Horizontal Transmission Routes Research Articles

Determination of the virulence of single nucleopolyhedrovirus occlusion bodies using a novel laser capture microdissection method.

Determination of the virulence of occlusion bodies (OBs), which are the horizontal transmission structures of nucleopolyhedroviruses (NPVs), is an important area of baculovirology. A method for inoculating an insect with an isolated OB was developed using Helicoverpa armigera nucleopolyhedrovirus (HearNPV) infection of second instar Helicoverpa armigera larvae as a model NPV-host pathosystem. In this novel method, laser capture microdissection (LCM) was used to directly catapult single OBs onto the surface of insect diet in bioassay containers. Since exposure via the natural oral horizontal transmission route of each larva to a single OB was established and not subject to chance variation, the method facilitated determination of the insect mortality rate (4.8%) associated with exposure to single HearNPV OBs. Droplet feeding bioassays confirmed that the novel method did not reduce OB virulence. The LCM method sets a foundation for virulence and genetic diversity studies based on single NPV OBs.

Management of mother–newborn dyads in the COVID-19 era

Management of mother–newborn dyads in the COVID-19 era

The Pathogen Profile of a Honey Bee Queen Does Not Reflect That of Her Workers.

Throughout a honey bee queen’s lifetime, she is tended to by her worker daughters, who feed and groom her. Such interactions provide possible horizontal transmission routes for pathogens from the workers to the queen, and as such a queen’s pathogen profile may be representative of the workers within a colony. To explore this further, we investigated known honey bee pathogen co-occurrence, as well as pathogen transmission from workers to queens. Queens from 42 colonies were removed from their source hives and exchanged into a second, unrelated foster colony. Worker samples were taken from the source colony on the day of queen exchange and the queens were collected 24 days after introduction. All samples were screened for Nosema spp., Trypanosome spp., acute bee paralysis virus (ABPV), black queen cell virus (BQCV), chronic bee paralysis virus (CBPV), Israeli acute paralysis virus (IAPV), Lake Sinai virus (LSV), and deformed wing virus master variants (DWV-A, B, and C) using RT-qPCR. The data show that LSV, Nosema, and DWV-B were the most abundant pathogens in colonies. All workers (n = 42) were LSV-positive, 88% were Nosema-positive, whilst pathogen loads were low (<1 × 106 genome equivalents per pooled worker sample). All queens (n = 39) were negative for both LSV and Nosema. We found no evidence of DWV transmission occurring from worker to queen when comparing queens to foster colonies, despite DWV being present in both queens and workers. Honey bee pathogen presence and diversity in queens cannot be revealed from screening workers, nor were pathogens successfully transmitted to the queen.

Hepatitis B Profile in Adolescent Donors

Hepatitis B is a world health problem, including in Indonesia. Hepatitis B is an inflammatory liver disease caused by the Hepatitis B virus. Blood transfusions, which are known to save lives, are one of the main routes of horizontal HBV transmission that often occurs. Reducing the potential for transmission of infectious infections through blood transfusion (IMLTD) can be done by carrying out a matched screening test or screening to detect antigens or antibodies against the disease. The screening process for Hepatitis B infection at various UTDs in Indonesia uses reactivity checks against HBsAg. The test used to detect Hepatitis B is the HBsAg examination using the Diasorin Murex ELISA (Enzyme Linked Immunosorbent Assay) method. This study provides an overview of Hepatitis B in adolescent donors. The frequency of reactive hepatitis B is quite low with the total number of donors as many as 196 people from September to November 2020. With the number of reactive as many as 3 samples (20%) with different blood groups. Seen from the age interval range 17-20 years with the number of donors voluntary sex that dominated were women. sample of teenage donors was positive 3 samples (20%) of the 196 donors who passed the screening.

Mycoviruses in Biological Control: From Basic Research to Field Implementation.

Mycoviruses from plant pathogens can induce hypovirulence (reduced virulence) in their host fungi and have gained considerable attention as potential biocontrol tools. An increasing number of mycoviruses that induce fungal hypovirulence, from a wide variety of taxonomic groups, are currently being reported. Successful application of these viruses in disease management is greatly dependent on their ability to spread in the natural populations of the pathogen. Mycoviruses generally lack extracellular routes of transmission. Hyphal anastomosis is the main route of horizontal mycovirus transmission to other isolates, and conidia of vertical transmission to the progeny. Transmission efficiencies are influenced by both the fungal host and the infecting virus. Interestingly, artificial transfection methods have shown that potential biocontrol mycoviruses often have the ability to infect a variety of fungi. This expands their possible use to the control of pathogens others than those where they were identified. Mycovirus research is also focused on gaining insights into their complex molecular biology and the molecular bases of fungus-virus interactions. This knowledge could be exploited to manipulate the mycovirus and/or the host and generate combinations with enhanced properties in biological control. Finally, when exploring the use of mycoviruses in field conditions, the pathogen life style and the characteristics of the disease and crops affected will deeply impact the specific challenges to overcome, and the development of biocontrol formulations and delivery methods.

Spatio-temporal distribution of Spiroplasma infections in the tsetse fly (Glossina fuscipes fuscipes) in northern Uganda.

Tsetse flies (Glossina spp.) are vectors of parasitic trypanosomes, which cause human (HAT) and animal African trypanosomiasis (AAT) in sub-Saharan Africa. In Uganda, Glossina fuscipes fuscipes (Gff) is the main vector of HAT, where it transmits Gambiense disease in the northwest and Rhodesiense disease in central, southeast and western regions. Endosymbionts can influence transmission efficiency of parasites through their insect vectors via conferring a protective effect against the parasite. It is known that the bacterium Spiroplasma is capable of protecting its Drosophila host from infection with a parasitic nematode. This endosymbiont can also impact its host’s population structure via altering host reproductive traits. Here, we used field collections across 26 different Gff sampling sites in northern and western Uganda to investigate the association of Spiroplasma with geographic origin, seasonal conditions, Gff genetic background and sex, and trypanosome infection status. We also investigated the influence of Spiroplasma on Gff vector competence to trypanosome infections under laboratory conditions. Generalized linear models (GLM) showed that Spiroplasma probability was correlated with the geographic origin of Gff host and with the season of collection, with higher prevalence found in flies within the Albert Nile (0.42 vs 0.16) and Achwa River (0.36 vs 0.08) watersheds and with higher prevalence detected in flies collected in the intermediate than wet season. In contrast, there was no significant correlation of Spiroplasma prevalence with Gff host genetic background or sex once geographic origin was accounted for in generalized linear models. Additionally, we found a potential negative correlation of Spiroplasma with trypanosome infection, with only 2% of Spiroplasma infected flies harboring trypanosome co-infections. We also found that in a laboratory line of Gff, parasitic trypanosomes are less likely to colonize the midgut in individuals that harbor Spiroplasma infection. These results indicate that Spiroplasma infections in tsetse may be maintained by not only maternal but also via horizontal transmission routes, and Spiroplasma infections may also have important effects on trypanosome transmission efficiency of the host tsetse. Potential functional effects of Spiroplasma infection in Gff could have impacts on vector control approaches to reduce trypanosome infections.

Microsporidian infections in the species complex Gammarus roeselii (Amphipoda) over its geographical range: evidence for both host\u2013parasite co-diversification and recent host shifts

BackgroundMicrosporidians are obligate endoparasites infecting taxonomically diverse hosts. Both vertical (from mother to eggs) and horizontal (between conspecifics or between species) transmission routes are known. While the former may promote co-speciation and host-specificity, the latter may promote shifts between host species. Among aquatic arthropods, freshwater amphipod crustaceans are hosts for many microsporidian species. However, despite numerous studies, no general pattern emerged about host specificity and co-diversification. In south-eastern Europe, the gammarid Gammarus roeselii is composed of 13 cryptic lineages of Miocene to Pleistocene age but few genotypes of one lineage have spread postglacially throughout north-western Europe. Based on nearly 100 sampling sites covering its entire range, we aim to: (i) explore the microsporidian diversity present in G. roeselii and their phylogenetic relationships, especially in relation to the parasites infecting other Gammaridae; (ii) test if the host phylogeographical history might have impacted host–parasite association (e.g. co-diversifications or recent host shifts from local fauna).MethodsWe used part of the small subunit rRNA gene as source of sequences to identify and determine the phylogenetic position of the microsporidian taxa infecting G. roeselii.ResultsMicrosporidian diversity was high in G. roeselii with 24 detected haplogroups, clustered into 18 species-level taxa. Ten microsporidian species were rare, infecting a few individual hosts in a few populations, and were mostly phylogenetically related to parasites from other amphipods or various crustaceans. Other microsporidians were represented by widespread genera with high prevalence: Nosema, Cucumispora and Dictyocoela. Two contrasting host association patterns could be observed. First, two vertically transmitted microsporidian species, Nosema granulosis and Dictyocoela roeselum, share the pattern of infecting G. roeselii over most of its range and are specific to this host suggesting the co-diversification scenario. This pattern contrasted with that of Dictyocoela muelleri, the three species of Cucumispora, and the rare parasites, present only in the recently colonised region by the host. These patterns suggest recent acquisitions from local host species, after the recent spread of G. roeselii.ConclusionsMicrosporidians infecting G. roeselii revealed two scenarios of host–parasite associations: (i) ancient associations with vertically transmitted parasites that probably co-diversified with their hosts, and (ii) host shifts from local host species, after the postglacial spread of G. roeselii.

Experimental Infection of Sand Flies by Massilia Virus and Viral Transmission by Co-Feeding on Sugar Meal.

Background: Massilia virus (MASV) is a phlebovirus isolated from Phlebotomus perniciosus in various regions of southwestern Europe. It is closely related to human pathogens such as Toscana virus and sandfly fever Naples virus. The natural cycle of phleboviruses is poorly understood. Indeed, experimental studies demonstrate that transovarial and sexual transmission are not efficient enough for the maintenance of the virus in nature and to date there is no convincing evidence that a species of vertebrates is the reservoir of the virus. Here, we studied various transmission routes of MASV taking advantage of experimental colonies representing different species of sand flies. Methodology/Principal findings: In P. perniciosus, four sources of infection were compared: (i) Virus-seeded larval food to the first instar larvae (L1), or (ii) to the fourth instar larvae (L4), (iii) virus-seeded blood meal to adult females, and (iv) virus-seeded sugar meal to adults of both sexes. From 875 adults emerged from infected L1 and L4, only three were positive. In females infected by bloodmeal the infection rate was high before defecation, then it decreased drastically; MASV RNA was detected in only 5 out of 27 post-defecation. Surprisingly, the most efficient route of infection was observed after intake of virus-seeded sugar meal: 72% of females (79/110) and 52% of males (51/99) were found to be MASV RNA-positive. In addition, MASV-infected sandflies regurgitated virus particules into the sugar drop and MASV RNA was detectable in this drop for at least 24 h after regurgitation. MASV RNA was detected in about one third of the P. perniciosus exposed to this sugar drop contaminated by regurgitation. Sugar meal infection was also tested with six other species of sand flies. In males, there were no significant differences in infection rates when compared to P. perniciosus. In females, most species tested showed high infection rate at the beginning but then significant gradual decrease in infection rate during the experiment. Conclusions/Significance: We present the first description of arboviral infection of a dipteran vector using sugar meal. In all seven sand fly species tested, MASV was detected for two weeks post-infection. Our results showed that MASV can be transmitted between P. perniciosus either through co-feeding or via an infected sugar source such as plant sap. These newly described routes of horizontal transmission may play an important role in the circulation of phleboviruses in nature.

Occurrence of deformed wing virus variants in the stingless bee Melipona subnitida and honey bee Apis mellifera populations in Brazil.

The global spread of the parasitic Varroa mite has introduced a new bee to the bee horizontal transmission route for several RNA viruses that bypasses existing barriers in honey bees. From among these viruses, deformed wing virus (DWV) is now among the most widespread insect pathogens in the world. Brazilian stingless bees are a diverse group often managed in close proximity to honey bees. Therefore, we investigated the prevalence and load of DWV in 21 stingless bee (Melipona subnitida) and 26 honey bee (Apis mellifera) colonies from Brazil. DWV was detected in all colonies with DWV-A and DWV-C dominating in M. subnitida, while DWV-A dominated in A. mellifera. Average total viral loads per bee were 8.8E+07 and 6.3E+07 in M. subnitida and A. mellifera, respectively, which are much lower than DWV levels (>1E+10) found in honey bees in the northern hemisphere. In colonies introduced 30 years ago to the remote island of Fernando de Noronha, the DWV load was low (<1E+03) in honey bees but we detected higher loads (1.6E+08) in all M. subnitida colonies on the island. This may suggest that minimal, if any, viral transmission of DWV from stingless bees to honey bees has occurred on this island. Furthermore, the ubiquitous presence of the DWV-C variant in M. subnitida colonies, and its rarity in A. mellifera, may again suggest that limited viral exchange between these two species is occurring.

Characterization of the hepatitis B virus DNA detected in urine of chronic hepatitis B patients

BackgroundDetection of human hepatitis B virus (HBV) DNA in the urine of patients with chronic hepatitis B infection (CHB) has been reported previously, suggesting urine could provide a potential route of horizontal HBV transmission. However, it is not clear whether the HBV DNA detected in urine is indeed full-length, infectious viral DNA. The aim of this study is to assess the potential infectivity of urine from patients with CHB and to correlate HBV DNA detection in urine with clinical parameters, such as serum viral load and HBeAg status.MethodsUrine from 60 CHB patients with serum viral loads ranging from undetectable to 108 IU/mL were analyzed for HBV DNA and serum immune markers. HBV DNA was detected from total urine DNA and size-fractionated urine DNA (separated into ≤1 kb and > 1 kb fractions) by PCR analysis of six regions of the HBV genome.ResultsTwenty-seven of 59 (45.7%) patients with HBV serum viral load (≥20 IU/mL) contained at least 20 copies per mL of fragmented HBV DNA in urine detected in at least 1 of the 6 PCR assay regions. Only one patient contained HBV DNA detected by all six regions, and was found to have evidence of blood in the urine. Sixteen of 25 urine samples with high viral load (> 105 IU/mL) and 11 of 34 urine samples with low viral load (< 105 IU/mL) contained detectable HBV DNA. Twelve of 27 (44.44%) patients with detectable HBV DNA in urine were HBeAg positive, and only 5 of these HBeAg positive patients were in the group of 33 (15.15%) patients with no detectable HBV DNA in urine. By Fishers’ exact test, HBV DNA in urine is significantly associated with high serum viral load (P = 0.0197) and HBeAg (P = 0.0203).ConclusionsWe conclude that urine from CHB patients with healthy kidney function should not contain full-length HBV DNA, and therefore should not be infectious.

Exploring the role of genome and structural ions in preventing viral capsid collapse during dehydration

Even though viruses evolve mainly in liquid milieu, their horizontal transmission routes often include episodes of dry environment. Along their life cycle, some insect viruses, such as viruses from the Dicistroviridae family, withstand dehydrated conditions with presently unknown consequences to their structural stability. Here, we use atomic force microscopy to monitor the structural changes of viral particles of Triatoma virus (TrV) after desiccation. Our results demonstrate that TrV capsids preserve their genome inside, conserving their height after exposure to dehydrating conditions, which is in stark contrast with other viruses that expel their genome when desiccated. Moreover, empty capsids (without genome) resulted in collapsed particles after desiccation. We also explored the role of structural ions in the dehydration process of the virions (capsid containing genome) by chelating the accessible cations from the external solvent milieu. We observed that ion suppression helps to keep the virus height upon desiccation. Our results show that under drying conditions, the genome of TrV prevents the capsid from collapsing during dehydration, while the structural ions are responsible for promoting solvent exchange through the virion wall.

Extended-Spectrum Beta-Lactamase-/AmpC Beta-Lactamase-Producing Enterobacteriaceae in Broiler Farms: Transmission Dynamics at Farm Level.

The occurrence of extended-spectrum beta-lactamase- (ESBL) and/or AmpC beta-lactamase- (AmpC) producing Enterobacteriaceae in livestock, especially in broiler fattening flocks, has been demonstrated in previous studies. Nevertheless, data on transmission routes of these resistant bacteria into the fattening farms are rare. Therefore, seven broiler fattening flocks were investigated for the occurrence of ESBL-/AmpC-producing Enterobacteriaceae during the course of the fattening period with the special focus on horizontal transmission routes. ESBL-/AmpC-producing Enterobacteriaceae from both individual animals and their housing environment were isolated at different time points and the housing environment was even sampled before the arrival of the chickens. All obtained ESBL-/AmpC-producing Enterobacteriaceae were examined for their bacterial species, Escherichia coli phylogroup, and occurrence of resistance genes. Selected isolates were further analyzed via whole-genome sequencing. All seven investigated flocks were tested positive for ESBL-/AmpC-producing Enterobacteriaceae with widely varying prevalence between the flocks. In one flock, the ESBL-/AmpC-producing Enterobacteriaceae were already detected in the housing environment before the arrival of the animals. In general, among the different types of ESBL-/AmpC-producing Enterobacteriaceae determined E. coli harboring a blaCMY-2 gene was the most frequent. Using whole-genome analyses we observed a horizontal transmission of ESBL-/AmpC-producing Enterobacteriaceae through contaminated housing environment as two flocks consecutively fattened in the same farm harbored closely related ESBL-producing isolates. This demonstrates the influence of a previous fattened flock on the ESBL-/AmpC-status of a following broiler flock and, therefore, the importance of hygiene measures on farm level.

Numerical solution of nonlinear fractional SEIR epidemic model by using Haar wavelets

Throughout the world people have been suffering from the infectious diseases like Rubella, Herpes Simplex, Hepatitis B, Chagas, and HIV(AIDS) which have been causing loss of millions of lives and billions of rupees in cure. These diseases get transmitted via both horizontal and vertical transmission routes. One among the most recent mathematical models for modeling the above infectious diseases is fractional order nonlinear SEIR model [3] with non-constant population. In this paper, we have proposed a computationally faster and simpler numerical method based on Haar wavelets to solve the SEIR model. The error bounds have also been derived and validated.

Neospora caninum and Bovine Neosporosis: Current Vaccine Research

Neospora caninum, a tissue cyst-forming parasite, is the causative agent of bovine neosporosis. It is considered to be one of the most important transmissible causes of reproductive failure in cattle; abortion and neonatal mortality result in significant economic losses within the cattle industry worldwide. The balance between acute (mediated by the tachyzoite stage) and persistent (mediated by the bradyzoite stage) phases of the infection is influenced by the immune status of the animal, and for pregnant cows (the intermediate host) immune status is critical for transplacental (i.e. vertical) transmission of the parasite and associated disease outcomes. The horizontal route of transmission from the definitive host, the dog, occurs via ingestion of oocysts containing sporozoites, and plays a minor but important role in transmission of the infection to cattle. Despite the importance of this disease, there is no vaccine or treatment available currently, and at the present the only control measure to reduce the impact of disease is informed management on the farm. The development of vaccines, targeting key biological processes such as invasion and persistent infection, is needed urgently for the control of this widespread parasite.

The transovarial transmission in the dynamics of dengue infection: Epidemiological implications and thresholds

The anthropophilic and peridomestic female mosquito Aedes aegyptibites humans to suck blood to maturate fertilized eggs, during which dengue virus can be spread between mosquito and human populations. Besides this route of transmission, there is a possibility of dengue virus being passed directly to offspring through transovarial (or vertical) transmission. The effects of both horizontal and transovarial transmission routes on the dengue virus transmission are assessed by mathematical modeling. From the model, the reproduction number is obtained and the contribution of transovarial transmission is evaluated for different levels of horizontal transmission. Notably, the transovarial transmission plays an important role in dengue spread when the reproduction number is near one. Another threshold parameter arises, which is the product of the fractions of the susceptible populations of humans and mosquitoes. Interestingly, these two threshold parameters can be obtained from three different approaches: the spectral radius of the next generation matrix, the Routh–Hurwitz criteria and M-matrix theory.

Faithful vertical transmission but ineffective horizontal transmission of bacterial endosymbionts during sexual reproduction of the black bean aphid, Aphis fabae

1. Insects are commonly infected with bacterial endosymbionts. In addition to the costs and benefits associated with harbouring these symbionts, their rates of vertical and horizontal transmission are important determinants of symbiont prevalence.2. Aphids are cyclical parthenogens and show virtually perfect maternal transmission of endosymbionts during asexual reproduction. Less clear is the role of the annual sexual generation, during which overwintering eggs are produced. Data from pea aphids (Acyrthosiphon pisum Harris) suggest that maternal transmission failures and horizontal transmission via males may occur under sexual reproduction at least occasionally. No such data exist for other aphid species.3. In the present study, the rates of maternal and paternal transmission of facultative endosymbionts during sexual reproduction in the black bean aphid, Aphis fabae (Scopoli) were examined. Crosses were performed between clones infected with Hamiltonella defensa, clones infected with Regiella insecticola and clones without facultative endosymbionts, and eggs were overwintered under three different conditions.4. Only one of 205 offspring from crosses testing for maternal transmission failed to inherit the symbiont present in the maternal clone, and in crosses testing for horizontal transmission, only one of 412 offspring acquired a facultative symbiont from the father.5. These results show that in A. fabae, maternal transmission of H. defensa and R. insecticola is extremely reliable also during sexual reproduction, indicating that maternal transmission failures are unlikely to exert a significant influence on frequencies of infection in the field. Paternal transmission of endosymbionts was exceedingly rare, suggesting that this route of horizontal transmission may be less important than hitherto assumed.

Vertical transmission of hepatitis C virus-like non-primate hepacivirus in horses.

Non-primate hepacivirus (NPHV), a recently discovered hepatotropic virus infecting horses, is phylogenetically the closest known homologue of hepatitis C virus (HCV). The main route for acquiring HCV infection in childhood is vertical transmission. However, nothing is known about the natural mode of transmission for NPHV. To investigate the possibility of vertically transmitted NPHV infection in horses, 20 Thoroughbred broodmares and their foals were monitored during foaling season 2015 until 6 months post-partum. Prepartal serum was taken from the mares, and during foaling umbilical cord blood and colostrum samples were collected. Postnatal serum samples were taken from the foals after delivery. In addition, serum was taken at 3 and 6 months after foaling from all mares and foals. Samples were analysed for the presence of NPHV RNA by quantitative real-time PCR and for the presence of anti-NPHV NS3 antibodies by luciferase immunoprecipitation system. Identified NPHV isolates were sequenced and phylogenetic analysis of the viral glycoproteins was used to track the course of naturally occurring infections and the circulation of distinct isolates within the herd. At parturition, 16 mares were seropositive, including four viraemic mares. Vertical transmission occurred in one of these four mare-foal pairs. Interestingly, NPHV isolates of newly infected foals and mares after 3 and 6 months cluster in their respective pasture herds suggesting another horizontal route of transmission.

On-site measurement of tracer gas transmission between horizontal adjacent flats in residential building and cross-infection risk assessment

Airborne transmission is a main spread mode of respiratory infectious diseases, whose frequent epidemic has brought serious social burden. Identifying possible routes of the airborne transmission and predicting the potential infection risk are meaningful for infectious disease control. In the present study, an internal spread route between horizontal adjacent flats induced by air infiltration was investigated. On-site measurements were conducted, and tracer gas technique was employed. Two measurement scenarios, closed window mode and open window mode, were compared. Using the calculated air change rate and mass fraction, the cross-infection risk was estimated using the Wells–Riley model. It found that tracer gas concentrations in receptor rooms are one order lower than the source room, and the infection risks are also one order lower. Opening windows results in larger air change rate on the one hand, but higher mass fraction on the other hand. Higher mass fraction not necessarily results in higher infection risk as the pathogen concentration in the source room is reduced by the higher air change rate. In the present study, opening windows could significantly reduce the infection risk of the index room but slightly reduce the risks in receptor rooms. The mass fraction of air originated from the index room to the receptor units could be 0.28 and the relative cross-infection risk through the internal transmission route could be 9%, which are higher than the external spread through single-sided window flush. The study implicates that the horizontal transmission route induced by air infiltration should not be underestimated.

Viral Transmission Dynamics at Single-Cell Resolution Reveal Transiently Immune Subpopulations Caused by a Carrier State Association.

Monitoring the complex transmission dynamics of a bacterial virus (temperate phage P22) throughout a population of its host (Salmonella Typhimurium) at single cell resolution revealed the unexpected existence of a transiently immune subpopulation of host cells that emerged from peculiarities preceding the process of lysogenization. More specifically, an infection event ultimately leading to a lysogen first yielded a phage carrier cell harboring a polarly tethered P22 episome. Upon subsequent division, the daughter cell inheriting this episome became lysogenized by an integration event yielding a prophage, while the other daughter cell became P22-free. However, since the phage carrier cell was shown to overproduce immunity factors that are cytoplasmically inherited by the P22-free daughter cell and further passed down to its siblings, a transiently resistant subpopulation was generated that upon dilution of these immunity factors again became susceptible to P22 infection. The iterative emergence and infection of transiently resistant subpopulations suggests a new bet-hedging strategy by which viruses could manage to sustain both vertical and horizontal transmission routes throughout an infected population without compromising a stable co-existence with their host.

‘Candidatus phytoplasma solani’ genotypes associated with potato stolbur in Serbia and the role of Hyalesthes obsoletus and Reptalus panzeri (hemiptera, cixiidae) as natural vectors

A progressive spread of stolbur-associated symptoms observed in potato fields in Serbia over the past few years initiated the study on disease epidemiology and transmission pathways performed during 2013 and 2014. Inspection of potato fields on 12 localities in northern Serbia revealed high incidence (60 % of symptomatic plants) and wide dispersal (100 % of inspected localities) of ‘Candidatus Phytoplasma solani’. A qualitative analysis of Auchenorrhyncha fauna in affected potato fields identified 16 species, however only Hyalesthes obsoletus, Reptalus panzeri and R. quinquecostatus tested positive for ‘Ca. P. solani’. Multilocus typing of strains associated with field collected potato plants and insects had been performed to identify the propagation scenario underlying the threatening epidemics. Combined analyses of the tuf, stamp and vmp1 genes detected ten genotypes, seven of which were shared by the potato plants and insects, confirming their interaction, with no clear species-specific association of certain ‘Ca. P. solani’ genotypes with plausible insect vectors. Semi- field experiments with naturally ‘Ca. P. solani’-infected H. obsoletus and R. panzeri confirmed the ability of both species to successfully transmit the pathogen to potato plants and induce symptoms characteristic of stolbur disease. The third putative vector R. quinquecostatus shared genotypes of ‘Ca. P. solani’ with potato plants and other two cixiids, and though not tested in this study should not be ruled out as a potential vector. Our study revealed rather complex epidemiology of potato stolbur in Serbia involving several possible routes of horizontal transmission and provided experimental evidence for two natural planthopper vectors.