Vector competence of Italian Aedes albopictus populations for the chikungunya virus (E1-226V)

Abstract

Background

Chikungunya virus (CHIKV) is an emerging arbovirus, belonging to the Togaviridae family, Alphavirus genus, transmitted by Aedes spp. mosquitoes. Since 2007, two different CHIKV strains (E1-226A and E1-226V) have been responsible for outbreaks in European countries, including Italy, sustained by Ae. albopictus mosquitoes.

Findings

In this study, we assessed the susceptibility to the CHIKV E1-226V, strain responsible for the Italian 2007 outbreak, of eight Ae. albopictus populations collected in Northern, Central, Southern, and Island Italy, by experimental infections. Vector competence was evaluated by estimating infection, dissemination, and transmission rates (IR, DR, TR), through detection of the virus in the bodies, legs plus wings, and saliva, respectively. Additionally, vertical transmission was evaluated by the detection of the virus in the offspring. The results of our study demonstrated that the Italian populations of Ae. albopictus tested were susceptible to CHIKV infection, and can disseminate the virus outside the midgut barrier with high values of IR and DR. Viral infectious RNA was detected in the saliva of three populations from Central, Southern, and Island Italy, also tested for TR and population transmission rate (PTR) values. No progeny of the first and second gonotrophic cycle were positive for CHIKV.

Conclusions

This study strongly confirms the role of Ae. albopictus as a potential CHIKV vector in Italy. This may represent a threat, especially considering both the high density of this species, which is widespread throughout the country, and the increasing number of cases of imported arboviruses.

Author summary

Aedes albopictus is a proven vector of more than 20 different arboviruses and, as demonstrated by experimental infections, is an efficient vector of chikungunya virus (CHIKV) in several countries. In Italy this widespread species caused the first outbreak of CHIKV in Europe in 2007 (Emilia-Romagna region) and recently, after 10 years, two different outbreaks in the Central and Southern part of the country (Latium and Calabria regions) were reported. Symptoms of CHIKV are arthralgia and joint pain, skin rash, primarily of the trunk and limbs, but also commonly fever and myalgia. Complications of this disease are rare, but long-term sequelae often occur in a considerable number of patients in particular, in children, the elderly, and patients with chronic diseases. The recent circulation of CHIKV in Italy has highlighted the importance of investigating vector competence of Italian populations of Ae. albopictus from different areas. In this study, we experimentally infected several mosquito populations in order to assess the real risk of CHIKV epidemics in temperate zones and support efficient surveillance and control strategies.