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The wild boar ( Sus scrofa) population has increased markedly during the last three decades in Sweden and in other parts of Europe. This population growth may lead to increased contact between the wild boar and the domestic pig ( Sus scrofa scrofa), increasing the risk of transmission of pathogens. The objective of our study was to estimate the seroprevalence of selective pathogens, known to be shared between wild boars and domestic pigs in Europe, in three wild boar populations in Sweden. In total, 286 hunter-harvested female wild boars were included in this study. The sera were analyzed for antibodies against nine pathogens using different commercial or in-house enzyme-linked immunosorbent assays. Antibodies were detected against porcine parvovirus (78.0%), porcine circovirus type 2 (99.0%), swine influenza virus (3.8%), Erysipelothrix rhusiopathiae (17.5%), Mycoplasma hyopneumoniae (24.8%), and Toxoplasma gondii (28.6%). No antibodies were detected against porcine respiratory and reproductive syndrome virus, Brucella suis, or Mycobacterium bovis. Our results highlight the potential importance of the wild boar as a reservoir for pathogens potentially transmissible to domestic pigs and which also may affect human health.

BackgroundSarcoptic mange has recently emerged in wild boar in Switzerland, raising the question of the origin of the infection. The main aim of this study was to assess the extent of exposure of the wild boar populations to Sarcoptes scabiei in Switzerland, prior to and after the detection of mange cases, to determine whether the mite has been recently introduced into the populations concerned. We performed a serological survey using a commercially available ELISA and 1056 archived blood samples of free-ranging wild boar from Switzerland. To facilitate the interpretation of the obtained data, we additionally estimated seroprevalence in wild boar populations of four other European countries (1060 samples), both from areas with confirmed clinical cases of mange and from areas without reported cases in wild boar. Lastly, we revised the evaluation of the commercial ELISA when used with wild boar sera.ResultsSeropositive reactions were observed for samples from all five countries and from 15 of the 16 study areas. The obtained apparent seroprevalences ranged from 0.0% (0/82; 95% confidence interval [CI]: 0.0–4.4) to 17.4% (8/46; 95% CI: 7.8–31.4). Wild boar from study areas with known clinical cases and those ≤60 kg were four times more likely to be seropositive than wild boar from areas without reported cases and > 60 kg, respectively. Optical density values did not differ between the two types of study areas among seropositive samples but were significantly lower among seronegative samples from areas without than from areas with clinical cases. No difference was observed between the two sampling periods in Switzerland. The revised ELISA specificity was 96.8% (984/1017; 95% CI: 95.5–97.7) when wild boar from areas without history of mange were considered truly negative.ConclusionsSeropositivity to S. scabiei is more frequent and occurs over a larger geographic range than expected. Data suggest that the parasite is endemic within the wild boar populations of Switzerland and other European countries but that its presence is not necessarily associated with disease occurrence. Extrinsic factors which trigger disease emergence in infected populations remain to be investigated. The applied ELISA represents a promising tool for future studies.Electronic supplementary materialThe online version of this article (10.1186/s12917-018-1430-3) contains supplementary material, which is available to authorized users.

BackgroundThe number and spatial distribution of wild boars (Sus scrofa) has increased remarkably in Sweden as well as in other European countries. To understand the population dynamics of the wild boar, knowledge of its reproductive period, oestrus cycle and reproductive success is essential. The aim of this study was therefore to describe the seasonal reproductive pattern and reproductive potential of a wild boar population in Sweden. The study was based on findings from macroscopic examinations of the reproductive organs from 575 hunter-harvested female wild boars (>30 kg body weight). Samples were collected between December 2011 and December 2015 in the southern and middle parts of Sweden. The age of the sampled animals was determined and dressed weight was noted. The stage of the reproductive cycle was defined according to ovarian structures and in relation to the appearance of/and findings in the uterus. The crown-rump length (CRL) of the embryos/foetuses was used to calculate the oestrus/mating month and month for the expected farrowing.ResultsThe macroscopic examination revealed a seasonal variation of reproductive stages, although cyclic and pregnant females were found in all seasons. Moreover, the estimated oestrus/mating and farrowing months based on the CRL showed that mating and farrowing may occur ‘off-season’. The average litter size (no. of embryos or foetuses) per pregnant female was 5.4. Sow weight and age had significant effect on both the reproductive potential (ovulation rate and litter size) and pregnancy rate, respectively.ConclusionsThe reproductive potential in the studied wild boar population was high compared to studies from other countries and farrowing may occur ‘off-season’. This suggests that the environmental conditions in Sweden, including supplemental feeding, are favourable for wild boar reproduction.Electronic supplementary materialThe online version of this article (doi:10.1186/s13028-017-0321-0) contains supplementary material, which is available to authorized users.

BackgroundSince the re-appearance of wild boars in Sweden in the 1970s, the population has increased. Besides having large litter sizes, puberty at an early age is considered as an important factor contributing to the high reproductive potential of wild boar. Although controversial, supplemental feeding is applied to varying extent throughout the wild boar range in Sweden, and its effect on wild boar reproduction is debated. The aim of this study was to investigate the proportion of post-pubertal female wild boar gilts in a population subjected to supplemental feeding, in relation to age, weight, and season. Also, the effect of another definition of puberty (based upon follicular size) on the outcome of the proportion of female wild boar gilts considered to be able to reproduce in a population was illustrated. Between Jan 2013 and Dec 2015 reproductive organs from 592 female wild boars, were collected. Ovaries and uterus were macroscopically examined, and reproductive stage was determined by the presence of ovarian structures and uterus characteristics. Age was estimated using tooth eruption and tooth replacement, and weight was noted. A subset of 175 female wild boars, aged 5–15 months, was included in this study. An animal was considered to be post-pubertal if the ovaries contained one or more corpora lutea (CL) or if the uterus showed signs of previous pregnancy (presence of enlarged blood vessels in the cut surface between the mesometric ligament and the uterus).ResultsIn total, 29 (16.6 %) animals were classified as post-pubertal. Field dressed weight ranged from 20.6 to 65.3 kg. Season, weight, and age class significantly influenced the variation in proportion of post-pubertal females. Post-pubertal animals were found in autumn, winter, and spring, but not in the summer season. Another definition of puberty, based on follicle size, lead to different result on proportions of animals considered to have passed puberty.ConclusionsSeason, weight, and age significantly influenced the variation in proportion of post-pubertal wild boar females. The proportion of post-pubertal animals increased with age and weight. However, weight is probably a better proxy for puberty than age group is. The proportion of post-pubertal females also increased from summer to spring suggesting a seasonal reproductive pattern. Different definitions of puberty will result in various outcomes, which high-lights the importance of using adequate definition of puberty.