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William C. Reeves was invited to Australia in 1952 to take part in field studies of Murray Valley encephalitis. The results of his work led to various hypotheses which directed arbovirus research in Australia for a generation. That and the people he influenced in Australia made him a major figure in the development of Australian arbovirus research.
As a complement of the study of the epidemiology of the arboviruses in Central Africa a survey of tick borne viruses has been done, in the Central African Republic, from December 1972 to June 1974; 15.103 ticks were collected, mainly from cattle at the slaughterhouses. They include: 10.085 Ambylomma variegatum, 4.113 Boophilus, 542 Rhipicephalus and 363 Hyalomma. From 892 monospecific pools inoculated into baby mice, 98 isolates of virus were obtained. Among the 57 isolates which have been fully identified (the identification of 41 other isolates is still in progress), 4 different serotypes of arbovirus have been found: Dugbe virus has been the most frequently found with 45 isolates from A. variegatum and I from B. decoloratus; this virus, previously isolated from human cases in Central African Republic in 1967 and 1970 has been isolated from a new human case in 1973. One isolate of CHF/Congo virus has been obtained from Hyalomma nitidum, but this virus has not yet been isolated from human beeings in C.A.R. The two other tick borne viruses isolated during this survey are Jos virus (9 isolates) and Bhanja virus (I isolate), all of them from A variegatum.
Seroepidemiological studies revealed the existence of a population stratum immune to West Nile and Sindbis viruses in the Saratov region. Screening of 218 sera showed that the stratum immune to arboviruses increased from 1998 to 2000. The incidence of antibodies to Batai and Sindbis viruses was the highest. Activation of natural foci of these arboviruses can lead to exacerbation of the epidemic situation in the region.
The territorial spread of Tahyna, Batai, Sindbis, West Nile fever and Crimean-Congo hemorrhagic fever viruses throughout the Saratov region in 1998 - 2000 was analyzed. The characteristics of the epizootic activity of the natural foci of these arboviruses in different landscape zones (temperate forest-steppes, steppes and semi-deserts) were calculated. The species composition of small mammals, the natural reservoirs of the causative agents of arbovirus infections, was determined.
The paper contains methodical basis of ecovirological zoning in the analysis of the problem of interrelation between climatic changes and the activity of natural nidi of arboviral infection. The authors offer an original hieroglyphic system of cartographic signs of arboviruses and a map of prevalence of arboviruses in various landscape zones of Noth Eurasia (within the boundaries of the former USSR.) They analyze the three main cartographic approaches to ecovirological zoning of natural territorial complexes, which imply analysis of a ralation to a landscape, conjugated component analysis, and paleographic reconstruction analysis.
Sera from 269 wild rabbit (Oryctolagus cuniculus L.) trapped in 1985 and 1986 in Camargue and Vaucluse, France, were studied for antibody against 9 arboviruses. By inhibition haemagglutination test, positive reactions were found only against West-Nile (0.37%). By complement fixation test, antibodies were detected against Eyach (0.92%) and Tribec (0.46%). These results are discussed according to arboviruses isolated in France, to previous serosurveys in rabbits and other mammals and to potential vectors known to occur in France. Potential impact on rabbit population is also discussed.
An epidemiologic and serologic study of arboviruses was done in 1972 in the basin of Lake Rudolf. The main object of this study was to demarcate the southern limit of the yellow fever epidemic which occurred from 1959 to 1962 in Southern Sudan and Ethiopia. Other purposes were to contribute to the inventory of arboviruses and their distribution in this region. The ethnic groups were studied: the Nyangatom and the Dassanetch in Ethiopia and the Turkana in northern Kenya. The results of tests on sera of the Nyangatom and the Dassanetch are practically identical: a high percentage of positive tests for group B. The Turkana on the other hand show a low percentage of positives. This is attributed to differences in the climatic characteristics of the two regions. The serological results suggest the presence of West Nile virus in the geographical areas inhabited by the three ethnic groups. The presence of Wesselsbron and probably Uganda S virus is suspected. Circulation of these viruses could be explained by the presence of Culex univittatus and other mosquitoes. As for yellow fever, the results suggest that the virus did not reach the areas studied, probably because of absence of efficient vectors.
Sixty-two sera horse collected from two stables at Lagos, Nigeria, were tested for complement fixing antibody to 8 arbovirus antigens; Chikungunya, Igbo-Ora, Yellow fever, Wesselsbron, West Nile, Potiskum, Uganda S and Rift Valley fever. Ten per cent of the horse sera examined contained CF antibody to one or more of the test antigens and indicated considerable arbovirus activity in the two stables. Reactions with flavivirus antigens were most common and the highest antibody titres were obtained with Wesselsbron and Yellow fever viruses. Eleven per cent of the sera tested reacted with alphavirus antigens while 10 per cent were positive for Rift Valley fever virus CF antibodies.
Serologic surveys of wild and domestic birds, wild mammals, and horses were conducted during arbovirus field studies in Argentina from 1977 through 1980, a non-epizootic interval. The prevalence of neutralizing antibodies to eastern equine encephalitis (EEE) was consistently higher than to western equine encephalitis (WEE) virus in all species and all areas. The presence of antibodies in short-lived avian species and in young unvaccinated horses and the demonstration of seroconversions in horses during the period, indicated that these viruses are either enzootic in, or annually reintroduced into, Argentina. Antibodies to AG80-646, a new subtype of WEE virus isolated in the subtropical north (Chaco Province) from Culex (Melanoconion) mosquitoes, were found in horses and rodents in that region. Antibodies to the TC-83 strain of Venezuelan equine encephalitis (VEE) virus were found in all areas studied. The presence of antibodies in some horses was probably related to vaccination, but the demonstration of seroconversions in sentinel horses and of antibodies in birds and wild mammals indicates active transmission of VEE virus. In 1980 a new enzootic subtype of VEE virus (AG80-663) was isolated from mosquitoes in Chaco; neutralizing antibodies to this virus were prevalent in horses and rodents in this area. Infections with Aura and Una viruses were most common in the subtropical northern provinces. Infection with St. Louis encephalitis was prevalent and widespread, and birds, principally passerine and columbiform species, appear to be the principal hosts. An interesting and unexplained finding was the absence of arbovirus antibodies, in particular SLE antibodies in house sparrows (Passer domesticus). Antibody prevalences in horses exceeded 50% in all areas, and 12% of horses surveyed in Santa Fe Province developed antibody in a 17-month period. Antibodies to other flaviviruses were rare. A high prevalence of immunity to Maguari virus was found in horses; this agent is considered to be a potential equine pathogen. Antibodies to 2 new viruses, Barranqueras and Resistencia, which had been isolated from Cx. (Melanoconion) in Chaco Province, were found in rodents there. Immunity to Gamboa group viruses was prevalent, and birds were implicated as principal hosts.
The bioecological parameters which are of special importance in the epidemiology of Dengue, Yellow Fever, and other arboviruses are discussed. Three levels are retained: the nature of Aedes aegypti-man contacts, the susceptibility of the mosquito to the pathogen and multiplication of the latter, and the transmission. The trophic preferences, the density variations, the daily survival rate, the egg diapause, and man influences are the main vector-dependent ecological factors. Temperature and genetical nature of viral and mosquito strains are particularly important in susceptibility and multiplication studies. Efficacy of the oral transmission is also temperature-dependent and mainly genetically determined. The true natural role of transovarial transmission is not yet well understood. Thus, the breaking up and/or prevention of epidemics would be possible only with a thorough knowledge of the relation between the above biological factors and the epidemiological situation. A list is provided of the naturally or experimentally Aedes aegypti transmitted arboviruses (103), protozoans (5) and filaria (20).
19 arboviruses pathogenic for human are present in the Central African Republic (CAR) where serologic data indicate an active circulation in human population. In most cases the clinical picture of infection is mild. However 3 arbovirus were recently involved in fatal cases: in 1983 West-Nile virus has been isolated in 4 patients with hepatitis. 2 fatal cases of Yellow Fever occurred in 1985 and 1986, and from 1983 to 1986 Rift Valley Fever virus was isolated in patients who died from hemorrhagic fever. This new situation requires to carry on an epidemiological survey and studies on virus pathogenicity.
Aedes albopictus is an efficient vector of the four dengue viruses, and it is also capable of transovarially transmitting these viruses. Aedes albopictus can also serve as a host and/or vector of several additional arboviruses, some of which are of considerable medical or veterinary importance. This review compiles previously published studies that have demonstrated an experimental or natural association between Ae. albopictus and specific arboviruses.
2,457 serum samples collected during an epidemiological survey on treponematosis in Senegal by the W. H. O. IR051 team in five areas of Senegal between 1972 and 1975 were studied for arbovirus antibodies using hemagglutination inhibition test. In addition 998 were studied using CF test and 1012 in neutralization test with yellow fever virus. The prevalence of arbovirus antibodies is important in all the country and does not vary basically between the different areas. In group A, chikungunya antibody is the most frequent and Sindbis antibody was found only in areas where migrant birds are resting. There is evidence of recent yellow fever infection in Upper Casamance and in Eastern Senegal. Most of the children are not immune and have to be immunized. Zika and Wesselsbron viruses show activity in all the areas and West-Nile, as Sindbis, is related to areas where birds are numerous. Bunyamwera virus activity is low.
The results obtained in the Institute of Virology by the study of arboviruses in Romania are reviewed. Isolation of tick-borne encephalitis virus and detection of specific serum antibodies in humans, animals and migratory birds demonstrate its presence on the territory of Romania. Serum antibodies could also be detected to other three flaviviruses (West Nile, Ntaya, dengue types 1, 2, 3), though none of them could be isolated in our country. However, isolation of Kemerovo and Tahyna viruses and detection of antibodies to these viruses as well as to Calovo virus draw attention to the possibility of human infections with arboviruses belonging to Kemerovo, California and Bunyavirus groups.
A survey of the frequency of hepatitis B markers in 258 subjects from Kavango, northern South West Africa/Namibia, was undertaken during February - May 1983. The hepatitis B surface antigen and hepatitis B e antigen carrier rates were 13,6% and 2,7% respectively. Only 1,9% of the subjects were negative for all the markers tested, indicating that infection had been present at some stage in 98,1% of the sample. No known transmission method of the virus seems to fit this high exposure rate. The possibility that arthropod transmission of the virus may play a role in the epidemiology of the disease in Kavango is being investigated. All subjects tested for antibodies to hepatitis A virus were found to give a positive result. Of the arboviruses tested for, West Nile virus was usually predominant and was probably responsible for most of the arbovirus infections. Antibodies to the Sindbis, Chikungunya, Germiston and Rift Valley fever viruses were also found.
This is the introductory paper to a series on the ecology of arboviruses in Argentina. Epizootics of equine encephalitis have occurred since at least 1908, principally in the Pampa and Espinal biogeographic zones, with significant economic losses; human cases of encephalitis have been rare or absent. Both western equine and eastern equine encephalitis viruses have been isolated from horses during these epizootics, but the mosquitoes responsible for transmission have not been identified. A number of isolations of Venezuelan equine encephalitis (VEE) virus were reported between 1936 and 1958 in Argentina, but the validity of these findings has been seriously questioned. Nevertheless, serological evidence exists for human infections with a member of the VEE virus complex. Serological surveys conducted in the 1960s indicate a high prevalence of infection of humans and domestic animals with St. Louis encephalitis (SLE), and 2 SLE virus strains have been isolated from rodents. Human disease, however, has rarely been associated with SLE infection. Only 7 isolations of other arboviruses have been described (3 of Maguari, 1 of Aura, 2 of Una, and 1 of an untyped Bunyamwera group virus). In 1977, we began longitudinal field studies in Santa Fe Province, the epicenter of previous equine epizootics, and in 1980 we extended these studies to Chaco and Corrientes provinces. The study sites are described in this paper.
Complex studies carried out on the territory of Kazakhstan have allowed one to detect arboviruses, heretofore unknown in the republic, to determine their role in human infectious pathology and to obtain additional data on the ecology of viruses causing tick-borne encephalitis and Crimean hemorrhagic fever under the conditions of different geographical zones in the republic. On the basis of the results thus obtained the map indicating the spread of arbovirus infections and their causative agents on the territory of the Kazakh SSR has been drawn. This map may serve as a practical aid in organizing antiepidemic measures.
During the summer of 1993, mosquitoes were collected by dry ice-baited CDC light traps from July through September in 12 different cities in Iowa. In all, 169,907 mosquitoes belonging to 17 different species were collected. A total of 2,013 pools were processed for arbovirus isolation, from which 59 arbovirus isolates were obtained: 41 Flanders (FLA), 16 trivittatus (TVT), one Cache Valley (CV), and one Turlock (TUR). Supplementary sentinel chicken and human data are also included. In spite of the increase in larval habitats and elevated mosquito populations, there was not an increase in virus transmission.