Raccoon cages and tall indoor plants may not do a lot to reduce the spread of disease-causing fleas and ticks in the United States, a new study suggests.
The researchers at Harvard University analyzed data from the Centers for Disease Control and Prevention (CDC) and state animal control agencies from 2002 to 2016 and found that indoor rabbit cages and outdoor rabbit cages did not increase the risk of a disease-carrying flea or tick by a statistically significant amount.
“Our results are consistent with the hypothesis that rodents and birds are not the primary carriers of disease and that, for instance, rodents and other domestic animals may not transmit disease to humans,” lead author David Reichardt, a professor of microbiology at Harvard Medical School, said in a statement.
“But, this may be due to the fact that many indoor environments have low air-borne concentrations of disease agents, and we would not expect to see a significant increase in the spread rate of infectious disease among domestic animals.”
In fact, researchers found that the incidence of disease transmission between humans and rodents and between rodents and humans increased by 1.5 percent and 2.5% in areas where there was a greater than 50 percent increase in outdoor rodent cages.
“In contrast, the incidence among humans increased more modestly in areas with more than 50% increases in outdoor cages,” the study said.
The study did not investigate whether outdoor rabbit cage levels affected transmission between animals.
The authors of the study noted that more research is needed to examine the effectiveness of rodent cage designs, such as those in urban settings.
The CDC did not immediately respond to a request for comment.
Reichardt is the author of a related study, published in the Proceedings of the National Academy of Sciences, which found that in cities, the number of rats in outdoor cage spaces was similar to that in indoor cage spaces.
However, rats did not spread diseases to humans.
A 2016 study found that rats and mice can transmit disease through indoor plumbing and rodent droppings in the U.S., but rats and dogs were not as contagious as they were in urban environments.
Reid said the study is the first to find that indoor rodent cages do not increase spread of infectious diseases, which he called “inconsistent with previous studies.”
He noted that he thinks the finding of a reduction in transmission could be due not to any changes in indoor rodent cage design, but to the changes in the way rodents interact with other species.
Reach Adam Brown at [email protected] or via Twitter at @AdamBrownAP.