Epidemiologic monitoring of wild animals is always an important step in defining potential zoonoses that can threaten humans. Particular emphasis should be given to those zoonotic agents permanently cycling within wild animal populations and represent a permanent reservoir for other wild or domesticated animals that can be direct sources of disease for humans. In Croatia, there are two European jackal populations: the Dalmatian population (DP) that has been inhabiting the islands and coastal area along the Adriatic Sea since medieval times, and the South East European population (SEEP) that is found in continental Croatia. Research on Trichinella infections in jackal populations in Croatia was conducted from 2008 to 2022. During this 15-year period, we tested 186 jackal samples and confirmed infection in 47 individuals (25.3 %). The dominant species was T. spiralis, identified in 28 samples (60 %), T. britovi was found in 13 samples (28 %), while for six samples (12 %) the PCR test was unsuccessful. In both populations, the Trichinella species of the domestic cycle (T. spiralis) was found, though in varying ratios: in DP the ratio of identified species was 10:6 in favour of T. britovi, as opposed to 22:3 in favour of T. spiralis in SEEP. The frequency of infection with parasites from the genus Trichinella was significantly different in DP (22.9 %) than in SEEP (26.7 %) (p<0.001), while the larval count in analysed tissue did not differ by type of Trichinella species (p=0.1028). Infected jackals were found in nine of ten tested counties. The results were analysed statistically and the origin of tested and positive samples shown on a map of Croatia. Based on these findings, both jackal populations can be considered to represent an exceptionally important indicators of parasites from the genus Trichinella in Croatia, both for the sylvatic and domestic cycles. There is an evident need for epidemiological monitoring for members of both populations.

In Serbia, modern pork production systems with implemented control measures, including the detection of Trichinella larvae in meat (ISO18743), have eliminated farmed pork from pigs slaughtered at abattoirs as a source of trichinellosis. Epidemiological data from 2011 to 2020 indicate that the number of human cases and the number of infected domestic pigs has decreased significantly. Over the years, pork was the most frequent source of human infection. Cases generally occurred in small family outbreaks, and the infection was linked to consumption of raw or undercooked pork from backyard pigs. In most of the outbreaks, T. spiralis was the aetiological agent of infection, but in 2016, a large outbreak was caused by consumption of uninspected wild boar meat containing T. britovi larvae. To achieve safe pork, it is important that consumers of pork from animals raised in backyard smallholdings and of wild game meat are properly educated about the risks associated with consumption of untested meat. Laboratories conducting Trichinella testing should have a functional quality assurance system to ensure competency of analysts and that accurate and repeatable results are achieved. Regular participation in proficiency testing is needed.

Serological methods are widely used for detection of infections in animals and humans. The recommendations provided here take into account the best current methods for the serological detection of Trichinella infection. They are based on current scientific information including unpublished data from laboratories with relevant expertise in this field. These recommendations represent the official position of the International Commission on Trichinellosis (ICT) regarding acceptable methods for the use and interpretation of serology testing for Trichinella infection in animals and humans. The ICT does not recommend use of serological methods for testing individual carcasses of animals at slaughter for assuring food safety. For detection of human infections, for epidemiological studies in animals and humans, and for monitoring Trichinella infection in swine, the ICT recommends ELISA using excretory/secretory (ES) antigens. These antigens are obtained from the in-vitro maintenance of Trichinella spiralis muscle larvae and are recognized by sera from hosts infected by all Trichinella species and genotypes identified thus far. In most situations, positive results obtained by ELISA should be confirmed by western blot. Serological assays should be properly standardized and validated for their intended purpose. The components of the test that are critical for maintaining suitable performance should be identified and appropriately checked. Users of commercial tests should verify that the test has been adequately evaluated by an independent body. Serology is useful for detecting Trichinella in animals and humans but its limitations need to be taken into account when interpreting the results.

BACKGROUND: Raccoon dogs and red foxes are well-adapted hosts for Trichinella spp. The aims of this study were to estimate Trichinella infection prevalence and biomass and to investigate which Trichinella species circulated in these indicator hosts in Estonia.
METHODS: From material collected for evaluating the effectiveness of oral vaccination program for rabies eradication in wildlife, samples from 113 raccoon dogs and 87 red foxes were included in this study. From each animal, 20 g of masseter muscle tissue was tested for the presence of Trichinella larvae using an artificial digestion method. The Trichinella larvae were identified to species level by multiplex polymerase chain reaction method.
RESULTS: The majority of tested animals were infected with Trichinella spp. The parasite species identified were T. nativa and T. britovi. The apparent infection prevalence was 57.5% in raccoon dogs and 69.0% in red foxes, which were higher than previous estimates. In addition, the larval burden had also increased in both hosts. We estimated that in 2011-2012, the Trichinella spp. biomass was more than 15 times higher in raccoon dogs and almost two times higher in red foxes than in 1992-2000 (based on mean larval burden), and almost 20 times higher in raccoon dogs and almost five times higher in red foxes than in 2000-2002 (based on median larval burden).
CONCLUSIONS: Raccoon dogs and red foxes are relevant reservoirs for Trichinella spp. in Estonia. The biomass of Trichinella circulating in sylvatic cycles was substantial and had increased: there is substantial infection pressure in the sylvatic cycle.

Trichinella spiralis and Trichinella pseudospiralis exhibit differences in the host-parasite relationship such as the inflammatory response in parasitized muscles. Several studies indicate that matrix metalloproteinases (MMPs) represent a marker of inflammation since they regulate inflammation and immunity. The aim of this study was to evaluate the serum levels of gelatinases (MMP-9 and MMP-2) in mice experimentally infected with T. spiralis or T. pseudospiralis, to elucidate the involvement of these molecules during the inflammatory response to these parasites. Gelatin zymography on SDS polyacrilamide gels was used to assess the serum levels and in situ zymography on muscle histological sections to show the gelatinase-positive cells. In T. spiralis infected mice, the total MMP-9 serum level increased 6 days post-infection whereas, the total MMP-2 serum level increased onward. A similar trend was observed in T. pseudospiralis infected mice but the MMP-9 level was lower than that detected in T. spiralis infected mice. Significant differences were also observed in MMP-2 levels between the two experimental groups. The number of gelatinase positive cells was higher in T. spiralis than in T. pseudospiralis infected muscles. We conclude that MMP-9 and MMP-2 are markers of the inflammatory response for both T. spiralis and T. pseudospiralis infections.