Trichinella infection in wild animals from endemic regions of Argentina

Molecular based confirmation of puma meat sausages implicated in trichinellosis outbreaks in Argentina

Trichinellosis is a zoonotic disease caused by Trichinella, with the main source of infection being the consumption of pork and pork-derived products. However, it can also be acquired from eating the meat from wild animals targeted for sport hunting. The objectives of this study were: 1) to develop and implement a molecular method for the identification of Sus scrofa (pig and wild boar) and Puma concolor (Puma) meat in sausages eaten raw, which were linked to trichinellosis outbreaks occurring in Córdoba, Buenos Aires and La Pampa provinces, Argentina, in 2010, 2021, and 2022, respectively; and 2) to identify the Trichinella species present in the food. Specific primers were designed for PCR amplification and nucleotide sequencing of a region of the mitochondrial cytochrome b gene from both host species. Samples from the mentioned outbreaks were analysed, and the molecular identification of Trichinella spp. larvae was also performed. Results of the species identification system revealed that sausages from Córdoba and Buenos Aires had a mixed composition of pork and puma meat, while those from La Pampa contained puma meat only. Trichinella spiralis was implicated in all three outbreaks. The species identification system developed and implemented in this study revealed two host species of Trichinella related to human cases, and alerts about the risk of zoonotic transmission to humans through infected puma meat.

Contribution to host diversity, genetic diversion, and epidemiology of Trichinella pseudospiralis in Slovakia, central Europe

Trichinella pseudospiralis belongs to the non-encapsulated clade of the genus and its epidemiology is influenced by various biotic and abiotic factors. The role of different animal species in the spread and epidemiology of the parasite is still not well understood and further research is needed in the areas where its occurrence has been recorded. In Slovakia, T. pseudospiralis was first documented in 2004 on a poorly maintained industrial pig farm where pigs, rats, and a domestic cat were found to be infected. In the following years, its occurrence was confirmed in foxes, wild boars, and three species of birds of prey. The objective of the present study was to investigate different micromammal and carnivore host species inhabiting the Tatra National Park in the north of Slovakia for the presence of Trichinella parasites. From 2018-2023, 715 small mammals belonging to 19 species and 92 muscle samples from 12 carnivorous species were individually examined for the presence of Trichinella muscle larvae using the artificial digestion method. The research brought new host records and completed the list of sylvatic hosts for T. pseudospiralis in Slovakia - the yellow-necked mouse (Apodemus flavicollis) and raccoon dog (Nyctereutes procyonoides) together with results of the genetic structure study conducted on a fragment of the 28S gene in T. pseudospiralis.

Invasive wild boar (Sus scrofa) as a functional reservoir for the dynamics of Trichinella in the Patagonia region

Trichinellosis is a zoonotic disease that has been studied mainly in domestic pigs (Sus scrofa domesticus). The cycle involves infection in domestic and wild fauna, which fulfill complex ecological roles, where Trichinella spiralis is reported in wild boar (Sus scrofa). The objective of this study was to determine the prevalence of trichinellosis in wild boar and evaluate the distance of positive animals to the nearest urbanization areas in Argentina Patagonia. Necropsies were carried out on wild boar hunted in the Nahuel Huapi and Lanín National Parks and surrounding areas. Skeletal muscle samples were collected from 1,694 wild boar and artificial digestion was performed on all samples. Trichinella spp. were found in 96 (5.8%) wild boar (0.2 to 424 Larvae/g). Parasitism in wild boar depends on the distribution of the population in natural and urban areas. Infected wild boar were found near peri-urban areas, demonstrating the importance of routine epidemiological surveillance and sanitary measures in and around cities. More research is needed to identify the Trichinella species that infect wild animals. We recommend the application of active and passive epidemiological surveillance in South America on exotic and native fauna that are hunted and consumed by humans.

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 spiralis Infecting Wild Boars in West, Southwest, and Northwest of Romania: Evidence of an Underrated Risk

The species of the genus Trichinella are etiological agents distributed all over the world and are able to infect mammals, birds, and reptiles. Trichinella spiralis is the species most adapted to domestic and wild pigs and is also the most important etiological agent of trichinellosis. The wild boar (Sus scrofa) is a nocturnal omnivorous mammal belonging to the Suidae family. S. scrofa has a great appetite and its diet includes a variety of small prey such as mice, rats, and other rodents, as well as carcasses of larger animals. The aim of this study was the identification and the molecular characterization of Trichinella larvae isolated from the muscle tissue of S. scrofa specimens collected in different counties of Romania. The muscle samples were examined by artificial digestion and the larvae identified at the species level by multiplex PCR. T. spiralis, a species that is able to infect a considerable number of different host species including humans, was identified. In Romania, S. scrofa is an important reservoir species for T. spiralis and plays an important role in linking the domestic and the wild cycle of Trichinella, with serious repercussions for human health.

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.

Eleven Years of Health Monitoring in Wild Boars (Sus scrofa) in the Emilia-Romagna Region (Italy)

In recent years, the growth of wild ungulates has increased the focus on their health monitoring. In particular, the health status of wild boars is relevant for the economic impact on the pig industry. The Emilia-Romagna region activated a wildlife monitoring plan to better evaluate the health status of the wild boar population. Between 2011 and 2021, samples of found dead and hunted wild boar have been examined for trichinellosis, tuberculosis, brucellosis, african swine fever, classical swine fever, Aujeszky's disease, swine vesicular disease, and swine influenza A. Trichinella britovi was identified in 0.001% of the examined wild boars; neither M. bovis nor M. tuberculosis were found in M. tuberculosis complex positive samples; 2.3% were positive for Brucella suis; 29.4% of the sera were positive for Aujeszky's disease virus; and 0.9% of the samples were positive for swine influenza A virus. With an uncertain population estimate, the number of animals tested, the number of positives, and the sampling method do not allow us to make many inferences but suggest the need to implement and strengthen the existing surveillance activity, as it seems to be the only viable alternative for safeguarding animal and human health.

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: Knockdown of gamma interferon inducible lysosomal thiol reductase (GILT) results in the reduction of worm burden

Trichinella spiralis is mammalian skeletal muscles parasite which may cause trichinellosis in animals and humans. Gamma interferon inducible lysosomal thiol reductase (GILT) is a widespread superfamily which plays key role in processing and presentation of MHC class II restricted antigen by catalyzing disulfide bond reduction. There are no reports about GILT in T. spiralis. In present study, GILT from T. spiralis (Tsp-GILT) was cloned, analyzed by multiple-sequence alignment, and predicted by 3D structure model. Recombinant Tsp-GILT (about 46 kDa) was efficiently expressed in Escherichia coli and thiol reductase activity suggested that in acidic environment the addition of a reducing agent is needed. Soaking method was used to knockdown expression of Tsp-GILT using small interference RNA (siRNA). Immunofluorescence assay confirmed the transformation of siRNA into muscle larva (ML) and new born larva (NBL). Quantitative real time-PCR (QRT-PCR) analysis revealed that transcription level of Tsp-GILT mRNA can be up-regulated by stimulation of mouse IFN-γ and down-regulated by siRNA2 in vitro. NBLs soaked with siRNA2 showed 32.3% reduction in the generation of MLs. MLs soaked with siRNA2 showed 26.2% reduction in the next generation of MLs, but no significant effect was observed on adult worms or NBLs. These findings concluded that GILT may play important roles in the development of T. spiralis parasite.

Helminth-fauna of Patagonian armadillos: comparative analysis of parasites geographical variation

The similarity between parasites communities' decay with distance and its analysis may explain important ecological process such host dispersion. Patagonia is inhabited by two armadillo species, Chaetophractus villosus and Zaedyus pichiy. In this study we describe and analyze the variation on helminth fauna of these armadillos in Patagonia compared with northern localities described in previous studies. A total of 49 armadillos were collected in Patagonia. Quantitative descriptors of parasite ecology were calculated and community structure of helminths was analyzed following the central-satellite species hypothesis. The parasite richness in Patagonia decreases almost 50% in both armadillos. Zaedyus pichiy present the same central species in Patagonia as in northern localities. For C. villosus central-satellite species analysis could not be applied. The loss of some helminths in Z. pichiy could be the result of lower temperatures or the absence of intermediate arthropods hosts. But in C. villosus the absence of some helminths with Patagonian distribution could be explained by its recent dispersion in Patagonia. Trichohelix tuberculata still being the only helminth in C. villosus introduced population of Tierra del Fuego.

Oral vaccination with invasive Lactobacillus plantarum delivered nucleic acid vaccine co-expressing SS1 and murine interleukin-4 elicits protective immunity against Trichinella spiralis in BALB/c mice

Trichinellosis is a foodborne zoonosis caused by Trichinella spiralis (T. spiralis) that not only causes considerable economic losses for the global pig breeding and food industries, but also seriously threats the health of human. Therefore, it is very necessary to develop an effective vaccine to prevent trichinellosis. In this study, the invasive Lactobacillus plantarum (L. plantarum) expressing fibronectin-binding protein A (FnBPA) was served as a live bacterial vector to deliver DNA to the host to produce a novel oral DNA vaccine. Co-expressing T. spiralis SS1 and murine interleukin-4 (mIL-4) of DNA vaccine were constructed and subsequently delivered to intestinal epithelial cells via invasive L. plantarum. At 10 days after the third immunization, the experimental mice were challenged with 350 T. spiralis infective larvae. The results found that the mice orally vaccinated with invasive L. plantarum harboring pValac-SS1/pSIP409-FnBPA not only stimulated the production of anti-SS1-specific IgG, Th1/Th2 cell cytokines, and secreted(s) IgA but also decreased worm burden and intestinal damage. However, the mice inoculated with invasive L. plantarum co-expressing SS1 and mIL-4 (pValac-SS1-IL-4/pSIP409-FnBPA) induced the highest protective immune response against T. spiralis infection. The DNA vaccine delivered by invasive L. plantarum provides a novel idea for the prevention of T. spiralis infection.

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.

The Role of Peridomestic Rodents as Reservoirs for Zoonotic Foodborne Pathogens

Although rodents are well-known reservoirs and vectors for a number of zoonoses, the functional role that peridomestic rodents serve in the amplification and transmission of foodborne pathogens is likely underappreciated. Clear links have been identified between commensal rodents and outbreaks of foodborne pathogens throughout Europe and Asia; however, comparatively little research has been devoted to studying this relationship in the United States. In particular, regional studies focused on specific rodent species and their foodborne pathogen reservoir status across the diverse agricultural landscapes of the United States are lacking. We posit that both native and invasive species of rodents associated with food-production pipelines are likely sources of seasonal outbreaks of foodborne pathogens throughout the United States. In this study, we review the evidence that identifies peridomestic rodents as reservoirs for foodborne pathogens, and we call for novel research focused on the metagenomic communities residing at the rodent-agriculture interface. Such data will likely result in the identification of new reservoirs for foodborne pathogens and species-specific demographic traits that might underlie seasonal enteric disease outbreaks. Moreover, we anticipate that a One Health metagenomic research approach will result in the discovery of new strains of zoonotic pathogens circulating in peridomestic rodents. Data resulting from such research efforts would directly inform and improve upon biosecurity efforts, ultimately serving to protect our food supply.

Updated checklist of helminths found in terrestrial mammals of Argentine Patagonia

The aim of the present study was to evaluate the state of knowledge about the helminthology of wild mammals in Argentine Patagonia and its link with the conservation of parasite species and biodiversity. To this end, the information included in the previously reported checklist of the helminths found in terrestrial wild mammals of Argentine Patagonia was completed and updated. The methodology used for the search was the same as that previously used, with slight modifications. Eighty-two species of mammals currently inhabit the region, and an additional six species are considered to have become extinct before the 20th century. The reports used to complete and update the information correspond to research done since 2015 to date. Considering the number of records analysed in the previously reported checklist and those of the current update, a total of 1918 helminthological reports for current Patagonian mammals and 2141 on mammal species that inhabited Patagonia before the 20th century were accounted for. It is important to point out that 41% of the 82 species of wild mammals currently inhabiting Patagonia have not been studied helminthologically; 38% of these without helminthological records are either threatened or do not have categorization, and 79% of mammals without helminthological studies have some degree of endemism. Therefore, in order to evaluate conservation priorities, the information about the parasitic richness in Patagonian wild mammals should be substantially increased, especially in those endangered or endemic.

Study of Trichinella patagoniensis in wild boars

Trichinellosis is a zoonotic disease, which represents a significant public health concern in some South American countries, such as Argentina and Chile. Its impact is essentially due to absence of adequate control measures on meat from game animals, as well as the presence of illegal slaughterhouses and the trade of meat products without being tested for this parasite. In Argentina, trichinellosis is an endemic disease. At present, Trichinella spiralis, Trichinella patagoniensis, Trichinella pseudospiralis, and Trichinella britovi have been detected in animals from Argentina. Until now, T. patagoniensis had only been found in mountain cougars (Puma concolor) in Argentina but there is limited information available. The present study intends to determine susceptibility, serological response and distribution of muscle larvae in wild boars infected with T. patagoniensis, T. spiralis and T. pseudospiralis. For each of the Trichinella species five wild boars were inoculated with 20,000 muscle larvae. Except for two specimens which died during the experiment, the animals were euthanized 19 weeks post infection (pi). Blood samples were collected throughout the study in order to determine the antibody kinetics. Also, nine muscle samples from each specimen were taken and analysed for determination of larval distribution. Additionally, four muscle samples were used to obtain muscle juices. Wild boars infected with T. patagoniensis showed little to no larvae in the muscle samples analysed while animals infected with T. spiralis and T. pseudospiralis had a significantly high larval load in all the samples analysed. Optical density (OD) values remained above the cut-off value throughout the experiment. This is the first study to characterize the biological aspects of T. patagoniensis in wild boars.

Succinate Coenzyme A Ligase Beta-Like Protein from Trichinella spiralis Suppresses the Immune Functions of Rat PBMCs in Vitro and Inhibits the Secretions of Interleukin-17 in Vivo

Succinate Coenzyme A ligase beta-like protein (SUCLA-β) is a subunit of Succinyl-coenzyme A synthetase, which is involved in substrate synergism, unusual kinetic reaction in which the presence of SUCLA-β for one partial reaction stimulates another partial reaction. Trichinella spiralis is a parasitic nematode, which may hinder the development of autoimmune diseases. Immunomodulatory effects of SUCLA-β from Trichinella spiralis in the parasite-host interaction are unidentified. In this study the gene encoding T. spiralis SUCLA-β was cloned and expressed. Binding activities of recombinant T. spiralis SUCLA-β (rTs-SUCLA-β) to rat peripheral blood mononuclear cells (PBMCs) were checked by immunofluorescence assay (IFA) and the immuno-regulatory effects of rTs-SUCLA-β on cell migration, cell proliferation, nitric oxide (NO) production and apoptosis were observed by co-incubation of rTs-SUCLA-β with rat PBMCs in vitro, while cytokine secretions in rTs-SUCLA-β treated rats were evaluated in vivo. Furthermore, phagocytosis of monocytes was detected by flow cytometry and effects of rTs-SUCLA-β-induced protective immunity on T. spiralis adult worms and muscle larva were evaluated in rats. The IFA results revealed that rTs-SUCLA-β could bind to rat PBMCs. Treatment of PBMCs with rTs-SUCLA-β significantly decreased the monocyte phagocytosis, cell migration and cell proliferation, while NO production and apoptosis of PBMCs were unaffected. Results of the in vivo study showed that the IL-17 secretion decreased significantly after rTs-SUCLA-β administration in rats, while no significant effects were observed on the secretions of IFN-γ, IL-9, TGF-β and IL-4. Moreover, significant reduction of T. spiralis muscle larvae burden and significant increase in anti-rTs-SUCLA-β immunoglobulin level of IgG, IgG1 and IgG2a was observed in rTs-SUCLA-β-administered rats. The results indicated that rTs-SUCLA-β may be a potential target for controlling T. spiralis infection by suppressing the immune functions of the rat PBMCs and by reducing the parasite burden. Additionally it may also contribute to the treatment of autoimmune diseases and graft rejection by suppressing IL-17 immune response in the host.

Toxoplasma gondii and Trichinella infections in wild boars (Sus scrofa) from Northeastern Patagonia, Argentina

Wild boar (Sus scrofa) was introduced in many countries of the world and is recognized as carrier of many infectious diseases. Wild game meat consumption is recognized as a source of transmission of Toxoplasma gondii and Trichinella spp. The aim of the present study was to evaluate the prevalence of antibodies to T. gondii and Trichinella spp. in free-range wild boars in Northeastern Argentine Patagonia. Between 2014 and 2018, 144 blood samples and 423 muscle samples from 423 carcasses were collected. To detect T. gondii IgG, 144 sera were processed by an immunofluorescent antibody test, and to detect anti-Trichinella IgG, 125 sera and 304 muscle juice samples were processed by ELISA. Detection of first stage larvae in muscle was performed by artificial digestion. A total of 423 wild boars muscle samples were negative to Trichinella spp. by artificial digestion. Antibodies to Trichinella spp. were detected in 2.4% (3/125) of serum samples and in 1.64% (5/304) of meat juice samples. Antibodies to T. gondii infection were detected in 12.5% (18/144) of the serum samples. This is the first study to reveal the presence of antibodies to T. gondii in wild boars from Argentina. The present results suggest that consumption of raw or undercooked wild boar meat could represent a potential source risk for toxoplasmosis in humans and that Trichinella spp. is infrequent and/or that it circulates in low burdens among wild boars in Northeastern Patagonia.

Trichinella spiralis in a South American sea lion (Otaria flavescens) from Patagonia, Argentina

Trichinella spp. from a sylvatic cycle has been found in several animal species such as pumas (Puma concolor), armadillos (Chaetophractus villosus), rats (Rattus norvegicus), and wild boars (Sus scrofa) in Argentina. Moreover, Trichinella infection has been detected in a wide range of marine mammals around the world, including polar bears (Ursus maritimus) and walruses (Odobenus rosmarus). Until the present time, Trichinella spp. infection has not been detected in marine mammals of South America. Samples from four South American sea lions (Otaria flavescens) found dead in Rio Negro, Argentina, were analyzed by artificial digestion, and in the case of one animal, Trichinella larvae were identified at the species level by nested multiplex PCR as Trichinella spiralis. This is the first report of a Trichinella species infecting marine mammals from South America.

Trichinellosis surveillance in wildlife in northeastern argentine patagonia

Trichinellosis is a food-borne parasitic disease produced by different nematodes of the genus Trichinella. In Argentina, it is an endemic zoonosis and an important public health problem. The infection has been detected in domestic and wild animals. Trichinella spp. muscle larvae have anaerobic metabolism, which allows their survival in decaying tissues. The aim of this study was to evaluate the presence of Trichinella spp. in carnivorous and/or scavenger wild vertebrates - birds, mammals and reptiles - in northeastern Argentine Patagonia. Skeletal muscle samples from 141 animals, which were found killed on northeastern Argentine Patagonia roads, were analyzed by the artificial digestion method. None of the 141 samples were positive for larvae of Trichinella. These results suggest that Trichinella does not use these species to complete its cycle in this region of the continent and the absence of a significant alteration in the study area makes it difficult to transmit parasitic diseases. However, due to the limited number of samples assessed for some species, this could not be confirmed. The relevance of this study resides in the fact that it is the first systematic study in South America that considers birds, reptiles and mammals as potential hosts for Trichinella.

Intrinsic and extrinsic factors related to pathogen infection in wild small mammals in intensive milk cattle and swine production systems

BACKGROUND

Understanding the ecological processes that are involved in the transmission of zoonotic pathogens by small mammals may aid adequate and effective management measures. Few attempts have been made to analyze the ecological aspects that influence pathogen infection in small mammals in livestock production systems. We describe the infection of small mammals with Leptospira spp., Brucella spp., Trichinella spp. and Cysticercus fasciolaris and assess the related intrinsic and extrinsic factors in livestock production systems in central Argentina at the small mammal community, population and individual levels.

METHODOLOGY/PRINCIPAL FINDINGS

Ten pig farms and eight dairy farms were studied by removal trapping of small mammals from 2008 to 2011. Each farm was sampled seasonally over the course of one year with cage and Sherman live traps. The 505 small mammals captured (14,359 trap-nights) included three introduced murine rodents, four native rodents and two opossums. Leptospira spp., anti-Brucella spp. antibodies and Trichinella spp. were found in the three murine rodents and both opossums. Rattus norvegicus was also infected with C. fasciolaris; Akodon azarae and Oligoryzomys flavescens with Leptospira spp.; anti-Brucella spp. antibodies were found in A. azarae. Two or more pathogens occurred simultaneously on 89% of the farms, and each pathogen was found on at least 50% of the farms. Pathogen infections increased with host abundance. Infection by Leptospira spp. also increased with precipitation and during warm seasons. The occurrence of anti-Brucella spp. antibodies was higher on dairy farms and during the winter and summer. The host abundances limit values, from which farms are expected to be free of the studied pathogens, are reported.

CONCLUSIONS/SIGNIFICANCE

Murine rodents maintain pathogens within farms, whereas other native species are likely dispersing pathogens among farms. Hence, we recommend preventing and controlling murines in farm dwellings and isolating farms from their surroundings to avoid contact with other wild mammals.

Evaluation of protective efficacy induced by virus-like particles containing a Trichinella spiralis excretory-secretory (ES) protein in mice

BACKGROUND

The frequent outbreaks of human trichinellosis globally underscore the need to develop effective vaccine. We hypothesized that a novel vaccine could improve vaccine efficacy against Trichinella spiralis.

METHODS

In this study, we developed virus-like particles (VLPs) containing the 53 KDa excretory/secretory (ES) protein of T. spiralis and the influenza matrix protein 1 (M1) as a core protein, and investigated the protective efficacy of the VLPs alone or with cholera toxin (CT) in a mouse model.

RESULTS

Intramuscular immunization induced T. spiralis-specific IgG, IgG1 and IgG2a antibody responses before and after challenge infections in the sera. These antibody responses were significantly enhanced in mice immunized with adjuvanted VLPs. Upon challenge infection, vaccinated mice showed significantly reduced worm burden in the diaphragm. Protective immune responses and efficacy of protection were significantly improved by immunization with VLPs together with CT adjuvant.

CONCLUSIONS

Our results are informative for a better understanding of the protective immunity induced by T. spiralis VLPs, and will provide insight into designing safe and effective vaccines.

The occurrence of Trichinella species in the cougar Puma concolor couguar from the state of Colorado and other regions of North and South America

Trichinella species are zoonotic nematodes that infect wild carnivores and omnivores throughout the world. We examined the prevalence and species of Trichinella infections in cougars (Puma concolor couguar) from Colorado, United States. Tongues from cougars were examined by pepsin-HCl artificial digestion to detect Trichinella spp. larvae. The species or genotype of individual worms was identified by multiplex polymerase chain reaction (PCR). Trichinella spp. larvae were detected in 17 of 39 cougars (43.6% (28.7-59.5%)). Five of the cougars (12.8%) were infected with T. murrelli, 3 (7.7%) were infected with T. pseudospiralis, and 1 (2.6%) had Trichinella genotype T6. Trichinella spp. larvae from eight cougars were not identified at the species level, due to degraded DNA. The high prevalence of Trichinella spp. in cougars from Colorado and reports of the parasite in other populations of Puma spp. suggest that this large predator is a key mammalian reservoir.

A Review of the Current Status of Relevant Zoonotic Pathogens in Wild Swine (Sus scrofa) Populations: Changes Modulating the Risk of Transmission to Humans

Many wild swine populations in different parts of the World have experienced an unprecedented demographic explosion that may result in increased exposure of humans to wild swine zoonotic pathogens. Interactions between humans and wild swine leading to pathogen transmission could come from different ways, being hunters and game professionals the most exposed to acquiring infections from wild swine. However, increasing human settlements in semi-natural areas, outdoor activities, socio-economic changes and food habits may increase the rate of exposure to wild swine zoonotic pathogens and to potentially emerging pathogens from wild swine. Frequent and increasing contact rate between humans and wild swine points to an increasing chance of zoonotic pathogens arising from wild swine to be transmitted to humans. Whether this frequent contact could lead to new zoonotic pathogens emerging from wild swine to cause human epidemics or emerging disease outbreaks is difficult to predict, and assessment should be based on thorough epidemiologic surveillance. Additionally, several gaps in knowledge on wild swine global population dynamics trends and wild swine-zoonotic pathogen interactions should be addressed to correctly assess the potential role of wild swine in the emergence of diseases in humans. In this work, viruses such as hepatitis E virus, Japanese encephalitis virus, Influenza virus and Nipah virus, and bacteria such as Salmonella spp., Shiga toxin-producing Escherichia coli, Campylobacter spp. and Leptospira spp. have been identified as the most prone to be transmitted from wild swine to humans on the basis of geographic spread in wild swine populations worldwide, pathogen circulation rates in wild swine populations, wild swine population trends in endemic areas, susceptibility of humans to infection, transmissibility from wild swine to humans and existing evidence of wild swine-human transmission events.

Efficacy of albendazole:β-cyclodextrin citrate in the parenteral stage of Trichinella spiralis infection

Albendazole-β-cyclodextrin citrate (ABZ:C-β-CD) inclusion complex in vivo antiparasitic activity was evaluated in the parenteral phase of Trichinella spiralis infection in mice. An equimolar complex of ABZ:C-β-CD was prepared by spray-drying and tested in CBi-IGE male mice orally infected with L1 infective larvae. Infected animals were treated with 50 or 30mg/kg albendazole, (ABZ) equivalent amounts of the ABZ:C-β-CD complex and non treated (controls). Mice received a daily dose on days 28, 29 and 30 post-infection. A week later, larval burden and percentage of encysted dead larvae were assessed in the host by counting viable and non-viable larvae in the tongue. Complexation of ABZ with C-β-CD increased the drug dissolution efficiency nearly eightfold. At 37 days p-i, the reduction percentage in muscle larval load was 35% in mice treated with 50mg/kg/day ABZ and 68% in those given the complex. Treatment with the lower dose showed a similar decrease in parasite burden. Treated animals showed a high percentage of nonviable larvae, the proportion being significantly higher in mice receiving the complex than in control animals (72-88% vs. 11%, P=0.0032). These data indicate that ABZ:C-β-CD increases bioavailability and effectiveness of ABZ against encapsulated Trichinella larvae, thus allowing the use of small doses.

Protective immunity against enteral stages of Trichinella spiralis elicited in mice by live attenuated Salmonella vaccine that secretes a 30-mer parasite epitope fused to the molecular adjuvant C3d-P28

The development of a veterinary vaccine against T. spiralis infection is an alternative strategy to control trichinellosis. In an effort to develop an efficient vaccine, BALB/c mice were immunized with attenuated Salmonella enterica serovar Typhimurium SL3261 that expresses a 30-mer peptide (Ag30) derived from the gp43 of T. spiralis muscle larvae fused to three copies of the molecular adjuvant P28 (Ag30-P283) and it was either displayed on the surface or secreted by recombinant Salmonella strains. Salmonella strain secreting Ag30-P283, reduced the adult worm burden 92.8% following challenge with T. spiralis muscle larvae compared to 42% achieved by recombinant Salmonella displaying Ag30-P283 on the surface. The protection induced by secreted Ag30-P283 was associated with a mixed Th1/Th2 with predominance of Th2 phenotype, which was characterized by the production of IgG1, intestinal IgA antibodies and IL-5 secretion. This finding could provide an efficient platform technology for the design of novel vaccination strategies.

Description of an outbreak of human trichinellosis in an area of Argentina historically regarded as Trichinella-free: the importance of surveillance studies

Trichinellosis is an important food-borne zoonosis which is not treated as a major public health concern in Argentina. After more than 20 years without reports of infection in an area regarded as Trichinella-free, research studies reported that infection occurred in humans, pigs and game animals, including the recent outbreak of human trichinellosis revealed here. The outbreak, affecting 64 individuals, occurred in July 2010 in the province of Entre Ríos. Epidemiological studies, clinical observations, laboratory analyses and immunoserological specific assays (indirect immunofluorescence, IIF, and ELISA) were performed. Food samples were analyzed by artificial digestion, and Trichinella larvae isolates were identified to the species level by multiplex PCR. The main source of infection, commercially available food, had a parasite load of 1.1 muscle larvae per gram. Larvae were identified as Trichinella spiralis. Patients presented predominantly with oedema, fever and myalgia; and laboratory findings and/or immunoserological tests were positive for trichinellosis. Individuals received outpatient treatment. No deaths or secondary sequelae were recorded. Results suggest that the presence of T. spiralis infection should be suspected in all endemic areas, especially where animal husbandry and official food safety controls are not properly conducted. The lack of the cases reported ought not to be taken as a proof of parasite absence. We highlight the importance of the urgent need to implement interdisciplinary and inter-institutional programs aimed to control infection transmission, to guarantee food safety and to conduct epidemiological surveillance studies.

New pieces of the Trichinella puzzle

Contrary to our understanding of just a few decades ago, the genus Trichinella now consists of a complex assemblage of no less than nine different species and three additional genotypes whose taxonomic status remains in flux. New data and methodologies have allowed advancements in detection and differentiation at the population level which in turn have demonstrably advanced epidemiological, immunological and genetic investigations. In like manner, molecular and genetic studies have permitted us to hypothesise biohistorical events leading to the worldwide dissemination of this genus, and to begin crystalising the evolution of Trichinella on a macro scale. The identification of species in countries and continents otherwise considered Trichinella-free has raised questions regarding host adaptation and associations, and advanced important findings on the biogeographical histories of its members. Using past reviews as a backdrop, we have ventured to present an up-to-date assessment of the taxonomy, phylogenetic relationships and epidemiology of the genus Trichinella with additional insights on host species, survival strategies in nature and the shortcomings of our current understanding of the epidemiology of the genus. In addition, we have begun compiling information available to date on genomics, proteomics, transcriptomics and population studies of consequence in the hope we can build on this in years to come.

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.

Zoonoses: a potential obstacle to the growing wildlife industry of Namibia

Zoonoses, which account for approximately 75% of emerging human infectious diseases worldwide, pose a re-emerging threat to public health. With an ever-increasing interrelationship between humans, livestock and wildlife species, the threat to human health will rise to unprecedented levels. Wildlife species contribute to the majority of emerging diseases; therefore, there is an urgent need to define control systems of zoonoses of wildlife origin but very little information exists. In this review, we examine prevalent zoonotic infections reported in Namibia between 1990 and 2009 and assess their potential impact on the growing wildlife industry. A wide spectrum of zoonotic diseases was confirmed in both livestock and wildlife species, with rabies and anthrax cases being over-represented and also showing the widest species distribution. Whilst vaccination and ante-mortem inspection against these diseases may curb infected livestock species from entering the human food chain, such practices are difficult to implement in free-ranging wildlife species. In this context, there is a need to improve existing control measures and/or develop novel and better interventional strategies to reduce the threat of this re-emerging global problem. This review provides the basis for initiating a multidisciplinary evidence-based approach to control zoonoses in countries with thriving wildlife and game farming.

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.

Trichinella sp. in red foxes (Vulpes vulpes) from Catalonia, NE Spain

European legislation allows the official recognition of Trichinella-free pig holdings, provided Trichinella sp. infection is absent from humans and prevalence of Trichinella sp. infection in red foxes (Vulpes vulpes) is below 0.1% in the area, region or country. Tibialis anterior muscle samples from 1,319 red foxes captured in Catalonia (NE Spain) between 1998 and 2007 were analyzed for Trichinella sp. using the digestion method. Four foxes resulted positive (one in 1999, one in 2002 and two in 2006), accounting for a low prevalence (0.3%). However, this prevalence was concentrated in mountain or rural areas with a low sample size, reaching high local prevalences. The two positive samples in 2006 were characterized as Trichinella britovi, and a sylvatic cycle of trichinellosis seems to occur, at least in the rural insufficiently sampled regions of Catalonia. Overall, the results obtained do not currently allow the establishment of Trichinella-free pig holdings in the study area, but further research is needed to better know the prevalence and cycle of Trichinella sp. in Catalonia.