Spillover infection

From Wikipedia, the free encyclopedia

Spillover infection, also known as pathogen spillover and spillover event, occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population. The pathogen is transmitted from the reservoir population and may or may not be transmitted within the host population. Due to climate change and land use expansion, the risk of viral spillover is predicted to significantly increase.[1][2]

Spillover zoonoses[edit]

Spillover is a common event; in fact, more than two-thirds of human viruses are zoonotic.[3] Most spillover events result in self-limited cases with no further human to human transmission, as occurs, for example, with rabies, anthrax, histoplasmosis or hidatidosis. Other zoonotic pathogens are able to be transmitted by humans to produce secondary cases and even to establish limited chains of transmission. Some examples are the Ebola and Marburg filoviruses, COVID-19, the MERS and SARS coronaviruses or some avian flu viruses. Finally, some few spillover events can result in the final adaptation of the microbe to the humans, who became a new stable reservoir, as occurred with the HIV virus resulting in the AIDS epidemic.[4]

The Fruit bat is believe to be the zoonotic agent responsible for the spillover of the Ebola Virus.

Most of the pathogens which are presently exclusive of humans were probably transmitted by other animals sometime in the past.[4] If the history of mutual adaptation is long enough, permanent host-microbe associations can be established resulting in co-evolution, and even on permanent integration of the microbe genome in the human genome, as it is the case of endogenous viruses. The closer the two species are in phylogenetic terms, the easier it is for microbes to overcome the biological barrier to produce successful spillovers. For this reason, other mammals are the main source of zoonotic agents for humans. For example, in the case of the Ebola virus, fruit bats, are the hypothesized zoonotic agent.[5]

During the late 20th century zoonotic spillover increased as the environmental impact of agriculture promoted increased land use and deforestation, changing wildlife habitat. As species shift their geographic range in response to climate change, the risk of zoonotic spillover is predicted to substantially increase, particularly in tropical regions that are experiencing rapid warming.[1] As forested areas of land are cleared for human use, there is increased proximity and interaction between wild animals and humans thereby increasing the potential for exposure.[6]

Intraspecies spillover[edit]

The Bumblebee is a potential reservoirs for several pollinator parasites.

Commercially bred bumblebees used to pollinate greenhouses can be reservoirs for several pollinator parasites including the protozoans Crithidia bombi, and Apicystis bombi,[7] the microsporidians Nosema bombi and Nosema ceranae,[7][8] plus viruses such as Deformed wing virus and the tracheal mites Locustacarus buchneri.[8] Commercial bees that escape the glasshouse environment may then infect wild bee populations. Infection may be via direct interactions between managed and wild bees or via shared flower use and contamination.[9][10] One study found that half of all wild bees found near greenhouses were infected with C. bombi. Rates and incidence of infection decline dramatically the further away from the greenhouses the wild bees are located.[11][12] Instances of spillover between bumblebees are well documented across the world but particularly in Japan, North America and the United Kingdom.[13][14]

Examples of Spillover Zoonosis
Disease Reservoir
Hepatitis E Wild Boar [15]
Ebola Fruit Bats [16]
HIV/AIDS Chimpanzee [17]
COVID-19 Bats [18]

See also[edit]


  1. ^ a b Carlson, Colin J.; Albery, Gregory F.; Merow, Cory; Trisos, Christopher H.; Zipfel, Casey M.; Eskew, Evan A.; Olival, Kevin J.; Ross, Noam; Bansal, Shweta (28 April 2022). "Climate change increases cross-species viral transmission risk". Nature. 607 (7919): 555–562. Bibcode:2022Natur.607..555C. doi:10.1038/s41586-022-04788-w. ISSN 1476-4687. PMID 35483403. S2CID 248430532. Retrieved 6 May 2022.
  2. ^ Power, AG; Mitchell, CE (Nov 2004). "Pathogen spillover in disease epidemics". The American Naturalist. 164 (Suppl 5): S79–89. doi:10.1086/424610. PMID 15540144. S2CID 16762851.
  3. ^ Woolhouse, Mark; Scott, Fiona; Hudson, Zoe; Howey, Richard; Chase-Topping, Margo (2012). "Human viruses: Discovery and emergence". Philosophical Transactions of the Royal Society B: Biological Sciences. 367 (1604): 2864–2871. doi:10.1098/rstb.2011.0354. PMC 3427559. PMID 22966141.
  4. ^ a b Wolfe, Nathan D.; Dunavan, Claire Panosian; Diamond, Jared (May 2007). "Origins of major human infectious diseases". Nature. 447 (7142): 279–283. Bibcode:2007Natur.447..279W. doi:10.1038/nature05775. ISSN 1476-4687. PMC 7095142. PMID 17507975.
  5. ^ Ebola. (2014). National Center for Emerging and Zoonotic Infectious Diseases, Division of High-Consequence Pathogens and Pathology, Department of Health & Human Services, CDC.
  6. ^ Rulli, Maria Cristina; Santini, Monia; Hayman, David T. S.; d'Odorico, Paolo (2017). "The nexus between forest fragmentation in Africa and Ebola virus disease outbreaks". Scientific Reports. 7: 41613. Bibcode:2017NatSR...741613R. doi:10.1038/srep41613. PMC 5307336. PMID 28195145.
  7. ^ a b Graystock, P; Yates, K; Evison, SEF; Darvill, B; Goulson, D; Hughes, WOH (2013). "The Trojan hives: pollinator pathogens, imported and distributed in bumblebee colonies". Journal of Applied Ecology. 50 (5): 1207–15. doi:10.1111/1365-2664.12134. S2CID 3937352.
  8. ^ a b Sachman-Ruiz, Bernardo; Narváez-Padilla, Verónica; Reynaud, Enrique (2015-03-10). "Commercial Bombus impatiens as reservoirs of emerging infectious diseases in central México". Biological Invasions. 17 (7): 2043–53. doi:10.1007/s10530-015-0859-6. ISSN 1387-3547.
  9. ^ Durrer, Stephan; Schmid-Hempel, Paul (1994-12-22). "Shared Use of Flowers Leads to Horizontal Pathogen Transmission". Proceedings of the Royal Society of London B: Biological Sciences. 258 (1353): 299–302. Bibcode:1994RSPSB.258..299D. doi:10.1098/rspb.1994.0176. ISSN 0962-8452. S2CID 84926310.
  10. ^ Graystock, Peter; Goulson, Dave; Hughes, William O. H. (2015-08-22). "Parasites in bloom: flowers aid dispersal and transmission of pollinator parasites within and between bee species". Proceedings of the Royal Society B: Biological Sciences. 282 (1813): 20151371. doi:10.1098/rspb.2015.1371. ISSN 0962-8452. PMC 4632632. PMID 26246556.
  11. ^ Otterstatter, MC; Thomson, JD (2008). "Does Pathogen Spillover from Commercially Reared Bumble Bees Threaten Wild Pollinators?". PLOS ONE. 3 (7): e2771. Bibcode:2008PLoSO...3.2771O. doi:10.1371/journal.pone.0002771. PMC 2464710. PMID 18648661.
  12. ^ Graystock, Peter; Goulson, Dave; Hughes, William O.H. (2014). "The relationship between managed bees and the prevalence of parasites in bumblebees". PeerJ. 2: e522. doi:10.7717/peerj.522. PMC 4137657. PMID 25165632.
  13. ^ Graystock, Peter; Blane, Edward J.; McFrederick, Quinn S.; Goulson, Dave; Hughes, William O. H. (2016). "Do managed bees drive parasite spread and emergence in wild bees?". International Journal for Parasitology: Parasites and Wildlife. 5 (1): 64–75. doi:10.1016/j.ijppaw.2015.10.001. PMC 5439461. PMID 28560161.
  14. ^ Carrington, Damian (18 July 2013). "Imported bumblebees pose risk to UK's wild and honeybee population – study". The Guardian.
  15. ^ Anheyer-Behmenburg, Helena E.; Szabo, Kathrin; Schotte, Ulrich; Binder, Alfred; Klein, Günter; Johne, Reimar (2017). "Hepatitis E Virus in Wild Boars and Spillover Infection in Red and Roe Deer, Germany, 2013–2015". Emerging Infectious Diseases. 23 (1): 130–133. doi:10.3201/eid2301.161169. PMC 5176221. PMID 27983488.
  16. ^ Mursel, Sena; Alter, Nathaniel; Slavit, Lindsay; Smith, Anna; Bocchini, Paolo; Buceta, Javier (2022). "Estimation of Ebola's spillover infection exposure in Sierra Leone based on sociodemographic and economic factors". PLOS ONE. 17 (9): e0271886. arXiv:2109.15313. Bibcode:2022PLoSO..1771886M. doi:10.1371/journal.pone.0271886. PMC 9436100. PMID 36048780.
  17. ^ "About HIV/AIDS | HIV Basics | HIV/AIDS | CDC". www.cdc.gov. 2022-06-30. Retrieved 2022-12-08.
  18. ^ Valencak, Teresa G.; Csiszar, Anna; Szalai, Gabor; Podlutsky, Andrej; Tarantini, Stefano; Fazekas-Pongor, Vince; Papp, Magor; Ungvari, Zoltan (October 2021). "Animal reservoirs of SARS-CoV-2: calculable COVID-19 risk for older adults from animal to human transmission". GeroScience. 43 (5): 2305–2320. doi:10.1007/s11357-021-00444-9. ISSN 2509-2723. PMC 8404404. PMID 34460063.

External links[edit]