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Horizontal Transmission (horizontal + transmission)

Distribution by Scientific Domains

Life Sciences	69%
Earth and Environmental Science	15%
Medical Sciences	12%

Distribution within Life Sciences

Entomology	30%
Evolution	26%

Selected Abstracts

HOST GROWTH CONDITIONS INFLUENCE EXPERIMENTAL EVOLUTION OF LIFE HISTORY AND VIRULENCE OF A PARASITE WITH VERTICAL AND HORIZONTAL TRANSMISSION

EVOLUTION, Issue 7 2010
Hélène Magalon
In parasites with mixed modes of transmission, ecological conditions may determine the relative importance of vertical and horizontal transmission for parasite fitness. This may lead to differential selection pressure on the efficiency of the two modes of transmission and on parasite virulence. In populations with high birth rates, increased opportunities for vertical transmission may select for higher vertical transmissibility and possibly lower virulence. We tested this idea in experimental populations of the protozoan Paramecium caudatum and its bacterial parasite Holospora undulata. Serial dilution produced constant host population growth and frequent vertical transmission. Consistent with predictions, evolved parasites from this "high-growth" treatment had higher fidelity of vertical transmission and lower virulence than parasites from host populations constantly kept near their carrying capacity ("low-growth treatment"). High-growth parasites also produced fewer, but more infectious horizontal transmission stages, suggesting the compensation of trade-offs between vertical and horizontal transmission components in this treatment. These results illustrate how environmentally driven changes in host demography can promote evolutionary divergence of parasite life history and transmission strategies. [source]

Horizontal transmission of Wolbachia in a Drosophila community

ECOLOGICAL ENTOMOLOGY, Issue 4 2005
Eleanor R. Haine
Abstract., 1.,Wolbachia bacteria are reproductive parasites of arthropods and infect an estimated 20% of all insect species worldwide. In order to understand patterns of Wolbachia infection, it is necessary to determine how infections are gained or lost. Wolbachia transmission is mainly vertical, but horizontal transmission between different host species can result in new infections, although its ecological context is poorly understood. Horizontal transmission is often inferred from molecular phylogenies, but could be confounded by recombination between different Wolbachia strains. 2.,This study addressed these issues by using three genes: wsp, ftsZ, and groE, to study Wolbachia infections in fruit- and fungus-feeding Drosophila communities in Berkshire, U.K. 3.,Identical sequences were found for all three genes in Drosophila ambigua and Drosophila tristis. This suggests horizontal transmission of Wolbachia between these two previously unstudied Drosophila species, which may be the result of the two host species sharing the same food substrates or parasites. 4.,Wolbachia infections might be lost from species due to curing by naturally occurring antibiotics and the presence of these is likely to vary between larval food substrates. 5.,It was investigated whether Wolbachia incidence was lower in fungus-feeding than in fruit-feeding Drosophila species, but no significant difference based on food substrate was found. [source]

Translocation of viable Aeromonas salmonicida across the intestine of rainbow trout, Oncorhynchus mykiss (Walbaum)

JOURNAL OF FISH DISEASES, Issue 5 2006
F Jutfelt
Abstract The pathogenic bacterium Aeromonas salmonicida is the causative agent of the destructive disease furunculosis in salmonids. Horizontal transmission in salmonids has been suggested to occur via the skin, gills and/or intestine. Previous reports are contradictory regarding the role of the intestine as a route of infection. The present study therefore investigates the possibility of bacterial translocation across intestinal epithelia using Ussing chamber technology, in vitro. Intestinal segments were exposed for 90 min to fluorescein isothiocyanate-labelled pathogenic A. salmonicida. Sampling from the serosal side of the Ussing chambers showed that bacteria were able to translocate across the intestinal epithelium in both the proximal and distal regions. Plating and subsequent colony counting showed that the bacteria were viable after translocation. During the 90 min exposure to A. salmonicida, the intestinal segments maintained high viability as measured by electrical parameters. The distal region responded to bacterial exposure by increasing the electrical resistance, indicating an increased mucus secretion. This study thus demonstrates translocation of live A. salmonicida through the intestinal epithelium of rainbow trout, suggesting that the intestine is a possible route of infection in salmonids. [source]

Horizontal transmission of Beauveria bassiana (Bals.) Vuill

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2000
David W. Long
Summary 1 Factors influencing horizontal transmission of the entomopathogen Beauveria bassiana in the Colorado potato beetle (CPB) were examined through a series of laboratory studies. 2 Cadaver density, cadaver life stage, ambient temperature and conidial density were the factors manipulated. 3 Mortality and sporulation of burrowing CPB prepupae both increased significantly with increased sporulating second-instar cadaver density on the soil surface. 4 Mortality rates were significantly higher when prepupae were released into laboratory arenas containing third-instar cadavers compared to second-instar cadavers. 5 Mortality and sporulation decreased significantly as temperature increased from 15 °C to 30 °C, however, no temperature-dependent behavioural response by prepupae could be identified as a potential cause. 6 An 86.1% decrease in conidial density per cadaver had no significant effect on mortality or sporulation of prepupae, indicating that this level of environmental degradation of cadavers may not significantly reduce the probability of horizontal transmission. [source]

Horizontal transmission of Wolbachia by strepsipteran endoparasites?

MOLECULAR ECOLOGY, Issue 2 2004
A response to Noda et al.
No abstract is available for this article. [source]

Estimation of dispersal distances of the obligately plant-associated ant Crematogaster decamera

ECOLOGICAL ENTOMOLOGY, Issue 5 2010
MANFRED TÜRKE
1. In obligate symbioses with horizontal transmission, the population dynamics of the partner organisms are highly interdependent. Host population size limits symbiont number, and distribution of partners is restricted by the presence and thus dispersal abilities of their respective partner. The Crematogaster decamera,Macaranga hypoleuca ant,plant symbiosis is obligate for both partners. Host survival depends on colonisation by its ant partner while foundress queens require hosts for colony establishment. 2. An experimental approach and population genetic analyses were combined to estimate dispersal distances of foundresses in their natural habitat in a Bornean primary rainforest. 3. Colonisation frequency was significantly negatively correlated with distance to potential reproductive colonies. Results were similar for seedlings at natural densities as well as for seedlings brought out in the area experimentally. Population genetic analysis revealed significant population differentiation with an FST of 0.041 among foundresses (n = 157) located at maximum 2280 m apart. In genetic spatial autocorrelation, genotypes of foundresses were significantly more similar than expected at random below 550 m and less similar above 620 m. Direct estimation of dispersal distances by pedigree analysis yielded an average dispersal distance of 468 m (maximum 1103 m). 4. For ants that disperse on the wing, genetic differentiation at such small spatial scales is unusual. The specific nesting requirements of the queens and the necessity for queens to find a host quickly could lead to colonisation of the first suitable seedling encountered, promoting short dispersal distances. Nonetheless, dispersal distances of C. decamera queens may vary with habitat or host spatial distribution. [source]

Horizontal transmission of Wolbachia in a Drosophila community

HOST GROWTH CONDITIONS INFLUENCE EXPERIMENTAL EVOLUTION OF LIFE HISTORY AND VIRULENCE OF A PARASITE WITH VERTICAL AND HORIZONTAL TRANSMISSION

Good outcome in HIV-infected refugees after resettlement in New Zealand: population study

INTERNAL MEDICINE JOURNAL, Issue 5 2007
S. M. Nisbet
Abstract Background: The aims of this study were to determine the clinical characteristics on arrival and the subsequent clinical outcome of HIV-infected UN quota refugees who settled in New Zealand during the last 11 years and to estimate their rate of HIV transmission. Methods: A population study was conducted. Data were provided by the Mangere Refugee Resettlement Centre, the infectious disease physicians caring for the subjects, the New Zealand AIDS Epidemiology Group and laboratories carrying out HIV viral load assays. Results: One hundred of 7732 (1.3%) UN quota refugees were HIV positive; mean age 30 years, 56% were men, median initial CD4 count was 320 (range 20,1358). HIV infection was most commonly acquired by heterosexual intercourse (74%). The median follow up was 5.0 years (range 1 month to 9.7 years). Five died and 15 subjects had 16 AIDS-defining illnesses, most commonly tuberculosis (n = 10). Sixty subjects commenced highly active antiretroviral therapy of whom 36/59 (61%) had an undetectable HIV viral load after 1 year of treatment. None of the six children born to HIV-infected women in New Zealand were infected. There were two known cases of horizontal transmission of HIV infection. Conclusion: Although HIV-infected quota refugees often have to overcome severe social, cultural and financial handicaps, their clinical outcome is generally very good, with response rates to highly active antiretroviral therapy that are similar to other patient groups. Furthermore, they have not been a significant source of transmission of HIV infection after resettlement in New Zealand. [source]

Host behaviour and exposure risk in an insect,pathogen interaction

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2010
Benjamin J. Parker
Summary 1.,Studies of variability in host resistance to disease generally emphasize variability in susceptibility given exposure, neglecting the possibility that hosts may vary in behaviours that affect the risk of exposure. 2.,In many insects, horizontal transmission of baculoviruses occurs when larvae consume foliage contaminated by the cadavers of virus-infected conspecific larvae; so, host behaviour may have a strong effect on the risk of infection. 3.,We studied variability in the behaviour of gypsy moth (Lymantria dispar) larvae, which are able to detect and avoid virus-contaminated foliage. 4.,Our results show that detection ability can be affected by the family line that larvae originate from, even at some distance from a virus-infected cadaver, and suggest that cadaver-detection ability may be heritable. 5.,There is thus the potential for natural selection to act on cadaver-detection ability, and thereby to affect the dynamics of pathogen-driven cycles in gypsy moth populations. 6. We argue that host behaviour is a neglected component in studies of variability in disease resistance. [source]

Three microsporidian pathogens infecting Lymantria dispar larvae do not differ in their success in horizontal transmission

JOURNAL OF APPLIED ENTOMOLOGY, Issue 7 2009
D. Goertz
Abstract We quantified horizontal transmission of three microsporidian pathogens, Endoreticulatus schubergi, Nosema lymantriae and Vairimorpha disparis that infect Lymantria dispar larvae in an experiment using caged, potted oak plants. Despite marked differences in the modes of spore release from infectious hosts, no significant differences in the transmission success to uninfected, susceptible test hosts were ascertained between the tested microsporidian species. The density of initially inoculated larvae and the exposure period, on the other hand, did influence the number of infected test larvae. Depending on the density of inoculated larvae (10%, 30% or 50%), between 0% and 26% of the test larvae became infected with one of the three tested microsporidian pathogens after an exposure period of 6 days. When the exposure period was 12 days, between 11% and 76% of the test larvae became infected. [source]

The influence of greenhouse chrysanthemum on the interaction between the beet armyworm, Spodoptera exigua, and the baculovirus SeMNPV: parameter quantification for a process-based simulation model

JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001
F. J. J. A. Bianchi
During the building of a process-based simulation model for the epidemiology of the multicapsid nucleopolyhedrovirus of S. exigua (SeMNPV) in populations of Spodoptera exigua (Hübner) in greenhouse chrysanthemum, it was found that the effect of host plants had been under-rated. ,Missing links' included (i) the ,natural' background mortality of larvae of S. exigua in practical cropping conditions; (ii) the developmental rate of larvae of S. exigua on plant substrate in a glasshouse as compared to artificial medium in the laboratory; (iii) the validity of the results of dose-mortality and time-mortality bioassays conducted on artificial medium as compared to natural plant substrate; (iv) the distribution of inoculum released from deceased caterpillars over chrysanthemum leaves; and (v) the leaf visit rate of healthy caterpillars (as it affects horizontal transmission). Experiments were carried out to quantify these processes. Developmental rates of S. exigua larvae on greenhouse chrysanthemum were 36% lower than on an artificial diet. The fraction survival during the first, second, third and fourth instar S. exigua larvae in greenhouse chrysanthemum was 0.60, 0.80, 0.88 and 0.95, respectively. Forty percent of the first instar larvae reached the fifth larval stage. Second instar S. exigua larvae reared on chrysanthemum were significantly more susceptible to SeMNPV than larvae reared on an artificial diet. The food source had no effect on the time to kill S. exigua larvae. Cadavers of second, third and fourth instar S. exigua larvae contaminated on average 1.4, 2.5 and 3.3 chrysanthemum leaves. Second to fourth instar S. exigua larvae visited 2,3 leaves per day and spent 15,55% of the time on the underside of leaves. The above information is of critical importance for a trustworthy simulation of the epidemiology of SeMNPV in chrysanthemum. [source]

The rate of horizontal transmission of antibiotic resistance plasmids is increased in food preservation-stressed bacteria

JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007
M.A.S. Mc Mahon
Abstract Aim: The aim of this study was to investigate the possibility that sublethal food preservation stresses (high/low temperature, osmotic and pH stress) can alter the rate of horizontal transmission of antibiotic resistance (ABR) plasmids between Escherichia coli strains and between E. coli and Salmonella serotype Typhimurium. Methods and Results: Escherichia coli donor cultures, carrying F1 plasmid R386 and Inc I1 plasmid TP307 and E. coli and Salm. Typhimurium recipient cultures were prestressed under a range of sublethal environmental conditions (high/low temperature, osmotic and pH stress). The prestressed donor and recipient cultures were then mated and the transmission rate calculated. The study found that the horizontal transmission rate of plasmids R386 and TP307 was significantly increased (P < 0·05) when prestressed donor and recipient cells are mated under conditions of environmental stress. Conclusion: The results from this study indicate that, the sublethal stresses that food pathogens encounter in modern food preservation systems increase the inter- and intra-specific horizontal transmission of selected ABR plasmids. Significance and Impact of the Study: Increased use of bacteriostatic (sublethal), rather than bacteriocidal (lethal) food preservation systems, may be contributing to the dissemination of ABR among important food borne pathogens. [source]

Association with host mitochondrial haplotypes suggests that feminizing microsporidia lack horizontal transmission

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2003
J. E. Ironside
Abstract The amphipod crustacean Gammarus duebeni hosts two feminizing microsporidian parasites, Nosema granulosis and Microsporidium sp. Samples of G. duebeni were collected from three sites on the Scottish island of Great Cumbrae and screened for microsporidia using polymerase chain reaction. Associations between the prevalence of the two feminizing parasites and haplotypes of the host mitochondrial gene cytochrome oxidase I (COI) were investigated. The prevalence of both parasites varied significantly among the host's COI haplotypes, suggesting that horizontal transmission is rare or absent in the life cycles of the feminizing microsporidia and that all transmission must therefore be vertical. Life cycles in which all transmission is vertical are common among bacterial parasites but have never before been demonstrated in Eukaryotic parasites. [source]

Two species of feminizing microsporidian parasite coexist in populations of Gammarus duebeni

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2003
J. E. Ironside
Abstract The amphipod crustacean Gammarus duebeni hosts two species of vertically transmitted microsporidian parasites, Nosema granulosis and Microsporidium sp. A. Here it is demonstrated that these co-occurring parasite species both cause infected females to produce female-biased broods. A survey of European G. duebeni populations demonstrates that these two parasites co-occur in six of 10 populations. These findings contrast with the theoretical prediction that two vertically transmitted feminizing parasites should not coexist in a panmictic population of susceptible hosts at equilibrium. Possible explanations for the co-occurrence of the two feminizing microsporidia in G. duebeni include the recent invasion of a new parasite, horizontal transmission of one or both parasites and the spread of alleles for resistance to the dominant parasite in host populations. [source]

Phylogenetic analyses and molecular epidemiology of European salmonid alphaviruses (SAV) based on partial E2 and nsP3 gene nucleotide sequences

JOURNAL OF FISH DISEASES, Issue 11 2008
E Fringuelli
Abstract Sequence data were generated for portions of the E2 and nsP3 genes of 48 salmonid alphaviruses from farmed Atlantic salmon (AS), Salmo salar L., and rainbow trout (RT), Oncorhynchus mykiss (Walbaum), in marine and freshwater environments, respectively, from the Republic of Ireland, Northern Ireland, England, Scotland, Norway, France, Italy and Spain between 1991 and 2007. Based on these sequences, and those of six previously published reference strains, phylogenetic trees were constructed using the parsimony method. Trees generated with both gene segments were similar. Clades corresponding to the three previously recognized subtypes were generated and in addition, two further new clades of viruses were identified. A single further strain (F96-1045) was found to be distinct from all of the other strains in the study. The percentage of nucleotide divergence within clades was generally low (0,4.8% for E2, 0,6.6% for nsP3). Interclade divergence tended to be higher (3.4,19.7% for E2, 6.5,28.1% for nsP3). Based on these results and using current SAV terminology, the two new clades and F96-1045 were termed SAV subtypes 4, 5 and 6, respectively. SAV4 contained AS strains from Ireland and Scotland, while SAV5 contained only Scottish AS strains. Recently identified SAV strains from RT in Italy and Spain were shown to belong to SAV2. In addition, marine AS strains belonging to SAV2 were identified for the first time. Analysis of the origin of several clusters of strains with identical E2 and nsP3 sequences strongly support horizontal transmission of virus between farms and aquaculture companies. Evidence in support of vertical transmission was not found. [source]

Occurrence and effects of Nosema fumiferanae infections on adult spruce budworm caught above and within the forest canopy

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2007
Eldon S. Eveleigh
Abstract 1,Nosema fumiferanae infections in populations of both sexes of spruce budworm Choristoneura fumiferana moths, collected live above the forest canopy (canopy moths), within the tree crown (crown moths) and in drop trays (dead moths), were examined over a 5-year period in New Brunswick, Canada. 2,The incidence of infection and of moderate,heavy infections in canopy and crown moths of both sexes increased concomitantly with moth eclosion, indicating that N. fumiferanae retards larval/pupal development, with infected moths, particularly those having higher disease loads, emerging later in the season. 3,Infection rates differed among canopy, crown, and dead female, but not male, moths. Canopy (i.e. emigrating) females had a lower incidence of infection, lower incidence of moderate,heavy infections, and had longer forewings and higher dry weights, than crown females. These results suggest that N. fumiferanae infections negatively affect aspects of female, but not male, flight performance. Regardless of infection, forewing length and dry weight of both canopy and crown females declined over the moth flight period, but infected females in both moth types were smaller than their uninfected counterparts. Forewing lengths and dry weights of moderately,heavily infected females were most severely affected. 4,Despite high annual infection rates in parents, only a small percentage of offspring (second-instar larvae) that established feeding sites each spring were infected, indicating that high rates of horizontal transmission occurred annually throughout the larval period. 5,The present study indicates that whether N. fumiferanae infections are a debilitating sublethal factor in spruce budworm populations depends more on the disease load than on the overall incidence of infection. The potential importance of N. fumiferanae infections on various fitness parameters related to host dispersal is discussed. [source]

Horizontal transmission of Beauveria bassiana (Bals.) Vuill

Decline of hepatitis B carrier rate in vaccinated and unvaccinated subjects: Sixteen years after newborn vaccination program in Taiwan

JOURNAL OF MEDICAL VIROLOGY, Issue 4 2003
Hans Hsienhong Lin
Abstract Taiwan was an endemic area for hepatitis B virus (HBV) infection, and related liver diseases cause a significant drain of public resources. To control the endemic, a nation-wide newborn vaccination program was started in 1985. We reviewed the results of the annual survey for HBV surface antigen (HBsAg) performed in freshmen class of two high schools in Hualien, eastern Taiwan, from 1991 to 2001. A total of 10,194 students, most of them 15 years old, were tested for serum HBsAg using enzyme immunoassays. There is a significant trend (P,<,0.0001) of decreasing HBsAg carrier rate from 20.3 to 4.4% in males and 14.3% to 2.4% in females, respectively, over 11 years. The HBsAg carrier rate was 16.0,20.3% in students surveyed during 1991,1993 (born more than 6 years before the start of the national vaccination program), which decreased to 7.7,11.9% during 1994,1999 (born 1,6 years before the program). It further declined to 4.7% and 3.4% in 2000 and 2001 (born after the start of the program). The HBsAg carrier rate in male students was significantly higher than that in female students in most of the years. The HBV newborn vaccination program not only successfully prevented most of the perinatal transmission of HBV but also reduced horizontal transmission of HBV to children born up to 6 years before the start of the program. Also, the protection persisted for at least 15 years. J. Med. Virol. 69:471,474, 2003. © 2003 Wiley-Liss, Inc. [source]

Hepatitis B vaccine: Risks and benefits of universal neonatal vaccination

JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 3 2001
CR Macintyre
Abstract: Global eradication of hepatitis B, which has infected over 2000 million people worldwide, is an achievable goal. Hepatitis B vaccine is effective and safe, and is recommended in Australia as a four-dose childhood schedule commencing with a neonatal dose. A neonatal dose has a greater impact on carriage, the main reservoir of transmission, due to the inverse relationship of age and risk of chronic carriage. Universal vaccination is clearly cost-effective in countries of high hepatitis B endemicity but less so in countries of low endemicity. Other factors affecting the perceived benefits of universal vaccination in low-risk countries include the use of the preservative thiomersal in hepatitis B vaccines, and case reports of multiple sclerosis (MS) and unexplained fever in recipients. Careful epidemiological studies have failed to confirm any risk of MS or fever with the hepatitis B vaccine, which is now thiomersal-free. Other arguments against universal vaccination include ,unnecessary' vaccination of low-risk neonates. However, selective vaccination programmes targeting at-risk neonates are often poorly implemented and do not protect against horizontal transmission in early childhood. Universal vaccination, which is safe and effective, is the only practical means of achieving global eradication of hepatitis B. [source]

Myiasis as a risk factor for prion diseases in humans

JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 9 2006
O Lupi
Abstract Prion diseases are transmissible spongiform encephalopathies of humans and animals. The oral route is clearly associated with some prion diseases, according to the dissemination of bovine spongiform encephalopathy (BSE or mad cow disease) in cattle and kuru in humans. However, other prion diseases such as scrapie (in sheep) and chronic wasting disease (CWD) (in cervids) cannot be explained in this way and are probably more associated with a pattern of horizontal transmission in both domestic and wild animals. The skin and mucous membranes are a potential target for prion infections because keratinocytes and lymphocytes are susceptible to the abnormal infective isoform of the prion protein. Iatrogenic transmission of Creutzfeldt,Jakob disease (CJD) was also recognized after corneal transplants in humans and scrapie was successfully transmitted to mice after ocular instillation of infected brain tissue, confirming that these new routes could also be important in prion infections. Some ectoparasites have been proven to harbour prion rods in laboratory experiments. Prion rods were identified in both fly larvae and pupae; adult flies are also able to express prion proteins. The most common causes of myiasis in cattle and sheep, closely related animals with previous prion infections, are Hypoderma bovis and Oestrus ovis, respectively. Both species of flies present a life cycle very different from human myiasis, as they have a long contact with neurological structures, such as spinal canal and epidural fat, which are potentially rich in prion rods. Ophthalmomyiases in humans is commonly caused by both species of fly larvae worldwide, providing almost direct contact with the central nervous system (CNS). The high expression of the prion protein on the skin and mucosa and the severity of the inflammatory response to the larvae could readily increase the efficiency of transmission of prions in both animals and humans. [source]

The Textual Criticism of Middle English Manuscript Traditions: A Survey of Critical Issues in the Interpretation of Textual Data

LITERATURE COMPASS (ELECTRONIC), Issue 6 2009
Gavin Cole
This essay is intended to survey two broad issues which determine the use of textual data. The first is the underlying orientation towards the use of textual data and how this relates to critical evaluations of agency, authority and materiality. This essay surveys two broad orientations: (i) an essentially retrospective genetic orientation and, (ii) an orientation which focuses on the phenomenon of change. Both approaches are dependent on the ability to distinguish original readings from scribal readings, identify genetic relationships and account for acts of horizontal transmission. With this in mind, the second issue with which this essay is concerned is the importance of critical interpretation in the categorisation of textual data. This essay argues that textual criticism is a practical demonstration of the difficulties of interpretation and that no textual data ,has any real evidential value until it has been interpreted' (Patterson 90). [source]

Bacteriophage WO-B and Wolbachia in natural mosquito hosts: infection incidence, transmission mode and relative density

MOLECULAR ECOLOGY, Issue 9 2006
N. CHAUVATCHARIN
Abstract Bacteriophages of Wolbachia bacteria have been proposed as a potential transformation tool for genetically modifying mosquito vectors. In this study, we report the presence of the WO-B class of Wolbachia -associated phages among natural populations of several mosquito hosts. Eighty-eight percent (22/25) of Wolbachia -infected mosquito species surveyed were found to contain WO-B phages. WO-B phage orf7 sequence analysis suggested that a single strain of WO-B phage was found in most singly (23/24) or doubly (1/1) Wolbachia -infected mosquitoes. However, the single Wolbachia strain infecting Aedes perplexus was found to harbour at least two different WO-B phages. Phylogenetic analysis suggested that horizontal transmission of WO-B phages has occurred on an evolutionary scale between the Wolbachia residing in mosquitoes. On an ecological scale, a low trend of co-transmission occurred among specific WO-B phages within Wolbachia of each mosquito species. Assessment of the density of WO-B phage by real-time quantitative polymerase chain reaction (RTQ-PCR) revealed an average relative density of 7.76 × 105± 1.61 × 105 orf7 copies per individual mosquito for a single Wolbachia strain infecting mosquitoes, but a threefold higher density in the doubly Wolbachia-infected Aedes albopictus. However, the average combined density of WO-B phage(s) did not correlate with that of their Wolbachia hosts, which varied in different mosquito species. We also confirmed the presence of WO-B-like virus particles in the laboratory colony of Ae. albopictus (KLPP) morphologically, by transmission electron microscopy (TEM). The viral-like particles were detected after purification and filtration of Ae. albopictus ovary extract, suggesting that at least one WO-B-like phage is active (temperate) within the Wolbachia of this mosquito vector. Nevertheless, the idea of utilizing these bacteriophages as transformation vectors still needs more investigation and is likely to be unfeasible. [source]

Distribution of the bacterial symbiont Cardinium in arthropods

MOLECULAR ECOLOGY, Issue 7 2004
EINAT ZCHORI-FEIN
Abstract ,Candidatus Cardinium', a recently described bacterium from the Bacteroidetes group, is involved in diverse reproduction alterations of its arthropod hosts, including cytoplasmic incompatibility, parthenogenesis and feminization. To estimate the incidence rate of Cardinium and explore the limits of its host range, 99 insect and mite species were screened, using primers designed to amplify a portion of Cardinium 16S ribosomal DNA (rDNA). These arthropods were also screened for the presence of the better-known reproductive manipulator, Wolbachia. Six per cent of the species screened tested positive for Cardinium, compared with 24% positive for Wolbachia. Of the 85 insects screened, Cardinium was found in four parasitic wasp species and one armoured scale insect. Of the 14 mite species examined, one predatory mite was found to carry the symbiont. A phylogenetic analysis of all known Cardinium 16S rDNA sequences shows that distantly related arthropods can harbour closely related symbionts, a pattern typical of horizontal transmission. However, closely related Cardinium were found to cluster among closely related hosts, suggesting host specialization and horizontal transmission among closely related hosts. Finally, the primers used revealed the presence of a second lineage of Bacteroidetes symbionts, not related to Cardinium, in two insect species. This second symbiont lineage is closely allied with other arthropod symbionts, such as Blattabacterium, the primary symbionts of cockroaches, and male-killing symbionts of ladybird beetles. The combined data suggest the presence of a diverse assemblage of arthropod-associated Bacteroidetes bacteria that are likely to strongly influence their hosts' biology. [source]

Conjugation mediates transfer of the Ll.LtrB group II intron between different bacterial species

MOLECULAR MICROBIOLOGY, Issue 5 2004
Kamila Belhocine
Summary Some self-splicing group II introns (ribozymes) are mobile retroelements. These retroelements, which can insert themselves into cognate intronless alleles or ectopic sites by reverse splicing, are thought to be the evolutionary progenitors of the widely distributed eukaryotic spliceosomal introns. Lateral or horizontal transmission of introns (i.e. between species), although never experimentally demonstrated, is a well-accepted model for intron dispersal and evolution. Horizontal transfer of the ancestral bacterial group II introns may have contributed to the dispersal and wide distribution of spliceosomal introns present in modern eukaryotic genomes. Here, the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis was used as a model system to address the dissemination of introns in the bacterial kingdom. We report the first experimental demonstration of horizontal transfer of a group II intron. We show that the Ll.LtrB group II intron, originally discovered on an L. lactis conjugative plasmid (pRS01) and within a chromosomally located sex factor in L. lactis 712, invades new sites using both retrohoming and retrotransposition pathways after its transfer by conjugation. Ll.LtrB lateral transfer is shown among different L. lactis strains (intraspecies) (retrohoming and retrotransposition) and between L. lactis and Enterococcus faecalis (interspecies) (retrohoming). These results shed light on long-standing questions about intron evolution and propagation, and demonstrate that conjugation is one of the mechanisms by which group II introns are, and probably were, broadly disseminated between widely diverged organisms. [source]

Periodontitis lesions are the main source of salivary cytomegalovirus

MOLECULAR ORAL MICROBIOLOGY, Issue 4 2009
ahin
Background:, Herpesviruses play causal or cooperative roles in childhood infections, tumorigenesis, ulcerogenesis, and periodontitis. Saliva is a common vehicle of herpesvirus horizontal transmission, but the source of salivary herpesviruses remains obscure. To evaluate the significance of periodontal disease in shedding of oral herpesviruses, this study determined the genome-copy counts of human cytomegalovirus (HCMV) and Epstein,Barr virus (EBV) in whole saliva of subjects with periodontitis, gingivitis, or no natural teeth. Methods:, Whole saliva was collected from 14 periodontitis patients, 15 gingivitis patients and 13 complete denture wearers. The study subjects were systemically healthy and had not received periodontal treatment in the past 3 months. Real-time TaqMan polymerase chain reaction was used to determine the salivary load of HCMV and EBV. Results:, Salivary HCMV was detected in seven (50%) periodontitis patients, but not in any gingivitis or edentulous subjects (P < 0.001). Salivary EBV was detected in 11 (79%) periodontitis patients, in five (33%) gingivitis patients, and in seven (54%) edentulous subjects (P = 0.076). Salivary samples showed copy counts of HCMV in the range of 3.3 × 103,4.2 × 104/ml and of EBV in the range of 3.6 × 102,1.6 × 109/ml. Conclusions:, HCMV and EBV are commonly present in the saliva of periodontitis patients. Periodontitis lesions of systemically healthy subjects seem to constitute the main origin of salivary HCMV, but do not comprise the sole source of salivary EBV. [source]

Mycoviruses of filamentous fungi and their relevance to plant pathology

MOLECULAR PLANT PATHOLOGY, Issue 1 2009
MICHAEL N. PEARSON
SUMMARY Mycoviruses (fungal viruses) are reviewed with emphasis on plant pathogenic fungi. Based on the presence of virus-like particles and unencapsidated dsRNAs, mycoviruses are common in all major fungal groups. Over 80 mycovirus species have been officially recognized from ten virus families, but a paucity of nucleic acid sequence data makes assignment of many reported mycoviruses difficult. Although most of the particle types recognized to date are isometric, a variety of morphologies have been found and, additionally, many apparently unencapsidated dsRNAs have been reported. Until recently, most characterized mycoviruses have dsRNA genomes, but ssRNA mycoviruses now constitute about one-third of the total. Two hypotheses for the origin of mycoviruses of plant pathogens are discussed: the first that they are of unknown but ancient origin and have coevolved along with their hosts, the second that they have relatively recently moved from a fungal plant host into the fungus. Although mycoviruses are typically readily transmitted through asexual spores, transmission through sexual spores varies with the host fungus. Evidence for natural horizontal transmission has been found. Typically, mycoviruses are apparently symptomless (cryptic) but beneficial effects on the host fungus have been reported. Of more practical interest to plant pathologists are those viruses that confer a hypovirulent phenotype, and the scope for using such viruses as biocontrol agents is reviewed. New tools are being developed based on host genome studies that will help to address the intellectual challenge of understanding the fungal,virus interactions and the practical challenge of manipulating this relationship to develop novel biocontrol agents for important plant pathogens. [source]

The Occurrence and Ape-to-Ape Transmission of the Entodiniomorphid Ciliate Troglodytella abrassarti in Captive Gorillas

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2009
DAVID MODRÝ
ABSTRACT. Entodiniomorphid ciliates are often present in the colons of wild apes. In captive apes the infection tends to gradually disappear, with the exception of Troglodytella abrassarti. We used fecal examinations to screen the gorillas (Gorilla gorilla gorilla) in European (Czech Republic, UK) and Australian Zoos to explore the ape-to-ape transmission pattern of T. abrassarti. Gorillas from two out of three European Zoos were positive for T. abrassarti, while gorillas from the Australian Zoo were negative. We documented a horizontal transmission of T. abrassarti to a non-infected adult gorilla introduced into a Troglodytella -positive group in the Prague Zoo and traced the origin of the ciliate infection to the Paignton Zoo (UK) using serial fecal examinations. During this study, two infant gorillas born in the Prague Zoo (CZ) first became positive for T. abrassarti at the age of 9 mo. Ciliate morphology and the sequencing of the small subunit rRNA gene and the internal transcribed spacer rDNA spacer region revealed that T. abrassarti affects both captive gorillas and chimpanzees. We conclude that zoo transport plays a major role in the distribution of T. abrassarti among captive gorillas. [source]