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The Biochemistry of the Elephant in the Room: The Red Tide

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I sit behind my desk tapping my pen to a mesmerizing rhythm thinking how much of this year’s symptoms of sinusitis, AOM, cough, and bronchitis are actually due to the common threats from bacteria and viruses versus the new elephant in the room, the red tide - large concentrations of aquatic microorganisms in water. This year I have noted that despite OTC and prescription treatments my patients are not improving. What is different this year? The red tide.

Having worked most of my career in California and being more familiar with the desert bacteria than the red tide; I believe the conditions in Florida regarding these brevatoxins are producing health effects not only on marine life but also on human beings. Diving into the reports I realized that anyone living 1–2 miles from the beach will be affected due to the winds. Wearing a mask does help to avoid the brevotoxins, however. The news portrayed dead corpses of manatees, fish, and seabirds, but there has not been much mention of the respiratory and gastrointestinal manifestations of the toxins in humans.

The respiratory inhalants are neurotoxins released by the blooms of the dinoflagellate called K. brevis. The Florida red tide blooms have been documented since the 1800 and have spread as far as to the coast of Mexico and Texas. There is a controversy that urbanization around the water sources in Florida are causing nutrients to be funneled more frequently into the gulf streams. This is a topic of political nature and will be best approached by another author. I would like to focus on how important it is for clinicians to ask about possible red tide exposure during our HPI and ROS.

The toxins from the K. brevis are lipid soluble, cyclic polyethers and they act to open those famous sodium gated ion channels in the cell membrane leading to influx into the cell. There are over 10 types of brevotoxins and more analogs of the toxin after the ingestion from the shellfish. In Florida, the major brevotoxin is the PbTx-2. It's interesting that K brevis produces its own antagonist! Brevenal thus acts on different receptor cells of the nerves and is more common during the senescence phase of the bloom.

The brevotoxins remind me of carbon monoxide; tasteless, odorless, and heat stable. Thus, dangerous to humans. However, many describe the burning sensation to the respiratory tract and eyes when at the beaches. The only way to truly detect the exposure is with a brevatoxin ELISA test. Only 10–20 percent of the brevatoxin molecules are small enough to enter the lower respiratory tract.

Research is claiming that the immunotoxic effect on humans produces apoptosis, the release of inflammatory mediators, decreased lymphocyte production, oxidative stress and interruption of the cell cycle. This reminds me of the mitochondrial poison alcohol. Sound familiar?

Furthermore, the allergic type reactions that we observe in the clinics is from the release of histamine, mast cell degranulation and the production of the pro-inflammatory cytokine IL-6. Remember that IL-6 stimulates antibody production and T cell release.

Should we monitor medications in our patients exposed to red tide? If brevatoxins effects on the glutathione depletion occurs then the monocytes are effected by the PbTx-2 and the excretion of the toxins occur through the P450 pathway. Strikingly, the same pathway as drinking a few cocktails. The end result: DNA damage.

Gastrointestinal manifestations occur when ingesting contaminated seafood and mimic a viral or bacterial gastroenteritis. When exposed to aerosolized toxins asthmatics will produce symptoms within one hour. Dr. Barabara Kirkpatrick's study found that symptoms after exposure in asthmatics persisted for 3-4 days. Another study in Florida showed that after 8 hours lifeguards at the beach evidenced symptoms of feeling overall unwell. Other studies on ER admissions also evidenced higher rates of bronchitis and asthma exacerbations during red tide blooms.

As clinicians if we treat out patients with antihistamines, steroids, and rest usually they will improve. The most difficult part of the correct diagnosis is that unless we do an ELISA test the red tide will only ever be a differential diagnosis. But let us be vigilant and remember to ask about beach time and dietary intake in our ill patients off the coast of Florida.

Connie Lapadat, NP, is a family nurse practitioner in El Cajon, CA. She is a 2018–19 Doximity Author.

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