Early diagnosis of viraemia in some experimental arbovirus infections in mice

Viraemia was demonstrated by the indirect haemagglutination (IHA) test in newborn white mice infected with dengue type 1 and 2 and Japanese encephalitis viruses but not with Chikungunya virus. The IHA allowed the detection of viraemia in the flavivirus infections before the appearance of clinical symptoms of the disease and was strictly specific.

[Arbovirosis from Central African Republic: incidence, diagnosis in human pathology (author's transl)]

The authors report results obtained about human arboviroses studied in the laboratory of Institut Pasteur of Bangui from 1966 to 1979 in Central African Republic. 74 cases are described; 36 strains from different serological Casal groups have been isolated and, in 38 cases, a serological conversion have allowed a diagnosis. The peculiar conditions of virological and clinical diagnosis are discussed.

[Minor arboviral diseases in Central and West Africa (author's transl)]

Many arboviruses can cause febrile illness in man, with or without rash, quite apart from yellow fever and the aetiological agents of haemorrhagic fevers. Exanthema are one of the commonest signs. Neuro-vascular attacks frequently occur and in some cases meningitic complications can happen. Diagnosis is often difficult: viraemia is of short duration and complement fixing antibodies do not appear consistently in convalescent serum. In Central and West Africa, 19 different arboviruses have been implicated either by isolation or by serological conversion. Some were isolated from man for the first time.

[Tick-borne viruses in tropical area (author's transl)]

Arboviruses, transmitted by ticks and pathogenic to man in tropical areas, are discussed. They are considered according to, first the faunal region in which they can be found, then the type of syndrome they cause. The greater part is of little medical importance, some are noxious but of a rare occurrence (Thogoto, Wanowrie, Langat) or geographically restrained (Kyasanur forest disease), so the Crimean-Congo hemorrhagic fever is the only infection to show a notorius importance. As severe in the tropics of the oriental faunal region (Pakistan, India) as it is Europe, it seems to be of little importance in the afrotropical faunal region. Nevertheless, its severity remains to be ascertained by the means of extensive serological surveys and by taking in account this virus in presence of every hemorrhagic syndrome.

Comparison of haemagglutination inhibition (HI) and indirect fluorescent antibody (IFA) techniques for the serological diagnosis of certain flavivirus infections

Paired serum samples from 25 patients having clinical evidence of arboviral infections and 15 controls were examined for antibodies against dengue, Japanese encephalitis and West nile viruses by haemagglutination inhibition (HI) and indirect fluorescent antibody (IFA) methods. The two tests were comparable in specificity but the IFA test was found to be more sensitive than the HI test. Like the HI test, the antibodies detected by IFA test cross-reacted within the flavivirus group under test. Use of IFA test is recommended to detect flavivirus infections as the test is simple, sensitive and can be carried out rapidly.

Epidemic polyarthritis acquired in Fiji

Four cases of epidemic polyarthritis which was acquired in Fiji between April and July of 1979 are described. The manifestations of the illness were similar to those of the disease in Australia. Knowledge of the geographic distribution of this disease can be valuable in diagnosis, but it is likely that its range is not yet fully known.

[Sero-epidemiological survey of arbovirus diseases in the Bi-Aka pygmies of Lobaye, Central African Republic]

Sero-epidemiological survey for Arboviruses among Bi-Aka Pigmies of the Lobaye, Central African Empire. A sero-epidemiological survey has been conducted, in 1975-1976, among 349 nomadic Pygmies of the Lobaye area in the Central African Empire, to investigate the prevalence of arbovirus infections. The percentages of individuals with detectable antibodies were 9,5 % for Chikungunya, 13,5 % for Semliki Forest, 5,2 % for Sindbis; 11,7 % for Bunyamwera; 2,3 % for West Nile, 6,3 % for Uganda S, and 8,9 % for Yellow Fever. These results are similar to those found in 1964 by CHIPPAUX in a comparable group of Pigmies of the same area and confirm that the prevalence of arbovirus infections is lower in the nomadic pygmies of the same area and confirm that the prevalence of arbovirus infections is lower in the nomadic Pygmies than in the sedentary Pygmies as well as in the settled bantus of the Lobaye valley villages. Yellow fever specific antibodies detected in this non vaccinated population indicate that latent infections occur in human beings living in the depth of the tropical forest, from the natural sylvatic focus of yellow fever, which remains active as recently proven in the Central African Empire by virus isolations obtained from wild caught mosquitoes.

[The ecology and medical importance of the Tahyna Virus (author's transl)]

In 1958 a virus transmitted by a mosquito was isolated in the Slovakian village of Tahyna. Since this virus was unknown in Europe, a detailed study was begun. It was shown that this virus belonged to the California group of arboviruses and occurs in practically all European countries. It could very well be that young hares are the hosts for this virus, and that it multiplies in them. Foals and suckling pigs are also hosts and possibly also increase the virus. In patients observed so far, infection with the Tahyna virus appears with influenza-like symptoms. In some cases, meningoencephalitis and atypical pneumonia were observed.

Serum dilution neutralization test for California group virus identification and serology

The serum dilution neutralization test was evaluated for serological diagnosis of California group arbovirus infections and identification of virus isolates. The technical advantages and the degree of subtype specificity of the serum dilution neutralization test over the hemagglutination inhibition test and the complement fixation test were demonstrated with paired specimens from human cases, single human survey sera, and sentinel rabbit sera. Twenty-one virus isolates from various geographical areas of the United States were also used to evaluate the efficacy of the serum dilution neutralization test for specific virus identification.

Turkey meningo-encephalitis: a general review

Turkey meningo-encephalitis (TME), a neuro-paralytic disease of the adult turkey caused by an Arbovirus, was described in 1960 in Israel, and not yet reported elsewhere. The seasonal outbreaks caused a high morbidity and a mortality up to 80%. A tendency toward spread has been found in the last two years. The TME virus was attenuated sucessfully by adapting it to a new host, the Japanese quail, and a vaccine prepared with this attenuated virus is effective in immunizing turkeys to the disease.

[Improved hemagglutination and hemagglutination inhibition tests for arboviruses]

The capacity of formalinized goose erythrocytes to be agglutinated in interactions with arboviruses was studied. Formalinized goose erythrocytes were found to be as sensitive as native erythrocytes, and were used successfully for diagnosis of arbovirus infections and study of the immune structure of the human population and animals. The superiority of formalinized erythrocytes is determined by the duration of storage (2 years of the observation period) withoug any change in the capacity for agglutination.

Arbovirus infections in Sarawak: the role of the domestic pig

The possible role of pigs as arbovirus maintenance hosts and their importance as amplifier hosts was studied. Blood samples from 464 pigs of all ages collected in 1962 and 1964 were tested against 10 arboviruses. Antibodies to Japanese encephalitis and Getah viruses were particularly prevalent and their calculated monthly infection rates were 19-5% and 13-3% respectively. In 1969, 447 pigs were bled monthly throughout the year and the infection rates for Japanese encephalitis virus were calculated in pigs during the first year of life. Infection rates were not uniform throughout the year; the rate increases as the pig grew older and there was a marked seasonal increase in the infection rate in the period from November to January. This coincided with the seasonal major population peak of Culex tritaeniorhynchus following intense breeding of this mosquito prior to rice planting. It is suggested that, in Sarawak, the pig acts as a maintenance host of Japanese encephalitis in a cycle involving C. gelidus mosquitoes and also acts as an important amplifier host towards the end of the year in a cycle involving C. tritaeniorhynchus. It is further suggested that Getah virus is maintained in a similar cycle between C. tritaeniorhynchus and pigs.