Performance assessment of a multi-epitope chimeric antigen for the serological diagnosis of acute Mayaro fever.

Mayaro virus (MAYV), which causes mayaro fever, is endemic to limited regions of South America that may expand due to the possible involvement of Aedes spp. mosquitoes in its transmission. Its effective control will require the accurate identification of infected individuals, which has been restricted to nucleic acid-based tests due to similarities with other emerging members of the Alphavirus genus of the Togaviridae family; both in structure and clinical symptoms. Serological tests have a more significant potential to expand testing at a reasonable cost, and their performance primarily reflects that of the antigen utilized to capture pathogen-specific antibodies. Here, we describe the assembly of a synthetic gene encoding multiple copies of antigenic determinants mapped from the nsP1, nsP2, E1, and E2 proteins of MAYV that readily expressed as a stable chimeric protein in bacteria. Its serological performance as the target in ELISAs revealed a high accuracy for detecting anti-MAYV IgM antibodies. No cross-reactivity was observed with serum from seropositive individuals for dengue, chikungunya, yellow fever, Zika, and other infectious diseases as well as healthy individuals. Our data suggest that this bioengineered antigen could be used to develop high-performance serological tests for MAYV infections.

Wolbachia significantly impacts the vector competence of Aedes aegypti for Mayaro virus.

Wolbachia, an intracellular endosymbiont present in up to 70% of all insect species, has been suggested as a sustainable strategy for the control of arboviruses such as Dengue, Zika and Chikungunya. As Mayaro virus outbreaks have also been reported in Latin American countries, the objective of this study was to evaluate the vector competence of Brazilian field-collected Ae. aegypti and the impact of Wolbachia (wMel strain) upon this virus. Our in vitro studies with Aag2 cells showed that Mayaro virus can rapidly multiply, whereas in wMel-infected Aag2 cells, viral growth was significantly impaired. In addition, C6/36 cells seem to have alterations when infected by Mayaro virus. In vivo experiments showed that field-collected Ae. aegypti mosquitoes are highly permissive to Mayaro virus infection, and high viral prevalence was observed in the saliva. On the other hand, Wolbachia-harboring mosquitoes showed significantly impaired capability to transmit Mayaro virus. Our results suggest that the use of Wolbachia-harboring mosquitoes may represent an effective mechanism for the reduction of Mayaro virus transmission throughout Latin America.

Seasonal variation and age-related correlates of Buggy Creek virus (Togaviridae) infection in nestling house sparrows.

Wild birds are rarely found with active arbovirus infections, and relatively little is known about the patterns of viremia they exhibit under field conditions or how infection varies with date, bird age, or other factors that potentially affect transmission dynamics. Buggy Creek virus (BCRV; Togaviridae, Alphavirus) is an arbovirus associated with colonially nesting Cliff Swallows (Petrochelidon pyrrhonota) and transmitted by its vector, the hematophagous swallow bug (Oeciacus vicarius), an ectoparasite of the Cliff Swallow. Introduced House Sparrows (Passer domesticus) that have occupied swallow nests at colony sites in peridomestic settings are also exposed to BCRV when fed upon by swallow bugs. We used data from 882 nestling House Sparrows in western Nebraska from 2006 to 2008 to examine seasonal variation and age-related correlates of virus infection in the field. Over 17% of nestling House Sparrows had active infections. Prevalence was higher in 2007 than in 2008 when birds from all colony sites were analyzed, but there was no significant difference between years for sites sampled in both seasons. Buggy Creek virus prevalence was similar in early and late summer, with a peak in midsummer, coinciding with the greatest swallow bug abundance. Nestlings 10 days of age and younger were most commonly infected, and the likelihood of BCRV infection declined for older nestlings. Average viremia titers also declined with age (but did not vary with date) and were high enough at all nestling ages to likely infect blood-feeding arthropods (swallow bugs). Length of viremia for nestlings in the field was ≥4 days, in agreement with an earlier study of BCRV. Nestling birds offer many advantages for field studies of arbovirus amplification and transmission.

[Taxonomic structure of Orthomyxoviridae: current views and immediate prospects].

Analysis of taxonomic structure of Orthomyxoviridae was undertaken in view of its anticipated evolution. Four concepts of circulation of influenza A viruses in the biosphere are discussed, viz. anthrponose, zooanthroponose, metastrongilose, and protozoan. All of them may be considered in the framework of the general zooantroponose concept. Influenza B and C viruses can not be regarded as strictly anthroponose. Comparative molecular-genetic analysis of the genus Thogotovirus provides a basis for the designation of Thogoto and Batken-Dhori as independent geni. It is speculated that t he proof of transmission of Isaviruses by copepods Caligus elongates and Lepeophtheirus salmonis (Crustacea: Copepoda) may open up a new line of developments in arborvirology since crustacean vectors of viruses have never been described before.

Epidemic O'Nyong-Nyong fever in southcentral Uganda, 1996-1997: entomologic studies in Bbaale village, Rakai District.

Entomologic studies were conducted between January 27 and February 2, 1997, in Bbaale village in southcentral Uganda during an o'nyong-nyong (ONN) virus epidemic, which began in mid 1996 and continued into 1997. The objectives were to confirm the role of anophelines in ONN virus transmission and to examine other mosquito species as epidemic vectors of ONN virus. Of 10,050 mosquitoes collected using light traps and pyrethrum knockdown sprays, Anopheles (Cellia) funestus Giles was presumed to be the principal vector because it was the most abundant mosquito species from which a strain of ONN virus was isolated. This virus was isolated for the first time from a culicine species, Mansonia (Mansonioides) uniformis Theobald. Bwamba virus and Nyando virus were also isolated from An. funestus.

Determination of natural versus laboratory human infection with Mayaro virus by molecular analysis.

A laboratory worker developed clinical signs of infection with Mayaro virus (Togaviridae), an arbovirus of South and Central America, 6 days after preparation of Mayaro viral antigen and 10 days after a trip to a rain forest. There was no evidence of skin lesions during the antigen preparation, and level 3 containment safety measures were followed. Therefore, molecular characterization of the virus was undertaken to identify the source of infection. RT-PCR and DNA sequence comparisons proved the infection was with the laboratory strain. Airborne Mayaro virus contamination is thus a hazard to laboratory personnel.

[Arbovirus infections. From virus, mosquitoes, animals and humans]. / Arboviroses. Des virus, des moustiques, des animaux et des hommes.

Arboviruses occur throughout the world in plants and animals: reptiles, birds and mammals including man. These relatively recent RNA-containing viruses have great evolutionary potential and are a major cause of epidemics. Arboviruses exhibit a dual life cycle involving continual transmission to and from the vertebrate host and arthropod vector which ingests or inoculates the agent during blood meals. Agents belong to many different viral families and represent an important source of emerging diseases. Because of the mode of transmission is vectorial, spread can enhanced by man-made changes in the ecosystem. This risk is often underestimated. The population explosion provides a great opportunity for the progression of these arboviruses.

Isolation and experimental oral transmission in pigs of a porcine reproductive and respiratory syndrome virus isolate.

A virus inducing a cytopathic effect on porcine alveolar macrophages was isolated from the lungs of a pig with respiratory problems and lesions of proliferative and necrotizing pneumonia. The isolate was found to react with porcine reproductive and respiratory syndrome virus (PRRSV) monoclonal antibodies by indirect immunofluorescence and was designated LHVA-93-3. The virus could also be propagated on the MARC-145 cell line. The LHVA-93-3 macrophage-passaged isolate was inoculated orally or intranasally in four-week-old specific pathogen-free pigs. Histologically, focal to multifocal lesions of proliferative, necrotizing and interstitial pneumonia could be observed in the lungs of pigs inoculated orally or intranasally, 6 and 10 days post-inoculation. Virus could be reisolated from essentially the same tissues including serum following both routes of infection. The distribution of PRRSV antigens in fixed tissues as determined by immunogold silver staining (IGSS) was similar in orally or intranasally inoculated pigs. The results of this experimental transmission study indicate that pigs may become infected by PRRSV following oral as well as intranasal exposure.

Inefficient mechanical transmission of Langat (tick-borne encephalitis virus complex) virus by blood-feeding mites (Acari) to laboratory mice.

One day after feeding on a viremic mouse, tropical rat mites, Ornithonyssus bacoti (Hirst), transmitted Langat (tick-borne encephalitis virus complex) virus to a naive suckling mouse in one of four trials. However, no transmissions to naive mice by O. bacoti were recorded either immediately after the viremic blood meal (0/4 trials) or on days 4-18 (0/20 trials). After feeding on a viremic mouse, chicken mites, Dermanyssus gallinae (De Geer), failed to transmit Langat virus to naive suckling mice in any trials (0/24). Although virus failed to replicate in either species of mite, it was detectable in 20% (2/10) of O. bacoti individuals 1 d after a viremic blood meal, but only immediately after the viremic blood meal in 20% (2/10) of D. gallinae mites. Neither mite appears to be an efficient vector of Langat virus.

Insect-transmitted vertebrate viruses: flaviviridae.

The Flaviviridae include almost 70 viruses, nearly half of which have been associated with human disease. These viruses are among the most important arthropod-borne viruses worldwide and include dengue, yellow fever, and Japanese encephalitis viruses. Morbidity and mortality caused by these viruses vary, but collectively they account for millions of encephalitis, hemorrhagic fever, arthralgia, rash, and fever cases per year. Most of the members of this family are transmitted between vertebrate hosts by arthropod vectors, most commonly mosquitoes or ticks. Transmission cycles can be simple or complex depending on the hosts, vectors, the virus, and the environmental factors affecting both hosts and viruses. Replication of virus in invertebrate hosts does not seem to result in any significant pathology, which suggests a close evolutionary relationship between virus and vector. Another example of this relationship is the ability of these viruses to grow in invertebrate cell culture, where replication usually results in a steady state, persistent infection, often without cytopathic effect. Yields of virus from insect cell culture vary but are generally similar to yields in vertebrate cells. Replication kinetics are comparable between insect and vertebrate cell lines, despite differences in incubation temperature. Both vertebrate and insect cell culture systems continue to play a significant role in flavivirus isolation and the diagnosis of disease caused by these agents. Additionally, these culture systems permit the study of flavivirus attachment, penetration, replication, and release from cells and have been instrumental in the production and characterization of live-attenuated vaccines. Both vertebrate and insect cell culture systems will continue to play a significant role in basic and applied flavivirus research in the future.

An outbreak of epidemic polyarthritis (Ross River virus disease) in the Northern Territory during the 1990-1991 wet season.

OBJECTIVE: To describe the epidemiology of a large outbreak of epidemic polyarthritis in the Northern Territory during the wet season of 1990-1991. DESIGN, SETTING AND PARTICIPANTS: Arbovirus cases notified to the Northern Territory Department of Health and Community Services by general practitioners and local laboratories between 1 July 1990 and 30 June 1991. MAIN OUTCOME MEASURES: Date and place of infection, age, sex and symptoms. RESULTS: Doctors in the Northern Territory notified 368 cases; another 14 were infected interstate. The epidemic started in September, peaked in January and tailed off in April. The highest attack rates occurred in the rural areas of Jabiru, Litchfield Shire and Katherine. Those most affected were 30-34 year olds. Children, the elderly and Aboriginal people were under-represented. CONCLUSIONS: Epidemic polyarthritis is a wet season problem in the Northern Territory, affecting the rural towns and districts more than the cities. Pre-planned mosquito control measures (effective water drainage and larval control) limited the extent of the 1990-1991 epidemic in Darwin City and Palmerston. The low attack rate in children reflects asymptomatic and less clinically severe infections. The under-representation of Aboriginal people may be the result of infection occurring earlier in life. A related cross-sectional seroprevalence survey has shown that rural Aboriginal people across all age groups have a significantly higher seropositive rate than urban non-Aboriginal residents.

Experimental infection of Aedes aegypti (Diptera: Culicidae) by the oral route with Sindbis virus.

The infectivity, dissemination, and transmissibility of wild-type Sindbis (SIN) virus were studied in Aedes aegypti (L). There was an initial decline in the viral titer of whole mosquitoes for 3 d after ingestion of virus, followed by a gradual increase to a maximal level by day 6. Immunoperoxidase staining of Ae. aegypti for viral antigen showed infection of midgut epithelial cells on day 1, of the fat body by day 3, and of the brain by day 4. By day 5, there was infection of the foregut, hindgut, Malpighian tubules, ovariole sheaths, Johnston's organ, thoracic ganglia, ventral nerve cord, and salivary glands. Viral antigen was not detected in the flight muscles and was found only in ovariole sheaths of the ovaries; germinal tissue was not infected. The transmission rate from SIN-infected Ae. aegypti to neonatal mice was 40%. A comparison of Ae. aegypti infected with SIN and with a neuroadapted strain of Sindbis virus (NSIN), which is more neurovirulent than SIN to mice after intracerebral inoculation, did not reveal significant differences in infectivity, dissemination, or transmissibility. The important differences between SIN and NSIN in a mouse model were not reflected in the infection of Ae. aegypti by the oral route.

Transovarial transmission of chikungunya virus by Aedes albopictus mosquitoes ingesting microfilariae of Dirofilaria immitis under laboratory conditions.

Female Aedes albopictus mosquitoes of the Miki strain were experimentally fed on defibrinated sheep blood containing 5 x 10(7) PFU of chikungunya virus and 20,000 microfilariae of Dirofilaria immitis per milliliter. Fully engorged mosquitoes transmitted the virus to a small percentage of the F1 progeny, but females of the F1 generation did not transmit the virus to the F2 progeny. The control mosquitoes that ingested the virus without microfilariae did not transmit the virus to their eggs, larvae, or pupae in the F1 or F2 generations. These results showed that A. albopictus of this strain that concurrently ingested the virus and microfilariae transmitted the virus by the transovarial route under experimental conditions.

Isolation of Getah virus from mosquitos collected on Hainan Island, China, and results of a serosurvey.

An isolate of Getah virus was obtained from Culex mosquitos collected in Mao'an Village, Baoting County, Hainan Province, China, in 1964. The virus (strain M-1) replicated in laboratory-bred Aedes aegypti and Cx. fatigans (= quinquefasciatus), and was transmitted by laboratory-bred Ae. albopictus to healthy newborn albino mice. Skeletal muscles of newborn albino mice experimentally infected with the virus showed degeneration, atrophy, necrosis, and inflammatory changes of muscle fibers. Antibody prevalence in humans and animals ranged from 10.3% by neutralization tests of samples from healthy people in 1979 to 26.4% by CF tests of samples from people with febrile illnesses in 1982. The high prevalence of antibody in pigs, horses, and goats (17.6% to 37.5%) indicated that infection with Getah or a closely related virus is relatively common in domestic animals.

Virus-dependent mortality in Rift Valley fever, eastern equine encephalomyelitis, and chikungunya virus-inoculated mosquito (Diptera: Culicidae) larvae.

The effect of inoculation of mosquito larvae with Rift Valley fever (RVF) virus on survival to the adult stage was evaluated in Aedes aegypti (L.), Ae. fowleri (Charmoy), Ae. mcintoshi Huang, Ae. taeniorhynchus (Wiedemann), Ae. triseriatus (Say), Eretmapodites quinquevittatus Theobald, Anopheles albimanus Wiedemann, and Culex pipiens L. Pupation rates were similar for RVF virus-inoculated and diluent-inoculated larvae of all mosquito species tested except Cx. pipiens. However, with the exception of An. albimanus and Ae. triseriatus, virtually all pupae derived from RVF virus-inoculated larvae failed to emerge successfully as adults. In contrast, both pupation and emergence rates were similar for diluent-inoculated and either La Crosse or St. Louis encephalitis virus-inoculated larvae of Ae. taeniorhynchus. There was also poor survival to the adult stage of Ae. taeniorhynchus inoculated with either eastern equine encephalomyelitis (EEE) or chikungunya (CHIK) virus. The high mortality rates observed under laboratory conditions of pupae derived from larvae inoculated with either RVF, EEE, or CHIK virus may be responsible for the lack of laboratory confirmation of vertical transmission of these viruses.

Limited potential for mosquito transmission of a live, attenuated chikungunya virus vaccine.

Studies were conducted to determine the potential for transmission of a live, attenuated chikungunya (CHIK) virus vaccine by orally exposed or virus-inoculated mosquitoes. The vaccine (CHIK 181/clone 25) replicated in and was transmitted by female Aedes albopictus and Ae. aegypti after intrathoracic inoculation. Mosquitoes also became infected with the vaccine after ingesting virus from either a blood-soaked cotton pledget or a viremic monkey. However, because of the low viremias produced in inoculated humans, it is unlikely that mosquitoes would become infected by feeding on a person inoculated with the live, attenuated CHIK vaccine. Although the vaccine was transmitted by mosquitoes after intrathoracic inoculation, there was no evidence of reversion to a virulent phenotype.

Dispersal of adult females of Culex annulirostris in Griffith, New South Wales, Australia.

The dispersal of Culex annulirostris, a major arbovirus vector in Australia, was studied in Griffith, N.S.W. using a mark-release-recapture technique. From an empirical model of dispersal, fitted to data on recaptured adults, the average distance dispersed was 6.8 km (95% c.l. 4.1-40.9 km), and 50% of the population dispersed 4.8 km or more. Maximum recorded dispersal was 8.7 km, and 2 individuals traveled more than 5 km in 1 day. The relevance of the findings to control strategy is discussed.

Susceptibility of selected strains of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) to chikungunya virus.

The relative susceptibility of selected strains of Aedes aegypti (L.) and Aedes albopictus (Skuse) fed on a viremic monkey to infection with chikungunya virus was determined. Infection rates were consistently higher in 10 strains of Ae. albopictus tested than in 7 strains of Ae. aegypti tested, regardless of the geographic location from which the strains originated or the dose of virus ingested. Similarly, virus dissemination rates were higher in the Ae. albopictus strains compared with the Ae. aegypti strains. For nearly all (11 of 12) strains tested of both species, groups of mosquitoes with one or more females with a disseminated infection transmitted virus by bite to weanling mice. Based on these studies, Ae. albopictus appears to be a more competent laboratory vector of chikungunya virus than does Ae. aegypti.