Zika virus (ZIKV), once considered an obscure pathogen, spread rapidly from 2014 to 2016 to become an internationally notifiable condition of major public health concern. The relative importance of various Culex and Aedes species mosquitoes (Diptera: Culicidae) in ZIKV transmission is a topic of debate. Quantifying host use is important in determining the vectorial capacity of a mosquito species for transmitting ZIKV in nature. In the United States, few data are available on host use of Aedes aegypti L. (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae), confirmed and suspected vectors of ZIKV, respectively. Here, we report results of bloodmeal analysis to quantify host use of confirmed (Ae. aegypti) and suspected (Ae. albopictus and Culex quinquefasciatus Say (Diptera: Culicidae)) vectors of ZIKV in two Florida counties. At an auto salvage yard in Indian River County, Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus fed mainly on humans, taking 90.2, 90.8, and 78.6% of bloodmeals from humans, respectively. At a residential area in Martin County, Ae. aegypti, Ae. albopictus took 61.5 and 66.7% of bloodmeals from humans, higher than Cx. quinquefasciatus (11.1%). Patterns of host use suggest that Ae. aegypti and Ae. albopictus are the most likely vectors of ZIKV in Florida and that Cx. quinquefasciatus would likely play a lesser role in ZIKV transmission in Florida. However, the relative importance of the three species in ZIKV transmission is likely location and population specific. Detailed studies quantifying other parameters of vectorial capacity, including vector competence, are needed in order to determine the actual role for each species in ZIKV transmission.
Evidence of sylvatic yellow fever was first reported in Atlantic Forest areas in Espírito Santo, Brazil, during a yellow fever virus (YFV) outbreak in 1931. An entomological survey was conducted in six forest sites during and after an outbreak reported ~80 years after the last case in the area. Among 10,658 mosquitoes of 78 species, Haemagogus leucocelaenus, and Hg. janthinomys/capricornii were considered the main vectors as they had a relatively high abundance, co-occurred in essentially all areas, and showed high YFV infection rates. Sabethes chloropterus, Sa. soperi, Sa. identicus, Aedes aureolineatus, and Shannoniana fluviatilis may have a secondary role in transmission. This is the first report of Sa. identicus, Ae. aureolineatus, and Sh. fluviatilis infected with YFV. Our study emphasizes the importance of entomological monitoring and maintenance of high vaccination coverage in receptive areas to YFV transmission.
The susceptibility of two fish and four mosquito species to the Caiman yacare haemoparasite Hepatozoon caimani was experimentally investigated. Mosquitoes belonging to four species (Aedes fluviatilis, Aedes albopictus, Aedes aegypti and Culex quinquefasciatus) were blood-fed on two naturally infected C. yacare from the Central-West Region of Brazil that exhibited distinct levels of parasitaemia: caimans A (11.05%) and B (1.25%). None of the engorged A. fluviatilis, A. albopictus or A. aegypti mosquitoes fed on caiman A survived for the duration of the sporogonic cycle; the great majority of the engorged mosquitoes died within 48 h of the blood meal. All A. aegypti fed on caiman B were negative, whereas 91.3% of dissected C. quinquefasciatus fed on the same caiman contained oocysts. Characid fish-Metynnis sp. and Astyanax sp.-were individually fed with C. quinquefasciatus females previously engorged (21-23 days) on caiman B. No parasite was found in the Astyanax fish. By contrast, 100% of the Metynnis fish depicted numerous cysts harbouring cystozoites identical to those of H. caimani, even more than 8 months after the ingestion of the infected mosquitoes. The cysts were located near the veins of the liver and, in some cases, close to the tunica intima of these vessels. No inflammatory reaction was observed. Gametocytes were observed in the blood smears of juvenile caimans that had ingested infected fish 9-12 weeks earlier. The potential role of fish as paratenic vertebrate hosts of H. caimani in nature is discussed.
Mosquitoes display highly variable oviposition strategies and behavior. By using a high-speed camera, we detailly documented for the first time the egg-throwing strategy of the sylvatic yellow fever vector Sabethes albiprivus Theobald in laboratory. An oviposition trap made with sapucaia nut for field collection of treehole mosquitoes and obtaining Sa. albiprivus eggs either in the field or in the laboratory colony is described.
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