Spiralis-infected Pigs Research Articles

Divergence at mitochondrial and ribosomal loci indicates the split between Asian and European populations of Trichinella spiralis occurred prior to swine domestication.

Available evidence suggests that Trichinella spiralis first originated in Asia and subsequently spread to the rest of the world. Notably limited genetic diversity in European T. spiralis isolates indicates that the parasite went through a dramatic genetic bottleneck at some point in its history. Did this genetic bottleneck result from the transport of a limited number of T. spiralis infected pigs from Asian centers of domestication, or was the parasite resident in Europe far earlier than the domestication of pigs there? In order to explore this hypothesis, we generated complete mitochondrial genomes and ribosomal DNAs from seventeen European T. spiralis isolates, six North American isolates and seven Asian isolates using next generation sequencing. A total of 13,858 base pairs of mitochondrial DNA and 7431 nucleotides of the nuclear ribosomal DNA sequence from each isolate were aligned and subjected to phylogenetic analysis using T. nelsoni as an outgroup. We confirmed that North American and European isolates were tightly clustered within a single "western clade" and all Chinese T. spiralis isolates were placed within a well-supported sister clade. These results indicate that European T. spiralis did not directly descend from extant Chinese parasite populations. Furthermore, the amount of nucleotide divergence between the two clades suggests that they diverged before pigs were domesticated. Over evolutionary time periods, Chinese and European T. spiralis were likely maintained as separate populations. The data presented here indicates the genetic bottleneck observed in European T. spiralis did not result from a small number of founders introduced with Chinese pigs in the recent past, but derives from an earlier bottleneck in host populations associated with the end of the last glacial maximum.

Differences in larval survival and IgG response patterns in long-lasting infections by Trichinella spiralis, Trichinella britovi and Trichinella pseudospiralis in pigs

BackgroundDomesticated and wild swine play an important role as reservoir hosts of Trichinella spp. and a source of infection for humans. Little is known about the survival of Trichinella larvae in muscles and the duration of anti-Trichinella antibodies in pigs with long-lasting infections.MethodsSixty pigs were divided into three groups of 20 animals and infected with 10,000 larvae of Trichinella spiralis, Trichinella britovi or Trichinella pseudospiralis. Four pigs from each group were sacrificed at 2, 6, 12, 18 and 24 months post-infection (p.i.) and the number of larvae per gram (LPG) of muscles was calculated. Serum samples were tested by ELISA and western blot using excretory/secretory (ES) and crude antigens.ResultsTrichinella spiralis showed the highest infectivity and immunogenicity in pigs and larvae survived in pig muscles for up to 2 years p.i. In these pigs, the IgG level significantly increased at 30 days p.i. and reached a peak at about 60 days p.i., remaining stable until the end of the experiment. In T. britovi-infected pigs, LPG was about 70 times lower than for T. spiralis at 2 months p.i. and only very few infecting larvae were detected at 6 months p.i., whereas no larvae were detected at 12, 18 and 24 months p.i. At 6 months p.i., degenerated/calcified larvae and cysts were detected in the muscles by trichinoscopy and histology. The IgG pattern showed by T. britovi-infected pigs was similar to that of T. spiralis-infected pigs, although seroconversion occurred some days later. The larval burden of T. pseudospiralis was slightly greater than for T. britovi at 2 months p.i., but no larvae were detected at 6 and 12 months p.i. In T. pseudospiralis-infected pigs, seroconversion occurred slowly, as in T. britovi-infected pigs. The IgG level showed a significant drop at 6 months p.i. and declining to the cut-off value at 12 months p.i.ConclusionsThe longer survival of T. spiralis in pigs in comparison with the other two species highlights its exceptional dissemination potential. These results provide an explanation of the controversial data collected by parasitological and serological tools in the course of epidemiological investigations.

A distinctive Western blot pattern to recognize Trichinella infections in humans and pigs

Trichinellosis is a zoonotic disease caused by parasites of the genus Trichinella, which have a cosmopolitan distribution. For diagnostic purposes, a confirmatory test for ELISA-positive human and pig sera such as Western blotting is required, due to the high number of ELISA false positive sera. The objective of this study was to identify the Trichinella-specific antigens most frequently recognized by sera from Trichinella-infected humans and pigs, so as to define a distinctive pattern of Trichinella infection in sera from infected hosts using Western blots which allow false positive sera to be distinguished from true positive sera. Using excretory/secretory antigens, 450 human sera were tested by Western blotting: 150 from persons with a confirmed diagnosis of trichinellosis and 300 from persons who did not have trichinellosis but who tested positive by ELISA (i.e., false positives). We also tested 210 pig sera: (i) 30 from pigs experimentally infected with Trichinella spiralis; (ii) 90 from naturally T. spiralis-infected pigs; and (iii) 90 from pigs not infected with Trichinella, as shown after artificial digestion of the diaphragm pillars, yet which tested positive by ELISA (i.e., false positives). All true positive sera (i.e., sera from persons with confirmed trichinellosis as well as sera from naturally and experimentally infected pigs), reacted with a three-band pattern ranging in size from 48–72kDa. A distinctive pattern for recognizing Trichinella spp. infections in humans and pigs by Western blots is defined; it shows a sensitivity of 100% and it allows sera from Trichinella-infected humans and pigs to be distinguished from sera from persons and pigs that were not infected with Trichinella spp. (100% specificity).

Histo-Blood Group Carbohydrates and Helicobacter pylori Infection

Trichinellosis is a wide spread food borne zoonosis caused by species of the genus Trichinella. Until present T. spiralis is the only species usually found in porcine, sinantropics and wild animals from Argentina. Nevertheless, Krivokapich et al. [1] isolated a novel species (Trichinella T12) from a Puma concolor, T. spiralis can be transmitted and maintained in both a domestic and sylvatic cycle whereby rats, among others contribute to the spread of T. spiralis from domestic to sylvatic animals and vice versa. In this research we studied the presence of Trichinella infection in rodents which inhabit pig farms from General La Madrid, Buenos Aires, Argentina. For this purpose, 9 pig farms with different levels of sanitation and with or without T. spiralis infected pigs and a garbage dump were assessed between spring 2008 and winter 2009. A total of 150 rodents were captured. All the species belonged to the genus Rattus species norvegicus. The presence of Trichinella spp was tested by artificial digestion of each muscle sample. No positive Trichinella infection was found. Further assessment would be done so as to deal with the role of rats in the life cycle of Trichinella spp.

The epidemiological investigation of Trichinella infection in brown rats (Rattus norvegicus) and domestic pigs in Croatia suggests that rats are not a reservoir at the farm level.

Whether the brown rat (Rattus norvegicus) is a reservoir of Trichinella spp. infection or merely an accidental host, which may be vector of Trichinella spp., continues to be debated. We estimated the prevalence of Trichinella sp. infection in brown rat populations and in domestic pigs in 2 villages in Croatia, where Trichinella sp. infection in pigs has been endemic in the past 10 yr. Trichinella spiralis larvae, identified by a multiplex polymerase chain reaction analyses, were the only species detected in both rats and pigs. In 2001 and 2002, 2,287 rats were collected on 60 farms with different levels of sanitation and with, or without, T. spiralis-infected pigs. The prevalence of infection in rats ranged from 0.2 to 10.7%. Infected rats were detected only on farms with T. spiralis-positive pigs and low sanitation or formerly with low sanitation (P = 0.007, Fisher's exact test), yet no infected rat was detected on farms with T. spiralis-negative pigs. The finding that no infected rat was found on farms with T. spiralis-negative pigs suggests that, in the investigated area, the brown rat is not a reservoir but only a victim of improper pig slaughtering.

Identification of a surrogate TSL-1 antigen of Trichinella spiralis from a phage library of random peptides.

We sought to find a peptide analogue of an important antigen (TSL-1) of Trichinella spiralis which is recognized by the 7C2C5 antibody. A phage library which displays a short (15-mer) randomly-generated peptide at the filament of the minor coat protein of the virion was used for selection by the 7C2C5 antibody. A peptide thus identified, ICDASGLGCWCWSLSP, was found to be a true surrogate since its binding to the antibody could be blocked by the native antigen and, conversely, an antiserum made to the peptide could recognize the native antigen. In addition, the peptide appeared to detect T. spiralis-infected pigs although it was less discriminatory than the native antigen.

Detection of Trichinellosis in Pigs by Artificial Digestion and Enzyme Immunoassay

The objective of this study was to demonstrate the reliability of current and proposed methods for the inspection of swine and other species for infection with the parasite Trichinella spiralis.Five groups of pigs were infected with doses of 2500, 500, 100, 50, and 20 T. spiralis larvae to establish moderate and low-level infections. Pigs were bled periodically during the study for samples to be tested by enzyme immunoassay (EIA). At the conclusion of the study, pigs were slaughtered and tissues collected for analyses of worm burdens and for comparison of digestion testing methods. Comparisons of pooled sample digestion methods were made using inspection methods prescribed by European Union Directives and the USDA, Code of Federal Regulations.Pooled sample digestion testing using 1-g samples was effective for detecting pigs with larval densities of >10 larvae per gram (LPG) of tissue but only partially effective for pigs with infections of <3 LPG. Pooled sample digestion testing using 5-g samples detected all pigs with infection levels >1 LPG. The EIA detected all T. spiralis-infected pigs, but did not detect infections in some pigs until 49 days after inoculation. These results demonstrate that the pooled sample digestion method using a 5-g sample size is the most effective inspection method for reducing the risk of human exposure to T. spiralis in pork.

Immunosuppression of in vivo and in vitro lymphocyte responses in swine induced by Trichinella spiralis or excretory-secretory antigens of the parasite

0he in vivo and in vitro effects of Trichinella spiralis excretory-secretory (ES) antigens on porcine peripheral blood lymphocyte (PBL) responses induced with mitogens (phytohemagglutinin, PHA; concanavalin A, Con A; pokeweed mitogen, PWM) or unrelated antigen (Protein A) were studied to determine whether ES antigens depress lymphocyte responses in experimental swine trichinosis, and/or if this response was manifested after lymphocytes from infected pigs had been pretreated with ES antigens. Additionally, the range of inhibition of lymphocyte responses was tested in parasite-free pigs using different doses of ES antigens and compared with the responsiveness of control cultures from the same animals. The responses of lymphocytes from pigs inoculated with 4 × 10 3 muscle larvae (ML) were strongly depressed ( P < 0.05) at post-inoculation days (PID) 7 (after stimulation with PHA), 14, 35 (Con A or PWM), and 49 (PWM). At PID 56 and 63 the lymphocytes from T. spiralis-infected pigs responded better ( P < 0.05) to all three mitogens than those from non-infected controls. After 7 weeks post-inoculation, PBL which were pretreated with 10 or 25 μg ml −1 of ES antigens showed significantly weaker ( P < 0.05, P < 0.001) responses to PWM or PHA,respectively, than those from non-infected animals. The responsiveness of lymphocytes from both groups of pigs to Protein A was not affected by the pretreatment with ES antigens in vitro. The responses of lymphocytes from the parasite-free pigs induced by PHA, PWM or Protein A were strongly depressed ( P < 0.01) after in vitro pretreatment regardless of the dose of ES antigens (5, 10, 15, or 20 μg ml −1) applied.