Date Published: September 28, 2018
Publisher: Public Library of Science
Author(s): Pei-Shi Yen, Fadila Amraoui, Anubis Vega Rúa, Anna-Bella Failloux, Luciano Andrade Moreira.
The recent yellow fever epidemic in Brazil has raised the concern of outbreaks in neighboring countries, particularly in the Caribbean region where the vector Aedes aegypti is predominant. This threat comes from the past when in the Americas, this disease caused devastating urban epidemics. We report the vector competence of Ae. aegypti from Guadeloupe for yellow fever virus by determining different parameters describing virus infection, dissemination, and transmission. The results indicate that Ae. aegypti Guadeloupe are susceptible to yellow fever virus with viral particles detected in mosquito saliva at 14 and 21 days post-infection. Local authorities and more broadly, international organizations should maintain the active surveillance of Aedes mosquitoes and the spreading of human cases from South America.
Yellow fever (YF) is a mosquito-borne viral disease endemic to some countries of South America and sub-Saharan Africa. It can present various clinical features ranging from a self-limited, mild febrile illness to fatal symptoms such as hemorrhages and liver damages. Most of all cases reported annually (80–90%) occur in Africa where YF covers 44 countries . In South America, YF is described in less than 10 countries: Argentina, Bolivia, Brazil, Colombia, Ecuador, Paraguay, Peru, and Venezuela (http://ais.paho.org/phip/viz/ed_yellowfever.asp). In these locations, YF uses to periodically spread via epizootic outbreaks following the displacements of non-human primates . From July 2017 through March 2018, the states of Rio de Janeiro, Minas Gerais, and São Paulo in Brazil, counted 932 human cases including 300 fatal cases . Alarmingly, human cases were reported near São Paulo city, threatening the initiation of an urban transmission that has not been notified in the country since 1942.
Mosquitoes were analyzed at three time points following infection: 7, 14 and 21 days post infection (dpi). At 7 dpi, 56.7% (17/30) of mosquitoes examined had infected bodies (Fig 1). Among them, 29.4% (5/17) of mosquitoes were able to ensure a viral dissemination beyond the midgut barrier in the hemocele. No mosquitoes were able to transmit the virus with no viral particles detected in mosquito saliva. Later, at 14 dpi, a higher proportion, 70% (21/30) of mosquitoes had an infected body and among them, 57.1% (12/21) presented a positive viral dissemination into the hemocele. Then, 8.3% (1/12) had virus in saliva, indicative of viral transmission; one mosquito had 20 viral particles. At 21 dpi, the proportion of mosquitoes with infected body decreased to 50% (15/30) and among them, more than half (53.3%; 8/15) could ensure a viral dissemination. A slightly higher proportion of mosquitoes (12.5%; 1/8) with disseminated infection presented virus in saliva; one mosquito had 200 viral particles. Rates did not significantly vary according to dpi: 7 dpi (Chi-square test: χ2 = 2.57, df = 2, p = 0.27), 14 dpi (Chi-square test: χ2 = 3.21, df = 2, p = 0.20), and 21 dpi (Chi-square test: χ2 = 0.65, df = 2, p = 0.72).
Except Trinidad and Tobago in 1979 , the Caribbean has not suffered from YF since 1960. The ongoing YFV circulation in Brazil raises concern regarding viral importation into the Caribbean. However, the requirement of YF vaccination is not mandatory in many Caribbean islands (e.g. Haiti, Cuba), but restricted to the travelers coming from YF-epidemic countries (http://www.who.int/ith/ITH_country_list.pdf?ua=1). The disease control relies only on the check of vaccination card, which is insufficient for YF prevention. Thus, YF is still a threat for this region where Ae. aegypti is widely distributed. Here, although not based on vertebrate animal transmission model, we demonstrated that Ae. aegypti from Guadeloupe are susceptible to YFV and able to transmit viral particles from 14 days post-infection.