Wastewater surveillance is a superb device to monitor the presence of particular pathogens effectively earlier than they are often detected via laboratory testing. It has been routinely used for many years for monitoring the polio virus in virtually each nation. Water-borne viruses could be greatest studied via testing sewage samples. If wastewater surveillance gives correct details about the presence of polio virus excreted by people, within the case of different pathogens, as an illustration SARS-CoV-2 virus, it helps present info on new variants and virus load which serves as a proxy for the extent of virus unfold in the neighborhood. The largest benefit of wastewater surveillance is that it’s cost-effective and may independently affirm the presence of pathogens earlier than laboratory testing throws up a warning sign.
For occasion, wastewater surveillance carried out by the Tata Institute for Genetics and Society (TIGS) in Bengaluru was ready to detect a silent wave of the XBB.1.16 Omicron variant within the metropolis final yr. The virus variant started growing in early-March final yr and peaked on April 1.
With the usefulness of wastewater surveillance through the pandemic established, researchers in developed nations have used it for monitoring different ailments resembling monkeypox, influenza and cholera. In a paper printed in November final yr within the journal Science Translational Medicine, researchers within the U.S. have recommended that wastewater surveillance be expanded to track dengue, malaria, Zika and typhoid.
Should India too use wastewater surveillance to track vector-borne illness just like the developed nations? “The U.S. and Europe don’t have much dengue and are unlikely to test fevers for dengue or malaria unless they know it is around (which may happen from environmental surveillance). In India, these are endemic diseases, so the questions that can be addressed by environmental surveillance need careful consideration since clinical cases are likely to be tested for known causes,” says Dr. Gagandeep Kang, former Professor at CMC Vellore.
In a paper printed within the journal Trends in Parasitology, Dr. Farah Ishtiaq from the Bengaluru-based Tata Institute for Genetics and Society, which has been utilizing wastewater surveillance to study SARS-CoV-2 burden in Bengaluru, says that using wastewater surveillance for vector-borne pathogens ought to bear in mind the geographical context, pathogen biology, and the supply of sewage networks.
There have been latest outbreaks of malaria and dengue within the U.S., and Portugal. However, the U.S. and European nations not often report malaria and dengue. The developed nations even have glorious sewage networks, which makes it simple to track these pathogens. Finally, transmission is seasonal, if in any respect.
But in India, malaria and dengue are endemic and pathogen transmission takes place virtually all year long. “Importantly, besides people shedding the pathogens through stools, there are several mammals, including nonhuman primates, that serve as reservoir hosts of malaria and dengue. So in a tropical country like India, it is difficult to say that all the malaria and dengue microbes detected in wastewater are excreted only by humans,” Dr. Ishtiaq says.
In the case of dengue, virus shedding by people is low. This makes it troublesome to detect dengue viral RNA in wastewater at ranges comparable to SARS-CoV-2 RNA. “Using wastewater surveillance to detect malaria or dengue pathogens and find the actual burden of the disease in the community in a setting like ours is a challenge,” says Dr. Ishtiaq.
“For vector-borne diseases, wastewater surveillance is not enough. Where we are trying to solve the problem through vector surveillance, mosquito surveillance should not be sidelined and wastewater surveillance be seen as a solution.” Unlike water-borne pathogens resembling rotavirus and hepatitis that are handed via human excreta, vector-borne ailments that produce other reservoir hosts will likely be a problem to study via wastewater surveillance, she provides. Though animals function hosts for malaria and dengue internationally, the range of animal hosts in tropical nations is under no circumstances comparable to temperate nations.
“There is a huge push to identify priority pathogens for wastewater surveillance, which is welcome for water-borne diseases, influenza, etc. But if asked to prioritise dengue and malaria I will think hard as I know that the signal I will get will not exclusively be from humans,” Dr. Ishtiaq stresses. One of the important thing standards for the collection of precedence pathogens of wastewater-based surveillance is that pathogens are secure within the wastewater and are constantly shed within the faecal materials or urine.
In August 2022, in addition to the SARS-CoV-2 virus, Bangladesh launched a proof-of-concept wastewater surveillance programme to track and monitor three different vaccine-preventable pathogens together with Salmonella typhi, Vibrio cholerae, and rotavirus within the communities.
“When selecting priority pathogens of wastewater surveillance, it is essential to consider the limitations and challenges that arise from different sanitation systems and host-parasite geography before drawing conclusions from wastewater surveillance data,” she writes.
