Combined human and porcine mass chemotherapy for the control of T. solium.

A combined (human and porcine) mass chemotherapy program was tested in a controlled design in 12 village hamlets in the Peruvian highlands. A single dose of 5 mg of praziquantel was given to eliminate intestinal taeniasis in humans, and two rounds of oxfendazole (30 mg/kg) were administered to all pigs. The total population in the study villages was 5,658 resident individuals, and the porcine population at the beginning of the study was 716 pigs. Human treatment coverage was 75%, ranging from 69% to 80%. There were only a few refusals of owners for porcine treatment of their animals. The effect of the intervention was measured by comparing incidence rates (seroconversion in pigs who were seronegative 4 months before) in treatment versus control villages, before and up to 18 months after treatment. There was a clear effect in decreasing prevalence (odds ratio, 0.51; P < 0.001) and incidence (odds ratio, 0.39; P < 0.013) in the treatment area after the intervention, which did not leave to extinction of the parasite but stabilized in slightly decreased rates persisting along the follow-up period. Mass chemotherapy was effective in decreasing infection pressure in this hyperendemic area. However, the magnitude of the effect was small and did not attain the goal of eliminating transmission.

Seroincidence of porcine T. solium infection in the Peruvian highlands.

We performed repeated serological sampling of pigs in an endemic area of the Peruvian highlands (eight villages) to assess the feasibility of detecting incident cases of Taenia solium infection as indicators of ongoing transmission of the parasite. A total of 2245 samples corresponding to 1548 pigs were collected in three sampling rounds (n=716, 926, and 603, respectively). Village-period specific seroprevalences of antibodies by enzyme-linked immunoelectrotransfer blot (EITB) assay varied from 39% (95% CI: 34, 44) to 76% (95% CI: 72, 79). The prevalence of cysticercosis increased with the age of the pigs (similarly for both sexes). Around 40% of pigs were re-sampled at the end of each 4-month period. Crude incidence risks were 48% (57/120, 95% CI: 43-52) and 58% (111/192, 95% CI: 54-61) for each period. A proportion of seropositive animals became seronegative at the end of each period (23 and 15%). Incidence varied by the village, and the exposure period, and was higher in males than females (but did not differ by age).

Protection of pigs with cysticercosis from further infections after treatment with oxfendazole.

Cysticercosis, the infection by the larvae of Taenia solium, is a major cause of acquired epilepsy in the world; it also causes significant economic loss because of contaminated pork. This disease is endemic in most developing countries and no control strategy has yet been proven efficient and sustainable. To further evaluate the full potential of single-dose oxfendazole treatment for pigs as a control measure, 20 pigs with cysticercosis were treated with oxfendazole and later matched with 41 naive pigs and exposed to a natural challenge in a hyperendemic area. New infections were found by serologic testing in 15 of the 32 controls (47%), and by the presence of cysts at necropsy in 12 of them (37%). Only minute residual scars were detected in the carcasses of oxfendazole-treated pigs. Pigs with cysticercosis, once treated with oxfendazole, are protected from new infections for at least three months.

Experimental infection model for Taenia solium cysticercosis in swine. Cysticercosis Working Group in Peru.

A novel method for infecting pigs with Taenia solium using an intramuscular innoculum of oncospheres was investigated in a series of five experiments in 18 animals. The model is simple to perform, requires a minimal number of oncospheres, permits multiple infections per animal, and decreases the variation inherent in oral infection models. This intramuscular oncosphere assay (IMOA) may provide a valuable tool to evaluate therapeutic agents or potential vaccines for cysticercosis.

Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals.

Attempts were made to develop an animal model for Cyclospora cayetanensis to identify a practical laboratory host for studying human cyclosporiasis. Oocysts collected from stool of infected humans in the United States, Haiti, Guatemala, Peru, and Nepal were held in potassium dichromate solution to allow development of sporozoites. The following animal types were inoculated: 9 strains of mice, including adult and neonatal immunocompetent and immune-deficient inbred and outbred strains, rats, sandrats, chickens, ducks, rabbits, jirds, hamsters, ferrets, pigs, dogs, owl monkeys, rhesus monkeys, and cynomolgus monkeys. Most animals were inoculated by gavage, although some of the primates were fed oocysts on food items. The animals were examined for signs of infection, particularly diarrhea, and stool samples were examined for 4-6 wk after inoculation. None of the animals developed patent infections or signs of infection. We conclude that none of the animals tested is susceptible to infection with C. cayetanensis.

Persistence of passively transferred antibodies in porcine Taenia solium cysticercosis. Cysticercosis Working Group in Peru.

We evaluated the presence and persistence of anticysticercal antibodies in piglets born to Taenia solium infected sows. Infected sows from a disease-endemic area of Peru were transported to a nondisease-endemic area and impregnated. Serum samples were collected from sows and piglets on Day 2 through Week 35 after birth. Using an immunoblot specific for cysticercosis, Ig isotypes to 7 cyst antigens were measured and quantified. Serum samples from the piglets contained detectable antibodies from Week 1 through Week 35 (27 weeks after weaning). The primary Ig isotype present in both sows and piglets was IgG. Antibodies did not appear in piglet serum samples until after suckling, demonstrating that anti-cysticercal antibodies are transferred solely via colostrum. Our data have shown that maternally transferred antibodies to cyst antigens may persist through much of a pig's life. Therefore, the presence of passively transferred antibodies must be considered in studies that examine the prevalence of cysticercosis in pigs. Furthermore, when designing control strategies for cysticercosis, careful evaluation and selection of sentinel pigs becomes a crucial component of sentinel selection.

Time-response curve of oxfendazole in the treatment of swine cysticercosis.

Human Taenia solium cysticercosis is a major cause of epilepsy in developing countries, and porcine infection causes widespread economic losses because of infested pork. Recently, the use of oxfendazole (OFZ) for porcine cysticercosis provided, for the first time, an effective, single-dose treatment. We performed a controlled study to determine the time required between treatment with a single dose of OFZ and the death of cysticerci to define its applicability as preslaughter treatment or as a field control measure. Twenty naturally infected pigs were included in this study. Sixteen received a single dose (30 mg/kg) of OFZ, and were killed in groups of four at one, two, four, and 12 weeks after treatment. Four untreated controls were killed at week 12. No adverse reactions to OFZ were noted. A clear decrease in viability and number of cysts was evident after the first week after therapy, but even at week 4 some viable cysticerci were found in all samples. Twelve weeks after treatment, all meat appeared clear and only minuscule scars remained, except in one animal that had viable brain cysts. This study confirms the efficacy of a single dose of 30 mg/kg of OFZ for porcine cysticercosis but demonstrates that preslaughter treatment of pigs with OFZ will not be useful in controlling cysticercosis. The inclusion of porcine treatment with OFZ in mass cysticercosis control programs is, however, highly promising because it is a simple, effective, inexpensive, and potentially sustainable method for decreasing the porcine reservoir of cysticercosis in disease-endemic countries.

Increased prevalence of cysticercosis and taeniasis among professional fried pork vendors and the general population of a village in the Peruvian highlands. Cysticercosis Working Group in Peru.

Two different populations in Saylla, a Peruvian village near Cusco, known for chicharrones, a local pork dish, were surveyed by serology and stool examination to determine the prevalence and epidemiologic characteristics of Taenia solium infection. Group I (n=43), the chicharroneros, were members of families professionally devoted to the making and selling of chicharrones, and Group II (n=102) was a sample of the general population of the same village. Unlike people in Group I, general villagers only occasionally prepare or sell this food product, and then only to their neighbors or relatives. The prevalence of taeniasis was extremely high (8.6%) for the chicharroneros and 3% for the general villagers. Seroprevalence for cysticercosis by immunoblot was similarly high in both groups (23.3% and 23.8%, respectively). Being female, older than 30, and having daily contact with pork were factors strongly associated with a positive serologic result for cysticercosis in the chicharroneros, whereas males were more frequently seropositive in the general villagers group. Antibody reaction to more antigen bands in immunoblots and neurologic symptoms were more common among the chicharroneros. Also, in the general villagers group, seroprevalence increased with each exposure factor, ranging from 9.4% in individuals who did not raise pigs to 50% in the small subgroup that raised pigs, butchered their own animals, sold pork, and sold chicharrones, suggesting that these activities are related to increased risk for tapeworm or larval infection.

Treatment of porcine cysticercosis with oxfendazole: a dose-response trial.

Taenia solium cysticercosis is an important public health problem in developing countries. Oxfendazole has been shown to be highly effective against porcine cysticercosis, when given as a single dose at 30 mg/kg bodyweight. This dose, however, was estimated from experience with albendazole. A controlled dose-response trial was therefore undertaken to determine the efficacy and safety of three concentrations of oxfendazole. Twenty-four naturally parasitised pigs were divided into four groups and treated with oxfendazole at 10 mg/kg, 20 mg/kg or 30 mg/kg, or left untreated. Eight to 10 weeks later the pigs were killed and the viability of the parasites assessed by evagination. No side-effects of oxfendazole treatment were observed. In the control group more than 90 per cent of the cysts were viable. Viable cysts were found in the muscle and brain of the pigs treated with 10 or 20 mg/kg oxfendazole. At 30 mg/kg there were no viable cysts in any of the tissues examined, indicating that this concentration of oxfendazole provided an effective treatment against porcine cysticercosis.

Effective, single-dose treatment or porcine cysticercosis with oxfendazole.

The pig is a vital link in the transmission cycle of Taenia solium, the cestode responsible for human-porcine cysticercosis. Infected pigs also represent an important source of economic loss to farmers in developing countries. Past efforts to find an adequate therapeutic regimen to treat this parasite disease in swine have failed because of low efficacy, high cost, side effects, or the need for multiple doses. In this randomized, no treatment-controlled study, the efficacy and safety of oxfendazole and praziquantel for the treatment of porcine cysticercosis were evaluated in 16 naturally infected pigs. Four groups of four pigs were treated with oxfendazole, praziquantel, oxfendazole plus praziquantel, or untreated. The pigs were humanely killed 12 weeks post-treatment, the number of cyst was counted, and parasite viability was assessed by cyst evagination. No detectable side effects were seen in any of the pigs. Praziquantel treatment alone appeared to reduce the number of cysts, but did not decrease the viability of the remaining parasites. Treatment with oxfendazole alone or oxfendazole plus praziquantel killed all of the parasites, and left only microcalcifications in the meat. Oxfendazole provides, for the first time, a practical, effective, inexpensive, and single-dose therapy for porcine cysticercosis.

Treatment of porcine cysticercosis with albendazole.

In a randomized, controlled study, the efficacy and safety of two different schemes of albendazole therapy for treatment of porcine cysticercosis were tested. Seventeen naturally infected pigs were divided into three groups and treated per os with albendazole (50 mg/kg single dose), albendazole (30 mg/kg every day for three days), or given no treatment, respectively. Serologic responses were monitored with the enzyme-linked electroimmunotransfer blot assay. Pigs were humanely killed 12 weeks after treatment, necropsied, and the number of parasites was recorded. Scolex evagination was used to assess viability of the cysts. Both albendazole-treated groups had significant side effects (anorexia, lethargy). Only a single viable cyst was recovered from the brain of one animal after therapy in the multiple-dose group, and the single-dose therapy left 11% of the cysts viable. In contrast, more than 90% of muscle cysts were found to be viable in the untreated group. Although albendazole therapy for three days was found to be highly effective, side effects and the need for multiple doses would still prevent its widespread use.

Use of sentinel pigs to monitor environmental Taenia solium contamination. The Cysticercosis Working Group in Peru (CWG).

We tested a novel approach to assay Taenia solium prevalence using the enzyme-linked immunoelectrotransfer blot assay in sentinel piglets to determine environmental contamination with T. solium eggs in a disease-endemic zone in Peru. Twelve sentinel piglets from an area where the disease is not present were tested at two months of age, moved to an area where the disease is endemic, and retested at the of age nine months. Sentinel piglets native from this T. solium-endemic area were also tested concurrently at two and nine months of age. Of the non-native pigs, 33% (4 of 12) acquired new infection. Of the 28 native pigs tested, 64% (18 of 28) acquired the infection. In a subset of the native piglets from seronegative sows, 44% (4 of 9) were infected at five months of age. Serodiagnosis of sentinel piglets is a practical method to detect T. solium eggs in the environment. Furthermore, it permits indirect assessment of human risk, which may be useful for monitoring the efficacy of intervention programs.