Vertical transmission of tomato viruses.

Simple SummaryThe transmission of vector-borne viruses requires arthropod vectors that are actively seeking for new blood-meal hosts. In regions where vectors do not blood-feed for prolonged periods, the persistence of a virus depends on alternative mechanisms of transmission, such as the transmission of a virus from an infected arthropod mother to her offspring, via so-called vertical transmission. Far less is known about this type of transmission than about transmission between vertebrate hosts, and it is often viewed as rarely occurring. Sindbis virus is one of many mosquito-borne viruses that originates in the tropics and has become introduced and established in temperate regions. In its northern range, the virus must persist through several months of winter when its mosquito vectors are inactive. In this study, we investigated the vertical transmission of Sindbis virus, both experimentally and in the field, and found evidence from the field that it does occur but with conflicting results in the experiments. This new knowledge highlights factors which are necessary for tropical viruses to establish in temperate regions.Vertical transmission (VT) is a phenomenon of vector-borne diseases where a pathogen is transferred from an infected arthropod mother to her offspring. For mosquito-borne flavi- and alphaviruses, VT is commonly viewed as rare; however, both field and experimental studies report on vertical transmission efficiency to a notably varying degree. It is likely that this reflects the different experimental methods used to test vertical transmission efficiency as well as differences between virus–vector combinations. There are very few investigations of the VT of an alphavirus in a Culex vector. Sindbis virus (SINV) is an arthritogenic alphavirus that utilizes Culex species as main vectors both in the summer transmission season and for its persistence over the winter period in northern latitudes. In this study, we investigated the vertical transmission of the SINV in Culex vectors, both in the field and in experimental settings. The detection of SINV RNA in field-collected egg rafts and emerging adults shows that vertical transmission takes place in the field. Experimentally infected females gave rise to adult offspring containing SINV RNA at emergence; however, three to four weeks after emergence none of the offspring contained SINV RNA. This study shows that vertical transmission may be connected to SINV’s ability to persist throughout northern winters and also highlights many aspects of viral replication that need further study.

Ascogregarina culicis and Ascogregarina taiwanensis are common gregarine parasites of Aedes aegypti and Aedes albopictus mosquitoes, respectively. These mosquito species are also known to transmit dengue and Chikungunya viruses. The sporozoites of these parasites invade the midgut epithelial cells and develop intracellularly and extracellularly in the gut to complete their life cycles. The midgut is also the primary site for virus replication in the vector mosquitoes. Therefore, studies were carried out with a view to determine the possible role of these gregarines in the vertical transmission of dengue and Chikungunya viruses from larval to adult stage. Experiments were performed by exposing first instar mosquito larvae to suspensions containing parasite oocysts and viruses. Since Ascogregarina sporozoites invade the midgut of first instar larvae, the vertical transmission was determined by feeding the uninfected first instar larvae on the freshly prepared homogenates from mosquitoes, which were dually infected with viruses and the parasite oocysts. Similarly, the role of protozoan parasites in the vertical transmission of viruses was determined by exposing fresh first instar larvae to the dried pellets of homogenates prepared from the mosquitoes dually infected with viruses and the parasite oocysts. Direct vertical transmission and the vertical transmission of CHIK virus through the oocyst of the parasites were observed in the case of Ae. aegypti mosquitoes. It is suggested that As. culicis may have an important role in the maintenance of CHIK virus during the inter-epidemic period.

Dengue is of great concern in various parts of the world, especially in tropical and subtropical countries where the mosquito vectors Aedes aegypti and Aedes albopictus are present. The transmission of this virus to humans, by what is known as horizontal transmission, occurs through the bite of infected females of one or other of the two mosquito species. Furthermore, an infected female or male parent, by what is known as vertical transmission, can transfer this arbovirus to some part of their offspring. Considering that vertical transmission may represent an important strategy for maintaining the circulation of arboviruses in nature, the verification of this phenomenon worldwide is extremely important and necessary to better understand its dynamic. In the present study, we conducted a literature review of the presence of natural vertical transmission of dengue virus in Ae. aegypti and Ae. albopictus worldwide. Searches were conducted in MEDLINE, sciELO and Lilacs and all the studies published in Portuguese, English and Spanish were read, evaluated and organized by mosquito species, serotype and the location at which the samples were collected. Forty-two studies were included in accordance with the exclusion criteria and methodology. The presence of natural vertical transmission in Ae. aegypti and Ae. albopictus was most clearly evidenced by dengue virus in endemic countries, especially in those in South America and Asia. Despite several African countries being considered endemic for dengue, there is a lack of publications on this subject on that continent, which highlights the importance of conducting studies there. Furthermore, the finding of natural vertical transmission in Ae. albopictus in countries where this species is not yet incriminated as a vector is of great concern as it demonstrates the circulation of this virus in populations of Ae. albopictus and alerts to the possibility of some other mosquito species playing a role in the transmission dynamics of this arbovirus. Parallel to this, the small number of studies of natural vertical transmission of chikungunya and Zika virus in the world may be explained by the recent entry of these arboviruses into most of the countries concerned.

Parasites can be transmitted vertically and/or horizontally, but the costs or benefits for the host of infection have only been tested after horizontal transmission. Here, we report for the first time, to our knowledge, the survival, reproduction and infection of Aedes aegypti during vertical and horizontal transmission of dengue virus 2 (DENV-2). Females infected horizontally produced more eggs, with a sex ratio skewed towards males, compared with uninfected controls. However, there was no significant difference in the number of emerging adults or in survival of mothers. In contrast, dengue-infected female offspring (vertical transmission) had a shorter lifespan but there were no significant differences in the number of eggs or sex ratio, compared with controls. Finally, the corroboration of infection revealed that virus infected about 11.5% and 8.8% of pools of mothers and of daughters, respectively. These results suggest that the mode of infection and the contact with the virus has no reproductive costs to female mosquitoes, which may explain why both types of transmission are evolutionarily maintained. In addition, we suggest that more attention should be paid to the male contribution to virus dissemination within and among populations and as reservoirs of the infection for human diseases.

Mother-to-child transmission of HIV is known as vertical transmission of human immunodeficiency virus (HIV). Although the risk of transmission can be significantly reduced with preventive measures, there is still a possibility of mother-to-child transmission of HIV without appropriate interventions. The virus can be present in bodily fluids such as blood and breast milk, and coming into direct contact with these fluids can lead to infection. Children born to HIV-infected mothers must receive appropriate medical and dental care from an early age to manage potential complications associated with vertical transmission of the virus. Oropharyngeal candidiasis in HIV-infected children has an increased risk of developing fungal infections, such as oropharyngeal candidiasis. This infection can affect the oral cavity, throat, and esophagus, causing symptoms such as white or red lesions, difficulty swallowing, and pain in the mouth. The compromised immune system of HIV-infected children puts them at increased risk of bacterial infections in the oral cavity. These infections can include gingivitis, periodontitis, and other bacterial pathogens that can affect oral tissues. Oral ulcerative lesions in the oral cavity in children with HIV can develop ulcerative lesions in the oral cavity, which can cause pain and discomfort. These lesions can be caused by opportunistic infections or manifestations of the virus itself. HIV can also affect tooth development in children, causing delays or abnormalities in their growth and development. The gums can also be affected, leading to gingivitis or other gum disease..

The prevalence of GB virus C (GBV-C)/HGV is high in individuals with parenteral risk factors. The frequency of GBV-C/HGV in blood donors is significantly lower, however it is still far above other parenterally transmitted viruses like HBV and HCV. Therefore, transmission routes apart from parenteral transmission must be considered. The purpose of the study was to evaluate the prevalence of GBV-C/HGV in blood donors and relatives of GBV-C/HGV-positive and -negative blood donors. Prevalence was also analyzed in aplastic anemia patients. Samples were tested by RT-PCR and partially by ELISA. Positive isolates were sequenced and phylogenetically analyzed. A total of 5733 blood donors were PCR tested and 90 were positive (1.6%). Of these, 98 relatives could be tested. Viremia was found in 14.3 percent and anti-E2 in 29.5 percent, whereas only 1.1 percent of the relatives of PCR-negative donors were viremic and 8.5 percent were anti-E2 positive. Probable virus transmission could be shown in two couples and in six mother-child pairs by sequencing of isolates indicating horizontal and vertical virus transmission, respectively. Recipients of GBV-C/HGV RNA-positive blood products were shown to be infected at a rate of 58 percent (18/31). Aplastic anemia patients were positive at a rate of 32 percent (17/53). The high percentage of 14.3 percent of GBV-C/HGV PCR-positive relatives of GBV-C/HGV-positive blood donors suggests intrafamilial transmission. Sequence analyses revealed vertical and horizontal transmission. Although parenteral transmission is highly efficient for GBV-C/HGV (58% of recipients of GBV-C/HGV RNA-positive blood products and 32% of aplastic anemia patients), it appears that sexual and vertical transmission are the most common transmission routes.

Knowledge of vertical transmission of human immunodeficiency virus in two inner-city obstetric populations

A history and certain characteristics of some tumor virus infections are presented. Vertical and/or horizontal transmission of murine leukemia viruses, particularly Friend virus (FV), Rauscher virus (RLV), and 334C virus, is discussed. Transmission of FV virus occurs through successive generations following infection of adult mice, and transmission of 334C virus occurs through successive generations following infection of newborn mice. Foster‐nursing experiments show that most effective transmission of FV, RLV, and 334C viruses occurs through the mother's milk. Transplacental transmission of virus, as determined by development of virus‐induced disease, has not been seen in reciprocal foster‐nursing studies or in tests of embryo extracts from FV‐ and RLV‐infected mothers, but test of embryo extract suggests that some transplacental transmission of 334C virus may occur. Unlike the mammary tumor virus, FV and RLV are not transmitted through the paternal line. Relatively high infectivity of semen and low incidence of leukemia in litters sired by infected males suggest a high potential for transmission of 334C virus by the male parent. FV, RLV, and 334C viruses may be transmitted by injection of urine, inducing low incidences of disease with long latency periods. Preparations from oral washings and feces from mice infected with FV and RLV have not induced disease in assay mice, but similar preparations from mice infected with 334C virus have induced low incidences of disease. Waterborne transmission of FV has been barely successful, but airborne and foodborne transmission have been unsuccessful. While the possibility of horizontal transmission of virus exists, horizontal transmission of FV and RLV in the natural environment, even under optimal conditions, is minimal. Friend virus‐infected mothers transmit maternal antibodies and virus to their offspring, which may account for the low natural incidence of the disease and the long latent period frequently observed.

Plastic pollution and infectious diseases

There is evidence showing that vertical transmission of dengue virus exists in Aedes mosquitoes. In this paper, we propose a deterministic dengue model with vertical transmission in mosquitoes by including aquatic mosquitoes (eggs, larvae and pupae), adult mosquitoes (susceptible, exposed and infectious) and human hosts (susceptible, exposed, infectious and recovered). We first analyze the existence and stability of disease-free equilibria, calculate the basic reproduction number and discuss the existence of the disease-endemic equilibrium. Then, we study the impact of vertical transmission of the virus in mosquitoes on the spread dynamics of dengue. We also use the model to simulate the reported infected human data from the 2014 dengue outbreak in Guangdong Province, China, carry out sensitivity analysis of the basic reproduction number in terms of the model parameters, and seek for effective control measures for the transmission of dengue virus.

The updated South African National Guideline for the Prevention of Mother to Child Transmission of Communicable Infections (2019).

Aedes aegypti and Aedes albopictus are the main mosquito species responsible for dengue virus (DENV) transmission to humans in the tropical and subtropical regions of the world. The role of vertical transmission in the epidemiology of dengue and the maintenance of this arbovirus in nature during interepidemic periods remain poorly understood, and DENV vertical transmission could sustain the existence of virus reservoirs within Aedes populations. Between April 2011 and October 2012, we monitored vertical transmission of DENV in Ae. aegypti and Ae. albopictus in 9 cities of 4 Mexican states. Aedes eggs were collected in ovitraps, then adults were reared under laboratory conditions and their heads were used to infect C6/36 cells. The presence of flavivirus was detected by immunofluorescence assays (IFA), and DENV infection was confirmed by RT-PCR. About 96% of reared adults were Ae. aegypti and 4.0% were Ae. albopictus. No infection was detected in Ae. albopictus, whereas 54 of 713 (7.8%) of Ae. aegypti pools tested positive. A minimum infection rate (MIR) of 2.52 per 1000mosquitoes was estimated for Ae. aegypti. DENV-1, DENV-2 & DENV-3 serotypes were detected even during interepidemic periods. This study reports the evidence of vertical transmission of dengue virus with viral isolation and molecular confirmation in Ae. aegypti eggs collected in four endemic regions of Central and Southern Mexico. Vertical transmission may play a role as a reservoir mechanism during mosquito dormancy in interepidemic periods but with minor participation in transmission during epidemic periods.

Vertical transmission of dengue viruses by mosquitoes was discovered at the end of the late 1970s and has been suggested to be a means by which these viruses persist. However, it is unclear how widespread it is in nature, and its importance in the epidemiology of this disease is still debated. Here, we review the literature on vertical transmission and discuss its role in dengue's epidemiology and control. We conclude that given the number of studies that failed to find evidence of vertical transmission, as well as mathematical models and its mechanistic basis, it is unlikely that vertical transmission is important for the epidemiological persistence of dengue viruses. A combination of asymptomatic infection in humans and movement of people are likely to be more important determinants of dengue's persistence. We argue, however, that there may be some need for further research into the prevalence of dengue viruses in desiccated, as well as diapausing, eggs and the role of horizontal transmission through larval cannibalism.

The prototypic hypovirus CHV1-EP713 attenuates virulence (hypovirulence) and alters several physiological processes of the chestnut blight fungus Cryphonectria parasitica. The papain-like protease, p29, and the highly basic protein, p40, derived, respectively, from the N-terminal and C-terminal portions of the CHV1-EP713-encoded open reading frame (ORF) A polyprotein, p69, both contribute to reduced pigmentation and sporulation. The p29 coding region was shown to suppress pigmentation and asexual sporulation in the absence of virus infection in transformed C. parasitica, whereas transformants containing the p40-coding domain exhibited a wild-type, untransformed phenotype. Deletion of either p29 or p40 from the viral genome also results in reduced accumulation of viral RNA. We now show that p29, but not p40, functions in trans to enhance genomic RNA accumulation and vertical transmission of p29 deletion mutant viruses. The frequency of virus transmission through conidia was found to decrease with reduced accumulation of viral genomic double-stranded RNA (dsRNA): from almost 100% for wild-type virus to approximately 50% for Deltap29, and 10 to 20% for Deltap69. When expressed from a chromosomally integrated cDNA copy, p29 elevated viral dsRNA accumulation and transmission for Deltap29 mutant virus to the level shown by wild-type virus. Increased viral RNA accumulation levels were also observed for a Deltap69 mutant lacking almost the entire ORF A sequence. Such enhancements were not detected in transgenic fungal colonies expressing p40. Mutation of p29 residues Cys(70) or Cys(72), strictly conserved in hypovirus p29 and potyvirus HC-Pro, resulted in the loss of both p29-mediated suppressive activity in virus-free transgenic C. parasitica and in trans enhancement of RNA accumulation and transmission, suggesting a linkage between these functional activities. These results suggest that p29 is an enhancer of viral dsRNA accumulation and vertical virus transmission through asexual spores.

To determine if hepatitis C virus (HCV) infection affects vertical transmission of human immunodeficiency virus (HIV), 487 HIV-infected pregnant women in the prospective, multicenter, Women and Infants Transmission Study had HCV antibody (anti-HCV by second-generation ELISA) and HCV RNA (by quantitative polymerase chain reaction) measured in peripartum maternal plasma; 161 (33%) were anti-HCV-positive. HIV vertical transmission occurred from 42 HCV-infected mothers (26.1%) versus 53 HCV-uninfected mothers (16.3%; odds radio [OR], 1.82; P = .01). In a logistic regression model that included maternal drug use, a potential confounder, HCV infection was marginally associated with perinatal HIV transmission (OR, 1.64; P = .05), whereas drug use was not. Women who transmitted HIV had higher levels of HCV RNA (median, 721,254 copies/mL) than those who did not (337,561 copies/mL; P = .01). Maternal HCV infection is associated with increased HIV vertical transmission. Further studies are needed to ascertain if HCV directly affects perinatal HIV transmission or is a marker for another factor, such as maternal drug use.