For pediatrician Reshem Agarwal, a dead dog in the middle of the road symbolized the plight of the “colonias,” or shantytowns along the United States-Mexican border where poverty is widespread and public services are scarce.

“It had been dead for a while,” said Agarwal, who practices in Oakland. “There were flies around and it was rigid. There were kids playing nearby.”

Agarwal was co-lead researcher on a study of the colonias slated for presentation in Chicago on Sunday at the national conference of the American Academy of Pediatrics.

Composed of shacks constructed from salvaged items, mobile homes, and other dwellings, colonias have been around since the 1950s to accommodate low-income Mexican workers, according to the US Department of Housing and Urban Development.

Often crowded on illegally subdivided land and lacking running water, plumbing, electricity, paved roads, street lights, trash collection, and other comforts, more than 2,400 exist today along the border. Many homeowners in the colonias purchased or inherited their properties but often lack proof of ownership.

In Texas, where most colonias are located, around 300,000 people live in them. More than a third are children born in the US, according to Proyecto Azteca, a Texas community group that helped Agarwal and her colleagues conduct the research and published a report based on their findings earlier this year. Community for Children, a Texas group that promotes pediatricians working in impoverished communities, also helped finalize the study.