Infectious agents from terrestrial animals, including domestic cats, livestock and even humans are spreading to the oceans and threatening our sea life. A new term has been coined to describe the land-based bacteria, fungi and parasites that travel into our seas: pollutagens (polluting pathogens). A feature in this month’s Scientific American details numerous cases of these pollutagens and suggests that they may be on the rise.
A key example is the Toxoplasa gondii parasite that travels from domestic cats, via their faeces, into natural irrigation and waste disposal systems and on to marine animals such as sea otters and dolphins.
The hardy nature of the parasite, combined with the huge numbers of domestic cats (around 70 million domestic and 60 million feral felines in the U.S. alone), gives some idea of the potential scale of the problem.
The mere appearance of such pollutagens is not the only issue of concern, however.Scientists have also found that many of the bacteria found in these marine organisms are resistant to medications, which could have implications for the treatment of infections in both the marine organisms and other animals (including humans) that are exposed to them. Further, viruses may be mutating and combining with other viruses to form strains with increased virulence and transmissibility. The feature suggests some key actions that could be taken to manage the problem of pollutagens, including preserving wetlands that act as a buffer zone between sources of pollutagens, such as farms and towns, keeping pets indoors, and disposing of human and animal sewage more responsibly.