2.1. Introduction

Bee diseases caused by viruses are significant threats to apiculture. Pathogen surveillance is an essential component of a structured (inter)national management strategy to contain or prevent epidemics of viral diseases in honey bee populations. Such surveillance is done both through questionnaires of beekeepers (see the BEEBOOK paper on surveys; van der Zee et al., 2013) and through monitoring bee colonies for pathogen prevalence and amount.

Although some honey bee viruses, such as chronic bee paralysis virus (CBPV), deformed wing virus (DWV), black queen cell virus (BQCV), sacbrood bee virus (SBV) and cloudy wing virus (CWV), are capable of causing diseases  with recognizable symptoms, most honey bee viruses usually persist and spread between colonies as covert infections without apparent symptoms in bees. Many other bee viruses such as bee virus X and bee virus Y (BVX; BVY) or filamentous virus (AmFV), either do not cause outward symptoms at all, or others, such as slow bee paralysis virus (SBPV) and acute bee paralysis virus (ABPV) only do so under laboratory conditions or produce vague, non-descript symptoms, such as ‘early death’ by Kashmir bee virus (KBV) and Israeli acute paralysis virus (IAPV) or ‘clustering’ associated with Apis iridescent virus (AIV). Many bee virus infections cannot therefore be identified through field observations, because the symptoms are non-existent, inconsistent or absent due to low titres. Until field-ready pathogen ID-kits become available, pathological analysis requires the transport of samples to a laboratory for analysis.