Showing papers on "Dengue fever published in 1980"

Dengue haemorrhagic fever--a public health problem and a field for research.

Abstract: Dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS) is an enigmatic and growing public health problem which is confined at present to countries of South-East Asia. Since 1956, over 350 000 patients have been hospitalized and nearly 12 000 deaths have been reported. Dengue viruses, a group of four flaviviruses, are transmitted to man by Aedes aegypti. Currently, dengue viruses are actively transmitted in 61 countries which circle the globe in the tropical zone and have a combined population of 1500 million. Because the precise antecedents to DHF/DSS are unknown, the public health hazard posed by this syndrome is potentially worldwide. Epidemiological studies in South-East Asia clearly link DHF/DSS to individuals who have had a previous dengue infection or who have acquired maternal dengue antibody. Such antibody may serve as an opsonin, enhancing dengue virus infection of mononuclear phagocytes-the type of cell in man to which dengue infection may be confined. Antibody-mediated infection of these cells is the central concept in the hypothesis of immune infection enhancement. This hypothesis provides a conceptual framework for design of future research. There is an urgent need for a comprehensive identification of "risk factors" in DHF/DSS. This research could be approached by undertaking comparative prospective epidemiological studies in dengue-endemic areas with and without DHF/DSS. Although important progress is being made in the development of attenuated dengue vaccines for each dengue type, a clearer understanding of the pathogenesis of DHF/DSS may be required to provide guidelines for safe and lasting immunoprophylaxis in man.

Enhancement of Dengue Virus Infection in Monocytes by Flavivirus Antisera

Abstract: Enhanced dengue 2 virus (D2V) infection in suspension cultures of human peripheral blood mononuclear phagocytes (PBL) produced by subneutralizing concentrations of dengue antisera has been described previously. In this study, the enhancement phenomenon was found to be a general property of representative flavivirus antisera. All except one of 24 antisera, which had been raised by 1-3 injections of flaviviruses in rabbits, enhanced the growth of dengue 2 virus in human PBL. Flavivirus antisera showing the greatest level of cross-reactivity against a battery of 42 flavivirus antigens in the hemagglutination-inhibition test were most potent in enhancing dengue replication in PBL cultures. Cross-neutralizing reactivity did not relate to enhanced D2V infection. However nearly one-half of studied flavivirus antisera neutralized D2V at dilutions of 1:10 or 1:20. Heterotypic D2V neutralizing antibody could serve as a "brake" on infection enhancement in vivo. Observations should be made in the field to look for possible enhancement of dengue infection in heterotypic flavivirus immunes.

Isolation of Dengue Viruses from Peripheral Blood Leukocytes of Patients with Hemorrhagic Fever

Abstract: Dengue viruses were isolated by a plaque technique in LLC-MK2 cells from washed peripheral blood leukocytes of patients with hemorrhagic fever. In comparison with plasma, the use of peripheral blood leukocytes permitted greater than three times the recovery rate of viruses, allowed for the isolation of strains of virus from patients with high serum levels of antibody to dengue virus, and extended the period of detectable viremia. The use of peripheral blood leukocytes was especially useful for isolation of viruses from patients with hemorrhagic fever, in whom antibody titers were generally quite high during the acute phase of the disease. This method is recommended for use by laboratories with access to the appropriate acute-phase specimens. Of the peripheral blood leukocytes, adherent monocytes appeared to be the cells most likely affected; however, involvement of atypical lymphocytes, which are commonly found in patients with hemorrhagic fever, or polymorphonuclear leukocytes could not be excluded by this study. Only a small number of infected centers could be identified by infectious-center assays, but the marked augmentation of recovery of virus with the use of peripheral blood leukocytes indicated the presence in patients of a subpopulation of cells that permit dengue virus infection.

An outbreak of type 2 dengue fever in the Seychelles, probably transmitted by Aedes albopictus (Skuse).

Abstract: Between December 1976 and September 1977 the Seychelles group of islands in the Indian Ocean was struck by an extensive epidemic of dengue fever. The peak of the epidemic was in the last week of February. Type 2 dengue virus was isolated from patients and mosquitos. Aedes albopictus was the sole vector. The clinical picture was that of classical dengue. Haemorrhagic fever and the shock syndrome were not observed.Absenteeism from schools and offices, anamnestic questioning, and prevalence of antibodies in sera collected after the epidemic was over, indicated that approximately 75% of the population had been infected. Serological evidence was obtained of an epidemic of dengue in the islands more than 40 years earlier. This was confirmed by archival records.

Transmission of dengue 1 and 2 viruses in Greece in 1928.

Abstract: In August-September 1928 approximately 650,000 residents of Athens and Piraeus contracted dengue fever, and 1,061 died. We were interested in the etiology of this severe epidemic in which many cases resembled dengue hemorrhagic fever or the dengue shock syndrome, and have attempted a retrospective seroepidemiological study. Serum specimens were obtained from 111 residents of Athens or Piraeus who were born in 1927 or 1928, and were studied by plaque reduction neutralization test for antibodies to dengue 1–4 viruses. Of 75 persons born in 1928, 20 (27%) had monospecific dengue 1, 10 (13%) had monospecific dengue 2, and 1 (1%) had dengue 1 and 2 neutralizing antibodies. When prevalence of neutralizing antibody was analyzed by month of birth in 42 individuals, evidence of both dengue 1 and 2 infections was found in persons born in January–July, but only dengue 2 antibody was detected in those who were born after July. This study dates dengue 1 and dengue 2 transmission to 1928, allowing for the possibility that sequential infections with these viruses could have played a pathogenetic role in the outbreak.

Dengue-2 vaccine: preparation from a small-plaque virus clone.

Abstract: The S-1 clone of dengue type 2 virus was used for the preparation of a live-attenuated vaccine after passage in DBS-FRhL-2 cell culture. The vaccine virus had a relatively higher replicative capacity at superoptimal temperatures than its precursor virus, S-1, passaged in primary green monkey kidney cells (S-1 PGMK). There was also a tendency for the S-1 vaccine virus to exhibit leakiness at increased temperatures. Another in vitro marker, replication in monkey peripheral blood leukocytes, indicated less host restriction for the S-1 vaccine in comparative assays with S-1 PGMK virus. Mouse virulence appeared to remain stable on passage in DBS-FRhL-2 cells, whereas monkey immunogenicity decreased. Cautious trials of the dengue type 2 S-1 vaccine in humans are indicated.

Inhibition of dengue virus replication by amantadine hydrochloride.

Abstract: The effect of amantadine hydrochloride (1-adamantanamine hydrochloride) on dengue virus replication was examined in vitro. Amantadine decreased the titers of all four types of dengue viruses grown in LLC-MK2 cells by greater than 90% at concentrations of 50 micrograms/ml. There was no evidence for any cytopathic effect of the drug at concentrations less than 100 micrograms/ml. Studies of the time of addition showed that the antiviral effect was maximal when drug was added to virus cultures immediately after the viral adsorption period. In addition, amantadine caused a marked reduction in the growth of dengue virus type 2 in both human and rhesus peripheral blood leukocytes without affecting cell viabili ty. These findings demonstrate that amantadine significantly inhibits the replication of dengue viruses in vitro and indicate a need to determine the efficacy of this drug against dengue virus infections in vivo.

Dengue-2 Vaccine: Viremia andImmuneResponses inRhesus Monkeys

Abstract: Studies were undertaken in Indian rhesus monkeys (Macaca mulatta) to determine the safety, potency, immunogenicity, and mosquito infectivity of a small-plaque, temperature-sensitive variant of dengue type 2 (DEN-2) virus, a vaccine candidate. Fifteen monkeys were inoculated subcutaneously with the vaccine virus, ten receiving 10(3.1) plaque-forming units (PFU) and five receiving 10(4.5) PFU. After primary immunization, viremia was detected in only one monkey, a recipient of the higher dose of vaccine. The recovered virus had the same growth characteristics as the vaccine strain. Aedes aegypti mosquitoes did not become infected when they were allowed to feed on monkeys that received the lower dose of vaccine. As expected, the immunization produced no evidence of illness in any of the animals. A dose response to vaccine was detected; all five of the high-dose recipients developed neutralizing antibodies, whereas only five of ten low-dose recipients did so. In both groups, neutralizing antibody was often transient. Its presence at 30 days did not always correlate with protection from viremia in those animals challenged 4 to 6 months after vaccination with wild-type DEN-2 virus. However, immunized animals developed anamnestic antibody responses after challenge, and none demonstrated adverse effects to infection. Reimmunization of monkeys 4 months after primary immunization led to the production of low-titered but persistent neutralizing antibody which protected the animals from a wild-type virus challenge.

Dengue-2 Vaccine: Viremia and Immune Responses in Rhesus Monkeys

Abstract: Studies were undertaken in Indian rhesus monkeys (Macaca mulatta) to determine the safety, potency, immunogenicity, and mosquito infectivity of a small-plaque, temperature-sensitive variant of dengue type 2 (DEN-2) virus, a vaccine candidate. Fifteen monkeys were inoculated subcutaneously with the vaccine virus, ten receiving 10(3.1) plaque-forming units (PFU) and five receiving 10(4.5) PFU. After primary immunization, viremia was detected in only one monkey, a recipient of the higher dose of vaccine. The recovered virus had the same growth characteristics as the vaccine strain. Aedes aegypti mosquitoes did not become infected when they were allowed to feed on monkeys that received the lower dose of vaccine. As expected, the immunization produced no evidence of illness in any of the animals. A dose response to vaccine was detected; all five of the high-dose recipients developed neutralizing antibodies, whereas only five of ten low-dose recipients did so. In both groups, neutralizing antibody was often transient. Its presence at 30 days did not always correlate with protection from viremia in those animals challenged 4 to 6 months after vaccination with wild-type DEN-2 virus. However, immunized animals developed anamnestic antibody responses after challenge, and none demonstrated adverse effects to infection. Reimmunization of monkeys 4 months after primary immunization led to the production of low-titered but persistent neutralizing antibody which protected the animals from a wild-type virus challenge.

Dengue hemorrhagic fever in Malaysia: the 1973 epidemic.

Abstract: The first major Malaysian epidemic of dengue hemorrhagic fever with severe manifestations occurred in 1973, with 969 reported cases and 54 deaths. In a detailed study of 138 clinically diagnosed and laboratory confirmed cases at the General Hospital in Kuala Lumpur, hemorrhagic manifestations were observed in 68.7% and shock in 18.1% of the patients. The cases occurred mainly from May to September, largely in urban and suburban areas of the majority of the states in the country. A main focus of infection was Jinjang, a heavily populated outlying district of Kuala Lumpur, where unusually high incidences of morbidity, severe disease and mortality were seen. Severe disease was seen mostly in children under the age of 15 years, although a significant number of adults suffered milder illnesses. The Chinese population was chiefly affected, due to their living in crowded, low-income housing where the vector, Aedes aegypti, occurred in the greatest numbers. All four dengue types were recovered during the epidemic period, although dengue 3 (DEN-3) was incriminated as the major epidemic type. Entomological data revealed high indices of A. aegypti throughout the country and left little doubt that this epidemic was aegypti transmitted. Spraying and fogging operations were carried out in attempts to control vector populations.

Serological and virological studies on patients with dengue hemorrhagic fever (DHF) in Chanthaburi province, Thailand. I. Serological studies on paired sera from DHF patients by neutralization (N), hemagglutination inhibition (HI) and staining tests.

Abstract: Twenty paired sera were collected from DHF patients admitted to the provincial hospital of Chanthaburi, Thailand in 1978. They were tested by the N and HI tests and a newly developed staining test against all four serotypes of dengue (DEN) virus and Japanese encephalitis (JE) virus. Four patients were demonstrated to be cases of primary DEN infection and the other 16 to be cases of secondary DEN infection. The serotypes of recent DEN infections were easily determined by the N test in cases of primary infection, but were difficult to determine in cases of secondary infection because of the strong cross reactions among DEN serotypes. These cross reactions seemed to be due to subgroup-specific antibody, which reacts with all 4 serotypes of DEN virus in the N test. However, acute phase sera from some patients with the secondary type of antibody response reacted monospecifically in the N test, indicating the serotype of the primarily infecting viruses.

Kinetics of peripheral blood leukocyte alterations in Thai children with dengue hemorrhagic fever.

Abstract: Peripheral leukocytes from 16 Thai children with dengue hemorrhagic fever were examined to determine the leukocyte composition on the day of presentation and on convalescent days 15 and 30. Mononuclear cells were isolated each time, and the concentrations of T, B, Fc receptor-bearing, and "null" cells were determined. On the day of hospitalization, in comparison to convalescent values, there was a significant increase in total lymphocytes, primarily due to concentrations of atypical lymphocytes. There was a significant loss of T cells with an increase in non-T, non-B, non-Fc receptor-bearing null cells. There were no changes in the concentrations of monocytes, B cells, or Fc receptor-bearing cells when acute and convalescent values were compared. During the convalescent period, a progressive increase in eosinophils was noted. Also, on day 15 but not on day 30 of the convalescent period, an increase was observed in the total leukocyte number due to an increase in granulocytes. There results indicate that in Thai children with dengue hemorrhagic fever, there are major shifts within several component cell subpopulations of the immune system.

T Suppressor Cells: Role in Dengue Hemorrhagic Fever and Dengue Shock Syndrome

Abstract: The hypothesis presented envisages dengue virus infection in a host with preexisting parasitic infection. The dual infections may produce alterations in the immunoregulatory system that would lead to depletion of T suppressor cells. The resultant augmented production of IgG and IgE may be responsible for type III and type I hypersensitivity reactions, respectively.

Epidemiological investigation for arboviruses in Jamaica, West Indies.

Abstract: Arbovirus investigation in Jamaica was undertaken between 1960 and 1975. Serological studies showed that antibodies to dengue type virus and St. Louis encephalitis virus (SLE) were prevalent throughout the island for several years. In urban communities, the incidence of dengue antibody was higher than for SLE; however, in children under 10 years of age antibody to both viruses was rarely present. In rural areas, SLE was prevalent in adults and children. This virus was isolated from Culex nigripalpus (mosquitoes) and from a nestling Mockingbird, Mimus polyglottos, in the same rural area. Dengue type 3 and type 4 were isolated from the sera of patients in an urban area, during two epidemic periods, 1963 and 1968. No other group B arbovirus was encountered on the island. Group A arbovirus was virtually absent prior to the eastern equine encephalomyelitis outbreak of 1962. That virus was isolated from brain tissue of humans and equines. Two strains of Cache Valley virus from mosquitoes, Anopheles grabhami, one strain from Aedes taeniorhynchus, and a strain of Wad Medani virus from a tick, Amblyomma cajenense, were also isolated.

Transovarial transmission of Murray Valley encephalitis virus by Aedes aegypti (L.).

Abstract: In laboratory studies, Murray Valley encephalitis virus was transmitted transovarially by orally infected Aedes aegypti to approximately 1.5% of both adult male and female progeny.

Studies on dengue 2 virus infection in cyclophosphamide-treated rhesus monkeys

Abstract: Dengue 2 virus (D2V) replication has been demonstrated in cultured primate mononuclear phagocytes, mitogen treated lymphocytes and lymphoblastoid cells. To determine which of these cell types might play an important role in sustaining infection in vivo, nine rhesus monkeys were immunosuppressed with cyclophosphamide and then infected with D2V. Maintenance doese which held total white blood cell counts to <3000/mm3 ablated both primary and secondary antibody responses. Six successfully immunosuppressed animals circulated virus and infected monocytes in blood for prolonged periods. Virus was recovered from lymphatic organs and visualized in tissue mononuclear leukocytes in two subjects dying during the experimental period. The results argue against the hypothesis that lymphoblasts play an important role in dengue virus infection but are consistent with the possibility that mononuclear phagocytes are the site of viral replication in vivo.

Serotyping of dengue viruses by an immune adherence hemagglutination test.

Abstract: An immune adherence hemagglutination test was used to type dengue viruses grown in LLC-MK2 cells and whole mosquitoes. The test was found to be more sensitive than the complement fixation test for that purpose.

In vitro studies of the normal human B lymphocyte receptors for preformed soluble dengue antigen-antibody complexes.

Abstract: Preformed soluble dengue antigen-antibody with or without complement complexes could bind to the surface of human lymphocytes via IgG (Fc) or complement receptors respectively. It may be that these lymphocytes were B lymphocytes not T lymphocytes. Dengue antigen or antibody alone will not attach to the surface of those cells. It is emphasized that dengue antigen-antibody complexes can form in the circulation and some will bind to the surface of the B lymphocytes in vivo and play a significant role in the pathogenesis of dengue haemorrhagic fever. In addition mice could develop glomerulonephritis by injection with preformed soluble dengue antigen-antibody complexes. These mice showed proteinuria and deposits of the immune complexes in the glomeruli of the kidneys.

Geographic medicine for the practitioner

Abstract: 1. Prevention of Exotic Diseases: Advice to Travelers.- Viral Infections.- 2. Acute Viral Hepatitis.- 3. Major Tropical Viral Infections: Yellow Fever, Dengue, and Hemorrhagic Fevers (Arena and Ebola).- Bacterial Infections.- 4. Cholera.- 5. Leprosy.- 6. Plague.- 7. Shigellosis.- 8. Tuberculosis.- 9. Typhoid Fever.- Protozoan Infections.- 10. Amebiasis.- 11. Giardiasis.- 12. Leishmaniases.- 13. Malaria.- 14. Toxoplasmosis.- 15. African Trypanosomiases.- 16. American Trypanosomiasis.- Helminth Infections.- 17. Ascariasis and Toxocariasis.- 18. Echinococcosis.- 19. Enterobiasis.- 20. The Filariases.- 21. Flukes: Liver, Intestinal, and Lung.- 22. Hookworm.- 23. Schistosomiasis.- 24. Strongyloidiasis.- 25. Tapeworms.- 26. Trichinosis.- 27. Trichuriasis.

Serological and virological studies on patients with dengue hemorrhagic fever (DHF) in Chanthaburi Province, Thailand. II. Serological characteristics of viruses isolated from DHF patients using a clone of Singh's Aedes albopictus cells.

Abstract: Four strains of dengue (DEN) virus were isolated using C6/36 cells, a clone of Singh's Aedes albopictus cells, from acute phase sera of DHF patients in Thailand in 1978. The isolates grown and passaged in C6/36 cells were not neutralized appreciably by standard rabbit antisera against each of the 4 types of DEN virus, but their serotypes could be identified by complement fixation (CF) tests. After the 4th or 10th passage in suckling mouse brain (SMB), however, three of the four strains showed type-specific reactions in neutralization (N) tests against the standard antisera. In cases of secondary infection, the highest N titer in the convalescent phase sera was demonstrated not against the isolated serotype, but against the serotype considered to have caused primary infection. Moreover in cases of secondary infection, the convalescent phase sera showed a significantly lower N titer against the newly isolated strain derived from the same patient than against the corresponding prototype standard virus. This phenomenon was not observed in a single case of primary infection.

Effect of experimental dengue virus infection on humoral and cell-mediated immune response to thymus-dependent antigen.

Abstract: Mice injected with dengue vims showed a depressed primary and secondary humoral immune response to SRBC as measured by the number of antibody-forming cells, haemagglutinin and haemolysin titres. The t

[Dengue. I. Historical antecedents; etiological agents; clinical picture].

Abstract: A bibliographic review of the dengue virus involving the 1952-1978 period and including viral characteristics (serotypes, physical and biological properties, susceptibility within different biological systems, antigenic characteristics, chemical constitution and viral multiplication) and the clinical picture of the disease is made.

Hemagglutination-inhibiting immunoglobulin A antibody in the serum of patients with dengue hemorrhagic fever.

Abstract: In convalescent-phase sera of patients with dengue hemorrhagic fever, hemagglutination-inhibiting (HI) antibody of immunoglobulin (Ig) A class, in both monomeric and oligomeric forms, was detected. It was found to be less type-specific than IgM HI, and as broadly cross-reacting as IgG HI antibodies.

Dengue haemorrhagic fever in Singapore.

Abstract: The history of dengue haemorrhagic fever as distinct from dengue fever in South-East Asia is traced. The epidemiology of the disease in the various countries is contrasted with that in Singapore since DHF first appeared on the scene in South-East Asia. From this survey, it is concluded that the dengue haemorrhagic fever is a new disease presentation, and its fate in SE Asia depends on the immunological state of the community, attempts at vector control, and probably antigenic variation in the various types of dengue virus. The pathogenetic mechanisms are discussed in detail. Diagnosis is presented with a detailed discussion of diagnosis of the pre-shock stage. Finally, the management of dengue haemorrhagic fever is discussed.

Cytopathic and pathogenic properties of dengue type 2 virus reproduced in quail embryo fibroblast cultures.

Abstract: Quail embryho fibroblast cultures are able to reproduce dengue type 2 virus up to high titres measured by TCID50 values. The reproduced virus at low passage levels was antigenically closely related to the original virus reproduced in newborn mouse brains in vivo, but was loosing its virulence for these animals.

Togavirus infection in rural Thailand.

Abstract: Hemagglutination inhibition tests for antibody against chikungunya virus and the four dengue viruses were performed on a rural Thai village population. The 50% and 90% prevalence indices fell at about ages 3 and 15 for dengue virus exposure. This is considerably earlier exposure than comparable urban populations. The prevalence of chikungunya virus antibody was also age related with 50% prevalence at about age 45.

[Results of an entomological survey of mosquitoes (diptera:Culicidae) in Hermit Islands and Wuvulu Island (Papua, New Guinea)].

Abstract: An entomological survey conducted on Wuvulu Island and Maron Island, Hermit group, Papua-New Guinea, in August 1975, 1976 and 1978, shows the presence of eight mosquito species: Anopheles (C.) farauti, Aedes (S.), hebrideus, A. (F.) notoscriptus, A. (V.) lineatus, A. (L.) dasyorrhus, Culex (C.) sitiens, C. (C.) pipiens fatigans and Armigeres breinli. The potential medical significance of these mosquitoes is discussed, with reference to malaria, dengue and filariasis.