RESUMO
Zika virus (ZIKV) was first discovered in 1947 in Uganda but was not considered a public health threat until 2007 when it found to be the source of epidemic activity in Asia. Epidemic activity spread to Brazil in 2014 and continued to spread throughout the tropical and subtropical regions of the Americas. Despite ZIKV being zoonotic in origin, information about transmission, or even exposure of non-human vertebrates and mosquitoes to ZIKV in the Americas, is lacking. Accordingly, from February 2017 to March 2018, we sought evidence of sylvatic ZIKV transmission by sampling whole blood from approximately 2000 domestic and wild vertebrates of over 100 species in West-Central Brazil within the active human ZIKV transmission area. In addition, we collected over 24,300 mosquitoes of at least 17 genera and 62 species. We screened whole blood samples and mosquito pools for ZIKV RNA using pan-flavivirus primers in a real-time reverse-transcription polymerase chain reaction (RT-PCR) in a SYBR Green platform. Positives were confirmed using ZIKV-specific envelope gene real-time RT-PCR and nucleotide sequencing. Of the 2068 vertebrates tested, none were ZIKV positive. Of the 23,315 non-engorged mosquitoes consolidated into 1503 pools tested, 22 (1.5%) with full data available showed some degree of homology to insect-specific flaviviruses. To identify previous exposure to ZIKV, 1498 plasma samples representing 62 species of domestic and sylvatic vertebrates were tested for ZIKV-neutralizing antibodies by plaque reduction neutralization test (PRNT90). From these, 23 (1.5%) of seven species were seropositive for ZIKV and negative for dengue virus serotype 2, yellow fever virus, and West Nile virus, suggesting potential monotypic reaction for ZIKV. Results presented here suggest no active transmission of ZIKV in non-human vertebrate populations or in alternative vector candidates, but suggest that vertebrates around human populations have indeed been exposed to ZIKV in West-Central Brazil.
Assuntos
Infecção por Zika virus/epidemiologia , Infecção por Zika virus/virologia , Zika virus , Animais , Brasil/epidemiologia , Culicidae , Geografia Médica , Humanos , Mosquitos Vetores , Testes de Neutralização , Vigilância em Saúde Pública , Estudos Soroepidemiológicos , Infecção por Zika virus/transmissão , ZoonosesRESUMO
In June 2016, we continued surveillance for tick-borne viruses in eastern Kansas following upon a larger surveillance program initiated in 2015 in response to a fatal human case of Bourbon virus (BRBV) (Family Orthomyxoviridae: Genus Thogotovirus). In 4 d, we collected 14,193 ticks representing four species from four sites. Amblyomma americanum (L.) (Acari: Ixodidae) accounted for nearly all ticks collected (n = 14,116, 99.5%), and the only other species identified were Amblyomma maculatum Koch (Acari: Ixodidae), Dermacentor variabilis (Say) (Acari: Ixodidae) and Ixodes scapularis Say (Acari: Ixodidae). All ticks were tested for both BRBV and Heartland virus (Family Bunyaviridae: Genus Phlebovirus) in 964 pools. Five Heartland virus positive tick pools were detected and confirmed by real-time reverse transcription PCR (rRT-PCR), while all pools tested negative for BRBV. Each Heartland positive pool was composed of 25 A. americanum nymphs with positive pools collected at three different sites in Bourbon County. A. americanum is believed to be the primary vector of both Heartland and BRBVs to humans based upon multiple detections of virus in field-collected ticks, its abundance, and its aggressive feeding behavior on mammals including humans. However, it is possible that A. americanum encounters viremic vertebrate hosts of BRBV less frequently than viremic hosts of Heartland virus, or that BRBV is less efficiently passed among ticks by co-feeding, or less efficiently passed vertically from infected female ticks to their offspring resulting in lower field infection rates.
Assuntos
Ixodidae/virologia , Phlebovirus/isolamento & purificação , Animais , Feminino , Kansas , MasculinoRESUMO
Bourbon virus (Family Orthomyxoviridae: Genus Thogotovirus) was first isolated from a human case-patient residing in Bourbon County, Kansas, who subsequently died. Before becoming ill in late spring of 2014, the patient reported several tick bites. In response, we initiated tick surveillance in Bourbon County and adjacent southern Linn County during spring and summer of 2015. We collected 20,639 host-seeking ticks representing four species from 12 sites. Amblyomma americanum (L.) (Acari: Ixodidae) and Dermacentor variabilis (Say) (Acari: Ixodidae) accounted for nearly all ticks collected (99.99%). Three tick pools, all composed of adult A. americanum ticks collected in Bourbon County, were virus positive. Two pools were Heartland virus (Family Bunyaviridae: Genus Phlebovirus) positive, and one was Bourbon virus positive. The Bourbon virus positive tick pool was composed of five adult females collected on a private recreational property on June 5. Detection of Bourbon virus in the abundant and aggressive human-biting tick A. americanum in Bourbon County supports the contention that A. americanum is a vector of Bourbon virus to humans. The current data combined with virus detections in Missouri suggest that Bourbon virus is transmitted to humans by A. americanum ticks, including both the nymphal and adult stages, that ticks of this species become infected as either larvae, nymphs or both, perhaps by feeding on viremic vertebrate hosts, by cofeeding with infected ticks, or both, and that Bourbon virus is transstadially transmitted. Multiple detections of Heartland virus and Bourbon virus in A. americanum ticks suggest that these viruses share important components of their transmission cycles.
Assuntos
Vetores Aracnídeos/virologia , Ixodidae/virologia , Doenças Transmitidas por Carrapatos/transmissão , Animais , Feminino , Ixodidae/crescimento & desenvolvimento , Kansas , Larva/crescimento & desenvolvimento , Larva/virologia , Masculino , Ninfa/crescimento & desenvolvimento , Ninfa/virologia , Phlebovirus/isolamento & purificação , Thogotovirus/isolamento & purificaçãoRESUMO
West Nile virus ecology has yet to be rigorously investigated in the Caribbean Basin. We identified a transmission focus in Puerto Barrios, Guatemala, and established systematic monitoring of avian abundance and infection, seroconversions in domestic poultry, and viral infections in mosquitoes. West Nile virus transmission was detected annually between May and October from 2005 to 2008. High temperature and low rainfall enhanced the probability of chicken seroconversions, which occurred in both urban and rural sites. West Nile virus was isolated from Culex quinquefasciatus and to a lesser extent, from Culex mollis/Culex inflictus, but not from the most abundant Culex mosquito, Culex nigripalpus. A calculation that combined avian abundance, seroprevalence, and vertebrate reservoir competence suggested that great-tailed grackle (Quiscalus mexicanus) is the major amplifying host in this ecosystem. West Nile virus transmission reached moderate levels in sentinel chickens during 2007, but less than that observed during outbreaks of human disease attributed to West Nile virus in the United States.