Red Tide: A Hospitalization Concern Or Not?

Red tide is a harmful algal bloom (HAB) that occurs when algae grow excessively in an area of the ocean, often discolouring the water with a reddish or reddish-brown hue. Caused by the microscopic algae Karenia brevis, red tides produce brevetoxins, which are toxic to marine life and humans. While the toxins primarily kill fish and make shellfish dangerous to eat, they can also become airborne, causing respiratory issues in humans and exacerbating existing respiratory conditions. Although red tides have been reported across all U.S. coastal states, they are particularly prevalent along Florida's Gulf Coast, where they have resulted in increased healthcare costs and adverse economic impacts.

Respiratory issues: burning eyes, noses, and throats, coughing, sneezing, and shortness of breath

Red tide is a harmful algal bloom (HAB) caused by the accumulation of aquatic microorganisms that produce toxins. These toxins can be released into the air and cause a range of respiratory issues, including burning eyes, noses, and throats, coughing, sneezing, and shortness of breath. While the occurrence of red tide is unpredictable, it typically happens in the late summer and early fall along coastal regions, turning the water reddish-brown.

The toxins released during a red tide event can have severe respiratory effects on humans, especially those with pre-existing respiratory conditions such as asthma, emphysema, or chronic obstructive pulmonary disease (COPD). People with these conditions are advised to avoid areas with red tide and take necessary precautions, such as closing windows, using air conditioning, and wearing particle filter masks.

The brevetoxins released during a red tide can become aerosolized by rough seas or breaking waves, making it easier for individuals to inhale them. Exposure to these toxins can result in a range of respiratory symptoms, including coughing, sneezing, a runny nose, and shortness of breath. In more severe cases, individuals may experience bronchoconstriction and respiratory distress.

The impact of red tide on respiratory health is not limited to direct exposure. Studies have shown that during red tide events, there is an increase in medical care facility visits for respiratory complaints, even among those who live along the coast but may not have direct contact with the water. This suggests that the toxins released during a red tide event can spread beyond the immediate coastal areas and affect a larger population.

If individuals experience any respiratory symptoms after potential exposure to red tide, it is recommended to seek medical attention and report the exposure to local health authorities to help monitor and manage the situation effectively.

Shellfish poisoning: toxins accumulate in shellfish, leading to neurotoxic shellfish poisoning (NSP)

Red tides are harmful algal blooms (HABs) that occur when algae grow excessively in a body of water, often discolouring it with a reddish or reddish-brown hue. These blooms produce toxins that can be harmful to fish, marine animals, birds, and humans. While red tides themselves can cause respiratory issues in humans, they also lead to neurotoxic shellfish poisoning (NSP) when toxins accumulate in shellfish.

Neurotoxic shellfish poisoning (NSP) is caused by the consumption of shellfish contaminated with brevetoxins, a group of powerful neurotoxins produced by the marine dinoflagellate Karenia brevis. Brevetoxins can cause a range of gastrointestinal and neurological issues in humans, including nausea, vomiting, diarrhoea, abdominal pain, and neurological symptoms such as dizziness, numbness, and slurred speech. In severe cases, NSP can lead to respiratory failure and even death.

Shellfish, such as clams, oysters, and mussels, accumulate biotoxins in their flesh due to their filter-feeding nature. When a red tide occurs, the brevetoxins produced by K. brevis can be ingested by shellfish, leading to NSP in humans who consume them. Cooking or freezing shellfish does not destroy these toxins, so it is crucial to avoid consuming shellfish from areas affected by red tides.

The occurrence of NSP is closely associated with red tides, and outbreaks commonly take place following a harmful algal bloom. The frequency of these blooms has been increasing due to human activities, climate change, and eutrophication of marine waters caused by agricultural runoff, deforestation, and river bed erosion. As a result, the risk of NSP has also increased.

Currently, there is no specific antidote for brevetoxins. Treatment for NSP focuses on supportive care, including intravenous fluids, respiratory function monitoring, and pain management. Activated charcoal can be administered within four hours of consumption to decontaminate the gastrointestinal tract. Public health policies vary across states, but measures are implemented to prevent shellfish poisoning outbreaks, such as monitoring dinoflagellate levels and restricting shellfish harvesting in affected areas.

Food poisoning: consuming contaminated seafood can cause food poisoning, including paralytic shellfish poisoning (PSP)

Red tides are harmful algal blooms (HABs) that occur when there is a high concentration of toxic algae in a particular area of the ocean, which often discolours the water red. These blooms produce toxins that can kill fish and make shellfish dangerous to eat. Consuming contaminated seafood can cause food poisoning, including paralytic shellfish poisoning (PSP).

Paralytic shellfish poisoning (PSP) is caused by eating shellfish contaminated with saxitoxins, which are produced by various types of algae, including the alexandrium species and dinoflagellates such as K. brevis. Shellfish eat these algae and can retain the toxins in their tissue. Bivalve molluscan shellfish such as clams, mussels, oysters, geoduck, and scallops are known to accumulate PSP. Other marine species, such as sea cucumbers and crustaceans like crabs and lobsters, may also be affected.

Symptoms of PSP usually appear 30 to 60 minutes after consuming contaminated shellfish and can include numbness and tingling in the face, lips, tongue, arms, and legs, as well as diarrhoea, vomiting, headaches, and nausea. In severe cases, PSP can cause paralysis of muscles and even lead to death. There is currently no antidote for PSP, and treatment for severe cases involves the use of life support systems until the toxin passes from the body.

It is important to note that cooking, freezing, or boiling shellfish does not destroy the toxins. Therefore, it is recommended to avoid consuming shellfish from areas with red tides or algal blooms. If you suspect that you have gotten sick from consuming contaminated seafood, it is advised to contact your local department of health and seek medical attention if symptoms persist or become severe.

To prevent exposure to red tide toxins, individuals can follow guidelines such as avoiding contact with affected water, thoroughly washing with clean water and soap if exposed, and avoiding shellfish from red tide areas. Additionally, wearing masks and using air conditioning with maintained filters can help reduce the impact of respiratory symptoms associated with red tides.

Marine life impact: red tide kills fish and marine animals, with toxins persisting in larger fish and mammals

Red tides, or harmful algal blooms (HABs), can have devastating impacts on marine life, killing fish and other marine animals and leaving toxins that persist in larger fish and mammals.

Harmful algal blooms are caused by the excessive growth of certain types of microscopic algae, which release powerful toxins that can be harmful to both marine life and humans. One of the most well-known species of algae that cause red tides is Karenia brevis (K. brevis), which produces brevetoxins. These toxins can accumulate in primary consumers such as zooplankton, fish, bivalves, and other filter feeders. From there, they move up the food chain, transferring to larger predators such as fish, crustaceans, and other bottom-dwelling organisms.

The toxins produced by K. brevis can affect a wide range of marine wildlife, including fish, marine mammals, seabirds, and invertebrates. Fish are particularly vulnerable to brevetoxins, which can cause violent twisting and corkscrew swimming, defecation, regurgitation, pectoral fin paralysis, and ultimately death due to gill failure. Shark species have also been affected during multi-species fish kills, although large-scale shark die-offs are rare. Invertebrates such as shrimp, sponges, sea urchins, crabs, and certain shellfish are also susceptible to red tide toxins.

Brevetoxins can also accumulate in filter-feeding organisms attached to seagrass, which are then ingested by manatees, leading to sickness and death. Mass die-offs of coastal seabirds and shorebirds are common during K. brevis blooms, as birds consume contaminated fish and crustaceans. Marine mammals, such as sea turtles, can be affected by consuming contaminated prey or by inhaling toxins.

The toxins produced by red tides can persist in the environment and accumulate in larger fish and mammals, making them sick. Cooking or freezing fish does not destroy these toxins, and contaminated fish may not look or taste different from uncontaminated ones. People who consume fish or shellfish that have been exposed to red tide toxins may experience illness, including allergic reactions, respiratory problems, and food poisoning.

Human exposure: swimming in or living near red tide areas can lead to health issues requiring medical attention

Red tides, or harmful algal blooms (HABs), can pose health risks to humans who swim in or live near affected areas. While not all algal blooms are harmful, certain species of algae can produce potent neurotoxins that can be transferred to humans through various exposure routes. Here are some ways human exposure to red tide can lead to health issues requiring medical attention:

Respiratory Issues

Beachgoers and residents exposed to red tide toxins may experience respiratory symptoms such as burning sensations in the eyes, nose, and throat. People with chronic respiratory issues, such as asthma or emphysema, are particularly vulnerable and should avoid red tide areas. Local health authorities advise closing windows, using air conditioning with well-maintained filters, and wearing particle filter masks to reduce exposure to airborne toxins.

Skin Irritation

Swimming in or coming into contact with red tide water can cause skin irritation, rashes, and a burning sensation. It is recommended to avoid swimming or wading in water with a red tide and to thoroughly wash the skin and clothing with soap and fresh water if exposed.

Seafood Consumption

Consuming seafood contaminated by red tide toxins can lead to serious neurological symptoms. Paralytic shellfish poisoning (PSP) is a potentially life-threatening syndrome that can develop within hours of consuming contaminated shellfish. It is important to follow local guidelines and avoid consuming shellfish from areas affected by red tide. Proper cleaning and cooking of locally caught fish can reduce the risk of contamination.

Environmental Impact

Red tides can have a detrimental impact on marine life, killing fish and affecting mammals, birds, and turtles. The toxins produced by certain algae species can also make the surrounding air difficult to breathe, affecting both humans and wildlife. The decay of large amounts of dead algae can deplete oxygen levels in the water, further endangering aquatic life.

It is important to follow local health alerts, warnings, and guidance to minimize the potential health risks associated with red tide exposure. If symptoms persist or become severe, individuals should seek medical attention from their primary care provider or specialized clinics equipped to handle red tide-related health issues.

Frequently asked questions