Revealing an Iranian Isolate of Tomato Brown Rugose Fruit Virus: Complete Genome Analysis and Mechanical Transmission

An analysis of the complete genome sequence of a novel isolate of tomato brown rugose fruit virus (ToBRFV) obtained from tomatoes in Iran and named ToBRFV-Ir is presented in this study. Comprehensive phylogenetic analysis utilizing key viral proteins, including 126 KDa, 183 KDa, movement protein (MP), and coat protein (CP), as well as the complete genome sequence, classified ToBRFV-Ir and 65 isolates from GenBank into three distinct clades. Notably, genetic diversity assessment revealed relatively low variability among the isolates, irrespective of their geographical or clade affiliation. Natural selection analysis based on the complete genome sequence showed that dN/dS values were consistently <1, indicating the prevailing role of negative selection across all populations. Analyses using the Recombination Detection Program and SplitsTree found no evidence of recombination events or signals in the complete genome sequence of the tested isolates. Thus, these results suggest that the genetic composition of ToBRFV remains stable without significant genetic exchange or recombination events occurring. A simple arithmetic comparison of the patristic distances and dates suggested that the time to the most recent common ancestor (TMRCA) of the ToBRFV populations is approximately 0.8 up to 2.7 with the closest tobamoviruses. An evolutionary study of the tested isolates from various countries based on the complete genome suggests Peruvian ancestry. The ToBRF-Ir isolate was successfully transmitted through mechanical inoculations to Solanum lycopersicum and Nicotiana rustica. These findings shed light on the genetic dynamics and transmission mechanisms of ToBRFV, providing valuable insights into its molecular characteristics and potential spread among susceptible plant species.

Epidemiology and Transmission of Theileria orientalis in Australasia

Oriental theileriosis, a disease primarily impacting cattle is caused by an apicomplexan hemoprotozoan parasite, Theileria orientalis. It has now become established in the Australasia region. The organism was long considered a benign cause of persistent infections; however, an increase in clinical outbreaks since 2006 in the eastern Australian states and New Zealand was associated with the identification of the pathogenic Ikeda (Type 2) and Chitose (Type 1) genotypes. Unlike the pathogenic T. parva and T. annulate, which target leucocytes, clinical manifestation with T. orientalis is due to its effects on erythrocytes, with the infection sometimes designated as Theileria associated bovine anemia (TABA). In Australia and New Zealand, the tick Haemaphysalis longicornis is the principal vector, though other Haemaphysalis species are also likely vectors. The endemic status of infection with pathogenic genotypes in areas with low or absent tick populations is an apparent paradox that may be attributable to alternative modes of transmission, such as mechanical transmission by hematophagous insects (lice, mosquitoes, and biting flies), vertical transmission, and transmission via iatrogenic means. This review addresses the evidence for the different modes of transmission of T. orientalis with particular focus on the reported and potential vectors in Australasia.

Potential mosquito vector attraction to- and feeding preferences for pigs in Romanian backyard farms

Introduction

Mosquitoes either biologically or mechanically transmit various vector-borne pathogens affecting pigs. Mosquito species display a wide variety of host preference, as well as host attraction and behaviours. Mosquito species attraction rates to- and feeding rates on pigs or other potential hosts, as well as the seasonal abundance of the mosquito species affects their pathogen transmission potential.

Methods

We caught mosquitoes in experimental cages containing pigs situated in Romanian backyard farms. The host species of blood meals were identified with PCR and sequencing.

Results

High feeding preferences for pigs were observed in Aedes vexans (90%), Anopheles maculipennis (80%) and Culiseta annulata (72.7%). However, due to a high abundance in the traps, Culex pipiens/torrentium were responsible for 37.9% of all mosquito bites on pigs in the Romanian backyards, despite low feeding rates on pigs in the cages (18.6%). We also found that other predominantly ornithophilic mosquito species, as well as mosquitoes that are already carrying a blood meal from a different (mammalian) host, were attracted to backyard pigs or their enclosure.

Discussion

These results indicate that viraemic blood carrying, for instance, African swine fever virus, West-Nile virus or Japanese encephalitis virus could be introduced to these backyard pig farms and therefore cause an infection, either through subsequent feeding, via ingestion by the pig or by environmental contamination.

Possibility of mechanical transmission of parapoxvirus by houseflies (Musca domestica) on cattle and sheep farms

Parapoxvirus (PPV) causes papular stomatitis and contagious pustular dermatitis in ruminants worldwide. The virus is generally transmitted through close contact with skin lesions containing PPV in infected animals and indirectly through PPV-contaminated materials. PPV-infected animals frequently do not show clinical signs and the route of PPV transmission is sometimes unclear. In this study, the possibility of mechanical transmission of PPV by houseflies (Musca domestica) was investigated using polymerase chain reaction (PCR) gene surveillance. Samples were collected from cattle, sheep, barn environments, direct wash solution of the body surface of houseflies, and indirect wash solution of the body surface and feces of the flies. Bovine papular stomatitis virus, pseudocowpox virus, and orf virus were detected in the oral cavity and body surface of cattle and sheep without clinical signs of PPV infection or barn environments; PPV was considered to have been retained on the farm. PPVs were also detected in the direct wash solution of the body surface of houseflies, and the indirect wash solution of the body surface and feces of the flies. The viral sequence determined from the indirect wash solution of the body surface and feces of the flies was identical to that determined from the body surface of cattle and barns. These results suggested that houseflies may mechanically transmit PPV to both cattle and sheep.

No Evidence of SARS-CoV-2 Among Flies or Cockroaches in Households Where COVID-19 Positive Cases Resided

Flies and other arthropods mechanically transmit multiple pathogens and a recent experimental study demonstrated house flies, Musca domestica L. (Diptera: Muscidae), can mechanically transmit SARS-CoV-2. The purpose of this study was to explore the possibility of mechanical transmission of SARS-CoV-2 by domestic insects and their potential as a xenosurveillance tool for detection of the virus. Flies were trapped in homes where at least one confirmed human COVID-19 case(s) resided using sticky and liquid-baited fly traps placed inside and outside the home in the Texas counties of Brazos, Bell, and Montgomery, from June to September 2020. Flies from sticky traps were identified, pooled by taxa, homogenized, and tested for the presence of SARS-CoV-2 RNA using quantitative reverse transcription PCR (RT-qPCR). Liquid traps were drained, and the collected fluid similarly tested after RNA concentration. We processed the contents of 133 insect traps from 40 homes, which contained over 1,345 individual insects of 11 different Diptera families and Blattodea. These individuals were grouped into 243 pools, and all tested negative for SARS-CoV-2 RNA. Fourteen traps in seven homes were deployed on the day that cat or dog samples tested positive for SARS-CoV-2 RNA by nasal, oral, body, or rectal samples. This study presents evidence that biting and nonbiting flies and cockroaches (Blattodea) are not likely to contribute to mechanical transmission of SARS-CoV-2 or be useful in xenosurveillance for SARS-CoV-2.

Research priorities to fill knowledge gaps in the control of African swine fever: possible transmission of African swine fever virus by vectors

The European Commission requested that EFSA provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: (i) the patterns of seasonality of African Swine Fever (ASF) in wild boar and domestic pigs in the EU; (ii) the epidemiology of ASF in wild boar; (iii) survival of ASF virus (ASFV) in the environment and (iv) transmission of ASFV by vectors. In this Scientific Opinion, the fourth research domain on ASFV transmission by vectors is addressed. Eleven research objectives were proposed by the EFSA working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the 11 research objectives, six were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time-frame study (< 1 year); (5) the novelty of the study and (6) if it was a priority for risk managers. The prioritised research objectives were: (I) Studies on the potential vector fauna at the pig-wild boar interface and the feeding preference of blood-feeding potential vectors in ASF-affected areas; (II) Assessment of the efficacy of insect screens on indoor/outdoor pig holdings to prevent the entry of blood-sucking vectors (i.e. Stomoxys) in ASF endemic areas; (III) Assess the role of mechanical vectors in the virus transmission in ASF-affected areas; (IV) Distribution of the potential mechanical transmission vectors in ASF-affected areas of the EU; (V) ASFV transmission by synanthropic birds; and (VI) Assessment on the presence/absence of the soft tick Ornithodoros erraticus in ASF-affected areas in Europe. For each of the selected research objectives, a research protocol has been proposed considering the potential impact on ASF management and the period of 1 year for the research activities.

The Potential Risk of Plant-Virus Disease Initiation by Infected Tomatoes

During 2019, tomato fruits showing viral-like symptoms of marbled yellow spots were abundant in Israel. The new symptoms were distinctive from those typical of tomato brown rugose fruit virus (ToBRFV) infection but resembled symptoms of pepino mosaic virus (PepMV) infection. RT-PCR analysis and the serological tests (enzyme linked immunosorbent assay, western blot and in situ immunofluorescence) revealed and confirmed the presence of both the tobamovirus ToBRFV and the potexvirus PepMV in the symptomatic fruits. A mixture of rod-like and filamentous particles, characteristic of viruses belonging to tobamovirus and potexvirus genera, was visualized by transmission electron microscopy of the tomato fruit viral extract. Sanger sequencing of amplified PepMV-coat protein gene segments showed ~98% sequence identity to the Chilean (CH2)-strain. In a biological assay testing the contribution of traded infected tomatoes to the establishment of tomato plant disease, we applied direct and indirect inoculation modes using Tm-2²-resistant tomato plants. The results, assessed by disease symptom development along with serological and molecular analyses, showed that the ToBRFV and PepMV co-infected fruits were an effective inoculum source for disease spread only when fruits were damaged. Importantly, intact fruits did not spread the viral disease. These results added a new factor to disease epidemiology of these viruses.

Mechanical Transmission of Lumpy Skin Disease Virus by Stomoxys Spp (Stomoxys Calsitrans, Stomoxys Sitiens, Stomoxys Indica), Diptera: Muscidae

Summary

Lumpy skin disease (LSD) is an emerging disease in Kazakhstan, and currently the means of transmission is uncertain. In the current study, mechanical transmission of lumpy skin disease virus (LSDV) by Stomoxys species from infected to naive animals was demonstrated under laboratory conditions. Flies partially fed on LSDV-infected cattle were placed onto recipient animals within a 1 h time period to complete their feeding process. In addition to this, virus was isolated from all three Stomoxys species immediately and 6 h post feeding on LSDV infected animal, while virus DNA was detectable up to 48 h post-feeding by PCR.

Abstract

Samples collected for PCR from recipient animals tested positive in 5 out of 6 cases, while the virus was isolated from 4 of 6 animals. The clinical signs exhibited by recipient animals were mostly moderate in nature with only one severe case. To our knowledge, this is the first time that transmission of LSDV by three Stomoxys species has been demonstrated, and their role as mechanical vectors of LSDV is indicated.

Seasonal succession of tabanid species in equine infectious anaemia endemic areas of Italy

Equine infectious anaemia (EIA) is a disease with an almost worldwide distribution, with several outbreaks having been reported recently in European countries. In Italy, two regions, Lazio and Abruzzo, are considered as endemic areas for this disease. In nature, the EIA virus is mechanically transmitted by biting flies such as tabanids (Diptera: Tabanidae), although few studies have investigated the epidemiological implications. In the present study, several sites characterized by different levels of EIA prevalence were sampled. In sites with high tabanid populations, a seasonal succession of tabanid species with a dual-peak corresponding to early active species (i.e. in June to July) and late active species (i.e. in August to September) was clearly observed. Moreover, a positive correlation was found between EIA prevalence and tabanid abundance and species richness, suggesting that tabanid diversity might extend the duration of the seasonal transmission period of EIA. Further observations are required to better assess how vector diversity influence EIA transmission.

A Review of Design and Fabrication of the Bionic Flapping Wing Micro Air Vehicles

Bionic flapping-wing micro air vehicles (FWMAVs) are promising for a variety of applications because of their flexibility and high mobility. This study reviews the state-of-the-art FWMAVs of various research institutes driven by electrical motor, mechanical transmission structure and "artificial muscle" material and then elaborates on the aerodynamic mechanism of micro-winged birds and insects. Owing to their low mass budget, FWMAVs require actuators with high power density from micrometer to centimeter scales. The selection and design of the mechanical transmission should be considered in parallel with the design of the power electronic interface required to drive it. Finally, power electronic topologies suitable for driving "artificial muscle" materials used in FWMAVs are stated.

A unique phenomenon of oral-anal contact between ticks observed in two tick species Ixodes ricinus and Dermacentor reticulatus

For the first time in the world literature, the presented study describes oral-anal contact between two sympatric Ixodes ricinus and Dermacentor reticulatus ticks, which are the vectors of many pathogens in Europe. Among the specimens collected in nature, an I. ricinus male was found with the hypostome and chelicerae inserted in the anal aperture of a D. reticulatus female. Given the biological and physiological traits of both species and microorganisms colonising these arthropods, it seems that the interspecific oral-anal contacts between ticks may be an unknown alternative route of transmission of pathogenic and symbiotic microorganisms present in ticks' alimentary tract, faeces, body surface, and in the haemolymph and organs, taking place when the male's mouthparts are inserted into the female's body. The authors suggest that interspecific contacts between ticks in natural conditions can contribute to the spread of some icroorganisms among different tick species and their hosts..

High relative abundance of the stable fly Stomoxys calcitrans is associated with lumpy skin disease outbreaks in Israeli dairy farms

The vector of lumpy skin disease (LSD), a viral disease affecting Bovidae, is currently unknown. To evaluate the possible vector of LSD virus (LSDV) under field conditions, a yearlong trapping of dipterans was conducted in dairy farms that had been affected by LSD, 1-2 years previously. This was done in order to calculate monthly relative abundances of each dipteran in each farm throughout the year. The relative abundances of Stomoxys calcitrans (Diptera: Muscidae) in the months parallel to the outbreaks (December and April) were significantly higher than those of other dipterans. A stable fly population model based on weather parameters for the affected area was used to validate these findings. Its results were significantly correlated with S. calcitrans abundance. This model, based on weather parameters during the epidemic years showed that S. calcitrans populations peaked in the months of LSD onset in the studied farms. These observations and model predictions revealed a lower abundance of stable flies during October and November, when LSD affected adjacent grazing beef herds. These findings therefore suggest that S. calcitrans is a potential vector of LSD in dairy farms and that another vector is probably involved in LSDV transmission in grazing herds. These findings should be followed up with vector competence studies.

Exploring the possibility of arthropod transmission of HCV

Hepatitis C virus (HCV) is a major cause of chronic hepatitis, cirrhosis, and liver cancer occurring in up to 3% of the world's population. Parenteral exposure to HCV is the major mode of transmission of infection. Once established, infection will persist in up to 85% of individuals with only a minority of patients clearing viremia. Egypt has possibly the highest HCV prevalence in the world where 10-20% of the general population are infected with HCV. Endemic HCV appears to be concentrated in the tropics and sub-tropics where there are higher biting rates from insects. The question as to whether a bridge vector transmission is possible, via arthropods, both between humans and/or from an animal reservoir to humans is explored. Mechanical transmission, as opposed to biological transmission, is considered. Mechanical transmission can be an efficient way of transmitting an infection, as effective as biological transmission. Probability of transmission can increase as to the immediate circumstances and conditions at the time. Several factors may enhance mechanical transmission, including high levels of microbes in the vector, frequent biting, the close proximity, and contact between vectors and recipients as well as high density of insects. HCV has been isolated from bodies or heads of mosquitoes collected from the houses of HCV-infected individuals. The possibility of enzootic cycles of HCV tangential transmission via bridging vectors, such as, arthropods needs to be further investigated and possible animal reservoirs, including domestic rural epizootic cycles for HCV infection, requires further research with particular initial emphasis on equine infections. J. Med. Virol. 89:187-194, 2017. © 2016 Wiley Periodicals, Inc.

Evaluation of disinfectants to prevent mechanical transmission of viruses and a viroid in greenhouse tomato production

BACKGROUND

In recent years, a number of serious disease outbreaks caused by viruses and viroids on greenhouse tomatoes in North America have resulted in significant economic losses to growers. The objectives of this study were to evaluate the effectiveness of commercial disinfectants against mechanical transmission of these pathogens, and to select disinfectants with broad spectrum reactivity to control general virus and viroid diseases in greenhouse tomato production.

METHODS

A total of 16 disinfectants were evaluated against Pepino mosaic virus (PepMV), Potato spindle tuber viroid (PSTVd), Tomato mosaic virus (ToMV), and Tobacco mosaic virus (TMV). The efficacy of each disinfectant to deactivate the pathogen's infectivity was evaluated in replicate experiments from at least three independent experiments. Any infectivity that remained in the treated solutions was assessed through bioassays on susceptible tomato plants through mechanical inoculation using inocula that had been exposed with the individual disinfectant for three short time periods (0-10 sec, 30 sec and 60 sec). A positive infection on the inoculated plant was determined through symptom observation and confirmed with enzyme-linked immunosorbent assay (PepMV, ToMV, and TMV) and real-time reverse transcription-PCR (PSTVd). Experimental data were analyzed using Logistic regression and the Bayesian methodology.

RESULTS

Statistical analyses using logistic regression and the Bayesian methodology indicated that two disinfectants (2% Virkon S and 10% Clorox regular bleach) were the most effective to prevent transmission of PepMV, PSTVd, ToMV, and TMV from mechanical inoculation. Lysol all-purpose cleaner (50%) and nonfat dry milk (20%) were also effective against ToMV and TMV, but with only partial effects for PepMV and PSTVd.

CONCLUSION

With the broad spectrum efficacy against three common viruses and a viroid, several disinfectants, including 2% Virkon S, 10% Clorox regular bleach and 20% nonfat dry milk, are recommend to greenhouse facilities for consideration to prevent general virus and viroid infection on tomato plants.

The majority of cockroaches from the Samutprakarn province of Thailand are carriers of parasitic organisms

We undertook a study of the mechanical transmission of parasitic organisms in cockroaches in the Samutprakarn province of Thailand. In this study, 920 cockroaches were obtained from 18 open-air shopping markets in 5 districts and 1 subdistrict of this province. All cockroaches were captured during their feeding time in their natural habitat. Direct wet smear and modified acid-fast bacilli staining were used to identify the parasites from the external surface or cuticle of the cockroaches. The results show that 498 (54.1 %) of the cockroaches harbored parasitic organisms. Of these, 56.1 % were protozoa and the remaining 43.9 % were helminthes (pathogenic helminthes- 1.4 %, non-pathogenic helminthes- 42.5 %). Of the pathogenic helminthes, the species included Strongyloides stercoralis (6 instances of the free-living adult male, 0.8 %), Ascaris lumbricoides (2 decorticated eggs, 0.3 %), Trichuris trichiura (2, 0.3 %), and Taenia spp. (1 egg, 0.1 %). The protozoa types that were identified included Cyclospora spp. (10 oocysts, 1.3 %), Endolimax nana (10 cysts, 1.3 %), B. hominis (9 instances of the vacuolated form, 1.2 %), Isospora belli (75 oocysts, 9.6 %), Entamoeba histolytica/E. dispar (36 cysts, 4.6 %), Cryptosporidium spp. (220 oocysts, 28.1 %), Chilomastix mesnilli (2 cysts, 0.3 %), Entamoeba coli (31 cysts, 4.0 %), Balantidium coli (45 trophozoites, 5.8 %), and Iodamoeba butschlii (1 cyst, 0.1 %). These results show that cockroaches isolated from these markets are carriers of several parasitic organisms that cause commonly found symptoms of illness such as diarrhea or bowel disorder.

Insect contribution to horizontal transmission of Reticuloendotheliosis virus

The involvement of insects in Reticuloendotheliosis virus (REV) transmission was examined by testing insects trapped at commercial farms and by controlled feeding experiments using mosquitoes, Culex pipiens L. and house flies, Musca domestica L. We established sensitive methods of REV detection, including reverse transcription-polymerase chain reaction (PCR) for REV-LTR and REV-gag genes, REV antigenemia measurements by enzyme-linked immunosorbent assay, and virus isolation in tissue cultures. A variety of blood-sucking species of insects were trapped at farms with infected poultry and tested, but none were positive. To rule out the possibility of PCR inhibition by insect RNA, spiking experiments were conducted and no interference was observed. Because Cx. pipiens mosquitoes were trapped frequently at farms, we performed feeding experiments with mosquito females fed on a REV-containing tissue culture medium and chicken blood mixture. Virus was detected in the mosquitoes up to 5 h postfeeding, compared with 96 h in the feeding mixture, indicating that Cx. pipiens can only harbor REV for a short period. House flies were suspected to be involved in the virus transmission because they frequently were trapped on positive farms. In contrast to mosquitoes, REV was harbored within the house fly digestive tract for up to 72 h and could infect chickens, as demonstrated by seroconversion and by detection of viral gag-sequence in the cloaca. The current study is supportive for the role of house flies as a mechanical vector of REV among poultry.