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. Our results reveal the presence of receptors for hCG in different developmental phases of both cultured parasites. On day 30, both taeniid species had the highest percentage of receptors in the neck, strobila, and suckers, but these receptors decreased by day 60, delimiting the segments and the exterior of the developing proglottids in T. solium. At the same time, there was a large number of hCG receptors in the area of the presumptive cirrus organ and in calcareous corpuscles within the parenchyma. This is the first report detecting receptors for hCG on different larval stages of T. crassiceps and T. solium. A direct effect of hCG could be recognized by the cysticerci as a factor contributing to the growth and development of T. crassiceps and T. solium cysticerci, respectively.

OBJECTIVE To describe and compare the clinical impacts of neurocysticercosis (NC) caused by Taenia solium in humans and pigs.METHODS Comparative study of the brains of 16 asymptomatic pigs and 35 human NC cases (15 asymptomatic and 20 symptomatic).RESULTS In humans, cysticerci were more frequently located in the ventricles and subarachnoid space at the base of the brain (11.8%vs. 1.6%; P = 0.001 and 25.9%vs. 0%; P < 0.0001, respectively) while in pigs, cysticerci were more frequently found in the parenchyma (44.4%vs. 7.6%; P < 0.0001). In human brains, 75.9% of the cysticerci were calcified, while in pigs all cysticerci were in the vesicular stage.CONCLUSION The duration of infection and the host-parasite relationship (such as immune reactivity and brain haemodynamics) differ between humans and pigs. This may account for the different distribution and stage of the cysticerci among humans and pigs.

Taenia solium is responsible for porcine cysticercosis, and human taeniasis. The parasite constitutes a serious public health problem in endemic areas of Latin America, Asia and Africa. The eggs can infect humans, resulting in cysticercosis or neurocysticercosis. Neurocysticercosis is a serious disease resulting in high morbidity and, in some cases, death. Random amplified polymorphic DNA markers (RAPDs) was employed to assess genetic variation within 13 T. solium muscle cysticerci collected from 14 naturally infected pigs. Using six different random primers and a total of 181 cysticerci, 88 different loci were amplified, among which 77 (85%) were polymorphic between pigs and from 0 to 24% within pigs indicating the polymorphism of the population. The phenogram grouped the cysticerci population into 8 major clusters with low differences in the genetic distances among and within pigs’ parasites (ranged from 0.78 to 1.00) mainly grouping according to the pigs’ origins. Genetic similarities amongst the cysticerci from different pigs were estimated using the Jaccard algorithm. A cluster analyses were performed using UPGMA and neighbor joining methods. Principal components analysis was also employed. The high cophenetic correlation coefficient obtained for the Jaccard algorithm and the UPGMA clustering method corroborated small variability observed of isolates from Central Mexico. Both, the association (0.0 to 0.089) and the genetic diversity indexes (0.009 to 0.073), support the idea that DNA diversity is mainly due to a recombination process. Diversity, possibly due to different infection within pigs was also found albeit exceptionally.

The disease caused by Taenia solium is progressively being recognized as a growing global threat for public human health and pig husbandry that requires the development of effective control measures. A central participant in the taeniasis/cysticercosis transmission network is the human carrier of the adult tapeworm because of its great potential in spreading the infection. Herein, evidence is presented that a primary infection of golden hamsters with orally administered T. solium cysticerci improved the host's resistance against a secondary infection. Likewise, previous vaccination increased the hamster's resistance. Similar high levels of protection (>78%) were induced by systemic or oral vaccination with the S3Pvac anticysticercosis synthetic peptide vaccine or the highly immunogenic recombinant chimera based on the protective peptide KETc1 bound to Brucella spp. lumazine synthase (BLS-KETc1). Increased resistance after primo-infection and vaccination possibly results from changes in the immune conditions prevailing in the host's intestine. The contribution to protection from the KETc1 and BLS epitopes in a chimeric vaccine is under study. Preventive vaccination of definitive hosts of T. solium against the tapeworm, the most relevant step in the taeniasis/cysticercosis transmission, may greatly impact the dynamics of endemic disease and has not been studied or tried previously.

Cysticercosis caused by Taenia solium frequently affects human health and rustic porciculture. Cysticerci may localize in the central nervous system of humans causing neurocysticercosis, a major health problem in undeveloped countries. Prevalence and intensity of this disease in pigs and humans are related to social factors (poor personal hygiene, low sanitary conditions, rustic rearing of pigs, open fecalism) and possibly to biological factors such as immunity, genetic background, and gender. The indispensable role of pigs as an obligatory intermediate host in the life cycle offers the possibility of interfering with transmission through vaccination of pigs. An effective vaccine based on three synthetic peptides against pig cysticercosis has been successfully developed and proved effective in experimental and field conditions. The well-defined peptides that constitute the cysticercosis vaccine offer the possibility to explore alternative forms of antigen production and delivery systems that may improve the cost/benefit of this and other vaccines. Encouraging results were obtained in attempts to produce large amounts of these peptides and increased its immunogenicity by expression in recombinant filamentous phage (M13), in transgenic plants (carrots and papaya), and associated to bacterial immunogenic carrier proteins.

Cuentepec is a rural village of central Mexico, where 1300 pigs were bred at the time of the study in conditions that favor Taenia solium transmission. The tongues of 1087 (84%) of these pigs were visually examined and 33% were found to be cysticercotic. Castration of male pigs increased prevalence from 23 to 50% (P < 0.001) and pregnancy in sows also increased their prevalence from 28 to 59% (P < 0.001). Thus, endocrinological conditions characterized by low levels of androgens or high levels of female hormones probably influence the susceptibility of pigs to T. solium cysticercosis as observed in mice infected with Taenia crassiceps. Delaying castration of male pigs and confinement of sows during pregnancy might significantly decrease the prevalence of pig-cysticercosis and help curb transmission without much cost or difficulty.

Untreated Taenia solium cysticerci obtained from different naturally infected pigs vary notably in their capacity to develop into intestinal tapeworms in prednisolone-treated hamsters, whereas cells derived from Taenia crassiceps cysticerci after 2 mo of infection almost always develop to cysticerci in the peritoneal cavity of susceptible BALB/cAnN mice. Preincubation of whole cysticerci or parasite cells with mice immunoglobulins raised against an 18-mer peptide epitope (GK-1) common to both parasites significantly interferes with both transformations. These crippling effects of antiparasite antibodies suggest new forms of immunological interference with parasite biology other than simple killing. Antibodies that cripple biological functions of the parasite, e.g., their development to reproductive or pathogenic stages, make them important protagonists in taeniasis/cysticercosis disease as classic parasitocidal antibodies. Different serum levels of crippling antibodies in the infected pigs could be responsible for the varied ability of cysticerci to convert to tapeworms. Antigens capable of inducing crippling antibodies, e.g., GK-1, could be useful as a therapeutic vaccine for pigs in order to reduce parasite transmission.

This article reviews current knowledge on human and porcine cysticercosis caused by Taenia solium. It highlights the conditions favorable for its prevalence and transmission, as well as current trends in research on its natural history, epidemiology, immunopathology, diagnosis, treatment and prevention. Our opinions on the most urgent needs for further research are also presented.

Research was conducted on typical smallholder farms with dual-purpose cattle (DPC) (Bos indicus×B. taurus) in the coastal north-central area of Veracruz, Mexico. The study was divided into two phases. The aim of the first phase was to investigate the effect of blood metabolites, body condition and pasture management on milk yield and postpartum intervals, in order to investigate if the former are suitable indicators of the reproductive and nutritional status of DPC. One hundred and sixty-five calvings of crossbred cows were recorded from January 1992 to November 1994 on 12 small farms. Milk samples were collected twice a week for progesterone analysis. Blood samples and BCS were taken once a month. However, in Phase II emphasis was placed on the effect of pasture management upon reproductive and productive performance of DPC. Records of four farms were obtained from June 1995 to November 1996. Stocking rates were 0.40, 0.87, 0.35 and 1.5 cows/ha for farms A, B, C and D, respectively. Farms A and C used a slow rotation while B and D used a rapid rotation. In Phase I, the changes in BCS during the last month of pregnancy and first month postpartum did not correlate (p>0.05) with milk yield or reproductive performance. Blood the metabolite profiles were not consistently related to productive or reproductive variables. The effect of farm and season was significant (p<0.05) on most of the response variables and low productivity on overstocked farms lead to the conclusion that the low reproductive performance of DPC was linked to poor pasture management. During Phase II, farms A (FA) and D (FD) produce more milk than the others. Days to first service, days open, and calving interval were similar for farms B (FB) and C (FC), highest for Farm A, and lowest for Farm D. The forage availability mean was above the critical range of 6–8 kg of dry matter per 100 kg of liveweight (kg DM/100 kg LW) in all farms (range from 6.1±5.0 to 21.1±11.2 kg DM/100 kg LW). Farm D had the highest stocking rate (1.5 cows/ha), a rapid rotation (10 paddocks), a good forage availability (7.1±3.9 kg DM/100 kg LW) with a good quality for a tropical pasture (11.6±2.4% crude protein), and an economic energy supplementation. These results suggest this type of management could be more widely employed to improve the productivity of DPC on smallholder farms in the Mexican tropics.

A partial immunocharacterization of oncosphere and metacestode antigens of Taenia solium was carried out and compared to antigens from other taeniid species. The results indicated that T. solium metacestode antigen contained epitopes cross reactive with rabbit anti-sera to adult and oncospheral stages of the parasite. Oncospheres, however, consisted largely of stage specific antigens. Western blot analysis indicated that T. solium and T. pisiformis shared several oncospheral antigens; however, this was not the case with T. solium and T. hydatigena. Western blot analysis showed a time-related increase in the number of molecules recognized by antibodies to T. solium oncosphere and metacestode antigens in pigs experimentally infected with T. solium eggs. Oncosphere specific antibodies were detected in pig sera one month after experimental infection whereas antibodies to cystic stage antigens were not present until the 3rd to 5th month post infection. Sera from neurocysticercotic patients as well as naturally infected cysticercotic pigs recognized high molecular weight antigens in the oncospheres.

We describe the cloning and the evaluation of the protective capacity of 5 recombinant antigens expressed during the cysticercus stage of both Taenia crassiceps and Taenia solium. A cDNA library was constructed in bacteriophage lambda ZAP using mRNA isolated from larvae of T. crassiceps of the ORF strain. The recombinant phage library was screened with polyclonal antibodies against 56- and 74-kDa protective antigen fractions. This screening identified 13 recombinant clones, 5 of which were also strongly recognized by pooled sera from pigs experimentally infected with T. solium. The native antigens are proteins of 56 (clones KETcl, 4, 7) and 74 and 78 kDa (clones KETc11, 12) of T. crassiceps cysticerci. Vaccination experiments using these 5 recombinant clones against murine cysticercosis point to the relevance of KETcl, 4, 7, and 12 in host protection, whereas immunization with the clone KETc11 does not modify the parasite load in females and facilitates the parasitosis in males. We report here the DNA and the deduced amino acid sequence (100 amino acids) of the first protective antigen (KETc7) of potential interest for T. solium pig cysticercosis prevention.

Fifty-six (56) pigs were immunized against Taenia solium cysticercosis with antigens from Taenia crassiceps metacestodes, in a variety of protocols, and then challenged orally with Taenia solium proglottids or eggs. Results of immunization (expressed as individual parasite loads) ranged from significant reduction of parasite loads (host protection) to clear increase (parasite facilitation) in apparent relation to the immunogen dose, adjuvant employed and genetic background of the pigs. In all trials, however, immunized pigs harboured more damaged cysticerci than controls, indicating that immunization does induce some restrictions to parasite survival even if these are eventually overwhelmed by other parasite-promoting factors. Western blots in immunized-protected pigs indicated antigens of 242, 234, 118, 77, 55 and 45 kDa as possibly being involved in immunological protection.

An original technique for computed tomography (CT) of the pig's brain is described. Brains of 11 cysticercotic pigs were studied by CT and by macroscopic and microscopic examination after necropsy, in order to compare the tomographic images with the anatomic findings. By CT, cysticerci could be seen in all the brains except one which had only one parasite. Good correlation was found when the CT sections were compared with the anatomic slices, nevertheless not all cysticerci seen during necropsy examination could be identified in the CT images. Only two parasites were found in the ventricles. There were difficulties in differentiating submeningeal and parenchymal localization of the cysticerci. Most cysticerci had similar morphologic appearance; inflammatory reactions of different degrees and characteristics were observed around some of them.