Occurrence of Alaria alata in wild boars (Sus scrofa) in Poland and detection of genetic variability between isolates

Abstract

Alaria alata is a trematode included among several emerging zoonotic parasites. The mesocercarial larval stage of A. alata named Distomum musculorum suis (DMS) may potentially be infective for humans. In the past, DMS was often observed in wild boar meat during the official Trichinella inspection by artificial digestion before a more specific and effective detection method, the A. alata mesocercariae migration technique (AMT), was introduced. In the present study, the AMT method was used to screen 3589 tissue samples collected from wild boars hunted in Poland during the 2015-2019 period. The survey mainly focused on the southern part of Poland with the majority of samples coming from Małopolskie, Świętokrzyskie, and Dolnoślaskie provinces; samples from ten additional provinces were also included. The total prevalence was 4.2% with mean abundance of 4.7 DMS. Occurrence was dependent upon environmental conditions (i.e., wetland habitats and water reservoirs) rather than on sex of the host or season in which they were hunted. The recovered trematodes were identified as Alaria spp. according to their morphological features. Molecular analysis of 18S rDNA and COI genes confirmed the species identification to be A. alata and documented genetic variability among the isolates.

Keywords: AMT; Alaria alata; DMS; Poland; Wild boars.

Fig. 1

Alignment of the 17 different COI sequences of A. alata isolates collected from wild boars

Fig. 2

Unrooted cladogram of partial COI A. alata sequences together with A. americana (MH536507.1) as outgroup

Fig. 3

Alaria alata prevalence in wild boars in Poland. For each province, the number of tested wild boars and the parasite prevalence (in brackets) is reported. The rising of prevalence in provinces were signed by gradient blue color (from light blue to the dark blue); provinces from which no samples were tested was colored in gray