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Mosquito-Borne Viral Infections in the Krasnodar Territory ~ Risks of Autochthonous Cases of the Disease
Abstract
Introduction . Global climate changes affect the habitats of insects, including mosquitoes, which are carriers of dangerous natural focal infections. When mosquitos develop new territories, they create a potential threat to people who find themselves in these areas. In the Krasnodar Region, a stable population of Ae. albopictus mosquitoes was formed in the 21st century. These mosquitoes are carriers of many viral pyrrhoid-focal infections, such as Dengue, Chikungunya, Zika fever and Yellow fever. Estimations of biological, epidemiological and cultural data can help to answer the question of the probability of occurrence of autochthonous cases of infection.
Aim . To estimate the probability of occurrence of autochthonous cases of viral infections carried by Ae. albopictus mosquitoes on the territory of the Black Sea coast of the Krasnodar territory. For the review, we used scientific publications describing the occurrence of autochthonous diseases in similar climate zones inhabited by Ae. albopictus mosquitoes, the biology of these mosquitoes, as well as official reports of the sanitary services of Europe and the Russian Federation. A stable population of Ae. albopictus mosquitoes has formed on the Black Sea coast of the Krasnodar Territory. The local climate, including the temperature range is favourable for active reproduction of vectors and autochthonous transmission of viral infection.
Conclusion . Despite the favourable conditions for the release of mosquitoes and the formation of a stable population, autochthonous transmission requires the introduction of the source of infection during the viremia period to infect the mosquito population. In recent years, isolated cases of such drifts have been reported in the Krasnodar Territory, which indicates a low probability of local cases of transmission. However, with the development of the tourism sector, the flow of tourists from endemic areas will inevitably increase. In addition, the increase in the well-being of the population, trips to these countries will become more frequent this may well increase the risk of transmission of viral infections by local mosquitoes. In any case, the weakening of epidemic control of mosquitoes and medical surveillance of imported cases of tropical fevers will have serious consequences.
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On 1 October 2019, a locally-acquired Zika virus disease case was laboratory confirmed in Hyères, Var department. Active case finding identified two additional locally-acquired cases living within 90 m, with symptom onset 8 days before the index case. Extensive patient interviews did not yield information supporting transmission through sexual contact or substances of human origin. Vector-borne transmission by local Aedes albopictus mosquitoes is the most likely mode of transmission. Here we describe the public health response.
Background:
Much work has been done in recent years to determine the vector competence of Aedes albopictus (Skuse) for Zika virus (ZIKV). If competent, Ae. albopictus could become an important vector in the spread of ZIKV to areas which until now have been considered safe from the virus. Despite much speculation about Ae. albopictus' competence for ZIKV, there have been, to date, no quantitative syntheses of Ae. albopictus' competence, nor have the potentially confounding differences between studies been addressed.
Methodology/ principle findings:
This study represents a quantitative meta-analysis of the literature surrounding this topic by examining infection rates (IR) and transmission rates (TR) among sample populations of Ae. albopictus at 7 and 14 days post infection (dpi) across 15 journal articles comprising 23 studies. Our analyses examined potentially confounding variables in the studies contained therein, including: geographic origin of viral strain or mosquito population tested, whether sympatry of the tested viral strain and mosquito population was important, and freshness of blood meal. Our results suggest 1) Ae albopictus is a competent vector for ZIKV and 2) that origin of Ae. albopictus population and origin of viral strain had significant effects on the competence of Ae. albopictus to transmit ZIKV.
Conclusions/ significance:
These results indicate a need to further explore the effects of methodology on vector competence studies and to examine in more detail the geographic variation in the competence of Ae. albopictus for ZIKV as well as the underlying causes of said variation. The ability of Ae. albopictus to carry and transmit ZIKV also points to a need to create new vector control strategies in case of a ZIKV outbreak in an area where Ae. albopictus is prominent. Finally, this study represents a potential template for future meta-analyses in the field of vector competence, where this type of study has been under-utilized despite the abundance of relevant studies.
Background:
Countries with ongoing outbreaks of Zika virus have observed a notable rise in reported cases of Guillain-Barré syndrome (GBS), with mounting evidence of a causal link between Zika virus infection and the neurological syndrome. However, the risk of GBS following a Zika virus infection is not well characterized. In this work, we used data from 11 locations with publicly available data to estimate the risk of GBS following an infection with Zika virus, as well as the location-specific incidence of infection and the number of suspect GBS cases reported per infection.
Methods:
We built a mathematical inference framework utilizing data from 11 locations that had reported suspect Zika and GBS cases, two with completed outbreaks prior to 2015 (French Polynesia and Yap) and nine others in the Americas covering partial outbreaks and where transmission was ongoing as of early 2017.
Results:
We estimated that 2.0 (95% credible interval 0.5-4.5) reported GBS cases may occur per 10,000 Zika virus infections. The frequency of reported suspect Zika cases varied substantially and was highly uncertain, with a mean of 0.11 (95% credible interval 0.01-0.24) suspect cases reported per infection.
Conclusions:
These estimates can help efforts to prepare for the GBS cases that may occur during Zika epidemics and highlight the need to better understand the relationship between infection and the reported incidence of clinical disease.
Although numerous viruses are transmitted by mosquitoes, four have caused the most human suffering over the centuries and continuing today. These are the viruses causing yellow fever, dengue, chikungunya, and Zika fevers. Africa is clearly the ancestral home of yellow fever, chikungunya, and Zika viruses and likely the dengue virus. Several species of mosquitoes, primarily in the genusAedes, have been transmitting these viruses and their direct ancestors among African primates for millennia allowing for coadaptation among viruses, mosquitoes, and primates. One African primate (humans) and one AfricanAedesmosquito (Aedes aegypti) have escaped Africa and spread around the world. Thus it is not surprising that this native African mosquito is the most efficient vector of these native African viruses to this native African primate. This makes it likely that when the next disease-causing virus comes out of Africa,Ae. aegyptiwill be the major vector to humans.
Surveillance of Zika virus (ZIKV) infection in the European Union/European Economic Area (EU/EEA) was implemented in 2016 in response to the large outbreak reported in the Americas in 2015 associated with an increased number of infants born with microcephaly. Between June 2015 and January 2017, 21 EU/EEA countries reported 2,133 confirmed cases of ZIKV infection, of whom 106 were pregnant women. Cases infected in the Caribbean constituted 71% of reported cases. Almost all cases (99%) were most probably infected by mosquito bite during travel outside continental Europe, while only 1% were transmitted sexually. Considering that 584 imported cases were reported between May and October 2016 among residents of areas with established presence of Aedes albopictus, the absence of autochthonous vector-borne cases suggests that Ae. albopictus is not an efficient vector for ZIKV infection.
Author summary
Understanding the drivers of recent Zika, dengue, and chikungunya epidemics is a major public health priority. Temperature may play an important role because it affects virus transmission by mosquitoes, through its effects on mosquito development, survival, reproduction, and biting rates as well as the rate at which mosquitoes acquire and transmit viruses. Here, we measure the impact of temperature on transmission by two of the most common mosquito vector species for these viruses, Aedes aegypti and Ae. albopictus. We integrate data from several laboratory experiments into a mathematical model of temperature-dependent transmission, and find that transmission peaks at 26–29°C and can occur between 18–34°C. Statistically comparing model predictions with recent observed human cases of dengue, chikungunya, and Zika across the Americas suggests an important role for temperature, and supports model predictions. Using the model, we predict that most of the tropics and subtropics are suitable for transmission in many or all months of the year, but that temperate areas like most of the United States are only suitable for transmission for a few months during the summer (even if the mosquito vector is present).
Mosquitoes collected in Germany in 2016, including Culex pipiens pipiens biotype pipiens, Culex torrentium and Aedes albopictus, as well as Culex pipiens pipiens biotype molestus (in colony since 2011) were experimentally infected with Zika virus (ZIKV) at 18 °C or 27 °C. None of the Culex taxa showed vector competence for ZIKV. In contrast, Aedes albopictus were susceptible for ZIKV but only at 27 °C, with transmission rates similar to an Aedes aegypti laboratory colony tested in parallel. © 2017, European Centre for Disease Prevention and Control (ECDC). All rights reserved.
Mosquito surveillance was carried out in Batumi, Georgia, in August 2014. Aedes albopictus was
detected for the first time, which brought the number of reported mosquito species in Georgia to 32. An updated
checklist of the mosquitoes of Georgia is provided.
During summer 2016, all the conditions for local mosquito-borne transmission of Zika virus (ZIKV) are met in mainland France: a competent vector, Aedes albopictus, a large number of travellers returning from ZIKV-affected areas, and an immunologically naive population. From 1 January to 15 July 2016, 625 persons with evidence of recent ZIKV infection were reported in mainland France. We describe the surveillance system in place and control measures implemented to reduce the risk of infection. © 2016, European Centre for Disease Prevention and Control (ECDC). All rights reserved.
Background:
Since 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 findings:
Two 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/significance:
In 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.
Dengue and chikungunya are increasing global public health concerns due to their rapid geographical spread and increasing disease burden. Knowledge of the contemporary distribution of their shared vectors, Aedes aegypti and Aedes albopictus remains incomplete and is complicated by an ongoing range expansion fuelled by increased global trade and travel. Mapping the global distribution of these vectors and the geographical determinants of their ranges is essential for public health planning. Here we compile the largest contemporary database for both species and pair it with relevant environmental variables predicting their global distribution. We show Aedes distributions to be the widest ever recorded; now extensive in all continents, including North America and Europe. These maps will help define the spatial limits of current autochthonous transmission of dengue and chikungunya viruses. It is only with this kind of rigorous entomological baseline that we can hope to project future health impacts of these viruses.
Objective
To estimate the risk of microcephaly in babies born to women infected by the Zika virus during pregnancy in Brazil in an epidemic between 2015 and 2016.
Methods
We obtained data on the number of notified and confirmed microcephaly cases in each Brazilian state between November 2015 and October 2016 from the health ministry. For Pernambuco State, one of the hardest hit, weekly data were available from August 2015 to October 2016 for different definitions of microcephaly. The absolute risk of microcephaly was calculated using the average number of live births reported in each state in the corresponding time period between 2012 and 2014 and assuming two infection rates: 10% and 50%. The relative risk was estimated using the reported background frequency of microcephaly in Brazil of 1.98 per 10 000 live births.
Findings
The estimated absolute risk of a notified microcephaly case varied from 0.03 to 17.1% according to geographical area, the definition of microcephaly used and the infection rate. Assuming a 50% infection rate, there was an 18–127 fold higher probability of microcephaly in children born to mothers with infection during pregnancy compared with children born to mothers without infection during pregnancy in Pernambuco State. For a 10% infection rate, the probability was 88–635 folds higher.
Conclusion
A large variation in the estimated risk of microcephaly was found in Brazil. Research is needed into possible effect modifiers, reliable measures of Zika virus infection and clear endpoints for congenital malformations.
The yellow fever and dengue mosquito Aedes aegypti previously flourished around the Mediterranean and Black Sea for decades until the 1950s, and was responsible of large outbreaks of both yellow fever and dengue [1]. The first well-described large dengue outbreak in Greece in 1927–28 caused more than 1 million cases (90% of the population in Athens) with 1000–1500 fatalities. The disappearance of Ae. aegypti from the European continent in Mediterranean, Black Sea, and Macaronesian biogeographical regions [2] is not well understood and its return in these regions raises concerns about a possible resurgence of the pathogens that can be transmitted by this vector species. Besides, the tiger mosquito Aedes albopictus is extending its distribution range worldwide, and it has already invaded large parts of the Mediterranean [1].
We report a case of Zika virus infection imported in Florence, Italy ex-Thailand, leading to a secondary autochthonous case, probably through sexual transmission. The two cases occurred in May 2014 but were retrospectively diagnosed in 2016 on the basis of serological tests (plaque reduction neutralisation) performed on stored serum samples. Our report provides further evidence that sexual transmission of Zika virus is possible. © 2016 European Centre for Disease Prevention and Control (ECDC). All right reserved.
Following the identification of Aedes (Ae.) aegypti in the Sochi area in Russia at the beginning of 2000, entomological surveys were conducted during the summers of 2007, 2011, and 2012, leading to the identification of Ae. albopictus and Ae. koreicus. These findings highlight Russia as being the only country in the World Health Organization European Region with a documented presence of both Ae. aegypti and Ae. albopictus mosquitoes. Both mosquito species are found on the coasts of the Black Sea. Control measures are needed to reduce the possible risks of importing exotic vector-borne infections, such as dengue and chikungunya.
Mosquito-borne viruses such as dengue, West Nile and chikungunya viruses cause significant morbidity and mortality in human populations. Since current methods are not sufficient to control disease occurrence, novel methods to control transmission of arboviruses would be beneficial. Recent studies have shown that virus infection and transmission in insects can be impeded by co-infection with the bacterium Wolbachia pipientis. Wolbachia is a maternally inherited endosymbiont that is commonly found in insects, including a number of mosquito vector species. In Drosophila, Wolbachia mediates antiviral protection against a broad range of RNA viruses. This discovery pointed to a potential strategy to interfere with mosquito transmission of arboviruses by artificially infecting mosquitoes with Wolbachia. This review outlines research on the prevalence of Wolbachia in mosquito vector species and the impact of antiviral effects in both naturally and artificially Wolbachia-infected mosquitoes.
In October 2014, an outbreak of 12 autochthonous chikungunya cases, 11 confirmed and 1 probable, was detected in a district of Montpellier, a town in the south of France colonised by the vector Aedes albopictus since 2010. A case returning from Cameroon living in the affected district was identified as the primary case. The epidemiological investigations and the repeated vector control treatments performed in the area and around places frequented by cases helped to contain the outbreak. In 2014, the chikungunya and dengue surveillance system in mainland France was challenged by numerous imported cases due to the chikungunya epidemic ongoing in the Caribbean Islands. This first significant outbreak of chikungunya in Europe since the 2007 Italian epidemic, however, was due to an East Central South African (ECSA) strain, imported by a traveller returning from West Africa. Important lessons were learned from this episode, which reminds us that the threat of a chikungunya epidemic in southern Europe is real.
Since January 2012, the Pacific Region has experienced 28 new documented outbreaks and circulation of dengue, chikungunya and Zika virus. These mosquito- borne disease epidemics seem to become more frequent and diverse, and it is likely that this is only the early stages of a wave that will continue for several years. Improved surveillance and response measures are needed to mitigate the already heavy burden on island health systems and limit further spread to other parts of the world. © 2014, European Centre for Disease Prevention and Control (ECDC). All rights reserved.
Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks occurring in 2010. The mosquito species Aedes albopictus, that was known as a secondary vector for both viruses, recently invaded the country and was the primary vector involved in the Gabonese outbreaks. We conducted a retrospective study of human sera and mosquitoes collected in Gabon from 2007 to 2010, in order to identify other circulating arboviruses.
Sample collections, including 4312 sera from patients presenting with painful febrile disease, and 4665 mosquitoes belonging to 9 species, split into 247 pools (including 137 pools of Aedes albopictus), were screened with molecular biology methods. Five human sera and two Aedes albopictus pools, all sampled in an urban setting during the 2007 outbreak, were positive for the flavivirus Zika (ZIKV). The ratio of Aedes albopictus pools positive for ZIKV was similar to that positive for dengue virus during the concomitant dengue outbreak suggesting similar mosquito infection rates and, presumably, underlying a human ZIKV outbreak. ZIKV sequences from the envelope and NS3 genes were amplified from a human serum sample. Phylogenetic analysis placed the Gabonese ZIKV at a basal position in the African lineage, pointing to ancestral genetic diversification and spread.
We provide the first direct evidence of human ZIKV infections in Gabon, and its first occurrence in the Asian tiger mosquito, Aedes albopictus. These data reveal an unusual natural life cycle for this virus, occurring in an urban environment, and potentially representing a new emerging threat due to this novel association with a highly invasive vector whose geographic range is still expanding across the globe.
In October 2013, autochthonous dengue fever was diagnosed in a laboratory technician in Bouches-du-Rhone, southern France, a department colonised by Aedes albopictus since 2010. After ruling out occupational contamination, we identified the likely chain of local vector-borne transmission from which the autochthonous case arose. Though limited, this second occurrence of autochthonous dengue transmission in France highlights that efforts should be continued to rapidly detect dengue virus introduction and prevent its further dissemination in France.
Dengue is the most important arboviral disease of humans with over half of the world's population living in areas of risk. The frequency and magnitude of epidemic dengue have increased dramatically in the past 40 years as the viruses and the mosquito vectors have both expanded geographically in the tropical regions of the world. There are many factors that have contributed to this emergence of epidemic dengue, but only three have been the principal drivers: 1) urbanization, 2) globalization and 3) lack of effective mosquito control. The dengue viruses have fully adapted to a human-Aedes aegypti-human transmission cycle, in the large urban centers of the tropics, where crowded human populations live in intimate association with equally large mosquito populations. This setting provides the ideal home for maintenance of the viruses and the periodic generation of epidemic strains. These cities all have modern airports through which 10s of millions of passengers pass each year, providing the ideal mechanism for transportation of viruses to new cities, regions and continents where there is little or no effective mosquito control. The result is epidemic dengue. This paper discusses this unholy trinity of drivers, along with disease burden, prevention and control and prospects for the future.
After information about a dengue case in Germany acquired in Croatia, health professionals and the public in Croatia were alerted to assess the situation and to enhance mosquito control, resulting in the diagnosis of a second case of autochthonous dengue fever in the same area and the detection of 15 persons with evidence of recent dengue infection. Mosquito control measures were introduced. The circumstances of dengue virus introduction to Croatia remain unresolved.
The introduction and rapidly expanding range of Aedes albopictus in Europe is an iconic example of the growing risk of the globalization of vectors and vector-borne diseases. The history of yellow fever and dengue in temperate regions confirms that transmission of both diseases could recur, particularly if Ae. aegypti, a more effective vector, were to be re-introduced. The article is a broad overview of the natural history and epidemiology of both diseases in the context of these risks.
Wolbachia are maternally inherited intracellular bacterial symbionts that are estimated to infect more than 60% of all insect species. While Wolbachia is commonly found in many mosquitoes it is absent from the species that are considered to be of major importance for the transmission of human pathogens. The successful introduction of a life-shortening strain of Wolbachia into the dengue vector Aedes aegypti that halves adult lifespan has recently been reported. Here we show that this same Wolbachia infection also directly inhibits the ability of a range of pathogens to infect this mosquito species. The effect is Wolbachia strain specific and relates to Wolbachia priming of the mosquito innate immune system and potentially competition for limiting cellular resources required for pathogen replication. We suggest that this Wolbachia-mediated pathogen interference may work synergistically with the life-shortening strategy proposed previously to provide a powerful approach for the control of insect transmitted diseases.
In 2007, physicians on Yap Island reported an outbreak of illness characterized by rash, conjunctivitis, and arthralgia. Although serum from some patients had IgM antibody against dengue virus, the illness seemed clinically distinct from previously detected dengue. Subsequent testing with the use of consensus primers detected Zika virus RNA in the serum of the patients but no dengue virus or other arboviral RNA. No previous outbreaks and only 14 cases of Zika virus disease have been previously documented.
We obtained serum samples from patients and interviewed patients for information on clinical signs and symptoms. Zika virus disease was confirmed by a finding of Zika virus RNA or a specific neutralizing antibody response to Zika virus in the serum. Patients with IgM antibody against Zika virus who had a potentially cross-reactive neutralizing-antibody response were classified as having probable Zika virus disease. We conducted a household survey to estimate the proportion of Yap residents with IgM antibody against Zika virus and to identify possible mosquito vectors of Zika virus.
We identified 49 confirmed and 59 probable cases of Zika virus disease. The patients resided in 9 of the 10 municipalities on Yap. Rash, fever, arthralgia, and conjunctivitis were common symptoms. No hospitalizations, hemorrhagic manifestations, or deaths due to Zika virus were reported. We estimated that 73% (95% confidence interval, 68 to 77) of Yap residents 3 years of age or older had been recently infected with Zika virus. Aedes hensilli was the predominant mosquito species identified.
This outbreak of Zika virus illness in Micronesia represents transmission of Zika virus outside Africa and Asia. Although most patients had mild illness, clinicians and public health officials should be aware of the risk of further expansion of Zika virus transmission.
Aedes albopictus is a mosquito originating from Asia, which has extended its range worldwide the last decades. It is a competent vector for several arboviruses. It was first described in La Réunion (an island of the South West part of the Indian Ocean) in 1913. Since then, it has become the dominant Aedes species and a serious threat to public health, especially during the two last arboviruses outbreaks of dengue (1977) and chikungunya (2005-2006). Despite its pest status, data on the biology of this vector are scarce, especially the population present in the Indian Ocean (IO), which has never been studied in detail. Therefore, the immature development, survival, longevity, fecundity, and gonotrophic cycles of Ae. albopictus were studied for an F2 population of the IO. These biological parameters were studied in controlled conditions at eight constant temperatures (5, 10, 15, 20, 25, 30, 35, and 40 degrees C). The minimal threshold of immature stages development was found at 10.4 degrees C and its optimum at 29.7 degrees C. The shortest periods for immature development were found at 30 degrees C, with in average of 8.8 d. The optimum intrinsic rate of growth (r) was observed between 25 and 30 degrees C. The gonotrophic cycles were also evaluated, and the shortest cycles were found at 30 degrees C (mean, 3.5 d). Those results are according to the field repartition of this species in La Réunion, allowing Ae. albopictus survival at a large range of temperatures.
The first record of Aedes albopictus in Croatia was made in Zagreb, Croatia, on October 28, 2004. A total of 13 larvae were collected in a discarded ceramic toilet bowl in a forested area in the southwest suburbs. Because the winter temperatures in Zagreb are not favorable for survival, this finding of Ae. albopictus may be temporary. Its survival in northern Croatia remains to be studied.
A Chikungunya (CHIK) outbreak hit La Réunion Island in 2005-2006. The implicated vector was Aedes albopictus. Here, we present the first study on the susceptibility of Ae. albopictus populations to sympatric CHIKV isolates from La Réunion Island and compare it to other virus/vector combinations.
We orally infected 8 Ae. albopictus collections from La Réunion and 3 from Mayotte collected in March 2006 with two Chikungunya virus (CHIKV) from La Réunion: (i) strain 05.115 collected in June 2005 with an Alanine at the position 226 of the glycoprotein E1 and (ii) strain 06.21 collected in November 2005 with a substitution A226V. Two other CHIKV isolates and four additional mosquito strains/species were also tested. The viral titer of the infectious blood-meal was 10(7) plaque forming units (pfu)/mL. Dissemination rates were assessed by immunofluorescent staining on head squashes of surviving females 14 days after infection. Rates were at least two times higher with CHIKV 06.21 compared to CHIKV 05.115. In addition, 10 individuals were analyzed every day by quantitative RT-PCR. Viral RNA was quantified on (i) whole females and (ii) midguts and salivary glands of infected females. When comparing profiles, CHIKV 06.21 produced nearly 2 log more viral RNA copies than CHIKV 05.115. Furthermore, females infected with CHIKV 05.115 could be divided in two categories: weakly susceptible or strongly susceptible, comparable to those infected by CHIKV 06.21. Histological analysis detected the presence of CHIKV in salivary glands two days after infection. In addition, Ae. albopictus from La Réunion was as efficient vector as Ae. aegypti and Ae. albopictus from Vietnam when infected with the CHIKV 06.21.
Our findings support the hypothesis that the CHIK outbreak in La Réunion Island was due to a highly competent vector Ae. albopictus which allowed an efficient replication and dissemination of CHIKV 06.21.
Dengue is the most common arboviral infection of humans, responsible for a substantial disease burden across the tropics. Traditional insecticide-based vector-control programmes have limited effectiveness, and the one licensed vaccine has a complex and imperfect efficacy profile. Strains of the bacterium Wolbachia, deliberately introduced into Aedes aegyptimosquitoes, have been shown to be able to spread to high frequencies in mosquito populations in release trials, and mosquitoes infected with these strains show markedly reduced vector competence. Thus, Wolbachia represents an exciting potential new form of biocontrol for arboviral diseases, including dengue. Here, we review how mathematical models give insight into the dynamics of the spread of Wolbachia, the potential impact of Wolbachia on dengue transmission, and we discuss the remaining challenges in evaluation and development.
The transmissibility of vector borne viruses can be affected by a combination of factors, both extrinsic (climatic changes, temperature, urbanization, among others) and intrinsic (genetics, life span, immunity, among others). Temperature is of particular importance since the insect vectors of arthropod-borne viruses (arboviruses) are ectothermic and acutely susceptible to temperature changes. Modeling suggests that with increasing global temperature and urbanization, arboviral diseases will continue to emerge or reemerge. This review highlights current literature regarding temperature-dependent effects on virus?vector interactions and their potential to influence the transmission dynamics and epidemiology of arboviral diseases.
The explosive pandemic of Zika virus infection occurring throughout South America, Central America, and the Caribbean (see map) and potentially threatening the United States is the most recent of four unexpected arrivals of important arthropod-borne viral diseases in the Western Hemisphere over the past 20 years. It follows dengue, which entered this hemisphere stealthily over decades and then more aggressively in the 1990s; West Nile virus, which emerged in 1999; and chikungunya, which emerged in 2013. Are the successive migrations of these viruses unrelated, or do they reflect important new patterns of disease emergence? Furthermore, are there secondary health consequences . . .
Recently, the highly invasive Asian tiger mosquito, Aedes albopictus, rapidly displaced resident populations of the yellow fever mosquito, Aedes aegypti in the southeastern United States and in Bermuda. Although multiple mechanisms of competitive displacement have been hypothesized, recent evidence of cross-insemination between these species in nature and the sterilizing effects of male accessory gland products asymmetrically favoring A. albopictus in interspecific matings support a role for satyrization (a form of reproductive interference) to explain the rapid displacements. Because of the drastic reproductive loss of A. aegypti females satyrized by A. albopictus males, we predicted selection for prezygotic isolation in populations of A. aegypti sympatric with A. albopictus. Exposures in cages demonstrated that female A. aegypti from populations in Florida sympatric with A. albopictus for the past 20 y were significantly less likely than nearby allopatric populations to mate with heterospecific males. Cross-inseminations of A. albopictus females by A. aegypti males were significantly less common, supporting the one-way direction of displacements observed in nature. Our results indicate rapid sexual selection leading to reproductive character displacement and the potential for satyr-resistant A. aegypti to recover from competitive displacements. These results have implications for increased risks of dengue transmission where these vector species meet worldwide.
Dengue virus, transmitted by mosquitoes, causes every year 50 million cases of dengue fever. A standardize method for early diagnosis is still needed for clinical diagnosis and epidemiological studies.
To develop and validate for sensitivity, specificity, linearity and precision real-time one-step RT-PCR for the detection of dengue viruses.
Multiple alignments of dengue virus sequence for each serotype were done and used to develop five systems of real-time RT-PCR to detect all dengue virus strains and then identify the serotype. These systems were validated on synthetic RNA transcripts for specificity, sensitivity, precision and linearity and then applied on series of human samples.
The specificity of each system was determined by sequence alignments and experimentally tested on different flaviviruses. Methods precision and linearity were statistically validated. Each of these systems allowed the detection of less than one infectious particle and was able to detect and serotype quickly dengue virus in human samples where infectious virus cannot be isolated anymore.
These systems are valuable tools for dengue virus diagnosis and epidemiological studies. Standardization and validation of these methods allow an easy transfer to diagnostic laboratories.
Dengue has emerged as an international public health problem. Reasons for the resurgence of dengue in the tropics and subtropics are complex and include unprecedented urbanization with substandard living conditions, lack of vector control, virus evolution, and international travel. Of all these factors, urbanization has probably had the most impact on the amplification of dengue within a given country, and travel has had the most impact for the spread of dengue from country to country and continent to continent. Epidemics of dengue, their seasonality, and oscillations over time are reflected by the epidemiology of dengue in travelers. Sentinel surveillance of travelers could augment existing national public health surveillance systems.
North American strains of Aedes albopictus, an Asian mosquito recently introduced into the Western Hemisphere, exhibit photoperiodic
sensitivity and cold-hardiness characteristics similar to strains originating from temperate zone Asia. Trade statistics for
used tire imports, the most likely mode of introduction, also indicate a north Asian origin. Aedes albopictus, an important
vector of dengue and a potential vector of many other arboviral diseases, may therefore have the capability of infesting much
of temperate North America.
In August-September 1928 appoximately 650,000 residents of Athens and Piraeus contracted dengue fever, and 1,061 died. We were interested in the etiology of this severe epidemic in which many cases resembled dengue hemorrhagic fever or the dengue shock syndrome, and have attempted a retrospective seroepidemiological study. Serum specimens were obtained from 111 residents of Athens or Piraeus who were born in 1927 or 1928, and were studied by plaque reduction neutralization test for antibodies to dengue 1-4 viruses. Of 75 persons born in 1928, 20 (27%) had monospecific dengue 1, 10 (13%) had monospecific dengue 2, and 1 (1%) had dengue 1 and 2 neutralizing antibodies. When prevalence of neutralizing antibody was analyzed by month of birth in 42 individuals, evidence of both dengue 1 and 2 infections was found in persons born in January-July, but only dengue 2 antibody was detected in those who were born after July. This study dates dengue 1 and dengue 2 transmission to 1928, allowing for the possibility that sequential infections with these viruses could have played a pathogenetic role in the outbreak.
During an epidemic of jaundice in Eastern Nigeria infection with Zika virus was shown to have occurred in three patients, one by isolation of the virus and two by a rise in serum antibodies. Two of these patients gave evidence of liver damage. Serological studies indicate a relationship between jaundice and the development of virus neutralizing bodies in the serum.
Effects of food, density, and heterospecific interactions on temperature-dependent development of Aedes albopictus (Skuse) and Aedes triseriatus (Say) larvae and pupae were described using a degree-day model. Under all conditions, the predicted number of degree-days (DD(T0)) to complete larval development was less, and the threshold temperature (T0) for initiation of larval development was higher for Ae. albopictus than for Ae. triseriatus. The DD(T0) for both species was food and density dependent. However, the per capita food ration appeared to exert a greater influence on the developmental times of Ae. triseriatus immatures, whereas for Ae. albopictus effects of density were not completely eliminated by an increase in the per capita food ration. The presence of heterospecific larvae did not prolong the DD(T0) of either species. At the low food ration, DD(T0) for both species were significantly greater under conspecific conditions. The DD(T0) for Ae. triseriatus increased directly as the proportion of conspecific larvae increased. However, when a higher per capita food ration was provided, conspecific effects on DD(T0) were mitigated. For Ae. albopictus, estimated DD(T0) values for larvae reared in pure culture were significantly higher than when heterospecific larvae were present, regardless of the per capita amount of food provided. Survivorship of immatures was density and food-dependent for both species. Ae. albopictus exhibited higher immature survivorship under all conditions relative to Ae. triseriatus. For both species, survival probabilities were lowest under conditions of high density and low food. Addition of food improved survival for both species. The presence of heterospecific larvae exerted a differential effect on the survivorship response of Ae. albopictus immatures to temperature. Lowest probability of survival for Ae. albopictus was occurred at low temperature when the proportion of heterospecific larvae in containers was the highest. In contrast, at high temperatures, survivorship of immatures improved, but was lowest for pure species cultures. For Ae. triseriatus, survivorship of immatures was consistently lower for pure species cultures regardless of the temperature. Standing crop production of adults of both species was primarily food rather that density-dependent. Under field conditions, Ae. triseriatus were predicted to initiate development sooner and exhibit faster population growth early in the season than Ae. albopictus. However, because of the shorter DD(T0), Ae. albopictus population growth was predicted to surpass that of Ae. triseriatus populations later in the season. Based on optimal DD(T0) values from laboratory experiments, spring emergence dates of Ae. triseriatus females in western North Carolina for 1989 and 1990 were predicted from accumulated degree-days calculated from local air temperature records. Predicted emergence dates were congruent with results of a previous survey for the same locality, indicating that accumulated degree-days can be used to accurately predict the seasonal occurrence of Ae. triseriatus. The utility of the degree-day approach in predicting the phenology of Ae. albopictus remains to be established.
Dengue fever (DF) is an old disease; the first record of a clinically compatible disease being recorded in a Chinese medical encyclopaedia in 992. As the global shipping industry expanded in the 18th and 19th centuries, port cities grew and became more urbanized, creating ideal conditions for the principal mosquito vector, Aedes aegypti. Both the mosquitoes and the viruses were thus spread to new geographic areas causing major epidemics. Because dispersal was by sailing ship, however, there were long intervals (10-40 years) between epidemics. In the aftermath of World War II, rapid urbanization in Southeast Asia led to increased transmission and hyperendemicity. The first major epidemics of the severe and fatal form of disease, dengue haemorrhagic fever (DHF), occurred in Southeast Asia as a direct result of this changing ecology. In the last 25 years of the 20th century, a dramatic global geographic expansion of epidemic DF/DHF occurred, facilitated by unplanned urbanization in tropical developing countries, modern transportation, lack of effective mosquito control and globalization. As we go into the 21st century, epidemic DF/DHF is one of the most important infectious diseases affecting tropical urban areas. Each year there are an estimated 50-100 million dengue infections, 500000 cases of DHF that must be hospitalized and 20000-25 000 deaths, mainly in children. Epidemic DF/DHF has an economic impact on the community of the same order of magnitude as malaria and other important infectious diseases. There are currently no vaccines nor antiviral drugs available for dengue viruses; the only effective way to prevent epidemic DF/DHF is to control the mosquito vector, Aedes aegypti.
Invasive mosquito species of the Black sea coast of the Caucasus: current ranges
- M V Fedorova
- O G Shvez
- I V Patraman
Fedorova MV, Shvez OG, Patraman IV, et al.2019. Invasive mosquito species of the Black sea coast of the Caucasus: current ranges. Med Parazitol Mosk.-2019 (a). No 1.
P.47-55. doi:10.33092/0025-8326mp2019.1.47-55 (In Russ.).
Pervie dannie o nalichii razmnozhayuschikhciy populiatstiyakh, Aedes aegypti L. v rayonakh Bol’shogo Sochi I otdelnikh gorodakh Abkhazii. Meditsinskaya Parazitologiya i Parazitarnyye bolezni
- Yunicheva Yuv
- T E Ryabova
- Markovich Nya
Yunicheva YuV, Ryabova TE, Markovich NYa, et al. Pervie dannie o nalichii razmnozhayuschikhciy populiatstiyakh, Aedes aegypti L. v rayonakh Bol'shogo Sochi I otdelnikh
gorodakh Abkhazii. Meditsinskaya Parazitologiya i Parazitarnyye bolezni. 2008; 3:140-43 (In Russ.).
// Euro surveillance: bulletin Européen sur les maladies transmissibles = European communicable disease bulletinance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin
- I Gjenero-Margan
- B Aleraj
- D Krajcar
Gjenero-Margan I., Aleraj B., Krajcar D., et al. Autochthonous Dengue Fever in Croatia, August-September 2010. // Euro surveillance: bulletin Européen sur les maladies
transmissibles = European communicable disease bulletinance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin. 2011 Mar
3;16(9):19805. PMID: 21392489.
The New England journal of medicine
- C P Simmons
- J J Farrar
- Nvv Chau
Simmons CP, Farrar JJ, Chau NVV, et al. Dengue. The New England journal of medicine. 2012 Apr 12;366(15):1423-32. doi: 10.1056/NEJMra1110265.
Obnaruzhenie komarov Aedes (Stegomyia) aegypti L. v g. Sochi. Medical Parasitology and parasitic diseases
- T E Ryabova
- Y V Unichema
- N I Markovich
Ryabova TE, Unichema YV, Markovich NI, et al. Obnaruzhenie komarov Aedes (Stegomyia) aegypti L. v g. Sochi. Medical Parasitology and parasitic diseases. 2005. № 3.
Pp. 3-4 (In Russ.).
Yellow fever and dengue: a threat to Europe? Euro surveillance: bulletin Européen sur les maladies transmissibles = European communicable disease bulletinance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin
- P Reiter