Pathological and molecular identification of porcine cysticercosis in Maharashtra, India

Porcine cysticercosis, caused by metacestodes of Taenia solium is an important emerging zoonotic disease with public health and economic significance. Pigs acquire the disease through consumption of Taenia solium eggs excreted by human tapeworm carriers. The present study was conducted to investigate the prevalence of porcine cysticercosis in Nagpur and Mumbai region of Maharashtra, India by P/M examination of carcasses followed by histopathology of affected organs in infected animals and molecular identification of cysts for confirmation. Out of 1000 pigs examined during slaughter, three pigs were found to be heavily affected with T. solium cysts giving a prevalence of 0.3%. Histological section of brain in infected animals revealed marked vascular congestion of meninges, mild neuronal degeneration, perivascular cuffing and gliosis while the liver showed the infiltration of mononuclear cell, predominantly eosinophils throughout the parenchyma. Some degree of calcification was observed in the cysts lodged in liver while calcification was not evident in case of cysts lodged in brain, tongue, diaphragm and skeletal muscle. Molecular identification by PCR using two sets of oligonucleotide primers against LSU rRNA gene and Mt-Cox1 gene of T. solium confirms the cysts to be that of T. solium. The molecular diagnostics methods have been considered for validation in conjunction with P/M inspections, parasitological and histopathological examinations. The study confirms the presence of porcine cysticercosis in the two regions and demands proper sanitary measures to minimize the risk of infection from zoonoses and food safety point of view.

In Vitro Study of Taenia solium Postoncospheral Form

Background

The transitional period between the oncosphere and the cysticercus of Taenia solium is the postoncospheral (PO) form, which has not yet been completely characterized. The aim of this work was to standardize a method to obtain T. solium PO forms by in vitro cultivation. We studied the morphology of the PO form and compared the expression of antigenic proteins among the PO form, oncosphere, and cysticerci stages.

Methodology/Principal Findings

T. solium activated oncospheres were co-cultured with ten cell lines to obtain PO forms, which we studied at three stages of development–days 15, 30, and 60. A high percentage (32%) of PO forms was obtained using HCT-8 cells in comparison to the other cell lines. The morphology was observed by bright field, scanning, and transmission electron microscopy. Morphology of the PO form changed over time, with the six hooks commonly seen in the oncosphere stage disappearing in the PO forms, and vesicles and microtriches observed in the tegument. The PO forms grew as they aged, reaching a diameter of 2.5 mm at 60 days of culture. 15–30 day PO forms developed into mature cysticerci when inoculated into rats. Antigenic proteins expressed in the PO forms are also expressed by the oncosphere and cysticerci stages, with more cysticerci antigenic proteins expressed as the PO forms ages.

Conclusions/Significance

This is the first report of an in vitro production method of T. solium PO forms. The changes observed in protein expression may be useful in identifying new targets for vaccine development. In vitro culture of PO form will aid in understanding the host-parasite relationship, since the structural changes of the developing PO forms may reflect the parasite’s immunoprotective mechanisms. A wider application of this method could significantly reduce the use of animals, and thus the costs and time required for further experimental investigations.

Neurocysticercosis is caused by T. solium, which is a neglected disease. The postoncospheral (PO) form is an intermediate form between the oncosphere, which is the larva, and the fully developed cysticercus, which is a cyst with a scolex. The morphology, development, and protein and antigen expression of the PO form have not previously been characterized. Here, we report the novel in vitro cultivation of T. solium PO forms and characterize the morphology, development, and expression of antigenic proteins. This new method will allow for better study of this transitional form, which is very difficult to study in the intermediate host. With the increased availability of secreted proteins and antigens, in vitro cultivation will help improve diagnostic assays and provide new targets for vaccine development to block transmission.

[Identification of Taenia solium with abnormal number of scolex hooklets]

OBJECTIVE

To identify 3 suspected adults Taenia solium with abnormal number of hooklets on scolex collected from 3 patients of Dali in Yunnan Province.

METHODS

Tapeworms were observed with unaided eyes. Morphology of the scolices and gravid proglottids was observed under microscope. DNA of gravid proglottids of the 3 adult tapeworms was extracted. T. solium mitochondrial cytochrome c oxidase subunit 1 gene (cox1) fragment and the full coxz1 gene were amplified by PCR. The cox1 gene of one isolate was sequenced. Eggs were hatched and oncospheres were inoculated into mice subcutaneously. Each mouse was subcutaneously injected with 1 mg dexamethasone once daily. Sixty days after infection, all mice were sacrificed and the morphology of cysticerci was observed. Two macaque monkeys were fed with eggs (2.5 x 10(5) per monkey). Euthanasia and autopsy were performed on day 47. Morphology of cysticerci were observed by light and scanning electron microscopy, and pathological changes of livers were observed.

RESULTS

The number of hooklets on scolices of the three tapeworms was 0, 4 and 10, respectively, and lateral uterine branches in gravid proglottids were 7-12. PCR results of co1l gene fragment with species-specific primer for T. solium were all positive. The complete sequence of cox1 gene had 99.8% identity to the reported T. solium sequences. Cysticerci were obtained from hypoderm of mouse, muscles and hearts of monkey. Four suckers and 26-28 hooklets ranged in two rows around rostellum on scolex were microscopically observed. Milia-like lesions were found in monkey liver. Histological examination showed that there was fibrous connective tissue hyperplasia and eosinophil infiltration around lesion, and parasites were found in some cysts.

CONCLUSION

The three tapeworms with abnormal number of hooklets have all been identified as T. solium. The larvae can infect macaque and lead to muscle and liver cysticercosis.

Portrait of Human Tapeworms

The tapeworms of the genus Taenia that infect human beings are T. solium, T. saginata and T. saginata asiatica. Taenia solium and T. saginata exhibit unequivocal features that characterize them; in contrast, only recent DNA studies, morphological characteristics, and epidemiological and sanitary aspects indicate that T. saginata asiatica is a subspecies of T. saginata. These 3 tapeworms occur in humans in their adult stage, and the intermediate hosts are pigs for T. solium and T. saginata asiatica and cows for T. saginata. Their identification is crucial considering the migratory increase from Asia to the Western Hemisphere and the fact that these tapeworms coexist in the same environment in Asia; furthermore, it is estimated that movement in both directions across the United States-Mexico border exceeds 200 million persons per yr, and thus, opportunities for acquiring and transporting T. solium infections are multiplied. It is not easy to distinguish among these tapeworms; therefore, a comparative diagram of the 3 parasites is shown in this article, which will facilitate their identification. All morphological features, some of which allow for identification, are clear and can be easily distinguished among the 3 tapeworms.