Science
Presence of parasite that’s deadly for dogs now confirmed in California: Signs to watch for
For five years, an elusive tormentor of animals hid from authorities in east Riverside County as 10 dogs were injured and another killed.
The victims hailed from Los Angeles, Riverside and Orange counties, while the suspect maintained a strong alibi: It had never visited California.
It took authorities years to discover the one key detail linking the abuser with those abused: time spent at the Colorado River at or near the California-Arizona border town of Blythe.
That’s where professor Adler R. Dillman, chair of UC Riverside’s Department of Nematology (study of roundworms) and an expert on parasitology, and a team of researchers and students recently unmasked their culprit.
A parasite called Heterobilharzia americana, a flatworm commonly referred to as liver fluke, was behind the illness of the 11 dogs.
The parasite normally makes its home in Texas and in the South. Its discovery in California, in the Colorado River, marked its first recorded appearance in the area.
Dillman said he was part of a team that made four trips to the Colorado River between March and August of 2023 to collect more than 2,000 snails of two distinct species known to transmit the worms. They used DNA to identify both snails, Galba cubensis and Galba humilis, and the flatworm.
That squad included UC Riverside postdoctoral researcher Anil B. Baniya and graduate students Connor Goldy and Perla Achi. The trio, Dillman and others published their findings Wednesday in the scientific journal Pathogens.
“I was super excited to finally provide an answer as to what was happening with those dogs,” Dillman said in a phone interview on Wednesday evening. “We suspected it was this parasite, but once we finally confirmed it, I was jumping up and down with excitement.”
Dillman and various public health agencies dedicated to humans or animals have been trying to raise awareness of the parasite and its harm to dogs.
The parasite can cause canine schistosomiasis, an illness that affects the liver and intestines of dogs, according to Dillman.
Los Angeles County Department of Public Heath veterinarian Emily Beeler said symptoms include:
- loss of appetite
- vomiting
- diarrhea
- profound weight loss
- signs of liver disease, which can include the above symptoms and, among others, increased thirst, the need to pee and yellowish eyes
“If your dog has these symptoms after swimming in the Colorado River,” Beeler said, “it’s a good precaution to ask your veterinarian for a simple fecal test.”
The health department notes that the disease in dogs has a very gradual, “insidious onset.”
The department issued one of its first warnings in March 2019 after two South Bay dogs tested positive for the parasite after returning from a trip to the Colorado River in 2018.
Eventually, the number grew to 11 dogs from five households across three counties infected between 2018 and 2023 with canine schistosomiasis, with seven from Orange County.
Some of the dogs had shown signs of illness, others were tested as a precaution after their owners realized they also had taken their pets to the river. In total, nine were tested through fecal exams, while two underwent liver biopsies, according to the L.A. County Department of Health.
Although six dogs were asymptomatic, five were stricken by vomiting, diarrhea and weight loss, according to the department.
One of those five dogs died, while the other four recovered thanks to treatment that included antiparasitic drugs.
It was discovered through interviews that all of the infected dogs had visited the Colorado River near Blythe.
In January 2023, Dillman said Beeler called and asked him to test those waters for the parasite.
Dog owners told him they had visited two primary places, Quechan Park and Hidden Beaches Resort.
Dillman and his team’s first discovery was that the two species of snails that carry the parasite had migrated to California.
How they arrived remains a mystery.
“We don’t know how these snails reached California,” Dillman said. “It’s a bit complex.”
The professor noted that there was an outbreak of canine schistosomiasis in Moab, Utah, in 2018. Ultimately, 12 dogs living near a man-made pond with those snails present tested positive. Dillman said the location of that pond was only a couple of miles from the Colorado River.
“Researchers didn’t check to see if the snails were in the river,” he said. “It’s possible they’re there.”
Along with dogs, the parasite has been known to infect raccoons and horses.
The disease cannot be transmitted between dogs and humans, though people may develop a self-limiting rash (meaning it goes away on its own without treatment) after swimming or contacting contaminated waters, according to Sara Strongin, chief veterinarian at the Riverside County Department of Animal Services.
The snail excretes a juvenile form of the worm, which then has 24 hours to find a mammal host to infect or die, according to Dillman.
The goal of the worm is to reach the intestines of a host, where it continues to develop into an adult. There it mates and releases thousands of eggs, Dillman said. Those eggs clog the lungs, spleen, liver and hearts of hosts along with immune cells called granulomas that fight them.
Eventually, organ tissue stops functioning, Dillman said.
If found in time, however, antiparasitics like praziquantel and fenbendazole can help fight off an infection.
“The goal here,” Dillman said, “is to get awareness out and make sure dog owners know what signs to look for.”
Science
What’s in a Name? For These Snails, Legal Protection
The sun had barely risen over the Pacific Ocean when a small motorboat carrying a team of Indigenous artisans and Mexican biologists dropped anchor in a rocky cove near Bahías de Huatulco.
Mauro Habacuc Avendaño Luis, one of the craftsmen, was the first to wade to shore. With an agility belying his age, he struck out over the boulders exposed by low tide. Crouching on a slippery ledge pounded by surf, he reached inside a crevice between two rocks. There, lodged among the urchins, was a snail with a knobby gray shell the size of a walnut. The sight might not dazzle tourists who travel here to see humpback whales, but for Mr. Avendaño, 85, these drab little mollusks represent a way of life.
Marine snails in the genus Plicopurpura are sacred to the Mixtec people of Pinotepa de Don Luis, a small town in southwestern Oaxaca. Men like Mr. Avendaño have been sustainably “milking” them for radiant purple dye for at least 1,500 years. The color suffuses Mixtec textiles and spiritual beliefs. Called tixinda, it symbolizes fertility and death, as well as mythic ties between lunar cycles, women and the sea.
The future of these traditions — and the fate of the snails — are uncertain. The mollusks are subject to intense poaching pressure despite federal protections intended to protect them. Fishermen break them (and the other mollusks they eat) open and sell the meat to local restaurants. Tourists who comb the beaches pluck snails off the rocks and toss them aside.
A severe earthquake in 2020 thrust formerly submerged parts of their habitat above sea level, fatally tossing other mollusks in the snail’s food web to the air, and making once inaccessible places more available to poachers.
Decades ago, dense clusters of snails the size of doorknobs were easy to find, according to Mr. Avendaño. “Full of snails,” he said, sweeping a calloused, violet-stained hand across the coves. Now, most of the snails he finds are small, just over an inch, and yield only a few milliliters of dye.
Science
Video: This Parrot Has No Beak, But Is at the Top of the Pecking Order
new video loaded: This Parrot Has No Beak, But Is at the Top of the Pecking Order
By Meg Felling and Carl Zimmer
April 20, 2026
Science
Contributor: Focus on the real causes of the shortage in hormone treatments
For months now, menopausal women across the U.S. have been unable to fill prescriptions for the estradiol patch, a long-established and safe hormone treatment. The news media has whipped up a frenzy over this scarcity, warning of a long-lasting nationwide shortage. The problem is real — but the explanations in the media coverage miss the mark. Real solutions depend on an accurate understanding of the causes.
Reporters, pharmaceutical companies and even some doctors have blamed women for causing the shortage, saying they were inspired by a “menopause moment” that has driven unprecedented demand. Such framing does a dangerous disservice to essential health advocacy.
In this narrative, there has been unprecedented demand, and it is explained in part by the Food and Drug Administration’s recent removal of the “black-box warning” from estradiol patches’ packaging. That inaccurate (and, quite frankly, terrifying) label had been required since a 2002 announcement overstated the link between certain menopause hormone treatments and breast cancer. Right-sizing and rewording the warning was long overdue. But the trouble with this narrative is that even after the black-box warning was removed, there has not been unprecedented demand.
Around 40% of menopausal women were prescribed hormone treatments in some form before the 2002 announcement. Use plummeted in its aftermath, dipping to less than 5% in 2020 and just 1.8% in 2024. According to the most recent data, the number has now settled back at the 5% mark. Unprecedented? Hardly. Modest at best.
Nor is estradiol a new or complex drug; the patch formulation has existed for decades, and generic versions are widely manufactured. There is no exotic ingredient, no rare supply chain dependency, no fluke that explains why women are suddenly being told their pharmacy is out of stock month after month.
The story is far more an indictment of the broken insurance industry: market concentration, perverse incentives and the consequences of allowing insurance companies to own the pharmacy benefit managers that effectively control drug access for the majority of users. Three companies — CVS Caremark, Express Scripts and OptumRx — manage 79% of all prescription drug claims in the United States. Those companies are wholly owned subsidiaries of three insurance behemoths: CVS Health, Cigna and UnitedHealth Group, respectively. This means that the same corporation that sells you your insurance plan also decides which drugs get covered, at what price, and whether your pharmacy can stock them. This is called vertical integration. In another era, we might have called it a cartel. The resulting problems are not unique to hormone treatments; they have affected widely used medications including blood thinners, inhalers and antibiotics. When a low-cost generic such as estradiol — a medication with no blockbuster profit margins and no patent protection — runs into friction in this system, the friction is not random. It is structural. Every decision in that chain is filtered through the same corporate profit motive. And when the drug in question is an off-patent estradiol patch that has negligible profit margins because of generic competition but requires logistical investment to keep consistently in stock? The math on “how much does this company care about ensuring access” is not complicated.
Unfortunately, there is little financial incentive to ensure smooth, consistent access. There is, however, significant financial incentive to steer patients toward branded alternatives, or simply to let supply tighten — because the companies aren’t losing much profit if sales of that product dwindle. This is not a conspiracy theory: The Federal Trade Commission noted this dynamic in a report that documented how pharmacy benefit managers’ practices inflate costs, reduce competition and harm patient access, particularly for independent pharmacies and for generic drugs.
Any claim that the estradiol patch shortage is meaningfully caused by more women now demanding hormone treatments is a distraction. It is also misogyny, pure and simple, to imply that the solution to the shortage is for women’s health advocates to dial it down and for women to temper their expectations. The scarcity of estradiol patches is the outcome of a broken system refusing to provide adequate supply.
Meanwhile, there are a few strategies to cope.
- Ask your prescriber about alternatives. Estradiol is available in multiple formulations, including gel, spray, cream, oral tablet, vaginal ring and weekly transdermal patch, which is a different product from the twice-weekly patch and may be more consistently available depending on manufacturer and region.
- Consider an online pharmacy. Many are doing a good job locating and filling these prescriptions from outside the pharmacy benefit manager system.
- Call ahead. Patch shortages are inconsistent across regions and distributors. A call to pharmacies in your area, or a broader geographic radius if you’re able, can locate stock that your regular pharmacy doesn’t have.
- Consider a compounding pharmacy. These sources can sometimes meet needs when commercially manufactured products are inaccessible. The hormones used are the same FDA-regulated bulk ingredients.
Beyond those Band-Aid solutions, more Americans need to fight for systemic change. The FTC report exists because Congress asked for it and committed to legislation that will address at least some of the problems. The FDA took action to change the labeling on estrogen in the face of citizen and medical experts’ pressure; it should do more now to demand transparency from patch manufacturers.
Most importantly, it is on all of us to call out the cracks in the current system. Instead of repeating “there’s a patch shortage” or a “surge in demand,” say that a shockingly small minority of menopausal women still even get hormonal treatments prescribed at all, and three drug companies control the vast majority of claims in this country. Those are the real problems that need real solutions.
Jennifer Weiss-Wolf, the executive director of the Birnbaum Women’s Leadership Center at New York University School of Law, is the author of the forthcoming book “When in Menopause: A User’s Manual & Citizen’s Guide.” Suzanne Gilberg, an obstetrician and gynecologist in Los Angeles, is the author of “Menopause Bootcamp.”
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