Echinococcosis transmission mainly occurs in the pastoral and farming-pastoral regions of western China due to the complex animal populations and Echinococcus spp., which involve a wide range of intermediate and definitive hosts, Human epidemiological surveys may be carried out by serology, and ultrasonography is regarded as a simple, safe and reliable diagnostic tool for screening for internal cysts. Importantly, relatively safe and effective chemotherapy is available [24-25, 34-41].
The data in this study demonstrate that the grand total person-hours spent on surgical interventions and treatment (including postoperative treatment) was 76.6% of the corresponding grand total proportion for the year of 2014, which was 1.2-fold compared to 2005. These results show a high disease burden in terms of DALYs in the endemic areas, which indicates that echinococcosis is a serious threat in parts of China. However, with the large-scale population screening, the patient numbers increased 18-fold in 2014 compared to 2004, while the prevalence per 100 000 population rate increased 17-fold at the county level and 10.8 times at the township level during the same time. Moreover, 1.5 as many new cases were found, and the cumulative cases (expressed in person-hours) for surgical operations increased 4.2 times, which was 3.8 times the value for CE and 8.1 times the value for AE. For treatment (expressed in person-hours), the cumulative cases increased 5.7 times the value for the CE cases and 3.3 times the value for the AE cases for the last 5 years (2009-2014) compared to the former 5 years (2004-2008). In addition, increases of 0.6 times co-infection with surgical interventions and 0.5 times the co-infection cases with treatment for the last 3 years (2012- 2014) were sustained compared to the former 3 years (2010-2011). For the unclassified cases, the cumulative cases were 13.7 times the value obtained with respect to surgical interventions and 6.3 times the value obtained for treatment for the last 4 years (2011- 2014) compared to the former 3 years (2008-2010).
According to the mean prevalence rate at the county and township level, more diagnosed patients will be reported with a higher prevalence following a large-scale population screening; however, the characteristics of the co-infection cases and the unclassified cases treated during an additional 3-year period decreased by one-half. The results indicate that patients with co-infection and unclassified cases display an annual decreasing trend. Moreover, the patient treatments varied widely due to improvement of the diagnostic accuracy through ultrasound screening for the entire exposed population in high-risk areas. Therefore, patient diagnosis and management, including surgery and treatment with albendazole in endemic areas, are sustainable, whereas established surveillance systems for population prevalence and relevant factors need improvement at different levels, including compliance with respect to albendazole treatment, clinical follow-up, personal information and timely treatment updates of record.
Dogs are definitive hosts in the semi-domestic life cycle of E. multilocularis and play a key role due to their close association with E. granulosus throughout parasite transmission in the endemic areas of western China [11,13;18-19]. Since 2005, the echinococcosis control initiative in China provides complete data for the management of registered dogs including deworming of infected dogs. Over the 7-year period of 2005-2011, the number of registered dogs increased 9-fold, but the deworming coverage rate only increased 8-fold in 2011 compared to the rate in 2005. However, according to the complete data records of registered dogs from 2012 to 2014, the coverage rate remained near 70% and exhibited an estimated 7-fold increase compared to 2005. These results were similar to those of the 2012-2014 period. Additionally, monthly anthelmintic treatment for dogs was more effective compared to previous studies [20-21]. Data for the annual number of dogs deworming with dog-time calculated for large-scale deworming for the registered dogs increased 1.7-times in 2014 compared to 2012 and was estimated at 12 times per dog per year for 2014. In conclusion, the estimation of dog management and treatment over this period was performed at completely different levels on an annual timeline and helped reduce the parasite load to control the disease.
Notably, a strong relationship exists between patients and dogs, which means that there is a high risk that humans ingest parasite eggs directly through contact with infectious dogs or indirectly from contaminated environments. Studies also reveal that E. granulosus eggs remain viable and infective after 41 months that include warm summer and cold winter conditions [1,2,12-13]. We also found that a positive correlation (R=0.97, P <0.01) between registered dogs with the available patients after Spearman's correlation analysis of the present data. Currently, the management of stray dogs is particularly difficult in some regions where cultural acceptance is prevalent, several studies indicate that distribution of anthelmintic baits against wild and stray definitive hosts results in significant reductions in AE prevalence, particularly if innovative bait delivery is used [26-28,31-32]. According to WHO reports regarding endemic regions, the human prevalence rates for CE can reach more than 50 per 100,000 person-years with prevalence levels as high as 5%-10% worldwide; similar rates have been reported in regions of western China [1,6,15,29-30].
The national echinococcosis control program demonstrates that mass human population screening of echinococcosis, early detection and prompt treatment of human cases and large-scale dog deworming are valuable (particularly with respect to coverage) based on the cost proportion changes, with the exception of limitations of minor values based on the estimation. The results of the simple cost analysis show that over the 10-year period, a total cost of USD 27.0 million after discount on patients treatment and registered dogs deworming was accumulated. It reached 24.4% accounting for 1/4 of the total financial input, though currently they have not adapted to the emerging numbers of patients in need of treatment and dogs that should be dewormed. The annual and the accumulated costs increased 57-fold and 368-fold compared to those in 2005 respectively, and the grand total proportion narrowed by 70% with respect to annual or accumulated gaps, which is in accordance with the annual increase of the cost for patients and anti-parasite treatment of registered dogs.
In this study, due to the limitation of data confidentiality, we only collected data approved by the National Minstry of Health up to 2014, so the four years data after that were not covered and unable to include the distribution of wild canines (stray dogs and etc.) through the national program, which is a critical for blocking parasitic egg transmission. Moreover, although the national control programme was led by National Minstry of Health, the livestock management and vaccination were the responsibility of the Ministry of Agriculture and the outcomes will depend on their reports. In addition, the national surveillance system for echinococcosis was established in 2016, as there were hardly any historical data for analysis to fully reflect the prevalence for patients and dogs, except for the two national surveys in 2004 and 2012.
All in all, based on the results obtained through this study, we recommend that it will be more effectively on the national programme evaluation by multi-sectoral joints in the future, more attention should be paid to controlling wild canines during the ongoing program period and with increased focus on patients and dog interventions by the Chinese Government.