Concordance between two monoclonal antibody-based antigen detection enzyme-linked immunosorbent assays for measuring cysticercal antigen levels in sera from pigs experimentally infected with Taenia solium and Taenia hydatigena.

BACKGROUND: Antigen detection in Taenia solium cysticercosis confirms viable infection in the intermediate host (either pig or human). The reference B158/B60 monoclonal antibody (mAb)-based Ag-enzyme-linked immunosorbent assay (ELISA) has acceptable levels of sensitivity and specificity in human neurocysticercosis with multiple brain cysts, although its sensitivity is lower in cases with single brain cysts, whereas in porcine cysticercosis the assay specificity is affected by its frequent cross-reaction with Taenia hydatigena, another common cestode found in pigs. Our group has produced 21 anti-T. solium mAbs reacting against antigens of the whole cyst, vesicular fluid, and secretory/excretory products, identifying TsW8/TsW5 as the most promising pair of mAbs for an Ag-ELISA. METHODS: We report the use of the TsW8/TsW5 Ag-ELISA to measure cysticercus antigen levels [expressed as optical density (OD) values] in two panels of sera collected from day 0 (baseline) to day 90 postinfection (PI) from pigs experimentally infected with T. solium (n = 26) and T. hydatigena (n = 12). At baseline and on days 28 and 90 PI, we used Bland-Altman (BA) analysis and Lin's concordance correlation coefficients (CCC) to determine the concordance between the TsW8/TsW5 and the B158/B60 Ag-ELISA. RESULTS: The TsW8/TsW5 Ag-ELISA was able to efficiently measure circulating antigen levels in T. solium-infected pigs, similar to that obtained with the B158/B60 Ag-ELISA. Almost all paired log-OD differences between assays were within the limits of agreement (LoA) in the BA analysis at baseline and on days 28 and 90 PI (92.3%, 100%, and 100%, respectively), and a high concordance of log-ODs between assays was also found (Lin's CCC: 0.69, 0.92, and 0.96, respectively, all P < 0.001). In pigs infected with T. hydatigena, almost all paired log-OD differences were within the LoA in the BA analysis, whereas the concordance of log-ODs between assays was low at baseline (Lin's CCC: 0.24) but increased on days 28 and 90 PI (Lins' CCC: 0.88 and 0.98, P < 0.001). CONCLUSIONS/SIGNIFICANCE: The TsW8/TsW5 Ag-ELISA recognizes antigens in pigs with T. solium cysticercosis and is highly concordant with the B158/B60 Ag-ELISA. However, its diagnostic use is hampered by cross-reactions with T. hydatigena, as in other mAb-based Ag-ELISAs.

Antibody Banding Patterns on the Enzyme-Linked Immunoelectrotransfer Blot (EITB) Assay Clearly Discriminate Viable Cysticercosis in Naturally Infected Pigs.

Enzyme-linked immunoelectrotransfer blot (EITB) detects antibodies against seven Taenia solium larvae antigens in three protein families (GP50, T24/42, and 8-kDa) with different structures and functions. EITB banding patterns against these antigens in pigs provide information about the course of infection and may discriminate viable cysticercosis. We analyzed the banding patterns and infection outcomes (presence of viable cysts, degenerated cysts, and any cysts) of 512 rural pigs. Banding patterns were grouped into homogenous classes using latent class analysis, and relationships with infection outcomes were assessed. Four classes were identified: 1 (n = 308, EITB-negative or positive for the GP50 family), 2 (n = 127, positive for GP50 (GP50 family), GP42-39 and GP24 (T24/42 family), but negative for 8-kDa antigens), 3 (n = 22, positive for GP50 and T24/42 antigens (GP42-39 and GP24), as well as to 8-kDa bands GP13, GP14, and GP18, but negative for GP21), and 4 (n = 55, positive for GP50 and T24/42 antigens, as well as to 8-kDa antigens GP21 and GP18 in combination). Pigs in classes 3 and 4 were more likely to have viable cysts (72.6% and 96.4%, respectively) than pigs in classes 1 and 2 (0.7% and 27.6%, respectively; p < 0.001). The number of infections with any cysts was higher in classes 3 and 4 (77.3% and 98.2%, respectively) and lower in classes 2 and 1 (34.7% and 4.9%, respectively; p < 0.001). Pigs with viable cysts represented >90% of pigs with any cysts in classes 3 and 4 (94.1% and 98.2%, respectively), while degenerated cysts were frequent among pigs with any cysts in classes 1, 3, and 2 (86.7%, 47.1%, and 43.2%, respectively; p < 0.001). EITB banding patterns strongly correlate with cysticercosis infection status in rural pigs, with classes 3 and 4 being more predictive of viable infections.

Oxfendazole as successful treatment of Taenia hydatigena metacestodes in naturally infected pigs

The efficacy of oxfendazole (OFZ) on Taenia hydatigena metacestodes, also called Cysticercus tenuicollis (C. tenuicollis), was studied in 648 raising pigs. This study was performed in Tumbes Department in Peru, an endemic area for cysticercosis. Pigs were randomized in two groups;untreated group (n=142) did not receive any treatment and treated group (n=506) received OFZ treatment at a single dose of 30 mg/kg body weight. Six months after treatment, the pigs were necropsied. The prevalence of infection by C. tenuicollis among the pigs was 27.5%(39/142) and 2.0%(10/506) in untreated and treated groups, respectively. Untreated group was infested only with viable cysts, whereas treated group had no viable cysts. All the cysts found in treated group presented degeneration, with a thick membrane, and they contained milky fluid and fibrous tissue. A single dose of OFZ was effective against C. tenuicollis, thus providing an alternative drug for controlling this parasite in pigs.

Relationship between serum antibodies and Taenia solium larvae burden in pigs raised in field conditions.

BACKGROUND: Serological tests have been used for the diagnosis of Taenia solium infection in pigs. However, those serological results do not necessarily correlate with the actual infection burden after performing pig necropsy. This study aimed to evaluate the Electro Immuno Transfer Blot (EITB) seropositivity with infection burden in naturally infected pigs. METHODOLOGY/PRINCIPAL FINDINGS: In an endemic area of Peru, 476 pigs were sampled. Seroprevalence was 60.5 ± 4.5% with a statistically higher proportion of positive older pigs (>8 months) than young pigs. The logistic model showed that pigs >8 month of age were 2.5 times more likely to be EITB-positive than ≤ 8 months. A subset of 84 seropositive pigs were necropsied, with 45.2% (38/84) positive to 1-2 bands, 46.4% (39/84) to 3 bands, and 8.3% (7/84) to 4+ bands. 41 out of 84 positive pigs were negative to necropsy (48.8%) and 43 (51%) had one or more cysts (positive predictive value). Older pigs showed more moderate and heavy infection burdens compared to younger pigs. In general, regardless of the age of the pig, the probability of having more cysts (parasite burden) increases proportionally with the number of EITB bands. CONCLUSIONS/SIGNIFICANCE: The probability of being necropsy-positive increased with the number of bands, and age. Therefore, the EITB is a measure of exposure rather than a test to determine the real prevalence of cysticercosis infection.

Transmission dynamics of Taenia solium and potential for pig-to-pig transmission.

Taenia solium taeniasis/cysticercosis is one of few potentially eradicable infectious diseases and is the target of control programs in several countries. The larval stage of this zoonotic cestode invades the human brain and is responsible for most cases of adult-onset epilepsy in the world. Our current understanding of the life cycle implicates humans as the only definitive host and tapeworm carrier, and thus the sole source of infective eggs that are responsible for cysticercosis in both human and pigs through oral-faecal transmission. Here we review transmission dynamics of porcine cysticercosis including an alternative pig-to-pig route of transmission, previously not suspected to exist. Second-hand transmission of T. solium eggs could explain the overdispersed pattern of porcine cysticercosis, with few pigs harbouring heavy parasite burdens and many more harbouring small numbers of parasites.

Short report: secondary transmission in porcine cysticercosis: description and their potential implications for control sustainability.

Taenia solium taeniasis/cysticercosis is one of few potentially eradicable infectious diseases and is the target of control programs in several countries. The larval stage of this zoonotic cestode invades the human brain and is responsible for most cases of adult-onset epilepsy in the world. The pig is the natural intermediate host, harboring the larvae or cysticerci. Our current understanding of the life cycle implicates humans as the only definitive host and tapeworm carrier (developing taeniasis) and thus the sole source of infective eggs that are responsible for cysticercosis in both human and pigs through oral-fecal transmission. Here we show evidence of an alternative pig-to-pig route of transmission, previously not suspected to exist. In a series of four experiments, naive sentinel pigs were exposed to pigs that had been infected orally with tapeworm segments (containing infective eggs) and moved to a clean environment. Consistently in all four experiments, at least one of the sentinel pigs became seropositive or infected with parasite cysts with much lower cyst burdens than did primarily infected animals. Second-hand transmission of Taenia solium eggs could explain the overdispersed pattern of porcine cysticercosis, with few pigs harboring heavy parasite burdens and many more harboring small numbers of parasites. This route of transmission opens new avenues for consideration with respect to control strategies.