TBE in Croatia

Wilhelm Erber and Tamara Vuković-Janković

E-CDC risk status: endemic

(data as of end 2022)

History and current situation

Even though tick-borne encephalitis (TBE) has been a notifiable disease in Croatia since 2007, there are no or only limited data available on the occurring tick species in the endemic areas, on the prevalence of TBE virus (TBEV) in ticks, its distribution in Croatia, and its genetic characteristics. Reporting of human cases also is very scarce. The Central European subtype of virus (TBEV-EU) appears to be present in Croatia.

Natural foci of TBE have been found so far in the continental area in the northwestern region (between the Sava River and the Drava River, near Zagreb, Varaždin, Bjelovar, Koprivnica, Križevci, and Vinkovci – with an area around Slavonski Brod) and in the northeastern region (across a small area on the western outskirts of Osijek city). Recently, 2 new natural foci have emerged in the central mountainous region, south of the Sava River. Cases are reported only sporadically in the Adriatic coastal region.1

A recent study found a prevalence of TBEV similar to other European countries (0.1%–5%) in ticks removed from red foxes in Varazdin County and Zagreb County (in the vicinity of Medvednica mountain), both well known as TBE areas. Furthermore, a viral prevalence of 1.1% (95% CI: 0.3%–3.0%) has been found in red deer (Cervus elaphus) from 2 areas in northeastern Croatia (Vukovar-Srijem County and Osijek-Baranja County). The latest human TBE cases from these 2 counties were recorded in 2009 (1 case) and 2010 (1 case), respectively.2

An average of 20 human cases of TBE is reported each year (minimum 11, maximum 45)3,4 i.e., 0.26–1.05 cases/100,000 persons. The majority of cases were registered in the Koprivnica-Križevci County (average annual incidence 5.2/100,000), Međimurska County (5/100,000), and Bjelovar-Bilogora County (4.3/100,000). The average incidence rate in the city of Zagreb, within the observed period, was 0.2/100,000 (16 cases registered). In 2015, the first outbreak of TBE after consumption of raw goat milk was reported in 7 out of 10 exposed persons.5


Figure 1: Geographical distribution of TBE by counties of the Republic of Croatia (1999–2008)3

Click the image above to enlarge

Overview of TBE in Croatia

Table 1: Virus, vector, transmission of TBE in Croatia
Viral subtypes, distribution European subtype (TBEV-EU)2,3
Reservoir animals Rodents
Infected tick species (%) Information not available
Dairy product transmission In 2015 a small outbreak of TBE affecting 7 people from the region of Bjelovar after consuming fresh goat’s milk and cheeses.5 In 2019, 5 patients were reported to have consumed raw goat milk from the same farm in the Gorski Kotar region.6

Table 2: TBE-reporting and vaccine prevention in Croatia
Mandatory TBE reporting TBE has been an obligatory reportable disease in Croatia since 20071
Other TBE-surveillance Not applicable
Special clinical features Information not available
Available vaccines FSME IMMUN7
Vaccination recommendations and reimbursement Only recommended for residents in endemic areas and those visiting endemic areas (for recreation), as well as forestry workers in the Koprivnica-Križevci region1
Vaccine uptake by age group/ risk group/ general population Year / Number of vaccinated individuals in Zagreb8

2010 / 670

2011 / 678

2012 / 781

2013 / 577

2014 / 415

Name, address/website of TBE National Reference Center National Institute of Public Health of Croatia

https://www.hzjz.hr/en/


Figure 2: Burden of TBE in Croatia over time8-9

Click the image above to enlarge

Source data
YearNumber of Cases Incidence / 105
1991601.4
1992270.6
1993761.8
1994872.1
1995591.4
1996571.4
1997250.6
1998240.6
1999260.6
2000180.4
2001270.6
2002300.7
2003360.9
2004380.9
2005280.7
2006200.5
2007110.3
2008200.5
2009441.1
2010360.9
2011260.6
2012451.1
2013441.1
2014220.5
2015250.6
201660.1
2017100.2
2018240.6
2019140.3
2020150.4
202140.1
2022230.6

Age and gender distribution of TBE in Croatia

No available data

Acknowledgments

2021 and 2022 TBE case numbers were kindly provided by Assoc. Prof. Rok Čivljak, University of Zagreb School of Medicine, Dr. Fran Mihaljević University Hospital for Infectious Diseases, Zagreb, Croatia.

Contact:

wilhelm.erber@pfizer.com

Citation:

Erber W, Vuković-Janković T. TBE in Croatia. Chapter 12b. In: Dobler G, Erber W, Bröker M, Schmitt HJ, eds. The TBE Book. 6th ed. Singapore: Global Health Press;2023. doi:10.33442/26613980_12b7-6

References

  1. Zavadska D, et al. Recommendations for tick-borne encephalitis vaccination from the Central European Vaccination Awareness Group (CEVAG). Hum Vaccin Immunother. 2013;9(2):362-74.
  2. Jemersic L, et al. Detection and genetic characterization of tick-borne encephalitis virus (TBEV) derived from ticks removed from red foxes (Vulpes vulpes) and isolated from spleen samples of red deer (Cervus elaphus) in Croatia. Ticks Tick Borne Dis. 2014;5(1):7-13.
  3. Mulic R, et al. Tick-borne diseases in the Republic of Croatia. Lijec Vjesn. 2011;133(3-4):89-95.
  4. Suss J. Tick-borne encephalitis 2010: epidemiology, risk areas, and virus strains in Europe and Asia-an overview. Ticks Tick-Borne Dis. 2011;2(1):2-15.
  5. Markovinovic L, et al. An outbreak of tick-borne encephalitis associated with raw goat milk and cheese consumption, Croatia, 2015. Infection. 2016;44:661–5.
  6. Vilibic-Cavlek T, et al. Emerging and Neglected Viruses of Zoonotic Importance in Croatia. Pathogens. 2021; 10(1):73. https://doi.org/10.3390/pathogens10010073
  7. Agency for Medicines and Medical Devices of Croatia. Database available at: http://www.halmed.hr/Lijekovi/Baza-lijekova/#rezultati [Accessed July 2017]
  8. Dr. Andrija Štampar Teaching Institute of Public Health. Data available at: http://www.stampar.hr/en [Accessed June, 2017]
  9. Amicizia D, et al. Epidemiology of tick-borne encephalitis (TBE) in Europe and its prevention by available vaccines. Hum Vaccin Immunother. 2013;9(5):1163–71.

TBE Book