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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. [ABSTRACT FROM AUTHOR]

North American genotypes of Trichinella spiralis (T-l), 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-I, 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. [ABSTRACT FROM AUTHOR]

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-HC1 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 l-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. [ABSTRACT FROM AUTHOR]

Retail meat cuts of pork are frequently enhanced with salt solutions to improve flavor and texture and to extend shelf life through reductions in microbial contamination. A study of the effect of commonly used meat enhancement solutions on the viability of Toxoplasma gondii tissue cysts was performed using tissues from experimentally infected mice and pigs. Brains of T. gondii-infected mice were injected to 110% of the original weight of the brain with solutions containing sodium chloride (1 and 2%), sodium diacetate (0.1 and 0.2%), sodium tripolyphosphate (0,25 and 0.5%), potassium lactate (1.4 and 1.96%), or sodium lactate (1.4, 1.5, and 2.0%) alone or in combination and stored at 4°C for 7 days before feeding to T. gondii--seronegative cats. Loins were collected from pigs experimentally infected with T. gondii and injected as above and stored for 7, 28, or 45 days at 4°C before feeding to T. gondii-seronegative cats. Cat feces were examined for 14 days to assess oocyst shedding. The present study demonstrated that injection of mouse brains or pork loins with solutions containing 2% sodium chloride or ⩾ 1.4% potassium or sodium lactate, alone or in combination with other components, prevented transmission of T. gondii to cats. [ABSTRACT FROM AUTHOR]