Trichinella spiralis: effects on the host-parasite relationship in mice of BCG (attenuated Mycobacterium bovis).

The effects of BCG (Bacillus Calmette-Guérin, i.e., attenuated Mycobacterium bovis) on the host-parasite relationship in murine trichinosis were examined. A total of 2 × 10⁷ colony forming units of BCG given iv 1 week prior to Trichinella spiralis infection delayed the expulsion of adult worms from the gut. The suppression of adult worm elimination was proportional to the dose of BCG given. This finding was associated with a reduction in the degree of partial villous atrophy induced in the small bowel by T. spiralis. Adult female worms were fecund when they were examined 1, 2, and 3 weeks after infection of mice with T. spiralis. Despite the prolongation of fecund adult worms in the gut, there were no significant differences in muscle larval counts 4 and 6 weeks after infection. When newborn larvae were cultivated in vitro and injected iv, there was a significant 25% reduction in larval numbers recovered from the muscles of BCG-treated mice 4 weeks later. The administration of BCG had no effect on the inflammatory reaction around larvae in the muscles 4 and 6 weeks after infection. It is concluded that BCG alters the host-parasite relationship producing retention of adult worms in the gut, reduction in the severity of partial villous atrophy, and increased nonspecific resistance to the systemic larval phase of this parasite.     

Adoptive transfer of immunity to Trichinella spiralis in mice: generation of effective cells by different life cycle stages

Adoptive transfer of immunity with day 8 mesenteric lymph node cells (MLNC) taken from NIH mice after a chemically abbreviated infection of 3 days duration was as effective as transfer with cells taken from mice which had received an uninterrupted infection. Using a surgical transplantation technique it was demonstrated that adult T. spiralis were not capable of stimulating cells effective upon adoptive transfer. The potent immunogenicity of the early stages of infection was emphasized by data showing that very low numbers of muscle larvae were efficient in stimulating effective mediator cells. Neither the time at which MLNC were taken for transfer after transplantation of adult worms nor the age of adult worms transplanted affected the failure of this life cycle stage to stimulate cells capable of mediating worm expulsion. It is proposed that expulsion of T. spiralis from the gut may be achieved by more than one effector mechanism, and that early and late intestinal stages stimulate these mechanisms differentially.     

Trichinella spiralis: mediation of the intestinal component of protective immunity in the rat by multiple, phase-specific, antiparasitic responses.

Rats infected orally with Trichinella spiralis developed an immunity that was induced by and expressed against separate phases of the parasite's enteral life cycle. Infectious muscle larvae generated an immune response (rapid expulsion) that was directed against the very early intestinal infection and resulted in the expulsion of worms within 24 hr. This response eliminated more than 95% of worms in an oral challenge inoculum. Developing larvae (preadults) also induced an immune response that was expressed against adult worms. The effect on adults was dependent upon continuous exposure of worms to the immune environment throughout their enteral larval development. Immunity induced by preadult T. spiralis was not expressed against adult worms transferred from nonimmune rats. While adult worms were resistant to the immunity engendered by preadults they induced an efficient immunity that was autospecific. Both “preadult” and “adult” immunities were expressed in depression of worm fecundity as well as in the expulsion of adults from the gut. However, the two reactions differed in respect to their kinetics and their efficiency against various worm burdens. Preadult immunity was directed mainly against fecundity whereas adult immunity favored worm expulsion. All responses (rapid expulsion, preadult and adult immunity, and antifecundity) acted synergistically to produce sterile immunity against challenge infections of up to 5000 muscle larvae. These findings indicate that the host protective response to T. spiralis is a complex, multifactorial process that operates sequentially and synergistically to protect the host against reinfection.     

Therapeutic Potential of Myrrh and Ivermectin against Experimental Trichinella spiralis Infection in Mice

Trichinosis is a parasitic zoonosis caused by the nematode Trichinella spiralis. Anthelmintics are used to eliminate intestinal adults as well as tissue-migrating and encysted larvae. This study aimed to investigate the effects of ivermectin and myrrh obtained from the aloe-gum resin of Commiphora molmol on experimental trichinosis. Ninety albino mice were orally infected with 300 T. spiralis larvae. Drugs were tested against adult worms at day 0 and day 5 and against encysted larvae on day 15 and day 35 post-infection (PI). Mature worms and encysted larvae were counted in addition to histopathological examination of muscle specimens. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), total protein, albumin, globulin, urea, and creatinine values were estimated. Significant reductions in mean worm numbers were detected in ivermectin treated mice at day 0 and day 5 PI achieving efficacies of 98.5% and 80.0%, while efficacies of myrrh in treated mice were 80.7% and 51.5%, respectively. At days 15 and 35 post-infection, ivermectin induced significant reduction in encysted larval counts achieving efficacies of 76.5% and 54.0%, respectively, while myrrh efficacies were 76.6% and 35.0%, respectively. AST, ALT, urea, and creatinine levels were reduced, while total proteins were increased in response to both treatments compared to their values in the infected non-treated mice. Ivermectin use for controlling T. spiralis could be continued. Myrrh was effective and could be a promising drug against the Egyptian strains of T. spiralis with results nearly comparable to ivermectin.     

Trichinella spiralis: Delayed rejection in mice concurrently infected with Nematospiroides dubius

The immune response of mice to the nematode Trichinella spiral's was markedly altered when the infection was superimposed upon an existing infection with Nematospiroides dubius. The expulsion of a primary infection of T. spiralis was delayed in such mice, and the worms persisted for at least 4 weeks longer than they did in control mice. The degree to which expulsion was suppressed was related to the number of N. dubius present. It would appear that both adult and larval stages of N. dubius can exert a suppressive effect, since the expulsion of T. spiralis was affected within days of a super-imposed (i.e., larval) N. dubius infection. When adult N. dubius were removed from mice 4 days before infection with T. spiralis, the mice expelled the latter parasite within the normal time, indicating that recovery from the suppressive effects of concurrent infection occurred rapidly. Concurrent infection with N. dubius appeared to affect both the afferent and efferent arms of the immune response to T. spiralis, since sensitization by, and memory of, prior infection were impaired and the expression of acquired immunity was inferior to that of controls.     

Trypanosoma musculi and Trichinella spirails: Concomitant infections and selection for resistance genotypes in mice

Trypanosoma musculi infections were given to mice of different strains before, at the same time, and after an infection with 400 Trichinella spiralis. Examined parameters of the host response to T. spiralis were worm rejection, antifecundity responses, development of immunological memory, and muscle larvae burden. After dual infection, each mouse strain showed characteristic effects on resistance to T. spiralis. This was due to a dynamic interaction between the genes controlling rejection of T. spiralis and those influencing T. musculi growth. C3H mice develop high trypanosome parasitemias. This impairs worm expulsion and the development of memory to T. spiralis when Trypanosoma infections take place on the same day or 7 days before. The C57B1/6 mouse develops low parasitemias and T. musculi infections on the same day, or 7 days before T. spiralis, delaying worm rejection only slightly despite the overall weak capacity of B6 mice to expel worms. NFR-strain mice are strong responders to T. spiralis and also develop low parasitemias. Trypanosome infections on the same day, or after T. spiralis, produce a delay in worm rejection; the former is comparable to C3H mice. However, NFR mice alone showed enhanced rejection of worm when T. musculi infections preceded T. spiralis by 7 days. An unusual feature of C3H mice was that T. musculi infections 7 days before T. spiralis increased antifecundity responses at the same time that worm expulsion was inhibited. Trypanosome infections can therefore modulate distinct antihelminth immune responses in different directions simultaneously. The different outcomes of dual infections compared with single infections provides another selective mechanism by which genetic polymorphisms can be established and maintained in the vertebrate host.     

Eimeria nieschulzi and Trichinella spiralis: Analysis of concurrent infection in the rat

The effects of concurrent primary infection of the rat with Eimeria nieschulzi and Trichinella spiralis on the number of oocysts of E. nieschulzi shed by the host and on the number, distribution, and fecundity of adult T. spiralis were analyzed. When rats were initially infected with E. nieschulzi followed 9 days later by infection with T. spiralis there occurred a significant decrease in the total numbers of adult worms in the small intestine, a significant shift in the position of these worms along the length of the small gut, a decrease in the fecundity of adult female worms, and a decrease in muscle parasitism when compared with rats infected with T. spiralis alone. When rats were initially infected with T. spiralis, followed 9 days later by infection with E. nieschulzi, there occurred a significant decrease in the numbers of oocysts shed over 24 hr on Days 7, 9, and 11 postinfection below that seen with rats infected only with Eimeria. These changes are discussed in terms of the enteropathophysiologic lesions and enteric inflammation known to occur during infections with these two parasites.     

Comparison of rapid expulsion of Trichinella spiralis in mice and rats

Alizadeh H. and Wakelin D. 1982. Comparison of rapid expulsion of Trichinella spiralis in mice and rats. International Journal for Parasitology12: 65–73. Primary infections of Tricliinella spiralis in both NIH mice and Wistar rats resulted in increased levels of mucosal mast cells and goblet cells. In mice the numbers of both cell types rose sharply before worm expulsion (days 8–10), remained at an increased level for a short time and declined quickly, reaching control levels on day 14 for goblet cells and between days 28 and 35 for mast cells. In contrast, in rats, the numbers of goblet cells and mast cells increased during worm expulsion and remained above control levels for a prolonged period. Challenge infections given shortly after expulsion of a primary infection (day 14) were expelled rapidly, worm loss being virtually complete with 24 h. In mice this response to challenge was short-lived and persisted only until day 16 after primary infection. After this time, challenge worms were expelled more slowly after infection. In rats the rapid expulsion response was expressed for at least 7 weeks after primary infection. Mice and rats showed differences in the conditions of infection necessary to prime for rapid expulsion, mice requiring larger and longer duration primary infections, but the expression of the response appeared to be similar in both species. In mice it was shown that rapid expulsion of T. spiralis was a response evoked specifically by prior infection with this species; infections with other intestinal nematodes had no effect. Similarly, the effect upon challenge infection was also specific to T. spiralis. The rapidity with which challenge infections are expelled suggests that either the specific inflammatory changes generated during primary infection result in an environment that is unsuitable for establishment of subsequent infections or that challenge infections provide a stimulus that can provoke an almost instantaneous response in the primed intestine. The relationship of the observed cellular changes to such mechanisms is discussed.     

The enhancement of muscle trichinosis in rabbits after immunization with heterologous serum proteins

The enhancement of muscle trichinosis in rabbits after immunization with heterologous serum proteins. International Journal for Parasitology4, 193–196. Rabbits were immunized with electrophoretically-purified rat serum albumin, β-globulin or γ-globulin in Freund's Complete Adjuvant and then inoculated with Trichinella spiralis larvae. Muscle parasitism was greatly enhanced in all the treated animals; this, plus the high levels of anti-rat and low levels of antiparasite antibody, indicates that antigenic competition can increase parasite numbers in trichinosis. Antigenic competition may play a role in the establishment of natural infections by T. spiralis by deflecting a protective immunological response by the host.     

Seroprevalence of Toxoplasma gondii and Trichinella spiralis infections in wild boars (Sus scrofa) in Korea

Toxoplasma gondii and Trichinella spiralis are important zoonotic pathogens with worldwide distributions. In Korea, several outbreaks of human toxoplasmosis and trichinellosis due to the consumption of infected wild animals have been reported. The purpose of this study was to determine the seroprevalence of T. gondii and T. spiralis infections in wild boars killed in Korea from December 2009 to October 2011. A total of 521 wild boars hunted in eight provinces were examined for antibodies to T. gondii and T. spiralis by using commercial ELISA kits. Overall, 25.1% of serum samples from individual boars were seropositive for T. gondii and 1.7% were seropositive for T. spiralis. Seropositive for T. gondii was found in the boars in all the eight provinces investigated and for T. spiralis in four provinces. This is the first report on the seroprevalence of T. gondii and T. spiralis infections in wild boars in Korea. The consumption of undercooked wild boar meat may expose humans to a high risk of infection.     

Trichinella spiralis: role of non-H-2 genes in resistance to primary infection in mice

Two strains of mice which share identical H-2 genes but differ in their genetic backgrounds were compared for their ability to resist infection with Trichinella spiralis. The two strains of mice, C3HeB/FeJ and AKR/J, share the H-2k haplotype which is associated with susceptibility to primary infection with T. spiralis in H-2 congenic strains of mice. AKR/J mice, infected with 150 infective muscle larvae, harbored significantly fewer muscle larvae 30 days postinfection than did mice of the strain C3HeB/FeJ. Approximately equal numbers of worms establish in the small intestine of AKR and C3H mice, but the AKR mice expelled adult worms from the gut more rapidly than did mice of the C3H strain. By Day 9 postinfection, 50% of the worms had been expelled by the AKR mice whereas expulsion of worms from C3H mice was delayed beyond Day 9 and occurred primarily between Days 10 and 12. Over this same experimental period (Days 6-12), fecundity of female worms from AKR mice, measured as the mean newborn larvae/female/hour, was approximately one-half that of worms taken from C3H mice. These results support the conclusion that genes outside of the mouse H-2 complex regulate expulsion of adult worms from the gut. These background genes also markedly influence the fecundity of female worms.     

Trichinella spiralis and Strongyloides ratti: immune interaction in adult rats.

The consequences of prior and concurrent infection with two species of nematodes were studied in rats. Primary infection with Strongyloides ratti adversely affected the development of a secondary Trichinella spiralis infection. Both immediate and delayed challenge with T. spiralis, following the expulsion of the previous S. ratti infection, reduced the percentage of worm recovery of the former as well as their fecundities and lengths. It is suggested that nonspecific inflammation produced by one species, during the peak period of worm expulsion, was not responsible for the accelerated rate of expulsion of the other; instead a direct, specific cross-immunity was probably operative affecting the survival of the challenge species. The response elicited by previous experience of the intestinal phase was reciprocal, but there was evidence of an enhancing effect by the muscle larval stages of T. spiralis on S. ratti. Rats concurrently infected with both species expelled S. ratti more rapidly than T. spiralis. Possible mechanisms underlying the interaction between the two species are suggested and discussed.     

Trichinella spiralis: Comparison with an Arctic isolate

The muscle phase of Trichinella spiralis and of Trichinella sp. isolated in the Arctic was compared in experimental and wild animals. Reproductive capacity indices (RCI) of the Trichinella sp. isolate were significantly lower in laboratory rodents but were similar to T. spiralis in wild rodents. Sprague-Dawley rats were the most refractory to the Trichinella sp. isolate of all laboratory rodents. Outbred strains of mice were more susceptible to both T. spiralis and the Trichinella sp. isolate than inbred strains of mice. T. spiralis muscle larvae survived longer in mice and the survival of both T. spiralis and the Trichinella sp. isolate larvae was higher in female mice. While single pair interbreeding experiments showed reproductive isolation between T. spiralis and the Trichinella sp. isolate, multiple pair and transplant breeding experiments showed reproductive compatibility. Male and female infective larvae of T. spiralis and the Trichinella sp. isolate differed morphometrically, but a convergence in size of worms was observed after prolonged passages of the parasites in mice. Passaging history of the isolate and host species was found to have a significant effect on Trichinella morphology. It is proposed that the Trichinella sp. isolate is a physiological variant of T. spiralis and not a distinct species.     

An Outbreak of Trichinosis with Molecular Identification of Trichinella sp. in Vietnam

The 5th outbreak of trichinosis occurred in a mountainous area of North Vietnam in 2012, involving 24 patients among 27 people who consumed raw pork together. Six of these patients visited several hospitals in Hanoi for treatment. Similar clinical symptoms appeared in these patients within 5-8 days after eating infected raw pork, which consisted of fever, muscle pain, difficult moving, edema, difficult swallowing, and difficult breathing. ELISA revealed all (6/6) positive reactions against Trichinella spiralis antigen and all cases showed positive biopsy results for Trichinella sp. larvae in the muscle. The larvae detected in the patients were identified as T. spiralis (Vietnamese strain) by the molecular analysis of the mitochondrial cytochrome c oxidase subunit III (cox3) gene.     

Immune responses to Trichinella pseudospiralis and Trichinella spiralis in mice

Primary infections with Trichinella pseudospiralis and Trichinella spiralis were followed in rapid- (NIH) and slow- (B10G) responder strains of mice. Expulsion of T. pseudospiralis was slower in both strains, but markedly so only in slower responder B10G mice. Blast cell activity in the mesenteric lymph nodes of the mice correlated with the expulsion patterns. In NIH mice, both parasites stimulated a strong response by day 8 of infection and activity had returned to control levels by day 11. In B10G mice, T. spiralis elicited an earlier peak response (day 12) than T. pseudospiralis (day 18), but in both, activity returned to control levels by day 21. Immunity to T. pseudospiralis and T. spiralis could be stimulated in NIH mice by prior infection with either parasite, by injection of T. spiralis larval antigen and by adoptive transfer of immune mesenteric lymph node cells taken from mice infected with either parasite. This extensive cross reactivity, and the differences seen during primary infections, are discussed in relation to the biology and specific identity of the two worms.     

Immunity to Trichinella spiralis in irradiated mice

Irradiation prevented the accelerated expulsion of Trichinella spiralis from mice immunized by transfer of immune mesenteric lymph node cells (IMLNC) or by prior infection. Nevertheless, worms in irradiated immune mice were smaller and less fecund than those in controls. In adoptively immunized and irradiated mice expulsion could not be achieved by increasing the numbers of IMLNC transferred, although the effect upon worm length was more severe. Thus IMLNC express a direct, anti-worm immunity which is independent of their role in worm expulsion. IMLNC cause expulsion in irradiated mice only when adequate levels of bone marrow-derived cells are available. The results are discussed in terms of a possible antibody-mediated basis for direct anti-worm immunity.     

Trichinella spiralis: immunity and inflammation in the expulsion of transplanted adult worms from mice.

The technique of implanting adult Trichinella spiralis into the intestines of mice has been used to assess the contributions of direct, anti-worm immunity and of intestinal inflammation to worm expulsion. The survival after transfer of worms exposed to an effective adoptive immunity in donors was no different from that of worms taken from control donors. Worms taken from donors 8 days after infection, i.e., shortly before the onset of expulsion, showed no increased susceptibility to an immunity adoptively transferred to the recipient mice. When worms were implanted into mice responding to a prior, oral infection they were expelled rapidly. This expulsion was independent of the age of the worms transferred and took place at the same time as the expulsion of the existing infection.