Dynamics of the presence of israeli acute paralysis virus in honey bee colonies with colony collapse disorder.

Chunsheng Hou,Hadassah Rivkin,Yossi Slabezki,Nor Chejanovsky

doi:10.3390/v6052012

Abstract

The determinants of Colony Collapse Disorder (CCD), a particular case of collapse of honey bee colonies, are still unresolved. Viruses including the Israeli acute paralysis virus (IAPV) were associated with CCD. We found an apiary with colonies showing typical CCD characteristics that bore high loads of IAPV, recovered some colonies from collapse and tested the hypothesis if IAPV was actively replicating in them and infectious to healthy bees. We found that IAPV was the dominant pathogen and it replicated actively in the colonies: viral titers decreased from April to September and increased from September to December. IAPV extracted from infected bees was highly infectious to healthy pupae: they showed several-fold amplification of the viral genome and synthesis of the virion protein VP3. The health of recovered colonies was seriously compromised. Interestingly, a rise of IAPV genomic copies in two colonies coincided with their subsequent collapse. Our results do not imply IAPV as the cause of CCD but indicate that once acquired and induced to replication it acts as an infectious factor that affects the health of the colonies and may determine their survival. This is the first follow up outside the US of CCD-colonies bearing IAPV under natural conditions.

Highlights

Honey bees (Apis mellifera) play a vital role in agriculture by pollinating on a wide variety of crops and flowers
Qualitative RT-PCR analysis of samples from these colonies indicated the presence of several honey bee viruses, mainly Israeli acute paralysis virus (IAPV) and Deformed wing virus (DWV) (Table 1)
To estimate the IAPV titers in the colonies we performed quantitative determinations of its genomic copies using RT-qPCR. This test showed that IAPV was the prominent virus in Colony Collapse Disorder (CCD)-colonies sampled in March 2011 with genomic copy titers varying from 1010–1012/μg RNA in colonies 1–15

Summary

Introduction

Honey bees (Apis mellifera) play a vital role in agriculture by pollinating on a wide variety of crops and flowers. In the last years there is increasing awareness that honey bee colonies worldwide are suffering a serious decline [2,3] This decline was attributed to several factors including pesticides, pathogens and parasites such as Nosema ceranae/ Nosema apis, Crithidia mellificae, Varroa destructor, bacteria, as well as viruses [2,4,5,6,7,8,9,10,11]. Several studies indicated that stress factors affecting bee immunity may be triggering dormant viral infections remaining hidden within bees or bee colonies, to become overt infections [17,18] These factors could be human-born such as insecticides [19] or nature-born such as environmental-climatic stresses or co-infection and infestation with other pathogens [17,20]

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