Trichinella spp. imported with live animals and meat

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.

Trichinella Infection in Culled Wild Boar (Sus scrofa) from El Palmar National Park, Argentina, and Exposure Risk in Humans and Dogs Consuming Wild Boar Meat

Trichinellosis is a foodborne disease caused by ingestion of raw or undercooked meat containing Trichinella spp. larvae. Consumption of wild boar (Sus scrofa) meat represents an important source of human trichinellosis worldwide. In El Palmar National Park (EPNP), Argentina, invasive alien wild boars are controlled and meat from culled animals is released for public consumption following on-site artificial digestion (AD) testing. Meat trimmings and offal from the control program are often used as food for dogs (Canis familiaris). We evaluated infection and exposure to Trichinella spp. in wild boars from EPNP, as well as exposure to Trichinella spp. and associated risk factors in dogs and human consumers of wild boar meat. Trichinella spp. larvae were detected in muscle samples from 5/49 wild boars by AD (10.2%; 95% confidence interval [CI], 3.8%-23%), with a mean burden of 0.24 larvae per gram (lpg; range, 0.06-0.95 lpg). Anti-Trichinella antibodies were not detected in wild boar serum samples (n=42). In dogs, 12/34 were seropositive to Trichinella spp. (35.29%; 95%, CI, 20.3%-53.5%). Immunoglobulin (Ig) G antibodies were not detected in human serum samples (n=63). Our results reveal the presence, albeit at low prevalence, of Trichinella spp. in wild boars and exposure in dogs fed game offal. These findings suggest that the low prevalence and parasitic load in wild boars, together with the best practices applied by EPNP culling program personnel, contribute to keeping the risk of infection in people low. The dog results highlight that the parasite is circulating in the area, and therefore the risk of infection is not negligible. We recommend the implementation of an animal surveillance strategy in order to monitor the evolution of this zoonosis in the study area.

Trichinella spiralis cathepsin B bound and degraded host's intestinal type I collagen

Trichinellosis is a zoonotic parasitic disease that poses threats to human health, the meat industry, food safety, and huge financial losses. The critical stage of Trichinella spiralis (T. spiralis) infection is the invasion of intestinal larvae into the host's intestinal epithelial cells (IECs). T. spiralis Cathepsin B (TsCB) specifically interacts with IECs to facilitate the invasion of larvae. This study aims to look at how TsCB affects mouse IECs. TsCB was successfully cloned, expressed, and characterized, demonstrating its natural cysteine protease hydrolysis activity. A total of 140 proteins that interact with rTsCB were identified by GST pull-down combined with LC-MS/MS, including type I collagen, an essential component of the host's intestinal epithelial barrier system and intimately related to intestinal epithelial damage. TsCB transcription and expression levels rise, whereas type I collagen in the host's intestinal mucosa declines when the T. spiralis larvae invaded. Besides, it was discovered that TsCB bound to and degraded type I collagen of the host's intestine. This research can serve as a foundation for clarifying how T. spiralis invades the host's intestinal barrier and might provide information on potential targets for the creation of novel treatments to treat parasite illnesses.

Pumpkin seeds (Cucurbita pepo subsp. ovifera) decoction promotes Trichinella spiralis expulsion during intestinal phase via "Weep and Sweep" mechanism

Trichinosis is a zoonotic disease of communal health concern as it instigated human outbreaks in several countries. Besides, the development of resistance, traditional therapy has numerous antagonistic effects. Thereby, finding efficient natural alternatives is required. In comparison to albendazole, this study evaluated the impact of pumpkin decoction on Trichinella spiralis in experimentally infected mice. The anthelmintic action of pumpkin decoction (500 mg/kg) was determined using T. spiralis infected mice in enteric phase for 5 days. Pumpkin decoction anthelmintic activity fortified by mixing with honey (1:1). Pumpkin decoction and Pumpkin decoction-honey mixture were evaluated by comprising with reference drug, albendazole (50 mg/kg). The T. spiralis adult count was significantly lower in all treated groups, with the pumpkin decoction-honey mixture showing the largest reduction (83.2%) when compared to the infected group (P ≤ 0.001). The intestinal histological changes and the level of COX-2 expression in the intestinal tissue were both significantly reduced in the same group. The pumpkin decoction improved the immune response, as evidenced by a significant decrease in nitric oxide (NO) and tumor necrosis factor (TNF-α) and a significant increase in the expression of the transforming growth factor (TGF-1β) and interleukin-17 (IL-17). The pumpkin decoction's anthelmintic action was facilitated by the TGF-1β and IL-17-driven Weep and Sweep mechanism. Both administration of pumpkin decoction beside honey showed the best treatment group that resulted in high infection reduction besides amelioration of biochemical markers and restoration of histological to normal state. In conclusion, pumpkin decoction is highly effective against T. spiralis which could be a promising alternative herbal drug and the pumpkin decoction effect was higher in the case of combination with honey.

Acetazolamide loaded-silver nanoparticles: A potential treatment for murine trichinellosis

Trichinellosis is a global food-borne disease caused by viviparous parasitic nematodes of the genus Trichinella. Due to the lack of effective, safe therapy and the documented adverse effects of traditional therapy, this study aimed to evaluate the therapeutic effect of acetazolamide-loaded silver nanoparticles (AgNPs) on murine trichinellosis. Fifty male Swiss albino mice were divided into five groups of ten mice each: Group I, normal control group; Group II, infected with T. spiralis and not treated; Group III, infected and given AgNPs; Group IV, infected and treated with acetazolamide; and Group V, infected and treated with acetazolamide-loaded AgNPs. Mice were infected orally with 250 larvae. The efficacy was assessed by counting T. spiralis adults and larvae, measuring serum total antioxidant capacity, and observing the histopathological and ultrastructural alterations. Acetazolamide-loaded AgNPs treatment exhibited the highest percentage of reduction (84.72% and 80.74%) for the intestinal adults and the muscular larvae of T. spiralis-infected animals, respectively. Furthermore, during the intestinal and muscular phases, the serum of the same group had the best free-radical scavenging capacity (antioxidant capacity), which reduced tissue damage induced by oxidative stress. Histopathologically, the normal intestinal and muscular architecture was restored in the group treated with acetazolamide-loaded AgNPs, in addition to the reduced inflammatory infiltrate that alleviated inflammation compared to infected animals. Our results confirmed the marked destruction of the ultrastructural features of T. spiralis adults and larvae. Acetazolamide-loaded AgNPs are a promising therapy against T. spiralis infection.

Invasive mammalian wildlife and the risk of zoonotic parasites

Invasive wild mammals are present in all continents, with Europe, North America, and the Asian-Pacific region having the largest number of established species. In particular, Europe has been the continent with the highest number of zoonotic parasites associated with invasive wild mammals. These invasive species may represent a major threat for the conservation of native ecosystems and may enter in the transmission cycle of native parasites, or act as spreaders of exotic parasites. Here, we review the role of invasive wild mammals as spreaders of zoonotic parasites, presenting important examples from Europe, America, and the Asia-Pacific region. Finally, we emphasize the need for more research on these mammals and their parasites, especially in areas where their monitoring is scantily performed.

Immunomodulatory in vitro effects of Trichinella cystatin-like protein on mouse splenocytes

Trichinella parasites have developed specific mechanisms allowing successful completion of their life cycle. These mechanisms are in a great part involved in immunomodulation and studying them may provide a valuable insight into the functioning of the immune system. Trichinella products may be also used as potential therapeutic agents to treat immune diseases. This study investigates the immunomodulatory potential of recombinant multi cystatin-like protein (CLP) derived from T. britovi to determine whether CLP has anti-inflammatory properties in vitro. CLP is a highly antigenic glycoprotein present in Trichinella excetory-secretory (ES) products. AlphaFold structure prediction confirms that it consists of three type-two cystatin-like domains. Mouse splenocytes were stimulated in vitro with lipopolysaccharide (LPS) and co-stimulated with recombinant CLP. The culture supernatants were collected and tested for secreted cytokine levels using ELISA. CLP was found to reduce LPS-induced secretion of inflammatory cytokines TNFα and IL-6. On the contrary, in some experimental groups, co-stimulation with CLP resulted in increased secretion of the regulatory cytokine IL-10. The obtained results indicate that CLP has anti-inflammatory properties and future research on its function is advisable, specifically in the context of the therapy of inflammatory disorders.

Real-time PCR versus traditional and Nano-based ELISA in early detection of murine trichinellosis

Trichinellosis is a serious foodborne zoonosis. It poses a serious risk to public health worldwide. Early serological diagnosis of trichinellosis is influenced by an immunological 'silent' phase following infection. This highlights the necessity for developing sensitive diagnostic approaches to be employed when antibodies cannot be detected. In this work, the validity of traditional ELISA, Nano-ELISA and real time polymerase chain reaction (PCR) were evaluated in early diagnosis of Trichinella spiralis. Swiss albino mice were orally infected with 100 and 300 muscle larvae/mouse. Mice were sacrificed 4, 6, 8, 10, 15, and 28 days post-infection (dpi). Blood samples were tested for circulating antigen by traditional ELISA and Nano-ELISA using anti-rabbit polyclonal IgG conjugated with AgNPs and for Rep gene by SYBR green real-time PCR. Rep gene detection by SYBR green real-time PCR could detect T. spiralis with 100% sensitivity in the mild infection group at 8 dpi, while in the severe infection group it reached 100% sensitivity at 4 dpi. Nano-ELISA could detect T. spiralis circulating antigen from 4 dpi in both mild and severe infection and reached 100% sensitivity at 8 dpi and 6 dpi in mild and severe infection, respectively. However, traditional ELISA could detect T. spiralis circulating antigen from 6 dpi and reached maximum sensitivity at 15 dpi in the mild infection group, while in the severe infection group detection began at 4 dpi and reached 100% sensitivity at 8 dpi. Nano-ELISA and real time PCR, using Rep gene, are useful tools for the detection of early T. spiralis infection even in its mild infection state.

Trichinellosis in Hospitalized Children and Adults from Western Romania: A 11-Year Retrospective Study

Trichinellosis, a serious and sometimes fatal human disease, is a consequence of consuming raw or improperly cooked meat containing the infective larvae of Trichinella spp. The aim of this observational cohort retrospective study is to compare the epidemiological, laboratory, clinical and therapeutic aspects of trichinellosis in children and adults from Western Romania. We investigated the medical records of patients who were diagnosed with trichinellosis and hospitalized between 17 January 2010 and 31 December 2020. One hundred thirty-three patients were identified according to the electronic databases of infectious disease hospitals, located in four counties from Western Romania. A total of 19 patients (14.28%) were children and 114 patients (85.71%) were adults. In children, the most frequent symptoms were digestive in 78.94%, followed by fever in 57.89%, eyelid or facial edema in 57.89% and myalgia in 52.63% of cases, while adults presented mainly myalgia in 87.71%, followed by fever in 77.19%, digestive symptoms in 68.42% and eyelid or facial edema in 66.66% of cases. The source of infection was pork meat products in the majority of patients (89.47%). Our results revealed a general declining trend in infection rates for both children and adults during the studied period. The vast majority of cases were severe and all required hospitalization. Education of the population along with public health strategies should be improved and maintained to fully prevent trichinellosis in Western Romania.

Trichinella infections in animals and humans of Iran and Turkey

Trichinellosis is considered as a cosmopolitan zoonosis caused by different species of the small nematodes of the genus Trichinella. The present study aimed to provide a broad review for exploring Trichinella sp. infection in humans and animals of Iran and Turkey. Additionally, we aimed to explore bases for trichinellosis prevention and control. Two reports of human trichinellosis following the consumption of meat of wild boar are available in the northern Iran. A large outbreak of trichinellosis and some other sporadic cases are reported mainly as a result of eating wild boar or pork meat from Turkey, where T. britovi is present. Field studies show that Trichinella sp. infections occur in wild carnivores of Iran, particularly the golden jackal (Canis aureus) as the most frequently infected species. T. britovi has been reported to be present elsewhere in Iran in wild mammals, where wild boar is the main source of Trichinella sp. infection. In Turkey, Trichinella spp. has been reported from animals including both domesticated and wild pigs and gray wolf (Canis lupus). However, current data on the distribution of Trichinella taxa are fragmentary in the Anatolian region.

The Prevalence of Trichinella spiralis in Domestic Pigs in China: A Systematic Review and Meta-Analysis

The meta-analysis was performed to assess the prevalence of T. spiralis in domestic pigs in China. The potential studies from seven databases (Pubmed, Web of science, Scopus, Google Scholar, CNKI, Wanfang, CBM) were searched. I², Cochran's Q statistic and the funnel plot and Egger's test were used to assess heterogeneity and publication bias, respectively. In this study, a total of 179 articles were captured in the initially screened. Of these, we finally obtained 39 significant articles (including 43 studies involving in 551,097 pigs) for the final analysis. We calculated using a random-effects model, and we found the overall infection rate was 0.04 (95% CI 0.03-0.06). The highest prevalence region was Guangxi. The funnel plot and Egger's test showed no publication bias in our meta-analysis. In addition, this high heterogeneity index was suggestive of potential variations which could be due to regions, quality scores, detection methods, publication years, or samplings. These results indicated that T. spiralis were still prevalent in some areas in China. This highlights the need for an increased focus on implementing affordable, appropriate control programs to reduce economic losses and T. spiralis infection in domestic pigs in China.

Epidemiology of Trichinella infection in wild boar from Spain and its impact on human health during the period 2006–2019

Trichinellosis is a notifiable zoonotic disease caused by parasitic nematode larvae belonging to the genus Trichinella. Domestic pig and wild boar are important hosts within the natural cycle of T. spiralis, the last one being an animal whose populations have experienced an important growth. Therefore, this paper studies the prevalence of Trichinella infection in wild boar in Spain, as well as its relation with hunting and its impact on public health during the period 2006–2019. For this purpose, different sources of information were consulted and analyzed depending on the autonomous communities of Spain and years. During the fourteen years of study, the number of wild boars hunted and the number of cases of Trichinella infection in them increased (from 172 cases in 2006 to 421 in 2019), although prevalence values remained low as the number of animals analyzed also increased. On the other hand, trichinellosis in humans tended to decrease (from a peak of 107 cases in 2007 to 11 cases in 2019). Nevertheless, the numbers of both wild boars and humans infected with Trichinella in Spain are among the highest in Europe, and this emphasizes the importance of food safety, sanitary controls of game meat and citizen awareness campaigns, which prevent the spread of Trichinella through the human population.

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We analyzed the prevalence of Trichinella infection in wild boar in Spain during the period 2006–2019.

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The number of harvested wild boars increased, just as the number of positive cases of Trichinella infection.

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Spain is one of the European countries with higher value of prevalence of Trichinella infection in wild boar and higher number of human trichinellosis.

The impact of globalization and climate change on Trichinella spp. epidemiology

The main reservoir hosts of nematodes of the genus Trichinella are wild carnivores, although most human infections are caused by the consumption of pork. This group of zoonotic parasites completes the entire natural life cycle within the host organism. However, there is an important phase of the cycle that has only been highlighted in recent years and which concerns the permanence of the infecting larvae in the striated muscles of the host carcasses waiting to be ingested by a new host. To survive in this unique biological niche, Trichinella spp. larvae have developed an anaerobic metabolism for their survival in rotting carcasses and, for some species, a resistance to freezing for months or years in cold regions. Climate changes with increasingly temperatures and reduction of environmental humidity lower the survival time of larvae in host carcasses. In addition, environmental changes affect the biology and ecology of the main host species, reducing their number and age composition due to natural habitat fragmentation caused by increasing human settlements, extensive monocultures, increasing number of food animals, and reduction of trophic chains and biodiversity. All of these factors lead to a reduction in biological and environmental complexity that is the key to the natural host-parasite balance. In conclusion, Trichinella nematodes can be considered as an indicator of a health natural ecosystem.

Epidemiology of trichinellosis in the People's Republic of China during 2009-2020

Trichinellosis is an important meat-borne zoonotic parasitic disease caused by ingesting raw or semi-cooked meat of pigs and other animals infected with Trichinella sp. muscle larvae. Epidemiological data on human and animal Trichinella sp. infection in the People's Republic of China (PRC) during 2009-2020 were analyzed in this review. The results showed that the endemic foci of human trichinellosis are principally localized in southwestern areas, and eight outbreaks covering 479 cases and 2 deaths were reported. Pork is still the primary source of trichinellosis outbreaks. Seven out of 8 outbreaks (87.50%) were caused by ingesting raw or semi-cooked pork. The seroprevalence of swine anti-Trichinella IgG ranged from 0 to 42.11% in 11 provinces/autonomous regions  (P/As), and swine Trichinella infection was detected in six P/A slaughterhouses. The Trichinella-infected pigs came from small backyard farms and outdoor free-ranging pigs in western and southwestern PRC. To prevent trichinellosis, the traditional pig-rearing mode should be improved, more industrialized pig farms should be developed, all pigs should be raised in piggeries under controlled management conditions, and mandatory inspection of Trichinella sp. in slaughtered pigs should be implemented in rural areas of western and southwestern PRC. A One Health approach with participation from governments, public health officials, and medical and veterinary practitioners is vital for controlling zoonotic foodborne trichinellosis.

Vaccines as a Strategy to Control Trichinellosis

Trichinellosis caused by Trichinella spiralis is a worldwide food-borne parasitic zoonosis. Several approaches have been performed to control T. spiralis infection, including veterinary vaccines, which contribute to improving animal health and increasing public health by preventing the transmission of trichinellosis from animals to humans. In the past several decades, many vaccine studies have been performed in effort to control T. spiralis infection by reducing the muscle larvae and adult worms burden. Various candidate antigens, selected from excretory-secretory (ES) products and different functional proteins involved in the process of establishing infection have been investigated in rodent or swine models to explore their protective effect against T. spiralis infection. Moreover, different types of vaccines have been developed to improve the protective effect against T. spiralis infection in rodent or swine models, such as live attenuated vaccines, natural antigen vaccines, recombinant protein vaccines, DNA vaccines, and synthesized epitope vaccines. However, few studies of T. spiralis vaccines have been performed in pigs, and future research should focus on exploring the protective effect of different types of vaccines in swine models. Here, we present an overview of the strategies for the development of effective T. spiralis vaccines and summarize the factors of influencing the effectiveness of vaccines. We also discuss several propositions in improving the effectiveness of vaccines and may provide a route map for future T. spiralis vaccines development.

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.

Analysis of a Trichinellosis Outbreak in Poland after Consumption of Sausage Made of Wild Boar Meat

An outbreak of trichinellosis due to the consumption of sausage made from wild boar meat unexamined for the presence of Trichinella spp. was reported in Poland in December 2020. The outbreak affected eight people. Examination of the sausages made of wild boar meat collected during epidemiological investigation indicated a high level of Trichinella spp. Larvae per gram (>30 lpg) and therefore the threat of an infection in humans after consumption of such product was significant. Over the years, the main source of trichinellosis in Poland has been wild boar meat, and the majority of trichinellosis cases were related to the consumption of traditional raw meat products such as Polish sausage. Taking this into account, there is the need for better education of consumers in the Trichinella spp. endemic regions and among cultures consuming traditional raw meat products.

Absence of Trichinella spp. larvae in carcasses of road-killed wild animals in Paraná state, Brazil

Trichinella spp. are zoonotic parasites that are widely distributed in warm-blooded carnivores and omnivores, including humans. Until the present moment, Brazil has been considered by World Animal Health Organization free from the domestic cycle of trichinellosis, whereas the parasite's sylvatic cycle has the status of infection in limited zones. However, neighboring countries such as Argentina have reports of parasite larvae in the wild fauna. The present study aimed to determine the occurrence of Trichinella spp. in road-killed wild animals in Paraná, Brazil. Biological samples from 71 wild animals-29 Didelphis albiventris, 11 Nasua nasua, ten Cerdocyon thous, seven Dasypus novemcinctus, six Leopardus guttulus, six Sphiggurus spinosus and two Puma concolor-collected from November 2016 to November 2021 were subjected to artificial digestion, following the methodology described in the REGULATION (EC) No. 2075/2005. No Trichinella spp. larvae were detected in the carcasses of the road-killed wild animals. However, considering the wide spectrum of possible reservoirs that could act as a link between the sylvatic and domestic cycles and considering the current Brazilian status of sylvatic trichinellosis in limited zones, frequent monitoring of wild fauna remains necessary.

Survey of Trichinella in American minks (Neovison vison Schreber, 1777) and wild rodents (Muridae and Cricetidae) in Chile

Trichinellosis is a zoonosis with worldwide distribution. Several hosts have been recognized around the world; however, there is a lack of knowledge of the role of feral mammals in Chile in its transmission. Herein, we tested muscle samples from 555 individuals among American minks (Neovison vison Schreber, 1777. n = 100) and several myomorph rodent species (Muridae and Cricetidae. n = 455) from southern Chile by artificial digestion to detect Trichinella larvae and identified the larvae at the species level through molecular analyses. Rodents were captured in agricultural and wild protected areas of several administrative regions (hereafter: region), while minks were captured in agricultural areas of the Los Ríos region. Trichinella spiralis larvae were detected in a synanthropic black rat (0.24%) of the Ñuble region and in seven minks (7%) trapped in agricultural areas of the Los Ríos region. The present results suggest that T. spiralis circulation is restricted to synanthropic rodents and minks living in agricultural areas where the parasite circulates among domesticated pigs. This study represents the first record of T. spiralis in a mustelid mammal in South America, increasing the number of feral species that could participate in the reservoir.

Upconverting phosphor technology-based lateral flow assay for the rapid and sensitive detection of anti-Trichinella spiralis IgG antibodies in pig serum

Background

Trichinella spiralis is a zoonotic food-borne parasite. A disease caused by infection with T. spiralis is called trichinellosis in humans. It is important to investigate the epidemic situation and the surveillance of herds and then prevent infection in humans. Therefore, this study is to develop a rapid and sensitive diagnostic method for on-site test in domestic and wild animals.

Methods

Upconverting phosphor nanoparticles (UCNPs), an excellent optical label, were conjugated with the excretory-secretory (ES) antigens from T. spiralis muscle larvae (ML) or goat anti-rabbit IgG, and a lateral flow (LF) assay based on these probes (UCNPs-ES/goat anti-rabbit IgG) was developed for the rapid and sensitive detection of anti-T. spiralis IgG antibodies in pig serum. The assay is named the UPT-LF-ES assay. In addition, the probes were characterized, and the assay was optimized. A cut-off threshold of the assay was also identified by using 169 known negative pig samples. Performance of the assay to T. spiralis with different infective numbers, cross-reactivity with other parasitic infections, the single-blinded experiment, and coincidence were evaluated with the assay.

Results

The UPT-LF-ES assay was successfully constructed and optimized based on the probes of UCNPs-ES/goat anti-rabbit IgG. In the pigs infected with 100, 1000, and 10,000 ML, positive results were first presented at 35 days post-infection (dpi), 30 dpi, and 25 dpi, respectively. The assay had no cross-reaction with other parasitic infections. A single-blinded experiment indicated that the sensitivity and specificity of the UPT-LF-ES assay were 100% and 100%, respectively, the area under the receiver operating characteristic (ROC) curve was 1.000. In addition, the value detected by the UPT-LF-ES assay was significantly different between positive and negative samples. Moreover, compared with the “gold standard” magnetic stirrer method, the coincidence rate of the UPT-LF-ES assay was 87.27%, and the kappa (K) coefficient was 0.7454, showing a substantial agreement.

Conclusions

The UPT-LF-ES assay is a useful point-of-care test (POCT) with T. spiralis in the detection of pig, which contributes to preventing human trichinellosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04949-2.

Infection, genetics, and evolution of Trichinella: Historical insights and applications to molecular epidemiology

Genetic variation in pathogen populations provides the means to answer questions in disease ecology and transmission, illuminating interactions between genetic traits, environmental exposures, and disease. Such studies elucidate the phylogeny, evolution, transmission and pathogenesis of viruses, bacteria and parasites. Here, we review how such studies have fostered understanding of the biology and epidemiology of zoonotic nematode parasites in the genus Trichinella spp., which impose considerable economic and health burdens by infecting wildlife, livestock, and people. To use such data to define ongoing chains of local transmission and source traceback, researchers first must understand the extent and distribution of genetic variation resident in regional parasite populations. Thus, genetic variability illuminates a population's past as well as its present. Here we review how such data have helped define population dynamics of Trichinella spp. in wild and domesticated hosts, creating opportunities to harness genetic variation in the quest to prevent, track, and contain future outbreaks.

Reprint of: Comparison between Trichinella patagoniensis and Trichinella spiralis infection in BALB/c mice

In Argentina, trichinellosis is an endemic disease acquired mainly through consumption of raw pork infected with nematodes larvae from the Trichinella genus. For years, the only species involved in outbreaks in humans and pig foci in Argentina was Trichinella spiralis. In 2008 the presence of a new Trichinella taxon from a cougar (Puma concolor) was detected and recorded in the province of Rio Negro, Argentina, and the finding was established as a new species in 2012: Trichinella patagoniensis. To the best of our knowledge, there is no information available on the intestinal phase and antibody response in a susceptible host during T. patagoniensis infection. Therefore, our research has been designed to study experimental infection with T. patagoniensis compared to infection with T. spiralis in BALB/c mice. One hundred and twenty eight BALB/c mice were divided into two groups and individuals in each group were infected per os with 500 larvae of T. patagoniensis or 500 larvae of T. spiralis, respectively. After that, they were euthanized on different days. Adult worm recovery from small intestines and artificial digestion of each carcass was performed. Histopathology of small intestines was performed using hematoxylin-eosin staining. Systemic cytokines and antibody kinetics were evaluated. Intestinal adult worm recovery of T. patagoniensis and T. spiralis took place until day 17 and 25, respectively. Systemic IFN-γ, IL-10, and TNF showed significant variations in T. patagoniensis infected mice. Seroconversion was detected in animals as from 15 days post-infection (pi) for both T. patagoniensis and T. spiralis, reaching the highest OD value at 42 days pi. Similar microscopic lesions were observed in the small intestine from mice infected with the same dose of T. spiralis and T. patagoniensis. Our findings contribute new information regarding the intestinal phase and the antibody kinetics of T. patagoniensis in BALB/c mice.

Vaccination with a DNase II recombinant protein against Trichinella spiralis infection in pigs

Trichinellosis caused by Trichinella spiralis (T. spiralis) is an important public health problem. DNase II is an acidic endonuclease that catalyzes the degradation of DNA into oligonucleotides. DNase II-7 has been detected at the adult stage of T. spiralis and has been examined in excretory/secretory products. Previous studies have indicated that the DNase II-7 recombinant protein has a high rate of protection against T. spiralis infection in mice. In the present study, the protective effect of DNase II-7 recombinant protein against T. spiralis infection in Large White pigs was further explored. The humoral and cellular immune responses to the DNase II-7 recombinant protein were evaluated, including the dynamic trends of specific IgG, IgG1, IgG2a and IgM antibodies levels, as well as the levels of Th1 (IFN-γ and IL-2) and Th2 (IL-10 and IL-4) cytokines in serum. Our results showed that a Th1 dominated Th1/Th2 mixed immune response was induced by the DNase II-7 recombinant protein for all the time or a short period after vaccination. And the DNase II-7 recombinant protein induced partial protection against T. spiralis infection in pigs, compared to the control group. Our results showed that the DNase II-7 recombinant protein group displayed a 45.7 % reduction in the muscle larvae burden five weeks after being challenged. This study suggested that DNaseII-7 recombinant protein could be used as a potential candidate vaccine against T. spiralis infection in pigs.

Oral immunization with recombinant Lactobacillus plantarum expressing Nudix hydrolase and 43 kDa proteins confers protection against Trichinella spiralis in BALB/c mice

Trichinellosis is a significant food-borne zoonotic parasitic disease caused by parasite Trichinella. Given the side effects of anti-Trichinella drugs (e.g., Mebendazole) aroused in the course of treatments, an effective vaccine against the parasite is called for. The therapies available to date are in most instances targeting a single stage of Trichinella, resulting in an incomplete protective immunity against the parasite in terms of the complexity of its developmental stages. In this study, a recombinant dual-expression double anchor vector NC8-pLp-TsNd-S-pgsA'-gp43 was constructed carrying two antigen genes from Trichinella spiralis (T. spiralis), encoding the gp43 and T. spiralis Nudix hydrolase (TsNd) proteins which were mainly expressed in muscle larva (ML) and intestinal infective larva stages of the parasite respectively. These two proteins were to be expressed by Lactobacillus plantarum NC8 (L. plantarum NC8) which was designed to express the two anchored peptides, a truncated poly-γ-glutamic acid synthetase A (pgsA') and the surface layer protein of Lactobacillus acidophilus (SlpA), on its surface for attaching expressed foreign proteins. Oral immunization with the above recombinant vaccine induced higher levels of specific serum IgG and mucosal secretory IgA (SIgA) in BALB/c mice. In addition, cytokines, interferon-γ (IFN- γ), interleukin-4 (IL-4) and IL-17 released by lymphocytes, and CD4+ levels displayed on the surfaces of splenic and mesenteric lymph cells were significantly enhanced by the vaccination. Moreover, after larval challenges, a 75.67 % reduction of adult worms (AW) at 7 days post-infection (dpi) and 57.14 % reduction of ML at 42 dpi were observed in mice immunized with the recombinant vaccine. Furthermore, this oral vaccination reduced the counts of encysted larvae presented in tongue and masseter muscles after infected with T. spiralis in mice. The overall results demonstrated that the recombinant vaccine developed in this study could induce specific humoral, mucosal, and cellular immune responses, and provides protections against different stages (adult worms and muscle larva) of T. spiralis infections in BALB/c mice, which could make it a promising oral vaccine candidate against trichinellosis.

Seroprevalence of Theileria equi, Babesia caballi, and Trichinella spp. infections in horses and donkeys from Nigeria, West Africa

The protozoan parasites Theileria equi and Babesia caballi, transmitted by ticks, cause equine piroplasmosis, the most prevalent tick-borne disease in equids. Trichinellosis is a worldwide food-borne zoonosis caused by helminth Trichinella spp. that can lead to serious disease in humans, with fatal outcome. Although the infection is rare in horses, it deserves attention due to the increasing use of horse meat as a source of protein for humans. Horse trichinellosis is caused by several Trichinella species, most commonly by T. spiralis. The aim of the study was to determine the prevalence of antibodies to T. equi, B. caballi and Trichinella spp. in equids from three states of Northern Nigeria. Serum samples were collected from 139 clinically healthy animals, comprising 115 horses and 24 donkeys. Antibodies to T. equi and B. caballi were detected in serum by competitive-inhibition enzyme-linked immunosorbent assay (cELISA) and antibodies to Trichinella spp. by ELISA. Antibodies to T. equi were detected in 34% of equids (41% horses and 0% donkeys), antibodies to B. caballi in 9% of equids (8% horses and 13% donkeys), and antibodies to Trichinella spp. in 4% of equids (4% horses and 0% donkeys). There was co-infection of T. equi and B. caballi in 1% of horses and co-infection of T. equi and Trichinella spp. in 2.6% of horses. This is the first report on seroprevalence of Trichinella spp. in equids from Northern Nigeria.

A Bead-Based Assay for the Detection of Antibodies against Trichinella spp. Infection in Humans

Human trichinellosis can be diagnosed by a combination of medical history, clinical presentation, and laboratory findings, and through detection of anti-Trichinella IgG in the patient's sera. ELISA using excretory-secretory (E/S) antigens of Trichinella spiralis larvae is currently the most used assay to detect Trichinella spp. antibodies. Bead-based assay can detect antibodies to multiple antigens concurrently; the ability to detect antibody to T. spiralis using a bead assay could be useful for diagnosis and surveillance. We developed and evaluated a bead assay to detect and quantify total IgG or IgG4 Trichinella spp. antibodies in human serum using T. spiralis E/S antigens. The sensitivity and specificity of the assay were determined using serum from 110 subjects with a confirmed diagnosis of trichinellosis, 140 subjects with confirmed infections with other tissue-dwelling parasites, 98 human serum samples from residents of the United States with no known history of parasitic infection, and nine human serum samples from residents of Egypt with negative microscopy for intestinal parasites. Sensitivity and specificity were 93.6% and 94.3% for total IgG and 89.2% and 99.2% for IgG4, respectively. Twelve percent of sera from patients with confirmed schistosomiasis reacted with the IgG Trichinella bead assay, as did 11% of sera from patients with neurocysticercosis. The Trichinella spp. bead assay to detect IgG total antibody responses has a similar performance as the Trichinella E/S ELISA. The Trichinella spp. bead assay shows promise as a method to detect trichinellosis with a possibility to be used in multiplex applications.

Time-resolved transcriptional profiling of Trichinella-infected murine myocytes helps to elucidate host-pathogen interactions in the muscle stage

Background

Parasites of the genus Trichinella are the pathogenic agents of trichinellosis, which is a widespread and severe foodborne parasitic disease. Trichinella spiralis resides primarily in mammalian skeletal muscle cells. After invading the cells of the host organism, T. spiralis must elude or invalidate the host’s innate and adaptive immune responses to survive. It is necessary to characterize the pathogenesis of trichinellosis to help to prevent the occurrence and further progression of this disease. The aims of this study were to elucidate the mechanisms of nurse cell formation, pathogenesis and immune evasion of T. spiralis, to provide valuable information for further research investigating the basic cell biology of Trichinella-infected muscle cells and the interaction between T. spiralis and its host.

Methods

We performed transcriptome profiling by RNA sequencing to identify global changes at 1, 3, 7, 10 and 15 days post-infection (dpi) in gene expression in the diaphragm after the parasite entered and persisted within the murine myocytes; the mice were infected by intravenous injection of newborn larvae. Gene expression analysis was based on the alignment results. Differentially expressed genes (DEGs) were identified based on their expression levels in various samples, and functional annotation and enrichment analysis were performed.

Results

The most extensive and dynamic gene expression responses in host diaphragms were observed during early infection (1 dpi). The number of DEGs and genes annotated in the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology databases decreased significantly in the infected mice compared to the uninfected mice at 3 and 7 dpi, suddenly increased sharply at 10 dpi, and then decreased to a lower level at 15 dpi, similar to that observed at 3 and 7 dpi. The massive initial reaction of the murine muscle cells to Trichinella infection steadied in the later stages of infection, with little additional changes detected for the remaining duration of the studied process. Although there were hundreds of DEGs at each time point, only 11 genes were consistently up- or downregulated at all 5 time points.

Conclusions

The gene expression patterns identified in this study can be employed to characterize the coordinated response of T. spiralis-infected myocytes in a time-resolved manner. This comprehensive dataset presents a distinct and sensitive picture of the interaction between host and parasite during intracellular infection, which can help to elucidate how pathogens evade host defenses and coordinate the biological functions of host cells to survive in the mammalian environment.

Early Detection of Trichinella spiralis DNA in Rat Feces Based on Tracing Phosphate Ions Generated During Loop-Mediated Isothermal Amplification

Early diagnosis of trichinellosis is still difficult because of the lack of specific symptoms and limited window for serological detection. Here we established an assay based on tracing phosphate ions generated during loop-mediated isothermal amplification (LAMP) to detect Trichinella spiralis DNA in rat feces during its early stage of infection. By targeting a 1.6-kb repetitive element of Tri. spiralis, the assay was able to detect Tri. spiralis DNA in the feces of all infected rats as early as 1 day postinfection (dpi). The positive detection lasted to 7 dpi in the rats infected with 250 muscle larvae, and 21 dpi in the rats infected with 5,000 larvae. The assay was highly sensitive, and could detect 1.7 femtograms (fg) of Tri. spiralis DNA with high specificity, and with no cross reactivity with the DNA from Anisakis pegreffii, Gnathostoma spinigerum, Angiostrongylus cantonensis, Enterobius vermicularis, Schistosoma japonicum, and Trypanosoma evansi. Our present study provided a reliable technique for the early diagnosis of trichinellosis with the advantages of simplicity and speed, as well as high sensitivity and specificity.

Effects of Trichinella spiralis and its excretory/secretory products on autophagy of host muscle cells in vivo and in vitro

Trichinella spiralis (T. spiralis) is a widely distributed pathogenic microorganism that causes trichinellosis, a disease that has the potential of causing severe harm to their host. Numerous studies have demonstrated that autophagy can be triggered by microbial infection, such as bacteria, viruses, protozoa, and parasitic helminths. However, it’s still unknown whether autophagy can facilitate host resistance to T. spiralis infection. The present study examined the role of autophagy in striated muscle cell transformation following infection with T. spiralis in BALB/c mice. Transmission electron microscopy (TEM) was used to detect the production of the host diaphragm autophagosome after T. spiralis infection, and changes in the protein and transcriptional levels of autophagic marker proteins were also detected. The significance of autophagy in T. spiralis infection, namely inhibition of T. spiralis growth, was preliminarily evaluated by conducting in vivo experiments using autophagy inhibitors. Besides, we studied the effect of excretory-secretory products (ES) of T. spiralis on autophagy of C2C12 myoblasts. The changes in protein and gene expression levels in autophagy-related pathways in vitro and in vivo were measured as further evidence. The results showed that T. spiralis infection induced autophagy in the host muscle cells. Meanwhile, ES inhibited autophagy of myoblasts in vitro, but this did not affect the cell viability. The upregulation and downregulation of autophagy-related factors in skeletal muscle cells may indicate an adaptive mechanism providing a comfortable niche for the parasite.

Autophagy, a intracellular degradation system, is a kind of unique phenomenon in eukaryotic cells. The commonly referred autophagy is the process of forming autophagosomes by wrapping the cytoplasmic components with double-membrane structure, and then fusing with lysosomes to degrade the internal substances of the cell. Autophagy can be induced by various pathogens including parasites. When the body is infected with intracellular parasites, the host cell can remove the parasites by autophagy. However, parasites have also evolved defence mechanisms that use autophagy in host cells to promote growth. These can be seen in some intracellular parasitic infections such as Toxoplasma gondii and Plasmodium. Although the role of autophagy in other parasitic infections has been revealed, it remains unclear whether autophagy is involved in the invasion process by Trichinella. We investigated the role of Trichinella infection on host muscle cells autophagy and the effect of autophagosome formation on the survival of T. spiralis. Understanding the role of autophagy in the interaction between parasitic infection and host cell is of great significance for the prevention and treatment of Trichinella infection and the development of anti-parasite drugs.

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.

Illegal Wildlife Trade: A Gateway to Zoonotic Infectious Diseases

The illegal wildlife trade (IWT) is a criminal practice bringing several ecological and public health consequences, such as the spreading of zoonotic pathogens and/or the introduction of exotic species of animals into new geographical areas. Here, we discuss potential risks of IWT on the spreading and emergence of zoonotic pathogens.

The immune protection induced by a serine protease from the Trichinella spiralis adult administered as DNA and protein vaccine

Trichinellosis is caused by Trichinella spiralis (T. spiralis), which is an important public health problem. In this study, a gene encoding a serine protease from adult worms of T. spiralis (Ts-Adsp) was screened from a cDNA library of adult worms and was cloned and expressed in a prokaryotic expression system. The gene Ts-Adsp was subcloned into the eukaryotic expression vector pcDNA3.1(+), which was named pcDNA3.1(+)-Adsp. Previous studies have found that recombinant Ts-Adsp protein (rTs-Adsp) can elicit partial protection against T. spiralis infection in mice. Our aim was to explore the protective effect of combining a DNA vaccine with the rTs-Adsp protein against T. spiralis. One week after the last vaccination, the serum and spleen were obtained. The levels of IgG, IgG1 and IgG2a and cytokine production in serum and spleen cells were analyzed. The results showed that the levels of humoral and cell-mediated immune responses increased in the pcDNA3.1(+)-Adsp/rTs-Adsp group mice and demonstrated that a Th1/Th2 mixed immune response was induced by pcDNA3.1(+)-Adsp/rTs-Adsp after vaccination. Moreover, mice vaccinated with pcDNA3.1(+)-Adsp/rTs-Adsp displayed a 69.50% reduction in muscle larvae burden. This study suggested that mixed immunity could improve the muscle larvae reduction rate.

Comparison between Trichinella patagoniensis and Trichinella spiralis infection in BALB/c mice

In Argentina, trichinellosis is an endemic disease acquired mainly through consumption of raw pork infected with nematodes larvae from the Trichinella genus. For years, the only species involved in outbreaks in humans and pig foci in Argentina was Trichinella spiralis. In 2008 the presence of a new Trichinella taxon from a cougar (Puma concolor) was detected and recorded in the province of Rio Negro, Argentina, and the finding was established as a new species in 2012: Trichinella patagoniensis. To the best of our knowledge, there is no information available on the intestinal phase and antibody response in a susceptible host during T. patagoniensis infection. Therefore, our research has been designed to study experimental infection with T. patagoniensis compared to infection with T. spiralis in BALB/c mice. One hundred and twenty eight BALB/c mice were divided into two groups and individuals in each group were infected per os with 500 larvae of T. patagoniensis or 500 larvae of T. spiralis, respectively. After that, they were euthanized on different days. Adult worm recovery from small intestines and artificial digestion of each carcass was performed. Histopathology of small intestines was performed using hematoxylin-eosin staining. Systemic cytokines and antibody kinetics were evaluated. Intestinal adult worm recovery of T. patagoniensis and T. spiralis took place until day 17 and 25, respectively. Systemic IFN-γ, IL-10, and TNF showed significant variations in T. patagoniensis infected mice. Seroconversion was detected in animals as from 15 days post-infection (pi) for both T. patagoniensis and T. spiralis, reaching the highest OD value at 42 days pi. Similar microscopic lesions were observed in the small intestine from mice infected with the same dose of T. spiralis and T. patagoniensis. Our findings contribute new information regarding the intestinal phase and the antibody kinetics of T. patagoniensis in BALB/c mice.

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.

Immunization with a Recombinant Protein of Trichinella britovi 14-3-3 Triggers an Immune Response but No Protection in Mice

14-3-3 proteins are present in all eukaryotic organisms and are ubiquitously expressed in a broad range of tissues and cellular compartments. They are regulatory adapter proteins that play key roles in a variety of signaling pathways, and have been proposed as suitable targets for the control and detection of certain parasites. Trichinella britovi is a widely-distributed parasitic nematode, transmitted through ingestion of meat products containing invasive larvae. The present study describes the cloning and expression of Tb14-3-3, and investigates the immunological and protective potential of the recombinant protein. Immunization of mice with rTb14-3-3 triggered an IgG response, and significant differences, in the profiles of secreted cytokines observed in vitro, between experimental groups. Nonetheless, neither specific antibodies, nor increased secretion of IFNγ, IL-4, and IL-10 cytokines, conferred greater protection against infection. No reduction in larval burden was observed during recovery at 48 dpi. Additionally, rTb14-3-3 was not recognized by sera from the infected control mice, except for one, suggesting some mismatch between native and recombinant Tb14-3-3 antigenic sites. Therefore, before 14-3-3 can be considered a potential tool for Trichinella detection and vaccination, more research regarding its target proteins, and actual specific function, is needed.

Trichinella species and genotypes

Trichinella spiralis has historically been deemed "the pig parasite" owing to its initial classification within a monospecific genus. However, in recent years, the genus has expanded to include 10 distinct species and at least 3 different genotypes whose taxonomic status remains unstipulated. In contrast to T. spiralis, however, most of these sylvatic species and genotypes do not infect pigs well. Inasmuch as morphological characters cannot be used to define species within this genus, earlier classifications were based upon host and geographical ranges, biological characters, and the presence or absence of a collagen capsule that surrounds the muscle stage larvae. Later, isoenzymes, DNA gel fragmentation patterns and DNA probes were used to help in identification and classification. Today, amidst the "-omics" revolution, new molecular and biochemical-based methodologies have improved detection, differentiation and characterization at all levels including worm populations. These efforts have discernably expanded immunological, epidemiological, and genetic studies resulting in better hypotheses on the evolution of the genus, and on global events, transmission cycles, host associations, and biogeographical histories that contributed to its cosmopolitan distribution. Reviews of this sort are best begun with a background on the genus; however, efforts will divert to the most recent knowledge available on the taxonomy, phylogeny, epidemiology and biochemistry that define this genus in the 21st century.

Use of Veterinary Vaccines for Livestock as a Strategy to Control Foodborne Parasitic Diseases

Foodborne diseases (FBDs) are a major concern worldwide since they are associated with high mortality and morbidity in the human population. Among the causative agents of FBDs, Taenia solium, Echinococcus granulosus, Toxoplasma gondii, Cryptosporidium spp., and Trichinella spiralis are listed in the top global risk ranking of foodborne parasites. One common feature between them is that they affect domestic livestock, encompassing an enormous risk to global food production and human health from farm to fork, infecting animals, and people either directly or indirectly. Several approaches have been employed to control FBDs caused by parasites, including veterinary vaccines for livestock. Veterinary vaccines against foodborne parasites not only improve the animal health by controlling animal infections but also contribute to increase public health by controlling an important source of FBDs. In the present review, we discuss the advances in the development of veterinary vaccines for domestic livestock as a strategy to control foodborne parasitic diseases.

Label-free serum detection of Trichinella spiralis using surface-enhanced Raman spectroscopy combined with multivariate analysis

Based on blood serum surface-enhanced Raman spectroscopy (SERS) analysis, this paper proposed a simple and unlabeled non-invasive serum detection for T. spiralis infection. Serum samples were collected and analyzed from 40 rats at 0 days post infection (dpi) (normal rats), 19 uninfected rats, and 16 rats infected with T. spiralis at 28 dpi, using SERS measurements. Multivariate statistical techniques, such as linear discriminant analysis (LDA) and principal components analysis (PCA), were used to analyze and identify the obtained blood serum SERS spectra. The diagnosis algorithms, based on PCA-LDA, achieved a diagnostic sensitivity of 87.5%, a specificity of 94.7%, and an accuracy of 91.4% for separating the samples infected with T. spiralis from the control samples. This exploratory study demonstrated that colloidal Ag NPs-based SERS serum analysis technique combined with PCA-LDA has a great potential in improving the detection of T. spiralis infection and onsite screening.

How globalization and climate change could affect foodborne parasites

Foodborne parasites, most of which are zoonotic, represent an important human health hazard. These pathogens which include both protozoa (e.g., Cryptosporidium spp., Cyclospora cayetanensis, Toxoplasma gondii) and helminths (e.g., liver and intestinal flukes, Fasciola spp., Paragonimus spp., Echinococcus spp., Taenia spp., Angiostrongylus spp., Anisakis spp., Ascaris spp., Capillaria spp., Toxocara spp., Trichinella spp., Trichostrongylus spp.), have accompanied the human species since its origin and their spread has often increased due to their behavior. Since both domesticated and wild animals play an important role as reservoirs of these pathogens the increase/decrease of their biomasses, migration, and passive introduction by humans can change their epidemiological patterns. It follows that globalization and climate change will have a tremendous impact on these pathogens modifying their epidemiological patterns and ecosystems due to the changes of biotic and abiotic parameters. The consequences of these changes on foodborne parasites cannot be foreseen as a whole due to their complexity, but it is important that biologists, epidemiologists, physicians and veterinarians evaluate/address the problem within a one health approach. This opinion, based on the author's experience of over 40 years in the parasitology field, takes into consideration the direct and indirect effects on the transmission of foodborne parasites to humans.

Synthetic gene as target to assess the sensitivity of PCR to detect Trichinella spp. larvae in meat from a non-endemic region

Trichinellosis is a zoonotic disease exotic in Brazil but commonly found worldwide including South American countries like Argentina. International trading of swine meat needs an official Trichinella-free diagnosis commonly carried out by pepsin-HCl digestion of diaphragm tissue fragments followed by microscopic examination for the presence or absence of Trichinella larvae. The easiness of this diagnostic method allows it to be performed at slaughtering plants but, in contrast, it lacks sensitivity and does not allow species differentiation, which is fundamental for determining geographical and species distribution of different genotypes. In our study, we aimed to evaluate a highly sensitive diagnostic method based on the polymerase chain reaction (PCR) that would allow us to detect and classify different species of Trichinella. Thus, we designed a synthetic gene and selected five sets of primers targeting specific regions of the Trichinella genome. The synthetic gene was cloned into a plasmid and then used to optimize PCR conditions. Using our PCR, we were able to detect 0.001 pg of the synthetic gene, which corresponded to 0.01 larvae. Then, we collected 175 samples of Suidae (domestic and wild boars) diaphragm fragments that were pooled into groups, digested with pepsin-HCl, and had the DNA extracted for analysis by PCR. The clinical samples evaluated were negative by PCR. Our results indicate that the PCR-based method might be a useful diagnostic method complementary to the pepsin-HCl digestion method currently in use, mostly in non-endemic areas.

Retrospective analysis of hospital discharge records for cases of trichinellosis does not allow evaluation of disease burden in Italy

Human trichinellosis is a disease caused by nematode worms of the genus Trichinella. In Italy, as well as in most other European countries, notification of Trichinella infections in humans is mandatory; however, no information is available on the number of cases occurring annually. The aim of the present study was to retrospectively evaluate the burden of trichinellosis in Italy from 2005 to 2016. Hospital discharge records (HDRs) showing the code for trichinellosis (124) were registered and screened. Results were then compared with yearly reports issued by the Italian National Reference Laboratory for Trichinella (NRLT), with reports from the European Centre for Disease Prevention and Control (ECDC), and with literature data. A total of 102 HDRs revealed that the 124 code was erroneously reported in 72 (70.6%) records. Out of the 30 (29.4%) records with a correct diagnosis of trichinellosis, nine cases were reported by HDRs only, 21 cases were documented by both HDRs and the NRLT, whereas the NRLT documented 100 additional cases. In the studied period, the average yearly incidence was 0.01 cases per 100,000 inhabitants. This study highlights the limitations of using HDRs to obtain a clear picture of the prevalence and incidence of trichinellosis in Italy. These findings demonstrate the need to intensify the surveillance system for trichinellosis through the development of an Italian registry. This would allow the identification of patients with severe infections and pauci-symptomatic patients, and would avoid the need for clinical analyses and unnecessary treatments, reducing the resulting economic burden on the Italian National Health Service.

Sarcocystis bertrami in skeletal muscles of donkeys (Equus africanus asinus) from Southern Italy

Among the protozoa of the genus Sarcocystis (Apicomplexa; Sarcocystidae), Sarcocystis bertrami (syn. Sarcocystis fayeri) is an obligate intracellular parasite of donkeys and horses with worldwide distribution. Here, we report the detection of S. bertrami in naturally infected donkeys from southern Italy and describe their structure by light microscopy (LM) and transmission electron microscopy (TEM). Protozoal cysts were detected both morphologically and molecularly in skeletal muscles of 28.57% (40/140) donkeys. Mature cysts of S. bertrami were found in skeletal muscle measuring 31-102 μm long and 19-83 μm wide with radially striated thick cyst wall. The high prevalence of infected donkeys suggests that dogs, the definitive hosts of S. bertrami, are contaminating environment with environmentally resistant sporocysts. Considering the increased consumption of raw donkey meat results also suggest a potential risk for human health.

Transboundary spread of pig diseases: the role of international trade and travel

As globalization increases the interconnectedness between nations, economies, and industries, the introduction of diseases will continue to remain a prominent threat to the livestock sector and the trade of animals and animal products, as well as the livelihoods of farmers, food security and public health. The global pig sector, with its size and dichotomy between production type and biosecurity level, is particularly vulnerable to the transmission of transboundary animal diseases such as African and classical swine fever, foot and mouth disease, or porcine reproductive and respiratory syndrome. All of the above pose a constant threat to swine health, mainly as a result of both formal and informal international trade.Inspired in the risk assessment methodology, this paper classifies and provides an overview of the different pig disease introduction and exposure pathways, illustrated with abundant examples. Introduction pathways are classified as formal international trade (by product), informal international trade (by product), and spread through fomites. Formal trade of pigs and pork products is regulated by legislation and measures protecting animal populations from exotic diseases. Much more difficult to control is the transboundary swine disease transmission originating through informal trade, which entails illegal smuggling, but also the informal cross-border transfer of animals and products for personal use or within informal market chains. Meat products are most commonly mentioned, although fomites have also played a role in some cases, with live pigs, being more difficult to smuggle playing a role less frequently. The main exposure pathways are also described with the oral route playing a prominent role.Risk assessments can aid in the identification of pathways of pathogen introduction and exposure. However, quantitative information on informal disease introduction pathways remains very scarce and often incomplete, making it difficult to estimate the actual magnitudes of risks. Nevertheless, this knowledge is deemed essential to set up risk based awareness, prevention and surveillance programs that correspond to reality.

Rapid and Visual Detection of Trichinella Spp. Using a Lateral Flow Strip-Based Recombinase Polymerase Amplification (LF-RPA) Assay

Trichinella spp., are amongst the most widespread parasitic nematodes, primarily live in the muscles of a wide range of vertebrate animals and humans. Human infection occurs by ingestion of raw or undercooked meat containing Trichinella larvae. Accurate diagnosis of Trichinella spp. infection in domestic animals is crucial for the effective prevention and control of human trichinellosis. In the present study, a simple, rapid and accurate diagnostic assay was developed combining recombinase polymerase amplification and a lateral flow strip (LF-RPA) to detect Trichinella spp. infection. The LF-RPA assay targets Trichinella spp. mitochondrial small-subunit ribosomal RNA (rrnS) gene and can detect as low as 100 fg DNA of Trichinella strains, which was approximately 10 times more sensitive than a conventional PCR assay. The LF-RPA assay can be performed within 10–25 min, at a wide range of temperatures (25–45°C) and showed no cross-reactivity with DNA of other parasites and related host species of Trichinella. The performance of the LF-RPA assay in the presence of high concentration of PCR inhibitor was better than that of a conventional PCR assay. Results obtained by LF-RPA assay for the detection of experimentally infected mice were comparable to the results obtained by using a conventional PCR, achieving 100% specificity and high sensitivity. These results present the developed LF-RPA assay as a new simple, specific, sensitive, rapid and convenient method for the detection of Trichinella infection in domestic animals.

Differentiation of Trichinella species (Trichinella spiralis/Trichinella britovi versus Trichinella pseudospiralis) using western blot

BACKGROUND

Trichinellosis is a meat-borne zoonotic disease caused by parasites of the genus Trichinella. To date, 12 taxa have been described. The identification of Trichinella species is crucial in order to identify the possible source of infection, the geographical origin of the parasite and to assess risk of infection for domestic pigs and humans. Specific identification of the etiological agent is not always feasible using direct methods since the source of infection can be untraceable. The aim of this study was to develop a diagnostic tool to infer the causative Trichinella species using western blot patterns of sera derived from infected animal and human hosts.

METHODS

Sera from mice experimentally infected with Trichinella spiralis, Trichinella britovi, Trichinella pseudospiralis and Trichinella papuae were tested by western blot using homologous and heterologous crude worm extracts (CWE) and a highly sensitive detection system based on chemiluminescence. In addition, sera from pigs experimentally infected with T. spiralis, T. britovi and T. pseudospiralis and from patients with confirmed T. spiralis, T. britovi and T. pseudospiralis infections, were also included.

RESULTS

Sera from mice infected with one Trichinella species reacted with CWE proteins from all four investigated species. Likewise, sera derived from pigs and humans infected with one Trichinella species reacted with CWE proteins from all the three investigated species. Using T. spiralis CWE, sera from T. pseudospiralis-infected hosts yielded a characteristic pattern of reactivity using Wb, which differed to that produced by T. spiralis/T. britovi- or T. papuae-infected host sera.

CONCLUSIONS

The present study suggests that western blot using T. spiralis CWE may be a useful tool to distinguish Trichinella infections caused by T. pseudospiralis from those caused by T. spiralis or T. britovi. This method may support epidemiological investigations, particularly when the source of infection is not traceable.

Wild Boar: A Reservoir of Foodborne Zoonoses

Wild boar populations around the world have increased dramatically over past decades. Climate change, generating milder winters with less snow, may affect their spread into northern regions. Wild boars can serve as reservoirs for a number of bacteria, viruses, and parasites, which are transmissible to humans and domestic animals through direct interaction with wild boars, through contaminated food or indirectly through contaminated environment. Disease transmission between wild boars, domestic animals, and humans is an increasing threat to human and animal health, especially in areas with high wild boar densities. This article reviews important foodborne zoonoses, including bacterial diseases (brucellosis, salmonellosis, tuberculosis, and yersiniosis), parasitic diseases (toxoplasmosis and trichinellosis), and the viral hepatitis E. The focus is on the prevalence of these diseases and the causative microbes in wild boars. The role of wild boars in transmitting these pathogens to humans and livestock is also briefly discussed.

Molecular cloning of enolase from Trichinella spiralis and the protective immunity in mice

Trichinella spiralis, the main pathogen of trichinosis, infects a wide range of mammalian hosts and is one of the most widespread parasites worldwide. For parasites, glycolysis is the most important way to generate energy. Previous studies showed that some enzymes involved in the glycolytic pathway play roles in regulation the host immunity. In this paper, enolase from T. spiralis was cloned and the protective potentials were studied. One hundred and sixty ICR mice were divided into four groups and vaccinated with recombinant enolase (pET-ENO), eukaryotic recombinant plasmid encoding enolase (pVAX1-ENO) and negative controls (pVAXl and PBS), respectively. Two weeks after the second immunization, each mouse was challenged orally with 200 muscle larvae (MLs) of T. spiralis. Results showed that mice vaccinated with pET-ENO and pVAX1-ENO induced specific antibodies of IgG, IgA, IgM, but no IgE. Subclasses of IgG antibodies showed that mice immunized with recombinant protein and recombinant plasmids induced a Th1/Th2 immune response. Concentrations of serum cytokines were detected and showed significant increase of IFN-γ, IL-4 and TGFβ1, while IL-17 in each group was not significantly different. Flow cytometric analysis showed significant increase of CD4+ and CD8+ T lymphocytes in the groups immunized with recombinant protein and recombinant plasmids. Challenge infection demonstrated that immunized groups had a reduced number of worm burdens. The reductions of larvae per gram muscle (LPG) in pET-ENO and pVAX1-ENO group were 17.7% and 15.8% when compared with PBS control.

Vaccines against Trichinella spiralis: Progress, challenges and future prospects

Trichinella spiralis, the causative agent of trichinellosis, is able to infect a wide range of carnivores and omnivores including human beings. In the past 30 years, a mass of vaccination efforts has been performed to control T. spiralis infection with the purpose of reduction in worm fecundity or decrease in muscle larval and adult burdens. Here, we summarize the development of veterinary vaccines against T. spiralis infection. During recent years, increasing numbers of new vaccine candidates have been developed on the protective immunity against T. spiralis infection in murine model. The vaccine candidates were not only selected from excretory-secretory (ES) antigens, but also from the recombinant functional proteins, such as proteases and some other antigens participated in T. spiralis intracellular processes. However, immunization with a single antigen generally revealed lower protective effects against T. spiralis infection in mice compared to that with the inactivated whole worms or crude extraction and ES productions. Future study of T. spiralis vaccines should focus on evaluation of the protective efficacy of antigens and/or ligands delivered by nanoparticles that could elicit Th2-type immune response on experimental pigs.