Molecular identification of Echinococcus granulosus genotypes (G1 and G7) isolated from pigs in Mexico.

With the aim of genotyping Echinococcus granulosus cysts found in Mexican livestock, we collected hydatid cysts from the livers and lungs of pigs in slaughterhouses in the state of Morelos, Central Region of Mexico. DNA was extracted from the parasites and examined by polymerase chain reaction (PCR) of rDNA internal transcribed spacer 1 (ITS1-PCR), Eg9-PCR, Eg16-PCR, and PCR-restriction fragment length polymorphism (PCR-RFLP). In addition, fragments of the genes coding for mitochondrial cytochrome c oxidase subunit 1 (CO1) and NADH dehydrogenase 1 (ND1) were sequenced. Two different genotypes of E. granulosus were unequivocally identified, the common sheep genotype, G1, and the common pig genotype, G7. The G1 genotype of E. granulosus has not been previously demonstrated in Mexico. Because of its recognized infectivity in humans, G1 genotype is a direct threat to human health and its presence in Mexico is consequently of immediate public health importance and epidemiological relevance.

Impact of naturally acquired Taenia solium cysticercosis on the hormonal levels of free ranging boars.

In chronically infected BALBc/AnN male mice, Taenia crassiceps cysticercosis induces changes in the host's sex steroids hormone that lead to their estrogenization and deandrogenization, with possible repercussions on their susceptibility to infections. Here reported are the serum steroid levels in free range cysticercotic male boars. Therefore, the possible effects of Taenia solium cysticerci over the pig steroid levels were evaluated. Herein are described the sex steroids and cortisol levels of non-cysticercotic (n=25) and cysticercotic (n=22) adult boars, as diagnosed by tongue inspection, all free-ranging in a typical village of an endemic rural area in Mexico. A significant reduction of testosterone (P=0.022) and a likely one of 17beta-estradiol (P=0.08) levels were found in the cysticercotic boars in comparison with those non-cysticercotic, whilst no significant differences in the cortisol and DHEA levels were detected. Serum levels of specific antibodies did not correlate with infection nor with the levels of any of the hormones measured. Results suggest that T. solium cysticercosis significantly affects the hormonal status of its porcine host independently of their antibody response.

Different effects of chorionic gonadotropin on Taenia crassiceps and Taenia solium cysticerci cultured in vitro.

Hormones play a significant role in murine Taenia crassiceps cysticercosis, and they may also participate in the susceptibility to Taenia solium cysticercosis. In the present study, in vitro effects are reported for human chorionic gonadotropin (hCG) on the larval stages of T. crassiceps (WFU strain) and T. solium. hCG effectively promotes parasite reproduction, i.e., it increases the number of buds on T. crassiceps cysticerci and the percentage of evagination and parasite length in T. solium. This is the first report in which a direct effect of hCG is reported for a parasite. hCG or mouse luteinizing hormone could be recognized by the cysticerci as mitogenic factors and contribute to the female and pregnancy bias toward susceptibility to T. crassiceps and T. solium cysticercosis, respectively.

Failure to incriminate domestic flies (Diptera: Muscidae) as mechanical vectors of Taenia eggs (Cyclophyllidea: Taeniidae) in rural Mexico.

Flies caught in homes in a rural village in Guerrero, Mexico, between November 1994 and August 1995 were assessed for their role in the transmission of Taenia solium L. Most (99%) of the trapped flies were Musca domestica L. None of the 1,187 guts or 1,080 legs of the flies contained T. solium eggs. Pigs roam freely in this village consuming human fecal material immediately after defecation, thereby limiting fly contact with T. solium eggs.

Taenia solium cysticercosis in young pigs: age at first infection and histological characteristics.

In spite of the vast knowledge that exists in the fields of immunology, biochemistry, diagnosis and treatment, the basic facts about the dynamics of the transmission of Taenia solium are incomplete. The present study determines the age at which piglets become infected in a rural community of Mexico, where the climate is divided into the dry and rainy seasons. It was found that piglets become infected during the dry months, not so during the rainy season. They pick up eggs at the age of 2 to 4 weeks and the metacestodes are present in the liver. In older animals aged 4 to 6 months, the larvae were also found in the muscles. In a 6-month-old pig larvae were found in the muscles and brain. These findings may be explained by behavioural studies of free living pigs and climatic conditions.

Experimental Taenia solium cysticercosis in pigs: characteristics of the infection and antibody response.

Pigs were infected with taeniid eggs to study the susceptibility to infection and reinfection of the animals of mixed breeds and of different ages, the viability and death of the metacestodes in the host tissue, and the antibody response which accompanies these events. Sixteen pigs were infected with Taenia solium eggs for this purpose. At necropsy metacestodes were counted in 2 kg of shoulder muscles and classified as vesicular or caseous, and all the metacestodes in brains were counted and classified. The results show that pigs inoculated at 49 and 60 days of age became infected to different degrees and reacted differently to the presence of parasites. In the brain the metacestodes remain viable for longer periods than in muscles. Enzyme-linked immunosorbent assay (ELISA) showed a significant rise in antibodies after infection, which started to decrease 92 days post-infection (p.i.). Pigs with viable cysts remained seropositive up to the end of the experiment (281 days p.i.). Antibody levels rose further after reinfection or after treatment. The results of Western blot were comparable to those of ELISA. Antigens of 13, 14 and 18 kDa were most frequently recognized in early infections and then started to decrease 92 days p.i., while the antigens of 42, 50 and 24 kDa were recognized during later stages of infection (200 days p.i.). The results suggest that older animals are more resistant to the infection [corrected].

Taenia solium cysticercosis: immunity in pigs induced by primary infection.

The present study demonstrates that pigs experimentally infected with Taenia solium eggs develop resistance to reinfection that lasts at least five months. Thirteen 2-month-old piglets were infected with eggs of Taenia solium. After 5 months, two pigs were euthanized and five were challenged with eggs from a second tapeworm. Nine months after the first infection, six pigs were challenged with a third tapeworm. All 11 challenged pigs were euthanized 2 months after reinfection. In order to confirm the infectivity of the eggs, several piglets were inoculated with each taenia. Two of the five pigs reinfected after 5 months did not develop metacestodes, two showed few caseous non-infective forms and in the fifth pig, 14% of the metacestodes were vesicular and 86% colloidal and caseous. In the six animals challenged 9 months after the first infection, three were heavily infected with vesicular metacestodes and the other three showed only colloid and caseous forms in muscles. All parasites found in brains were vesicular. We conclude that immunity due to primary infection lasts at least 5 months. At 2 months of infection antigens of 24 and 39-42 kDa were the most frequently recognised. In those pigs with only a few caseous cysts in muscles and/or vesicular ones in brains no antibodies were detected.

Diagnosis of porcine cysticercosis: a comparative study of serological tests for detection of circulating antibody and viable parasites.

Epidemiological studies of porcine cysticercosis require identification of pigs harbouring viable Taenia solium cysticerci and estimates of the degree of exposure to the parasite in the pig population destined for human consumption. Identification of infected pigs with viable larvae is achieved through detection of their secretory products. However, detectable levels of circulating antibody may also be present in the absence of viable larvae. In this study, both types of tests have been evaluated in groups of pigs experimentally infected with T. solium. Detection of viable cysticerci was achieved using a monoclonal antibody-based (HP10) antigen capture assay. HP10 epitope-bearing antigens have now been demonstrated in T. solium and T. crassiceps cyst fluid and excretion/secretions. Serum antibodies were measured in ELISA assays using two parasite preparations as antigens; T. solium cyst fluid and T. crassiceps cyst fluid antigens bearing the HP10 epitope. Low-background values were obtained with sera from non-infected animals in all the assays used. In heavily infected pigs, both antigens and antibodies were detected at least 29 days and up to 200 days post-infection (pi), while in lightly infected pigs antigen and antibodies were first observed between 61-97 days pi. Thus, the levels of the serum antigen and antibody varied with the intensity of the infection.

Limitations of current diagnostic procedures for the diagnosis of Taenia solium cysticercosis in rural pigs.

The aim of the present study was to evaluate diagnostic procedures for porcine cysticercosis. Sera were obtained from 32 pigs reared in commercial farms, 47 pigs before and after experimental infection, 42 carefully necropsied rural pigs and 191 slaughtered pigs from rural communities in which the presence of the Taenia solium metacestode was assessed by tongue dissection. Sera were analyzed by ELISA to detect antibodies against T. solium antigens and to detect parasite antigens. Most sera from the necropsied rural pigs were also evaluated by the Western blot method. Antigen and antibody ELISA detection assays showed high sensitivity and specificity when applied to sera from pigs reared in commercial farms. In contrast, all methods (Ag-ELISA, Ab-ELISA assays, EITB and tongue inspection) showed lower sensitivity and specificity when applied to the generally lightly infected rurally reared pigs. The probability distribution of cysts in carcasses were also determined. These results emphasize the difficulties in detecting cysticercosis in rural pigs with low levels of cyst burdens.

Vaccination against Taenia solium cysticercosis in underfed rustic pigs of México: roles of age, genetic background and antibody response.

Vaccination of pigs of mixed genetic make-up, raised as rustically as done in rural Mexico, resulted in effective protection to experimental challenge against Taenia solium cysticercosis. Maximum protection was achieved if pigs were immunized at 70 days of age. There was large variation of viable parasite load within vaccinated pigs and controls, which is suggestive of significant genetic factors influencing susceptibility, besides immunization. Our results strengthen the advisability of pig vaccination for control of T. solium cysticercosis, since it lowers the number of viable cysticerci capable of transforming into tapeworms.

Histological description of tomographic images of Taenia solium cysticerci in pig brains.

In the computed tomography (CT) scans of five pigs with neurocysticercosis (Taenia solium), interesting lesions produced by the larvae were selected. The pigs were euthanized and the corresponding lesions in their brains identified and processed for histopathology. It was found that the hypodense areas in CT scans corresponded to vesicular larvae that are presumably viable. The hyperdense areas were either solid in nature or had formed a rim around a hypodense center and in the brain slice they were either solid granulomas or colloidal cysts with inflammatory reaction in the periphery, perivascular cuffing, and vasculitis. It was not always possible to classify larvae as meningeal or parenchymatous in the CT.

Limits of the therapeutic properties of synthetic S3Pvac anti-cysticercosis vaccine.

The S3Pvac synthetic vaccine, composed of three peptides (GK1, KETc1 and KETc12) effectively protects against cysticercosis under experimental and field conditions. Additionally, S3Pvac vaccine can effectively damage early-established cysticerci in experimentally lightly infected young pigs. This study was designed to explore if also fully-developed cysticerci that eluded immunity induced by the infection can be damaged by S3Pvac-induced immunity in naturally, heavily infected adult pigs. Fourteen pigs identified as cysticercotic by tongue inspection from rural communities were purchased and moved to controlled conditions in the Faculty of Veterinary Medicine. Half of these pigs were treated once a month three times with S3Pvac plus saponin, and the other half received only saponin (controls). Twelve months later pigs were euthanized, and the number of cysticerci, their macro and microscopic status and their capacity to transform into tapeworms were determined. S3Pvac failed to damage fully-developed muscle cysticerci of naturally, heavily infected adult pigs. To explore possible factors involved in the failure of the therapeutic capacity pooled sera from control and treated cysticercotic pigs were added to mice mononuclear peripheral cells. Pooled sera from non-infected pigs were also tested. Sera from control and treated infected pigs almost completely suppressed the T cell proliferative responses, pointing to the presence of suppressor factors. In conclusion, S3Pvac vaccine failed to damage fully-developed cysticerci in pigs in which a host parasite relationship had evolved after months of infection with immunological implications.