Parasites in human waste fertilizers alarm health experts

It has been suggested that human faeces used as fertiliser on farms are leading to the spread of ‘Third World’ parasites causing a serious stomach illness across Sydney.

Health experts fear the Sydney Water Biosolids Strategy, which turns 180,000 tonnes of human waste into fertiliser yearly, could be behind the emergence of stomach bug, Blastocystis hominis, usually found in dirty water in ‘Third World’ countries and spread via faeces, and a second parasite which often accompanies it, Dientamoeba fragilis. Both parasites lead to stomach cramps, extreme pain, distended stomach, diarrhoea, weight loss and fatigue they warn.

Over the last four months there have been confidential microbiology tests, signed off on by Sydney Water, that detected D. fragilis in one in five samples of primary wastewater. The tests did not look for Blastocystis hominis. Solid waste removed from the sewage is turned into biosolids and sent to 20 farms in NSW to enrich soil under a sustainability program.

According to Professor Kerryn Phelps, former head of the Australian Medical Association there is need for an independent inquiry into the practice after detecting an increasing number of patients with the parasites in their gut. “I've noticed an increase in these pathogens in people who have not travelled overseas,” she said. “One hundred and eighty thousand tonnes of partially treated sewage is being used as fertiliser annually and the program had not been independently assessed…From a public health point of view, we have what appears to be a significant problem,” she warned.

Switzerland and Austria have banned the use of sewerage sludge as fertiliser, while in Sweden and parts of Germany, supermarkets do not stock products treated with biosolids. According to three studies, published in international medical and public health policy journals, residents living near land where biosolids are used suffered a statistically higher rate of illness.

In a recent 2007 survey of residents living near Ohio farm fields which use biosolids, published in the international journal, Archives of Environmental & Occupational Health, authors wrote, “Results revealed that some reported health-related symptoms were statistically significantly elevated among the exposed residents. The findings suggest an increased risk for certain respiratory, gastrointestinal and other diseases among residents living near farm fields on which the use of biosolids was permitted.”

According to leading gastroenterologist, Professor Thomas Borody, who carried out research supporting the team that won a Nobel Prize for cure of stomach ulcers, said there needs to be an investigation into the biosolids program to give the public certainty that human faeces is not infecting our food supply. He said in the past 10 to 15 years, 1500 people had been diagnosed with D. fragilis and Blastocystis in his practice. “If we are going to be using foods grown on crops which use these biosolids it would be good to have a certain level of assurance that they are not carrying pathogens,” he said. He said the parasite Blastocystis homonis was difficult to kill in humans. “The problem, apart from parasites, is viruses…Faecal matter transmits viruses that give you diarrhoea. What worries us more is the sporadic case of Hepatitis B and C when you do not know how it has been caught. Some people have never used needles,” he said.

However, NSW Health has not reviewed the potential health impacts of the program nor conducted tests on the farms where soil has been fertilised with human faeces. Despite the discussion in medical journals about the transmission of D. fragilis, Sydney Water's spokesman said the bug was not a concern and was unlikely to survive for long outside the human body. “Sydney Water is unaware of any cases of illnesses directly caused by biosolids,” the spokesman said.

Former general manager of Pittwater City Council, Angus Gordon, who retired in 2006, said NSW Health advised him not to use biosolids on sports ovals because it was not safe around children. “The problem with biosolids was, at the time we were being advised, that there was the possibility of pathogens being within the biosolids…We were asking the question: if we were to use this material would it be safe for people, particularly children, to play on those fields, given that people do sustain injuries and grazes? At the time we rejected it on the basis that we weren't able to get the assurances,” he said.

NSW Health's spokesman said if Environmental Protection Agency (EPA) guidelines were adhered to, the use of biosolids was unlikely to present a risk to public health. The guidelines span over 92 pages and state that if biosolids are used on agricultural land, crops - from potatoes to lettuce and turf - should not be grown for between 18 months and five years. There is also a 30-day harvesting rule for animal feed and fibre crops. “Where there is a high potential for public exposure, access should be restricted by fencing and signing for one year after biosolids application,” the guidelines state.

Sydney Water's water quality and public health program manager Peter Cox said, “What we do is we manage the guidelines to make sure that the biosolids are safe for the purpose that they are used…Pathogens can exist in very low numbers but not enough to cause any harm…There are lots and lots of pathogens and it will depend on the individual bit of biosolid that you pick up to analyse. The whole management of biosolids, which includes treatment and potential for exposure, is there so that it doesn't cause a risk to health.” Sydney Water does not conduct testing on its biosolids for the two parasites and would not reveal which pathogens, if any, it does test for. “We don't routinely test for things that are not required for us to test in the guidelines,” Mr Cox said.

Blastocystis Research Foundation director, Ken Boorom said a large number of patients who were complaining of a variety of symptoms including fatigue, erratic bowel function, nausea and bloating. Many diagnosed with ‘irritable bowel syndrome’ were discovered to have one or several parasites.

The CDC describes Dientamoeba fragilis: Dientamoeba fragilis is a parasite that causes gastrointestinal problems. Despite its name, Dientamoeba fragilis is not an ameba but a flagellate. This protozoan parasite produces trophozoites; cysts have not been identified. Infection may be either symptomatic or asymptomatic.

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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