Disseminated Infection Rates Research Articles

Low humidity enhances Zika virus infection and dissemination in Aedes aegypti mosquitoes.

As climate change alters Earth's biomes, it is expected the transmission dynamics of mosquito-borne viruses will change. While the effects of temperature changes on mosquito-virus interactions and the spread of the pathogens have been elucidated over the last decade, the impact of relative humidity changes is still relatively unknown. To overcome this knowledge gap, we exposed Aedes aegypti females to various humidity conditions. We measured different components of vectorial capacity such as survival, blood-feeding rates, and changes in infection and dissemination of Zika virus. Survival decreased as the humidity level decreased, while infection rates increased as the humidity level decreased. Alternatively, blood feeding rates and disseminated infection rates peaked at the intermediate 50% relative humidity treatment but were the same in the 30% and 80% relative humidity treatments. These results provide empirical evidence that Ae. aegypti exposure to low humidity can enhance Zika virus infection in the mosquito, which has important implications in predicting how climate change will impact mosquito-borne viruses.IMPORTANCEViruses transmitted by mosquitoes to humans are a major public health burden and are expected to increase under climate change. While we know that temperature is an important driver of variation in arbovirus replication in the mosquito, very little is known about how other relevant climate variables such as humidity will influence the interaction between mosquitoes and the viruses they transmit. Given the variability in humidity across environments, and the predicted changes in humidity under climate change, it is imperative that we also study the impact that it has on mosquito infection and transmission of arboviruses.

FACTORS ASSOCIATED WITH DISSEMINATION AND COMPLICATIONS OF ACUTE BONE AND JOINT INFECTIONS IN CHILDREN

Paediatric bone and joint infections remain common in low- and middle-income countries (LMICs). We aimed to determine the complication rate and incidence of disseminated infection in paediatric bone and joint infections in an LMIC setting. Secondly, we aimed to elucidate factors associated with complications and disseminated disease.We retrospectively reviewed our database for children that presented with bone and joint infections between September 2015 and March 2019. Data were extracted to identify factors that were associated with development of complications and disseminated infection.We analysed 49 children. The median age at presentation was 6 years (range 1 month to 12 years). Locally advanced disease was present in 13 children (27%). The remaining 36 children were evenly divided (18/49 each, 37%) between isolated AHOM and SA, respectively. Disseminated disease was present in 16 children (33%) and was associated with locally advanced disease, an increase in number of surgeries and an increased length of stay. Twenty-six complications were documented in 22 (45%) children. Chronic osteomyelitis developed in 15/49 (31%) cases, growth arrest in 5/49 (10%), and pathological fracture, DVT and septic shock in 2/49 (4%) each. Complicated disease was associated with locally advanced disease, a higher number of surgeries, disseminated disease and an increased length of stay. Sixty five percent of cases cultured Staphylococcus aureus, while 25% (12/49) were culture negative. The median time from admission to surgery was one day, and the median time from onset of symptoms to surgery was seven days.We found a high complication rate. One third of patients had locally advanced disease, and this was associated with the development of complications and disseminated disease. Further studies are needed to be able to predict which children will have poor outcomes.

Vector Competence for Zika Virus Changes Depending on the Aedes aegypti's Region of Origin in Manaus: A Study of an Endemic Brazilian Amazonian City.

Zika virus (ZIKV) is transmitted to humans by the infectious bite of mosquitoes such as Aedes aegypti. In a city, the population control of mosquitoes is carried out according to alerts generated by different districts via the analysis of the mosquito index. However, we do not know whether, besides mosquito abundance, the susceptibility of mosquitoes could also diverge among districts and thus impact the dissemination and transmission of arboviruses. After a viremic blood meal, the virus must infect the midgut, disseminate to tissues, and reach the salivary gland to be transmitted to a vertebrate host. This study evaluated the patterns of ZIKV infection in the Ae. aegypti field populations of a city. The disseminated infection rate, viral transmission rate, and transmission efficiency were measured using quantitative PCR at 14 days post-infection. The results showed that all Ae. aegypti populations had individuals susceptible to ZIKV infection and able to transmit the virus. The infection parameters showed that the geographical area of origin of the Ae. aegypti influences its vector competence for ZIKV transmission.

Factors associated with dissemination and complications of acute bone and joint infections in children

BACKGROUND: Paediatric bone and joint infections remain common in low- and middle-income countries (LMICs) and may have devastating long-term sequelae. There is a paucity of data from LMICs where the true incidence might be underreported, and delayed presentation is common. Our study aimed to determine the complication rate and incidence of disseminated infection in paediatric bone and joint infections in an LMIC setting. Secondly, we aimed to elucidate factors associated with complications and disseminated disease METHODS: We retrospectively reviewed our paediatric orthopaedic database for children that presented with bone and joint infections between September 2015 and March 2019. Data were extracted from medical records, laboratory results and radiological investigations to identify factors that were associated with the development of complications and disseminated infection at a median follow-up of four months RESULTS: We analysed 49 children. The median age at presentation was 6 years (range 1 month to 12 years). Locally advanced disease, with combined acute haematogenous osteomyelitis (AHOM) and septic arthritis (SA), was present in 13 children (27%). The remaining 36 children were evenly divided (18/49 each, 37%) between isolated AHOM and SA, respectively. Disseminated disease was present in 16 children (33%) and was associated with locally advanced disease, an increase in the number of surgeries and an increased length of stay. Twenty-six complications were documented in 22 (45%) children. Chronic osteomyelitis developed in 15/49 (31%) cases, growth arrest in 5/49 (10%), and pathological fracture, DVT and septic shock in 2/49 (4%) each. Complicated disease was associated with locally advanced disease, a higher number of surgeries, disseminated disease and an increased length of stay. Staphylococcus aureus was the infecting pathogen in 65% of cases (31 MSSA, 1 MRSA), while 25% (12/49) were culture-negative infections. While the median time from admission to surgery was one day, the median time from onset of symptoms to surgery was seven days CONCLUSION: We found a high complication rate despite a short follow-up period. More than a quarter of patients had locally advanced disease, and this was associated with the development of complications and disseminated disease. Further studies are needed to be able to predict which children will have poor outcomes Level of evidence: Level 4

Brazilian Aedes aegypti as a Competent Vector for Multiple Complex Arboviral Coinfections.

Aedes aegypti is a highly competent vector in the transmission of arboviruses, such as chikungunya, dengue, Zika, and yellow fever viruses, and causes single and coinfections in the populations of tropical countries. The infection rate, viral abundance (VA), vector competence (VC), disseminated infection, and survival rate were recorded after single and multiple infections of the vector with 15 combinations of chikungunya, dengue, Zika, and yellow fever arboviruses. Infection rates were 100% in all single and multiple infection experiments, except in 1 triple coinfection that presented a rate of 50%. The VC and disseminated infection rate varied from 100% (in single and quadruple infections) to 40% (in dual and triple infections). The dual and triple coinfections altered the VC and/or VA of ≥1 arbovirus. The highest viral VAs were detected for a single infection with chikungunya. The VAs in quadruple infections were similar when compared with each respective single infection. A decrease in survival rates was observed in a few combinations. A. aegypti was able to host all single and multiple arboviral coinfections. The interference of the chikungunya virus suggests that distinct arbovirus families may have a significant role in complex coinfections.

Effects of Ascogregarina culicis (Eugregarinorida: Lecudinidae) on Mosquito Size and Dengue Virus Infection in Aedes aegypti (Diptera: Culicidae).

Dengue virus infection, transmitted via mosquito bites, poses a substantial risk to global public health. Studies suggest that the mosquito's microbial community can profoundly influence vector-borne pathogen transmissions, including dengue virus. Ascogregarina culicis (Ross) of the phylum Apicomplexa is among the most common parasites of Aedes aegypti (Linnaeus), the principal vector of dengue. Despite a high prevalence worldwide, including in the areas where dengue is endemic, the impact of A. culicis on Ae. aegypti vector competence for dengue virus is unknown. This study aimed to investigate the effects of A. culicis infection on mosquito size and fitness, as measured by wing length, and the susceptibility to dengue virus infection in Ae. aegypti. Our results showed that there was no statistically significant difference in wing lengths between Ae. aegypti infected and not infected with A. culicis. Furthermore, A. culicis infection did not significantly affect dengue virus infection or disseminated infection rate. However, there was a significant association between shorter wings and higher dengue virus infection rate, whereby a 0.1-mm increase in wing length decreased the odds of the mosquito being infected by 32%. Thus, based on our result, A. culicis infection does not influence the body size and dengue virus infection in Ae. aegypti. This study helps to shed light on a common but neglected eukaryotic mosquito parasite.

Clinical features of children with immunodeficiency and Mycobacterium tuberculosis infection

OBJECTIVE To study the clinical features of Mycobacterium tuberculosis infection in children with secondary immunodeficiency disease (SID) versus primary immunodeficiency disease (PID). METHODS A retrospective analysis was performed on the medical data of children with immunodeficiency and Mycobacterium tuberculosis infection (36 children with SID and 52 with PID) and 108 children with Mycobacterium tuberculosis infection but without immunodeficiency (control group). RESULTS The onset age in the PID group was significantly lower than those in the control and SID groups (P < 0.05), and the proportation of males in the PID group was significantly higher than those in the control and SID groups (P < 0.05). Compared with the control group, the SID and PID groups had significantly lower incidence rates of tuberculosis poisoning symptoms (night sweeting, weight loss, fatigue and loss of appetite) and positive rate of PPD test (P < 0.05), as well as a significantly higher incidence rate of the involvement of ≥ 3 pulmonary lobes (P < 0.05). The children with PID tended to have the involvement of multiple organs (P < 0.05). The SID group had a significantly higher incidence rate of miliary shadow on chest CT than the control and PID groups (P < 0.05). The PID group had a significantly lower positive rate of IFN-gamma release assay (IGRA) than the control and SID groups (P < 0.05). Mycobacterium tuberculosis infection manifested as latent tuberculosis infection (36.1%) and active tuberculosis (63.9%) in the SID group. The infection mainly manifested as bacille Calmette-Guerin disease in the PID group (90.4%), among whom 2 children (3.8%) also had tuberculosis. CONCLUSIONS Children with immunodeficiency and Mycobacterium tuberculosis infection have atypical clinical symptoms, with a high incidence rate of disseminated infection and low positive rates of PPD and IGRA tests, which may lead to misdiagnosis and missed diagnosis. Children with immunodeficiency should undergo regular tuberculosis screening for early identification and intervention.

Severe Infectious Complications of Intravesical Bacillus Calmette-Guérin: A Case Series of 10 Patients

ObjectiveTo investigate severe infectious complications after intravesical treatment with bacillus Calmette-Guérin (BCG). We examine a retrospective case series of 10 patients between 2006 and 2018 with severe cystitis or systemic infection after BCG. MethodsPatients with BCG cystitis or disseminated infection were retrospectively identified between 2006 and 2018 at our institution. Cases were reviewed for bladder cancer treatments, demographics, treatment of infection, and outcomes. ResultsThere was a 0.8% rate of severe BCG cystitis or disseminated infection. Seven patients experienced delayed-onset infections >3 months after last BCG instillation. Four had isolated bladder symptoms, and 5 had diverse systemic manifestations. One patient was asymptomatic and diagnosed on cystoscopic findings. All were treated with varied antibiotic regimens; 9 included antituberculous therapy, and 1 was treated with levofloxacin alone. Two underwent cystectomy for end-stage bladder. The remaining patients are asymptomatic with no residual effects. All are in remission for bladder cancer. ConclusionSevere infectious complications after BCG are rare and thus difficult to study. Treatment regimens can vary widely. Thorough reporting of patient outcomes is essential to expand the limited body of knowledge.

Vector competence of Australian Aedes aegypti and Aedes albopictus for an epidemic strain of Zika virus.

BackgroundRecent epidemics of Zika virus (ZIKV) in the Pacific and the Americas have highlighted its potential as an emerging pathogen of global importance. Both Aedes (Ae.) aegypti and Ae. albopictus are known to transmit ZIKV but variable vector competence has been observed between mosquito populations from different geographical regions and different virus strains. Since Australia remains at risk of ZIKV introduction, we evaluated the vector competence of local Ae. aegypti and Ae. albopictus for a Brazilian epidemic ZIKV strain. In addition, we evaluated the impact of daily temperature fluctuations around a mean of 28°C on ZIKV transmission and extrinsic incubation period.Methodology/Principal findingsMosquitoes were orally challenged with a Brazilian ZIKV strain (8.8 log CCID50/ml) and maintained at either 28°C constant or fluctuating temperature conditions. At 3, 7 and 14 days post-infection (dpi), ZIKV RNA copies were quantified in mosquito bodies, as well as wings and legs, using qRT-PCR, while virus antigen in saliva (a proxy for transmission) was detected using a cell culture ELISA. Despite high body and disseminated infection rates in both vectors, the transmission rates of ZIKV in saliva of Ae. aegypti (50–60%) were significantly higher than in Ae. albopictus (10%) at 14 dpi. Both species supported a high viral load in bodies, with no significant differences between constant and fluctuating temperature conditions. However, a significant difference in viral load in wings and legs between species was observed, with higher titres in Ae. aegypti maintained at constant temperature conditions. For ZIKV transmission to occur in Ae. aegypti, a disseminated virus load threshold of 7.59 log10 copies had to be reached.Conclusions/SignificanceAustralian Ae. aegypti are better able to transmit a Brazilian ZIKV strain than Ae. albopictus. The results are in agreement with the global consensus that Ae. aegypti is the major vector of ZIKV.

Potential for sylvatic and urban Aedes mosquitoes from Senegal to transmit the new emerging dengue serotypes 1, 3 and 4 in West Africa.

Dengue fever (DEN) is the most common arboviral disease in the world and dengue virus (DENV) causes 390 million annual infections around the world, of which 240 million are inapparent and 96 million are symptomatic. During the past decade a changing epidemiological pattern has been observed in Africa, with DEN outbreaks reported in all regions. In Senegal, all DENV serotypes have been reported. These important changes in the epidemiological profile of DEN are occurring in a context where there is no qualified vaccine against DEN. Further there is significant gap of knowledge on the vector bionomics and transmission dynamics in the African region to effectively prevent and control epidemics. Except for DENV-2, few studies have been performed with serotypes 1, 3, and 4, so this study was undertaken to fill out this gap. We assessed the vector competence of Aedes (Diceromyia) furcifer, Ae. (Diceromyia) taylori, Ae. (Stegomyia) luteocephalus, sylvatic and urban Ae. (Stegomyia) aegypti populations from Senegal for DENV-1, DENV-3 and DENV-4 using experimental oral infection. Whole bodies and wings/legs were tested for DENV presence by cell culture assays and saliva samples were tested by real time RT-PCR to estimate infection, disseminated infection and transmission rates. Our results revealed a low capacity of sylvatic and urban Aedes mosquitoes from Senegal to transmit DENV-1, DENV-3 and DENV-4 and an impact of infection on their mortality. The highest potential transmission rate was 20% despite the high susceptibility and disseminated infection rates up to 93.7% for the 3 Ae. aegypti populations tested, and 84.6% for the sylvatic vectors Ae. furcifer, Ae. taylori and Ae. luteocephalus.

Analysis of Salivary Glands and Saliva from Aedes albopictus and Aedes aegypti Infected with Chikungunya Viruses.

Chikungunya virus (CHIKV) is a medically important mosquito-borne virus transmitted to humans by infected Aedes (Stegomyia) species. In 2013–2014, Ae. aegypti transmitted CHIKV to humans in the Caribbean and in 2005–2006, Ae. albopictus transmitted CHIKV on La Réunion Island (Indian Ocean basin). CHIKV LR2006 OPY1 from the La Réunion epidemic was associated with a mutation (E1:A226V) in the viral E1 glycoprotein that enhanced CHIKV transmission by Ae. albopictus. CHIKV R99659 from the Caribbean outbreak did not have the E1:A226V mutation. Here, we analyzed the salivary glands and saliva of Ae. albopictus strains from New Jersey, Florida, Louisiana and La Réunion after infection with each virus to determine their transmission potential. We infected the Ae. albopictus strains with blood meals containing 3–7 × 107 PFU/mL of each virus and analyzed the mosquitoes nine days later to maximize infection of their salivary glands. All four Ae. albopictus strains were highly susceptible to LR2006 OPY1 and R99659 viruses and their CHIKV disseminated infection rates (DIR) were statistically similar (p = 0.3916). The transmission efficiency rate (TER) was significantly lower for R99659 virus compared to LR2006 OPY1 virus in all Ae. albopictus strains and Ae. aegypti (Poza Rica) (p = 0.012) suggesting a salivary gland exit barrier to R99659 virus not seen with LR2006 OPY1 infections. If introduced, LR2006 OPY1 virus poses an increased risk of transmission by both Aedes species in the western hemisphere.

Vector competence of Culex antennatus and Anopheles coustani mosquitoes for Rift Valley fever virus in Madagascar.

Culex antennatus (Diptera: Culicidae), Anopheles coustani (Diptera: Culicidae) and Anopheles squamosus/cydippis were found to be infected with Rift Valley fever virus (RVFV) during an epidemic that occurred in 2008 and 2009 in Madagascar. To understand the roles played by Cx. antennatus and An. coustani in virus maintenance and transmission, RVFV vector competence was assessed in each species. Mosquito body parts and saliva of mosquitoes that fed on RVFV-infected blood were tested for RVFV using real-time quantitative polymerase chain reaction (RT-qPCR) assays. Overall, viral RNA was detected in body parts and saliva at 5 days post-infection (d.p.i.) in both species. At 5 d.p.i., infection rates were 12.5% (3/24) and 15.8% (6/38), disseminated infection rates were 100% (3/3) and 100% (6/6), transmission rates were 33.3% (1/3) and 83.3% (5/6), and transmission efficiencies were 4.2% (1/24) and 13.2% (5/38) in Cx. antennatus and An. coustani, respectively. Although RVFV detected in saliva did not propagate on to Vero cells, these results support potential roles for these two mosquito species in the transmission of RVFV.

Zika Virus, a New Threat for Europe?

BackgroundSince its emergence in 2007 in Micronesia and Polynesia, the arthropod-borne flavivirus Zika virus (ZIKV) has spread in the Americas and the Caribbean, following first detection in Brazil in May 2015. The risk of ZIKV emergence in Europe increases as imported cases are repeatedly reported. Together with chikungunya virus (CHIKV) and dengue virus (DENV), ZIKV is transmitted by Aedes mosquitoes. Any countries where these mosquitoes are present could be potential sites for future ZIKV outbreak. We assessed the vector competence of European Aedes mosquitoes (Aedes aegypti and Aedes albopictus) for the currently circulating Asian genotype of ZIKV.Methodology/Principal FindingsTwo populations of Ae. aegypti from the island of Madeira (Funchal and Paul do Mar) and two populations of Ae. albopictus from France (Nice and Bar-sur-Loup) were challenged with an Asian genotype of ZIKV isolated from a patient in April 2014 in New Caledonia. Fully engorged mosquitoes were then maintained in insectary conditions (28°±1°C, 16h:8h light:dark cycle and 80% humidity). 16–24 mosquitoes from each population were examined at 3, 6, 9 and 14 days post-infection to estimate the infection rate, disseminated infection rate and transmission efficiency. Based on these experimental infections, we demonstrated that Ae. albopictus from France were not very susceptible to ZIKV.Conclusions/SignificanceIn combination with the restricted distribution of European Ae. albopictus, our results on vector competence corroborate the low risk for ZIKV to expand into most parts of Europe with the possible exception of the warmest regions bordering the Mediterranean coastline.

Vector competence of Aedes aegypti in transmitting Chikungunya virus: effects and implications of extrinsic incubation temperature on dissemination and infection rates.

BackgroundAedes aegypti is a competent arthropod vector of chikungunya virus (CHIKV). The rate at which the virus disseminate in the vector is limited by temperature of their environment which can be an important determinant of geographical and seasonal limits to transmission by the arthropods in the tropics. This study investigated the vector competence of Ae. aegypti for CHIKV at ambient temperature of 32 and 26 °C (Coastal and Western Kenya respectively) reared at Extrinsic Incubation Temperature (EIT) of 32 and 26 °C that resembles those in the two regions.MethodsAe. aegypti eggs were collected from coastal and Western Kenya, hatched in the insectary and reared to F1 generation. Four-day old mosquitoes were exposed to CHIKV through a membrane feeding. They were then incubated in temperatures mimicking the mean annual temperatures for Trans-Nzoia (26 °C) and Lamu (32 °C). After every 7, 10 and 13 days post infection (DPI); one third of exposed mosquitoes were sampled and assayed for virus infection and dissemination.ResultsThe midgut infection rates (MIR) of Ae. aegypti sampled from Coastal Region was significantly (p < 0.05) higher than those sampled from Western Kenya, with no statistical differences observed for the coastal Ae. aegypti at EIT 26 and at 32 °C. The MIR of Ae. aegypti from the Western Region was significantly (p < 0.05) affected by the EIT, with mosquito reared at EIT 32 °C exhibiting higher MIR than those reared at EIT 26 °C. There was a significant (p < 0.05) interactive effects of the region, EIT and DPI on MIR. The disseminated infection rates for the CHIKV in Ae. aegypti in the legs (DIR-L) was higher in mosquitoes sampled from Coast regardless of the EIT while those from Western Kenya, dissemination rates were significantly higher at higher EIT of 32 °C.ConclusionsVector competence was higher in mosquito populations reared under high temperatures which weakens the midgut infection barrier. Hence, suggesting Lamu population is more susceptible to CHIKV therefore having a weaker mid gut infection barrier than the Trans Nzoia population. These underscores importance of examining the course of infection at various ambient temperatures and EIT between regions mosquito populations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0566-7) contains supplementary material, which is available to authorized users.

Differential Susceptibilities of Aedes aegypti and Aedes albopictus from the Americas to Zika Virus.

BackgroundSince the major outbreak in 2007 in the Yap Island, Zika virus (ZIKV) causing dengue-like syndromes has affected multiple islands of the South Pacific region. In May 2015, the virus was detected in Brazil and then spread through South and Central America. In December 2015, ZIKV was detected in French Guiana and Martinique. The aim of the study was to evaluate the vector competence of the mosquito spp. Aedes aegypti and Aedes albopictus from the Caribbean (Martinique, Guadeloupe), North America (southern United States), South America (Brazil, French Guiana) for the currently circulating Asian genotype of ZIKV isolated from a patient in April 2014 in New Caledonia.Methodology/Principal FindingsMosquitoes were orally exposed to an Asian genotype of ZIKV (NC-2014-5132). Upon exposure, engorged mosquitoes were maintained at 28°±1°C, a 16h:8h light:dark cycle and 80% humidity. 25–30 mosquitoes were processed at 4, 7 and 14 days post-infection (dpi). Mosquito bodies (thorax and abdomen), heads and saliva were analyzed to measure infection, dissemination and transmission, respectively. High infection but lower disseminated infection and transmission rates were observed for both Ae. aegypti and Ae. albopictus. Ae. aegypti populations from Guadeloupe and French Guiana exhibited a higher dissemination of ZIKV than the other Ae. aegypti populations examined. Transmission of ZIKV was observed in both mosquito species at 14 dpi but at a low level.Conclusions/SignificanceThis study suggests that although susceptible to infection, Ae. aegypti and Ae. albopictus were unexpectedly low competent vectors for ZIKV. This may suggest that other factors such as the large naïve population for ZIKV and the high densities of human-biting mosquitoes contribute to the rapid spread of ZIKV during the current outbreak.

How do Nutritional Stress and La Crosse Virus Infection Interact? Tests for Effects on Willingness to Blood Feed and Fecundity in Aedes albopictus (Diptera: Culicidae).

Evolutionary theory predicts that vector-borne pathogens should have low virulence for their vector because of selection against pathogens that harm the vector sufficiently to reduce transmission. Environmental factors such as nutritional stress can alter vector-pathogen associations by making the vectors more susceptible to pathogens (condition-dependent competence) and vulnerable to the harm caused by pathogen replication (condition-dependent virulence). We tested the hypotheses of condition-dependent competence and condition-dependent virulence by examining the interactive effects of short-term sugar deprivation and exposure to La Crosse virus (LACV) in female Aedes albopictus (Skuse). We predicted that infection status interacts with sugar deprivation to alter willingness to blood feed and fecundity in the second gonotrophic cycle (condition-dependent virulence). Sugar deprivation had no effect on body infection or disseminated infection rates. Infection status, sugar treatment, and their interaction had no effect on fecundity. Mosquitoes that had intermittent access to sugar were significantly more willing to take a second bloodmeal compared with those that had continuous access to sugar. Infection status and the interaction with sugar treatment had no effect on blood-feeding behavior. Thus, we found no evidence of short-term sugar deprivation leading to condition-dependent competence for, or condition-dependent virulence of, LACV in Ae. albopictus.

Container Type Influences the Relative Abundance, Body Size, and Susceptibility of Ochlerotatus triseriatus (Diptera: Culicidae) to La Crosse Virus.

Ochlerotatus triseriatus (Say), the primary vector of La Crosse virus (LAC), develops in a variety of natural and artificial aquatic containers where it often co-occurs with larvae of other mosquito species. We conducted a field study at two woodlots (South Farms and Trelease Woods) in Urbana, IL, to examine how container type influences vector abundance, body size, and susceptibility to LAC. Mosquito pupae were collected from tree holes, plastic bins, and waste tires, and eclosing adults were identified to species morphologically. Oc. triseriatus and Ochlerotatus japonicus (Theobald) females were orally challenged with LAC and midgut infection rate, disseminated infection rate, and body titer were determined by reverse-transcriptase real-time PCR. Oc. triseriatus was the dominant species collected in tree holes while Oc. japonicus and Culex restuans (Theobald) were mostly dominant in artificial containers. Female Oc. triseriatus and Oc. japonicus collected from plastic bins were significantly larger than those collected from tree holes or waste tires. Oc. japonicus females from South Farms were also significantly larger than those from Trelease Woods. Oc. triseriatus females collected from plastic bins and waste tires were significantly more susceptible to LAC infection relative to females collected from tree holes. In addition, Oc. triseriatus females from waste tires had significantly higher LAC titer relative to Oc. triseriatus from tree holes. For each container type and study site, wing length was not correlated to infection or dissemination rates. These findings suggest that the container type in which Oc.triseriatus develop may contribute to the spatial and temporal dynamics of LAC transmission.

Distinct variation in vector competence among nine field populations of Aedes aegypti from a Brazilian dengue-endemic risk city.

BackgroundIn Brazil, dengue epidemics erupt sporadically throughout the country and it is unclear if outbreaks may initiate a sustainable transmission cycle. There are few studies evaluating the ability of Brazilian Aedes aegypti populations to transmit dengue virus (DENV). The aim of this study was to compare DENV susceptibility of field-captured Ae. aegypti populations from nine distinct geographic areas of the city of Belo Horizonte in 2009 and 2011. Infection Rate (IR), Vector Competence (VC) and Disseminated Infection Rate (DIR) were determined.MethodsAedes aegypti eggs from each region were collected and reared separately in an insectary. Adult females were experimentally infected with DENV-2 and the virus was detected by qPCR in body and head samples. Data were analyzed with the Statistical Package for the Social Sciences version 17.ResultsIR varied from 40.0% to 82.5% in 2009 and 60.0% to 100.0% in 2011. VC ranged from 25.0% to 77.5% in 2009 and 25.0% to 80.0% in 2011. DIR oscillated from 68.7% to 100.0% in 2009 and 38.4% to 86.8 in 2011. When the results were evaluated by a logistic model using IR as covariate, North, Barreiro, South-Central and Venda Nova showed the strongest association in 2009. In 2011, a similar association was observed for South-Central, Venda Nova, West and Northeast regions. Using VC as covariate, South-Central and Venda Nova showed the most relevant association in 2009. In 2011, South-Central, Venda Nova and Barreiro presented the greatest revelation associations. When DIR data were analyzed by logistic regression models, Pampulha, South-Central, Venda Nova, West, Northeast and East (2009) as well as South-Central, Venda Nova and West (2011) were the districts showing the strongest associations.ConclusionsWe conclude that Ae. aegypti populations from Belo Horizonte exhibit wide variation in vector competence to transmit dengue. Therefore, vector control strategies should be adapted to the available data for each region. Further analysis should be conducted to better understand the reasons for this large variability in vector competence and how these parameters correlate with epidemiological findings in subsequent years.

Role of Bunyamwera Orthobunyavirus NSs Protein in Infection of Mosquito Cells

BackgroundBunyamwera orthobunyavirus is both the prototype and study model of the Bunyaviridae family. The viral NSs protein seems to contribute to the different outcomes of infection in mammalian and mosquito cell lines. However, only limited information is available on the growth of Bunyamwera virus in cultured mosquito cells other than the Aedes albopictus C6/36 line.Methodology and Principal FindingsTo determine potential functions of the NSs protein in mosquito cells, replication of wild-type virus and a recombinant NSs deletion mutant was compared in Ae. albopictus C6/36, C7-10 and U4.4 cells, and in Ae. aegypti Ae cells by monitoring N protein production and virus yields at various times post infection. Both viruses established persistent infections, with the exception of NSs deletion mutant in U4.4 cells. The NSs protein was nonessential for growth in C6/36 and C7-10 cells, but was important for productive replication in U4.4 and Ae cells. Fluorescence microscopy studies using recombinant viruses expressing green fluorescent protein allowed observation of three stages of infection, early, acute and late, during which infected cells underwent morphological changes. In the absence of NSs, these changes were less pronounced. An RNAi response efficiently reduced virus replication in U4.4 cells transfected with virus specific dsRNA, but not in C6/36 or C7/10 cells. Lastly, Ae. aegypti mosquitoes were exposed to blood-meal containing either wild-type or NSs deletion virus, and at various times post-feeding, infection and disseminated infection rates were measured. Compared to wild-type virus, infection rates by the mutant virus were lower and more variable. If the NSs deletion virus was able to establish infection, it was detected in salivary glands at 6 days post-infection, 3 days later than wild-type virus.Conclusions/SignificanceBunyamwera virus NSs is required for efficient replication in certain mosquito cell lines and in Ae. aegypti mosquitoes.

Does the presence of mediastinal adenopathy confer a risk for disseminated infection in immunocompetent persons with pulmonary coccidioidomycosis?

Pulmonary coccidioidomycosis is caused by inhaling airborne arthroconidia of Coccidioides, a soil-dwelling fungus endemic to the desert southwestern United States. Although uncommon, disseminated coccidioidal infection can be associated with well-defined risk factors, such as cell-mediated immunodeficiency, certain racial heritages (e.g. African or Filipino), male sex, or pregnancy. Before widespread use of computed tomography (CT), the presence or persistence of mediastinal lymphadenopathy was postulated to be a risk factor for disseminated coccidioidal infection. To investigate the use of CT scanning to identify the presence of mediastinal lymphadenopathy in patients with pulmonary coccidioidomycosis, and to correlate such lymphadenopathy with disseminated coccidioidal infection, we performed a retrospective review of patients with pulmonary coccidioidomycosis who were evaluated by chest CT. Two radiologists independently interpreted 150 CT scans from patients with pulmonary coccidioidomycosis. Forty-nine patients met CT criteria for mediastinal lymphadenopathy, whereas 101 patients did not. Disseminated coccidioidal infection was observed in 5 (10%) of the 49 patients with mediastinal lymphadenopathy and in 6 of the 101 (6%; P = .34) without such adenopathy. Among patients with coccidioidomycosis, patients with mediastinal lymphadenopathy, as assessed by CT, had a higher rate of disseminated infection, but the difference was not statistically significant.