A Multidisciplinary Approach to Parasitic Diseases: Tuesday, January 21st

Armando E. Gonzalez, PhD, is the head of the Veterinary Epidemiology and Economics Laboratory at the San Marcos School of Veterinary Medicine in Peru.  He obtained a Master degree in microbiology from San Marcos and his PhD in veterinary epidemiology and economics at the University of Reading.  He holds an Associate Appointment at the Bloomberg School of Public Health (Johns Hopkins University), and is currently the president of the Peruvian Academy of Veterinary Sciences.  Dr. Gonzalez devotes his time to the study of the control and transmission of cysticerosis, and the tapeworm Taenia solium.  Specifically, his research examines the transmission of zoonotic cestodes and the role that invertebrates play in T. solium egg dispersion.  His talk at the North Carolina One Health Intellectual Exchange centered on the epidemiology of T. solium, as well as, intervention and control techniques used in multidisciplinary approaches to parasitic diseases. 

Dr. Gonzalez began his talk with a brief explanation of the zoonotic cestode parasite T. solium’s life cycle.  T. solium infection, and the resulting disease cysticerosis, is prevalent in less developed regions throughout the world including Latin America, Asia, and sub-Saharan Africa.  High transmission rates are associated with poor sanitation and hygiene, poverty, low living standards, poor waste disposal, and primitive pig husbandry sites.  Pigs become infected when they consume gravid proglottids (T. solium eggs), that are contained in the human feces.  These pigs act as the intermediate host and develop porcine cysticerosis.  Humans, the definitive host, then ingest viable cysts when eating undercooked meat and develop Taeniasis.  Human intestinal cysticerosis is generally asymptomatic; however, when humans acquire the larval stage through the ingestion of eggs, neurological problems develop. 

Dr. Gonzalez argued that continual porcine infection reflects the poor development state of endemic areas, and that the only long-term sustainable solution and control strategy to eradicate this infection is to improve development.  Dr. Gonzalez supports this argument by stating the failure of the World Health Organization’s strategy: slaughterhouse control, which lacks sustainability and only removes 3% of cases.  Other tested control strategies included mass human chemotherapy, which decreased prevalence but lacked sustainability; health education; and immunotherapy.  Other alternatives included pig treatment, pig corralling, pig vaccination, pig re-population, and refinement of how meat is processed.  Examples of Peruvian methods involved killing the tapeworm and treating infected pigs, a solution that included both medical doctors and veterinarians, yet still showed no success.  Nonetheless, this collaboration between professionals was later key to the elimination of T. solium.  

However, research results noted a matched interval incidence pattern that occurred for both control and intervention areas, suggesting an unknown variable or mechanism of transmission.  A simulation model was developed, and it was concluded that the control methods mentioned above are not sustainable because T. solium returns to endemic stability after only two years following control interventions.    

Dr. Gonzalez aimed to develop and evaluate a new control strategy based on serologic identification, mass targeted chemotherapy, and evaluation of efficacy.  His research, and work with the board of the Cysticerosis Working Group in Peru, is responsible for transmission interruption of T. solium in an area with 100,000 inhabitants.  This control strategy involved the collaboration of veterinarians and medical doctors and provides an ideal example of a successful One Health type approach.  The team eliminated cysticerosis using 4 rounds of Oxfendazole on pigs and two rounds of human chemotherapy with 142 days between human interventions. 

GIS technology was used to further examine two rural Peruvian villages.  The data revealed that 35% of pigs were infected with Spiruroid nemotodes (Ascarops strongylina), a pig parasite which utilizes dung beetles as an intermediate host.  The odds of the pigs having viable cysts increased nearly four times in pigs with Ascarops strongylina compared to those without.  Additional evidence for dung beetles as a potential source of the infection came from the discovery that T. solium eggs were found to remain viable in the dung beetle’s intestine for at least one week following ingestion.  Dr. Gonzalez noted that T. solium proglottids do not move and are very sticky; therefore this discovery is crucial to understanding the dispersion and transmission of cysticerosis.  Additionally, only a small number of alpha male pigs consume human feces, which indicates that another dispersion route in addition to pigs consumption was involved.

If this is true and invertebrates are involved, Dr. Gonzalez argued that control and elimination activities will not change.  However, this knowledge will be taken into account for more intensive veterinary inspection, corralling, diagnostic inspections, and tongue examinations. Dr. Gonzalez concluded his talk by arguing the importance of a multidisciplinary approach that involves medical doctors, veterinarians, biologists, mathematicians, entomologists, sociologists, and environmentalists to solve not only parasitic diseases, such as cysticerosis, but many health problems that plague the world.

Blog Post authored by: Emma Seagle (UNC)