Geographical distribution of arboviruses in Yugoslavia.

Studies of arboviruses started in Yugoslavia in 1953 following the isolation of TBE virus which caused a severe epidemic that year. Until now the following viruses have been proven to circulate in the country: tick-borne encephalitis (TBE), Crimean-Congo hemorrhagic fever (CCHF), Bhanja (BHA), sandfly fever (SF), Tahyna (TAH), Calovo (CVO), West Nile (WN), dengue (DEN), Jug Bogdanovac (JB), and Hantaviruses. TBE virus is endemic in the north-west part of the country, causing also epidemics in cyclical intervals. Its typical clinical picture is aseptic meningitis, but severe cases with paralysis have also been described. The bite of ticks is confirmed in about 80% of cases. CCF caused a small epidemic with ten clinical cases in Macedonia in 1976. Bhanja virus was isolated on the Dalmatian island of Brac in 1977, the antibody rate there, determined by the HI method, being about 31%. The first human disease in the world was caused by the Yugoslav Bhanja virus strain. Sandfly fever is still active in the country. The Naples type is prevailing and has proved hazardous for newcomers. Hantaviruses have been studied since 1980. They caused severe epidemics (1967, 1980, 1989) and sporadic cases all over the country. Three different strains are in circulation. Further studies are needed for the rest of the above mentioned viruses to learn more about their significance in human pathology.

Neutralizing antibodies for sandfly fever Naples virus in human sera on the island of Mljet.

Sera from apparently healthy residents of various age from different localities of the Adriatic island of Mljet were tested by the plaque reduction neutralization test (PRNT) for antibodies to sandfly fever Naples virus (SFN). An average of 51.4% of the sera examined was found to have neutralizing antibodies. Reactors to SFN virus were found in all the age groups examined and the antibody prevalence appeared to increase with age. The presence of SFN neutralizing antibodies in all age groups indicates that the virus must have been present endemically and that it is still active on the island of Mljet.

Incidence of hemagglutination-inhibiting antibodies for Bhanja virus in humans along the north-west border of Yugoslavia.

By the hemagglutination-inhibition test with the Yugoslav strain of Bhanja virus, the sera of 380 youngsters residing in the region along the Yugoslav-Hungarian border (North Croatia) and 367 sera from newcomers to the area from various parts of Yugoslavia were examined. The testing included 154 sera of the youngsters who had came to the region along the Yugoslav-Italian border (Slovenia) without antibodies for Bhanja virus and were staying there for a year. Hemagglutination-inhibiting antibodies for BHA virus were found in the sera of 5.53% examined natives of North Croatia, while in the newcomers after one-year stay in the area HI antibodies for the virus were confirmed in 3.27% of the sera examined. HI antibodies for BHA virus were found in 1.95% sera of the 154 youngsters who had come to the study area along the Yugoslav-Italian border (after one-year stay in the area). These results suggest a recent circulation of Bhanja virus in the regions studied. It is important to point out that the presence of the tick Haemaphysalis punctata, the principal vector of Bhanja virus in Europe, was evidenced in both regions.

Isolation of Bhanja virus from ticks in Yugoslavia.

Two strains of Bhanja (BHA) virus, an ungrouped arbovirus, were isolated from Haemaphysalis punctata ticks collected from sheep on the island of Brac in the Yugoslavian Adriatic. Serologic testing gave evidence of the endemicity of BHA virus on the island, and antibody prevalence rates were high for both man (35.8%--ranging locally to 61.3%) and sheep (100%). No antibody was found in 82 small mammals tested. Evidence of a natural cycle involving ticks and sheep, the potential significance of this virus for man and for animals of agricultural importance, and factors related to its epidemiology are discussed.

Serological studies on the epidemiology of sandfly fever in the Old World.

Selected human sera from 59 different localities in Africa, the Mediterranean littoral, eastern Europe and Asia were examined by plaque reduction neutralization test against eight sandfly (Phlebotomus) fever virus serotypes (Sicilian, Naples, Arumowot, SudAn 754-61, Karimabad, Salehabad, Gordil and Saint Floris) known to occur in the Old World. Results of these studies provide new information on the geographic distribution and prevalence of human infection with each of the viruses. Specific neutralizing antibodies were detected against all of the agents except Salehabad. Naples and Sicilian antibodies were encountered most frequently and had the widest geographic range; moreover they were found only in areas where Phlebotomus papatasi occurs. Age-specific antibody rates for several of the viruses are presented. These data and the epidemiology of sandfly fever are discussed.

Arbovirus infections in Ceylon.

The haemagglutination-inhibition test has been used to assess the frequency of arbovirus infections in the population of Ceylon, by age-group, and also in some animals. The antigens used were: chikungunya, JE, dengue 1, 2, 3, 4, and Tahyna.The percentage of positive reactors to the group-B viruses ranged from 16.3% to 84.6% and was lower in the mountainous part of the country. Infections with the chikungunya (group-A) virus were less frequent (from 0 to 37%) and were considered to be recent infections. The prevalence of antibodies was found to increase with age.From a comparison of the antibody titres of the indigenous Ceylonese population with those of a group of immigrant Yugoslav workers it was concluded that a titre of 1:640 would represent a significant titre for a recent infection.The animals examined included goats, cattle, bandicoots, pigs and sheep; virus infections were most frequent in the bandicoots, pigs and sheep.