This pathogen has been tentatively linked to
colony collapse disorder, a phenomenon reported primarily from the United States, since fall of 2006. Highly preliminary evidence of
N. ceranae was reported in a few hives in the Central Valley area of California. "Tests of genetic material taken from a "collapsed colony" in
Merced County point to a once-rare microbe that previously affected only Asian bees but might have evolved into a strain lethal to those in Europe and the United States." The researcher did not, however, believe this was conclusive evidence of a link to CCD; "We don't want to give anybody the impression that this thing has been solved." A
USDA bee scientist has similarly stated, "while the parasite nosema ceranae may be a factor, it cannot be the sole cause. The fungus has been seen before, sometimes in colonies that were healthy." Likewise, a Washington State beekeeper familiar with
N. ceranae in his own hives discounts it as being the cause of CCD. In early 2009, Higes
et al. reported an association between CCD and
N. ceranae was established free of confounding factors, and that weakened colonies treated with
fumagillin recovered. News articles published in October 2010 quoted researchers who had discovered that
Nosema fungus had joined with a previously unsuspected virus, invertebrate iridescent virus, or IIV6, dealing test bee colonies a lethal blow. Neither the fungus nor the virus alone kills all the test group, but the two combined do. Both the fungus and the virus are found with high frequency in hives that have suffered CCD. Final testing is in progress with field tests on colonies.
N. ceranae and
N. apis have similar lifecycles, but they differ in spore morphology. Spores of
N. ceranae seem to be slightly smaller under the light microscope and the number of polar filament coils is between 20 and 23, rather than the more than 30 often seen in
N. apis. The disease afflicts adult bees and depopulation occurs with consequent losses in honey production. One does not detect symptoms of diarrhea as in
N. apis. However, the infection damages the bee's midgut, resulting in the necrosis of intestinal tissue. This impairs the bee's ability to digest food and absorb nutrients. The most significant difference between the two types is how quickly
N. ceranae can cause a colony to die. Bees can die within 8 days after exposure to
N. ceranae, a finding not yet confirmed by other researchers. The forager caste seems the most affected, leaving the colony presumably to forage, but never returning. This results in a reduced colony consisting mostly of nurse bees with their queen, a state very similar to that seen in CCD. Little advice on treatment is available, but it has been suggested that the most effective control of
N. ceranae is the antibiotic
fumagillin as recommended for
N. apis. The
genome of
N. ceranae was sequenced in 2009. This should help scientists trace its
migration patterns, establish how it became dominant, and help measure the spread of infection by enabling diagnostic tests and treatments to be developed. ==Treatment==