Sacbrood VirusThe Sacbrood Virus is a filterable virus with an unclassified RNA. The virus is active mainly in summer. The disease caused by it is not so common and the virus itself is less dangerous than other bee viruses. The virus attacks the bee brood and the contamination is done through feeding. The capped larvae receive infested food and thus they get contaminated and eventually die. The virus can live up to twenty-thirty days within a hive whether on combs or in honey.
The infested larvae present an important concentration of the virus within their fatty and muscular tissues. The adult individuals carry the viruses in their pharyngeal glands but show no evident sign of infection. However, their lifespan is dramatically diminished since they no longer gather pollen and eventually die. The disease manifests itself in the same season with the European Foulbrood and in many cases its outburst is determined by the same factors. The dead infected larvae, the adult bee and the infested beekeeping tools represent genuine sources of infestation. The Sacbrood Virus can be transmitted from one hive to another by rubbing and drifting honey bees or by the acquisition of already infested bee families.
SymptomsThe incubation period lasts for a week. The infested combs look very similar to those infested with foulbrood. The brood death takes place after being capped. The Sacbrood Virus infested cells have concave, perforated, dark colored caps. The infested larvae can be yellow, gray or brown; the head being darker than the rest of the body. Their tegument is opaque. They have a strange position within the comb cell: they are turned upside down with their ventral part totally exposed while the dorsal part leans against the inferior cell walls, having the aspect of a sack filled up with liquid. This liquid is neither viscous nor filante. It has no smell, the larvae do no adhere to the cell walls and they can be easily removed from the hive. Once dried, the Sacbrood Virus infested larvae look like a sort of black crust. When the cold season approaches the virus is less active and beginner beekeepers might believe that the virus has been defeated. This is far from being true, since it will return and kill more bees the next summer.
Treatment and PreventionThere is no available treatment for a hive infested with Sacbrood Virus. The proliferation of the virus can be stopped through abundant nectar gatherings, artificial feeding, sanitation measures and strengthening of weak bee families against Sacbrood Virus. It is advisable to melt the combs that contain infested brood.
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