Evolution and spread of Venezuelan equine encephalitis complex alphavirus in the Americas.

Venezuelan equine encephalitis (VEE) complex alphaviruses are important re-emerging arboviruses that cause life-threatening disease in equids during epizootics as well as spillover human infections. We conducted a comprehensive analysis of VEE complex alphaviruses by sequencing the genomes of 94 strains and performing phylogenetic analyses of 130 isolates using complete open reading frames for the nonstructural and structural polyproteins. Our analyses confirmed purifying selection as a major mechanism influencing the evolution of these viruses as well as a confounding factor in molecular clock dating of ancestors. Times to most recent common ancestors (tMRCAs) could be robustly estimated only for the more recently diverged subtypes; the tMRCA of the ID/IAB/IC/II and IE clades of VEE virus (VEEV) were estimated at ca. 149-973 years ago. Evolution of the IE subtype has been characterized by a significant evolutionary shift from the rest of the VEEV complex, with an increase in structural protein substitutions that are unique to this group, possibly reflecting adaptation to its unique enzootic mosquito vector Culex (Melanoconion) taeniopus. Our inferred tree topologies suggest that VEEV is maintained primarily in situ, with only occasional spread to neighboring countries, probably reflecting the limited mobility of rodent hosts and mosquito vectors.

Differential Vector Competency of Aedes albopictus Populations from the Americas for Zika Virus.

To evaluate the potential role of Aedes albopictus (Skuse) as a vector of Zika virus (ZIKV), colonized mosquitoes of low generation number (≤ F5) from Brazil, Houston, and the Rio Grande Valley of Texas engorged on viremic mice infected with ZIKV strains originating from Senegal, Cambodia, Mexico, Brazil, or Puerto Rico. Vector competence was established by monitoring infection, dissemination, and transmission potential after 3, 7, and 14 days of extrinsic incubation. Positive saliva samples were assayed for infectious titer. Although all three mosquito populations were susceptible to all ZIKV strains, rates of infection, dissemination, and transmission differed among mosquito and virus strains. Aedes albopictus from Salvador, Brazil, were the least efficient vectors, demonstrating susceptibility to infection to two American strains of ZIKV but failing to shed virus in saliva. Mosquitoes from the Rio Grande Valley were the most efficient vectors and were capable of shedding all three tested ZIKV strains into saliva after 14 days of extrinsic incubation. In particular, ZIKV strain DakAR 41525 (Senegal 1954) was significantly more efficient at dissemination and saliva deposition than the others tested in Rio Grande mosquitoes. Overall, our data indicate that, while Ae. albopictus is capable of transmitting ZIKV, its competence is potentially dependent on geographic origin of both the mosquito population and the viral strain.

Outbreak of Zika Virus Infection, Chiapas State, Mexico, 2015, and First Confirmed Transmission by Aedes aegypti Mosquitoes in the Americas.

BACKGROUND: After decades of obscurity, Zika virus (ZIKV) has spread through the Americas since 2015 accompanied by congenital microcephaly and Guillain-Barré syndrome. Although these epidemics presumably involve transmission by Aedes aegypti, no direct evidence of vector involvement has been reported, prompting speculation that other mosquitoes such as Culex quinquefasciatus could be involved. METHODS: We detected an outbreak of ZIKV infection in southern Mexico in late 2015. Sera from suspected ZIKV-infected patients were analyzed for viral RNA and antibodies. Mosquitoes were collected in and around patient homes and tested for ZIKV. RESULTS: Of 119 suspected ZIKV-infected patients, 25 (21%) were confirmed by RT-PCR of serum collected 1-8 days after the onset of signs and symptoms including rash, arthralgia, headache, pruritus, myalgia, and fever. Of 796 mosquitoes collected, A. aegypti yielded ZIKV detection by RT-PCR in 15 of 55 pools (27.3%). No ZIKV was detected in C. quinquefasciatus ZIKV sequences derived from sera and mosquitoes showed a monophyletic relationship suggestive of a point source introduction from Guatemala. CONCLUSIONS: These results demonstrate the continued, rapid northward progression of ZIKV into North America with typically mild disease manifestations, and implicate A. aegypti for the first time as a principal vector in North America.

IRES-Containing VEEV Vaccine Protects Cynomolgus Macaques from IE Venezuelan Equine Encephalitis Virus Aerosol Challenge.

Venezuelan equine encephalitis virus (VEEV) is an arbovirus endemic to the Americas that is responsible for severe, sometimes fatal, disease in humans and horses. We previously described an IRES-based VEE vaccine candidate based up the IE serotype that offers complete protection against a lethal subtype IE VEEV challenge in mice. Here we demonstrate the IRES-based vaccine's ability to protect against febrile disease in cynomolgus macaques. Vaccination was well tolerated and elicited robust neutralizing antibody titers noticed as early as day 14. Moreover, complete protection from disease characterized by absence of viremia and characteristic fever following aerosolized IE VEEV challenge was observed in all vaccinees compared to control animals, which developed clinical disease. Together, these results highlight the safety and efficacy of IRES-based VEEV vaccine to protect against an endemic, pathogenic VEEV IE serotype.

Venezuelan equine encephalitis virus activity in the Gulf Coast region of Mexico, 2003-2010.

Venezuelan equine encephalitis virus (VEEV) has been the causative agent for sporadic epidemics and equine epizootics throughout the Americas since the 1930s. In 1969, an outbreak of Venezuelan equine encephalitis (VEE) spread rapidly from Guatemala and through the Gulf Coast region of Mexico, reaching Texas in 1971. Since this outbreak, there have been very few studies to determine the northward extent of endemic VEEV in this region. This study reports the findings of serologic surveillance in the Gulf Coast region of Mexico from 2003-2010. Phylogenetic analysis was also performed on viral isolates from this region to determine whether there have been substantial genetic changes in VEEV since the 1960s. Based on the findings of this study, the Gulf Coast lineage of subtype IE VEEV continues to actively circulate in this region of Mexico and appears to be responsible for infection of humans and animals throughout this region, including the northern State of Tamaulipas, which borders Texas.

Genetic and anatomic determinants of enzootic Venezuelan equine encephalitis virus infection of Culex (Melanoconion) taeniopus.

Venezuelan equine encephalitis (VEE) is a re-emerging, mosquito-borne viral disease with the potential to cause fatal encephalitis in both humans and equids. Recently, detection of endemic VEE caused by enzootic strains has escalated in Mexico, Peru, Bolivia, Colombia and Ecuador, emphasizing the importance of understanding the enzootic transmission cycle of the etiologic agent, VEE virus (VEEV). The majority of work examining the viral determinants of vector infection has been performed in the epizootic mosquito vector, Aedes (Ochlerotatus) taeniorhynchus. Based on the fundamental differences between the epizootic and enzootic cycles, we hypothesized that the virus-vector interaction of the enzootic cycle is fundamentally different from that of the epizootic model. We therefore examined the determinants for VEEV IE infection in the enzootic vector, Culex (Melanoconion) taeniopus, and determined the number and susceptibility of midgut epithelial cells initially infected and their distribution compared to the epizootic virus-vector interaction. Using chimeric viruses, we demonstrated that the determinants of infection for the enzootic vector are different than those observed for the epizootic vector. Similarly, we showed that, unlike A. taeniorhynchus infection with subtype IC VEEV, C. taeniopus does not have a limited subpopulation of midgut cells susceptible to subtype IE VEEV. These findings support the hypothesis that the enzootic VEEV relationship with C. taeniopus differs from the epizootic virus-vector interaction in that the determinants appear to be found in both the nonstructural and structural regions, and initial midgut infection is not limited to a small population of susceptible cells.

Infection and dissemination of Venezuelan equine encephalitis virus in the epidemic mosquito vector, Aedes taeniorhynchus.

The mosquito Aedes taeniorhynchus is an important epidemic vector of Venezuelan equine encephalitis virus (VEEV), but detailed studies of its infection are lacking. We compared infection by an epidemic VEEV strain to that by an enzootic strain using virus titrations, immunohistochemistry, and a virus expressing the green fluorescent protein. Ae. taeniorhynchus was more susceptible to the epidemic strain, which initially infected the posterior midgut and occasionally the anterior midgut and cardia. Once dissemination beyond the midgut occurred, virus was present in nearly all tissues. Transmission of the epidemic strain to mice was first detected 4 days after infection. In contrast, the enzootic strain did not efficiently infect midgut cells but replicated in muscles and nervous tissue on dissemination. Because VEEV emergence can depend on adaptation to epidemic vectors, these results show that epidemic/enzootic strain comparisons not only comprise a useful model system to study alphavirus transmission by mosquitoes, but also have important public health implications.

Observaçöes sobre os níveis glicêmicos de Holochilus brasiliensis namus Thomas, 1897, hospedeiro natural do Schistosoma Mansoni na pré-Amazônia / Glycemic levels of Holochilus brasiliensis nanus Thomas, 1897, natural host of Schistosoma mansoni in lower Amazonia

Roedores silvestres, nascidos em biotério, descendentes de Holochilus b. manus, capturados na regiäo da Baixada Maranhese, localizada na Pré-Amazônia, foram infectados experimentalmente com Schistosoma mansoni, procedente da mesma Regiäo, com o objetivo de verificar a influência da infecçäo sobre os níveis glicêmicos. Um grupo de roedores näo infectados tiveram, também, seus níveis glicêmicos detereminados, para o conhecimento da concentraçäo normal de glicose. O estudo procedeu distinguindo os animais, tanto os normais quanto os infectados, por sexo, regime alimentar e idade de infecçäo. A quantificaçäo da glicose sérica foi feita pelo método da Orto-Toluidina, após sangrias semanais pelo plexo oftálmico, sempre no mesmo horário. Os resultados mostraram que ocorreu elevaçäo de pesos corporais de todos os animais normais, durante suas maturaçöes, ao passo que, os animais infectados, tiveram seus pesos em decréscimo, durante a evoluçäo da infecçäo. Os níveis glicêmicos estudados nos animais mostraram que as fêmeas possuem nível mais baixo e estável do que os machos, independente de terem sido alimentados ou näo. Os animais infectados aos 30 dias de vida tiveram seus níveis glicêmicos em declínio à proporçäo que a infecçäo evoluía, provavelmente, devido ao acometimento dos órgäos, como baço, fígado e pâncreas; enquanto que, os animais infectados aos 40 dias de vida, tiveram seus níveis de glicose, durante as 8 semanas de infecçäo, sem diferença significativa entre eles. O número de vermes adultos recuperados nos animais infectados com 30 dias de vida foi maior do que o número encontrado nos roedores do grupo. Os dados informaram, também, que, a idade ideal para a infecçäo deste novo modelo experimental, deva ser a de 30 dias de vida, semelhante a outros, como camundongos

Variaçöes nos níveis das células sanguíneas periféricas encontradas em Holochilus brasiliensis nanus Thomas, 1897, infectadas com Schistosoma mansoni Sambon, 1907, próprio da pré-Amazônia / Variations in peripheral blood cells levels found in Holochilus brasiliensis nanus Thomas, 1897, infected with Schistosoma mansoni Sambon, 1907, from pre-Amazonia

Foram constituídos quatro grupos de roedores silvestres para a contagem de células sangüíneas periféricas, da seguinte forma: Grupo I - formado de animais normais, nascidos em biotério, com 30 dias de vida; Grupo II - formado de animais que foram capturados no campo e considerados näo infectados com S. mansoni, após ovohelmintoscopia das fezes, realizada durante 30 dias de observaçäo; Grupo III - animais capturados no campo, nautralmente infectados com o esquistossomo, e o Grupo IV - de animais nascidos em biotério, com 30 dias de vida, e infectados com 150 cercárias de S. mansoni, oriundas da Regiäo da Baixada Maranhense. Semanalmente, a partir da data da infecçäo, estes animais foram sangrados e tiveram suas células sangüíneas periféricas contadas global e especificamente. Os resultados mostraram que o número de hemácias e leucócitos por mm3 näo variou nos animais normais, tanto de campo como de biotério. No grupo de animais experimentalmente infectados, foi observado decréscimo do número de hemácias à proporçäo que a infecçäo evoluia. Comportamento oposto foi verificado com os leucócitos. Elevados níveis de eosinófilos só foram observados nos animais com infecçäo natural. Estes resultados foram discutidos com dados da literatura e considerados importantes para complementar as informaçöes sobre este hospedeiro natural do trematódeo, oferecido como modelo experimental do verme, e para sua própria história natural