Showing papers on "Dengue fever published in 1970"

Observations related to pathogenesis of dengue hemorrhagic fever. 3. Virologic studies of fatal disease.

Abstract: Virologic study of fatal dengue hemorrhagic fever (DHF) is a problem of special importance to an understanding of the pathogenesis of this disease. As opposed to experience in patients surviving DHF, virus isolations from fatal cases are extremely rare, three having so far been reported in the literature.`2 This report summarizes studies on autopsy materials submitted to the SEATO Medical Research Virology Department during the period 1962-64. the body was usually moved into a refrigerator until autopsy permission. The interval between death and autopsy was measured in the first 46 study cases and is shown in Table 1. These cases were all autopsied at the Children's Hospital. Organ sections were placed in separate containers and transferred to the Virus Laboratory on wet ice. They were then frozen and stored at-700 C. Venous blood was obtained from some patients with hemorrhagic fever who subsequently died. Collection of these specimens has been described.' In other instances heart blood was drawn immediately after the patient expired, placed at 40C. and brought to the laboratory. If not already hemolysed, the red cells were separated from serum. Serum was quick frozen in a dry-ice-alcohol bath and stored at-70°C. until tested. Twenty liver specimens were obtained immediately after death by use of Vim-Silverman needle. These tissues were immediately brought to the laboratory on wet ice.

Observations related to the pathogenesis of dengue hemorrhagic fever. II. Antigenic and biologic properties of dengue viruses and their association with disease response in the host.

Abstract: One of the hypotheses invoked to explain the occurrence of different diseases associated with dengue virus infection is that dengue viruses differ in virulence properties. Observations on virologically studied dengue fever and dengue hemorrhagic fever (DHF)\"'8 patients have reasonably established that both of these diseases are associated with dengue viruses of all known antigenic types. The possibility that virus strains within the same type differ in their virulence properties and that these differences might be genetically associated with surface antigen or other readily measured markers has not been examined. This hypothesis was the initiating motivation for this study. Using single lots of mouse immune ascitic fluids, we tested a large number of dengue viruses by a plaque reduction neutralization test and the results were compared with the disease response and geographic origin of virus strains. A few observations on biologic properties of the examined dengue virus strains are included. Plaque reduction test The production of LLC-MK2 monolayers, the techniques of plaque assay and the plaque reduction neutralization test have been given elsewhere.' In all tests, six repli-cate 2 oz. plaque bottles were used. All neutralization tests reported in this paper were performed by incubating serum and virus mixtures at 22-250C. for exactly 60 minutes. Reactions were stopped by dilution of serum-virus mixtures to 1:100 in chilled 0.75% bovine albumin-phosphate buffered saline, pH 7.8-8.0 (BAPS) or 20% heat inactivated agamma calf serum in phosphate buffered saline, pH 7.8-8.9. Residual virus was in-cubated on cell sheets for 90 minutes at 370C. before agar overlay.

Observations related to pathogenesis of dengue hemorrhagic fever. V. Examination of agspecific sequential infection rates using a mathematical model.

Abstract: Experimental studies of dengue infections in humans suggest that immunity to homologous virus challenge is probably of lifelong duration.' Individuals infected with one type of dengue virus and then exposed to a second serotype within 3-6 months may develop modified disease or no disease at all.' Studies of dengue infection in Bangkok have suggested that infection with one type of dengue virus sensitizes an individual so that subsequent infection with another type elicits a hypersensitivity reaction producing the dengue hemorrhagic fever (DHF) syndrome.2 Since at least four types of dengue viruses are simultaneously endemic in Bangkok, it is theoretically possible that hypersensitivity reactions could occur during the second, third or fourth heterologous infection. The limits of the interval between sensitizing and eliciting infections are unknown, but the evidence of short duration heterologous protection cited above plus the seasonal periodicity of dengue transmission in the tropics suggests that most DHF may result from heterologous infections occurring at an interval of one year or more.8\" It is the purpose of this paper to utilize the above observations in a study of mathematical models which permit prediction of age specific secondary or tertiary infection rates in populations exposed to three or four different dengue viruses. Results from models have been compared with available epidemiologic data, particularly age specific hemorrhagic fever hospitalization rates, to evaluate hypotheses concerning the number of infections and the interval between infections required to produce DHF.

Ecology and Control of Dengue Vectors on an Island in the Gulf of Thailand

Abstract: Entomological observations made on Koh Samui during an epidemic of dengue hemorrhagic fever in 1967 indicated that the densities of the populations of the 2 vector species, Aedes aegypti and Aedes albopictus , were directly related to the amount of rainfall during that period. The incidence of dengue virus infections in man and mosquitoes was also highest during the period of greatest precipitation. On Koh Samui A. aegypti was highly endophilic, while A. albopictus was exophilic, and there was very little overlap between the preferred habitats of the 2 species. Significant numbers of both species were observed to be taking multiple blood meals during their individual gonotrophic cycles. Effective control of the A. aegypti was achieved for a period of approximately 10 weeks in a village on the island by treatment of water storage containers with Abate and by ground applications of malathion fog. The results obtained suggest that such control measures would be effective in preventing dengue transmission by A. aegypti in Thailand.

A multipurpose serological survey in Kenya: 2. Results of arbovirus serological tests

Abstract: Arbovirus infections are of public health interest in East Africa, where a very widespread epidemic of o'nyong-nyong fever was reported in 1959-60 and where the threat of yellow fever, present in neighbouring areas such as Ethiopia, remains. Sera collected in a serological survey in Kenya were therefore tested for antibodies against 3 group-A arboviruses (chikungunya, o'nyong-nyong and Sindbis), 6 group-B arboviruses (Zika, yellow fever, West Nile, Banzi, Wesselsbron and dengue 1), and Bunyamwera virus. The sera were examined mainly by the haemagglutination-inhibition test but a small proportion were also subjected to virus neutralization tests.The results showed that the prevalence of arbovirus tnfection varies markedly from area to area in Kenya. All types of arbovirus infections were more frequent on the coast than on the dry plateau around Kitui and the Lake Victoria area, The only exceptions were o'nyong-nyong and chikungunya, which were found to be just as prevalent on the coast as in Nyanza, where an epidemic was reported in 1959-60. Yellow fever antibodies were found to be present in about half of the people living on the coast but practically absent from the other two areas. It was concluded that the yellow fever antibodies in the coastal area must be due either to vaccination or to cross-reactions with other group-B arboviruses.

Observations related to pathogenesis of dengue hemorrhagic fever. I. Experience with classification of dengue viruses.

Abstract: Two distinct syndromes associated with dengue virus infection are prevalent in tropical Asia; dengue fever, a benign disease characterized by fever, myalgia, leucopenia and a maculo-papular rash and dengue hemorrhagic fever (DHF), accompanied by fever, shock, hemorrhagic diathesis and a significant mortality.1 The dengue viruses, a group of antigenically related members of the Group B arthropod-borne virus family, are transmitted from man to man by the mosquito, Aedes aegypti. Multiple members of the group are known to be simultaneously transmitted in large urban areas of tropical Asia. Dengue disease syndromes of both types may occur concurrently, DHF usually is restricted to the indigenous population, while dengue fever may occur in both indigenous and non-indigenous residents of an area.\" When dengue hemorrhagic fever was first described in the Philippines, two new dengue viruses, types 3 and 4 were recovered from patients.' Shortly thereafter, dengue strains recovered from DHF patients in Thailand were tentatively designated types 5 and 6.5 As one explanation of the malignant type of dengue fever, it was suggested that dengue viruses had acquired virulence properties.6 A corollary to this hypothesis was that virulence and surface antigen were genetically linked and thus, the \"newer\" types of dengue viruses were the cause of the severe dengue syndrome. The hypothesis that DHF is due to a self-destructive host response has been proposed by Halstead and associates.7 They suggested that some persons are sensitized by their first dengue infection. In such a host the course

Virological study of an epidemic of febrile illness with haemorrhagic manifestations at Kanpur, India, during 1968.

Abstract: Several epidemics of febrile illnesses associated with haemorrhagic manifestations occurred in India during 1963 and 1964. These epidemics were restricted to the eastern coastal areas. However, in northern India, for the first time, a widespread epidemic of febrile illness associated with haemorrhagic manifestations occurred at Kanpur in 1968. In the present study, the virological findings of the epidemic are reported.The role of dengue type 4 virus in the epidemic is demonstrated by the isolation of the virus from a number of cases, including one with haematemesis, and conversion of antibody titres with dengue type 4 virus in the paired sera.

Protection against St. Louis encephalitis and West Nile arboviruses by previous dengue virus (types 1-4) infection.

Abstract: Summary Hamsters inoculated with Den-2 virus were shown to survive peripheral challenge with large amounts of WN virus. Dengue types 1, 3, and 4 gave less complete protection than Den-2. Cynomolgus monkeys with probable naturally acquired Den-2 neutralizing antibody were shown to be protected from a persistent viremia following SLE virus inoculation. Serological tests on both hamsters and monkeys were of the expected pattern but did not lead to an understanding of the specific mechanism involved in the cross protection. These results support epidemiological observations of the absence of severe epidemics of JBE, SLE, WN, and other Group B encephalitides in areas with endemic dengue.

A clinical and epidemiological study of an epidemic of febrile illness with haemorrhagic manifestations which occurred at Kanpur, India, in 1968

Abstract: An epidemic of febrile illness associated with haemorrhagic manifestations and shock occurred at Kanpur, India, during 1968. The epidemic was widespread in the city, involving about one-tenth of the population; cases were more frequent in thickly populated localities with poor sanitary conditions. Those affected were mainly adolescents and adults of both sexes and multiple cases occurred in families. The disease was characterized by the sudden onset of fever, associated with severe headache and low backache. A number of patients had bradycardia, vomiting and diarrhoea and macular skin rashes associated with itching. A small percentage of the patients had haemorrhagic manifestations in the form of haematemesis, haemoptysis, melaena, haematuria and bleeding per vaginum. The mortality was very low. Dengue type 4 virus has been implicated in the epidemic.

Studies on arboviruses in Egypt. II. Contribution of arboviruses to the aetiology of undiagnosed fever among children.

Abstract: Acute blood samples from 120 children, attending the fever hospital in Alexandria and complaining of fever, were collected and examined for haemagglutination-inhibiting (HAI) and complement-fixing (CF) antibodies against the following arbovirus antigens; Sindbis, West Nile (WN), yellow fever, dengue 1, sandfly fever, Quaranfil, Chenuda and Nyamanini. Positive reactions in the acute sera were only detected against Sindbis (4·3%) and WN (4·3%) antigens. The convalescent sera obtained from 48 of these children showed a pronounced HAI titre against WN antigen in 14·6% of them. The same sera showed a lower titre against yellow fever antigen (Asibi strain) which is due to cross-reaction between the two viruses. None of the acute or the convalescent sera showed CF antibodies against Quaranfil, Chenuda or Nyamanini antigens. The convalescent sera were not tested against dengue type 1 antigen. It is suggested that of the known arboviruses in Egypt, WN is the most important from the public health point of view.

Dengue virus plaque development in simian cell systems. I. Factors influencing virus adsorption and variables in the agar overlay medium.

Abstract: Chemical and physical variables influencing the plaquing of all dengue serotypes in two simian cell systems were studied. Calf serum in the nutrient overlay may be replaced by mouse ascitic fluid or bovine plasma albumin when employing the rhesus monkey kidney LLC-MK2 cell system for plaquing all dengue serotypes. Doubling the serum concentration in the overlay had little effect in modifying dengue types 1, 2, 3, and 4 plaque titers. Newborn agamma, 4-week-old and 8-week-old calf serum gave comparable titers with all dengue virus serotypes. Dengue virus titers, plaque size, and development time were unaffected by sodium bicarbonate concentrations ranging from 1.1 to 4.4 mg/ml of overlay. A twofold increase (0.00332 g%) in the amount of either autoclaved or filtered-sterilized neutral red reduced the dengue 2 virus titer as much as 2.2 logs. An increased Mg++ and decreased Ca++ concentration in the overlay medium increased the efficiency of the plaquing system.

Lymphocytes and Yellow Fever: I. Transient Virus Refractory State Following Vaccination of Man with the 17-D Strain

Abstract: Human lymphoeytes can support the replication of 17-D yellow fever virus when stimulated in vitro with phytohemaggiutinin. Between 7 and 11 days following vaccination with 17-D virus, peripheral lymphocytes lose their ability to support virus replication but regain this capacity by the 25th day post-vaccination.

Forest mosquitoes of the eastern Himalayan foothills of India.

Abstract: Several species of mosquitoes are vicious biters and are well known as important vectors of arboviruses. The mosquito-borne endemic diseases in India are malaria, filaria, dengue, haemorrhagic fever and Japanese-B encephalitis. It is likely that some of the viruses isolated from wild-caught mosquitoes whose identity has not yet been established may prove to be pathogenic to man.

Dengue virus plaque development in simian cell systems. II. Agar variables and effect of chemical additives.

Abstract: Dengue type 2 virus, strain New Guinea B, plaqued with equal facility and titer under overlays containing six different grades of commercial agar in the LLC-MK(2) cell system. Doubling the agar volume on LLC-MK(2) cell monolayers increased the plaque development time of dengue type 1, strain Hawaii. Storage of agar at 56 C reduced or totally abolished dengue type 4, strain H-241, plaque titer in LLC-MK(2) cells. The influence of six known virus plaque-enhancing compounds on plaque development of all dengue virus serotypes was studied in two continuous simian kidney cell lines, LLC-MK(2) and Vero. In the absence of any chemical additive, plaque development of all dengue serotypes was more rapid (4 to 10 days) in the LLC-MK(2) line than in the Vero line (6 to 13 days). Increased plaque development time of type 1, strain Hawaii, by pancreatin and plaque-size doubling of dengue types 1 and 4 was the only advantage conferred by the addition of six chemical additives in the LLC-MK(2) cell system. Dengue types 1 and 6 failed to plaque in the Vero cell system unless aided by a plaque-enhancing compound; plaques of dengue types 2, 3, 4, and 5 appeared sooner (2 days) and were increased in plaque diameter. The optimal DEAE concentration for plaquing dengue type 1, strain Hawaii, was 100 mug/ml; plaque development either failed at lower concentrations or was inhibited at higher (200 mug/ml) concentrations.

Survival of arboviruses in Aedes albonotatus, a peridomestic Bahaman mosquito.

Abstract: SummaryExperimental infections with chikungunya and dengue 2 viruses did not persist in Aedes albonotatus. On the other hand, titers increased in A. aegypti and transmission to suckling mice occurr...

Antigenic and biological classification of dengue viruses.

Abstract: : Dengue viruses are the cause of two distinct diseases, dengue fever (DF), a mild and self limited illness and dengue hemorrhagic fever (DHF), a severe disease with an appreciable mortality rate This investigation addressed itself to the hypothesis that two subpopulations of dengue viruses exist, virulent and avirulent, and that the virulence of a dengue infection is correlated with identifiable antigenic markers on the virus In addition, an attempt was made to evaluate in sub-human primates the hypothesis that a second dengue infection is modified by host factors to result in more severe disease response (Author)