Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 28, Number 2—February 2022
Research Letter

Group IV Getah Virus in Culex Mosquitoes, Malaysia

Figures
Article Metrics
Author affiliations: Universiti Malaya, Kuala Lumpur, Malaysia (S.-S. Sam, N.-A. Mohamed-Romai-Noor, B.-T. Teoh, Z.-R. Hamim, H.-Y. Ng, J. Abd-Jamil, C.-S. Khor, S. AbuBakar); Monash University Malaysia, Selangor, Malaysia (S.-S. Hassan); Universiti Sains Malaysia, Pulau Pinang, Malaysia (H. Ahmad)

Cite This Article

Abstract

A new Getah virus (GETV) strain, B254, was isolated from Culex fuscocephalus mosquitoes captured at Mount Ophir, Malaysia, in 2012. Phylogenetic analyses revealed that GETV B254 is distinct from the old Malaysia GETV MM2021 strain but closely related to group IV GETV from Russia (LEIV16275Mag), China (YN12031), and Thailand (GETV/SW/Thailand/2017).

Getah virus (GETV) is an emerging mosquitoborne alphavirus of the family Togaviridae. The virus was first reported in 1955 from Culex gelidus mosquitoes collected near Kuala Lumpur, Malaysia (1). Serologic evidence of GETV infection was found in various large domestic mammals (2) and humans (3). GETV infections in these populations, however, were mostly inapparent. In other regions, reproductive failures in pregnant sows, death in piglets, and hind limb edema in racehorses, as well as neurologic symptoms and death in blue foxes, have been reported (47).

We conducted mosquito surveillance in the forests of 4 different states in Peninsular Malaysia, Perak, Pahang, Selangor, and Johor, during 2011–2014. We captured a total of 4,160 mosquitoes from the study sites by BG-Sentinel CO2 trap (Biogents AG, https://eu.biogents.com) with the addition of UV light and sorted them into 208 pools according to their species, determined by morphologic keys, and collection sites. We homogenized the pooled mosquitoes, inoculated them into C6/36 mosquito cells, and blind passaged for 5 passages. We obtained cytopathic effects from 1 of the pools on day 4 postinfection during the last passage. The pool comprised Cx. fuscocephalus mosquitoes collected from the forested area at Mount Ophir (Malay: Gunung Ledang) in Johor in 2012. We screened the culture supernatants by reverse transcription PCR (RT-PCR) using the in-house developed alphavirus generic primers targeting the nsP4 gene and flavivirus primers targeting the nonstructural 5–3′ untranslated region junction. A similar sample pool that showed cytopathic effects was found positive for the presence of alphaviruses, as indicated by a 683 bp amplicon. Sanger sequencing of the amplicon revealed high sequence similarity to GETV. We obtained the complete coding sequence of the GETV isolate, designated as B254, using 10 pairs of RT-PCR amplification primers and genome sequencing. We deposited the genome in GenBank (accession no. LR990838).

Figure

Maximum-clade credibility tree of complete coding sequences of Getah virus (GETV) strain B254 from Malaysia (black dot) and reference strains. Horizontal branches are drawn to a scale of estimated year of divergence. Times to the most recent common ancestor with 95% highest posterior density values (ranges in parentheses) are shown at nodes. Posterior probability values >0.6 of key nodes are shown. G, group.

Figure. Maximum-clade credibility tree of complete coding sequences of Getah virus (GETV) strain B254 from Malaysia (black dot) and reference strains. Horizontal branches are drawn to a scale of estimated year...

We constructed a maximum clade credibility tree using the Bayesian Markov chain Monte Carlo analysis based on the complete coding regions of GETV B254 and other GETV isolates available in GenBank (Figure). The GETV phylogeny revealed 4 major groups of viruses: group I (GI), GII, GIII, and GIV (8). GI and GII consisted of early identified GETV isolates; GI contained the Malaysia MM2021 isolate (1955), and GII, Japan Sagiyama (1956). The GIII and GIV comprised the most recent circulating virus strains. The newly isolated Malaysia GETV B254 is phylogenetically distinct from the ancestral Malaysia MM2021. It clustered within the GIV clade, which included the strains recovered in Russia (LEIV16275Mag, 2007), China (YN12031, 2012) and Thailand (GETV/SW/Thailand/2017). The B254 strain showed the highest nucleotide sequence homology with YN12031 (98.8%), isolated from the Armigeres subalbatus mosquito, and GETV/SW/Thailand/2017 (98.6%), isolated from pig serum.

Currently, only the GIII GETV lineage is associated with epidemic outbreaks. The GIV GETV, however, consisted of only a few virus strains. We calculated the mean evolutionary rate of GIV GETV at 4.10 × 10−4 substitutions/site/year and the rate for GIII at 2.98 × 10−4 substitutions/site/year. These results suggest that the GIV viruses may be under a different selection pressure, potentially involving a different host. It is also possible that GIV viruses are maintained in a yet-to-be-identified enzootic transmission cycle involving mosquitoes and asymptomatic hosts.

The Culex mosquitoes, particularly Cx. gelidus and Cx. tritaeniorhynchus, have been identified as the most predominant vector host for GETV in Malaysia (1,2). Cx. fuscocephalus mosquitoes, however, are not an uncommon vector; they have been known to carry the virus in China and Sri Lanka (9,10). Cx. fuscocephalus mosquitoes could be an emerging vector for GETV transmission in Malaysia along with the other Culex mosquitoes.

The high similarity of genome sequences of GIV GETV strains recovered thousands of kilometers apart raised the possibility that the virus may share a common dispersal route. One possible route linking the virus is the East Asian–Australasian flyway of migratory birds. GIV GETV could have been introduced to the regions through the migratory birds along the flyway, which included Malaysia as one of the stopover sites; the abundantly available Culex mosquitoes at the roosting sites could have maintained the transmission.

In summary, we identified a new GETV strain, B254, in Malaysia that is phylogenetically distinct from the old Malaysia MM2021 strain. The virus strain shares high similarities to the widely distributed GIV GETV. Although further surveillance studies are needed for confirmation, this finding suggests that GIV GETV strains could share a common dispersal origin, possibly through the bird transmigratory flyways.

Dr. Sam is a researcher at Tropical Infectious Diseases Research and Education Centre, Universiti Malaya. Her primary research interest is emerging mosquitoborne viral diseases.

Top

Acknowledgments

We thank World Refence Center for Emerging Viruses and Arboviruses, The University of Texas Medical Branch, Galveston, USA, for kindly providing us with the Malaysia GETV strain MM2021.

This study was supported in parts by the Ministry of Education Malaysia for niche area research under the Higher Institution Centre of Excellence (HICoE) program (project MO002–2019), the Fundamental Research Grant Scheme (FRGS FP014-2019A), and the Long Term Research Grant Scheme (LRGS/2011A/UM/Penyakit-Berjangkit).

Top

References

  1. Simpson  DI, Way  HJ, Platt  GS, Bowen  ET, Hill  MN, Kamath  S, et al. Arbovirus infections in Sarawak, October 1968-February 1970: GETAH virus isolations from mosquitoes. Trans R Soc Trop Med Hyg. 1975;69:358. DOIPubMedGoogle Scholar
  2. Marchette  NJ, Rudnick  A, Garcia  R, MacVean  DW. Alphaviruses in Peninusular Malaysia: I. Virus isolations and animal serology. Southeast Asian J Trop Med Public Health. 1978;9:31729.PubMedGoogle Scholar
  3. Marchette  NJ, Rudnick  A, Garcia  R. Alphaviruses in Peninsular Malaysia: II. Serological evidence of human infection. Southeast Asian J Trop Med Public Health. 1980;11:1423.PubMedGoogle Scholar
  4. Brown  CM, Timoney  PJ. Getah virus infection of Indian horses. Trop Anim Health Prod. 1998;30:24152. DOIPubMedGoogle Scholar
  5. Nemoto  M, Bannai  H, Tsujimura  K, Kobayashi  M, Kikuchi  T, Yamanaka  T, et al. Getah virus infection among racehorses, Japan, 2014. Emerg Infect Dis. 2015;21:8835. DOIPubMedGoogle Scholar
  6. Yang  T, Li  R, Hu  Y, Yang  L, Zhao  D, Du  L, et al. An outbreak of Getah virus infection among pigs in China, 2017. Transbound Emerg Dis. 2018;65:6327. DOIPubMedGoogle Scholar
  7. Shi  N, Li  LX, Lu  RG, Yan  XJ, Liu  H. Highly pathogenic swine Getah virus in blue foxes, eastern China, 2017. Emerg Infect Dis. 2019;25:12524. DOIPubMedGoogle Scholar
  8. Li  YY, Liu  H, Fu  SH, Li  XL, Guo  XF, Li  MH, et al. From discovery to spread: The evolution and phylogeny of Getah virus. Infect Genet Evol. 2017;55:4855. DOIPubMedGoogle Scholar
  9. Peiris  JS, Amerasinghe  PH, Amerasinghe  FP, Calisher  CH, Perera  LP, Arunagiri  CK, et al. Viruses isolated from mosquitoes collected in Sri Lanka. Am J Trop Med Hyg. 1994;51:15461. DOIPubMedGoogle Scholar
  10. Zhang  HL, Zhang  YZ, Yang  WH, Feng  Y, Nasci  RS, Yang  J, et al. Mosquitoes of Western Yunnan Province, China: seasonal abundance, diversity, and arbovirus associations. PLoS One. 2013;8:e77017. DOIPubMedGoogle Scholar

Top

Figure

Top

Cite This Article

DOI: 10.3201/eid2802.204887

Original Publication Date: January 13, 2022

Table of Contents – Volume 28, Number 2—February 2022

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.

Top

Comments

Please use the form below to submit correspondence to the authors or contact them at the following address:

Sazaly AbuBakar, Tropical Infectious Diseases Research and Education Centre and Department of Medical Microbiology, Faculty of Medicine, Universiti Malaya, 50603 Kuala Lumpur, Malaysia

Send To

10000 character(s) remaining.

Top

Page created: December 16, 2021
Page updated: January 22, 2022
Page reviewed: January 22, 2022
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
file_external