The researchers have investigated the presence of drug residues and infectious agents in wild rats from economically disadvantaged neighborhoods in Salvador, Brazil. The focus has been on infections that the rats can spread to humans.
In the study, the researchers looked for six different infectious agents and residues from 97 different pharmaceutical substances.
The brains of the 152 rats tested contained residues of drugs, including antibiotics, antidepressants and antipsychotics, among others.
Roundworm infection
The most common drug was the antidepressant citalopram. According to the study, rats with this substance in their bodies were three times more likely to carry so-called Capillaria parasites, a type of roundworm that can infect humans.
Antibiotics also stood out in the study. In that case, however, they were shown to reduce certain infections in the rats. This may sound like something positive, but it is not, emphasizes Hussein Khalil, a researcher at SLU who led the study.
The rats have fewer bacteria, sure, but what happens is that antibiotics are constantly being pumped into these environments. This leads bacteria to adapt to the antibiotics, producing so-called antimicrobial resistance.
The risk is then that an environment with antibiotic-resistant bacteria will develop, which in the worst-case scenario could also lead to humans being infected by resistant strains.
Affected the rats' behavior
Every year, thousands of people in Brazil are exposed to zoonotic diseases. Many of these infections are treated with antibiotics. According to Khalil, the biggest risk to humans is that these diseases become incurable.
The researchers have also seen that drug residues seem to change the behavior of rats. When rats are exposed to drug residues, they become more curious and fearless. They can even become aggressive, says Khalil.
Through their curiosity, we suspect they interact more with other rats, making them more likely to carry diseases and then transmit them to humans.
