Trichinella species in wild animals in Estonia

ABSTRACT. Trichinella infections in animals pose a worldwide public health concern, including in Estonia. The doctoral thesis comprises of five independent studies: four studies on Trichinella spp. epidemiology in wild animals and pigs in Estonia, and a study evaluating methods for detecting Trichinella spp. in meat. The results show convincingly, that wild animals, including game species play an important role as reservoirs of Trichinella spp. in Estonia. No antibodies against Trichinella spp. were found in domestic pigs, but anti-Trichinella IgG antibodies were found in 42.1% of wild boars. Trichinella infection was detected in 69.0% of red foxes, 57.5% of raccoon dogs, 0.9% of wild boars, 14.7% of brown bears, 65.6% of Eurasian lynxes, three out of five European badgers, and none of the investigated moose. Four Trichinella species were identified in Estonia: T. nativa, T. britovi, T. spiralis and T. pseudospiralis. The findings of T. pseudospiralis and T. spiralis were the first in wild animals in Estonia. In wild boars and lynxes, Trichinella spp. prevalence was higher in the northern and western regions, and significantly lower in the southeast when compared to the southwest, northwest, and northeast. Identified risk factors for Trichinella infection in wild boars and lynxes included the year, age group, and geographical unit. The high Trichinella infection pressure from wild hosts poses a risk for transmission to domestic pigs and humans via game meat consumption. Therefore, continuous monitoring is essential to collect data on changes in Trichinella epidemiology in Estonia, facilitating effective risk assessment.

The publication of this dissertation is supported by the Estonian University of Life Sciences.

LÜHIKOKKUVÕTE. Loomadel esinevatel keeritsussinakkustel on märkimisvääne mõju rahvatervisele paljudes riikides, sealhulgas Eestis. Doktoritöö koosneb viiest osast: neli uuringut hõlmasid Trichinella spp. epidemioloogiat metsloomadel ja kodusigadel Eestis ning viies, kirjanduse ülevaade, käsitles lihas Trichinella spp. tuvastamise meetodeid. Uurimistöö tulemused näitavad, et metsloomadel, sealhulgas jahiulukitel on oluline roll Trichinella spp. levikul Eestis. Trichinella spp. antikehi ei leitud kodusigadel, kuid anti-Trichinella IgG esines metssigadel (42,1%). Trichinella spp. infektsioone leiti rebastel (69,0%), ilvestel (65,6%), kährikkoertel (57,5%), karudel (14,7%), metssigadel (0,9%) ning viiest uuritud mägrast kolmel; nakkust ei leitud ühelgi uuritud põdral. Eestis leiti neli keeritsussi liiki: T. nativa, T. britovi, T. spiralis ja T. pseudospiralis, kusjuures T. spiralis ja T. pseudospiralis leiti metsaloomadel Eestis esmaleidudena. Metssigadel ja ilvestel oli Trichinella spp. levimus põhja- ja läänepiirkondades suurem kui lõuna- ja idapiirkondades ning edela-, loode- ja kirdepiirkondades suurem võrreldes kagupiirkonnaga. Metssigade ja ilveste Trichinella spp. nakatumise riskiteguriteks olid aasta, vanuserühm ja geograafiline üksus. Trichinella spp. suur nakkussurve ohustab seakasvatusi ning toiduks kütitud nakatunud ulukid on omakorda ohuks inimestele, mistõttu tuleb seirata metsloomi, et jälgida muutusi keeritsusside levikus ja liikide esinemises ning hinnata regulaarselt sellest tulenevaid riske.