Animals aren’t picky about which water to drink, even when it’s tinted green or red.

Water with those colors or green mats on the surface may contain harmful algal blooms, proliferations of microbes that produce substances toxic to animals. Pets, for example, may ingest those organisms not only by having a drink but also by grooming themselves after a swim.

Dr. Sherri Lyn Kasper, who is a private practitioner in Tallahassee, Florida, and chair of the AVMA Committee on Environmental Issues, taught veterinarians at the AVMA Virtual Convention 2021 how to identify the various signs of intoxication related to blooms, what treatments might be needed, and how to educate clients on identifying potential danger. She delivered a lecture, “The Effects of Harmful Algal Blooms on Our Patients,” July 29.

In recent years, federal health authorities have been gathering information on the harm caused by algal blooms and educating the public about those risks. In December 2020, officials from the Centers for Disease Control and Prevention reported HABs had sickened at least 389 people and 413 animals during three years of surveillance, 2016-18. Those figures were among the first data published through the CDC’s One Health Harmful Algal Bloom System. Of the 92 animal cases with reported signs, slightly more than half of signs were gastrointestinal.

Wildlife—especially wild birds—accounted for most illnesses in animals. But the figures also included at least 50 dogs and 36 cattle.

In her session, Dr. Kasper noted the differences in clinical signs among HAB exposures. Hepatotoxins cause liver damage, depression, vomiting, and jaundice. Neurotoxins cause signs ranging from ataxia to respiratory system paralysis. And dermatoxins cause irritation to skin and airways.

“Asking the client whether or not that animal has been near a water source or, if you happen to be going out to a farm, looking at the herd and looking at the water source the herd is drinking from is going to be very helpful,” she said.

Physical examinations will be broad, and clinical signs will be dose dependent, she said. If an animal has recent exposure to a waterway and signs related to HAB exposure, a veterinarian may consider asking a client to collect a water sample for testing.

Dr. Kasper also said veterinarians may want to research how to submit water samples and patient specimens now so they are prepared for any potential HAB exposures. She noted that state governments often provide information on confirmed or suspected HABs, and some accept reports of related illnesses.

Detoxification can include steps such as bathing animals to remove leftover toxins from their coats and inducing vomiting.

Treatments can range widely by the types of substances, and they may include administration of activated charcoal, intravenous fluids, anti-seizure medications, antimicrobials, anti-emetic drugs, vitamin K, or plasma. Some patients may need respiratory support, and some may need a month of antioxidant administration to protect their liver.

“With the right type of supportive care, many of these patients can survive,” Dr. Kasper said.