[Tick-borne meningoencephalitis in Gorski Kotar--new findings]. / Krpeljni meningoencefalitis u Gorskom kotaru--nove spoznaje.

Motivated by the occurrence of a case of suspected tick-borne meningoencephalitis (TBE) in a forestry worker of the Delnice Forestry Enterprise, 139 sera samples were collected from his co-workers, for TBE-specific IgG antibody testing. The commercially purchased ELISA and our own indirect immunofluorescence tests were used. Two sera samples were found positive and another six as inconclusive. All of them were sent for confirmation to the Institute of virology, University of Vienna. The two previously positive sera were also ELISA positive in Vienna, the rest being qualified as negative. Accepting that the first case really had TBE and that the two seropositives have experienced infection with the TBE virus, it is inferred that in the wider region of Delnice there is an until now unknown TBE focus, quiescent there for an unknown period of time.

Hepatitis A control in a refugee camp by active immunization.

An outbreak of hepatitis A occurred among children of a refugee camp in Croatia. In order to disrupt the outbreak, we decided to vaccinate children from 1 to 15 years of age in the camp, in addition to intensified general preventive measures. Assuming high prevalence of hepatitis A virus antibodies within this population, we conducted anti-HAV testing of the children eligible for vaccination. Of 108 children tested, 74 (68.5%) were anti-HAV positive. We vaccinated 34 children. One month after vaccination 31 previously negative children were tested for anti-HAV and 30 of them were found positive, suggesting a seroconversion rate of 96.8%. One child fell ill 5 days after vaccination, after whom no new cases of hepatitis A occurred. Thus we conclude that active immunization is a successful means of stopping an outbreak of hepatitis A.

Improvements for multipurpose bacteriological identification tables to suit the diagnosis of Vibrio cholerae.

The aim of the study was to reduce to key tests the 4 extensive polyvalent diagnostic biochemical tables most widely used in Croatia and to adapt them for the demonstration of Vibrio cholerae and its differentiation from the 3 Vibrios (V. alvinolyticus, V. mentschikovii, V. fluvialis) important in differential diagnosis. The fourth table has now been adapted to differentiate among all 12 Vibrio species known to be human pathogens (V. mimicus, V. cincinatiensis, V. holisae, V. damsela, V. furnisi, V. parahaemolyticus, V. vulnificus, V. carchariae). Using the inductive Learning by Logic Minimization Method (ILLM), we analyzed 2 tables (i.e. identification matrices) that were a part of bioMérieux's commercial packaged polyvalent identification systems widely used in Croatia (API 20E and ATB 32E), as well as 2 compilation tables by M. T. Kelly et al. The tables contained 27, 32, 59 and 8 tests, respectively. Cutting these solely to the key tests involved rationalizing them from 59 to the 5 necessary to differentiate Vibrio cholerae from 3 related Vibrios. Further rationalizations were from 32 to 2 and from 27 to the 3 necessary to differentiate Vibrio cholerae from 2 related Vibrios. By reducing the table of 8 tests to 7, and adding 4 new ones to these we achieved an optimization permitting mutual differentiation of all 12 known human Vibrio pathogens. Use of the selective TCBS plating medium was the only precondition for making these tables effective.

Some epidemiological data on TBE and Lyme borreliosis in Croatia.

TBE in Croatia was first discovered in 1953 but its mandatory reporting, as a distinct nosological entity, was instituted in 1987. Data presented here concern the 1989-1998 decade. During this period a total of 500 cases of TBE was recorded, ranging from 23 (1990) to 87 (1994) per year, with an average of 50 cases annually. There is only one natural focus in the northern part of the country, between the rivers Sava and Drava. Alleged cases of TBE, as occurring out of the focus (Zadar and Pula), have not been certified. The seasonal distribution of TBE cases is typical, most cases occurring from May to July (75%). As for the age distribution of TBE, a substantial rise is seen after the age of 20, only some 3% of cases occurring in children younger than 10 years. The first documented cases of human Lyme borreliosis in Croatia were published in 1986, its official compulsory reporting starting in 1991. Since then 1464 cases were recorded with an annual average of some 150 cases, varying from 93 (1992) up to 335 (1996). The age distribution is somewhat different from TBE, since the age group 0-9 years recruits 20% of all cases. Nevertheless, most of the diseased are of adult age. About 92% of the cases occur between May and August. The disease occurs mostly in the inland, above the 45th parallel, and only sporadically on the Adriatic coast.

A comparative study of reactogenicity and immunogenicity of an oral and an inactivated polio vaccine.

Reactogenicity and immunogenicity of the oral live attenuated (OPV) and inactivated polio vaccines (IPV) were studied in primary vaccination of toddlers. Three doses were administered simultaneously with DPT following the usual schedule valid in Croatia. The two groups of children had about 100 children each. Postvaccinal reactions were recorded for three days after each vaccination, and seroconversion was determined one month after the last injection. Although a conclusive analysis of postvaccinal reactions is not possible, since the staff of four different health centers apparently did not observe the same criteria, vaccination with IPV + DPT was not associated with remarkably more adverse events than OPV + DPT. Seroconversion rates attained with OPV ranged between 95.2% and 99.0%. With IPV, the rates were between 96.5% and 100%. Antibody levels for virus types 1, 2, and 3, as measured by GMT (reciprocal value), were 277, 1017, and 222 for OPV, and 465, 526, and 758 for IPV, respectively. IPV appears to be perfectly acceptable as a substitute for OPV for primary vaccination.

Immunity of the Croatian population to poliomyelitis--a serosurvey.

Eight years after the last case of poliomyelitis it was of a special interest to determine the immunity level of the Croatian population to polio and thus to evaluate the possible risk of the revival of this infection. For this purpose, 200 sera samples were collected from individuals of different age and place of residence. Neutralizing antibodies (NT) for all three polioviruses were searched for. Antibody titers of > or = 1:8 were considered positive. Results of the study showed some 75% of the study subjects to have antibodies to polio type 1 and 2, and some 83% to type 3. Only 4% of the sera tested had no NT antibodies to any of the three types. The lowest mean geometric antibody titer (GMT) was for polio type 3 (GMT3 = 19.4; reciprocal value) and somewhat higher for type 1 (GMT1 = 23.5) and type 2 (GMT2 = 22.6). When the antibody titers were related with the age of the subjects, they were found not to decline with age, which was ascribed to periodical boosters with vaccinal strains. It is stressed that, in spite of the eradication of poliomyelitis achieved in Croatia, compulsory vaccination of the children should be continued until its global eradication.

[Immunity to diphtheria in the Croatian population in 1994]. / Imunost Hrvatskog pucanstva na difteriju 1994. godine.

The large outbreak of diphtheria in the former SSSR countries, which has been linked, among others, to low herd immunity, has led us to determine the level of this immunity in the Croatian population in view to undertake, if necessary, extra prophylactic measures (vaccination). For the purpose, C. diphtheriae serum antibody levels were determined in persons aged from 20 to above 60 years and coming from four major Croatian towns (Zagreb, Rijeka, Osijek and Split). A commercial ELISA test and neutralization test (NT) on guinea pig were used. Whereas 223 sera were examined with ELISA, only 51 underwent NT. Both tests showed herd immunity to decline gradually with age, ELISA also revealing a wide variation range of antibody concentrations by individual age groups (Table 1). There was not a single serum sample below the "critical" level of 0.01 IU/ml. in Table 2, ELISA results are classified in three groups by antibody level: up to 0.01 IU/ml, between 0.01 and 0.09 and above 0.09 IU/ml, i.e. as unprotected, partially protected and protected persons. Such grouping of findings shows that not one of the subjects belongs to the first category, that most of them belong to the third (68%), as well as that the latter are passing into the second with growing age. It is concluded that by carrying out the mandatory immunization programme, in force in Croatia, it has been possible to attain and to sustain a high level of herd immunity. Hence there is no need for booster immunizations at older age.

[Reactivity and immunogenicity of Havrix 360 vaccine for hepatitis A]. / Reaktogenost i imunogenost "Havrix 360" vakcine protiv hepatitisa A.

The reactogenicity and immunogenicity of a new vaccine against viral hepatitis A, under the name HAVRIX, manufactured by SmithKline Beecham Biologicals, Belgium, was studied. A single dose of 1 ml contains not less than 360 ELISA units of inactivated HAV, strain HM175, cultivated on human diploid cells. The vaccine has been applied intramuscularly to 80 second-grade primary school children under the 0, 1 and 6-month schedule. Postvaccinal reactions were followed for three days after each application of the vaccine. They were generally mild and present in less than 5% of the vaccinees (local as well as general). One month after the last vaccination the seroconversion was 100% in the anti HAV antibody test (HAVAB-ABBOT), the antibody level being over 500 IU/I, in 98% of the vaccinees. In conclusion, the tested vaccine is perfectly acceptable from both aspects, postvaccinal reactions and conferred protection. As the hepatitis A morbidity in Croatia has never been as low as in the last few years, the eventual introduction of this vaccination into the EPI is questionable.

Schizophrenia and prenatal exposure to the 1957 A2 influenza epidemic in Croatia.

The authors present data from the Republic of Croatia on schizophrenia rates in a birth cohort prenatally exposed to the 1957 A2 influenza epidemic and in comparison (unexposed) birth cohorts. The rate of schizophrenia did not differ significantly between the exposed and unexposed cohorts.

[Hemorrhagic fever with renal syndrome in Croatia: incidence of infection in human and wild animal reservoirs]. / Hemoragijska groznica s bubreznim sindromom (HGBS) u Hrvatskoj: ucestalost infekcije u ljudi i divlji animalni rezervoari.

On the territory of Lika and Gorski Kotar a group of 300 forest workers and 260 persons from the general population were screened for Hantavirus antibodies (by the indirect immunofluorescence test). In the first group of examenees a mean of 1.6% were found positive, ranging from 0% (Gospic) to 3.2% (Ogulin). In the second groups a mean of 5.4% were positive, ranging from 4.4 to 8.9% (Delnice and Slunj, respectively). It is concluded that the Hantavirus infection rate in our natural foci of HFRS is higher than officially registered. Screening of micromammals for the presence of Hantavirus in their organs (lungs), using the direct immunofluorescence test, was undertaken on three locations: Planina Gornja (hillsides of the mountain Medvednica), a case of HFRS having been registered there previously, and Plitvicka Jezera and Velika Gorica (village of Kobilic) selected because of two previous epidemics of HFRS (1967 and 1989, respectively). On the first location, all 126 animals examined (10 different species) were Hantavirus negative. On the second location, 9 of the 165 animals examined (three species) were Hantavirus positive (5.4%), namely 6 bank voles (Clethrionomys glareolus) and three yellow-necked mice (Apodemus flavicollis). On the third location, where 141 animals was caught and examined (7 different species), 7 animals were positive (4.9%): 3 striped field mice (A. agrarius), 3 wood mice (A. sylvaticus) and 1 bank vole (Cl. glareolus). The findings suggest that in our natural foci of HFRS the circulation of the Hantavirus is sustained by several species of micromammals.

Persistence of immunity against measles in persons immunized with Edmonston-Zagreb vaccine.

Cohorts of 30 children--470 in all--vaccinated against measles 2 to 17 years earlier were tested for measles heminhibiting antibodies. The vaccinees were randomly selected from a semi-urban, semi-rural population where the circulation of the wild measles virus has never been interrupted. The vaccinal status of the vaccinees varied widely, some were vaccinated only once, some twice or even three times, in some the primary vaccination was performed with a measles monovalent and in some with a combined MMR vaccine, only the revaccination having always been performed with a monovalent vaccine. The results of this serologic study reveal that the vaccine-induced immunity against measles does not fade with time, on the contrary, as judged by the mean geometric antibody titers, it rises. This is speculatively attributed to the booster effect of natural reinfection(s). Thereafter it is demonstrated that revaccination(s) do not yield a better immunity than the primary vaccination alone. This "revaccination", if withheld, helps only to attain a better coverage of children that have escaped primary vaccination.

[Epidemiology of enteroviral meningitis in Croatia 1958-1988 with special emphasis on the great epidemic of 1988]. / Epidemiologija enterovirusnih meningitisa u Republici Hrvatskoj 1958-1988. s posebnim osvrtom na veliku epidemiju 1988. godine.

In 1988, there was a large outbreak of enteroviral meningitis in the Republic of Croatia and in other parts of Yugoslavia as well. A total of 4079 cases of enteroviral meningitis were registered with one fatal outcome (Mb 8.7 0/ooo). The outbreak was caused by echovirus 4. Analysis of epidemiological, virologic and ecological data for 1988, as well as for a number of previous years, showed the following: an upward morbidity trend observed from 1958 to 1979 turned to a high level stationary trend with irregular annual oscillations. A cyclic morbidity trend was noticed with peaks in 9-10 years. Seasonal peak was lower in July regularly. In 1988, age and sex distribution of the diseased persons differed from the usual picture, showing greater proportion of older age and women. The probable reason is in the long absence of echovirus 4 from the target population, resulting in low herd immunity. This caused greater proportion of older cases, among which women (mothers) had probably been more exposed to infections than men (nursing ill household members, laundry handling, etc). The epidemic years 1988 and 1979 were hot during spring and summer, at above-average level. Such climatic factors (high temperature) coupled with the sufficiently low level of herd immunity probably triggered in both examples the outbreak of enteroviral meningitis.

[The role of large wildlife in the maintenance of natural foci of tick-borne meningoencephalitis in northern Croatia]. / Uloga velikih divljih zivotinja u podrzavanju prirodnog zarista krpeljnog meningoencefalitisa u Sjevernoj Hrvatskoj.

Between 1986-1988 sera from 245 game animals--37 roe deers, 102 red deers, 81 wild boars and 25 hares--shot in 8 different localities of Nort Croatia, a well-known nosoareal of tick-borne encephalitis, were tested for TBE virus heminhibiting antibodies. The following percentages of positive animals were found: 24, 39, 39 and 0% respectively. Most of the animals examined, 180 of them, were shot in lowland woods of the commune of Nasice and its surroundings. There the percentage of positive animals was somewhat higher: 36, 41, 42 and 0 respectively. As these animals regularly participate in the feeding cycle of the ubiquitous wood tick Ixodes ricinus, the main vector of the tick-borne meningoencephalitis virus, it is infered that they (the hare being excluded in this study), apart from myomorphous mammals, play an important role in the transmission chain of the tick-borne meningoencephalitis virus in the respective natural foci of this zoonosis.

[The development and duration of immunity in children vaccinated against measles with the Edmonston-Zagreb vaccine]. / Stvaranje i trajanje imunosti u djece cijepljene protiv ospica vakcinom Edmonston-Zagreb.

After routine measles-rubella-mumps (MRM) vaccine, seroconversion rate for measles heminhibiting (HI) antibodies in a group of 161 children was determined. Of the 154 children who had no HI antibodies in the first serum sample, 153 (99.3%) developed these antibodies in titres greater than or equal to 1:4 and 148 (96.1%) in titres greater than or equal to 1:8 at 6 weeks postvaccination. These results are in concord with the WHO standards. Another study was designed to evaluate persistence of HI antibodies to measles in a group of 123 children who were given MRM vaccine 1-6 years earlier. No significant decrease in HI antibody titers was recorded. It is concluded that immunity acquired through vaccination with the Edmonston-Zagreb measles virus strain in children aged 12 months to 3 years is satisfactory and that it does not decrease at least up to 6 years following vaccination.

[An epidemic of legionnaires' disease in a hotel]. / Epidemija legionarske bolest u jednom hotelu.

An outbreak of legionnaires' disease and epidemic control measures taken at one of our hotels are described. Twenty (1% morbidity) hotel guests were affected with one dying. As a result of field investigations and survey the hot water supply system has been identified as the source of infection. Control measures which created conditions unfavourable to Legionella growth and replication in the hot water system stopped the outbreak.

[Reactivity and immunogenicity of Engerix B, the recombinant DNA vaccine against hepatitis B]. / Ispitivanje reaktogenosti i imunogenosti rekombinantne DNA vakcine protiv hepatitisa B "Engerix-B".

A group of 67 health workers with no markers indicating previous hepatitis B infection were vaccinated against hepatitis B with a new DNA recombinant vaccine, Engerix B (commercially manufactured by Smith-Kline-RIT, Belgium). Three injections were given according to the 0-1-6 schedule. One month after the last injection the vaccinees were tested for anti-HBs antibodies by the enzyme-linked assay. Antibody titers equal or less than 10 mIU/ml were found only in three subjects or in 4.5% of them. Titers ranging from 11 to 99 mIU/ml were found in 7 subjects (10.4%), from 100 to 999 mIU/ml in 28 (41.8%) and those equal or more than 1000 mIU/ml in 29 subjects (43.3%). It is inferred that the seroconversion rate is 95.5%. Only one subject did not develop detectable antibodies but three subjects had titers over 10000 mIU/ml. No one developed overt hepatitis B during the trial nor did the high responders experienced inapparent infections. They were tested for anti HBc with negative results. Postvaccinal reactions were mild and almost exclusively local. There were no complications. For its high immunogenicity and acceptable reactogenicity the Engerix B vaccine has a promising future.