as being pathogenic.
Some are regarded as named "bee diseases" like Ascosphaera apis
(chalkbrood); Aspergillus flavus, A. fumigatus, and other Aspergillus
species (stonebrood); and Nosema apis and N. ceranae (nosema disease).
Other fungi have been recorded as agents of "opportunistic"
infections. They include Aureobasidium pullulans, Trichoderma
lignorum, Mucor hiemalis, Rhizopus species (black bread mold), and
various species of Candida, a yeast.
It now seems that Dr. Bailey was very prescient in the 1960's. Lots of
honey bees have latent viruses in them. If they don't replicate, the
viruses don't appear to cause any physical damage to the bee. But,
they are showing up in honey bee eggs, larvae, pupae and adults. The
research uncovered one more interesting fact. The WHOLE GENOME of the
virus could become incorporated into the bee's genome. Then, under the
right circumstances, the instructions for virus replication could be
activated right from within the bee cell, itself.
FROM
Eric Mussen
Apiculture Newsletter
July/August 2007
* * *
Sacbrood virus is the most widely distributed of all honey bee
viruses. Since its first identification in the United States in 1913,
infection of SBV has been found on every continent where A. mellifera
honey bees are present. SBV attacks both brood and adult stages of
bees, but larvae about 2-day old are most susceptible to SBV
infections. SBV affects adult bees without causing obvious signs of
disease, but the infected adult bees may have a *decreased life span*.
SBV infection has been associated with varroa mite infestation. SBV
was detected in large amount of adult bees from varroa mite–infested
colonies. Stressful circumstances can favor outbreaks of viral
diseases, thus any efforts that strengthen the colony health are
expected to reduce the risk of virus infections. Since the varroa mite
has been proven to be an effective vector in transmitting and
activating viruses, timely and efficient control of the varroa mite
population will reduce the incidence of viral diseases.
* Viruses can act in new and unexpected ways and new viruses keep
emerging, forming additional challenges in the elucidation of viral
infections.
FROM
Honey Bee Viruses
Yan Ping (Judy) Chen, and Reinhold Siede
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