Alternative food and external source of infection stabilize predator-prey oscillations -- A conclusion drawn from an eco-epidemiological model

Das et al. [Effect of disease-selective predation on prey infected by contact and external sources, Biosystems 95（3） （2009） 188-199] proposed an eco-epidemiological model where the prey species is infected through the external source of infection and contact of the species. In this present study we have modified their model by assuming that the predator consumes both the susceptible as well as the infected prey following the modified Holling type-Ⅱ functional response. Our main focusing points of this study are the role of infection rate （both internal and external）, alternative food, and half-saturation constant in the predator prey dynamics with disease in the prey population. We have shown the local stability of the boundary as well as the interior equilibrium point under certain conditions. We have Mso worked out the permanence of the system. Our simulation results show that the system enters into limit cycle oscillations from stable position for higher values of the contact rate. But it is also shown that the external infection rate, enrichment of the alternative food of the predator population and the half-saturation constant can prevent limit cycle oscillations and stabilize the system. Thus external dis- ease propagation, enrichment of the alternative food resource, and the half-saturation constant are the key factors for preventing the oscillatory behavior of the species.

Interruption of schistosomiasis transmission in mountainous and hilly regions with an integrated strategy:a longitudinal case study in Sichuan,China

Background:Schistosomiasis remains a major public health concern in China.Since 2004,an integrated strategy was developed to control the transmission of Schistosoma japonicum in China.However,the long-term effectiveness of this integrated strategy for the interruption of schistosomiasis transmission remains unknown in the mountainous and hilly regions of China until now.This longitudinal study aims to evaluate the effectiveness of the integrated strategy on transmission interruption of schistosomiasis in Sichuan Province from 2005 through 2014.Methods:The data regarding replacement of bovines with machines,improved sanitation,access to clean water,construction of public toilets and household latrines,snail control,chemotherapy,and health education were captured from the annual report of the schistosomiasis control programmes in Sichuan Province from 2005 to 2014,and S.japonicum infection in humans,bovines and snails were estimated to evaluate the effectiveness of the integrated strategy.Results:During the 10-year period from 2005 through 2014,a total of 536568 machines were used to replace bovines,and 3284333 household lavatories and 15523 public latrines were built.Tap water was supplied to 19116344 residents living in the endemic villages.A total of 230098 hm2 snail habitats were given molluscicide treatment,and 357233 hm2 snail habitats received environmental improvements.There were 7268138 humans and 840845 bovines given praziquantel chemotherapy.During the 10-year study period,information,education and communication(IEC)materials were provided to village officers,teachers and schoolchildren.The 10-year implementation of the integrated strategy resulted in a great reduction in S.japonicum infection in humans,bovines and snails.Since 2007,no acute infection was detected,and no schistosomiasis cases or infected bovines were identified since 2012.In addition,the snail habitats reduced by 62.39%in 2014 as compared to that in 2005,and no S.japonicum infection was identified in snails since 2007.By 2014,88.9%of the endemic counties achieved the transmission interruption of schistosomiasis and transmission control of schistosmiasis was achieved in the whole province in 2008.Conclusion:The government-directed and multi-department integrated strategy is effective for interrupting the transmission of schistosomiasis in the mountainous and hilly regions of China.

Assessment of echinococcosis control in Tibet Autonomous Region,China

Background:In China the highest prevalence of echinococcosis is in Tibet Autonomous Region(TAR).The government has issued documents and implemented comprehensive prevention and control measures focusing on controlling the source of infection of echinococcosis.It was very important to understand the implementation and effect of infectious source control measures.The purpose of this study was to examine the implementation of measures to control infectious source(domestic and stray dogs)in TAR and to assess their effectiveness.Methods:We collected data on domestic dog registration and deworming and stray dog sheltering in 74 counties/districts in the TAR from 2017 to 2019.Fecal samples from domestic dogs were collected from randomly selected towns to determine Echinococcus infection in dogs using coproantigen ELISA.We analyzed the data to compare the canine rate of infection between 2016 and 2019.The data analysis was performed by SPSS statistical to compare dog infection rate in 2016 and 2019 by chi-square test,and ArcGIS was used for mapping.Results:From 2017 to 2019,84 stray dog shelters were built in TAR,and accumulatively 446,660 stray or infected dogs were arrested,sheltered,or disposed of.The number of domestic dogs went downward,with an increased registration management rate of 78.4%(2017),88.8%(2018),and 99.0%(2019).Dogs were dewormed 5 times in 2017,12 times in 2018,and 12 times in 2019.The dog infection rate was 1.7%(252/14,584)in 2019,significantly lower than 7.3%(552/7564)from the survey of echinococcosis prevalence in Tibet in 2016(P<0.05).Conclusion:Between 2017 and 2019,the number of stray dogs and infection rate of Echinococcus spp.in domestic dogs decreased significantly,indicating that dogs were effectively controlled as a source of infection in TAR and reflecting a significant decrease in the risk of echinococcosis transmission.

Approaches being used in the national schistosomiasis elimination programme in China:a review

Schistosomiasis japonica,caused by the human blood fluke Schistosoma japonicum,remains a major public health problem in China,although great success has been achieved.The control efforts during the past half-decade,notably the wide implementation of the new integrated strategy with emphasis on control of the source of S.japonicum infection across the country since 2004,has greatly reduced S.japonicum in humans,livestock,and intermediate host Oncomelania hupensis snails,and transmission control of schistosomiasis was achieved in China in 2015.A two-stage roadmap was therefore proposed for schistosomiasis elimination in 2015,with aims to achieve transmission interruption by 2020 and achieve disease elimination by 2025 in the country.During the last two decades,a variety of approaches,which target the epidemiological factors of schistosomiasis japonica have been developed,in order to block the transmission cycle of the parasite.These approaches have been employed in the national or local schistosomiasis control activities,and facilitated,at least in part,the progress of the schistosomiasis elimination programs.Here,we present an approach to control the source of S.japonicum infection,three new tools for snail control,three approaches for detecting and monitoring S.japonicum infection,and a novel model for health education.These approaches are considered to play a great role in the stage moving towards transmission interruption and elimination of schistosomiasis in China.