Animal welfare and zoonosis risk: anti-Trichinella antibodies in breeding pigs farmed under controlled housing conditions

Abstract

Background Domesticated pigs are the main source of Trichinella sp. infections for humans, particularly when reared in backyards or free-ranging. In temperate areas of southern Europe, most pigs are farmed under controlled housing conditions, but sows and sometimes fattening pigs have access to outdoors to improve animal welfare. The aim of the present study was to investigate whether outdoor access of breeding pigs farmed under controlled housing conditions can represent a risk for Trichinella sp. transmission when the farm is located in an agricultural area interspersed with wooded areas and badlands, where Trichinella spp. could be present in wildlife. Methods Serum samples were collected from 63 breeding sows and one boar before and after their access to an open fenced area for 2 months and from 84 pigs that never had outdoor access. Samples were screened for anti-Trichinella antibodies by ELISA, and positive sera were confirmed using Western blot (Wb) excretory/secretory antigens. To detect Trichinella sp. larvae, muscle tissues from serologically positive and negative pigs were tested by artificial digestion. Results Thirteen (20.6%) sows and one boar tested positive with both ELISA and Wb. No larvae were detected in muscle samples of serologically positive and serologically negative pigs. Positive serum samples were then tested by Wb using crude worm extract as antigens. The Wb banding pattern displayed was that characteristic of encapsulated species (Trichinella spiralis or Trichinella britovi). Conclusions The detection of anti-Trichinella antibodies without larvae in the pig muscles, supported by epidemiological data, suggests that pigs may have been exposed to T. britovi. This study stresses the importance of instigating monitoring systems at farm level to prevent Trichinella sp. transmission and to investigate, through a landscape parasitological study, the suitability of a site before the planting of a high containment level pig farm in which the sows can have outside access to improve their welfare during pregnancy. Graphical abstract

The European Union One Health 2022 Zoonoses Report

“…Farming practices at risk of transmitting Trichinella spp. (rearing outdoor, backyard or free‐range pigs (Pozio et al., 2021 ) occur, in general, in disadvantaged and poor areas where veterinary services do not exist or are unable to control many small pig units, or where veterinary supervision can be circumvented (Pozio, 2014 ). There are examples from the past where countries had suitable controls in place for parasite management in domestic pigs but where changes in pork production affected by socioeconomic conflicts resulted in the re‐emergence of trichinellosis as a severe public health problem (Djordjevic et al., 2003 ; Cuperlovic et al., 2005 ).…”

Serosurveillance of Trichinella sp. in wild boar and Iberian domestic suids in Mediterranean ecosystems of southwestern Spain

“…infection for public health, such as the increased demand for pig and wild boar products (Gamble, 2022), or the population dynamics of wild boar and the interactions between wild boar and pigs in specific free‐range production systems (Díaz et al., 2021). Moreover, the possibility of transmission of the parasite in those backyards and free‐range productions systems derived from incorrect human activities (Pozio, Celli, et al., 2021), and the illegal introduction of pig and wild boar meat in European countries (Rostami et al., 2017), should be also considered. Therefore, there is a permanent need for epidemiological studies on Trichinella sp.…”

“…may occur. Iberian pigs, raised under open extensive management systems, having access to rodents and wild boar, is considered a major source of infection of Trichinella sp., and may suppose a risk for human infection (Gamble, 2022; Pozio, Celli, et al., 2021). Thus, it would be interesting to identify pathways that enables the infection and identify potential risk areas.…”

Global prevalence ofTrichinellain pigs: A systematic review and meta‐analysis

“…In non‐intensive management systems (backyard, free roaming or traditional), the housing, feeding supply, and veterinary care can be poor, with pigs scavenging on domestic or agricultural scraps (Nwanta et al., 2011 ). Given lack of details on some of the production systems in the included studies, the impact of indoor versus outdoor production (separate from intensity) could not be assessed, although studies have shown that outdoor production can increase Trichinella exposure (Pozio et al., 2021 ). This is an area in which further research is needed, considering the number of outdoor production systems and consumer trends towards free‐range or organically produced meat in high HDI countries (Delsart et al., 2020 ; EFSA Panel on Animal Health and Welfare et al., 2021 ).…”