Local Stream Parasites: The Good, The Bad, The Dog Warning

Most people think of parasites and get goosebumps. Parasites have a negative stigma, and people associate them with diseases like malaria or illness caused by having tapeworms in the digestive system. While some parasites do indeed cause disease and can wreak havoc on human health, there is a huge variety of beneficial parasites in our world too.  

According to a study led by the Smithsonian Institute in Washington D.C., it is estimated that only 10-15% of parasitic species globally are known to science. From the small fraction of parasites we have identified, we know that they play vital roles in food webs and some may even protect humans or other host species from disease.  

“You’re just not going to find a group of creatures that have more amazing adaptations and behaviors than parasites,” says Farallon Broughton, a PhD student at Oregon State University.  

Benton County Parasites 

Farallon is studying a type of parasite called Nanophyetus salmincola, which is a trematode – one of the major groups of helminth, or worm-shaped, parasites – common in freshwater environments of the Pacific Northwest. Currently, Farallon is studying Nanophyetus collected from Oak, Dixon, and Rock Creek, all located within Benton County.  

This parasite is both understudied and important, as it carries the bacterium that causes salmon poisoning disease (SPD). Not to alarm all fish lovers in the Pacific Northwest – SPD does not actively harm fish. Rather, SPD is potentially harmful and even deadly to dogs that ingest raw fish after an infected fish has died. So, while all the fisherpeople of the Northwest will be safe from the parasite as long as they cook any fish they have caught, SPD may be alarming to pet owners who frequently walk their dogs along streams or rivers.  

“You can reduce the risk to your dog by not feeding it any scraps of recently caught and cleaned fish unless they’re thoroughly cooked,” Farallon says. “I’d also recommend keeping your dog leashed or being vigilant if they’re playing around water, since they can be sneaky and get into a dead fish really quickly if they’re out of your sight.” 

Currently, Farallon’s research focuses on an intermediate host of the Nanophyetus parasite – the native Juga snail. Nanophyetus has a complex life cycle, involving two aquatic hosts – a freshwater snail followed by a salmonid (trout or salmon), other fish, or salamanders – then a final mammalian host before restarting its life cycle. The goal of the project is to learn as much as possible about the parasite to better understand its role in the ecosystem and how to safeguard pets.  

Parasites might gross you out, but they’re amazing animals and they’re an important part of ecosystems,” Farallon says, citing not only their importance to aquatic and terrestrial environments, but also the fact that pollution and climate change are leading to extinction of parasitic species before they are fully understood.  

If you are interested in Farallon’s research, the Arismendi Freshwater Ecology & Conservation Lab will be assembling a public outreach campaign with information on the parasite for the Corvallis community in the future.  

By: Lauren Zatkos