Chronic bee paralysis virus (CBPV) commonly affects adult ''Apis mellifera'' honey bees and causes a chronic paralysis that can easily spread to other members of a colony. Bees infected with CBPV begin to show symptoms after 5 days and die a few days after. Chronic bee paralysis virus infection is a factor that can contribute to or cause the sudden collapse of honeybee colonies. Since honeybees serve a vital role in

ecological resilience In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorm ...

, it is important to understand factors and diseases that threaten them. Although CBPV infects mainly adult bees, the virus can also infect bees in earlier developmental stages, though developing bees typically have significantly lower viral loads compared to their adult counterparts. Death as a result of CBPV infection in developing bees or brood losses due to viral infection are low or nonexistent. Bees that have been infected with CBPV may harbor millions of viral particles, with half of them concentrated in the head region of the infected honey bee. As a result, the virus has neurotropic activity, allowing the virus to cause nervous system damage in infected honey bees. Specifically, research has identified that viral particles concentrate primarily in two centers of the brain to replicate after infecting the host. The first replication center is the

mushroom bodies The mushroom bodies or ''corpora pedunculata'' are a pair of structures in the brain of insects, other arthropods, and some annelids (notably the ragworm ''Platynereis dumerilii''). They are known to play a role in olfactory learning and memory ...

, which play a role in sensory processing, memory, learning, and motor control, and the second replication center the central body, the center of the

insect brain The supraesophageal ganglion (also "supraoesophageal ganglion", "arthropod brain" or "microbrain") is the first part of the arthropod, especially insect, central nervous system. It receives and processes information from the first, second, and th ...

that primarily control locomotion, behavior, bodily orientation, and arousal.

Virology

Chronic bee paralysis virus shares similarities to the virus families '' Nodaviridae'' and ''

Tombusviridae ''Tombusviridae'' is a family of single-stranded positive sense RNA plant viruses. There are three subfamilies, 17 genera, and 95 species in this family. The name is derived from '' Tomato bushy stunt virus'' (TBSV). Genome All viruses in the ...

'', but CBPV is distinct enough from the two existing families and consequently is considered a new family of viruses. As a result, CBPV has yet to be fully classified.Aurore Chevin, Bruno Coutard, Philippe Blanchard, Anne-Sophie Dabert-Gay, Magali Ribière-Chabert, Richard Thiéry
Characterisation of Structural Proteins from Chronic Bee Paralysis Virus (CBPV) Using Mass Spectrometry
in: Viruses. 2015 Jun; 7(6): 3329–3344. doi:10.3390/v7062774, , Chronic bee paralysis virus is a single-stranded positive-RNA virus with five fragments, two large fragments and three small fragments. The first large fragment is suspected to encode an RNA-dependent RNA polymerase, as it possesses 8 conserved domains of an RNA-dependent RNA polymerase. The second large fragment is thought to encode for the virus

capsid protein A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...

, which is reported to be a capsid protein of 23.5 kDa and four polypeptides of 75, 50, 30 and 20 kDa. The virus capsid is hypothesized to have

icosahedral symmetry In mathematics, and especially in geometry, an object has icosahedral symmetry if it has the same symmetries as a regular icosahedron. Examples of other polyhedra with icosahedral symmetry include the regular dodecahedron (the dual polyhedr ...

. Chronic bee paralysis virus is also found to facilitate the growth and reproduction of a satellite virus, called Chronic bee paralysis associate satellite virus (CBVA), which has three small (+) single-stranded RNA fragments. The three small (+) single-stranded RNA fragments appear inconsistently in the Chronic bee paralysis virus, which lends to the idea that the three RNAs are not components of CBPV but of a satellite virus that relies on CBPV activity in order to proliferate. Additionally, the three small RNA fragments each have molecular weights of 0.35 x 10⁶ (1100 nucleotides), which exactly matches the molecular weights of the three (+) ssRNA fragments of CBVA.

Infection and transmission

Chronic bee paralysis virus is transmitted through two main mechanisms. The first mechanism is viral transmission through bee feces, which remains on the hive floor and can be picked up on the furry legs of other bees and ingested orally. The second mechanism is through close contact between bees in the hive.

Worker bee A worker bee is any female (eusocial) bee that lacks the full reproductive capacity of the colony's queen bee; under most circumstances, this is correlated to an increase in certain non-reproductive activities relative to a queen. While worker be ...

s are the most susceptible to infection, since they travel the hive most frequently. The infection may spread between hives as a result of indirect contact or direct contact between honey bees.

Research Research is " creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness ...

shows that mainly adult honey bees can be infected with chronic bee paralysis virus by a topical contact with infected feces or by ingestion of

virion A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...

-containing substances.

Viral replication cycle

Entry into cell

Chronic bee paralysis virus is transmitted to honey bees through a

ubiquitous Omnipresence or ubiquity is the property of being present anywhere and everywhere. The term omnipresence is most often used in a religious context as an attribute of a deity or supreme being, while the term ubiquity is generally used to describ ...

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

common to honey bee hives, Varroa mites (''

Varroa destructor ''Varroa destructor'', the ''Varroa'' mite is an external parasitic mite that attacks and feeds on the honey bees '' Apis cerana'' and ''Apis mellifera''. The disease caused by the mites is called varroosis. The ''Varroa'' mite can reproduce o ...

''). Varroa mites are known to harbor many viruses for which honey bees are susceptible and permissive. The parasitic mites attach themselves to honey bees externally and feed off of the

hemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...

of their hosts. This exchange of fluids between the parasitic mites and the hosts allows for CBPV particles to enter fluid transfer systems in the honey bee body. The mechanisms by which chronic bee paralysis virus gains entry into honey bee cells is currently unknown.

Replication

Like other positive sense single-stranded RNA viruses, Chronic bee paralysis virus replicates in the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

of honeybee cells. The first large (+) RNA fragment in the CBPV

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...

likely encodes for an RNA-dependent RNA polymerase, which makes many copies of viral RNA. After many copies of the genome have been produced, the honey bee host's cellular processes will translate the viral RNA into functional

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s which can cause propagation of the virus inside the host. The virus replicates at the highest levels in the head of the honeybee, reaching an average of 10⁷ copies of the virus in an infected worker bee head and as many as 10¹¹ copies of the virus in an infected

queen bee A queen bee is typically an adult, mated female ( gyne) that lives in a colony or hive of honey bees. With fully developed reproductive organs, the queen is usually the mother of most, if not all, of the bees in the beehive. Queens are developed ...

head. Chronic bee paralysis virus particles have been found to concentrate in two centers; in

which play a role in sensory processing,

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered ...

, and learning as well as in the central body, which plays a vital role in coordinating movement. Loss of flying ability in honey bees as a result of CBPV infection can be attributed to neuron destruction in the central body. Erratic behavior in infected bees may be a result of mushroom body neuron destruction.

Symptoms

Infected honeybees will begin to show symptoms of the illness within five days of infection, and the infection presents in two distinct ways, with Type I infection being the more common of the two infection types. A Type I infected bee presents with a bloated abdomen due to a fluid-filled honey sac and weak or trembling wings. Type I infected honey bees tend to crawl on the ground or cluster near the entrance of the hive, as their weakened wings lead to an inability to fly. A Type II infected honey bee presents with complete abdominal hair loss, causing it to appear black and greasy. These bees are still able to fly 2–3 days after symptoms begin to appear, but they lose their ability to fly shortly before succumbing to the disease. A third type of infection that is a major contributor to the spread of the virus is an infection of CBPV in which the infected bee exhibits no symptoms of the illness. The infected bee does not present with any of the classic symptoms of the disease before death, and, as a result, is able to transmit the virus beyond its own hive.

Treatment

There is no known treatment for the disease currently.

Testing

Chronic bee paralysis virus is classified as an inapparent infection because there are few tell-tale symptoms that appear before the infection has progressed to a fatal degree. As many honey bees can become infected and either show symptoms days after the initial point of infection or fail to show any symptoms throughout the entire course of the illness, CBPV can infect entire hives before the virus is detected. Despite the use of

infectivity In epidemiology, infectivity is the ability of a pathogen to establish an infection. More specifically, infectivity is a pathogen's capacity for horizontal transmission — that is, how frequently it spreads among hosts that are not in a parent ...

and serological tests, these testing methods are often inaccurate and difficult to reproduce with consistent results.

Symbiotic relationships

Although Chronic bee paralysis virus mainly infects honey bees, the virus has also been found to replicate in two species of carnivorous

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

, ''

Camponotus vagus ''Camponotus vagus'' is a species of large, black, Palaearctic carpenter ant with a wide range that includes much of Europe, a large area of Asia, and part of Africa. Description ''Camponotus vagus'' is a relatively distinctive species that is ...

'' and ''

Formica rufa ''Formica rufa'', also known as the red wood ant, southern wood ant, or horse ant, is a boreal member of the ''Formica rufa'' group of ants, and is the type species for that group, being described already by Linneaus in the first version of Sys ...

''. These carnivorous ants become infected with CBPV through two mechanisms: eating decomposing bees who harbor the virus or by independently collecting infected honeydew. While the virus does not cause any symptoms in the carnivorous ants, the

commensal relationship Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fr ...

between the virus and the ants allows the ants to serve as a reservoir for viral replication to occur. Chronic bee paralysis virus is also similar to slow bee paralysis virus and

acute bee paralysis virus Diseases of the honey bee or abnormal hive conditions include: Pests and parasites ''Varroa'' mites ''Varroa destructor'' and ''V. jacobsoni'' are parasitic mites that feed on the fat bodies of adult, pupal and larval bees. When the hive ...

. Though CBPV does not fall into the same family as the other two viruses, it bears similarities to the other viruses because it causes paralysis as the fatal symptom of the infection. Slow bee paralysis, in contrast to Chronic bee paralysis virus, causes paralysis of the front two pairs of legs on honey bees ( ''Apis mellifera''), silkworms (''

Bombyx mori The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...

''), and bumble bees ( ''Bombis'' spp.). This paralysis eventually causes death in the infected insects. Slow bee paralysis virus is transmitted to hives through ''

'' mite infestations. Because of the similarities between the two viruses, Chronic bee paralysis virus is suspected to have the same mode of transmission. Chronic bee paralysis virus is also seen to interact with satellite viruses. The three short RNA segments of the viral genome are thought to be a satellite virus. Only in the presence of CBPV can the associated satellite virus proliferate.

References

{{Taxonbar, from=Q16662559 Bee diseases Insect viral diseases Positive-sense single-stranded RNA viruses