Lepto-causing bacteria found in Estero de Paco

MANILA, Philippines —  Scientists from the University of the Philippines have found leptospirosis-causing bacteria throughout the entire Estero de Paco – a waterway that passes through densely populated and flood-prone communities in Metro Manila. The waterway is located near President Quirino Avenue and Pres. Osmeña Highway (South Superhighway), with the Paco Market – one of Manila’s largest and oldest public markets – sitting along its banks. It is a major tributary to the Pasig River.

Scientists Ram Julius Marababol and Windell Rivera of the University of the Philippines-Diliman College of Science (UPD-CS) said they detected Leptospira at all five sites where soil and water samples were collected.

“Most people picture leptospirosis risk as something you catch from an obvious flood puddle after a typhoon. What our data show is that the bacteria carrying the potential to make people sick aren’t waiting for a flood to arrive; they are already living in the soil and water of an ordinary city waterway, spread evenly across it, all year round,” Marababol, who led two UPD-CS studies, said.

Their findings suggest no statistically significant difference in the presence of Leptospira between upstream and downstream areas or between soil and water samples, which suggests that the bacterium is not just concentrated in one part of the waterway.

“The bacteria were detected throughout the waterway, showing that contamination can extend across different parts of an urban waterway rather than being limited to a single visible source,” Marababol said.

Marababol and Rivera collected soil and water samples from five sites along the Paco creek and tested 448 bacterial isolates.

Within the bacteria collected from the waterway, the researchers said two strains of Leptospira carrying the lipL32 gene, a genetic marker commonly associated with pathogenic Leptospira, were identified.

Marababol said genetic sequencing identified the strains as Leptospira yasudae, a species known to infect humans and animals.

He noted that this is the first time L. yasudae has been genetically sequenced from a sample collected in the Philippines.

“The researchers compared the Philippine strains with the only two other L. yasudae genomes currently available, which came from Mayotte and Brazil. Their analysis showed that the Philippine strains were genetically distinct from the previously sequenced strains, suggesting that L. yasudae in the Philippines may represent a previously undocumented local lineage,” Marababol said.

The researchers reported the first complete draft genome of L. yasudae recovered from Philippine soil in a companion paper published in “Microbiology Resource Announcements.”

“The absence of isolated hotspots is itself the alarming part. It means the old model of pointing to one contaminated spot and cleaning it up isn’t going to be enough,” Rivera said.

“If an entire waterway is functioning as a single, connected reservoir, then surveillance and intervention have to be rethought at the scale of the whole system, not a handful of sampling points,” he added.

The researchers classified leptospirosis as a neglected tropical disease, but public health literature cited in the researchers’ own papers describes an epidemiology that has been “undergoing a marked shift.”

“The incidence (of leptospirosis) is now climbing specifically in dense, rapidly urbanizing and inadequately drained cities like Metro Manila, where informal settlements, weak waste management and recurring flooding create ideal conditions for the bacteria to move from animal reservoirs into human contact,” Marababol said.

The researchers noted that their findings did not determine the number of people infected by these specific strains nor does it establish that the bacteria are responsible for any recent increase in reported leptospirosis cases.

Marababol said that the findings highlight the need to consider the “widespread presence of Leptospira in urban waterways when planning flood-season disease surveillance and communicating leptospirosis risks to the public.”

Both studies were supported by the Department of Science and Technology and conducted at the Pathogen-Host-Environment Interactions Research Laboratory of the UPD-CS Institute of Biology in partnership with the Philippine Genome Center.