title: A 38-year study on Trichinella spp. in wild boar (Sus scrofa) of Latvia shows a stable incidence with an increased parasite biomass in the last decade.
abstract: BACKGROUND
  Trichinella spp. are zoonotic parasites transmitted to humans by the consumption of raw or insufficiently cooked meat of different animal species. The most common source of infection for humans is meat from pigs and wild boar (Sus scrofa). The aim of the present work was to evaluate the incidence of Trichinella spp. infections in wild boar hunted in Latvia over a 38 year interval (1976 to 2013).
  
  
  METHODS
  A total 120,609 wild boars were individually tested for Trichinella spp. by trichinoscopy and, in case of negativity, by artificial digestion of 25 g muscles, in the 1976-2005 period, and by artificial digestion of 25-50 g muscles in the 2006-2013 period. Trichinella spp. larvae were identified at the species level by multiplex PCR.
  
  
  RESULTS
  In the study period, the overall prevalence of infected wild boar was 2.5%. Trichinella britovi was the predominant (90%) species. The incidence of Trichinella spp. infection in wild boar exhibited two different trends. From 1976 to 1987, the incidence of infected/hunted wild boar increased from 0.23% to 2.56%, then it decreased to 0.19 in 1994. Thereafter, the incidence fluctuated between 0.05% and 0.37%. A statistically significant (P < 0.05) correlation (r = 0.54; p = 0.0199) was found between the trend of Trichinella spp. incidence in hunted wild boar and the number of snow cover days from 1976 to 1993. From 1997 to 2013, the estimated wild boar population of Latvia increased by 4.9 times and the hunting bag by 9.7 times, with a stable incidence of Trichinella spp. in the population. It follows that the biomass of Trichinella spp. larvae and of T. britovi, in particular, increased.
  
  
  CONCLUSIONS
  The incidence trends of Trichinella spp. in wild boar could be related to the role played by the snow in reducing the thermal shock and muscle putrefaction which increases the survival of the larvae in muscle tissues of carrion in the 1976-1993 period; and, in the 1997-2013 period, to the increased biomass of Trichinella spp. due to the increased carnivore populations, which are the main reservoirs of these parasites.
authors.affiliation: Daugavpils University, Institute of Life Sciences and Technology, Daugavpils, Latvia. muza.kirjusina@du.lv.
authors.forename: Muza
authors.initials: M
authors.lastname: Kirjušina
authors.affiliation: Institute of Food Safety, Animal Health and Environment "BIOR", Riga, Latvia. gunita.deksne@bior.lv.
authors.forename: Gunita
authors.initials: G
authors.lastname: Deksne
authors.affiliation: European Union Reference Laboratory for Parasites, Istituto Superiore di Sanità, Rome, Italy. gianluca.marucci@iss.it.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Marucci
authors.affiliation: Daugavpils University, Institute of Life Sciences and Technology, Daugavpils, Latvia. edlasen@gmail.com.
authors.forename: Eduards
authors.initials: E
authors.lastname: Bakasejevs
authors.affiliation: Daugavpils University, Institute of Life Sciences and Technology, Daugavpils, Latvia. inese.jahundovica@du.lv.
authors.forename: Inese
authors.initials: I
authors.lastname: Jahundoviča
authors.affiliation: Daugavpils University, Institute of Life Sciences and Technology, Daugavpils, Latvia. atlantida26@inbox.lv.
authors.forename: Anžela
authors.initials: A
authors.lastname: Daukšte
authors.affiliation: Daugavpils University, Institute of Life Sciences and Technology, Daugavpils, Latvia. zdankovska@inbox.lv.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Zdankovska
authors.affiliation: Institute of Food Safety, Animal Health and Environment "BIOR", Riga, Latvia. zanda.berzina@bior.lv.
authors.forename: Zanda
authors.initials: Z
authors.lastname: Bērziņa
authors.affiliation: Institute of Food Safety, Animal Health and Environment "BIOR", Riga, Latvia. zanda.esite@bior.lv.
authors.forename: Zanda
authors.initials: Z
authors.lastname: Esīte
authors.affiliation: CNESPS, Istituto Superiore di Sanità, Rome, Italy. antonino.bella@iss.it.
authors.forename: Antonino
authors.initials: A
authors.lastname: Bella
authors.affiliation: SIDBAE, Istituto Superiore di Sanità, Rome, Italy. fabio.galati@iss.it.
authors.forename: Fabio
authors.initials: F
authors.lastname: Galati
authors.affiliation: Riga Stradiņš University, Riga, Latvia. angelika.krumina@rsu.lv.
authors.forename: Angelika
authors.initials: A
authors.lastname: Krūmiņa
authors.affiliation: European Union Reference Laboratory for Parasites, Istituto Superiore di Sanità, Rome, Italy. edoardo.pozio@iss.it.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Pozio
mesh_terms: D000818:Animals; D018533:Biomass; D015994:Incidence; D007844:Latvia / Q000453:epidemiology; D025202:Molecular Diagnostic Techniques; D010274:Parasitology; D016133:Polymerase Chain Reaction; D034421:Sus scrofa / Q000469:parasitology*; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000469:parasitology*; D014234:Trichinella / Q000254:growth & development*; D014235:Trichinellosis / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*