Feline coronavirus isolates from a part of Brazil: insights into molecular epidemiology and phylogeny inferred from the 7b gene

MYRRHA, Luciana Wanderley; SILVA, Fernanda Miquelitto Figueira; VIDIGAL, Pedro Marcus Pereira; RESENDE, Maurício; BRESSAN, Gustavo Costa; FIETTO, Juliana Lopes Rangel; SANTOS, Marcus Rebouças; SILVA, Laura Morais Nascimento; ASSAO, Viviane Sisdelli; SILVA-JÚNIOR, Abelardo; de ALMEIDA, Márcia Rogéria

The authors have shown that Brazilian FCoV isolates were recently introduced from the North America, and that evolution of the 7b gene was possibly shaped by a combination of high rates of nucleotide substitution (5.686 × 10 −4 ) and purifying selection. Furthermore, the time tree of the present study suggests that FCoV introduction in Brazil occurred over the past of 40 years. Additionally, the findings of the present study suggest that both the internal mutation theory [23, 31] and the hypothesis of distinct virulent (FIPV) and avirulent (FECV) strains circulating [3] possibly cannot be taken as valid for the 7b gene. The authors have reported high conservation among sequences of Brazilian isolates and a strong correlation between the geographic origin of viral isolates and the genealogy predicted from the 7b gene. Thus, it is more plausible that FIP is clinically manifested in cats, mainly due to host and environmental factors and independent of genetic differences between FECV and FIPV. Comparative sequence analysis may eventually not be sufficient to answer the FECV/FIPV question. The numbers in parentheses correspond to the 95% lower and upper bounds of the highest-probability density intervals. a) AI: association index; PS: parsimony score; MC: maximum monophyletic clade; b) Expected value on null hypothesis (random phylogeny-trait association). I) Less-pathogenic biotype of FCoV; II) Pathogenic biotype of FCoV. *Statistical significance of tests: P<0.01.