Analysis of vaccination strategy against cystic echinococcosis developed in the Province of Río Negro, Argentina: 12 years of work

A scoping review on control strategies for Echinococcus granulosus sensu lato

Background

Cystic echinococcosis (CE) is a widespread neglected zoonotic disease caused by Echinococcus granulosus sensu lato (EG) with a global burden of control in the billions of dollars. E. granulosus' life cycle involves definitive, intermediate, and humans as dead-end hosts. Echinococcosis control programs use strategies that focus on any of these hosts. We aimed to provide a comprehensive and up-to-date overview of the EG control interventions worldwide.

Methods

We conducted a scoping review by mapping all studies on interventions for EG control following the Arksey and O'Malley Framework. We screened identified articles, and charted and coded selected papers. We classified the data based on target host, type of study, and control mechanism. We described the efficacy or safety outcomes, and the associated barriers/facilitators for the intervention. Critical appraisal was conducted.

Results

From 7,853 screened studies, we analyzed 45: seven centered on human interventions, 21 on animals, and 17 on both. Studies on humans focused on educational strategies and human CE monitoring. The studies on animals were field trials and most were based on Praziquantel (PZQ) for dogs. Studies focused on both animals and humans had, in general, more participants, lasted longer, and covered larger geographical areas. Overall, the quality of studies was moderate to low.

Conclusions

Available evidence suggests that long-term interventions aimed at both animals and humans can achieve significant reduction in EG transmission, particularly when PZQ treatment for dogs is included. Higher quality evidence, standardization of methodologies, and better reporting on post-intervention outcomes are necessary for drawing stronger conclusions. Further evidence is needed to assess the sustainability and scalability of control measures. Nonetheless, an integrative One Health approach is essential for overcoming the multiple challenges associated with sustaining long-term control efforts for Echinococcosis.

Funding

RCN was supported by the National Institute of Allergy and Infectious Diseases (grant nos. K01AI139284 and R01AI168291). LOC, JAB, and RCN were supported by the Fogarty International Center (grant no. D43TW012741). TAD, CG and JAB were supported by the Fogarty International Center (grant no. D43TW001140).

Author Summary

Cystic echinococcosis is a disease caused by the parasite Echinococcus granulosus sensu lato . This parasite can be found in specific areas on all continents, especially in poverty-stricken regions, increasing costs and losses. Some countries have achieved control, but most are still in the process. Our review provides a clear picture of what we currently know about these control strategies and points out where more research is needed. It highlights how the findings can improve control practices by showing what works best and address practical challenges. The review also identifies gaps in current knowledge and suggests that comparing different control methods could help find the most effective and cost-efficient solutions. Key areas needing attention include increasing support and funding for echinococcosis, as the disease is often overlooked. More research from different fields is needed to better understand and manage the disease's complexities. Better and ongoing surveillance is crucial for maintaining effective control strategies. Finally, comprehensive reviews that bring together findings from different studies are needed to identify what works best and improve and combine future control efforts.

Echinococcus granulosus sensu lato control measures: a specific focus on vaccines for both definitive and intermediate hosts

Echinococcosis, a neglected zoonotic disease caused by Echinococcus tapeworms, presents significant public health challenges worldwide. Cystic and alveolar echinococcosis has substantial health and economic impacts, necessitating effective prevention and control strategies. The present review provides a framework to expand our knowledge regarding key components of echinococcosis prevention and control, including phases, options, targets and available tools as well as current gaps and challenges in the field. Furthermore, we discuss the progress made in developing vaccines for the intermediate and definitive hosts and review the limitations and obstacles in vaccine development for definitive hosts. Abundant information is available on various aspects of the Echinococcus vaccine in sheep. Livestock vaccination effectively reduces Echinococcus transmission to sheep, offering a feasible control measure in intermediate hosts. However, vaccine development for the definitive host, i.e. dogs, exhibits significant challenges. Information gaps regarding the immune-mediated protective responses in dogs, repeatability of results, factors influencing the immune response, reinfection resistance, potential age-related decreases in worm burden and factors associated with the antifecundity effect are key challenges that should be addressed in canine vaccine development, and research collaboration, innovative technologies, and a deeper understanding of transmission dynamics are crucial. Multisectoral coordination under the One Health framework, with long-term political commitment and national and international cooperation, is critical for effective control in endemic areas.

Successful control of Echinococcosis in Argentina and Chile through a One Health approach, including vaccination of the sheep intermediate host

Cystic echinococcosis control in South American countries requires a comprehensive integrative ‘One Health’ approach. While insular nations have seen successful in their elimination programmes, South American countries face persistent challenges in hostile environments, with Echinococcus granulosus s.l., posing a significant public health concern. Vaccination of intermediate hosts has demonstrated the efficacy of the EG95 vaccine in reducing transmission rates. For example, since 2009, Rio Negro Province in Argentina has added, with marked success, the EG95 vaccine to the control programme, supplementing dog deworming. The Aysen Region of Chile has also reported encouraging preliminary results in reducing cyst prevalence in vaccinated sheep after 3 years of vaccination. The challenges in aligning control strategies with socio-cultural factors, especially in indigenous communities, underlines the need for context-specific strategies. The Rio Negro programme demonstrated commendable compliance, underlining the importance of community engagement in achieving lasting success. The most promising strategies for effective echinococcosis control involved dog deworming and the routine vaccination of sheep and/or goats, underscoring the importance of sustained implementation until all grazing animals have been replaced. For lasting success, these interventions need to be combined with a robust surveillance system.

Nanoparticle formulation for the development of a dog nanovaccine against Cystic Echinococcosis

Cystic Echinococcosis is a cosmopolitan zoonosis closely linked to poverty and ignorance. It affects both cattle and humans, causing significant losses to both human and animal health. To date, there is no effective way to combat this. Our proposal focused on the formulation of poly (lactic-co-glycolic acid (PLGA) and Eudragit-RSPO polymeric nanoparticles, which are suitable to encapsulate an antigen for oral administration in dogs. This antigen, named EgFABP1, belonging to the family of fatty acid-binding proteins, was isolated from the larval form of the parasite Echinococcus granulosus. Several reports point to proteins from this family from parasitic flatworms as candidates for a successful vaccine, considering the restricted lipid metabolism of these organisms. The encapsulation of the antigen yielded an efficiency higher than 50 %, and the nanoparticles showed the expected size range. In addition, antigen integrity was conserved and the formulation was resistant to artificial gastric and intestinal fluid effects.