ABSTRACT
Objective To investigate the sensitivity of adult worms of filial generations from praziquantel-resistant and -sensitive Schistosoma japonicum mixed infections to praziquantel. Methods Mice were infected with the cercariae of an experimentally generated praziquantel-resistant S. japonicum isolate [median effective dose (ED50) = 277.4 mg/kg] and a laboratory-maintained praziquantel-sensitive S. japonicum isolate (ED50 = 99.6 mg/kg) at a mixture ratio of 1:1 and 2:1, which was maintained in the laboratory via the mouse-snail cycle for 8 generations. Then, mice were infected with the cercariae of the 8th filial-generation parasite, and grouped 35 days post-infection. Mice in the 5 treatment groups were given praziquantel treatment by gavage at a single oral dose of 37.5, 75, 150, 300 mg/kg and 600 mg/kg, while animals in the control group was administered orally with 2.5% cremophor EL. All mice were sacrificed 14 days post-treatment and adult worms were collected by perfusion of the portal vein. The worm burden reductions and praziquantel ED50 values were calculated. The praziquantel-resistant S. japonicum isolate generated from experimental induction with 12 rounds of praziquantel treatment with sub-curative doses was maintained in the laboratory via the mouse-snail cycle, and mice were infected with the cercariae of the 8th filial-generation parasite. The praziquantel ED50 value against the 8th filial-generation adults was measured. Results After mice were infected with the mixture of cercariae of PZQ-resistant and -sensitive S. japonicum isolates at a ratio of 1:1, the praziquantel ED50 was 135.2 mg/kg against the adults of the 8th filial-generation parasite. After mice were infected with the mixture of cercariae of PZQ-resistant and -sensitive S. japonicum isolates at a ratio of 2:1, the praziquantel ED50 was 129.2 mg/kg against the adults of the 8th filial-generation parasite. In addition, the praziquantel ED50 was 208.4 mg/kg against the adults of the 8th filial-generation S. japonicum without the selection pressure of praziquantel. Conclusions Compared with the experimentally induced praziquantel-resistant S. japonicum isolate, the adult worms of the filial-generation S. japonicum show a reduced sensitivity to praziquantel in the same host following infection with the mixture of cercariae of praziquantel-resistant and -sensitive S. japonicum isolates. The adult worms of the filial generation of the praziquantel-resistant S. japonicum isolate without the selection pressure of praziquantel may still maintain the resistance to praziquantel.
ABSTRACT
Objective To investigate the prevalence and changing patterns of Schistosoma japonicum infections in goats in Dantu District of Zhenjiang City, so as to provide the scientific data for the management of in livestock. Methods The S. japonicum infections were detected using a miracidial hatching test (one test for one stool specimen) in goats grazed in settings with snail habitats in Dantu District of Zhenjiang City at spring and autumn of each year from 2004 to 2019, and the prevalence and intensity of S. japonicum infections were estimated. Results A total of 21 836 goat stool samples were detected from 2004 to 2019, and 86 were positive for S. japonicum (0.39% prevalence). The highest prevalence of S. japonicum infections in goats was seen in 2004 (1.25%) and no infections were detected in goats since 2013. S. japonicum-infected goats were identified in marshland-type endemic areas and plain regions with waterway networks, and there was a significant difference in the prevalence of S. japonicum infections in goats between these two types of endemic areas (0.50% vs. 0.15%; χ2 = 11.566, P < 0.05). The prevalence of S. japonicum infections was significantly greater in goats at ages of more than 10 months (0.51%) and over 10 months (0.44%) than in other goats (χ2 = 13.088, P < 0.05), and higher prevalence was found in autumn than in spring (0.54% vs. 0.27%; χ2 = 9.597, P < 0.05). In addition, there were 76.74% of S. japonicum-infected goats with intensity of“+++”and“++++”. Conclusions Although the high prevalence of S. japonicum infections has been effectively controlled in goats in Dantu District, goat remains to be an important source of S. japonicum infections that should be given a high priority for control to consolidate the schistosomiasis control achievements.