UCR researchers gathering samples from the Colorado River in Blythe. Credit: Adler Dillman/UCR
Two new studies released this week show the importance of protecting man’s best friend. In the first, researchers detail a dog-killing flatworm in Southern California, warning owners to stary away from the Colorado River. The second study reveals how spending quality time with dogs reduces stress and increases the power of brain waves associated with relaxation and concentration.
Dangerous parasite
UC Riverside (UCR) scientists confirm, for the first time, that a potentially fatal dog parasite is present in a portion of the Colorado River that runs through California. Previously found almost exclusively in Texas and other Gulf Coast states, the parasite—Heterobilharzia americana—has never been reported as far west as the Golden State.
Heterobilharzia americana is a flatworm, commonly referred to as liver fluke, that can cause canine schistosomiasis, an illness that impacts the liver and intestines of dogs. Symptoms start gradually—months after infection—with a loss of appetite, and eventually vomiting, diarrhea, profound weight loss, and signs of liver disease. Typical treatment involves use of multiple medications and close monitoring.
After learning about infection cases in local dogs, UCR nematology professor Adler Dillman assembled a research team and headed to Blythe, a border town east of Joshua Tree National Park in Riverside County, California, where the sick dogs had all spent time swimming in the river.
The infection is actually driven by the presence of a snail that transmits the worm. So, the team collected more than 2,000 snails from the banks of the river. DNA sequencing identified two different species of snails that were both actively shedding the worm parasite.
After transforming itself inside one of the snails, the worm ventures out with the goal of finding a mammal to infect. In this stage it can only survive on its own for about 24 hours. If a dog or a raccoon is in the water or drinking the water, it will most likely become infected.
“It gets into the veins of the intestinal lining, and that’s where it develops into an adult and mates,” said Dillman. “The presence of the adults in the veins isn’t the problem. It’s the eggs that get into the lungs, spleen, liver, and heart. The immune system tries to deal with it, and hard clusters of immune cells called granulomas form. Eventually, the organ tissues stop functioning.”
Once infected, it can be several months before the worst symptoms of the illness appear. Since 2019 in California, 11 dogs in three counties have been confirmed with this disease, and one has died.
H. americana is not known to be capable of causing disease in humans, nor can it contaminate drinking water.
“It can cause swimmer’s itch, a red rash where it penetrates human skin. But it’s not able to cause infection,” Dillman said. “But dogs do die from this infection, so we are hoping to raise public awareness that it’s there.”
Less stress
It turns out, protecting dogs from this parasite (in addition to other preventable illnesses) is also in the best interest of humans as a new study has shown spending quality time with dogs reduces human stress.
Researchers from Konkuk University in South Korea recently recruited 30 adult participants to perform eight different activities with a well-trained dog, such as playing with a handheld toy, giving her treats, and taking pictures with her. Participants wore electroencephalography (EEG) electrodes to record electrical activity from the brain while they interacted with the dog, and they recorded their subjective emotional state immediately following each activity.
According to the study results, published in PLOS ONE, the relative strength of alpha-band oscillations in the brain increased while participants played with and walked the dog, reflecting a state of relaxed wakefulness. When grooming, gently massaging, or playing with the dog, relative beta-band oscillation strength increased, a boost typically linked to heightened concentration. Participants also reported feeling significantly less fatigued, depressed and stressed after all dog-related activities.
Today, animal-assisted interventions like canine therapy are widely used in hospitals, schools, advocacy centers and more to help reduce anxiety, relieve stress and foster feelings of trust. The study authors say their results can build upon this, with the newly identified relationship between specific activities and physiological effects serving as a reference for programming targeted animal-assisted interventions in the future.