Who knew what poo could do
What we flush down the toilet every day can tell a population-health story. ESR's Dr Joanne Hewitt explains.
Imagine a test that could detect just one case of a virus among a city of 80,000 people. Imagine how that test could be applied to other population health issues, from Covid-19 to community drug use. That vision is what Porirua’s Crown Research Institute ESR, turned in to a reality when senior scientists pitched waste-water testing to government as an epidemiolgical and genetic tool in the midst of the Covid-19 pandemic.
Clues in our poo | What we flush down the toilet every day can tell a population-health story. Everything that enters our body, exits containing traces of what we consume and encounter in the environment, from the food we eat, to the bacteria and viruses that might infect us.
In the early days of the Covid-19 pandemic, scientists in the Netherlands used wastewater testing – a tool that’s been around for half a century – to monitor the virus in the community (the virus that causes Covid-19 was detected shortly after the first case was reported). This caught the attention of ESR scientists in New Zealand. With numbers of infections believed to be small and contained here, could wastewater testing be used throughout the country to ensure that we were indeed, Covid-free?
It was a pitch in May 2020 that would go on to save lives and illuminate the usefuless of surveying just what’s in our poo. When areas with no known cases of the virus pinged positive for Covid-19 through wastewater surveillance, there was no doubting that the virus was there. This helped both contain the virus regionally, and reassure that other places were definitely Covid-free.
Senior scientist Dr Joanne Hewitt is a super sleuth when it comes to poo. She’s spent 25 years helping track and contain infectious diseases, from norovirus to hepatitis A.
“At the moment we have a hepatitis A outbreak in New Zealand. Hepatitis A is not endemic (always present) here, so for every case, we take that person’s blood and/or poo, and we genetically sequence it to get the genome of that specific virus. Then we look to see if it’s connected to any other cases – is it geographically linked? How are they related if there is more than one?
"This is exactly the same process that was used for Covid-19 in 2020 and 2021.”
Purposeful testing | While wastewater testing doesn’t currently look for the hepatitis A virus, it easily could, although Joanne says there have to be good reasons for looking for other targets: “You have to know what you’re doing wastewater surveillance for and have an action plan in place.”
Testing was previously used in Aotearoa with the changeover from the oral polio vaccine to the inactivated one in the early 2000s. “Through testing we could see traces of the oral polio vaccine slowly disappear from our wastewater.”
With the oral polio vaccine still in use in some countries, and vaccination rates lower than they should be globally, outbreaks of vaccine-derived polio have been reported in places previously deemed polio free – and it is wastewater testing that has revealed the virus’s silent presence.
Another surprising application for wastewater surveillance is the monitoring of illicit drug use in the community. This is done by ESR for the Police. “Rather than testing for a drug itself such as methamphetamine, we look for converted chemical compounds that are produced by the body instead. These are called metabolites. By testing different sites, authorities can learn about patterns of drug use and use that information to potentially home-in on vulnerable areas.”
Testing is not about drug busts but about proactive education. “If you don’t know what drugs are where you can’t help. It just provides an extra level of intelligence.”
So what other applications can wastewater testing be used for? Joanne says that testing for influenza viruses and respiratory syncytial virus (RSV) are both on the cards for future focus. “We’re hoping to trial testing in the next 12 months and use it to predict when cases are going up. This would help with pre-warning and planning. We learned so much with Covid-19, it’s been a really, really useful tool. Wastewater testing changed attitudes. People became aware of rising numbers and changed their behaviour. It definitely saved lives.”
Who knew what poo could do.