Global geographic distribution of Trichinella species and genotypes

From wildlife to humans: The global distribution of Trichinella species and genotypes in wildlife and wildlife-associated human trichinellosis

Zoonotic nematodes of the genus Trichinella are foodborne parasites that have a global distribution in wild carnivores and omnivores, with spillover and spillback into domestic livestock and people, with concomitant trade and health consequences. Historically, most human cases were linked to domestic pigs infected with Trichinella spiralis, but under current high biosecurity swine production in many countries, wildlife have become a more important source of human trichinellosis. The aim of this review is to update the global distribution of Trichinella species and genotypes reported in wildlife, as well as reported human outbreaks from the consumption of wildlife. Using several online databases and by "snowballing" references, hundreds of reports of Trichinella spp. in wildlife published between January 1991 and December 2023 provide an important update to the host and geographic range for each of the recognized 13 species/genotypes, grouped by continent. Surveillance effort was highest in Europe and North America, while Africa, Asia, Oceania, Central and South America have had limited surveillance, in some instances with human cases serving as sentinels of transmission in a region. Dozens of human outbreaks are described, with wild boars (Sus scrofa) being the most frequently implicated wildlife species in human outbreaks globally. Bears are an important source of infection in North America, for wildlife tourism, and importation of bear meat has also been implicated in multicountry outbreaks. The largest study limitation was the dearth of molecular identification of larvae in both wildlife surveillance studies and human outbreaks, particulary in under-studied regions. We highlight the need for enhanced molecular epidemiological approaches to outbreaks of this important foodborne parasite, and emphasize the need for a One Health approach to manage Trichinella spp. which transmit among terrestrial and marine wildlife (including migratory birds), pigs, horses, and people, often across large geographic scales and borders.

Predicted distribution of Metaparasitylenchus hypothenemi (Tylenchida: Allantonematidae), parasite of the coffee berry borer

Metaparasitylenchus hypothenemi is an endoparasitic nematode of the coffee berry borer Hypothenemus hampei. The nematode has only been recorded across a limited geographical range in coffee-growing areas of southeastern Mexico. Because of its confined geographical distribution, the effect of altitude, temperature, and mean annual precipitation on M. hypothenemi's presence/absence in the Soconusco region of Mexico was investigated. The geographical distribution of this parasite was predicted based on current data, using geographical information systems (GIS), the MaxEnt algorithm, and historical data to improve the prediction accuracy for other Neotropical regions. In Soconusco, the presence of this parasite is directly related to annual precipitation, especially in the areas with the highest annual rainfall (4000 - 4700 mm/year). Four species distribution models were generated for the Neotropical region with environmental variables for sites with parasite presence data, predicting a range of possible distribution with a high probability of occurrence in southeastern Mexico and southwestern Guatemala and a low probability in areas of Central and South America. Characterization of the abiotic habitat conditions suitable for M. hypothenemi development allows us to predict its distribution in the Neotropics and contributes to our understanding of its ecological relationship with environmental variables.

Genetic identification of Trichinella species found in wild carnivores from the territory of Kazakhstan

Trichinellosis, also called trichinosis, is a foodborne parasitic disease caused by eating raw or undercooked meat from animals infected with Trichinella spp. larvae and affects both animals and humans. Although on the territory of Kazakhstan, the species characteristics and prevalence of this helminth were studied back in the 90s, the data have not been updated since then. Given the above, our study was aimed at identifying Trichinella spp. using parasitological and molecular genetics methods. In our work, we studied 160 samples of muscle tissue of wild animals living in the natural zones of steppes and semi-deserts. Of the animals examined, 32 were positive for Trichinella spp., including 1 lynx (Lynx lynx), 17 wolves (Canis lupus), 11 foxes (Vulpes vulpes), 1 jackal (Canis aureus) and 2 corsac foxes (Vulpes corsac). Helminths were extracted using the digestion method. DNA was extracted using a Gene Jet commercial kit (Thermo Fisher Scientific, United Kingdom). For species identification a multiplex PCR, amplification of ESV, ITS1, and ITS2 genes regions was performed. After that, uniplex PCR was performed on the 5S rDNA and ITS1 genes region for sequencing analysis. The resulting sequences were subsequently used to construct a phylogenetic tree and the studied samples were identified as Trichinella nativa and Trichinella britovi. Thus, we can conclude that there is a circulation of two species of Trichinella in Kazakhstan, highlighting that constant control and monitoring of wild animals are necessary to prevent transmission and protect the health of people.

Trichinella spiralis and T. britovi in North-Eastern Romania: A Six-Year Retrospective Multicentric Survey

Simple Summary

The genus Trichinella includes roundworm parasites with a wide geographical spread that can cause illness in humans and animals. In this context, an epidemiological study of Trichinella infection was carried out in the northeastern part of Romania to investigate for the first time its prevalence in pigs, horses, wild boars and bears, the geographical distribution of Trichinella species and the natural reservoir of the parasites. Between 2010 and 2015, a total of 166,270 animals were examined by specific methods in order to calculate the prevalence of Trichinella infection, the involved species, and their geographical distribution. The overall prevalence of Trichinella infection in animals was 0.188%. But the specific prevalence varied as follows: in pigs 0.096%, horses 0.021%, wild boar 1.46% and bears 36.76%. The geographical distribution showed that T. spiralis was dominant, occupying the entire northeastern part of Romania, being identified in pigs, horses, wild boars and bears. T britovi occupied five mountain counties, being identified only in wild boars and bears. These results validate the presence of T. spiralis and T. britovi in domestic and game animals in northeast Romania and warn about the risk of human infection in the region.

Abstract

The genus Trichinella includes species with a wide geographical spread that cause pathology in humans and animals. In this context, an epidemiological study of Trichinella infection was carried out in the northeastern part of Romania to investigate for the first time the prevalence of this infection in pigs, horses, wild boars and bears, the geographical distribution of Trichinella species and the natural reservoir of Trichinella infection. Between 2010 and 2015, a total of 166,270 animals were examined by the method of artificial digestion, in order to calculate the annual and general prevalence of Trichinella infection, according to the host and the Trichinella species involved, the Pearson correlation coefficient (r), trendline and geographical distribution of species of the genus Trichinella. Taxonomic framing was performed by the multiplex PCR method. The overall prevalence of Trichinella infection in animals was 0.188%. Within the host species, the prevalence varied as follows: in pigs 0.096%, horses 0.021%, wild boar 1.46% and bears 36.76%. The geographical distribution showed that T. spiralis was dominant, occupying the entire northeastern part of Romania, being identified in pigs, horses, wild boars and bears. T britovi occupied five mountain counties, being identified only in wild boars and bears. These results validate the presence of T. spiralis and T. britovi in domestic and game animals in the northeastern part of Romania.

Bioinformatic Prediction and Production of Four Recombinant Proteins from Different Developmental Stages of Trichinella spiralis and Testing of Their Diagnostic Sensitivity in Mice

Background:

Trichinellosis is a serious food-borne parasitic zoonosis, thus finding high quality antigens is the key to serodiagnosis of trichinosis. This article reports the characterization and sensitivity of four recombinant proteins expressed by four genes (Wn10, Zh68, T668, and Wm5) from different developmental stages of Trichinella spiralis for the diagnosis of trichinellosis in mice.

Methods:

This study was conducted in Jilin University and National Institute of Parasitic Diseases of Chinese Center for Disease Control and Prevention in 2017–2018. The structures and functions of the proteins encoded by four genes were predicted by bioinformatics analysis. The four genes were cloned and expressed, and the recombinant proteins were purified. Anti-Trichinella IgM and IgG antibodies in the sera of mice infected with T. spiralis from 1-45 d post-infection (dpi) were evaluated by ELISA.

Results:

The optimal antigen epitopes of four proteins (P1, P2, P3, and P4) encoded by the four genes from T- and B-cells were predicted, and four purified recombinant proteins (r-P1, r-P2, r-P3, and r-P4) were successfully produced. For IgM, the antibody levels detected by the four recombinant antigens were approximately equal to the cut-off value. Anti-Trichinella IgG antibodies were first detected by r-P1 at 8 dpi, followed by r-P2, r-P3, and r-P4 at 10 dpi, 14 dpi, and 16 dpi, respectively, and the antibody levels remained high until 45 dpi.

Conclusion:

The recombinant antigens r-P1, r-P2, r-P3, and r-P4 could be antigens that react with antibodies, they showed high sensitivity in the detection of anti-Trichinella IgG antibodies in mice. Among these proteins, r-P1 may be a candidate antigen for the detection of anti-Trichinella IgG antibodies in the early infection phase and exhibited the best sensitivity among the antigens.

Exploiting the potential of 2D DIGE and 2DE immunoblotting for comparative analysis of crude extract of Trichinella britovi and Trichinella spiralis muscle larvae proteomes

The Trichinella genus poses an interesting puzzle for researchers, having diverged very early in the evolution of the nematodes. The Trichinella spiralis proteome is a cosmopolitan and well-studied model of Trichinella; however, Trichinella britovi also circulates in the sylvatic environment and both species infect humans, resulting in the development of trichinellosis. Few experiments have examined the proteins belonging to the T. britovi proteome. The aim of the present study was to compare the protein expression profiles of crude extracts of T. spiralis and T. britovi muscle larvae using a highly-sensitive two-dimensional differential in-gel electrophoresis (2D DIGE) technique coupled with 2DE immunoblotting. Selected immunoreactive protein spots were then identified by liquid chromatography coupled with mass spectrometry analysis (LC-MS/MS), and their function in Trichinella and the host-parasite interaction was determined by gene ontology analysis. Spots common to both T. spiralis and T. britovi, spots with different expressions between the two and spots specific to each species were labelled with different cyanine dyes. In total, 196 protein spots were found in both proteomes; of these 165 were common, 23 expressed exclusively in T. spiralis and 8 in T. britovi. A comparative analysis of volume ratio values with Melanie software showed that among the common spots, nine demonstrated higher expression in T. spiralis, and 17 in T. britovi. LC-MS/MS analysis of 11 selected spots identified 41 proteins with potential antigenic characteristics: 26 were specific for T. spiralis, six for T. britovi, and eight were found in both proteomes. Gene Ontology analysis showed that the identified T. spiralis proteins possess hydrolytic endopeptidase, endonuclease and transferase activities. Similarly, most of the T. britovi proteins possess catalytic activities, such as lyase, hydrolase, isomerase and peptidase activity. The applied 2D DIGE technique visualized Trichinella spp. protein spots with different molecular weights or isoelectric point values, as well as those with different expression levels. The identified immunoreactive proteins participate in multiple processes associated with host muscle cell invasion and larval adaptation to the host environment. Their reactivity with the host immune system makes them possible candidates for the development of a novel trichinellosis diagnostic test or vaccine against helminthiasis caused by T. spiralis or T. britovi.

Trichinella britovi as a risk factor for alternative pig production systems in Greece and Europe

Trichinellosis is an important zoonosis and the most common source of human infection is meat from pigs and wild boars. The European Union (EU) supports alternative pig production systems (organic and free-ranging) as sustainable farming systems. However, these systems that allow outdoor access for farm animals, may create new or reintroduce old risks to public health. During the last years, alternative pig production systems (free-ranging or organic pig) are growing in popularity in Greece due to the increasing interest of consumers for organic products. The majority of the trichinellosis outbreaks in the EU were associated with pork and meat products including wild boars. In Greece, from 2009 to 2012, 37 Trichinella spp. positive free-ranging pigs were reported in free-ranging pig farms of Northern-Eastern Greece (31 were identified as T. britovi). The recent re-emerging present of the Trichinella spp. infections in free-ranging pigs and wild boars are a high risk for the consumers and should alarm the Public Health Authorities in Greece and the EU. During the last years, the organic or free-ranging pig production systems are growing in popularity in the EU. However, these systems increase the risk of Trichinella spp. infections, since pigs are possible to be infected by feeding on carcasses or the offal of hunted or dead wild animals. For this reason, it is important for Public Health Authorities to be focused on the training of hunters and farmers in order to avoid the transmission among free-ranging pigs and prevent the cases of human infection.

Trichinella britovi infection and muscle distribution in free-living martens (Martes spp.) from the Głęboki Bród Forest District, Poland

Trichinella nematodes occur in many carnivorous and omnivorous animal species in the sylvatic cycle. Due to their widespread occurrence throughout Poland and diet, free-living Mustelids can act as a potential reservoir for nematodes of the genus Trichinella and play a role in their circulation. The study was designed to determine the presence and predilection sites for Trichinella nematodes in martens (Martes spp.) from the Głęboki Bród Forest District, Poland.

Trichinella britovi larvae were detected by molecular methods in 17.54% examined martens (prevalence: 41.67% among pine martens and 13.88% among Martes spp.). The intensity of infection varied from 0.17 to 37.29 larvae per gram (LPG) (mean 5.43; median 3.4). The highest larval burdens were detected in the tongue in pine martens (Martes martes) and the diaphragm in Martes spp., respectively; the lowest levels were found in the masseter in pine martens and the tongue in Martes spp. No statistically significant difference in the intensity of infection was observed between males and females in either group.

Our findings indicate that T. britovi is present in martens from the Głęboki Bród Forest District, and the predilection sites for the nematode may differ between males and females. However, due to the low number of examined animals, further studies are necessary to confirm whether they are an important element in the maintenance of Trichinella nematodes in the examined area.

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Trichinella britovi was found in Martes spp. from the Głęboki Bród Forest District, Poland.

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The parasite was identified in 41.67% of pine martens (Martes martes) and 13.88% of Martes spp.

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The highest larval burdens were detected in the tongue for pine martens and in the diaphragm for Martes spp.

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The marten is an important host for the maintenance of T. britovi among wildlife in the area.

Lipid profile of Trichinella papuae muscle-stage larvae

Outbreaks of trichinellosis caused by Trichinella papuae have been reported in South-East Asia. Mebendazole and thiabendazole are the treatments of choice for trichinellosis; however, both drugs result in significant side effects and are less effective for muscle-stage larvae (L1). An alternative therapeutic agent is needed to improve treatment. Information on lipid composition and metabolic pathways may bridge gaps in our knowledge and lead to new antiparasitics. The T. papuae L1 lipidome was analysed using a mass spectrometry-based approach, and 403 lipid components were identified. Eight lipid classes were found and glycerophospholipids were dominant, corresponding to 63% of total lipids, of which the glycerolipid DG (20:1[11Z]/22:4[7Z,10Z,13Z,16Z]/0:0) (iso2) was the most abundant. Overall, 57% of T. papuae lipids were absent in humans; therefore, lipid metabolism may be dissimilar in the two species. Proteins involved T. papuae lipid metabolism were explored using bioinformatics. We found that 4-hydroxybutyrate coenzyme A transferase, uncharacterized protein (A0A0V1MCB5) and ML-domain-containing protein are not present in humans. T. papuae glycerophospholipid metabolic and phosphatidylinositol dephosphorylation processes contain several proteins that are dissimilar to those in humans. These findings provide insights into T. papuae lipid composition and metabolism, which may facilitate the development of novel trichinellosis treatments.

Intestinal microbes influence the survival, reproduction and protein profile of Trichinella spiralis in vitro

The interactions between intestinal microbes and parasitic worms play an essential role in the development of the host immune system. However, the effects of gut microbes on Trichinella spiralis are unknown. The aim of this work was to explore microbe-induced alterations in the survival and reproduction of T. spiralis in vitro. To further identify the proteins and genes involved in the response of nematodes to microbes, quantitative proteomic analysis of T. spiralis was conducted by iTRAQ-coupled LCMS/MS technology and quantitative real-time-PCR was used to measure changes in mRNA expression. The results showed Lactobacillus acidophilus, and especially Lactobacillus bulgaricus, significantly enhanced the survival and reproductive rates of nematodes. Salmonella enterica, and especially Escherichia coli O157:H7 (EHEC), had opposite effects. Genetic responses were activated mainly by EHEC. A total of 514 proteins were identified and quantified, and carbohydrate metabolism-related proteins existed in a higher proportion. These findings indicated that some gut bacteria are friendly or harmful to humans and in addition they may have similar beneficial or detrimental effects on parasites. This may be due to the regulation of expression of specific genes and proteins. Our studies provide a basis for developing therapies against parasitic infections from knowledge generated by studying the gut microbes of mammals.

Wild boars meat as a potential source of human trichinellosis in Poland: current data

Trichinellosis is an epidemiological problem with a global distribution. In Poland a substantial increase of the wild boar population has been observed since 2010, together with an increased incidence of trichinellosis after ingestion of raw or undercooked wild boar products containing Trichinella spp. larvae. However, the actual number of human cases remains particularly difficult to determine. The aim of the present study was to determine the current prevalence and spread of these parasites within wild boars. The diaphragm pillars and tongue from 833 wild boars were collected from 2010 to 2014, as well as one wild boar meat sausage known to be a source of infection. The samples were tested for Trichinella spp. using pepsin digestion. Recovered larvae were identified at species level by multiplex polymerase chain reaction (multiplex PCR). The overall prevalence in all examined samples was found to be 2.0% (17/833). Recovered larvae were identified as T. spiralis and T. britovi (9/18 and 5/18, respectively). T. spiralis larvae were isolated from the sausage. Mixed infection was confirmed only once. Three isolates were not identified. The results of our study confirm that the wild boar plays a key role in the maintenance of Trichinella nematodes through the sylvatic cycle.

Characterisation of a high-frequency gene encoding a strongly antigenic cystatin-like protein from Trichinella spiralis at its early invasion stage

Background

The intestinal phase is the early invasion stage of Trichinella spiralis (T. spiralis), in which muscle larvae invade intestine epithelial cells and then develop into adult worms to breed newborn larvae. Thus, intestinal infective larvae are first exposed to the immune system of the host, and antigens from the worms may be the earliest marker in the diagnosis of trichinellosis and may contribute to vaccine development to prevent Trichinella infections in pigs.

Methods

A cDNA library of intestinal infective larvae of T. spiralis at 6 hours post infection (p.i.) was constructed and immunoscreened using serum collected from pigs that were infected with T. spiralis at 26 days p.i. T. spiralis cystatin-like protein (Ts-CLP) gene encoding a 45.9 kDa protein was cloned and expressed in Escherichia coli. The rabbit antisera were generated and used to determine the location of Ts-CLP in the parasite. Transcription levels of Ts-CLP in different developmental stages of T. spiralis were observed by RT-PCR. The potential application of recombinant Ts-CLP in diagnosis against T. spiralis infection was tested by ELISA. The immune protection of recombinant Ts-CLP protein against T. spiralis infection was evaluated in mice.

Results

Thirty-three positive clones were selected from cDNA library, among which 20 clones encoded the same novel cystatin-like protein (Ts-CLP). Immunolocalisation and real-time quantitative PCR revealed that native Ts-CLP was localised primarily to β-stichocytes and that the Ts-clp gene was transcribed and expressed in all developmental stages of T. spiralis. The recombinant protein rTs-CLP was recognised by pig antiserum as early as 15 days p.i., and could induce protective immunity in mice, with a 61.21% reduction in the number of muscle larvae.

Conclusions

These data preliminarily suggested that Ts-CLP may play an important role in the early infection of T. spiralis and that recombinant Ts-CLP protein is a candidate antigen for diagnosis and vaccine development in Trichinella infections.