Mayaro virus mimicking Chikungunya virus infection: first reported case in a Canadian traveler
Pabbaraju K 1, Wong A1, Gill K1, Turvey S2, Zelyas N1,2, Fonseca K1,3, Tellier R1,3 1Provincial Laboratory for Public Health of Alberta; 2University of Alberta; 3University of Calgary Background: Alphaviruses constitute a genus within the family Togaviridae; these arboviruses are present in many regions of the globe and depending on the species, typically cause a febrile illness with arthritis (eg Chikungunya virus, CHIKV) or meningoencephalitis (eg Eastern Equine Encephalitis virus). The recent global spread of CHIKV illustrates that, like other arboviruses, alphaviruses can become emergent. Methods: Diagnostic testing for arboviruses at ProvLab includes an in-house triplex real time PCR for Dengue, Zika and CHIKV and serological testing using commercial assays and referrals to the National Microbiology Laboratory (Winnipeg, Canada); in specific situations, investigational pan-alphaviruses, pan-flaviviruses and pan bunyaviruses gel based PCR assays are also used.
Results and Discussion: A Canadian traveler returning from a vacation in South America, which included Peru and a jungle tour in the Amazon basin, developed a febrile illness one day after his return; over the next few days he developed myalgias, arthralgias, conjunctivitis and a rash. Serology for CHIKV (Euroimmun) was initially negative but CHIK IgM was positive 19 days after symptom onset and IgG was positive at 38 days. Because the triplex PCR for Dengue, Zika and CHIKV was negative on a sample collected on day 4, further testing using a pan alphaviruses PCR targeting a well conserved segment within the nsP4 gene was performed. It yielded an amplicon of the expected 875 bp from which a sequence of 793 bp was obtained; BLAST analysis showed 98% identity with the sequence of a genotype D (“widely dispersed”) Mayaro virus previously isolated in 2000 from Peru. The near complete genome sequence (11099 bases) was then determined by PCR and Sanger sequencing directly from the sample. Based on phylogenetic comparison to all the full-genome sequences available in GenBank, this isolate clusters most closely with isolates within genotype D circulating in Peru from 1995 and 2010 and Venezuela from 2010 with greater than 98% sequence identity. Recently recombinant variants (2BR14 and HAITI15) isolated from a Brazilian patient returning to São Paulo from the Amazon basin in 2014, and from an eight-year-old child in Haiti in 2015 have been reported. These recombinations were not noted in our isolate. This is the first report of a case of Mayaro virus infection in a Canadian traveler. The areas he visited are known to harbor local transmission of Mayaro virus. The serologic cross-reactivity between Mayaro and CHIKV has been demonstrated before and is warned about in the Euroimmun product insert. The lack of specific clinical indicators and the positive CHIKV serology in this case illustrate that a large-scale emergence of Mayaro could be difficult to detect early in a background of high CHIKV activity. Molecular assays performed on acute samples will be essential.
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