Virulence variation among epidemic and non-epidemic strains
of Saint Louis encephalitis virus circulating in Argentina |
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Authors: | María Elisa Rivarola Laura Beatriz Tauro Guillermo Albrieu Llinás Marta Silvia Contigiani |
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Institution: | Laboratorio de Arbovirus, Instituto de Virología Dr JM Vanella, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina |
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Abstract: | Saint Louis encephalitis virus caused an outbreak of febrile illness and encephalitis
cases in Córdoba, Argentina, in 2005. During this outbreak, the strain CbaAr-4005 was
isolated from Culex quinquefasciatus mosquitoes. We hypothesised
that this epidemic variant would be more virulent in a mouse model than two other
non-epidemic strains (78V-6507 and CorAn-9275) isolated under different
epidemiological conditions. To test this hypothesis, we performed a biological
characterisation in a murine model, including mortality, morbidity and infection
percentages and lethal infection indices using the three strains. Mice were separated
into age groups (7, 10 and 21-day-old mice) and analysed after infection. The strain
CbaAr-4005 was the most infective and lethal of the three variants, whereas the other
two strains exhibited a decreasing mortality percentage with increasing animal age.
The strain CbaAr-4005 produced the highest morbidity percentages and no significant
differences among age groups were observed. The epidemic strain caused signs of
illness in all inoculated animals and showed narrower ranges from the onset of
symptoms than the other strains. CbaAr-4005 was the most virulent for Swiss albino
mice. Our results highlight the importance of performing biological characterisations
of arbovirus strains likely to be responsible for emerging or reemerging human
diseases. |
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Keywords: | arbovirus flavivirus Saint Louis encephalitis virus biological characterisation virulence |
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