Trichinellosis: the zoonosis that won't go quietly

Enhanced Genomic and Transcriptomic Resources for Trichinella pseudospiralis and T. spiralis to Underpin the Discovery of Molecular Differences between Stages and Species

Nematodes of the genus Trichinella are important pathogens of humans and animals. This study aimed to enhance the genomic and transcriptomic resources for T. pseudospiralis (non-encapsulated phenotype) and T. spiralis (encapsulated phenotype) and to explore transcriptional profiles. First, we improved the assemblies of the genomes of T. pseudospiralis (code ISS13) and T. spiralis (code ISS534), achieving genome sizes of 56.6 Mb (320 scaffolds, and an N50 of 1.02 Mb) and 63.5 Mb (568 scaffolds, and an N50 value of 0.44 Mb), respectively. Then, for each species, we produced RNA sequence data for three key developmental stages (first-stage muscle larvae [L1s], adults, and newborn larvae [NBLs]; three replicates for each stage), analysed differential transcription between stages, and explored enriched pathways and processes between species. Stage-specific upregulation was linked to cellular processes, metabolism, and host-parasite interactions, and pathway enrichment analysis showed distinctive biological processes and cellular localisations between species. Indeed, the secreted molecules calmodulin, calreticulin, and calsyntenin-with possible roles in modulating host immune responses and facilitating parasite survival-were unique to T. pseudospiralis and not detected in T. spiralis. These insights into the molecular mechanisms of Trichinella-host interactions might offer possible avenues for developing new interventions against trichinellosis.

Identification and profiling of Trichinella spiralis circulating antigens and proteins in sera of mice with trichinellosis

Trichinellosis is a zoonotic disease caused by the ingestion of the Trichinella nematode. With a worldwide incidence of approximately 10,000 cases per year, Trichinella spiralis is responsible for most human infections. There are no specific signs or symptoms of this parasitic infection. Muscle biopsy is the gold diagnostic standard for trichinellosis, but the technique is invasive and unable to detect the early stage of infection. Although immunodiagnostics are also available, antibody detection usually occurs after 3 weeks and prolonged up to 19 years after the acute phase. Therefore, additional diagnostic biomarkers must be identified to improve trichinellosis diagnosis. This study aimed to measure concentration changes in mouse serum proteins prior to T. spiralis infection and 2, 4 and 8 weeks after infection, and to identify T. spiralis circulating proteins and antigens using mass spectrometry-based proteomics. Mouse muscle-related proteins including inter-alpha-trypsin inhibitor heavy chain H2, a protein involved in the response to muscle tissue damage, were up-regulated in mouse sera during the T. spiralis larvae invasion. Additionally, 33 circulatory parasite proteins were identified in infected mouse sera. Notably, T. spiralis long-chain fatty acid transport protein 1 could be detected in the early stage of infection and peroxidasin-like protein was identified 2, 4 and 8 weeks after infection. Seventeen T. spiralis circulating antigens were detected in mouse immune complexes, with PX domain protein being found 2, 4 and 8 weeks after infection. Because peroxidasin-like protein and PX domain protein were detected at all post-infection time points, sequence alignments of these proteins were performed, which showed they are conserved among Trichinella spp. and have less similarity to the human and murine sequences. Integrative analysis of T. spiralis biomarkers throughout the course of infection may reveal additional diagnostic targets to improve early diagnosis of trichinellosis.

Seroprevalence and Associated Risk Factors of Trichinellosis and T. Solium Cysticercosis in Indigenous Pigs in Hoa Binh Province, Vietnam

Trichinellosis and cysticercosis remain challenges to human health and animal productivity worldwide, especially in developing countries. While information on the occurrence of both diseases is infrequent, they are endemic in parts of Vietnam and mainly related to indigenous pigs kept by ethnic minorities. This study aimed to determine the seroprevalence and risk factors of both diseases in indigenous pigs and explore the perception and awareness of both human and pig trichinellosis and cysticercosis of pig farmers. A total of 352 pig sera samples from 131 holdings were collected and analyzed using ELISA antibody tests in six communes in the Da Bac districts of Hoa Binh province, Vietnam. A survey was conducted with representatives from these households to understand the knowledge and perspective on food-borne parasitic diseases. Overall, the seroprevalence of trichinellosis and T. solium cysticercosis was 13.6% (95% CI 10.2–17.7) and 1.7% (95% CI 0.6–3.7), respectively. The seroprevalence of trichinellosis was significantly higher in female and older pigs. Risk perception and knowledge of interviewed people on both human and pig trichinellosis and cysticercosis of pig farmers was poor. Risky practices, including free roaming of pigs and eating undercooked or fermented pork, were observed. Educational and awareness campaigns aligned with further research on feasible practice changes are critical to addressing these issues.

Seropositive Wild Boars Suggesting the Occurrence of a Wild Cycle of Trichinella spp. in Brazil

Trichinella is a zoonotic nematode traditionally detected worldwide in both domestic and wild animals. In South America, along with the occurrence of this parasite in domestic pigs and wild boars, there are reports of infection in wild carnivores. Brazil is considered free of the domestic cycle of Trichinella, but there is unpublished serological evidence of infection in wild boars, which changed the Brazilian status in OIE regarding the disease after an official communication. We investigated Trichinella spp. infection in wild boars and wild carnivores in the Southeastern region of Brazil. A total of 136 samples were tested, 121 from wild boars and 15 from wild carnivores. Artificial enzymatic digestion (AED) tests were performed on muscle samples from 37 wild boars and 15 wild carnivores, and 115 serum samples from wild boars were tested by iELISA. Seven serum samples from wild boars tested positive (7/115 = 6.1%, 95% CI 3.0–12.0), but no larvae were found in the AED. There was no significant difference between sex, age, and location of the samples. The serological results suggest that a wild cycle of Trichinella spp. may occur in Brazil, but further analyses should be performed to confirm the presence of the parasite.

Trichinella spiralis-associated myocarditis mimicking acute myocardial infarction

BACKGROUND

Trichinellosis is a parasitic infection caused by nematodes of the genus Trichinella, and its principal mode of transmission is the consumption of raw or undercooked contaminated meat. Cardiac involvement in trichinellosis is unusual, yet it represents the most frequent cause of death. Here, we report a case in which Trichinella spiralis-associated myocarditis simulated a myocardial infarction.

CASE PRESENTATION

A 35-year-old African man with no previous medical history was admitted to the emergency department for acute substernal discomfort at rest described as a pressure with no radiation. The electrocardiogram performed upon admission showed non-specific alterations of repolarization. Blood biology revealed high levels of troponin T and predominant eosinophilic leukocytosis. A transthoracic echocardiography was carried out and found a significant left ventricular concentric hypertrophy with a preserved ejection fraction. The septal and inferior walls, as well as the endocardium were hyperechogenic. The patient was hospitalized for eosinophilic myocarditis. The cause of hypereosinophilia was investigated, and a Trichinella spiralis serology came back strongly positive. A diagnosis of Trichinella spiralis associated-myocarditis was made.The patient was treated with albendazole-prednisolone dual therapy with favorable clinical and biological outcomes.

CONCLUSION

The clinical suspicion of trichinellosis is based on suggestive epidemiology associated with the typical clinical presentation and the presence of eosinophilia. Eosinophilic myocarditis is a severe complication of trichinellosis which can result in death due to rhythm disorders. Chest pain, increase in troponins, and electrocardiographic abnormalities are all elements that can mimic a myocardial infarction and mislead clinicians.Abbreviations: ANCA: Anti-Neutrophil Cytoplasmic Antibodies; ANA: Anti-Nuclear Antibodies; ECDC: European Centre for Disease Prevention and Control; ECG: Electrocardiogram; ELISA: Enzyme-Linked ImmunoSorbent Assay; EMF: Endomyocardial Fibrosis; ES: Excretory-Secretory; ICT: International Commission on Trichinellosis; MRI: Magnetic Resonance Imaging.

Development of an immunochromatographic point-of-care test for detection of IgG antibody in serodiagnosis of human trichinellosis

OBJECTIVE

Trichinellosis is a globally distributed food-borne parasitic disease. Initially, diagnosis is usually made based on clinical signs, symptoms, and history of eating raw or undercooked meat. In the present study, an immunochromatographic test (ICT) kit was developed to diagnose trichinellosis by detecting IgG antibodies in sera of infected humans.

METHODS

Somatic extract from Trichinella spiralis larvae was used as the antigen for the ICT kit development. Diagnostic efficacy was evaluated using human serum samples from proven trichinellosis patients, healthy persons, and those with other parasitic infections.

RESULTS

The diagnostic sensitivity, specificity, positive and negative predictive values and accuracy of the ICT kit were 100.0% (95%; CI 88.8 to 100.0%), 92.5% (95% CI; 86.9 to 96.2%), 73.8% (95% CI; 58.0 to 86.1%), 100.0% (95% CI; 97.3 to 100.0%) and 93.8% (95% CI; 89.2 to 96.9%), respectively.

CONCLUSIONS

This ICT diagnostic kit can be used as a testing tool for human trichinellosis. This test should permit rapid detection of infection to enable prompt anthelminthic treatment. It can also be used for retrospective diagnoses and field surveys based at laboratories where sophisticated equipment is lacking.

First record of Trichinella in Leopardus guigna (Carnivora, Felidae) and Galictis cuja (Carnivora, Mustelidae): new hosts in Chile

Background

Trichinellosis is a zoonotic disease with a worldwide distribution. It is caused by several species of nematodes in the genus Trichinella. Trichinella spp. are transmitted through predation or carrion consumption and occur in domestic and sylvatic cycles. In humans trichinellosis occurs due to the consumption of raw or undercooked, infected meat and is mainly associated with the household slaughter of pigs or the consumption of game animals without veterinary inspection, a cultural practice that is difficult to resolve. Therefore, knowledge of this parasite's reservoir is relevant for better implementing public health strategies. The aim of this study was to assess the presence of Trichinella sp. in several carnivore and omnivore vertebrates in central-southern Chile.

Methods

We collected muscle tissue from a total of 53 animals from 15 species and were digested to detect Trichinella larvae which were further identified to species level using molecular techniques.

Results

We detected Trichinella larvae in Leopardus guigna (Felidae) and Galictis cuja (Mustelidae). We identified the larvae collected from L. guigna as Trichinella spiralis, but we were unable to molecularly characterize the larvae from G. cuja. This is the first record of Trichinella in a native mustelid of South America and the first record of T. spiralis in L. guigna. This study identified two novel hosts; however, further work is needed to identify the role that these and other hosts play in the cycle of Trichinella in Chile.

Trichinella britovi infection in wild boar in Portugal

Trichinella spp. infection occurs when a host ingests muscle tissue containing infective larvae (L1 stage). Wild boar meat and its products represent the second largest source of human trichinellosis worldwide. For this reason, and since that in Portugal wild boar is the most hunted large game specie, the laboratory of Technology, Quality and Food Safety (TQFS) from the University of Trás-os-Montes e Alto Douro created a free service to test wild boar meat for Trichinella spp. From December 2015 to February 2020, and 857 samples were analysed. From those, the majority (719/857, 83.9%) were tested after October 2018 when a specific national legislation came into force, demanding that meat from wild boar hunted in a defined risk area should be tested for Trichinella spp. Under TQFS laboratory activity, in January 2020, a positive case was identified, being the first molecular confirmation of Trichinella britovi infection in wild boar in Portugal. Additionally to this activity, in 2019, a questionnaire was submitted to 100 hunters to acquire information about wild boar meat usage and consumption behaviours. From the total respondents, 86% declared they intended to use meat for private consumption. Of those, 93% also stated that have sold part of the meat and/or homemade sausages, the majority (80%) without prior testing for Trichinella spp., as required by EU Regulation. These results alert the hunters to a risk for human infection, which could be extended to outside the hunter's household. Given the actual epidemiological situation, it should be emphasized that testing for Trichinella spp. in wild boar meat should be maintained and reinforced, particularly in the risk area. The results presented in this report strongly support the importance of specific national legislation to mitigate the risk of trichinellosis due to consumption of non-tested wild boar meat.

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.

Alvaxanthone, a Thymidylate Synthase Inhibitor with Nematocidal and Tumoricidal Activities

With the aim to identify novel inhibitors of parasitic nematode thymidylate synthase (TS), we screened in silico an in-house library of natural compounds, taking advantage of a model of nematode TS three-dimensional (3D) structure and choosing candidate compounds potentially capable of enzyme binding/inhibition. Selected compounds were tested as (i) inhibitors of the reaction catalyzed by TSs of different species, (ii) agents toxic to a nematode parasite model (C. elegans grown in vitro), (iii) inhibitors of normal human cell growth, and (iv) antitumor agents affecting human tumor cells grown in vitro. The results pointed to alvaxanthone as a relatively strong TS inhibitor that causes C. elegans population growth reduction with nematocidal potency similar to the anthelmintic drug mebendazole. Alvaxanthone also demonstrated an antiproliferative effect in tumor cells, associated with a selective toxicity against mitochondria observed in cancer cells compared to normal cells.

Epidemiology of taeniosis, cysticercosis and trichinellosis in Iran: A systematic review

BACKGROUND

The aim of this review was to establish the current epidemiology of taeniosis, cysticercosis and trichinellosis among humans and animals in Iran by carrying out a comprehensive assessment of published articles reporting on these foodborne zoonotic diseases across the country.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was used in the search for relevant published articles reporting on cysticercosis, taeniosis and trichinellosis in Iran using a number of appropriate key words. The search was conducted through PubMed, Web of Science, Google Scholar, SpringerLink, SCOPUS, WHOLIS, FAO and CDC. Published scientific articles including journals, books and book chapters reporting on cysticercosis, taeniosis and trichinellosis in Iran for the period between 1967 and 2018 were selected.

RESULTS

A total of 37 articles met the search criteria and were incorporated in this review. Of these, 10 (27%) reported on human taeniosis, 15 (40.5%) on cysticercosis (10 on Taenia saginata and five on Taenia spp. cysticercosis) and 12 (32.5%) on trichinellosis. T. saginata was implicated in all human taeniosis cases. All Taenia spp. cysticercosis cases were reported among domesticated pigs and wild animals. A case of neurocysticercosis was reported in a male patient at Shohada Hospital in Tehran. Eleven (91.7%) of the 12 studies reported on trichinellosis among wild animals, while one (8.3%) study detected anti-Trichinella IgG in 8 (2.2%) of the 364 at-risk human beings tested. Nevertheless, most of these studies were carried out in northern Iran.

CONCLUSION

This review found T. saginata to be the most prevalent and of greater economic and public health significance in Iran. However, T. solium and Trichinella spp. were of little significance to human health. More studies should focus on other regions besides northern Iran.

Advances in kinome research of parasitic worms - implications for fundamental research and applied biotechnological outcomes

Protein kinases are enzymes that play essential roles in the regulation of many cellular processes. Despite expansions in the fields of genomics, transcriptomics and bioinformatics, there is limited information on the kinase complements (kinomes) of most eukaryotic organisms, including parasitic worms that cause serious diseases of humans and animals. The biological uniqueness of these worms and the draft status of their genomes pose challenges for the identification and classification of protein kinases using established tools. In this article, we provide an account of kinase biology, the roles of kinases in diseases and their importance as drug targets, and drug discovery efforts in key socioeconomically important parasitic worms. In this context, we summarise methods and resources commonly used for the curation, identification, classification and functional annotation of protein kinase sequences from draft genomes; review recent advances made in the characterisation of the worm kinomes; and discuss the implications of these advances for investigating kinase signalling and developing small-molecule inhibitors as new anti-parasitic drugs.

Epizootic and Epidemiological Situation of Trichinella sp. Infection in Poland in 2006-2015 in View of Wild Boar Population Dynamics

Introduction

The objective was to evaluate the epizootic and epidemiological situation of Trichinella sp. infection in Poland between 2006 and 2015 against the dynamics of the wild boar population and its primary reservoir host.

Material and Methods

Boar and porcine trichinosis epizootic analysis was based on General Veterinary Inspectorate data from RRW-6 bulletins. The epidemiological situation was evaluated on the basis of the data supplied by the Department of Epidemiology of the National Institute of Hygiene - National Institute of Public Health. The wild boar hunting harvest and population dynamics were estimated, as these animals remain the basic infection source for humans. Population size and harvest data were obtained from hunting statistics.

Results

The study timeframe showed an almost 2.5-fold increase in Trichinella infection cases in wild boars but a significant decline in human cases. In the domestic pig, the incidence rate did not exceed 0.00037%. The highest infection risk exists in West Pomerania, Greater Poland, and Kuyavian-Pomeranian Provinces. Over the study period, the wild boar population increased more than 1.5-fold, while the hunting harvest more than tripled. During the last two seasons the total hunt surpassed 100% of the spring population.

Conclusion

Wild boar management by increasing the hunting take of the annual population growth should limit that growth and decrease the take in the future. Thereby, over some years intra-species trichinosis spread should reduce, for a substantial safety gain for wild boar meat.

Crystal structures of nematode (parasitic T. spiralis and free living C. elegans), compared to mammalian, thymidylate synthases (TS). Molecular docking and molecular dynamics simulations in search for nematode-specific inhibitors of TS

Three crystal structures are presented of nematode thymidylate synthases (TS), including Caenorhabditis elegans (Ce) enzyme without ligands and its ternary complex with dUMP and Raltitrexed, and binary complex of Trichinella spiralis (Ts) enzyme with dUMP. In search of differences potentially relevant for the development of species-specific inhibitors of the nematode enzyme, a comparison was made of the present Ce and Ts enzyme structures, as well as binary complex of Ce enzyme with dUMP, with the corresponding mammalian (human, mouse and rat) enzyme crystal structures. To complement the comparison, tCONCOORD computations were performed to evaluate dynamic behaviors of mammalian and nematode TS structures. Finally, comparative molecular docking combined with molecular dynamics and free energy of binding calculations were carried out to search for ligands showing selective affinity to T. spiralis TS. Despite an overall strong similarity in structure and dynamics of nematode vs mammalian TSs, a pool of ligands demonstrating predictively a strong and selective binding to TsTS has been delimited. These compounds, the E63 family, locate in the dimerization interface of TsTS where they exert species-specific interactions with certain non-conserved residues, including hydrogen bonds with Thr174 and hydrophobic contacts with Phe192, Cys191 and Tyr152. The E63 family of ligands opens the possibility of future development of selective inhibitors of TsTS and effective agents against trichinellosis.

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.

The first report of Trichinella pseudospiralis presence in domestic swine and T. britovi in wild boar in Bosnia and Herzegovina

The Balkans is endemic for nematodes of the genus Trichinella in both domestic and wild animals. The high prevalence of these zoonotic pathogens in animals linked with the food habits to consume raw meat and meat derived products resulted in a very high prevalence of trichinellosis in humans living in this European region. In spite of numerous epidemiological investigations carried out in this region, very few information is available on the Trichinella species circulating in Bosnia and Herzegovina. Trichinella spp. larvae were isolated from a domestic pig reared in a backyard and from a hunted wild boar whose meat had been the source of trichinellosis in one case. Both Trichinella pseudospiralis and T. spiralis have been identified in the domestic pig, whereas, T. britovi was detected in the wild boar. While, T. spiralis is the Trichinella species most frequently detected in domestic pigs, T. pseudospiralis has been previously documented in domestic pigs only three times in Russia, Slovakia and Croatia. The detection of T. britovi in the wild boar confirms that this nematode is the most frequent species circulating among wildlife of Europe.

New finding of Trichinella britovi in a European beaver (Castor fiber) in Latvia

We report the first finding of Trichinella britovi in a European beaver. In Latvia, beaver is a common game animal and frequently used in human diet. A high prevalence of Trichinella infections in Latvia is present in the most common hosts-carnivores and omnivores. In total, 182 European beaver muscle samples were tested for Trichinella larvae accordingly to the reference method of European Communities Commission Regulation (EC) No. 2075/2005 (2005). Trichinella britovi larvae were detected in one animal (prevalence 0.5%; intensity 5.92 larvae per gram of muscle). This finding suggests that the consumption of European beaver meat can be a risk to human health. Further studies are needed in order to determine if the present observation represents an isolated individual case or low prevalence of Trichinella infection in beavers.

Efficacy of maslinic acid and fenbendazole on muscle larvae of Trichinella zimbabwensis in laboratory rats

Trichinellosis is a zoonotic disease caused by nematode species of the genus Trichinella. Anthelmintics targeting the intestinal adults and muscle-dwelling larvae of Trichinella spp. have been tested, with limited success. This study was aimed at determining the efficacy of maslinic acid and fenbendazole on muscle larvae of Trichinella zimbabwensis in laboratory rats. Forty-two Sprague–Dawley rats, with an average weight of 270 g and 180 g for males and females respectively, were infected with T. zimbabwensis larvae. Infected rats were randomly assigned to three groups which were subjected to single treatments with each of maslinic acid, fenbendazole and a combination of both on day 25 post-infection (pi), and three groups which were subjected to double treatments with each of these drugs and a combination on days 25 and 32 pi. The untreated control group received a placebo. In single-treatment groups, the efficacy of each treatment, measured by rate of reduction in muscle larvae, was significant (P< 0.001) for both drugs compared to the untreated control group. There was no apparent synergistic effect on the combination of the two drugs in reducing the muscle larval burden, either in single or double treatments. In all the treatment regimens, the reductions were significant (P< 0.001) when compared to the untreated control and not significant when the single treatments were compared with the double treatments (P>0.05). We conclude that the efficacy of maslinic acid against larval stages of T. zimbabwensis in rats was comparable to that of fenbendazole, with no side-effects observed, making maslinic acid a promising anthelmintic against larval stages of Trichinella species.

Protective effect of a prime-boost strategy with the Ts87 vaccine against Trichinella spiralis infection in mice

Trichinellosis is a widespread zoonosis primarily caused by Trichinella spiralis. Mucosal immunity is crucial for preventing Trichinella spiralis infection. In our previous study, a DNA vaccine with the Trichinella antigen Ts87 delivered by an attenuated Salmonella typhimurium elicited partial protection against Trichinella spiralis infection in mice. In the current study, to elicit a more robust immune response and develop a potent vaccination strategy against trichinellosis, a heterologous prime-boost vaccination regimen for Ts87 was used in mice and the protective efficacy was evaluated compared to the homologous DNA prime-boost or protein prime-boost immunization alone. The results revealed that the DNA-prime/protein-boost vaccination with Ts87 induced higher levels of both humoral and cellular immune responses. The challenge results showed that mice with the DNA-prime/protein-boost vaccination displayed higher muscle larval reduction than those immunized with DNA prime-boost or protein prime-boost. The results demonstrated that mice vaccinated with Ts87 in a DNA-prime/protein-boost strategy effectively elicited a local IgA response and mixed Th1/Th2 immune response that might be responsible for improved protection against Trichinella spiralis infection.

The low global burden of trichinellosis: evidence and implications

Trichinellosis is a cosmopolitan foodborne disease that may result in severe health disorders and even death. Despite international awareness of the public health risk associated with trichinellosis, current data on its public health impact are still lacking. Therefore we assessed, for the first known time, the global burden of trichinellosis using the Disability-Adjusted Life Year metric. The global number of Disability-Adjusted Life Years due to trichinellosis was estimated to be 76 per billion persons per year (95% credible interval: 38-129). The World Health Organization European Region was the main contributor to this global burden, followed by the WHO region of the Americas and the World Health Organization Western Pacific region. The global burden of trichinellosis is much lower than that of other foodborne parasitic diseases and is in sharp contrast to the high budget allocated to prevent the disease in many industrialised countries. To decrease the uncertainty around the current estimates, more knowledge is needed on the level of underreporting of clinical trichinellosis in different parts of the world.

Detection of anti-Trichinella antibodies in serum of experimentally-infected swine by immunochromatographic strip

An immunochromatographic strip method, developed with the excretory-secretory antigens from muscle larvae (ML) of Trichinella spiralis labeled with colloidal gold, was used for the detection of anti-Trichinella antibodies in serum of experimentally-infected swine. Sera from swine infected with 200, 2000 and 20,000 infective ML were collected at different days post infection (dpi) and used to evaluate the method. The strip method was shown able to detect anti-Trichinella antibodies by 35 dpi, 28 dpi and 21 dpi for the three different infection doses, respectively, and closely correlated with the results of an ELISA test. The strip method is rapid and easy to perform and is suggested as an acceptable alternative for clinical laboratories lacking specialized equipment, and for field diagnosis of trichinellosis.

Comparison of three molecular detection methods for detection of Trichinella in infected pigs

Different molecular detection methods require diverse molecular platforms, but there is no uniform standard for people to reference in the detection of Trichinella. In this study, real-time PCR, loop-mediated isothermal amplification (LAMP), and conventional PCR were developed for the detection of Trichinella by targeting mitochondrial large subunit ribosomal DNA (mt-lsrDNA). We compared the performance of the three newly developed assays. The results revealed that the detection limits of the real-time PCR, LAMP, and conventional PCR assays were 10 and 100 fg/μL and 1 pg/μL of Trichinella spiralis genomic DNA, respectively. The assays were used in the detection of Trichinella in the field. A total of 192 samples were obtained from pigs: 75 samples from free range farming and 117 from intensive feeding factory. The infection rate was 8/192 (4.2 %), 7/192 (3.6 %), and 1/192 (1.0 %) through the real-time PCR, LAMP, and conventional PCR assays, respectively. These data indicate that Taqman real-time PCR was a rapid, specific, and sensitive tool as a preferred option for investigation of valuable samples, but that LAMP assay was closed tube, highly sensitive, cost-effective, rapid, easy-to-perform, and was the optimal choice for detection of Trichinella in the field. The results of a model of experimental infection in mice indicated that spleen can be used as sampling site for the detection of early T. spiralis infection. However, the diaphragm and myocardium were the most suitable sampling sites for the detection of T. spiralis.

The fifth outbreak of trichinosis in Korea

Trichinosis is a food-borne zoonotic disease caused by the nematode, Trichinella spp., and had been reported several times in Korea. Recently, there was an additional outbreak, involving 5 patients, the findings from which are reported herein. On 30 November 2010, 8 persons ate sashimi of the meat of a wild boar. Then, 2-3 weeks later, they complained of myalgia and fever. Unfortunately, muscle biopsy was not performed, but ELISA was performed using their sera. Two people among 8 were positive for Trichinella on the 34th day post-infection (PI), and 3 patients who initially revealed negative ELISA were additionally proved to be positive for trichinosis on the 42nd day PI. Hence, the confirmed patients of trichinosis were 5 in total in the present outbreak. They were treated with albendazole and discharged uneventfully. This was the fifth outbreak of trichinosis in Korea.

A study to demonstrate freedom from Trichinella spp. in domestic pigs in Switzerland

Trichinellosis is a food-borne zoonotic disease caused by the nematode Trichinella spp. Many omnivorous and carnivorous animal species can act as host for this parasite, including domestic pigs. To protect public health, it should be ensured that pork should not contain infective Trichinella larvae. Surveillance for Trichinella spp. can be done using direct (larval detection) and indirect (antibody detection) diagnostic techniques. The aim of this study was to demonstrate the absence of infection in Swiss domestic pigs. An ELISA was used as the initial screening test, and sera reacting in ELISA were further investigated using both a Western blot for serology and an artificial digestion test with 20 g of diaphragm tissue for larval detection. A total of 7412 adult pigs, 9973 finishing pigs and 2779 free-ranging pigs were tested. Samples from 17 (0.23%) adult pigs, 16 (0.16%) finishing pigs and nine (0.32%) free-ranging pigs were ELISA-positive, but all of these sera were subsequently negative by Western blot and by the artificial digestion method. Based on these findings, an absence of Trichinella infections in adult pigs (target prevalence 0.04%) and finishing pigs (target prevalence 0.03%) can be concluded. The results also demonstrated that the prevalence of Trichinella infections does not exceed 0.11% in free-ranging pigs, the group with the highest risk of exposure.

The epidemiology of human trichinellosis in China during 2004-2009

The endemic foci of human trichinellosis are mainly located in southwestern China. Seroepidemiological surveys of Trichinella spiralis infection in humans were carried out in 10 out of 34 Provinces/Autonomous Regions/Municipals (P/A/M) of China during 2004-2009. The overall seroprevalence was 3.19% (3198/100,282). The highest seroprevalences were mainly located in western China: 8.43% in Yunnan, 6.37% in Inner Mongolia and 5.35% in Sichuan. The seroprevalence of Trichinella infection in humans was related to the habit of eating meat and differed among nationalities. From 2004 to 2009, 15 outbreaks of human trichinellosis, consisting of 1387 cases and four deaths, were reported in the three southwestern-most P/A of China (nine outbreaks in Yunnan, two in Sichuan and four in Tibet), where ethnic groups routinely eat raw meat. Pork is the predominant source of outbreaks of human trichinellosis in China. Out of 15 outbreaks, 12 (85.71%) were caused by eating raw or undercooked pork, and 2 (13.33%) resulted from the consumption of raw wild boar, suggesting the significance of game meat as a source of infection for human trichinellosis. An outbreak of imported trichinellosis involving 49 cases in Yunnan during December 2006 from Laos is the first recorded outbreak of imported trichinellosis in China, but the source of that outbreak could not be identified. The mandatory inspection of pork should be further strengthened in southwestern China.

Identification and characterization of microRNAs in Trichinella spiralis by comparison with Brugia malayi and Caenorhabditis elegans

Trichinella spiralis is an important zoonotic nematode causing trichinellosis which is associated with human diseases such as malaise, anorexia, nausea, vomiting, abdominal pain, fever, diarrhea, and constipation. microRNAs (miRNAs) are endogenous small non-coding RNAs that play important roles in the regulation of gene expression. The objective of the present study was to examine the miRNA expression profile of the larvae of T. spiralis by Solexa deep sequencing combined with stem-loop real-time polymerase chain reaction (PCR) analysis. T. spiralis larvae were collected from the skeletal muscle of naturally infected pigs in Henan province, China, by artificial digestion using pepsin. The specific identity of the T. spiralis larvae was confirmed by PCR amplification and subsequent sequence analysis of the internal transcribed spacer of ribosomal DNA. A total of 17,851,693 reads with 2,773,254 unique reads were obtained. Eleven conserved miRNAs from 115 unique xsmall RNAs (sRNAs) and 12 conserved miRNAs from 130 unique sRNAs were found by BLAST analysis against the known miRNAs of Caenorhabditis elegans ( ftp://ftp.ncbi.nih.gov/genomes/Caenorhabditis_elegans ) and Brugia malayi dataset ( http://www.ncbi.nlm.nih.gov/genomeprj?Db=genomeprj&cmd=ShowDetailView&TermToSearch=9549 ) in miRBase, respectively. One novel miRNA with 12 precursors were identified and certified using the reference genome of B. malayi, while no novel miRNA was found when using the reference genome of C. elegans. Nucleotide bias analysis showed that the uracil was the prominent nucleotide, particularly at the 1st, 6th, 18th, and 23th positions, which were almost at the beginning, middle, and the end of the conserved miRNAs. The identification and characterization of T. spiralis miRNAs provides a new resource to study regulation of genes and their networks in T. spiralis.

An epidemiological overview of swine trichinellosis in China

Trichinellosis is a major food-borne zoonosis with health, social, and economic impacts. Epidemiological data on swine trichinellosis in China from 2005 to 2009 were obtained from seven Provinces/autonomous regions/Municipalities (P/A/M) and analyzed and sero-epidemiological data were acquired from five P/A. The seroprevalence ranged from 0.01% to 29.95% as determined by enzyme-linked immunosorbent assay or an immunochromatographic strip method. The prevalence of Trichinella infection in swine slaughtered at abattoirs varied from 0% to 5.75% in five P/A. Between 2005 and 2009, endemic areas of swine trichinellosis were located mainly in the Western (Guangxi and Qinghai), central (Henan and Hubei), and North-eastern parts (Heilongjiang) of China. Swine trichinellosis in China is transmitted mostly through garbage. Pigs infected with Trichinella are predominately from small backyard farms where animals are raised under poor hygienic conditions, and from rural and mountainous areas where they range freely at pasture. The prevalence of Trichinella in pork sold at the market was reported in four P/A, and varied from 0.06% to 5.6% as determined by trichinoscopy or the digestion method. From 2005 to 2009, 15 outbreaks of human trichinellosis, with 1387 cases and 4 deaths, were recorded in three P/A of South-western China. Twelve (85.71%) of these 15 outbreaks were caused by the eating of raw or undercooked pork, which remains the predominant source of trichinellosis in humans. Pig-rearing practices must be improved, and mandatory inspection of pork further strengthened in rural and mountainous areas in Western China for the control of the disease.

Social science implications for control of helminth infections in Southeast Asia

Social science perspectives can inform helminth disease control in Southeast Asia. The social science literature offers theoretical and conceptual models; research methods; recommendations for training and capacity building, health education and health care professional training; and practice guidelines, including implementation of evidence-based interventions. Priority themes include poverty, gender differences, health inequities and access to social resources. Implications for helminth control include broadening disease monitoring and surveillance to include social and economic variables and subjective measures of well-being; training for health professionals and researchers in the social determinants of health; and application of social science models, specifically the expanded 'Chronic Care Model', to the planning and evaluation of interventions. The chapter posits that helminth diseases meet the World Health Organization's expanded definition of chronic conditions, and that integrated delivery of multiple interventions is needed to address the full range of risks and outcomes due to helminth infection.

Comparing the demonstration of freedom from Trichinella infection of domestic pigs by traditional and risk-based surveillance

Traditionally, the routine artificial digestion test is applied to assess the presence of Trichinella larvae in pigs. However, this diagnostic method has a low sensitivity compared to serological tests. The results from artificial digestion tests in Switzerland were evaluated over a time period of 15 years to determine by when freedom from infection based on these data could be confirmed. Freedom was defined as a 95% probability that the prevalence of infection was below 0·0001%. Freedom was demonstrated after 12 years at the latest. A new risk-based surveillance approach was then developed based on serology. Risk-based surveillance was also assessed over 15 years, starting in 2010. It was shown that by using this design, the sample size could be reduced by at least a factor of 4 when compared with the traditional testing regimen, without lowering the level of confidence in the Trichinella-free status of the pig population.

Quantitative risk assessment for the annual risk of exposure to Trichinella spiralis in imported chilled pork meat from New Zealand to Singapore

AIMS

To determine the annual likelihood of exposure to an infectious dose of Trichinella spiralis from consuming imported pork meat from New Zealand to Singapore.

METHODS

Input values specific for chilled pork meat imported into Singapore from New Zealand were used in a quantitative risk-assessment model. The model, designed to allow any combination of importing and exporting countries, was divided into two components, viz the release assessment, and the exposure assessment that assessed the annual risk of exposure to the consumer (ARC). The former estimated the likelihood that a contaminated fresh meat product from New Zealand would arrive at Singapore's border, and took into consideration the prevalence of disease on different types of farms. The latter determined the likelihood over a year that a person in Singapore would consume one or more servings of imported fresh meat from New Zealand that contained a burden of greater than or equal to one larva(e) of T. spiralis per gram after preparation for consumption.

RESULTS

The ARC for offal was 2.41 x 10(-7), which was below the pre-selected safety threshold of 1.00 x 10(-6). The ARC for lean meat was 2.39 x 10(-5), which was above the acceptable safety threshold.

CONCLUSIONS

The study demonstrated that continued routine testing at slaughter is unnecessary for pig offal produced commercially, and provided a model with which to further assess management of the risk of exposure to T. spiralis in lean meat.

CLINICAL RELEVANCE

The potential of Trichinella species to cause disease in humans is a public health concern, and has created adverse effects on the international trade of fresh lean meat without regard to the surveillance measures employed by particular pork-producing countries.

Histopathology of trichinellosis in wild boar

Histopathological study of Trichinella constitutes an important knowledge base to understand the pathogenesis of this disease. This study analyses cell response and macroscopic lesions in wild boar for the two species of Trichinella present in Spain: Trichinella spiralis and T. britovi. We carried out both trichinelloscopy and artificial digestion to calculate the parasitic load and relate this to the macroscopic lesions. The results obtained prove a lesser adaptation of T. britovi in wild boar. From a histological point of view, the organic region that was most affected was the skeletal muscle, where inflammatory infiltrates were observed around the larvae, and they were most abundant in calcified cysts.

Epidemiology, diagnosis, treatment, and control of trichinellosis

SUMMARY

Throughout much of the world, Trichinella spp. are found to be the causative agents of human trichinellosis, a disease that not only is a public health hazard by affecting human patients but also represents an economic problem in porcine animal production and food safety. Due to the predominantly zoonotic importance of infection, the main efforts in many countries have focused on the control of Trichinella or the elimination of Trichinella from the food chain. The most important source of human infection worldwide is the domestic pig, but, e.g., in Europe, meats of horses and wild boars have played a significant role during outbreaks within the past 3 decades. Infection of humans occurs with the ingestion of Trichinella larvae that are encysted in muscle tissue of domestic or wild animal meat. Early clinical diagnosis of trichinellosis is rather difficult because pathognomonic signs or symptoms are lacking. Subsequent chronic forms of the disease are not easy to diagnose, irrespective of parameters including clinical findings, laboratory findings (nonspecific laboratory parameters such as eosinophilia, muscle enzymes, and serology), and epidemiological investigations. New regulations laying down rules for official controls for Trichinella in meat in order to improve food safety for consumers have recently been released in Europe. The evidence that the disease can be monitored and to some extent controlled with a rigorous reporting and testing system in place should be motivation to expand appropriate programs worldwide.

World distribution of Trichinella spp. infections in animals and humans

The etiological agents of human trichinellosis show virtually worldwide distribution in domestic and/or wild animals, with the exception of Antarctica, where the presence of the parasite has not been reported. This global distribution of Trichinella and varying cultural eating habits represent the main factors favouring human infections in industrialised and non-industrialised countries. Human trichinellosis has been documented in 55 (27.8%) countries around the world. In several of these countries, however, trichinellosis affects only ethnic minorities and tourists because the native inhabitants do not consume uncooked meat or meat of some animal species. Trichinella sp. infection has been documented in domestic animals (mainly pigs) and in wildlife of 43 (21.9%) and 66 (33.3%) countries, respectively. Of the 198 countries of the world, approximately 40 (20%) are small islands far from the major continents, or city-states where Trichinella sp. cannot circulate among animals for lack of local fauna (both domestic and wild). Finally, information on the occurrence of Trichinella sp. infection in domestic and/or wildlife is still lacking for 92 countries.