Showing papers on "Dengue fever 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.

Immunological surveys of arbovirus infections in South-East Asia, with special reference to dengue, chikungunya, and Kyasanur Forest disease.

Abstract: Serological surveys have been widely used in South-East Asia to determine the presence and activity of arboviruses. The haemagglutination-inhibition test has been most frequently employed but complement-fixation and neutralization tests have also been used in some investigations.Although virus isolations provide the most conclusive evidence, they can be carried out in a few specialized centres only, and serological surveys are very important for studying the distribution of arboviruses.The surveys have shown that group B arboviruses (principally all four types of dengue, Japanese encephalitis, and West Nile) are widely prevalent. Dengue and Japanese encephalitis viruses are more widespread than West Nile virus, which was not known previously to extend east of India although recent survyes have shown that its range extends to Burma. Japanese encephalitis is frequent in most of South-East Asia but in India is found mainly in eastern and south-eastern parts of the country. Kyasanur Forest disease (KFD) and Langat viruses are the only tick-borne group B arboviruses definitely known to occur in the region, the former in India, the latter in Malaysia. KFD virus has been isolated only from a small focus in Mysore, although human and animal sera containing neutralizing antibodies to this virus have been found sporadically in widely scattered areas. Among the group A arboviruses, chikungunya and Sindbis have been detected in serological surveys, but the former has not yet been found in Malaysia.

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.

Immunopathologic Mechanisms in the Dengue Shock Syndrome

Abstract: Publisher Summary This chapter describes the immunopathologic mechanisms in the dengue shock syndrome (DSS). Immunopathologic mechanisms usually play a minor role in the pathogenesis of disease due to acute viral infections. The relative timing of virus replication and the immune response is a critical factor in determining the degree of damage done by immunopathologic mechanisms in virus diseases. The viruses associated with DSS include all four serotypes of dengue viruses. The same viruses also cause classic dengue fever, and benign undifferentiated febrile illnesses. The major pathophysiologic abnormality seen in DSS is an acute increase in vascular permeability. In typical cases, after a 3- to 6-day febrile period, clinical shock occurs due to loss of plasma from the intravascular space. The onset of the shock phase is acute, and the hematocrit rises sharply as plasma escapes through the endothelium. The hypovolemic shock can lead to tissue hypoxia, acidosis, hyperkalemia, and death if uncorrected. Replacement of plasma volume with colloid-containing solutions is an effective method of treatment which may be lifesaving.

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

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.

Simian Hemorrhagic Fever Virus

Abstract: Previous studies on the virology of the Sukhumi/64 and Bethesda/64 epizootics of simian hemorrhagic fever (SHF) are reviewed. Virologic investigation of 2 more recent epizootics (i.e. Davis/67 and Sussex/68 outbreaks) are described. Serologic studies revealed that all 4 known epizootics were caused by the same virus. Additional biophysical studies demonstrated that the buoyant density of SHF virus in CsCl2 and sucrose D2O gradients was 1.22 and 1.19, respectively. Electron microscopy of virus-infected cells revealed that unique lamellar structures precede the development of whole virions whose size corresponded to results previously obtained from Millipore filtration studies.