Far from good luck: Bird poop poses serious health risk, contains antibiotic-resistant genes

HOUSTON – Whether it falls on your car or on your head, bird poop can be inconvenient to say the least. Now, researchers at Rice University suggest that bird droppings may be more than just a nuisance, they could also be a serious health risk. Their study reveals that feces from urban ducks, crows, and gulls has high levels of genes related to antibiotic resistance.

The study in the journal Environmental Pollution examines the prevalence, diversity, and persistence of antibiotic-resistant genes (ARGs) in wild urban birds. Researchers compare “freshly deposited” droppings from wild urban birds in Houston to samples from poultry and livestock, which they believe carry some of the same ARGs.

The findings reveal ARGs are both common and persistent in the environment. Moreover, most bird ARGs have significant resistance to antibiotics including tetracycline, beta-lactam, and sulfonamide. The levels of antibiotic resistance are similar to those of poultry, which are sometimes fed with antibiotics.

Where can contamination occur?

The presence of antibiotic-resistant genes in bird feces is concerning because previous studies warn ARGs and antibiotic resistant bacteria (ARBs) can spread from birds to humans. This can occur through swimming in feces-contaminated water, contact with feces and feces-contaminated soil, or inhaling fecal particles in the air.

In fact, the team found ARGs are “moderately persistent” in soil up to an inch deep, with half-lives of up to 11 days.

“Our results indicate that urban wild birds are an overlooked but potentially important reservoir of antimicrobial resistance genes, although their significance as vectors for direct transmission of resistant infections is possible but improbable due to low frequency of human contact,” researcher Pedro Alvarez says in a university statement.

What makes bird poop so dangerous?

The study authors note that birds have high levels of intI1. This is an integron (a genetic element that can capture and carry genes) which helps bacteria rapidly gain antibiotic resistance. In birds, levels of intl1 are five times higher than in farm animals.

The content of bird feces also seems to vary by season. Compared to summer droppings, winter droppings have more types of bad bacteria that may harbor ARGs. This may be due to less sunlight or different moisture levels and temperatures in different seasons.  The authors say that winter samples contain bacteria that cause urinary tract infections, sepsis, and respiratory infections among all birds in the study.

Moreover, crows have lower levels of ARGs in the summer compared to ducks and gulls.

“Our study raises awareness to avoid direct contact with bird droppings in urban public areas, especially for vulnerable or sensitive populations,” lead researcher Pingfeng Yu explains. “Meanwhile, regular cleaning should also help to mitigate associated health risks.”

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