The retention and concentration of glycogen in Trichinella nativа in the winter-spring period

The metabolism of Trichinella spp. is primarily anoxybiotic in nature. Their main energy source is glycogen, which is stored in the stichocites at the muscular stage of the larval development. When subject to tow temperatures the Trichinella larvae consume glycogen and neutral fats to provide for basal metabolism until the energy supplies reach the critical level. The present study establishes the glycogen concentration as well the invasive activity of T. nativа when affected by low temperatures in natural conditions. The carcasses of infected laboratory rats were placed in containers beneath the snow cover, in the natural conditions of a game husbandry in Central Russia. The viability, invasive capacity and the glycogen level were monitored in the Trichinella larvae monthly. The invasive capacity of Trichinella larvae was established based on the presence of the larvae in the muscular tissue of laboratory mice after the peroral administration of the helminth larvae. On the 45 day of the experiment, the mice were euthanized by cervical dislocation, and if the Trichinella larvae could be discovered in the muscular tissue with the help of the trichinelloscopic compression method, the invasive capacity of the Trichinella larvae was viewed as positive. To establish the quantitative value of glycogen content in Trichinella larvae a modified method was used. In order to measure the glycogen level in the T. nativa larvae isolated by fermentation larvae were counted in one drop of the suspended sedimentation in the Migacheva-Kotelnikov chamber. To establish the quantitative value of glycogen content in Trichinella larvae a method based on the treatment of glycogen with iodine, optical density measurement with a refractometer MКMФ-02 was used. For the purpose of measuring the concentration of glycogen in Trichinella larvae in the suspended sedimentation a calibration curve was used. The studies showed that the viability indicator of the Trichinella larvae which had been preserved in natural conditions in the four months of the winter-spring period, in the muscular tissue of laboratory rats remained high (over 90 %). The glycogen concentration in one helminth larva was 0.041 μg in January, 0.033 μg in February, 0.015 μg in April. The invasive capability of the preserved Trichinella larvae was considerably reduced to 33.3 %. In the winter period, under temperatures below 0 °C, a decrease in the glycogen concentration in the Trichinella larvae was observed.

The vasculature of nurse cells infected with non-encapsulated Trichinella species

The vasculature surrounding the nurse cells of encapsulated Trichinella spiralis has been described previously. It has been postulated the function of these vessels is to support the growth of the parasite. We describe here for the first time the vasculature surrounding the nurse cells of non-encapsulated T. pseudospiralis and T. papuae. Similar to the vasculature of uninfected muscle cells, the vessels surrounding non-encapsulated Trichinella nurse cells are dense and branched longitudinally along the long axis of the muscle cells; they also appear to be similar in diameter. The netting pattern of enlarged vessels found around T. spiralis (encapsulated) nurse cells is not present in non-encapsulated Trichinella infections. The vessels surrounding non-encapsulated Trichinella nurse cells seem to exist prior to parasite invasion of the muscle cell.

Trichinella diagnostics and control: mandatory and best practices for ensuring food safety

Because of its role in human disease, there are increasing global requirements for reliable diagnostic and control methods for Trichinella in food animals to ensure meat safety and to facilitate trade. Consequently, there is a need for standardization of methods, programs, and best practices used in the control of Trichinella and trichinellosis. This review article describes the biology and epidemiology of Trichinella, and describes recommended test methods as well as modified and optimized procedures that are used in meat inspection programs. The use of ELISA for monitoring animals for infection in various porcine and equine pre- and post-slaughter programs, including farm or herd certification programs is also discussed. A brief review of the effectiveness of meat processing methods, such as freezing, cooking and preserving is provided. The importance of proper quality assurance and its application in all aspects of a Trichinella diagnostic system is emphasized. It includes the use of international quality standards, test validation and standardization, critical control points, laboratory accreditation, certification of analysts and proficiency testing. Also described, are the roles and locations of international and regional reference laboratories for trichinellosis where expert advice and support on research and diagnostics are available.

Experimental infections of baboons (Papio spp.) and vervet monkeys (Cercopithecus aethiops) with Trichinella zimbabwensis and successful treatment with ivermectin

Experimental Trichinella zimbabwensis infections were established in three baboons (Papio sp.) and four vervet monkeys (Cercopithecus aethiops) and the clinical-pathological manifestations assessed. The infected animals showed clinical signs ranging from fever, diarrhoea, periorbital oedema and muscular pain in varying degrees. One baboon became blind due to the infection. Levels of creatinine phosphokinase and lactate dehydrogenase increased to reach a peak on Day 42 post-infection (pi) for both baboons and monkeys. Blood parameters such as packed cell volume, levels of red blood cells and white blood cells did not change significantly from the normal ranges except for the levels of eosinophils which peaked above the normal ranges at Day 28 and 56 pi in baboons and at Day 56 pi in monkeys. Two baboons and two monkeys died during the course of the experiment. They were emaciated and showed lesions such as ascites, hydropericardium, congested liver and enlarged gall bladder. Histopathological findings of various muscles included a basophilic transformation of muscle cells, the disappearance of sarcomere myofibrils and basophilic sarcoplasm with the presence of Trichinella larvae in the sarcoplasm. These changes were mainly in the massetter and were of various intensities in the tail, gastrocnemius and biceps muscles. Five consecutive treatments with an oxfendazole-levamisole combination on surviving animals failed to clear the infection whereas ivermectin cleared the infection after one treatment in two monkeys and after two treatments in a baboon.

A probable case of human neurotrichinellosis in the United States

Human neurotrichinellosis is seldom reported. This is likely the result of the low incidence of parasites from the genus Trichinella in the United States domestic food supply, as well as difficulties in diagnosing the disease, especially when neither the organism nor the source of the infection are readily available. Although trichinellosis from domestic food supplies has been decreasing for many years, a resurgence has occurred in cases derived from the consumption of wild game. We report a rare case of neurotrichinellosis in the United States and implicate wild game as the source of the infection. These results suggest that clinicians should consider the potential for Trichinella infection in cases where wild game is common in the diets of the patients.

[Anti-Trichinella antibody level in muscle juice of experimentally infected mice]

OBJECTIVE

To detect the anti-Trichinella antibody level in muscle juice of experimentally infected mice and their correlation with serum antibodies.

METHODS

Two hundred and eighty-eight Kunming mice were randomly divided into 3 groups (96 mice each), each mouse was inoculated with 100, 300 or 500 muscle larvae of T spiralis, respectively. Anti-Trichinella antibodies in serum and muscle juice taken weekly up to 18 weeks post-infection (wpi) were detected by ELISA using T. spiralis muscle larval excretory-secretory (ES) antigens. Thirty mice were inoculated with T. spiralis muscle larvae(500 larvae each). The muscle samples taken in 6 wpi were kept in plastic containers and conserved at 4 degrees C for 7 days or at -20 degrees C for 20 weeks for detecting anti-Trichinella antibodies later.

RESULTS

Anti-Trichinella antibodies in muscle juice of the mice infected with 100, 300 or 500 larvae were detected in 4, 3 and 3 wpi, with antibody positive rate of 87.5%, 50% and 87.5% respectively. In the three groups of mice, the antibody positive rate of muscle juice increased gradually after infection and up to 100% in 6, 4 and 4 wpi, and the antibody level reached its peak in 8 wpi with an absorbance value of 0.43, 0.49 and 0.52 respectively. Thereafter, the antibody level decreased slightly, but the positive rate was still 100% and lasted to 18 wpi when the experiment was ended. The antibody level in muscle juice showed significant positive correlation with serum antibodies at different time intervals after infection in three groups (r100=0.940, r300=0.970, r500=0.983, P<0.05). The absorbance value of muscle samples conserved at 4 degrees C for 7 d and 1 d was the same (0.53) (F=0.250, P>0.05), and those conserved at -20 degrees C for 8 wk and 1 wk was 0.46 and 0.50 respectively, showing that the antibody level in muscle juice did not decreased considerably after the muscle samples were frozen at -20 degrees C for 8 weeks (F=2.273, P>0.05). The absorbance value of Trichinella-infected muscle conserved at -20 degrees C for 10 wk decreased to 0.43, with significant difference from that conserved at -20 degrees C for 1 wk, but the positive rate was also 100%, and antibodies were detected in all muscle samples conserved at -20 degrees C for 20 weeks when the experiment was ended.

CONCLUSION

When animals died or were slaughtered and serum samples could not be collected, muscle juice can be collected from fresh, cool and frozen meat and used as a substitute sample for detecting anti-Trichinella antibodies.

Trichinella in pork: current knowledge on the suitability of freezing as a public health measure

Nematodes of the genus Trichinella are the causative agents of trichinellosis, a potentially severe disease in humans. Raw or undercooked pork, horse and game meat (predominantly wild boar and bear) poses a health risk to consumers.

Trichinae certification in the United States pork industry

Control of Trichinella infection in U.S. pork has traditionally been accomplished by inspection of individual carcasses at slaughter or by post-slaughter processing to inactivate parasites. We propose that an alternative to individual carcass testing or processing can be used when pigs are raised in production systems where risk of exposure to Trichinella spiralis has been mitigated. Declines in prevalence of this parasite in U.S. domestic swine during the last 30 years, coupled with improvements in pork production systems, now allow Trichinella control to be shifted to the farm through implementation of specific pork production practices. Knowledge of risk factors for exposure of swine to T. spiralis was used to develop an objective audit of risk that can be applied to pork production sites. In a pilot study, 461 production site audits were performed by trained veterinary practitioners. The on-farm audit included aspects of farm management, bio-security, feed and feed storage, rodent control programs and general hygiene. Of the 461 production site audits, 450 audits (97.6%) indicated compliance with the required good production practices. These sites are eligible for certification under the U.S. Trichinae Certification Program and will be audited regularly to maintain that status. The described trichinae certification mechanism will establish a process for ensuring the Trichinella safety of swine, and ultimately food products derived from swine, at the production level.

Experimental studies in pigs on Trichinella detection in different diagnostic matrices

A total of 72 specific pathogen-free (SPF) and Iberian pigs (three animals per group) were inoculated with 200, 1000 or 20,000 muscle larvae of T. spiralis, T. nativa, T. britovi and T. pseudospiralis. For each animal, the muscle larva burden was evaluated in nine muscle samples by digestion. The anti-Trichinella IgG kinetics in blood samples, taken twice prior and at days 5, 10, 15, 20, 25, 30, 40, 50 and 60 post-inoculation, and in muscle juice, obtained at necropsy, was evaluated by an ELISA using an excretory/secretory antigen. The mean larval recovery rate in SPF/Iberian pigs corresponded with the level of inoculum dose, and tongue, diaphragm and masseter were identified as predilection muscles. In SPF and Iberian pigs receiving 20,000 larvae of T. spiralis, an earlier seroconversion was detected from day 25 post-inoculation. At a 10-fold dilution, the muscle juice showed a good test agreement with blood serum.

Re-emergence of trichinellosis in southeastern Europe due to political and economic changes

The countries of southeastern Europe including the Balkan region and bordering countries - Albania, Bulgaria, Bosnia and Herzegovina, Croatia, Greece, Hungary, Macedonia, Romania, Serbia and Montenegro, Slovenia, and the European part of Turkey - occupy a very important strategic position and represent a land bridge between Europe and Asia. In the majority of southeastern European countries, cases of trichinellosis among the human and animal populations were described in the late 19th or early 20th centuries. Trichinella infections among wildlife were also described in the aforementioned countries. Today, the prevalence of trichinellosis is different between the Balkans and bordering countries. A high prevalence of trichinellosis in domestic animals and humans has been reported in Bulgaria, Serbia and Montenegro, Romania and Croatia. A moderate prevalence was found in Bosnia and Herzegovina. In Hungary, human trichinellosis has not been present for a long period of time. However, sporadic cases were recorded in swine over the last 2 years. Trichinellosis has not been found among domestic animals and humans in Greece and Macedonia in recent years while in Turkey and Slovenia human trichinellosis is sporadic. The re-emergence of trichinellosis is connected with the changes in the social and political systems in Bulgaria and Romania. In Serbia and Montenegro as well in Croatia, however, a re-emergence of trichinellosis was due not only to political and social changes but also to wars that took place in these countries during the last years of the 20th century. Social, economic and political factors responsible for the re-emergence of trichinellosis in southeast European countries are discussed in this communication.

Anti-Trichinella antibodies detected in chronically infected horses by IFA and Western blot, but not by ELISA

In the Balkan countries, where trichinellosis is a re-emerging zoonosis, it is of great importance to determine Trichinella infection prevalence among the major hosts, including horses. One method for monitoring prevalence is serological surveillance; however, the validity of serological methods in horses is not well understood. The dynamics of anti-Trichinella IgG production and circulating excretory/secretory (ES) antigens were investigated in three horses experimentally-infected with Trichinella spiralis. Horses were slaughtered at 32 week post infection (p.i.). Low worm burdens were found in all three animals. Anti-Trichinella IgG was detected up to 32 weeks p.i. by an indirect immunofluorescence assay (IFA) and by Western blot (Wb), but not by ELISA. The ELISA test detected antibodies for only a short period of time (up to 18 weeks p.i. using ES antigen or up to 20 weeks p.i. using tyvelose-BSA antigen). The presence of circulating muscle larvae ES antigen in sera of infected horses was observed by dot blot from the 4th week p.i. up to the 32nd week p.i.

New trends and clinical patterns of human trichinellosis in Russia at the beginning of the XXI century

Official national statistics show a gradual decline in the incidence of trichinellosis in Russia from 971 cases in 1996 to 527 cases in 2002. Of the total 864 cases involved in 47 trichinellosis outbreaks during 1998--2002, only 35.8% were due to infected pork compared to 80% in 1995--1996. Other important sources were wild animals, such as bear (Ursus arctos) (39.5%), badger (Meles meles) (10.6%), and dog meat (11.9%). Children composed 15.9% of all cases. Overall, 81.0% of pork-cases occurred in the European part of the country, and 89.4% of bear-meat cases were from the Asian region where most of the badger and dog-meat cases also originated. The percent of clinically severe cases of disease derived from pork and from bear meat was 7.7% and 7.9%, respectively; the frequency of moderate cases from pork was significantly higher than from bear meat. Clinically severe cases from badger and dog meat were 1.1% and 1.9%, respectively, where the number of clinically moderate cases from badger meat was significantly larger than that from dog meat. A disturbing trend is the 52.3% of trichinellosis cases during 1998--2002 in Russia that were derived from wild animal meat, especially the clinically severe cases occurring among the aboriginal Siberian population. The contributing factors to the slow decline in trichinellosis incidence in Russia and to the increase in percentage of cases originating from wild animal meat are the distribution and consumption of veterinary-uncontrolled pork, poaching and distribution of wild animal meat, and the neglect of medical and civil regulations. These trends should be seriously evaluated by the institutions of health, education, and by the veterinary service.

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.

Red fox (Vulpes vulpes) cannibalistic behaviour and the prevalence of Trichinella britovi in NW Italian Alps

Food habits of the red fox (Vulpes vulpes) were studied in the Aosta Valley region (NW Italian Alps) and were related to the prevalence of Trichinella infection in the red fox itself and in two Mustelid species (the stone marten (Martes foina) and the badger (Meles meles)). The search of Trichinella by the automatic digestion of muscles samples led us to determine a prevalence of 3.5+/-1.2% in red foxes, 7.9+/-4.3% in stone martens and 1.9+/-1.8% in badgers, with no significant differences among the species. All larvae were identified as Trichinella britovi. The fox diet was assessed through the analysis of both faeces (n=180) and the stomach contents of road-killed animals (n=109). Our results confirmed the opportunistic feeding behaviour of the red fox, which is able to use various trophic resources, both of animal and vegetal origin: e.g. wild and cultivated fruits (F%=47.1; V%=67.3), rodents (F%=22.8; V%=64.8) and carrion (F%=15.6; V%=78.6) formed the bulk of the fox's diet. The frequency of occurrence of potential events of cannibalism was 1.0%, even if the complete absence of undigested remains, other than hairs, suggested the possibility of confusing cannibalism with coat-cleaning. We suggest that intra-specific necrophagy could not represent the unique way of transmission of the nematode in natural conditions.

Effects of raw biles and their non-protein fractions from fox, pig, sheep and chicken on the survival of Trichinella spp. in vitro

The in vitro differential effect of fox, pig, sheep and chicken bile and corresponding non-protein fractions at various concentrations on the motility of released muscle larvae of Trichinella spiralis, Trichinella nativa and Trichinella nelsoni was examined. In many cases, the percentages of motile (live) larvae of the three Trichinella species cultured in the presence of the non-protein fractions of bile from the study animals were significantly higher (p<0.001) compared to their respective control cultures. In addition, the percentages of motile (live) larvae of all Trichinella species cultured in the presence of the non-protein fraction of bile at every concentration from all study animals were significantly higher (p<0.001) compared to their respective cultures in the presence of raw bile. Not only did results with non-protein fractions of bile differ from those with raw bile, but also the non-protein fraction, with increased dilution, showed a decrease in the percentages of motile larvae while the opposite was true with the raw bile (p<0.001). These observations indicate that the non-protein fraction of bile prolongs the in vitro survival of larvae.

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.

Spatial Variation of Trichinella Prevalence in Rats in Finnish Waste Disposal Sites

Trichinellosis is 1 of the most widespread parasitic zoonoses in the world and can be lethal to humans. Trichinella spp. are also parasites of considerable economic importance. Because rats may play a role in the transmission of trichinellosis to swine and farmed wild boar, 767 brown rats (Rattus norvegicus Berkenhout) from 13 Finnish waste disposal sites were examined for Trichinella spp. by a HCl-pepsin digestion method. Trichinella spp. were found to be a common parasite in trapped rats (overall prevalence, 19%) detected in 12 of 13 dumps. Significant differences were observed between sites in the prevalence (0-49%) of Trichinella spp. Female rats were more often and more heavily infected than males, but age was not shown to be a risk factor for trichinellosis. In addition, positive correlation was demonstrated between rat population density and prevalence. Trichinella spiralis was identified by multiplex polymerase chain reaction in 28 rats. The median density of infection was 42 (range, 0.5-6,925) larvae/ g of host tissue, but neither the occurrence nor the density of the parasite was related to the physical condition of the animal.

[Trichinellosis outbreaks in Spain (1990-2001)]

INTRODUCTION

Trichinellosis is a helminth infection having a wide geographical distribution. It is acquired by ingestion of raw or undercooked meat infected with Trichinella spp. The present work reviews the human trichinellosis outbreaks recorded in Spain during 1990-2001, taking into account both the geographical distribution and source of the infection.

METHODS

The parasite was isolated from suspected meats with the digestion technique. Molecular characterization of Trichinella isolates was done by random amplified polymorphic DNA (RAPD) analysis and Western-blot with US5 and US9 monoclonal antibodies. Anti-Trichinella antibodies in the patients' sera were investigated by indirect immunofluorescence (IIF).

RESULTS

A total of 49 trichinellosis outbreaks were detected in Spain during 1990-2001, 75.5% produced by ingestion of infected wild boar, 14.3% by infected domestic pig and 10.2% by an unknown source. Of the 49 outbreaks, 21 were followed up in our laboratory. We were able to perform molecular identification of the Trichinella species involved in 13 outbreaks, with 61.5% produced by T. britovi and 38.5% by T. spiralis. Serological diagnosis of the trichinellosis patients by IIF allowed confirmation of helminth infection.

CONCLUSIONS

With the use of molecular markers, T. spiralis and T. britovi were identified as the causative organisms in trichinellosis outbreaks detected in Spain during 1990-2001. These results reveal the importance of T. britovi in Spanish public health.

Minor interspecies variations in the sequence of the gp53 TSL-1 antigen of Trichinella define species-specific immunodominant epitopes1

Among the Trichinella TSL-1 antigens, whose antigenicity is generally due mainly to tyvelose-containing epitopes, gp53 is unusual in that its antigenicity is due mainly to protein epitopes. In the present study we mapped two of these epitopes, recognized by monoclonal antibodies (mAbs) that specifically recognize gp53 from all encysting Trichinella species (mAb US9), or gp53 from Trichinella spiralis alone (mAb US5). Based on previously published sequences of this glycoprotein [Mol. Biochem. Parasitol. 72 (1995) 253], in this study, we cloned the full gp53 cDNA from a new strain, Trichinella britovi (ISS 11; AN: ), and from another T. spiralis isolate (ISS 115; AN: ). The gp53 sequence comprised an ORF of 1239bp, coding for 412 amino acids, with 61 nucleotide differences (resulting in 38 residue changes) between the two species. Mapping of US5- and US9-recognized epitopes was undertaken through the construction and expression in the pGEX4T vector of truncated gp53 peptides, and by the construction of peptides derived from the antigenic regions. The epitope recognized by mAb US9 was a linear peptide of 8 residues, 33Met- 40Ser, located in the amino-terminal region, while the corresponding epitope recognized by mAb US5 was a 47-amino acid sequence containing two alpha-helix regions flanked by random coils, 290Thr- 336Lys. Molecular modeling of these peptides seems to indicate that recognition of the US9 epitope depends on the presence of two available hydroxyl groups provided by one methionine and one serine on T. spiralis gp53 (not present on Trichinella pseudospiralis gp53). Additionally, the stability of the US5 epitope seems to depend on correct folding of the 47-amino acid sequence (only present in T. spiralis). The relevance of these findings for understanding the antigenic recognition of Trichinella TSL-1 antigens, and for further studies to investigate possible function(s) of gp53 in Trichinella, is discussed.

An outbreak of trichinellosis due to consumption of bear meat infected with Trichinella nativa, in 2 northern Saskatchewan communities

In June 2000, bear meat infected with Trichinella nativa was consumed by 78 individuals in 2 northern Saskatchewan communities. Interviews and blood collections were performed on exposed individuals at the onset of the outbreak and 7 weeks later. All exposed individuals were treated with mebendazole or albendazole, and symptomatic patients received prednisone. Confirmed cases were more likely to have consumed dried meat, rather than boiled meat (P<.001). Seventy-four percent of patients completed the recommended therapy, and 87% of patients who were followed up in August 2000 reported complete resolution of symptoms. This outbreak of trichinellosis was caused by consumption of inadequately cooked bear meat contaminated with T. nativa. Apart from clinical symptomatology, blood counts, creatine kinase levels, serology test results, and analysis of the remaining bear meat helped establish the diagnosis. Treatment with antiparasitic drugs and prednisone was beneficial in limiting the severity and duration of the illness.

Trichinellosis: old facts and new developments

Trichinellosis is a helminth zoonosis, which is known since long, but which is emerging or re-emerging in several regions of the world. During the last years the number of cases of trichinellosis in pigs and man in several East-European countries has increased very much due to the breakdown of the veterinary services because of the difficult political and socio-economic situation. In several third world countries on the other hand trichinellosis has become more important due to the increasing number of small traditional pig farms, in which the hygienic conditions are suboptimal. Furthermore, outbreaks of human trichinellosis have been reported due to recently discovered new species such as T. pseudospiralis and T. papuae. Over the last 25 years horsemeat has been more important as a source of human trichinellosis within the European Union than pork or wild boar meat. In Belgium, however, no cases of human trichinellosis have been reported since 1979. A review is presented of the available data on animal trichinellosis in Belgium. The potential risk for the consumer is discussed. Finally, some suggestions are made for a new approach of trichinellosis control in Belgium and the European Union.

Trichinellosis in China: epidemiology and control

The first outbreak of human trichinellosis in China, according to official national publication, was registered in Tibet in 1964. Since then, more than 500 outbreaks, numbering 25161 cases with 240 deaths, have been recorded. However, this reported quantity is probably highly underestimated because adequate diagnostic techniques might not have been available in the whole area. Moreover, infection in animals is widespread over China, with the prevalence of pig trichinellosis being as high as 4% in some provinces. The estimated situation of trichinellosis in China highlights the necessity not only for its control, but also for the government to elaborate new regulations and guidelines for animal inspection.

Oxidative, heat and anthelminthic stress responses in four species of Trichinella: comparative study

The aim of this study was to compare levels of stress proteins in four Trichinella species when exposed to different stressors. Heat shock protein (HSP) 60, 70 and 90 responses were evaluated in infective larvae (L(1)) of four classic Trichinella species following exposure to oxidative, anthelminthic and thermal stress. Larvae of T. nativa, T nelsoni, T. pseudospiralis and T. spiralis were exposed to peroxide shock (0.2%, 1%, or 2% H(2)O(2)for 2h), high temperatures (40 degrees C or 45 degrees C for 2h), or 0.1 microg/ml of the benzimidazole anthelminthics: mebendazole (MBZ), albendazole (ALB) or thiabendazole (TBZ) for 4h. Following exposures, the L(1) were tested for induced morphological changes. Those observed were: (i) no change (in all species exposed to 40 degrees C) (ii) aberrant forms (in all species exposed to anthelminthics, in T. nativa, T. nelsoni and T. spiralis exposed to 45 degrees C, and in T. spiralis and T. nelsoni exposed to 0.2% H(2)O(2)) and (iii) severe degradation or death (in T. nativa and T. pseudospiralis exposed to 0.2% H(2)O(2), and in all species at 1% and 2% H(2)O(2)). In Western blot analyses, L(1) proteins were probed with monoclonal antibodies (mAbs) specific for the three HSPs. Greater changes in HSP levels occurred following H(2)O(2) exposure than with other stresses in all Trichinella species, while accumulation of a 50 kDa HSP was only observed in T. spiralis and T. pseudospiralis. Anthelminthic stress only caused decreased HSP levels in T. nativa. Thermal stress caused no significant changes in the HSP response of any species. It is suggested that other stress proteins (e.g., glucose-regulated proteins) may be involved in adaptation to thermal stress.

Effects of Trichinella spiralis on survival, total mass, and organ mass of oldfield mice (Peromyscus polionotus)

Trichinella spiralis is a parasitic nematode that infects many mammals, including humans. Hosts may experience significant physiological changes or may die because of acute inflammatory immune responses toward the parasite. In this study, oldfield mice (Peromyscus polionotus) were used as a new experimental host for T. spiralis. Males of P. polionotus were infected with increasing doses of T. spiralis to determine the effect infection had on survival, mass change, total mass, and relative organ masses. Total juvenile worm burden increased in an asymptotic fashion with infective dose. Large doses (> or = 600 juveniles) significantly reduced survival. There were significant negative correlations between infection intensity (log10[juveniles]/g) and both mass gain and final total mass. Infection had no effect on liver or spleen size. But there were significant negative correlations between T. spiralis intensity and both testis and seminal vesicle masses. These effects on male size and reproductive organs may help explain behavioral changes, such as the elimination of male dominance, seen in previous studies on mice infected with T. spiralis.

Comparison of cholinesterase activities in the excretion-secretion products of Trichinella pseudospiralis and Trichinella spiralis muscle larvae

The presence of cholinesterases (ChE) is reported in T. pseudospiralis excretion-secretion products (ESP) by spectrophotometric method, using acetylthiocholine (ATCI) and butyrilthiocholine (BTCI) as substrates. By inhibition assays, we found that T. pseudospiralis release both acetyl- and butiryl-cholinesterases (AchE and BchE, respectively). The sedimentation coefficientes of these enzymes were determined by sucrose density gradient. We studied the in vivo ChE secretion by immunoblot assays using AchE from Electrophorus (electric eel) and sera from normal or infected mice with T. pseudospiralis or T. spiralis. The presence of anti-AchE antibodies was only demonstrated in the sera from T. pseudospiralis infected mice. Moreover the in vivo secretion was corroborated by the high difference determinate between the ChE activity of the immuno complexes from T. pseudospiralis infected sera and the immunocomplexes from T. spiralis infected sera as well as normal sera. Finally, we analyzed the effect of the organophosphate Neguvón (metrifonate) on the ChE activity from the T. pseudospiralis ESP. The drug inhibits in part this activity. Moreover Neguvón (metrifonate) showed a high activity against the T. pseudospiralis viability.

Expression of excretory and secretory protein genes of Trichinella at muscle stage differs before and after cyst formation

By adapting a semi-quantitative reverse transcriptase-PCR (RT-PCR) method, we investigated kinetics of gene expression at different developmental stages of Trichinella spiralis and T. pseudospiralis. The analyzed genes included four kinds of excretory and secretory (ES) proteins, a heat shock protein (HSP) and a DNA binding protein and showed that T. spiralis and T. pseudospiralis expressed ES proteins in a stage-specific manner. The gene encoding a 43 kDa ES protein was expressed by muscle larvae, either pre-cyst or post-cyst larvae. The genes encoding: the 53 kDa ES protein of T. spiralis; 53 kDa ES protein of T. pseudospiralis; and 19.6 kDa ES protein of T. spiralis were expressed by post-cyst larvae and adult worms, but not expressed by pre-cyst larvae or newborn larvae. The results showed that pre-cyst larvae and post-cyst larvae are similar but different in the expression of 53 and 19.6 kDa ES proteins. On the other hand, genes of housekeeping proteins, such as HSP and the DNA binding protein, were expressed at all stages although there were some differences in the expression level.

New aspects of human trichinellosis: the impact of new Trichinella species

Trichinellosis is a re-emerging zoonosis and more clinical awareness is needed. In particular, the description of new Trichinella species such as T. papuae and T. murrelli and the occurrence of human cases caused by T pseudospiralis, until very recently thought to occur only in animals, requires changes in our handling of clinical trichinellosis, because existing knowledge is based mostly on cases due to classical T spiralis infection. The aim of the present review is to integrate the experiences derived from different outbreaks around the world, caused by different Trichinella species, in order to provide a more comprehensive approach to diagnosis and treatment.

The effect of changes in the gastric pH value on experimental trichinosis

The effect of increasing or decreasing the gastric pH of mice on the course of experimental infection with Trichinella spiralis was studied, by administration of 1% NaHCO3 in PBS (pH 9.0) or 1% HCl in PBS (pH 5.0) to mice half an hour prior to infection respectively. The results revealed that raising the gastric pH led to a significant increase in the adult worm count with all increase in their fecundity both in vivo and in vitro. On on the other hand, the more acidic gastric pH induced prior to infection led to its amelioration. This was obvious by the significant reduction in the adult worm count and their inability to give birth to newborn larvae. Several factors may be incriminated, among which are decreased larval infectivity and affection of the maturation of the reproductive organs, mainly the uterus and the testis. Changes in their morphology were observed by both light and transmission electron microscopic studies, which could account for the impairment in their functions, namely embryogenesis and spermatogenesis.

New patterns of Trichinella infection

Human and animal trichinellosis should be considered as both an emerging and reemerging disease. The reemergence of the domestic cycle has been due to an increased prevalence of Trichinella spiralis, which has been primarily related to a breakdown of government veterinary services and state farms (e.g., in countries of the former USSR, Bulgaria, Romania), economic problems and war (e.g., in countries of the former Yugoslavia), resulting in a sharp increase in the occurrence of this infection in swine herds in the 1990s, with a prevalence of up to 50% in villages in Byelorussia, Croatia, Latvia, Lithuania, Romania, Russia, Serbia, and the Ukraine, among other countries. The prevalence has also increased following an increase in the number of small farms (Argentina, China, Mexico, etc.) and due to the general belief that trichinellosis was a problem only until the 1960s. The sylvatic cycle has been studied in depth at both the epidemiological and biological level, showing the existence of different etiological agents (Trichinella nativa, Trichinella britovi, Trichinella murrelli, Trichinella nelsoni) in different regions and the existence of "new" transmission patterns. Furthermore, the role of game animals as a source of infection for humans has greatly increased both in developed and developing countries (Bulgaria, Canada, Lithuania, some EU countries, Russia, USA, etc.). The new emerging patterns are related to non-encapsulated species of Trichinella (Trichinella pseudospiralis, Trichinella papuae, Trichinella sp.), infecting a wide spectrum of hosts (humans, mammals including marsupials, birds and crocodiles) and to encapsulated species (T. spiralis, T. britovi, and T. murrelli) infecting herbivores (mainly horses). The existence of non-encapsulated species infecting mammals, birds and crocodiles had probably remained unknown because of the difficulties in detecting larvae in muscle tissues and for the lack of knowledge on the role of birds and crocodiles as a reservoir of Trichinella. On the other hand, it is not known whether horse and crocodile infections existed in the past, and their occurrence has been related to improper human behavior in breeding. The problem of horse-meat trichinellosis is restricted to France and Italy, the only two countries where horse-meat is eaten raw, whereas mutton and beef have been found to be infected with Trichinella sp. only in China.

Secretion of the novel Trichinella protein TSJ5 by T. spiralis and T. pseudospiralis muscle larvae

The Trichinella tsJ5 gene is preferentially expressed in muscle larvae of Trichinella spiralis and encodes a novel protein. Previous observations have shown tsJ5 to be expressed at higher levels in encapsulating species than in non-encapsulating species and down-regulation of gene expression in T. pseudospiralis to be correlated with a lower protein abundance in the muscle larva of this species. In the present study we have determined the full-length cDNA sequence of the tsJ5 homologue in T. pseudospiralis (tpJ5). Antigens recognised by an anti-J5 antibody are found on the cuticular surface of both T. spiralis and T. pseudospiralis muscle larvae, as well as in the body wall muscle. We show that both the TSJ5 and TPJ5 proteins are found in the excretory/secretory fractions collected from muscle larva cultured in vitro and that despite the absence of a typical N-terminal signal sequence, secretion of pTSJ5 is mediated through the classical ER/Golgi secretory pathway.

Trichinella spp. in ostrich meat: a public health risk?

In the present work the biological behaviour of T. spiralis and T. pseudospiralis in ostriches is reported. Oral infections were performed in eight ostriches with two infective doses (10,000 and 80,000 larvae) for each species of Trichinella. On day 0, 30 and 60 p.i. blood samples were collected to assay the serum changes concerning specific muscle enzyme activities and total proteins. The immunological study, to determine specific IgG in sera, was conducted employing a monoclonal blocking ELISA. From the carcasses of sacrificed animals, samples of various muscle tissues were examined by the digestion method and by standard histopathologic procedures. The study showed a low susceptibility of the ostriches to T. pseudospiralis; preferential sites of larval distribution were muscle tissues of the legs. T. spiralis could be found in muscle tissues only when a high number of larvae were inoculated. Immunological reactivity was found only in animals infected with higher doses of T. pseudospiralis.

Principles of contemporary treatment in trichinellosis

Principles of trichinellosis treatment were presented, based on contemporary parasitologic and clinical criteria. Significance of the Trichinella sp. life cycle, phase of the invasion and the disease was presented. The role of anthelmintics was stressed, as drugs of choice in eradication of the intestinal phase and in prevention against development of the muscular phase. Role of glucocorticoids was described in suppression of acute clinical signs/symptoms. Pathology of the late period oftrichinellosis and of the late invasion sequele were discussed.

The distribution of excretory/secretory antigens during the muscle phase of Trichinella spiralis and T. pseudospiralis infections

The in situ distribution of excretory/secretory (ES) antigens of the infective-stage larvae of Trichinella spiralis and T. pseudospiralis was compared at various periods of development by immunofluorescent laser confocal microscopy and the immunoperoxidase method. In the former infection, epitopes of the ES antigens were always confined exclusively within the nurse cell, i.e., in the cytoplasmic region, hypertrophic nuclei, stichocytes, and cuticular surface of worms. In the latter infection, as early as at day 15 postinfection, ES epitopes were located along the infected myofibers, in the adjacent muscles, hypertrophic nuclei, stichocytes, and cuticular surface of worms. By day 30 postinfection there was a marked increase in both the distribution and the intensity of ES antigens in infected as opposed to uninfected myofibers. A new method was also developed to reveal the number of hypertrophic nuclei, small cells, and larvae in intact nurse cells. As many as four worms could be accommodated within a single complex. The number of hypertrophic nuclei within each complex varied from 15 to 81.

Trichinella papuae n.sp. (Nematoda), a new non-encapsulated species from domestic and sylvatic swine of Papua New Guinea

Encapsulated and non-encapsulated species of the genus Trichinella are widespread in sylvatic animals in almost all zoogeographical regions. In sylvatic animals from Tasmania (Australian region), only the non-encapsulated species Trichinella pseudospiralis has been reported. Between 1988 and 1998, non-encapsulated larvae of Trichinella were detected in five domestic pigs and six wild boars from a remote area of Papua New Guinea. Morphological, biological, and molecular studies carried out on one strain isolated from a wild boar in 1997 suggest that these parasites belong to a new species, which has been named Trichinella papuae n.sp. This species can be identified by the morphology of muscle larvae, which lack a nurse cell in host muscles, and whose total length is one-third greater than that of the other non-encapsulated species, T. pseudospiralis. Adults of T. papuae do not cross with adults of the other species and genotypes. Muscle larvae of T. papuae are unable to infect birds, whereas those of T. pseudospiralis do. The expansion segment V of the large subunit of the ribosomal DNA differs from that of the other species and genotypes. All of these features allow for the easy identification of T. papuae, even in poorly equipped laboratories. The discovery and identification of a second non-encapsulated species in the Australian region strongly supports the existence of two evolutionary lines in the genus Trichinella, which differ in terms of the capacity of larvae to induce a modification of the muscle cell into a nurse cell.

Infectivity of Trichinella sp. isolated from Crocodylus niloticus to the indigenous Zimbabwean pig (Mukota)

An experimental infection of the indigenous Zimbabwean pig (Mukota) with a Trichinella sp. derived from crocodile (Crocodylus niloticus) was performed. The same larval isolates of Trichinella were infected to rats as a control. The muscles of both pigs and rats were found to be heavily infected with the first-stage larvae. The present study constitutes the first report of a successful experimental infection of the pig with Trichinella sp. originating from crocodile.

Cloning and characterization of Rab and Ran/TC4 cDNA clones in Trichinella spp

The cloning and characterization of seven Rab and three Ran/TC4 partial cDNA sequences in both cystic (Trichinella spiralis and T. britovi) and noncystic species (T. pseudospiralis) are reported. These molecules were cloned by rapid amplification of cDNA ends via polymerase chain reaction (RACE-PCR), using cDNA from the aforementioned Trichinella spp. coupled to the AP1 adaptor. As primers, AP1 and 5B (derived from the WDTAGQE sequence of region 2 specific for Rab and Ran proteins) sequences were included in the PCR. The cloned cDNAs were sequenced and characterized by both Southern-blot and Northern-blot analysis. Trichinella spp. Rab- and Ran-like molecules showed divergences in both the nucleotide and the deduced amino acid sequences as compared with the corresponding homologues previously described in other organisms. In addition, differences were observed among the Trichinella species, mainly between the cystic and the noncystic species, in both DNA restriction-enzyme polymorphism and expression of the six GTPases isolated.

A panel of antigens of muscle larvae of Trichinella spiralis and T. pseudospiralis as revealed by two-dimensional western blot and immunoelectron microscopy

This study characterized antigens of Trichinella spiralis and T. pseudospiralis muscle larvae recognized by mice infected with the worms. Two-dimensional (2-D) Western blot analysis revealed some profile of antigenic peptides including: (1) molecular weight (MW); (2) isoelectric points (pI), (3) reactivity to well-defined monoclonal antibodies (mAb) and (4) cross-reactivity between the 2 species. Antigenic peptides of T. spiralis consisted of about 100 spots. The MW ranged from 22 to 80 kDa, and pI ranged from 4 to 7. The mAb against TSL-1 stained most of the T. spiralis excretory-secretory (E-S) peptides migrating at 40, 45 and 50 kDa, and the mAb against TSL-4 stained non-E-S peptides. Antigenic peptides of T. pseudospiralis consisted of about 20 to 30 peptide spots. The MW ranged from 25 to 80 kDa, and pI ranged from 4 to 7. The mAb against TSL-1 stained most of the T. pseudospiralis E-S peptides migrating at 35 and 45 kDa, and the mAb against TSL-4 stained non-E-S peptides. Two-dimensional Western blots showed that the E-S products of T. spiralis and T. pseudospiralis were highly cross-reactive with each other. The non-E-S peptides were, however, not recognized by T. pseudospiralis-infected sera but were recognized by T. spiralis-infected sera. An immunoelectron microscopical study showed the similar result that stichocyte granules and cuticle surface (known to contain E-S antigen) had cross-reactive antigens between the two species. T. pseudospiralis-infected sera stained very weakly the cuticle inner layers and haemolymph (known to contain non-E-S antigen). This evidence implies that mice infected with T. pseudospiralis do not evoke antibodies against non-E-S antigen at the detectable level.

Evaluation of the infectivity of Trichinella spp. for reptiles (Caiman sclerops)

Experimental inoculation with nine well-characterised Trichinella isolates was performed on caimans (Caiman sclerops) to determine their infectivity for reptiles belonging to the family Crocodilidae. As controls, the same larval batches of Trichinella isolates were inoculated into mice and guinea pigs. It was suggested that Trichinella pseudospiralis was more likely to infect reptiles than encapsulating species, but whereas all Trichinella species established in mice and guinea pigs, the caimans remained negative. The finding that caimans could not be experimentally infected contrasts with a recent report on infections in farmed crocodiles (Crocodylus niloticus).

Trichinella pseudospiralis: X-ray analysis of the infected muscle cells and the muscle larva compartments after exponential growth of the larva in situ

The distribution of nutrients such as Na, Cl, K, P, S, and Ca was investigated by energy-dispersive X-ray microanalysis (EDXA) on bulk-frozen mouse muscles infected with Trichinella pseudospiralis. In an attempt to gain information as to whether muscle larvae would modify the element status within muscles of their host. Significant increases in phosphorus concentrations within nurse cells and internal cells of the larva, e.g., the somatic muscle cells and the stichocytes, were shown. This could reflect changes in the energy metabolism and/or in the turnover of nucleic acids of the nurse cell. High phosphorus concentrations within the internal larva cells corresponded to high levels of expression of thymidylate synthase shown elsewhere in both T. pseudospiralis and T. spiralis muscle larvae, most likely reflecting more intensive DNA replication. Furthermore, the Na+-concentration gradient between the nurse cell and neighboring host muscle cells indicated the plasma membrane as a diffusion barrier for Na+. Moreover, the cuticle seemed to maintain the Cl--concentration gradient between the nurse cell and the internal cells of the larva. Nevertheless, the mechanisms involved in the transport of both ions, the collagen cuticle appeared, strong permeability that serves the transcuticular transport maintaining the Cl--concentration gradient.

Differences and similarities between Trichinella spiralis and T. pseudospiralis in morphology of stichocyte granules, peptide maps of excretory and secretory (E-S) products and messenger RNA of stichosomal glycoproteins

The ultrastructure of muscle larvae of Trichinella pseudospiralis was studied by electron microscopy. The overall structure of muscle larvae of T. pseudospiralis resembled that of T. spiralis except for the stichocyte granules. T. pseudospiralis had at least 3 kinds of stichocyte granules distinguishable from each other by their shape, size and inclusions. The granules had some resemblance to alpha granules or beta granules of T. spiralis, but no resemblance to gamma granules. In favour of these morphological differences and similarities among T. spiralis and T. pseudospiralis, excretory and secretory (E-S) products (originating from stichocyte granules) of the 2 species differed to some degree. In an analysis by 2-dimensional electrophoresis, some peptide spots migrating at 45 kDa were shared by the 2 species but the other spots were unique to each of the 2 species. Messenger RNA encoding the 43 kDa glycoprotein of stichocyte granules was detected in the muscle larvae of both species but mRNA encoding the 53 kDa glycoprotein was detected only in muscle larvae of T. spiralis.

Characterization of eleven antigenic groups in Trichinella genus and identification of stage and species markers

Several monoclonal antibodies (Mabs) were raised against the L1 muscle stage (L1M) of Trichinella spiralis (Ts) and Trichinella pseudospiralis (Tp). Western blot analysis of various antigenic preparations established that Mabs described by different authors recognized 8 antigenic fractions (TSL1-TSL8) in crude extracts of infective larvae. The TSL1 fraction was immunodominant and present on the cuticle of different parasite stages. Mabs against Trichinella T5 (T5) and Ts were selected in order to extend the previous studies to another Trichinella phenotype. Only 35% of the selected Mabs recognized linear epitopes and 71% reacted with soluble or excretory-secretory antigens in a dot blot procedure and ELISA test. The targets of the Mabs were identified by immunoprecipitation with [35S]methionine-labelled L1M worm lysate. Mabs prepared from mice immunized with the whole parasite (T5) recognized a wider panel of antigens in different parasitic organs. Seven antigenic structures were distinguished on the cuticle and several epitopes were identified in the gut, haemolymph and stichocytes. Eleven antigenic groups were established according to their indirect immunofluorescence pattern on cross-sections of the worm. Monoclonal antibodies raised against Ts soluble antigen mainly recognized epitopes in stichocytes and on the cuticle surface. All the selected Mabs recognized T5 and Trichinella britovi (Tb) strengthening the link between these 2 species. Four Mabs were used to differentiate antigenic structures among 6 Trichinella phenotypes and to develop a new tool to follow gene flow within the Trichinella genus.

Trichinosis

Trichinosis is a worldwide zoonotic disease closely related to cultural and dietary habits caused by a nematode Trichinella spp. Human infection is acquired through ingestion of undercooked meat containing infective encysted larvae. There are two cycles of transmission, one domestic and the other wild. A complete life cycle develops in a single host harboring adult worms in the small intestine, from which newborn larvae migrate and finally encyst in striated muscle. Traumatic and immunological alterations are responsible for the main clinical features, including diarrhea, febrile syndrome, myalgias, oculopalpebral signs and eosinophilia. Cardiovascular, lung and CNS involvement characterize severe trichinosis. CNS inflammatory infiltration and damage may result from larval migration and vascular obstruction, or from the effect of toxic parasite antigens, or eosinophil infiltration. Humoral and cellular immune host response are relevant both to protect against re-infection and for immunodiagnosis. DNA probes and PCR technology may help to identify Trichinella spp. Muscle biopsy may disclose T spiralis larvae coiled within a muscle fibre host nurse cell surrounded by a capsule. Inflammatory infiltration includes monocytes, plasma cells, eosinophils and T lymphocytes mainly of the suppressor/cytotoxic phenotype. Histological appearance and histochemical profile of the host nurse cell differ from that of striated muscle fibre and are partly indicative of regeneration. Our own histological and histochemical findings in experimental studies of infected mouse muscle support the concept that changes induced by the larva encysting within a single host skeletal muscle fibre which becomes a nurse cell are unique of Trichinella infection. Interestingly, no dystrophin could be detected within the host nurse cell-capsule interface. It has been advanced that larva-induced host muscle fibre changes may be regulated at muscle gene transcription level whilst host regulatory pathways governed by cell cycle phase may also contribute to larval development.

[Updates on equine trichinellosis]

Trichinellosis is a zoonosis caused by parasites of the genus Trichinella. Transmission of trichinellosis to humans has been shown to occur mainly by the ingestion of meat from pigs, bears of foxes parasitized with muscle larvae of this parasite. However, in Europe, the major human outbreaks of the disease have occurred due to the ingestion of parasitized horse meat. Although the larvae were not isolated from the horse meat, the identification of larvae as T. nativa, T. britovi and T. spiralis was done in biopsy samples obtained from infected individuals. More recently T. spiralis muscle larvae have been isolated and identified, for the first time, in muscle tissue of horses slaughtered at an abattoir in the State of Mexico. Furthermore, in ELISA assays using total extracts or TSL-1 antigens, circulating antibodies against Trichinella have been detected in horses slaughtered at abattoirs from various countries in Europe and Mexico. On the other hand, the experimental infection of horses with parasites of the genes Trichinella has been achieved by several research groups and data obtained regarding the kinetics of antibody production in these animals are important in the development of sensitive and specific diagnostic assays for horse trichinellosis. This will allow to determine the frequency of this infection in horses which are used for animal and human feeding. These assays will also be very helpful for designing strategies to control transmission on the disease by horse meat.

The effect of Trichinella spiralis and Trichinella pseudospiralis on the mechanical properties of mammalian diaphragm muscle

The isometric mechanical properties of diaphragm muscle were studied in mice infected with either Trichinella spiralis or Trichinella pseudospiralis. Measurements of muscle stress were taken at 15, 20, 30 and 40 days post-infection. Infected diaphragm muscle showed a significant (P < 0.001) reduction in muscle stress during both twitch and tetanic contractions when compared with muscle from control animals. T. spiralis caused a significant reduction in resistance to muscle fatigue. The consequences of these changes in muscle function to host pathology are discussed, and related to previous work on the effects of Trichinella on host biochemistry and the immune response.

Biochemical investigations of the dynamics of proteinase activity at different stages of trichinellosis in mice

In the literature available hitherto there are many reports on enzymatic changes in tissues and a correlated rise in enzymatic activity in blood serum during experimental and human trichinellosis. In this study we were characterised proteinase activity in crude extracts from muscles of mice infected with Trichinella spiralis and T. pseudospiralis and the dynamics of their changes in different stages of disease. The activity of proteinase in muscle of mice infected with T. spiralis showed an increase in the 1st-5th week post infection, and then a slight decrease. The biggest proteinase activity was observed in 5th-6th week post infection. In the muscle of mice infected with T. pseudospiralis the increase of proteinase activity was observed in 1st-4th week post infection. In the 4th week the activity reached its maximum and in the 5th-10th week post infection there was a decrease of the activity in comparison with the control. As we could see, the dynamics of the changes of proteinase activity in mice is similar in the case of the disease with other biochemical and immunological indices observed in trichinellosis and with the increase of regeneration and transformation processes observed in histopathological studies.

Enteral and parenteral phases of Trichinella nativa and Trichinella pseudospiralis in the deer mouse, Peromyscus maniculatus

Trichinella nativa and Trichinella pseudospiralis infections in a wild rodent host, the deer mouse (Peromyscus maniculatus), were characterized. Forty-six percent of 400 inoculated T. nativa were recovered on day 4 postinoculation (PI); 77% and 23% were found in the small and large intestines, respectively. Thirty-one percent of the worms recovered on day 4 remained in the large intestine beyond day 20 PI. Worms were embedded in the mucosa of the small intestine, cecum, and colon. Females recovered from the small and large intestines had statistically indistinguishable in vitro larval releases. Distension of the cecum and passage of loose stools were associated with the presence of worms in the large intestine. The ability of T. nativa to establish and thrive in the large intestine of deer mice was confirmed following intracecal implantation of first-stage larvae. On day 4 PI, 35% of 400 inoculated T. pseudospiralis were recovered, with 91% and 9% found in the small and large intestines, respectively. Although T. pseudospiralis established in the large intestine of deer mice, few worms remained beyond day 20. Females recovered from the small and large intestines had statistically indistinguishable in vitro larval releases. Although higher establishments of T. nativa (56% vs. 46%) and T. pseudospiralis (52% vs. 35%) were observed in CD-1 mice than in deer mice on day 4 PI, neither was able to colonize the large intestine of the former. The large intestine may be a more important habitat for adult trichinae than previously recognized.

The prevalence of Trichinella sp. in Arctic foxes (Alopex lagopus) in Svalbard

The prevalence of Trichinella sp. in arctic foxes (Alopex lagopus) from Svalbard was studied from 1983 to 1989. Diaphragms of 697 foxes were examined for larvae; 59 foxes (8.5%) were infected. The prevalence of Trichinella sp. increased from 4% in juveniles to 36% in foxes aged more than 6 years of age. There were no significant correlations when condition and body weight each were correlated to the occurrence and number of larvae of Trichinella sp. More foxes were infected in the northern than in the central part of Svalbard. There were only minor differences in prevalence among years.