Showing papers on "Dengue virus published in 1971"

Pandemic Dengue in Caribbean Countries and the Southern United States — Past, Present and Potential Problems

Abstract: THE outbreaks of dengue in the Caribbean area in 1963–64 and 1968–691 have served as reminders of the continuing presence of dengue in the Western Hemisphere, and the threat of recurrence of epidem...

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City: 5. Observations in relation to dengue haemorrhagic fever

Abstract: Dengue haemorrhagic fever in Singapore was a disease of the urban human population, with concentrations of cases occurring in areas of high population density. Mosquito surveys revealed that these areas also had high population densities of Ae. aegypti and Ae. albopictus.The disease occurred throughout the year but the incidence of cases appeared to follow a seasonal pattern. Observations from 1966 to 1968 showed that the number of cases increased in April, reached a peak in November, and, thereafter, decreased until the next increase in April of the following year. The epidemic curve generally agreed with the fluctuations of both Ae. aegypti and Ae. albopictus populations, although the latter species appeared to show a better correspondence with the incidence of cases.Six dengue viruses were isolated from the two Aedes species during 1966. One dengue type 2 virus was isolated from a pool of Ae. aegypti and 1 dengue type 1 virus and 4 dengue type 2 viruses were recovered from 5 pools of Ae. albopictus. These viruses were isolated from mosquitos collected during the period of increase in the incidence of cases and in 4 different areas of the city. The dengue virus infection rates per 1 000 mosquitos estimated in the present study were 0.51 for Ae. aegypti and 0.59 for Ae. albopictus.The data obtained in the present study suggest that both Ae. aegypti and Ae. albopictus are involved in the transmission of dengue haemorrhagic fever in Singapore.

Growth of Arboviruses in Aedes albopictus and A. aegypti Cell Lines

Abstract: The susceptibility of A. albopictus and A. aegypti cell lines to infection with 22 arboviruses and 4 other viruses is listed in Table 28. A. albopictus was susceptible to infection with all the mosquito-borne arboviruses tested, but was generally resistant, with certain exceptions, to infection with members of the tick-borne groups. A. aegypti was much more restricted in its susceptibility and could support the growth of only three arboviruses. Attempts to infect both cell lines with other species of animal viruses were not successful.

Experimental infection of Aedes aegypti and Aedes albopictus with dengue viruses.

Abstract: The susceptibility of two Aedes (Stegomyia) species, Ae. aegypti and Ae. albopictus, to infection with dengue virus was assessed using both natural feeding on a viraemic gibbon and a membrane feeding technique. Both species were highly susceptible to dengue virus infection. It was found that both species were more sensitive than the LLC-MK2 cell plaque assay system used in detecting viraemia in a gibbon infected with a low tissue culture passage strain of dengue-2 virus. However, the same strain passaged in LLC-MK2 cells failed to infect either species when the mosquitoes were fed upon a suspension of this virus. Both species were infected readily when fed upon a suspension of a mouse adapted strain of dengue-2 virus.

Comparison of Three Methods Used to Isolate Dengue Virus Type 2

Abstract: During the 1969 dengue epidemic in Puerto Rico, human sera and Aedes aegypti mosquitoes were collected for virus isolation and identification. Three methods of isolation were used and compared. In the first method, we inoculated newborn mice by the intracranial route, noted any signs of illness, and serially passed specimens in mice until virus was isolated. In the second method, we inoculated tube cultures of LLC-MK2 cells, noted any cytopathic effect (CPE), and assayed fluids for virus by plaque formation in LLC-MK2 cell monolayers. The third method was different from the second only in that the original specimens were first inoculated into fluid cultures of Singh9s A. albopictus cells. No significant CPE was seen in LLC-MK2 cultures; however, distinct syncytial CPE was observed in A. albopictus cells. About the same number of virus isolates were made in each isolation system. Virus isolates from both sera and mosquitoes were identified as dengue type 2 by a plaque-reduction neutralization test in LLC-MK2 cells. The utility of the three methods, individually or in combination, is discussed and related to diagnostic and epidemic situations. Images

Comparative studies on nucleic acid synthesis and virus-induced RNA polymerase activity in mammalian cells infected with certain arboviruses.

Abstract: Variations in the metabolism of African green monkey (AGMK) and stable porcine kidney (PS) cells infected with certain arboviruses were investigated. Virus-directed RNA synthesis and RNA polymerase activity were stimulated in actinomycin-treated infected cells. The rate of3H-uridine incorporation into RNA in Western equine encephalitis (WEE) virus-infected AGMK cells reached a maximum at approximately 5 hours after infection. In contrast, the viral RNA synthesis induced by Japanese encephalitis (JE) or dengue virus did not increase appreciably during the first 15 hours, and a maximum was reached from 24 to 30 hours after infection. Cytoplasmic large- and small-particle fractions from cells infected with WEEV or JEV were found to catalyze the incorporation of 4 nucleoside triphosphates into acid-insoluble products. In WEEV-infected AGMK cells, the enzyme activity was associated almost solely with the small-particle fraction, whereas nuclear and large-particle fractions of JEV-infeeted cells still contained 15 to 30% of the total enzyme activity 24 hours after infection. Rapid inhibition of cellular DNA synthesis was observed 4 hours after infection, with each of the three kinds of arbovirus used. Heat-inactivated WEEV was unable to suppress host cell DNA synthesis appreciably, whereas infection by UV-irradiated virus did result in a clear inhibition of DNA synthesis. However, the effect was apparently less marked than that of the active WEE virus.

Mosquito-borne infections in Fiji. II. Arthropod-borne virus infections.

Abstract: Surveys of arbovirus activity in Fiji were conducted over a 10-year period from December 1959 to December 1969. No arboviruses were isolated from over 200,000 mosquitoes, 9000 ticks, or 575 serum samples. Eight thousand human and 1117 bird, bat and animal sera were tested for haemagglutination-inhibiting arbovirus antibody using a variety of group A, group B and Bunyamwera group antigens. Only a small number of low-titre reactions were found among the non-human sera, but 14% of all human sera were found to contain Group B antibody. The antibody prevalence increased with increasing age, from less than 1% for persons born since 1950, to 70% for persons born before 1900. The age differences in prevalence could be used to estimate the time and size of previous epidemics. Differences were found in antibody prevalence between the sexes, between ethnic groups and between persons from different regions. These differences could be explained in terms of climate, location and custom. Historical and serological evidence both suggest that all the antibody detected was due to past exposure to dengue virus. The very high proportion of the population with no dengue antibody makes Fiji a high-risk area for a further dengue epidemic. Dengue virus is known to be active in the Pacific and South-East Asia.