Seroprevalencija i epidemiološke karakteristike krpeljskog encefalitisa u Vojvodini

Abstract

Uvod: Krpeljski encefalitis je prirodnožarišna vektorska bolest virusne etiologije, koja se javlja endemski na širokom području Evrope i Azije. Globalno, krpeljski encefalitis postaje sve veći javnozdravstveni problem, jer se postojeća endemska žarišta šire, a formiraju nova, što za posledicu ima postepen i stalan porast učestalosti ove bolesti u humanoj populaciji i pojavu autohtonih slučajeva u državama u kojima do sada nisu registrovani. U Republici Srbiji, epidemiološki nadzor nad krpeljskim encefalitisom je pasivan i insuficijentan, a laboratorijska dijagnostika je dostupna u malobrojnim ustanovama. Ciljevi istraživanja su bili da se dokaže prisustvo virusa krpeljskog encefalitisa i odredi njegov podtip i prevalencija u populaciji krpelja na teritoriji Fruške gore, te da se utvrde seroprevalencija specifičnih antitela protiv virusa krpeljskog encefalitisa stanovnika fruškogorske regije i stanovnika Vojvodine van teritorije Fruške gore, kao i stopa incidencije krpeljskog encefalitisa u Vojvodini. Materijal i metode: Utvrđivanje prisustva virusa krpeljskog encefalitisa i određivanje njegove prevalencije u populaciji krpelja sa teritorije Fruške gore sprovedeno je prospektivno. Krpelji su prikupljeni u periodu od juna 2019. godine do oktobra 2019. godine, tokom maja 2020. godine i u periodu mart-jun 2022. godine na 109 lokaliteta u 49 naseljenih mesta Fruške gore flag-čas metodom. Determinacija krpelja izvršena je na osnovu najvažnijih morfoloških karakteristika, prema taksonomskim ključevima. Krpelji su testirani na prisustvo virusne RNK primenom PCR metode. Utvrđivanje prisustva, učestalosti i rasprostranjenosti krpeljskog enceflitisa u populaciji ljudi u Vojvodini sprovedeno je prospektivno od 1. avgusta 2021. do 31. oktobra 2022. godine. Ispitanike su činili hospitalizovani pacijenti, kod kojih je na osnovu definicije slučaja Evropskog Centra za kontrolu i prevenciju bolesti postavljena sumnja na ovu bolest. Krvni serumi i/ili likvor ovih pacijenata ispitani su ELISA testom na prisustvo specifičnih antitela na virus krpeljskog encefalitisa. Svi seropozitivni i granični uzorci, dalje su ispitani neutralizacionim testom. Seroepidemiološko istraživanje sprovedeno je prospektivno. Na osnovu kriterijuma za uključivanje ispitanika u istraživanje, odnosno isljučivanje iz istaživanja, prikupljeno je 1000 uzoraka rezidualnog krvnog seruma stanovnika 49 naselja fruškogorske regije. Svakom ispitaniku ove grupe po polu i uzrastu odgovarao je po jedan iz grupe ispitanika, koju je činilo 1000 krvnih seruma stanovnika Vojvodine van teritorije Fruške gore. Laboratorijsko ispitivanje uzoraka krvnih seruma sprovedeno je ELISA testom na prisustvo specifičnih IgG antitela i svi pozitivni i granični uzorci su dalje ispitani na prisustvo neutrališućih antitela. Izračunata je seroprevalencija specifičnih antitela na virus krpeljskog encefalitisa u obe grupe ispitanika, te je izvršeno poređenje između njih, a analizirane su i seroprevalencije u odnosu na pol, uzrast, mesto stanovanja ispitanika, zanimanje i prethodni ubod krpelja. Rezultati: Tokom perioda istraživanja, prikupljena je i determinisana ukupno 1931 jedinka krpelja, od kojih je 1882 laboratorijski ispitano PCR metodom. Ni u jednom uzorku nije detektovana RNK virusa krpeljskog encefalitisa. U periodu od 1. avgusta 2021. do 31. oktobra 2022. godine, na teritoriji Vojvodine nisu registrovani potvrđeni slučajevi krpeljskog encefalitisa. Registrovana seroprevalencija antitela na virus krpeljskog encefalitisa u grupi stanovnika Vojvodine van Fruške gore iznosi 0,20% (95% CI: 0,02 - 0,72), a u grupi stanovnika fruškogorske regije 0,40% (95% CI: 0,01– 1,02). Seroprevalencija među stanovništvom Fruške gore dvostruko je viša od vrednosti seroprevalencije registrovane u grupi stanovnika Vojvodine van ove regije, ali nije utvrđena statistički značajna razlika u seroprevalencijama između ove dve grupe. Najviša seroprevalencija prema uzrastu od 2,94% (CI: 95% 0,07–16,39) beleži se u uzrasnoj grupi 80 i više godina u oba uzorka ispitanika. U grupi ispitanika Vojvodine van Fruške gore, seroprevalencije prema polu su u odnosu 1:1 (0,20% : 0,20% (95% CI: 0,01– 1,11)), dok su svi seropozitivni ispitanici na virus krpeljskog encefalitisa u grupi stanovnika Fruške gore muškog pola, a registrovana seroprevalencija iznosi 0,80% (95% CI: 0,20–2,05). Seropozitivni ispitanici registrovani su u naseljenim mestima: Beočin (1,08%; 95% CI: 0,02–5,99), Beška (1,45%; 95% CI: 0,03–8,07), Čortanovci (3,57%; 95% CI: 0,09–19,90), Irig (1,92%; 95% CI: 0,04– 10,71) i u delu Južnobačkog okruga van fruškogorske regije (0,65%; 95% CI: 0,07– 2,33). Zaključak: Stanovništvo regije Fruške gore i delova Južnobačkog okruga je prokuženije virusom krpeljskog encefalitisa, nego ostalo stanovništvo Vojvodine van ovih područja. Neophodna je implementacija sveobuhvatnog nadzora nad encefalitisima infektivne etiologije, na osnovu standardizovane definicije slučaja, posebno u sezoni najveće aktivnosti krpelja, uz jačanje laboratorijskih kapaciteta i uvođenje novih metoda laboratorijskog ispitivanja u rutinsku praksu. Takođe je neophodan skrining domaćih i divljih životinja i monitoring krpelja, uz ispitivanje prevalencije virusa u njima.

Introduction: Tick-borne encephalitis is a viral vector-borne disease with focal distribution, which occurs endemically in a wide area of Europe and Asia. Globally, tick-borne encephalitis is becoming an increasing public health problem, because existing endemic foci are spreading and new ones are emerging, which results in a gradual and constant increase in the incidence of this disease in human population and the appearance of autochthonous cases in countries where they have not been registered so far. In the Republic of Serbia, epidemiological surveillance of tick-borne encephalitis is passive and insufficient, and laboratory diagnostics are available in a small number of institutions. The aim of the research was to detect the presence of the tick-borne encephalitis virus and determine its subtype and prevalence in the tick population in the territory of Fruška Gora, and to determine the seroprevalence of specific antibodies against the tick-borne encephalitis virus among the population of the Fruška Gora region and population of Vojvodina outside the territory of Fruška Gora, as well as the incidence rate of tick-borne encephalitis in Vojvodina. Material and methods: Detecting the presence of the tick-borne encephalitis virus and determining its prevalence in ticks from the territory of Fruška Gora was conducted prospectively. Ticks were collected in the period from June 2019 to October 2019, during May 2020 and in the period March-June 2022 at 109 locations in 49 places of Fruška Gora using the flag-hour method. The determination of ticks was carried out according to the most important morphological characteristics, according to taxonomic keys. Ticks were tested for the presence of viral RNA using the PCR method. Determining the presence, frequency and prevalence of tick-borne encephalitis in the human population in Vojvodina was conducted prospectively from August 1, 2021 to October 31, 2022. The subjects were hospitalized patients, who were suspected for tick-borne encephalitis, based on the case definition of the European Center for Disease Control and Prevention. The blood sera and/or cerebrospinal fluid of these patients were examined by ELISA test for the presence of specific antibodies to the tick-borne encephalitis virus. All seropositive and borderline samples were further tested with a neutralization test. Seroepidemiological study was conducted prospectively. Based on the criteria for the inclusion of subjects in the research, that is, exclusion from the research, 1000 samples of residual blood serum of residents of 49 places in the Fruška Gora region were collected. Each subject of this group by gender and age was matched by one from the group of subjects, which consisted of 1000 blood sera of residents of Vojvodina outside the territory of Fruška Gora. Laboratory testing of blood serum samples was performed using an ELISA test for the presence of specific IgG antibodies, and all positive and borderline samples were further tested for the presence of neutralizing antibodies. The seroprevalence of specific antibodies against the tick-borne encephalitis virus was calculated in both groups of subjects, and they compared. Also, the seroprevalence was analyzed in relation to sex, age, place of residence of the subjects, occupation and previous tick bite. Results: During the research period, a total of 1931 ticks were collected and determined, of which 1882 were laboratory tested using the PCR method. No tick-borne encephalitis virus RNA was detected in any sample. In the period from August 1, 2021 to October 31, 2022, no confirmed cases of tick borne encephalitis were registered on the territory of Vojvodina. The registered seroprevalence of specific antibodies to the tick-borne encephalitis virus in the group of residents of Vojvodina outside Fruška Gora is 0.20% (95% CI: 0.02 - 0.72), and in the group of residents of the Fruška Gora region it is 0.40% (95% CI: 0.01–1.02). Seroprevalence among the population of Fruška Gora is twice as high as the value of seroprevalence registered in the group of inhabitants of Vojvodina outside this region, but no statistically significant difference in seroprevalence between these two groups was determined. The highest seroprevalence of 2.94% (CI: 95% 0.07–16.39) was recorded in the age group of 80 years and older in both samples of respondants. In the group of respondents from Vojvodina outside Fruška Gora, the male/female seroprevalence ratio is 1:1 (0.20% : 0.20% (95% CI: 0.01– 1.11)), while in the population of Fruška Gora, all seropositive respondents were males, and the registered seroprevalence is 0.80% (95% CI: 0.20–2.05). Seropositive respondents were registered in places: Beočin (1.08%; 95% CI: 0.02–5.99), Beška (1.45%; 95% CI: 0.03–8.07), Čortanovci (3.57%; 95% CI: 0.09–19.90), Irig (1.92%; 95% CI: 0.04–10.71) and in the part of South Bačka District outside the Fruška Gora region (0.65%; 95% CI: 0.07–2.33). Conclusion: The population of the region of Fruška Gora and parts of the South Bačka district were more infected with the tick-borne encephalitis virus than the rest of the population of Vojvodina outside these areas. It is necessary to implement a comprehensive surveillance of viral encephalitis, based on a standardized case definition, especially in the season of the highest tick activity, with the strengthening of laboratory capacities and the introduction of new methods of laboratory testing into routine practice. It is also necessary to carry out screening of domestic and wild animals and monitoring of ticks with an examination of the prevalence of the tick-borne encephalitis virus in them.