Chronic bee paralysis virus

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"Chronic bee paralysis virus"
Systematics
Classification : Viruses
Area : Riboviria
Empire : Orthornavirae
Phylum : Kitrinoviricota
Class : unclassified
Order : unclassified
Family : unclassified
Genre : unclassified
Type : "Chronic bee paralysis virus"
Taxonomic characteristics
Genome : (+) ss RNA, segmented
Baltimore : Group 4
Symmetry : icosahedral
Cover : no
Scientific name
"Chronic bee paralysis virus"
Short name
CBPV
Left
NCBI  Taxonomy: 180822

The species " Chronic bee paralysis virus " ( " Chronic bee paralysis virus " CBPV ), not to be confused with the Slow bee paralysis virus (SBPV) or Acute bee paralysis virus (acute bee paralysis virus ABPV), is a cause of bee diseases and often affects adult honeybees of the species Apis mellifera ( Western honeybees ) and causes chronic paralysis that easily spreads to other members of a colony. Bees infected with CBPV show symptoms after five days and die a few days later. CBPV infection can contribute to or cause the sudden breakdown of honey bee colonies. Because honey bees are an important factor in the resilience of an ecosystem , it is important to understand the circumstances and diseases that threaten them.

Although CBPV mainly adults infected (adult) bees, the virus can also infect bees in earlier stages of development. However, growing bees typically have a significantly lower viral load compared to their adult conspecifics. Mortality from CBPV infection in developing bees is low or nonexistent; the same applies to the brood losses due to such a virus infection.

Bees infected with CBPV can contain millions of virus particles (virions), half of which are concentrated in the head area of ​​the infected honeybees. As a result, the virus exhibits neurotropic activity, i. H. the virus can cause nervous system damage in infected honey bees .

construction

The Chronic bee paralysis virus is a single-stranded RNA virus of positive polarity with five segments (two large and three small). The first large segment is believed to encode an RNA-dependent RNA polymerase , as it has 8 conserved domains from this family of enzymes. The second large fragment appears to code for the virus capsid proteins. Apparently there is an icosahedral symmetry.

The closest relatives of

Satellite virus

It was also found that CBPV facilitates the growth and reproduction of a satellite virus known as Chronic Bee Paralysis Associate Satellite Virus ( CBVA ), which has three small, single-stranded RNA segments of positive polarity, also (+) ssRNA.

In the CBPV genome, the three small RNA segments do not seem to match the two large ones. There is much to suggest that these three (+) ssRNAs are not part of CBPV, but rather a satellite virus that depends on CBPV activity to reproduce. In addition, the three small RNA segments each have molecular weights of 0.35 × 10 6 (1100  nt ), which corresponds exactly to the molecular weights of the three (+) ssRNA segments from CBVA.

Infection and transmission

CBPV is transmitted through two main mechanisms.

  • The first mechanism is the transmission of virus through bee droppings, when it remains on the beehive floor and clinging to other bees' furry legs and can then be ingested orally.
  • The second mechanism is via the close contact between the bees in the hive. Worker bees are the most susceptible to infection because they are the most common in the hive. The infection can spread through indirect or direct contact between honeybees from different hives . Studies show that mainly adult honey bees can be infected with CBPV through contact with infected faeces or through ingestion of substances containing viruses.

CBPV is also transmitted to honey bees by an ubiquitous parasite in beehives, the Varroa mites Varroa jacobsoni . Varroa mites are known to harbor a variety of viruses to which honeybees are susceptible or tolerant. The parasitic mites attach themselves externally to honey bees and feed on the hemolymph of their hosts. This exchange of fluid between the parasitic mites and the hosts allows CBPV particles to enter fluid transfer systems in the honeybees' body.

Propagation cycle

Entry into the cell

The mechanisms by which CBPV virions enter honeybee cells are currently unknown.

Replication

Like (+) ssRNA viruses, CBPV replicates in the cytoplasm of the host cells. The first large (+) RNA segment in the CBPV genome likely codes for an RNA-dependent RNA polymerase that makes many copies of the viral RNA genome. After many copies of the genome have been made, the cellular processes of the host cells convert the viral RNA into functional proteins ( translation on the ribosomes ), which enable the virus to multiply in the host. The virus replicates most strongly in the honeybee's head. Rates of an average of 10 7 copies of the virus in the head of an infected worker and up to 10 11 copies in that of an infected queen bee are achieved.

It could be shown that after infection of the host the virions concentrate mainly in two centers of the bee brain and replicate there. Both are located in the part of the upper pharyngeal ganglion called the protocerebrum : The first of these replication centers is the fungal body , which plays a role in sensory processing, memory, learning and motor control (coordination of movement). The second replication center is the central body, the center of the insect brain, which mainly controls body orientation, locomotion, behavior and arousal. The loss of flight ability in honey bees as a result of CBPV infection can be traced back to the destruction of neurons in the central body. Irregular behavior in infected bees, on the other hand, can be attributed to the destruction of neurons in the fungal body.

Disease symptoms

The bee on the right shows the beginning of blackening in connection with black disease.

Infected honey bees show symptoms within five days of infection. The infection occurs in two different ways, with Type I infection being the most common of the two types of infection:

  • In the case of a type I infection, the infected bee shows a distended abdomen (belly) due to a honey sack filled with fluid, and weak or trembling wings. Honeybees infected with Type I tend to crawl or cluster on the ground near the beehive entrance as their weakened wings make them unable to fly.
  • With a type II infection, the honeybee shows complete hair loss in the abdominal area (stomach area), which makes it appear black and greasy. For this reason, the French name for the disease is maladie noire , black sickness . Bees infected in this way can still fly 2–3 days after the symptoms appear, but ultimately lose their ability to fly shortly before they succumb to the disease.

A third type of infection that makes a significant contribution to the spread of the virus is an infection with CBPV in such a way that the infected bee does not show any classic disease symptoms until it dies. She can therefore transmit the virus beyond her own beehive during this time.

Combat

There is currently no known therapy for the disease. Often, infections with CBPV will subside on their own, but if infected bees are detected, they must be removed from the hive immediately to reduce the likelihood of the virus spreading. Adding healthy bees from another colony to a smaller hive that has been badly affected by the virus can prevent the colony from collapsing in infected hives. For unknown reasons, the risk of infection is higher in winter than in the warmer months.

Treating the beehive for varroa mites has also been shown to be an effective preventative method against viral infections. However, bees should not be treated preventively against mites, because the mites quickly develop resistance. However, once discovered, mites can be eliminated through the use of pesticides . Common agents are fluvalinate (Apistan), formic acid , and thymol (Apiguard). The home remedies for eradicating mites in a beehive also include dusting the beehive floors and the honeybees themselves with powdered sugar to suffocate the mites.

Testing

Infections with CBPV are considered inapparent or subclinical because there are few tell-tale symptoms before the infection becomes fatal. Since many honey bees can become infected and show symptoms for days, if at all, after the onset of infection, CBPV can infect entire hives before the virus is detected. Unfortunately, during this period, infectivity and serological tests are often imprecise and difficult to reproduce with consistent results.

Host spectrum

While CBPV primarily infects honey bees, the virus has been found to multiply in two types of carnivorous ants, the hairy wood ant ( Camponotus vagus ) and the red wood ant ( Formica rufa ). These ants - both of which belong to the subfamily of the scale ants (Formicinae) - become infected with CBPV through two mechanisms: by consuming bees carcasses that harbor the virus, or independently, by collecting infected honeydew. While the virus does not cause symptoms in the carnivorous ants, the ants can act as a reservoir for virus replication.

Similarity to other viruses

CBPV similar to the symptoms and the slow bee paralysis virus (SBPV) and Acute bee paralysis virus ( acute bee paralysis virus , ABPV). Although CBPV does not fall into the same family, Dicistroviridae, as the other two viruses, it has symptomatic similarities to these other viruses in that it causes paralysis as a fatal symptom of infection. In contrast to CBPV, the slow bee paralysis virus (SBPV) causes paralysis of the two front pairs of legs in honey bees ( Apis mellifera ), silkworms ( Bombyx mori ) and bumblebees ( Bombus spp.). This paralysis eventually leads to the death of the infected insect. It has been shown that SBPV is transmitted to beehives through infestation with mites of the species Varroa destructor . Because of the similarities between the two viruses, it is believed that the chronic bee paralysis virus has the same mode of transmission.

Systematics

The virus is currently (as of mid-March 2020) not yet officially confirmed by the International Committee on Taxonomy of Viruses (ICTV).

CBPV shares similarities with the Nodaviridae and Tombusviridae virus families , but it is so different from these two existing families that it must be considered a member of a new family of viruses. As a result, a complete taxonomic classification of CBPV is still pending. Since both families belong to the phylum Kitrinoviricota , newly created by the ICTV in March 2020 , membership of such a proposed family of CBPV-like viruses in this phylum is obvious, and thus not with the picornavirales , which belong to the phylum Pisuviricota .

Web links

Individual evidence

  1. ↑ a b ICTV Master Species List 2018b.v2 . MSL # 34, March 2019
  2. ↑ a b c ICTV: ICTV Master Species List 2019.v1 , New MSL including all taxa updates since the 2018b release, March 2020 (MSL # 35)
  3. ↑ ICTV: ICTV Taxonomy history: Enterovirus C , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  4. ↑ a b c d e f g h i j k l Magali Ribière, Violaine Olivier, Philippe Blanchard: Chronic bee paralysis: A disease and a virus like no other? . In: Journal of Invertebrate Pathology . 103, January 2010, pp. S120-S131. doi : 10.1016 / j.jip.2009.06.013 . PMID 19909978 .
  5. ↑ a b Chronic Bee Paralysis Virus , on: Microbe Wiki
  6. ↑ L. Bailey, BV Ball, JN Perry: Honeybee Paralysis: Its Natural Spread and its Diminished Incidence in England and Wales . In: Journal of Apicultural Research . 22, No. 3, January 1983, ISSN  0021-8839 , pp. 191-195. doi : 10.1080 / 00218839.1983.11100586 .
  7. ↑ a b Violaine Olivier, Philippe Blanchard, Soraya Chaouch, Perrine Lallemand, Frank Schurr, Olivier Celle, Eric Dubois, Noël Tordo, Richard Thiéry, Rémi Houlgatte, Magali Ribière: Molecular characterization and phylogenetic analysis of chronic bee paralysis virus, a honey bee virus . In: Virus Research . 132, No. 1-2, March 2008, pp. 59-68. doi : 10.1016 / j.virusres.2007.10.014 . PMID 18079012 .
  8. ↑ a b c Violaine Olivier, Philippe Blanchard, Soraya Chaouch, Perrine Lallemand, Frank Schurr, Olivier Celle, Eric Dubois, Noël Tordo, Richard Thiéry, Rémi Houlgatte, Magali Ribière: Molecular characterization and phylogenetic analysis of Chronic bee paralysis virus, a honey bee virus . In: Virus Research . 132, No. 1-2, March 2008, pp. 59-68. doi : 10.1016 / j.virusres.2007.10.014 . PMID 18079012 .
  9. ↑ Leslie Bailey: "Viruses Attacking the Honey Bee", Advances in Virus Research Volume 20, Advances in Virus Research, 20, Elsevier, 1976, pp. 271-304, doi: 10.1016 / s0065-3527 (08) 60507-2 , ISBN 978-0-12-039820-1 , PMID 775948
  10. Jump up ↑ Brenda V. Ball, Leslie Bailey: "Honey Bee Viruses", Encyclopedia of Virology, Elsevier, 1999, pp. 743-749, doi: 10.1006 / rwvi.1999.0139 , ISBN 978-0-12-227030-7
  11. ↑ a b H. A. Overton, KW Buck, L. Bailey, BV Ball: Relationships between the RNA Components of Chronic Bee-Paralysis Virus and those of Chronic Bee-Paralysis Virus Associate . In: Journal of General Virology . 63, No. 1, November 1, 1982, ISSN  0022-1317 , pp. 171-179. doi : 10.1099 / 0022-1317-63-1-171 . PDF
  12. ↑ Mike Bain: Chronic Bee Paralysis Virus , East Lothian Beekeepers Association, Scotland; on: globalnet, UK
  13. ↑ Magali Ribière, Perrine Lallemand, A.-L. Iscache, Frank Schurr, Olivier Celle, Philippe Blanchard, Violaine Olivier, J.-P. Faucon: Spread of Infectious Chronic Bee Paralysis Virus by Honeybee (Apis mellifera L.) Feces . In: Applied and Environmental Microbiology . 73, No. 23, December 1, 2007, ISSN  0099-2240 , pp. 7711-7716. doi : 10.1128 / AEM.01053-07 . PMID 17933946 . PMC 2168079 (free full text).
  14. ↑ Magali Ribiere, Perrine Lallemand, A.-L. Iscache, Frank Schurr, Olivier Celle, Philippe Blanchard, Violaine Olivier, J.-P. Faucon: Spread of infections chronic bee paralysis virus by honeybee ( Apis mellifera L.) feces . In: Applied and Environmental Microbiology . 73, No. 23, October 12, 2007, pp. 7711-7716. doi : 10.1128 / AEM.01053-07 . PMID 17933946 . PMC 2168079 (free full text).
  15. ↑ a b c d Chronic bee paralysis virus ( en-US ) August 18, 2010. Retrieved December 1, 2019.
  16. ↑ L. Bailey, RG Milne: The multiplication regions and interaction of acute and chronic bee-paralysis viruses in adult honey bees . In: Journal of General Virology . 4, No. 1, Jan. 1, 1969, pp. 9-14. doi : 10.1099 / 0022-1317-4-1-9 .
  17. ↑ a b How to Control a Varroa Mite Problem in Your Beehive ( en ) Retrieved December 2, 2019.
  18. ↑ a b Olivier Celle, Philippe Blanchard, Violaine Olivier, Frank Schurr, Nicolas Cougoule, Jean-Paul Faucon, Magali Ribière: Detection of chronic bee paralysis virus (CBPV) genome and its replicative RNA form in various hosts and possible ways of spread . In: Virus Research . 133, No. 2, May 2008, pp. 280-284. doi : 10.1016 / j.virusres.2007.12.011 . PMID 18243390 .
  19. ↑ Aurore Chevin, Bruno Coutard, Philippe Blanchard, Anne-Sophie Dabert-Gay, Magali Ribière-Chabert, Richard Thiéry: Characterization of Structural Proteins from Chronic Bee Paralysis Virus (CBPV) Using Mass Spectrometry , in: Viruses. 2015 Jun; 7 (6): 3329-3344. doi: 10.3390 / v7062774 , PMC 4488741 (free full text), PMID 26110588