Virus In Natural Populations Research Articles

A Systematic Review on the Viruses of Anopheles Mosquitoes: The Potential Importance for Public Health.

Anopheles mosquitoes are the vectors of Plasmodium, the etiological agent of malaria. In addition, Anopheles funestus and Anopheles gambiae are the main vectors of the O'nyong-nyong virus. However, research on the viruses carried by Anopheles is scarce; thus, the possible transmission of viruses by Anopheles is still unexplored. This systematic review was carried out to identify studies that report viruses in natural populations of Anopheles or virus infection and transmission in laboratory-reared mosquitoes. The databases reviewed were EBSCO-Host, Google Scholar, Science Direct, Scopus and PubMed. After the identification and screening of candidate articles, a total of 203 original studies were included that reported on a variety of viruses detected in Anopheles natural populations. In total, 161 viruses in 54 species from 41 countries worldwide were registered. In laboratory studies, 28 viruses in 15 Anopheles species were evaluated for mosquito viral transmission capacity or viral infection. The viruses reported in Anopheles encompassed 25 viral families and included arboviruses, probable arboviruses and Insect-Specific Viruses (ISVs). Insights after performing this review include the need for (1) a better understanding of Anopheles-viral interactions, (2) characterizing the Anopheles virome-considering the public health importance of the viruses potentially transmitted by Anopheles and the significance of finding viruses with biological control activity-and (3) performing virological surveillance in natural populations of Anopheles, especially in the current context of environmental modifications that may potentiate the expansion of the Anopheles species distribution.

First detection of dengue and chikungunya viruses in natural populations of Aedes aegypti in Martinique during the 2013 – 2015 concomitant outbreak

ABSTRACTDengue and chikungunya viruses are transmitted by Aedes mosquitoes. In Martinique, an island of the French West Indies, Aedes aegypti is the suspected vector of both arboviruses; there is no Aedes albopictus on the island. During the concomitant outbreak of 2013 – 2015, the authors collected wild A. aegypti populations, and for the first time, detected dengue and chikungunya viruses in field-collected females. This paper demonstrates the mosquito’s role in transmission of both dengue and chikungunya on the island, and also highlights a tool that public health authorities can use for preventing outbreaks.

Risk assessment of gene flow from genetically engineered virus resistant cassava to wild relatives in Africa: an expert panel report.

The probability and consequences of gene flow to wild relatives is typically considered in the environmental risk assessment of genetically engineered crops. This is a report from a discussion by a group of experts who used a problem formulation approach to consider existing information for risk assessment of gene flow from cassava (Manihot esculenta) genetically engineered for virus resistance to the 'wild' (naturalized) relative M. glaziovii in East Africa. Two environmental harms were considered in this case: (1) loss of genetic diversity in the germplasm pool, and (2) loss of valued species, ecosystem resources, or crop yield and quality due to weediness or invasiveness of wild relatives. Based on existing information, it was concluded that gene flow will occur, but it is not likely that this will reduce the genetic diversity in the germplasm pool. There is little existing information about the impact of the virus in natural populations that could be used to inform a prediction about whether virus resistance would lead to an increase in reproduction or survival, hence abundance of M. glaziovii. However, an increase in the abundance of M. glaziovii should be manageable, and would not necessarily lead to the identified environmental harms.

Characterization of 27 molecular markers linked toBarley Yellow Dwarf Virus(BYDV) resistance genes inElymus shandongensis(Triticeae, Poaceae)

Barley Yellow Dwarf Virus (BYDV) is a pathogen caused serious yield losses in cereals, which may become even more important due to its intrinsic adaptation and global warming. As a perennial species in Triticeae, Elymus shandongensis contains genes resistant to BYDV. The 27 molecular markers linked to BYDV resistance genes developed from Triticeae species were characterized. The 25 loci were polymorphic, and 2 loci were monomorphic in this study. The number of alleles ranged from 1 to 6. The effective number of alleles (Ne) of each primer ranged from 1 to 1.932 (mean= 1.624). The Shannon's information index (I) of each primer ranged from 0 to 0.662 (mean= 0.499), and the unbiased genetic diversity (He) ranged from 0 to 0.481 (mean= 0.353). The population from the Lingshan island (PL) showed a lower level of genetic variation (P =80.25%, I =0.477, and He =0.338), whereas the population from the surrounding areas of the Laoshan reservoir (PS†) had a higher level of genetic diversity (P =90.12%, I =0.520, and He =0.368). Four private alleles were found in PL and 1 private allele was found in PS†. The results indicated the 27 markers could be used in future genetic study of E. shandongensis that might be useful in a context of wheat breeding, germplasms conservation, finding useful resistant genotype to BYDV and adaptive evolution at resistance loci to virus in natural populations.

Illumination of Murine Gammaherpesvirus-68 Cycle Reveals a Sexual Transmission Route from Females to Males in Laboratory Mice

Transmission is a matter of life or death for pathogen lineages and can therefore be considered as the main motor of their evolution. Gammaherpesviruses are archetypal pathogenic persistent viruses which have evolved to be transmitted in presence of specific immune response. Identifying their mode of transmission and their mechanisms of immune evasion is therefore essential to develop prophylactic and therapeutic strategies against these infections. As the known human gammaherpesviruses, Epstein-Barr virus and Kaposi's Sarcoma-associated Herpesvirus are host-specific and lack a convenient in vivo infection model; related animal gammaherpesviruses, such as murine gammaherpesvirus-68 (MHV-68), are commonly used as general models of gammaherpesvirus infections in vivo. To date, it has however never been possible to monitor viral excretion or virus transmission of MHV-68 in laboratory mice population. In this study, we have used MHV-68 associated with global luciferase imaging to investigate potential excretion sites of this virus in laboratory mice. This allowed us to identify a genital excretion site of MHV-68 following intranasal infection and latency establishment in female mice. This excretion occurred at the external border of the vagina and was dependent on the presence of estrogens. However, MHV-68 vaginal excretion was not associated with vertical transmission to the litter or with horizontal transmission to female mice. In contrast, we observed efficient virus transmission to naïve males after sexual contact. In vivo imaging allowed us to show that MHV-68 firstly replicated in penis epithelium and corpus cavernosum before spreading to draining lymph nodes and spleen. All together, those results revealed the first experimental transmission model for MHV-68 in laboratory mice. In the future, this model could help us to better understand the biology of gammaherpesviruses and could also allow the development of strategies that could prevent the spread of these viruses in natural populations.

Evidence for interspecies transmission of viruses in natural populations of filamentous fungi in the genus Cryphonectria.

Interspecies transmission is a significant evolutionary event that has allowed a variety of pathogens to invade new host species. We investigated interspecies transmission of viruses between the chestnut blight fungus, Cryphonectria parasitica, and a sympatric unidentified Cryphonectria species in Japan. Two isolates of Cryphonectria sp. were found to contain Cryphonectria hypovirus 1 (CHV-1), which has been typically found in C. parasitica. Three lines of evidence support the hypothesis of interspecies transmission of CHV-1. First, host species occur sympatrically and therefore have the opportunity to come into physical contact. Second, we transmitted CHV-1 between species experimentally in the laboratory. Third, phylogenetic analysis of 476 bp of the ORF B region of CHV-1 showed that sequences from Cryphonectria sp. were more closely related to those from C. parasitica than to each other. Local geographical subdivision of virus sequences from both host species argues against the alternative hypothesis of independent evolution of CHV-1 since speciation of their hosts. Based on these findings, we rule out the hypotheses that CHV-1 diverged from viruses in a common ancestor of the hosts, or that ancestral polymorphisms in CHV-1 persisted in the two host taxa. Estimating the direction and frequency of interspecies transmission in nature will require more extensive samples of CHV-1 from both host species.

Host Heterogeneity in Susceptibility and Disease Dynamics: Tests of a Mathematical Model

Most mathematical models of disease assume that transmission is linearly dependent on the densities of host and pathogen. Recent data for animal diseases, however, have cast doubt on this assumption, without assessing the usefulness of alternative models. In this article, we use a combination of laboratory dose-response experiments, field transmission experiments, and observations of naturally occurring populations to show that virus transmission in gypsy moths is a nonlinear function of virus density, apparently because of heterogeneity among individual gypsy moth larvae in their susceptibility to the virus. Dose-response experiments showed that larvae from a laboratory colony of gypsy moths are substantially less heterogeneous in their susceptibility to the virus than are larvae from feral populations, and field experiments showed that there is a more strongly nonlinear relationship between transmission and virus density for feral larvae than for lab larvae. This nonlinearity in transmission changes the dynamics of the virus in natural populations so that a model incorporating host heterogeneity in susceptibility to the virus gives a much better fit to data on virus dynamics from large-scale field plots than does a classical model that ignores host heterogeneity. Our results suggest that heterogeneity among individuals has important effects on the dynamics of disease in insects at several spatial and temporal scales and that heterogeneity in susceptibility may be of general importance in the ecology of disease.

Properties of the Iranian Isolate of Bermudagrass Etched‐line Virus

AbstractThe Iranian isolate of bermudagrass etched‐line virus (BELV‐I), purified by low‐pH treatment of infected bermudagrass sap followed by several cycles of differential centrifugation and sucrose density‐gradient centrifugation, formed two components in density‐gradient columns. The top component consisted of empty protein shells. It had a major structural protein of c. 22 kDa and a minor of c. 25 kDa. The weight of the nucleic acid present only in bottom component particles, was calculated to be 1.82 × 106 Da. Only Aconurella prolixa (Leth.) was able to transmit the virus under experimental conditions or contained the virus in natural populations. In ELISA tests the virus titer in the vector increased rapidly between days 14 and 29 after acquisition, results indicating a propagative relationship. BELV‐1 was serologically closely related to the Moroccan isolate of BELV, and related to the American but not to the Costa Rican isolate of maize rayado fino virus (MRFV). Several graminaceous species were found to be experimental or natural hosts of the virus.

Blueberry Shoestring Virus in Natural Populations of Highbush and Lowbush Blueberry

Abstract Blueberry shoestring virus (BBSSV) is the most serious disease in Michigan, and it has been reported in New Jersey, Washington, North Carolina, and Nova Scotia (4, 8). Shoestring is particularly difficult to eradicate, since there is no known control other than removing diseased bushes, and infected bushes do not show external symptoms for up to 4 years. Also, no cultivars of highbush blueberry are immune to the disease (2).

Transmission efficiency of the sigma virus in natural populations of its host, Drosophila melanogaster.

A study of the viral samples collected in French natural populations of Drosophila melanogaster since 1969, indicates that natural populations include, as expected, both stabilized and non stabilized infected individuals. In agreement with previous observations made on other characters of the virus, the viral samples collected appear to be homogeneous for the efficiency of the hereditary transmission. However, this efficiency is greater than the average value observed with virus perpetuated in infected laboratory fly strains. One sample collected in Gabon and three in the U.S.A. appear to differ from the French samples for one at least of the traits studied in these experiments.

Observations on Myxomatosis in a Rabbit Population With Immune Adults.

High mortality (88-100%) was observed during two outbreaks of myxomatosis between 1973 and 1974 in a population of Oryctolagus cuniculus at Canberra. The presence of immune adult rabbits predisposed the disease to be confined either to the young kittens or to susceptible immature rabbits surviving from the period between the outbreaks. A virulent Lausanne strain myxoma virus was deliberately introduced by means of infective fleas (Spilopsyllus cuniculi). Field strains were present. Reactivation and transmission of virus in natural populations is discussed. The possibility of contact rather than vector (flea) transmission is examined in respect of failure to maintaining the outbreaks. Some observations were made on rabbits that recovered from myxomatosis and on the occurrence in some individuals of persistent sublethal signs of myxomatosis. Frequency of raptor predation is compared between periods with and without myxomatous rabbits. The duration of survival of infected rabbits is not significantly reduced by predation, but some raptors, such as brown hawk and little eagle, may concentrate more on the youngest available rabbits during an outbreak. ADDITIONAL ABSTRACT: High case mortalities (88-100%) were observed during two outbreaks of myxomatosis between 1973 and 1974 in a population of rabbits (Oryctolagus cuniculus), at Canberra, Australia. The presence of immune adult rabbits predisposed the disease to be confined either to the young kittens or to susceptible immature rabbits surviving from the period between the epizootics. A virulent Lausanne strain myxoma virus was deliberately introduced by means of infective Spilopsyllus cuniculi (Dale). Field strains were present. Reactivation and transmission of virus in natural populations is discussed. The possibility of contact rather than vector (flea) transmission is examined in respect of failure to maintaining the epizootics. Some observations were made on rabbits that recovered from myxomatosis and on the occurrence in some individuals of persistent sublethal signs of myxomatosis. The duration of survival of infected rabbits was not significantly reduced by predation, but some raptors sometimes concentrated more on the youngest available rabbits during an epizootic.

Presence of the Hereditary Rhabdovirus Sigma and Polymorphism for a Gene for Resistance to this Virus in Natural Populations of Drosophila melanogaster

Presence of the Hereditary Rhabdovirus Sigma and Polymorphism for a Gene for Resistance to this Virus in Natural Populations of Drosophila melanogaster