Global prevalence of latent toxoplasmosis in pregnant women: a systematic review and meta-analysis.

BACKGROUND: Toxoplasma gondii infection, if acquired as an acute infection during pregnancy, can have substantial adverse effects on mothers, fetuses and newborns. Latent toxoplasmosis also causes a variety of pathologies and has been linked to adverse effects on pregnancy. OBJECTIVE: Here, we present results of a comprehensive systematic review and meta-analysis of the global prevalence of latent toxoplasmosis in pregnant women. DATA SOURCE: We searched PubMed, EMBASE, Web of Science, SciELO and Scopus databases for relevant studies that were published between 1 January 1988 and 20 July 2019. STUDY ELIGIBILITY CRITERIA: All population-based, cross-sectional and longitudinal studies reporting the prevalence of latent toxoplasmosis in healthy pregnant women were considered for inclusion. PARTICIPANTS: Pregnant women who were tested for prevalence of latent toxoplasmosis. INTERVENTIONS: There were no interventions. METHOD: We used a random effects model to calculate pooled prevalence estimates with 95% confidence intervals (CIs). We grouped prevalence data according to the geographic regions defined by the World Health Organization (WHO). Multiple subgroup and meta-regression analyses were performed. RESULTS: In total, 311 studies with 320 relevant data sets representing 1 148 677 pregnant women from 91 countries were eligible for inclusion in the meta-analysis. The global prevalence of latent toxoplasmosis in pregnant women was estimated at 33.8% (95% CI, 31.8-35.9%; 345 870/1 148 677). South America had the highest pooled prevalence (56.2%; 50.5-62.8%) of latent toxoplasmosis in pregnant women, whereas the Western Pacific region had the lowest prevalence (11.8%; 8.1-16.0%). A significantly higher prevalence of latent toxoplasmosis was associated with countries with low income and low human development indices (p < 0.001). CONCLUSION: Our results indicate a high level of latent toxoplasmosis in pregnant women, especially in some low- and middle-income countries of Africa and South America, although the local prevalence varied markedly. These results suggest a need for improved prevention and control efforts to reduce the health risks to women and newborns.

Low salt exposure results in inactivation of Toxoplasma gondii bradyzoites during formulation of dry cured ready-to-eat pork sausage.

The production of safe and healthy food products represents one of the main objectives of the food industry. The presence of microorganisms in meat and products containing meat can result in a range of human health problems, as well as economic losses to producers of these products. However, contaminated meat products continue to initiate serious and large-scale outbreaks of disease in consumers. In addition to outbreaks of diseases caused by bacteria and viruses, parasitic organisms, such as Toxoplasma gondii, are responsible for foodborne infections worldwide, and in the case of T. gondii, is considered the 2nd leading cause of death from foodborne illness in the U.S. Transmission of Toxoplasma gondii has historically been linked to the consumption of raw or undercooked meat products, including pork. Specific concerns with respect to pork products are ready-to-eat (RTE) pork meals. These are pork or products containing pork that are prepared by curing or drying, and are not intended to be cooked before being consumed. Previous studies have demonstrated that T. gondii is inactivated during dry cured sausage preparation, apparently in the batter during fermentation. In this study, we have analyzed timing of inactivation of T. gondii in freshly prepared pepperoni batter to confirm our previous findings, to determine how quickly inactivation occurs during fermentation, and to confirm what parameters of the sausage preparation are involved in inactivation of the parasite. Results from the current and previous study indicate that rapid inactivation of T. gondii bradyzoites occurs in low salt batter for dry cured sausage within 4 h of initiation of fermentation.

Rapid inactivation of Toxoplasma gondii bradyzoites during formulation of dry cured ready-to-eat pork sausage.

Curing processes for pork meat in the U.S. currently require individual validation of methods to demonstrate inactivation of Trichinella spiralis, a nematode parasite historically associated with pork. However, for protozoan parasites, no such strictures exist. It has been assumed, with little evidence, that curing processes required to inactivate Trichinella also inactivate Toxoplasma gondii. Currently no model of meat chemistry exists that can be correlated with inactivation of T. gondii. Given the possibility of the presence of T. gondii in pork meat, and the frequent use of pork for ready-to-eat (RTE) products not intended to be cooked, curing methods which inactivate T. gondii early in the curing process would be of great value to producers. In this study, we tested the effect of five variables - salt/brine concentration, water activity (aw), pH, temperature, and time on inactivation of T. gondii bradyzoites in tissue cysts using low and high endpoints for common curing treatments during preparation of dry cured pork sausage. Survival of T. gondii bradyzoites at each stage of preparation was assessed using a mouse bioassay. Results indicated that encysted T. gondii bradyzoites do not survive the early stages of the dry curing process within the endpoint parameters tested here, even at levels of NaCl that are lower than typically used for dry curing (1.3%). Exposure of T. gondii encysted bradyzoites to curing components in the formulated batter resulted in rapid inactivation of bradyzoites. These data suggest that the use of dry curing components may be effective for controlling T. gondii potentially transmitted through RTE meats, rendering them safe from risk with respect to T. gondii transmission to human consumers.

Curing conditions to inactivate Trichinella spiralis muscle larvae in ready-to-eat pork sausage.

Curing processes are one method by which pork products, which are considered ready to eat (RTE) and have not been otherwise tested or treated, can be rendered safe from risk for exposure to Trichinella muscle larvae (ML). Curing processes in the U.S. currently require individual validation of methods to demonstrate inactivation of Trichinella. This is a major undertaking for each process; currently no model of meat chemistry exists that can be correlated with inactivation of Trichinella. Given the potential for new RTE products (e.g., lower salt), the availability of a wider range of tested methods for inactivation of Trichinella in pork would be of substantial value to the industry. In this study, five variables were tested - salt/brine concentration, water activity (aw), pH, temperature, and time, using low and high endpoints for common curing treatments for dry cured pork sausage. The data demonstrated that NaCl concentrations above 1.3%, in combination with fermentation to pH 5.2 or below, resulted in inactivation of > 96% of Trichinella ML in stuffed sausages within 24-28 h. All ML were inactivated by 7-10 days post-stuffing. These curing processes reliably predict inactivation of Trichinella spiralis, and can be used within the defined upper and lower endpoint parameters to reduce or eliminate the need for individual product validation.

Toxoplasmosis in sentinel chickens (Gallus domesticus) in New England farms: Seroconversion, distribution of tissue cysts in brain, heart, and skeletal muscle by bioassay in mice and cats.

Free-range chickens are a good indicator of soil contamination with oocysts because they feed from the ground and they are also an important source of infection for cats that in turn shed oocysts after eating tissues of intermediate hosts. Little is known of the epidemiology of toxoplasmosis in chickens. In the present study 90 Toxoplasma gondii seronegative, sentinel chickens were placed on three (30 each) swine farms in New England in November, 2003. Chickens were bled monthly and their sera were tested for T. gondii antibodies by the modified agglutination test (MAT, cut-off 1:25). Chickens that seroconverted were euthanized and their tissues were bioassayed in mice, cats, or both. Over the course of the experiment (7 months), 31 of 71 chickens seroconverted (MAT 1:100 or higher). Tissues of 26 seropositive chickens were bioassayed in both cats and mice; viable T. gondii was isolated, by bioassay in mice, from hearts (whole) of all 26 chickens, brains (whole) of 3 chickens and leg muscles (25 g) of 11 chickens; 21 of 26 cats fed 250 g of muscle from seropositive chickens excreted T. gondii oocysts. Results indicated that the density of T. gondii in poultry muscle is low but heart is the tissue of choice for isolation of viable parasites.

Surveillance of feral swine for Trichinella spp. and Toxoplasma gondii in the USA and host-related factors associated with infection.

Trichinella spp. and Toxoplasma gondii are important zoonotic parasites that infect warm blooded animals and humans worldwide. Among domesticated food animals, pigs are the main host for Trichinella spiralis. Pigs, chickens, sheep, and goats are known to be infected with T. gondii at varying rates, depending on husbandry. Infections in wildlife with these parasites are generally higher than in domesticated species. Feral swine act as reservoirs of infection in the sylvatic ecosystem for Trichinella spp. and T. gondii, acting as sources of infection for peridomestic carnivores whose home ranges overlap with domestic pigs. Feral swine can have direct contact with non-biosecure domestic pigs, presenting opportunity for direct disease transmission through cannibalistic behavior. Determination of the prevalence of Trichinella spp. and T. gondii infection in feral swine is needed to understand the risk of transmission of these parasites to domestic pigs. A cross-sectional serological survey was conducted between 2006 and 2010 to estimate the antibody prevalence of Trichinella spp. and T. gondii and risk factors associated with infection in feral swine in the USA. Serum samples were tested from 3247 feral pigs from 32 states; results are reported from 26 states. Maximum entropy ecological niche modeling and spatial scan statistic were utilized to predict the geographic range and to examine clusters of infection of Trichinella spp. and T. gondii in feral pigs. The seroprevalence of antibodies to Trichinella spp. and T. gondii was 3.0% and 17.7%, respectively. Species distribution modeling indicated that the most probable distribution areas for both parasites was similar, concentrated primarily in the South and the Midwest regions of the USA. A follow up survey conducted during 2012-2013 revealed that 2.9% of 984 sampled feral swine were seropositive for Trichinella spp., and 28.4% were seropositive for T. gondii. Three hundred and thirty (330) tongues were collected from the 984 sampled animals during 2012-2013; 1.81% were tissue positive for T. spiralis muscle larvae; no other genotypes were found. The potential exists for introduction of these pathogens into domestic herds of non-biosecure domestic pigs as a result of increasing overlap of the range of feral pigs with non-biosecure domestic pigs production facilities in the USA.

Trichinella infection in wild animals from endemic regions of Argentina.

Natural infection with Trichinella has been described in more than 150 mammalian species. However, few reports of Trichinella infection in wild animals have come from Argentina. In this study, muscle tissue was obtained from wild animals in Argentina with the aim of evaluating the presence of Trichinella. A total of 169 muscle samples were collected to determine the presence of Trichinella larvae by artificial digestion. The 169 muscle samples originated from 12 species including 36 opossums (Didelphis albiventris), 19 armadillos (Chaetophractus villosus), 9 capybaras (Hydrocaeris hydrocaeris), 1 puma (Puma concolor), 3 grey fox (Lycalopex gymnocercus), 6 coypus (Myocastor coypus), 6 skunks (Conepatus chinga), 2 ferrets (Galictis cuja), 66 rats (Rattus norvegicus), 6 mice (Mus musculus), 12 wild boars (Sus scrofa), and 3 wild cats (Felis geoffroyi). Trichinella infection was detected in 1 puma [2 larvae per gram (LPG)], 3 wild boars (8-420 LPG), 3 armadillos (0.04-0.08 LPG), and 9 rats (0.1 to 150 LPG). Only 3 Trichinella isolates, of 1 rat and 2 wild boars from Neuquén, were identified as Trichinella spiralis by nested PCR. The presence of Trichinella infection among wild animal populations suggests a sylvatic cycle of transmission in Argentina, which can serve as a reservoir for humans and domestic animals. Further, evidence of high prevalence in rats emphasizes the need to improve pig management, mainly in small individual farms without adequate technology, to enhance the quality of feeds, and to improve veterinary services to avoid exposure of pigs to Trichinella.

Seroprevalence of and risk factors for Toxoplasma gondii in the US swine herd using sera collected during the National Animal Health Monitoring Survey (Swine 2006).

The United States Department of Agriculture (USDA) initiated the National Animal Health Monitoring System (NAHMS) in 1983 to collect, analyse and disseminate data on animal health, management and productivity in US domestic livestock populations, including swine. The programme includes an on-farm serological sampling component which can be used to monitor seroprevalence of various pathogens, including Toxoplasma gondii. The purpose of this study was to determine the seroprevalence of T. gondii in grower/finisher pigs using sera collected during NAHMS Swine 2006 and to determine farm level factors associated with differences in seroprevalence on farms where sera was collected during the Swine 2006 survey. Sera and data on management practices for this study were collected from 185 grower/finisher swine production sites located in 16 states accounting for > 90% of US swine production (Arkansas, Colorado, Iowa, Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Carolina, Ohio, Pennsylvania, South Dakota, Texas and Wisconsin). A total of 6238 sera were tested for T. gondii antibodies using a commercial ELISA assay (Vet. Parasitol.128, 2005, 177). Seroprevalence in this study, as determined by ELISA, was 2.6%, with a herd prevalence of 21.6% and a mean within-herd prevalence of 2.7%. Analysis of swine management practices indicated that rodent control methods and carcass disposal methods were associated with differences in the number of T. gondii positive samples on farm. These results are consistent with current epidemiological knowledge of the transmission of Toxoplasma on the farm (ingestion of organic matter containing oocysts, or ingestion of infected animal tissues). Production practices which eliminate these sources of exposure can reduce the risk of Toxoplasma infection in pigs, and reduce the likelihood of human infection from consumption of infected pork.

Survival of North American genotypes of Trichinella in frozen pork.

North American genotypes of Trichinella spiralis (T-1), Trichinella nativa (T-2), Trichinella pseudospiralis (T-4), Trichinella murrelli (T-5), and Trichinella T-6 were examined for susceptibility to freezing in pork using time-temperature combinations that have been proven to inactivate T. spiralis. Infections were established in 3-month-old pigs of mixed sex and breed by oral inoculation of 10,000 muscle larvae (ML) (all genotypes, rodent-derived ML), 20,000 ML (T-1, T-4, and T-5; cat-derived ML), or 30,000 ML (T-2 and T-6; cat-derived ML). Pigs were euthanized 60 days postinoculation. Muscles from the tongue, masseter muscles, diaphragm, triceps, hams, neck, rump, and loins were ground, pooled, and mixed to ensure even distribution of larvae. Samples (20 g) containing each Trichinella species, genotype, and source combination were placed in heat-sealable pouches, transferred to a constant temperature refrigerant bath, and maintained according to defined time and temperature combinations. Larvae recovered from cold-treated pork samples were inoculated into mice to determine infectivity. Results indicated that the time-temperature combinations known to render pork safe for T. spiralis are sufficient to inactivate T. nativa and T-6 (the freeze-resistant isolates), T. murrelli (the most common sylvatic species in the United States excluding Alaska), and T. pseudospiralis (a species that lacks a muscle nurse cell). These data close a gap in knowledge about the effectiveness of freezing for inactivating these parasites in pork and should alleviate concern about the safety of frozen pork products from the United States.

Evaluation of the risk of transmission of Trichinella in pork production systems in Argentina.

Recently, there has been interest in programs that certify pork production practices that minimize the risk of exposure of pigs to Trichinella spiralis. Certification might be useful for reducing the risk of human trichinellosis from pork in Argentina, but more information is needed on pig production practices and sources of Trichinella infection in Argentinian pigs. In this study, 21 pig farms were assessed for Trichinella infection including some farms using total and partial confinement management, and others with pigs raised exclusively outdoors. A total of 3224 muscle samples were collected from pigs raised on these farms and tested to determine the presence of T. spiralis larvae by artificial digestion. Serum samples from the same 3224 pigs were tested for antibodies to T. spiralis by ELISA. For each farm, a questionnaire was completed summarizing information about management factors and this information was used to assess risk factors for exposure of T. spiralis. Based on the results, pigs raised outdoors were more likely to be infected than pigs raised in total or partial confinement (p< or =0.05). Pigs fed waste products containing meat were 12.5 times more likely to be infected than pigs not fed waste containing meat (p<0.01). The role played by rats in transmission of Trichinella is unclear; however, on farms with evidence of wild animals and access of pigs to wildlife carcasses, the prevalence of Trichinella infection was significantly higher. All pigs raised under good hygienic and sanitary conditions were negative for Trichinella infection by both artificial digestion and ELISA.

Complete validation of a unique digestion assay to detect Trichinella larvae in horse meat demonstrates the reliability of this assay for meeting food safety and trade requirements.

A tissue digestion assay using a double separatory funnel procedure for the detection of Trichinella larvae in horse meat was validated for application in food safety programs and trade. The assay consisted of a pepsin-HCl digestion step to release larvae from muscle tissue and two sequential sedimentation steps in separatory funnels to recover and concentrate larvae for detection with a stereomicroscope. With defined critical control points, the assay was conducted within a quality assurance system compliant with International Organization for Standardization-International Electrotechnical Commission (ISO/IEC) 17025 guidelines. Samples used in the validation were obtained from horses experimentally infected with Trichinella spiralis to obtain a range of muscle larvae densities. One-, 5-, and 10-g samples of infected tissue were combined with 99, 95, and 90 g, respectively, of known negative horse tissue to create a 100-g sample for testing. Samples of 5 and 10 g were more likely to be positive than were 1-g samples when larval densities were less than three larvae per gram (lpg). This difference is important because ingested meat with 1 lpg is considered the threshold for clinical disease in humans. Using a 5-g sample size, all samples containing 1.3 to 2 lpg were detected, and 60 to 100% of samples with infected horse meat containing 0.1 to 0.7 lpg were detected. In this study, the double separatory funnel digestion assay was efficient and reliable for its intended use in food safety and trade. This procedure is the only digestion assay for Trichinella in horse meat that has been validated as consistent and effective at critical levels of sensitivity.

Clinical, haematological, biochemical and economic impacts of Trichinella spiralis infection in pigs.

The purpose of this work was to assess the clinical, haematological and biochemical responses of pigs experimentally inoculated with Trichinella spiralis. Groups of three pigs were inoculated per os with 100, 500 and 5000 T. spiralis muscle larvae, two pigs were used as control. Clinical evaluation of disease in pigs included daily examination, rectal temperature measurements and cardiac and respiration rates. Haematological studies included: hematocrit (%), hemoglobin (g/dl), and white cell, neutrophil, lymphocyte and eosinophil counts. Blood biochemistry included: bun (mg/dl), creatinine (mg/dl), AST (UI/l), ALT (UI/l), CPK (UI/l) and ALP (UI/l). No significant differences were observed in rectal temperature and in cardiac and respiration rates between inoculated animals and the control group (p> or =0.05). Significant differences were detected (p< or =0.05) in the values of % hemoglobin, and eosinophils, as well as in the values of CK, ALP, AST and ALT. The variations observed in some cases were related to the number of T. spiralis larvae inoculated and varied with the number of days post-infection. Inoculated pigs showed significant differences (p< or =0.05) in weight gain when compared with uninoculated controls. This study has clinical, haematological, and enzyme alterations in Trichinella infected pigs provides a better understanding of acute and chronic trichinellosis in pigs.

Viability and infectivity of Trichinella spiralis muscle larvae in frozen horse tissue.

Many aspects of the biology and epidemiology of Trichinella infection in the horse are poorly understood, including survival of Trichinella spp in horse muscle. In this study, we have assessed the freeze tolerance of T. spiralis in horse meat stored at 5, -5, and -18 degrees C for 1 day to 24 weeks. Results demonstrate a steady reduction in the number of live ML recovered from the cold stored meat samples. On Day 1, recovery of live larvae had been reduced by 18.6%, 50.1%, and 37.2%, and by 4 weeks, recovery of larvae had been reduced by 65.4%, 66.5%, and 96.2% in samples stored at 5, -5, and -18 degrees C, respectively. Infectivity results (measured as reproductive capacity index (RCI)) from mice inoculated with larvae recovered from non-frozen meat samples at day 0 was 23.5. Following storage at -18 degrees C for one and two days, the RCIs were 2.09 and 0.99, respectively. Small numbers of infective larvae were still present in meat samples stored at -18 degrees C for 4 weeks. The RCI of ML recovered from meat samples stored at -5 degrees C was 14.99 and 6.36 at 2 weeks and 4 weeks respectively; the RCI of samples stored at 5 degrees C was 23.1 at 8 weeks, and fell rapidly thereafter (12 week RCI 1.33; 0 at 24 weeks). These data demonstrate that infective T. spiralis, a non-freeze tolerant species, can survive for at least 4 weeks in horse tissue frozen at -5 or -18 degrees C, and that the numbers of infective larvae decrease substantially by day 2 at -18 degrees C and by week 4 at -5 degrees C.

Larval viability and serological response in horses with long-term Trichinella spiralis infection.

The horse is considered an aberrant host for the nematode parasite Trichinella spiralis, and many aspects of the biology and epidemiology of Trichinella infection in the horse are poorly understood. It has been reported that experimentally-infected horses produce a transient serological response to infection and that muscle larvae are cleared more rapidly than in parasite-adapted hosts such as the pig and humans. However, limited numbers of animals have been studied, and both the longevity of larvae in horse musculature and the immune response to Trichinella larvae remain unclear. In this study, we infected 35 horses with 1000, 5000, or 10,000 T. spiralis muscle larvae and followed the course of infection for 1 year, assessing larval burdens in selected muscles, the condition and infectivity of recovered larvae, and the serological response of infected horses. The results demonstrated that T. spiralis establishes infection in horses in a dose dependent manner. Anti-Trichinella IgG antibodies peaked between weeks 6-10 post-inoculation. Viable, infective larvae persisted in horse musculature for the duration of the study (12 months), and exhibited no apparent reduction in muscle burdens over this period. Encapsulated larvae showed no obvious signs of degeneration in histological sections. Larval capsules were surrounded by infiltrates consisting of mature plasma cells and eosinophils. Macrophages were notably absent. Given the lack of a detectable serological response by 26 weeks p.i. and the persistence of infective muscle larvae for at least 1 year, parasite recovery methods are currently the only suitable detection assays for both meat inspection and epidemiological studies of Trichinella infection in the horse.

Trichinellosis in Argentina: an historical review.

In Argentina, Trichinella infection in pigs is endemic. The first report of human trichinellosis in Argentina was from 1898 in Buenos Aires. The number of human cases increased from 908, between 1971 and 1981, to 6,919, between 1990 and 2002. In pigs slaughtered in official establishments, the prevalence of Trichinella infection was 0.46% in 1914 and 0.01--0.03% during the period 1990--2004. T. spiralis is typically found in the domestic cycle that includes pigs, humans and rodents. Trichinella spp. from a sylvatic cycle has also caused human outbreaks resulting from the consumption of meat from puma, armadillo and wild boar. European migration to Argentina (principally Spanish and Italian) during the first years of the 20th century brought the tradition of preparing and eating raw sausages. This increased the risk of human exposure to Trichinella. Detection in pigs was initially made at slaughter by compression of muscle tissue (trichinoscopy) and continued this way until 1996, when artificial digestion was adopted for use in preventing human trichinellosis in Argentina. The following report synopsizes the evolution of trichinellosis in Argentina over the past century.

Trichinella pseudospiralis from a wild pig in Texas.

In December 2001, the routine inspection of a wild boar intended for human consumption revealed the presence of Trichinella ssp. larvae. Biological, morphological and genetic analyses demonstrated the parasite to be Trichinella pseudospiralis. This is the second report of T. pseudospiralis in the United States and the first report of the parasite in a food animal species in the U.S.

Trichinella nativa in a black bear from Plymouth, New Hampshire.

A suspected case of trichinellosis was identified in a single patient by the New Hampshire Public Health Laboratories in Concord, NH. The patient was thought to have become infected by consumption of muscle larvae (ML) in undercooked meat from a black bear killed in Plymouth, NH in October 2003 and stored frozen at -20 degrees C fro 4 months. In January 2004, a 600 g sample of the meat was thawed at 4 degrees C, digested in hydrochloric acid and pepsin, and larvae were collected by sedimentation. Intact, coiled, and motile ML were recovered (366 larvae per gram (l pg) of tissue), which were passed into mice and pigs. Multiplex PCR revealed a single 127 bp amplicon, indicative of Trichinella nativa. The Reproductive Capacity Index (RCI) for the T. nativa-Plymouth isolate in mice was 24.3. Worm burdens in the diaphragms of two 3-month-old pigs given 2,500 ML were 0.05 and 0.2l pg by 35 days post-inoculation, while 2.2 and 0.75 l pg were recovered from two 3-month-old pigs given 10,000 ML; no larvae were recovered from four 1-year-old pigs given 2,500 ML (n=2) or 10,000 ML (n=2). Viable larvae were also recovered from frozen black bear meat harvested at two additional locations, one in southern Ontario, Canada, and one in upstate New York, USA. Multiplex PCR using genomic DNA from these parasite samples demonstrated that both isolates were T. nativa. This is the first report of the freeze-resistant species, T. nativa, within the continental United States.

Comparison of two antigens for demonstration of Trichinella spp. antibodies in blood and muscle fluid of foxes, pigs and wild boars.

For the surveillance of trichinellosis, the digestion method is reliable but also labour intensive. The serological methods for the detection of Trichinella-specific antibodies using ELISA offer a sensitive and relatively specific alternative. For serological studies, sera or plasma from blood samples are the most common source of antibodies, but although the concentration of antibodies is approximately 10-fold lower, muscle fluid can be a good alternative particularly for testing of wildlife samples. In the present study, an indirect ELISA technique was evaluated on both sera and muscle fluids from experimentally infected foxes, pigs, and wild boars using both excretory/secretory (E/S) antigens and a synthetic glycan antigen, beta-tyvelose. Although the synthetic antigen appears to be less sensitive than the E/S antigens, Trichinella-specific IgG antibodies were detected in both serum samples and muscle fluid samples from pigs, wild boars and foxes infected at levels which would be important for food safety or represent a significant reservoir for further transmission.

Muscle distribution of sylvatic and domestic Trichinella larvae in production animals and wildlife.

Only a few studies have compared the muscle distribution of the different Trichinella genotypes. In this study, data were obtained from a series of experimental infections in pigs, wild boars, foxes and horses, with the aim of evaluating the predilection sites of nine well-defined genotypes of Trichinella. Necropsy was performed at 5, 10, 20 and 40 weeks post inoculation. From all host species, corresponding muscles/muscle groups were examined by artificial digestion. In foxes where all Trichinella species established in high numbers, the encapsulating species were found primarily in the tongue, extremities and diaphragm, whereas the non-encapsulating species were found primarily in the diaphragm. In pigs and wild boars, only Trichinella spiralis, Trichinella pseudospiralis and Trichinella nelsoni showed extended persistency of muscle larvae (ML), but for all genotypes the tongue and the diaphragm were found to be predilection sites. This tendency was most obvious in light infections. In the horses, T. spiralis, Trichinella britovi, and T. pseudospiralis all established at high levels with predilection sites in the tongue, the masseter and the diaphragm. For all host species, high ML burdens appeared to be more evenly distributed with less obvious predilection than in light infections; predilection site muscles harbored a relatively higher percent of the larval burden in light infections than in heavy infections. This probably reflects increasing occupation of available muscle fibers as larger numbers of worms accumulate. Predilection sites appear to be influenced primarily by host species and secondarily by the age and level of infection.