Friday, 3 July 2015

Ebola virus: wild and domestic animals, plants and insects...

Initial Ebola virus (EBOV) infection of humans is a rare zoonotic spillover event.

Hypsignathus monstrosus, Epomops franqueti and Myonycteris torquatebats, all fruit-eating megabats of the family Pteropodidae, are considered to be important reservoir hosts, yet they do not show signs of disease.[1]

While a great deal remains unknown about the identity and spectrum of natural ebolavirus hosts,[1] zoonoses appear to co-occur with bat pregnancy.[2]

Animals that have died from ebolavirus infections include:[3,4]

  • Duiker (Cephalophus sp.; an antelope) 
  • Gorilla (Gorilla gorilla) 
  • Chimpanzee (Pan troglodytes)

Living animals found to harbour ebolavirus RNA include:[1,4,23]

  • Cynomolgus macaque monkey (Macaca fascicularis; RESTV) 
  • Franquet’s epauletted fruit bat (Epomops franqueti; EBOV) 
  • Hammer-headed bat (Hypsignathus monstrosus; EBOV) 
  • Little collared fruit bat (Myonycteris torquata; EBOV)
Those animals with only antibodies to EBOV in the absence of infectious virus, suggesting past exposure include:[5,6]

  • Domestic dogs (Canis lupus familiaris
  • Peter’s lesser epauletted fruit bat (Micropterus pusillus; fruit-eating) 
  • Angolan free-tailed bat (Mops condylurus; insect-eating) 
  • Giant roundleaf bat (Hipposideros gigas; insect-eating) 
  • Egyptian fruit bat (Roussetus aegyptiacus; fruit-eating) 
  • Geoffrey’s rousette (Rousettus amplexicaudatus; a bat species; fruit-eating) 
  • Lord Derby’s scaly-tailed squirrel (Anomalurus derbianus)
Porcupines (Hystrix cristata) have been implicated as a source for human EBOV exposure but virus-positive animals have not been documented.[4]

Between nine and 25% of 337 domestic dogs from various towns and villages in Gabon during an EBOV outbreak in 2001-2002 were identified as possible hosts for EBOV when found to be seropositive.[7,8] It was not known when they became seropositive nor has it been experimentally determined that dogs are able to host an active EBOV infection.[9,10] Dogs were observed in contact with suspected virus-laden fluids and with other animals during the Gabon outbreak but seropositive dog specimens did not contain EBOV antigen or viral RNA. Three specimens from these seropositive dogs did not yield infectious virus in cell culture either and thus there remains no documented evidence for a canine source of human EBOV infection. In 2014, two dogs owned by human cases of EBOV/Mak in Spain (euthanized without testing [11]) and the United States of America (tested negative for EBOV[12,13]) did not exhibit any signs of disease.

Domestic pigs have been found to be a natural host for the Reston ebolavirus[9,14] and antibodies to EBOV have also been found in guinea pigs, an animal that can also be experimentally infected.[15] Domestic dogs and guinea pigs appear to become infected without symptoms.[6,7] Horses, mice, guinea pigs and goats have been experimentally inoculated with EBOV to produce antisera or test therapeutic preparations.[16,17]

Pigs experimentally infected with a member of the Zaire ebolavirus become symptomatic.[8] NHP, guinea pigs and mice have been used to examine aspects of disease progression and exhibit various degrees of disease when experimentally infected.[18,19]

On a few occasions in one study into possible hosts, a low viral load of EBOV could be sporadically recovered after inoculation of a snake (up to 11 days post inoculation), a mouse (up to nine days later) and a spider (21 days later) but the authors of this study concluded that these results could have represented residual inoculum.[21]

Plants, arthropods, cows, cats and sheep have not been found to naturally carry or host ebolavirus infection but only small numbers of some species have been examined.[3,20-22]


References...

  1. Leroy EM, Kumulungui B, Pourrut X, et al. Fruit bats as reservoirs of Ebola virus. Nature 2005;438:575-6. 
  2. Plowright RK, Eby P, Hudson PJ, et al. Ecological dynamics of emerging bat virus spillover. Proc Biol Sci 2015;282:20142124. 
  3. Olson SH, Reed P, Cameron KN, et al. Dead or alive: animal sampling during Ebola hemorrhagic fever outbreaks in humans. Emerg Health Threats J 2012;5 
  4. Lahm SA, Kombila M, Swanepoel R, Barnes RF. Morbidity and mortality of wild animals in relation to outbreaks of Ebola haemorrhagic fever in Gabon, 1994-2003. Trans R Soc Trop Med Hyg 2007;101:64-78. 
  5. Marsh GA, Haining J, Robinson R, et al. Ebola Reston virus infection of pigs: clinical significance and transmission potential. J Infect Dis 2011;204 Suppl 3:S804-9. 
  6. Gonzalez JP, Herbreteau V, Morvan J, Leroy EM. Ebola virus circulation in Africa: a balance between clinical expression and epidemiological silence. Bull Soc Pathol Exot 2005;98:210-7. 
  7. Allela L, Boury O, Pouillot R, et al. Ebola virus antibody prevalence in dogs and human risk. Emerg Infect Dis 2005;11:385-90. 
  8. Weingartl HM, Nfon C, Kobinger G. Review of Ebola virus infections in domestic animals. Dev Biol (Basel) 2013;135:211-8. 
  9. Stansfield SK, Scribner CL, Kaminski RM, Cairns T, McCormick JB, Johnson KM. Antibody to Ebola virus in guinea pigs: Tandala, Zaire. J Infect Dis 1982;146:483-6. 
  10. Connolly BM, Steele KE, Davis KJ, et al. Pathogenesis of experimental Ebola virus infection in guinea pigs. J Infect Dis 1999;179 Suppl 1:S203-17. 
  11. Why Dallas Won't Kill The Dog Of The Texas Nurse With Ebola. Business Insider, 2014. (Accessed 27/4/2015, at http://www.businessinsider.com.au/what-will-happen-to-dallas-nurses-dog-2014-10
  12. Starting today, Dallas Animal Services will begin testing Nina Pham’s year-old dog Bentley for Ebola. The Dallas Morning News, 2014. (Accessed 17/4/2015, at http://thescoopblog.dallasnews.com/2014/10/starting-today-dallas-animal-services-will-begin-testing-nina-phams-year-old-dog-bentley-for-ebola.html/.) 
  13. EBOLAVIRUS, ANIMAL RESERVOIR (05): USA, DOG, NOT. 2014. (Accessed 01/05/2015, at http://promedmail.org/direct.php?id=20141026.2901733
  14. Barrette RW, Metwally SA, Rowland JM, et al. Discovery of swine as a host for the Reston ebolavirus. Science 2009;325:204-6. 
  15. Rouquet P, Froment JM, Bermejo M, et al. Wild animal mortality monitoring and human Ebola outbreaks, Gabon and Republic of Congo, 2001-2003. Emerg Infect Dis 2005;11:283-90. 
  16. Kudoyarova-Zubavichene NM, Sergeyev NN, Chepurnov AA, Netesov SV. Preparation and use of hyperimmune serum for prophylaxis and therapy of Ebola virus infections. J Infect Dis 1999;179 Suppl 1:S218-23. 
  17. Bray M, Davis K, Geisbert T, Schmaljohn C, Huggins J. A mouse model for evaluation of prophylaxis and therapy of Ebola hemorrhagic fever. J Infect Dis 1998;178:651-61. 
  18. Ebihara H, Takada A, Kobasa D, et al. Molecular determinants of Ebola virus virulence in mice. PLoS Pathog 2006;2:e73. 
  19. Geisbert TW, Young HA, Jahrling PB, Davis KJ, Kagan E, Hensley LE. Mechanisms underlying coagulation abnormalities in ebola hemorrhagic fever: overexpression of tissue factor in primate monocytes/macrophages is a key event. J Infect Dis 2003;188:1618-29. 
  20. Turell MJ, Bressler DS, Rossi CA. Short report: lack of virus replication in arthropods after intrathoracic inoculation of Ebola Reston virus. Am J Trop Med Hyg 1996;55:89-90. 
  21. Swanepoel R, Leman PA, Burt FJ, et al. Experimental inoculation of plants and animals with Ebola virus. Emerg Infect Dis 1996;2:321-5. 
  22. Ebola haemorrhagic fever in Sudan, 1976. Report of a WHO/International Study Team. Bull World Health Organ 1978;56:247-70. 
  23. Miranda ME, Ksiazek TG, Retuya TJ, Khan AS, Sanchez A, Fulhorst CF, Rollin PE, Calaor AB, Manalo DL, Roces MC, Dayrit MM, Peters CJ. Epidemiology of Ebola (subtype Reston) virus in the Philippines. J Infect Dis. 1999 Feb;179 Suppl 1:S115-9.