Transovarial Transmission Of Virus Research Articles

THE DETECTION OF DENGUE VIRUS TRANSOVARIAL TRANSMISSION IN Aedesaegypti MOSQUITOES IN PONTIANAK CITY ENDEMIC AREA

The background of this study is that the Dengue Virus is highly pathogenic in humans and spreads rapidly through the bites of Aedes aegypti and Aedes albopictus. more than half a billion of the 100 countries in the world are at serious risk of dengue virus infection. The purpose of this study was to prove the existence of transovarial dengue virus transmission in Ae.aegypti mosquitoes with a transovarial transmission index (TTI) in the Endemis area in Pontianak, West Kalimantan. The method used in this study was observational descriptive with a cross-sectional study, namely to prove the existence of transovarial virdi transport in the same period. The conclusion was proved by the transovarial transmission of dengue virus in Ae.aegypti mosquitoes in Pontianak City, TTI by 30% in Sungai Jawi village, and 40% in Batulayang Village. Virus serotype was found, namely DENV-3.

Vector development and vitellogenin determine the transovarial transmission of begomoviruses

The majority of plant viruses are transmitted by insect vectors between hosts, and transovarial transmission of viruses from vector parents to offspring has great significance to their epidemiology. Begomoviruses are transmitted by the whitefly Bemisia tabaci in a circulative manner and are maintained through a plant-insect-plant cycle. Other routes of begomovirus transmission are not clearly known. Here, we report that transovarial transmission from female whiteflies to offspring often happens for one begomovirus, Tomato yellow leaf curl virus (TYLCV), and may have contributed significantly to its global spread. We found that TYLCV entry of the reproductive organ of its vector mainly depended on the developmental stage of the whitefly ovary, and the transovarial transmission of TYLCV to offspring increased with whitefly adult age. The specific interaction between virus coat protein (CP) and whitefly vitellogenin (Vg) was vital for virus entry into whitefly ovary. When knocking down the expression of Vg, the entry of TYLCV into ovary was inhibited and the transovarial transmission efficiency decreased. In contrast, another begomovirus, Papaya leaf curl China virus (PaLCuCNV), CP did not interact with whitefly Vg, and PaLCuCNV could not be transovarially transmitted by whiteflies. We further showed that TYLCV could be maintained for at least two generations in the absence of virus-infected plants, and the adult progenies were able to infect healthy plants in both the laboratory and field. This study reports the transovarial transmission mechanism of begomoviruses, and it may help to explain the evolution and global spread of some begomoviruses.

Experimental Vector Incompetence of a Soft Tick, Ornithodoros sonrai (Acari: Argasidae), for Crimean-Congo Hemorrhagic Fever Virus

Adults and nymphs of a soft tick, Ornithodoros sonrai Sautet & Witkowski, were allowed to feed on suckling mice that had been experimentally infected with Crimean-Congo hemorrhagic fever (CCHF) virus (IbAr 10200 strain). The mean viral titer of mouse blood at the time of tick feeding was 10(3.2) plaque-forming units (PFU) per ml. Samples of ticks were assayed on 12 occasions between days 0 and 31 after the viremic blood meal. Mean CCHF viral titers were 10(2.1) PFU per tick immediately after the viremic meal but declined to 10(1.2) PFU per tick after 2 d, and no virus was detected beyond 8 d. The percentage of ticks with detectable virus was 92% (22/24) immediately after the viremic meal, but then declined to 20% (2/10) after 4 d and to 0% (0/44) after 11 or more days. Ticks were allowed to feed on sets of three naive suckling mice on days 0, 2, 5, 8, 11, 14, 21, and 28 after the viremic blood meal, but CCHF viral transmission did not occur. Similarly, no transovarial transmission of virus from CCHF virus-exposed O. sonrai to their progeny was observed. These results strongly indicate that O. sonrai is not a vector of CCHF virus.

RNA genome stability of Toscana virus during serial transovarial transmission in the sandfly Phlebotomus perniciosus

We have carried out a T1 ribonuclease fingerprinting analysis of the RNA genomes of Toscana virus isolates from successive generations of an experimentally virus-infected laboratory colony of Phlebotomus perniciosus sandflies. This analysis detected no virus RNA genome changes during transovarial transmission of the virus over 12 sandfly generations (a period of almost 2 years). These results demonstrate that although RNA viruses can exhibit high rates of mutational change under a variety of conditions, Toscana virus RNA genomes can be maintained in a stable manner during repeated transovarial virus transmission in the natural insect host. The implications of these results for insect RNA virus evolution are discussed.

Panveld oviposition sites of floodwater Aedes mosquitoes and attempts to detect transovarial transmission of Rift Valley fever virus in South Africa.

Floodwater aedine mosquito eggs were recovered from soil samples taken from grassland depressions, called pans, in the Orange Free State Province of South Africa. A sedge, Mariscus congestus (Vahl) C.B.Cl., was a useful indicator of Aedes (Ochlerotatus) juppi McIntosh oviposition areas. No transovarial transmission of virus was demonstrated by Ae.juppi females reared from the eggs and allowed to feed shortly after eclosion on hamsters. No virus was recovered from 557 pools of 5425 adult Ae.juppi that were collected as eggs and reared to the adult stage in the laboratory. Rift Valley fever virus replicated to high titres in experimentally infected Ae.juppi females, but horizontal transmission experiments proved inconclusive.

Transovarial transmission of yellow fever virus in Stegomyia mosquitoes.

Transovarial transmission of two strains of yellow fever virus was demonstrated in three colonized geographical strains of Aedes aegypti following infection by intrathoracic inoculation. Infected progeny were detected in F1 offspring from only the first three ovarian cycles (OVC). The overall minimum filial infection rate for the first three OVC was 1:596; rates were loser in the second and third OVC. Virus survived in eggs for longer than 4 months and was recovered from progeny of three immersions of first OVC eggs. Infected progeny averaged a longer time to pupation than noninfected siblings. Transovarial transmission of virus was also demonstrated in first OVC progeny of Aedes mascarensis.

The ecology of California group viruses.

Fifteen viruses have been described as members of the California group of arboviruses; of these, 10 are currently considered to be antigenically distinct viruses, 2 are still under consideration, 2 are now considered synonyms of previously described viruses, and 1 (Bocas virus) is now recognized as a variant of mouse hepatitis virus. Synopses of the natural history of 12 viruses of the California group are presented herein. Viruses considered include California encephalitis (CE). Trivittatus (TVT), Tahyna (TAH), Snowshoe Hare (SSH), Melao (MEL), San Angelo (SA), La Crosse (LAC), Keystone (KEY), Jamestown Canyon (JC), Inkoo (INK), South River and Serra do Navio viruses. Brief mention is also made of Lumbo virus, a synonym of TAH virus, and Jerry Slough, a synonym of JC virus. The general aspects of virus transmission appear to be similar for most viruses of the group. The majority appear to have 2 distinct cycles: a dormant maintenance cycle and an active amplification cycle. Transovarial transmission of virus by certain vector species appears to be one significant means of dormant maintenance. Hibernating infected vectors or vertebrate hosts may perhaps also serve to maintain virus. In the amplification cycle, mosquitoes, primarily of the genus Aedes , apparently serve as principal vectors, and mammals serve as vertebrate hosts. The primary vectors and vertebrate hosts utilized by each virus vary considerably. Man is thought to become involved in some cycles only as an accidental, dead-end host. Clinical disease results from infection by some viruses of the group, and this has been documented for LAC, CE and TAH viruses. Other viruses of the group are suspected of causing human illness as well, but documentation is incomplete.

Transmission of a mosquito iridescent virus in Aedes taeniorhynchus: II. Experiments related to transmission in nature

Experiments relating to the transmission of MIV in nature are described. Intact cadavers of diseased fourth-instar larvae were found to be potent sources of infection in laboratory experiments. A field experiment showed that infection could be acquired per os by larvae exposed under natural conditions, and that when healthy fourth-instar larvae were given access to intact diseased cadavers for a short time before pupation, they became infected and produced adults that laid infected eggs. Further laboratory tests showed that the virus becomes uninfective after a few days when liberated into artesian and 10% seawater, and does nto remain active when liberated onto the surface of soil such as might be found in natural breeding grounds of Aedes taeniorhynchus. A tentative account of the natural history of the disease is given in which it is proposed that the pathogen survives through a simple cyle. Transovarial transmission of virus gives rise to diseased larvae, which die in the fourth instar. The cadavers so formed provide the source of new infection, which is acquired per os by healthy larvae just before pupation. Infected adults from these larvae complete the cycle by depositing infected eggs.

Multiplication of the Rice Stripe Virus in its Insect Vector, Laodelphax striatellus Fallen

The present paper describes the results of experiments carried out with the aim of obtaining evidences other than the transovarial virus transmission, of multiplication of the rice stripe virus in its insect vector, the smaller brown planthopper Laodelphax striatellus Fallen, and information about the possible site of virus multiplication and pathological effects of the virus on the insect vector.Serial transfers of the rice stripe virus from insect to insect were made using micro-injection method described by Maramorosch (1952). The virus was successfully carried in 4 serial passages in the smaller brown planthopper. The final dilution of the inoclum used to inject the last group of the series is calculated to be at least 1.25×10-6 of the original inoculum, while the virus derived from viruliferous insects was shown to have a dilution end-point between 10-2 and 10-3. Groups of planthoppers which had been injected with the juice from viruliferous insects, were macerated 2, 5, 10 and 15 days after the injection, and the preparations were tested for infectivity by inoculating to virus free insects. The inocula prepared from the planthoppers 2 and 5 days after injection were found noninfective, in coincidence with the incubation period in the vector. A 1:10 dilution of the macerate from planthoppers 10 days after injection and a 1:50 dilution of those from planthoppers 15 days after injection proved infective. This suggests that the virus may have multiplied in its vector at least fivehold during the period from 5th to 15th day after injection.Blood and various organs from viruliferous planthoppers were tested for the presence of virus by the injection method. Virus was recovered from eggs, male reproductive organs, and blood and fat body, while no virus was recovered from alimentary canal.Male planthoppers following 2 days of acquisition feeding on diseased rice plants were dissected to remove legs, wings, alimentary canal, Malpighian tubules and reproductive organ, and the remaining part was separated into head, thorax, and abdomen. These body parts were incubated for 13 days at 25-27°C in hanging drops of a medium consisting of Takami's salt solution, D-glucose and extract from their respective part. The virus was not recovered from fresh material of these parts, but was recovered from the abdominal part incubated in vitro for 13 days. Female and male reproductive organs excised from planthoppers which had fed for 3 days on diseased plants, were incubated for 12 days in vitro. From both organs virus was recovered after having been incubated for 12 days, but not before incubation.Cytological examinations of blood corpsucles, reproductive cells, salivary glands, alimentary canal, dermis, and fat body of viruliferous planthoppers showed no consistent, conspicuous changes in these tissues. Histochemical tests for hyaluronic acid, RNA, DNA, lipid, and phospholipid, and phosphatase activity showed no distinct difference between viruliferous and virus-free planthoppers. Relative amount of glycogen and of polysaccharides in the fat body and of mycetome, as determined by Bauer-Feulgen stain and by Lillie method, appeared to be somewhat less in viruliferous planthoppers than in virusfree ones.