Raccoon dog rabies surveillance and post-vaccination monitoring in Lithuania 2006 to 2010

<p>Abstract</p> <p>Background</p> <p>Oral rabies vaccination (ORV) in rabies infected regions should target the primary rabies vector species, which in Lithuania includes raccoon dogs as well as red foxes. Specific investigations on ORV in raccoon dogs are needed e.g. evaluation of vaccine effectiveness under field conditions. The objective of the current study was to investigate the efficacy of the ORV programme 2006-2010 in Lithuania by examining the number of rabies cases and estimating the prevalences of a tetracycline biomarker (TTC) and rabies virus antibodies in raccoon dogs.</p> <p>Methods</p> <p>From 2006 to 2010, 12.5 million rabies vaccine-baits were distributed by aircraft. Baiting occurred twice per year (spring and autumn), targeting raccoon dogs and red foxes in a 63,000 km²area of Lithuania. The mandibles of raccoon dogs found dead or killed in the vaccination area were analyzed by fluorescence microscopy for the presence of the TTC. Rabies virus sera neutralizing anti-glycoprotein antibody titres were determined using an indirect ELISA method and seroconversion (> 0.5 EU/ml) rates were estimated.</p> <p>Results</p> <p>During the study period, 51.5% of raccoon dog mandibles were positive for TTC. 1688 of 3260 tested adults and 69 of 175 tested cubs were TTC positive. Forty-seven percent of raccoon dog serum samples were positive for rabies virus antibodies. 302 of 621 investigated adults and 33 of 95 investigated cubs were seropositive. In the same time 302 of 684 and 43 of 124 tested samples were TTC and ELISA positive in spring; whereas 1455 of 2751 and 292 of 592 tested samples were TTC and ELISA positive in autumn. There was a positive correlation between the number of TTC and antibody positive animals for both adult and cub groups.</p> <p>Conclusions</p> <p>ORV was effective in reducing the prevalence of rabies in the raccoon dog population in Lithuania. The prevalence of rabies cases in raccoon dogs in Lithuania decreased from 60.7% in 2006-2007 to 6.5% in 2009-2010.</p

Filogenetsko istraživanje djelomičnih sekvencija gena G terenskih izolata virusa bjesnoće u Litvi.

The objective of this study was to evaluate the molecular epidemiology of rabies virus G-gene partial sequences in rabies positive field samples, isolated in different regions of Lithuania, and to compare the sequences phylogenetically with various rabies virus isolates of wild carnivores from the Baltic Sea region, Europe and Russia. Twenty brain samples of rabid animals, collected during the period 2006-2011, were investigated. Multiple alignments of 358 nt G gene (nt 3324-3682) sequences were performed using ClustalW with default settings. Phylogenetic and molecular evolutionary analyses were conducted using the Neighbor-Joining method (NJ) in MEGA version 4. The phylogenetic investigations of rabies virus glycoprotein indicate that the Lithuanian rabies virus isolates’ G-sequences were closely related and showed 89.8-98.9 % of nt identity. The G-sequences between Lithuanian raccoon dog and red fox rabies virus isolates were more conservative (97.2 % nt identity) than the rabies virus isolates inside the raccoon dog group (95.1 % nt identity). Two Lithuanian raccoon dog rabies virus isolate G-sequences were rather divergent (90.8 and 91.2 % nt identity) and were closely associated with rabies virus isolate G-sequences from Estonia (92.5 % nt identity), Russia (91.0 %) and Poland (89.3 %) respectively. The comparative investigation of G-sequences between the Lithuanian rabies virus isolates and different isolates from Germany, Slovenia and France indicated 84.2 % nt identity, whereas the G-sequences of Lithuanian rabies virus isolates and rabies virus isolate G-sequences from Russia were 88.1 % nt identical.Svrha ovog rada bila je odrediti molekularnu epidemiologiju djelomičnih sekvencija gena G virusa bjesnoće u terenskim uzorcima pozitivnima na bjesnoću iz različitih područja Litve te ih filogenetski usporediti s različitim izolatima virusa bjesnoće iz divljih mesojeda na području Baltičkog jezera, Europe i Rusije. Pretraženo je 20 uzoraka tkiva mozga bijesnih životinja prikupljenih u razdoblju od 2006. do 2011. Višestruka poravnanja sekvencija od 358 nukleotida gena G (nt 3324-3682) učinjena su pomoću programa ClustalW. Filogenetska i molekularno evolucijska analiza provedena je metodom združivanja genetski najsličnijih sojeva (engl. Neighbour-joining method) u MEGA verziji 4. Filogenetska istraživanja glikoproteina virusa naznačuju da su G-sekvencije izolata litavskoga virusa bjesnoće usko srodne i pokazuju 89,8-98,9 % nt identičnosti. G-sekvencije izolata virusa bjesnoće iz litavskog rakunskog psa i crvenih lisica bile su sačuvanije (97,2 % nt identičnosti) nego izolati virusa bjesnoće izdvojeni iz rakunskog psa (95,1 % nt identičnosti). G-sekvencije dvaju izolata iz litavskih rakunskih pasa bile su prilično divergentne (90,8 i 91,2 % nt identičnosti) i usko srodne s G-sekvencijama izolata virusa bjesnoće iz Estonije (92,5 % nt identičnosti), Rusije (91,0 %) i Poljske (89,3 %). Komparativno istraživanje G-sekvencije litavskih izolata virusa bjesnoće i različitih izolata iz Njemačke, Slovenije i Francuske pokazalo je 84,2 % nt identičnosti, dok je identičnost između G-sekvencije između litavskih izolata virusa bjesnoće i ruskih izolata bila na razini 88,1 % nt identičnosti

African swine fever situation and detection methods in Lithuania

African swine fever is one of the most important and serious diseases of wild boar and domestic pigs. Its highly contagious nature and ability to spread over long distances make it one of the most feared diseases, since its devastating effects on pig production have been experienced not only in most of sub-Saharan Africa but also in Western Europe, the Caribbean, Brazil and, most recently, the Caucasus. On 24 th January 2014 Lithuania notified two primary cases of African swine fever (ASF) in wild boar. The animals were tested positive for ASF virus (ASFV) genome by real time PCR at the National Reference Laboratory for ASF in Lithuania (NRL), results were confirmed by the EURL CISA-INIA. Intensive wild and domestic animal monitoring program was started. During period 2014-2017 ASF were confirmed in two large commercial pig holding with the highest biosecurity. Pigs were killed and destroyed. Since 2014 ASF outbreak territory from east and south has expanded to the middle of Lithuania. As there is still no vaccine or treatment available, monitoring and controling of the disease is the only way to control the disease. Diagnosis by PCR is one of the highly recommended diagnostic methods by OIE for diagnosis of ASF. This studies was to combine singleplex real-time PCR assays to a duplex assay allowing the identification of ASF and internal control in a single PCR tube and to compare primers target the p72 gene (ASF 250 bp and ASF 75 bp) efectivity. Multiplex real-time PCR assays offer the possibility to save analysis time and costs and have therefore a high potential to be applied in routine analysis. For experiments were used reference sample (INIA, Spain), and positive samples from affected places in Lithuania. Results show 100% sensitivity and specificityBiologijos katedraGamtos mokslų fakultetasNacionalinis maisto ir veterinarijos rizikos vertinimo institutasVytauto Didžiojo universiteta

Skirtingų Afrikinio kiaulių maro viruso nustatymo metodų įvertinimas

Afrikinio kiaulių maro (AKM) suvaldymui iki šiol nėra jokios vakcinos ar gydymo, todėl ligos stebėjimas ir ankstyva diagnostika yra vienintelis būdas ją kontroliuoti. Labai svarbu yra įdiegti naujus ir greitus molekulinius AKM diagnozavimo metodus, pasižyminčius dideliu jautrumu ir specifiškumu. Šio tyrimo tikslas buvo parinkus tinkamus reakcijos pradmenis ir zondus, reakcijos buferius ir pradme-nų prilydimo temperatūrą, optimizuoti daugybinės realaus laiko PGR metodą, kuriuo galima aptiktiAKM virusą ir užtikrinti vidinę kontrolę, bei palyginti AKM viengubos (250 bp AKM fragmentas) ir AKM-IC daugybinės (75 bp AKM fragmentas) realaus laiko PGR metodus. Buvo patvirtintas daugybinės realaus laiko PGR metodo specifiškumas ir jautrumas. Gauti rezultatai rodo, kad AKM-IC daugybinės realaus laiko PGR metodas yra greitesnis ir jautresnis nei realaus laiko PGR (juo nustatomas tik 250 bp AKM fragmentas) nustatant AKM virusą naminių kiaulių ir šernų kaulų čiulpų, širdies, inkstų, kepenų, blužnies, plaučių, maisto produktų ir kt. mėginiuose. Po tyrimų Ct vertės pagal šiuos metodus skyrėsi per 0,55–8,4 ciklo, tai reiškia, kad daugybinės realaus laiko PGR metodu sintetinama 0,3–70,5 karto daugiau reakcijos produktoAfrican swine fever (ASF) is a contagious disease of key importance that occurs in wild boar population and domestic pigs. To date, there is no vaccine or treatment available, hence disease surveillance and stamping out in case of an outbreak is the only way to control it. A duplex ASF-IC real-time PCR assay was optimised using field samples obtained in Lithuania and results of singleplex and duplex real-time PCR assays allowing the identification of the ASF virus were compared. The specificity and sensitivity of ASF virus detection was validated using a reference sample of positive and negative virus nucleic acid and ASF virus positive and negative samples obtained from animals in Lithuania. Results prove that duplex ASF-IC real-time PCR assay provides a rapid, sensitive, and reliable molecular tool for ASF virus detection in wild boar population and domestic pigs. In general, it was found that duplex ASF-IC real-time PCR assay proves to be faster and more sensitive than singleplex real-time PCR and therefore has a high potential to be applied in routine analysisBiologijos katedraGamtos mokslų fakultetasMatematikos ir statistikos katedraNacionalinis maisto ir veterinarijos rizikos vertinimo institutasVytauto Didžiojo universiteta

African Swine Fever and Its Epidemiological Course in Lithuanian Wild Boar

African swine fever (ASF) has been present in Lithuania since 2014. It is mainly the wild boar population that is affected. Currently, little is known about the epidemiological course of ASF in Lithuania. In the present study, ASF surveillance data from 2016–2021 were analyzed. The numbers of samples taken from hunted wild boar and wild boar found dead per year and month were recorded and the prevalence was estimated for each study month and administrative unit. A Bayesian space–time model was used to calculate the temporal trend of the prevalence estimates. In addition, population data were analyzed on a yearly basis. Most samples were investigated in 2016 and 2017 and originated from hunted animals. Prevalence estimates of ASF virus-positive wild boar decreased from May 2019 onwards. Seroprevalence estimates showed a slight decrease at the same time, but they increased again at the end of the study period. A significant decrease in the population density was observed over time. The results of the study show that ASF is still present in the Lithuanian wild boar population. A joint interdisciplinary effort is needed to identify weaknesses in the control of ASF in Lithuania and to combat the disease more successfully

The African Swine Fever epidemic in wild boar (Sus scrofa) in Lithuania (2014–2018)

In January 2014 the first case of African swine fever (ASF) in wild boar of the Baltic States was reported from Lithuania. It has been the first occurrence of the disease in Eastern EU member states. Since then, the disease spread further affecting not only the Baltic States and Poland but also south-eastern Europe, the Czech Republic and Belgium. The spreading pattern of ASF with its long-distance spread of several hundreds of kilometers on the one hand and the endemic situation in wild boar on the other is far from being understood. By analyzing data of ASF cases in wild boar along with implemented control measures in Lithuania from 2014–2018 this study aims to contribute to a better understanding of the disease. In brief, despite huge efforts to eradicate ASF, the disease is now endemic in the Lithuanian wild boar population. About 86% of Lithuanian’s territory is affected and over 3225 ASF cases in wild boar have been notified since 2014. The ASF epidemic led to a considerable decline in wild boar hunting bags. Intensified hunting might have reduced the wild boar population but this effect cannot be differentiated from the population decline caused by the disease itself. However, for ASF detection sampling of wild boar found dead supported by financial incentives turned out to be one of the most effective tools

Prevalence and spatiotemporal distribution of African swine fever in Lithuania, 2014–2017

Abstract Background The emergence in 2014 and persistence of African Swine Fever (ASF) in Lithuania has been linked to infected wild boar movement and close contact with the carcasses of other infected wild boars. Over time the number of reported cases of ASF in wild boars gradually increased, but no detailed epidemiological data has been available. Therefore, the objective of the present study was to determine ASF virus prevalence in wild boars and domestic pigs during the 2014–2017 period and further explore the current geographical distribution of the virus. Results Our study results show that ASF virus prevalence in hunted wild boars using PCR analysis increased from 0.83% (95% CI 0.69–0.98) to 2.27% (95% CI 2.05–2.48) from 2014 to 2016 respectively. However, there was a dramatic jump in the number of ASF positive wild boars cases in 2017 resulting in prevalence of 12.39% (95% CI 11.91–12.86) (p < 0.05). The average prevalence of ASF-specific antibodies in wild boar population during years 2014–2017 was 0.45% (95% CI 0.39–0.51) based on ELISA test results. Prevalence of ASF virus in domestic pigs ranged from 0.24% (95% CI 0.17% - 0.32) in 2015 to 2.74% (95% CI 2.33% - 3.15) in 2017. The average seasonal prevalence of ASF virus in pigs was statistically significant (p < 0.05) and ranged from 0% in spring to 3.68% (95% CI 3.32–4.05) in summer. Correlation between the pig density and number of recorded pig ASF cases in affected regions was only found in 2017 (R = 0.78, p < 0.05). No correlation was detected between the wild boar density and number of recorded pig or wild boar ASF - positive cases. Conclusions This study provides the first results of ASF virus prevalence changes in Lithuania during the 2014–2017. The overall results confirm the relatively high prevalence of ASF virus in wild boar that was gradually increasing from 2014 to 2017. In the last year of study, the number of ASF positive cases in both domestic pigs and wild boars had unexpectedly increased several times. A better understanding of current status of the disease will enable better control and prevent further spread of ASF virus in Western Europe

Rabies in the Baltic States: Decoding a Process of Control and Elimination

<div><p>Rabies is a fatal zoonosis that still causes nearly 70, 000 human deaths every year. In Europe, the oral rabies vaccination (ORV) of red foxes (<i>Vulpes vulpes</i>) was developed in the late 1970s and has demonstrated its effectiveness in the eradication of the disease in Western and some Central European countries. Following the accession of the three Baltic countries—Estonia, Latvia and Lithuania—to the European Union in 2004, subsequent financial support has allowed the implementation of regular ORV campaigns since 2005–2006. This paper reviews ten years of surveillance efforts and ORV campaigns in these countries resulting in the near eradication of the disease. The various factors that may have influenced the results of vaccination monitoring were assessed using generalized linear models (GLMs) on bait uptake and on herd immunity. As shown in previous studies, juveniles had lower bait uptake level than adults. For the first time, raccoon dogs (<i>Nyctereutes procyonoides)</i> were shown to have significantly lower bait uptake proportion compared with red foxes. This result suggests potentially altered ORV effectiveness in this invasive species compared to the red foxes. An extensive phylogenetic analysis demonstrated that the North-East European (NEE) rabies phylogroup is endemic in all three Baltic countries. Although successive oral vaccination campaigns have substantially reduced the number of detected rabies cases, sporadic detection of the C lineage (European part of Russian phylogroup) underlines the risk of reintroduction via westward spread from bordering countries. Vaccine induced cases were also reported for the first time in non-target species (<i>Martes martes</i> and <i>Meles meles</i>).</p></div

Location of the study and evolution of ORV areas.

<p>*Latvia: 2008 and autumn 2011: ORV not fully completed; spring 2014: ORV not carried out.</p