- Charles Sturt University researchers have published ground-breaking research that will assist with the elimination of schistosomiasis – the third most devastating tropical disease, globally
- Schistosomiasis is a neglected tropical parasitic disease and is a major cause of morbidity in Asia, Africa, South America, the Middle East, and the Caribbean
- Between 2005 - 2010 the rates of positive Schistosoma serology in new refugee arrivals to Australia varied from roughly five to 40 per cent
Ground-breaking research by Charles Sturt University, the University of Georgia in the USA and the Research Institute for Tropical Medicine in Manila will assist in saving thousands of lives as part of the global quest to reduce the incidence of schistosomiasis.
The research ‘Towards sustainable control and elimination of schistosomiasis in the Philippines’ was led by Charles Sturt researchers from the Rural Health and Medical Research Institute (RHMRI) in Orange NSW and funded by the National Health and Medical Research Council.
Schistosomiasis can cause a range of symptoms such as abdominal pain, bloating, bloody diarrhea, chills, fatigue and/or fevers and can lead to major cognitive impairment, liver and spleen damage and sometimes death.
The disease ranks as the third most devastating tropical disease in the world and is a major cause of morbidity in Asia, Africa, South America, the Middle East and the Caribbean.
Professor of Medicine and Executive Director of the RHMRI Allen Ross MD, PhD said schistosomiasis is caused by blood flukes of the genus Schistosoma.
“Schistosomiasis is caused by parasitic worms that penetrate the skin of humans and bovines when they come into contact with infested water,” Professor Ross said.
“The intermediate snail host – a particular species of snail about the size of a grain of rice – release a free-swimming larvae stage of the parasite called cercariae into freshwater, which then infects people or bovines when entering the water.”
The research trial focussed on developing a vaccine for bovines (cattle and water buffalo), which act as major reservoir hosts of schistosomiasis, thereby assisting with the elimination of the disease in Asia and Africa.
Professor Ross said the main method of treatment for schistosomiasis currently is praziquantel (PZQ) - a pyrazinoisoquino-line derivative that is used to treat people with this disease.
“However, praziquantel does not prevent reinfection and the development of drug resistance is a constant concern,” Professor Ross said.
Professor Ross said there is no commercially available human vaccine against any of the human schistosomes.
“Overall, by vaccinating bovines we will be able to prevent approximately a third of infections in people by reducing the number of bovines transferring eggs into endemic water that could later hatch and infect humans,” Professor Ross said.
The research trial was conducted over six years from 2012 until 2017 among 18 schistosomiasis-endemic villages comprising 18,221 residents in Laoang and Palapag, Northern Samar, in The Philippines.
Professor Ross lived in rural villages for roughly three-to-four months per year to conduct the trial with a team of approximately 50 medical personnel, including doctors, nurses, midwives and vets.
“We conducted a one-year cross-sectional survey which was followed by a 5-year phase IIIa cluster randomised control trial that was conducted among the 18 schistosomiasis-endemic villages,” Professor Ross said.
“This is the first trial to demonstrate the effectiveness of a bovine vaccine for schistosomiasis in reducing human schistosome infection.”
Professor Ross noted the prevalence of schistosomiasis globally.
“Worldwide it is estimated that more than 250 million people (1 in 30) have Schistosoma infection,” he said.
“During 2005 to 2010 the rates of positive Schistosoma serology in new refugee arrivals to Australia was roughly between five and 40 per cent.”
Professor Ross said the reason his team focussed on trialling a vaccine in bovines to reduce schistosomiasis transmission in Asia was because of the complicated nature of schistosomiasis control in China and the Philippines based on the zoonotic nature of the disease, with bovines acting as major reservoir hosts.
“Sustainable control strategies are required to combat schistosomiasis to overcome rapid reinfection, the potential threat of PZQ resistance, and problems of drug compliance which is currently only at levels of 25 to 40 per cent in China and the Philippines,” Professor Ross said.
“A multifaceted integrated approach targeting transmission pathways for the disease could comprise complementing PZQ treatment with vaccination of bovines and snail control as the key to sustainable control and eventual elimination (defined as the reduction to zero in human incidence).
“In light of their importance as major reservoirs for S. japonicum, vaccination of bovines has been proposed as a tool to assist in long-term prevention, which is supported by mathematical modelling.”
Professor Ross said that vaccination of bovines would be particularly applicable to areas where mechanized farming is unsuitable.
“Vaccination can reduce egg excretion from cattle and buffalo, thereby interrupting transmission from bovines to snails,” he said.
“We are now planning to conduct a larger Phase 3b clinical trial in three endemic zones in the Philippines.”