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A new paper just out on PLOS breaks down IAPV and discusses its connection with colony collapse. While there seems to be a direct connection between weak colonies and high levels of IAPV, this does not mean that IAPV is the cause of that weakness. In fact, it could be the other way round: that weak colonies may be more susceptible to disease. There may be other reasons why the colonies are weak in the first place and are unable to fight off the virus.

Israeli acute paralysis virus (IAPV) is a widespread RNA virus of honey bees that has been linked with colony losses. Here we describe the transmission, prevalence, and genetic traits of this virus, along with host transcriptional responses to infections.

While no statistically significant seasonal variation in IAPV infection was observed in the strong colonies, the infection rate of IAPV in adult bees in weak colonies increased from spring to summer and fall and peaked in winter. While strong colonies in our survey survived through the cold winter months, almost all weak colonies collapsed before February (Figure 3).

While the simultaneous presence of multiple viruses in honey bees makes Koch’s postulates of disease causality difficult to fulfill [27], the presence and diversity of viruses in bee colonies has high predictive value for colony mortality [28]. The negative correlation between the level of IAPV infections and the size of host populations, in combination with other stress factors, has significant negative impact on colony survival and is likely a contributing factor to poor winter survivorship of honey bee colonies.
IAPV was found to be the third most common virus infection
in bee colonies after DWV and Black Queen Cell Virus
(BQCV). Over the 4-year study period, the infection IAPV
detected in the brood was significantly higher than in adult bees (p,0.001).
When we divided our experimental bee colonies into
those with more than ten frames covered with adult workers and
more than six frames filled with brood and food stores (‘strong’)
versus those with fewer than ten frames of adult bees, less than
six combs with brood and small patches of food stores (‘weak’),
we found a measurable difference in IAPV infection levels. The
average rate of IAPV infection per month was 49% for brood
and 19.5% for adults in weak colonies and 26% for brood and
3.25% for adults in strong colonies. The overall rate of IAPV
infection in weak colonies was significantly higher than in the
strong colonies (p,0.01 for brood and p,0.001 for adults).
Citation: Chen YP, Pettis JS, Corona M, Chen WP, Li CJ, et al. (2014) Israeli Acute Paralysis Virus: Epidemiology, Pathogenesis and Implications for Honey Bee Health. PLoS Pathog 10(7): e1004261. doi:10.1371/journal.ppat.1004261
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