About this course:
The purpose of this activity is to enhance the learner’s knowledge of aquatic toxins in fresh and saltwater and the risks for human illness.
At the completion of this activity, the learner should be able to:
- Discuss aquatic toxins found in salt and fresh water.
- Consider Vibrio vulnificus exposure, medical management, and outcomes.
- Discuss Naegleria fowleri exposure, medical management, and outcomes.
- Explore the effects of harmful algae blooms and brevotoxins on humans.
- Define safe recreation in salt and fresh water and how to protect from infection with aquatic toxins.
Recently, there has been increased awareness of individuals impacted by exposure to toxins in the ocean and fresh water. From the elderly man who died from "flesh-eating bacteria" to the child who died from a "brain-eating amoeba," there is no shortage of fear of entering the water for recreation. Considering the majority of Florida is surrounded by water, much of the available data on this topic relates to this state. However, these concerns translate anywhere that residents and tourists seek recreation in bodies of fresh or salt water. The economic impact related to aquatic toxins and harmful algae blooms can exceed 34 million dollars per year from lost productivity in the fishing industry. Healthcare costs can skyrocket into the millions of dollars, with Sarasota County in Florida reporting 4 million dollars in hospital emergency costs resulting from the algae blooms off their coast. The recreation and tourism industries report as much as 47 million dollars lost to tourism over the last two years due to the effects of the algae blooms (Centers for Disease Control and Prevention [CDC], 2019a).
This module will explore the primary dangers in fresh and salt water to increase awareness by the healthcare provider.
Salt Water Toxins
Many of the health concerns occur in salt water and brackish water, which is the area where a river meets with sea, and fresh and salt water mix. One of the bacteria that thrive in salt water is Vibrio, which is prevalent in higher concentrations in coastal waters between May and October as temperatures rise. This timing coincides with hurricane season with severe storms that affect the coastline and allow seawater to come inland during flooding (CDC, 2019d).
There are over a dozen Vibrio species that cause a human illness known as vibriosis. The three most common disease-producing types include Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus. Other forms of Vibrio can cause cholera, but these are not addressed in this discussion. Briefly, cholera is caused by Vibrio cholerae and is rare in the US but is frequently found in Africa, Southeast Asia, and Haiti, (CDC, 2017d). Vibrio can cause disease in two primary ways within coastal waters. First, it can be contracted through eating raw or undercooked shellfish. Undercooked or raw oysters seem to produce the highest level of risk for disease development. The second is skin exposure to Vibrio in salt or brackish water, which can lead to a skin infection in the presence of an open wound (CDC, 2017d, 2019d).
Individuals with an impaired immune system or liver disease are at the highest risk for infection and complications with exposure to Vibrio. The CDC (2019d) reports approximately 80,000 illnesses each year related to Vibrio and about 52,000 of these result from eating contaminated food. Most people recover from vibriosis within 3-4 days and do not endure lasting effects. Vibrio infections from contaminated food may have the following symptoms:
- watery diarrhea within 24 hours of exposure,
- stomach cramping,
- chills (CDC, 2017d).
Occasionally, individuals who acquire a Vibrio vulnificus infection become seriously ill requiring intensive care and in most severe cases, limb amputation. Approximately 1 in 5 people with this infection die within a couple of days of becoming sick. Vibrio vulnificus can cause two types of infections; 1) wound infection that starts as redness and edema at the wound site, which quickly spreads to other parts of the body, or 2) primary septicemia, which is a bloodstream infection presenting with fever, hypotension, and blisters on the skin (CDC, 2017d, 2019d).
The diagnosis of a Vibrio vulnificus infection is based on the presence of Vibrio bacteria in wound, blood, or stool cultures from the patient. These cultures should be sent to the public health laboratory. Blood cultures are recommended for a febrile patient presenting with hemorrhagic bullae (blisters) or any other signs of sepsis.
In mild cases of Vibriosis due to ingestion, oral fluid replacement from diarrhea is recommended, along with over-the-counter anti-diarrheal medications as needed. In more severe cases, IV fluids may be needed for fluid replacement (CDC, 2017b).
Vibriosis is treated with antibiotics such as doxycycline (Vibramycin, Doryx), along with a third-generation cephalosporin such as ceftazidime (Fortaz, Tazicef). Single-agent antibiotics such as a fluoroquinolone are reported by the CDC (2019d) to be less effective than the combination therapy of ceftazidime (Fortaz, Tazicef) and doxycycline (Vibramycin, Doryx). When treating children, trimethoprim-sulfamethoxazole (Bactrim, Septra) plus an aminoglycoside such as gentamycin (Garaymycin) is preferred due to the contraindication for doxycycline (Vibramycin, Doryx) and fluroquinolones such as ciprofloxacin (Cipro) within this age group (CDC, 2017b).
While the CDC (2017d) reports only around 200 cases of Vibrio vulnificus each year, these cases are typically life-threatening. During the summer of 2019, cases of necrotizing fasciitis (“flesh-eating bacteria”) were identified across the US in Florida, Texas, Alabama, Delaware, Maryland and Virginia (Mazziotta, 2019). Several types of bacteria are associated with necrotizing fasciitis, including Group A Streptococcus, which is also the bacterium that causes strep throat. However, in the coastal waters, most of these infections are related to Vibrio vulnificus. While the bacterium is always concerning for the exposed individual, there is often an immunocompromised host in cases where serious illness ensues. Overall, this infection has poor outcomes (CDC, 2019). In wound infections, necrotic tissue is debrided, and full amputation may be required to remove the dead or infected tissue (CDC, 2017d).
Protection from Vibrio Infection
The CDC (2017d) provides strategies that the nurse can share with patients to protect them from Vibrio vulnificus wound infections. Patient education should include the following:
- Avoid brackish or salt water with an open wound.
- If entering brackish or salt water with an open wound, the wound should be covered with a waterproof bandage to prevent direct contact with the water. Wounds should also be covered if handling raw seafood or the juices from raw seafood (such as restaurant workers).
- If a wound comes in contact with brackish or salt water, raw seafood or the juices from raw seafood, it should be washed it immediately with soap and water.
- If skin infection or sensitivity develops, immediately report the exposure so that prompt treatment can be initiated.
- If wounded or exposed to brackish or salt floodwaters during a natural disaster, clean the wound as soon as possible. They should see a healthcare provider if a wound develops redness, swelling, or drainage. Other reportable symptoms are increasing pain, shortness of breath, fast heart rate, confusion, or any abnormal symptoms (CDC, 2017d).
The ingestion of Vibrio vulnificus can lead to subsequent illnes
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Fresh Water Toxins
While fresh waters across the US put individuals in danger of toxins, Naegleria fowleri is a "heat-loving, free-living amoeba" commonly found in Florida and other southern states with warm climates. Naegleria fowleri is the only species of Naegleria that is known to infect humans. This amoeba lives in fresh water and feeds on bacteria. In rare instances, it enters the nose of a human during water activities such as diving or swimming. Once in the nose, Naegleria fowleri travels to the brain and causes a severe infection called primary amebic meningoencephalitis (PAM), which is typically fatal (CDC, 2017c).
While PAM has been detected in Florida since the early 1960s, there has recently been new cases diagnosed within other southeastern states such as Texas. There have only been 145 cases of PAM in the US since 1962. Of these 85% have been in children and adolescents, and over 75% in males. This amoeba has a specific life cycle (See Figure 1) that affects transmission and subsequent disease (CDC, 2017c).
The heat-loving Naegleria fowleri thrives in hot springs and in the human body with a preferred temperature of 115° F. The trophozoite state (the feeding stage of a protozoan parasite), is relatively sensitive to environmental changes, including temperature, while the cysts are much more tolerant to changes in their environment. The trophozoites are killed quickly by cooler temperatures for even short periods of time but the cysts can survive the cold for weeks to months. This provides an opportunity for the amoeba to be found in almost any lake or river and eliminates all methods of controlling the natural levels of this parasite. The only thing that appear to make the cysts nonviable is drying them out. Fortunately for the healthcare environment, both chlorine and chloramine kill Naegleria fowleri trophozoites and cysts. The amoeba does not survive in salt water and has not been detected in the ocean (CDC, 2017c).
A patient presenting with PAM develops symptoms within 1-9 days after exposure. Early symptoms include headache, fever, nausea, and vomiting. Later symptoms include stiff neck, confusion, photophobia, seizures, and cranial nerve abnormalities. Focal deficits and meningeal signs are typically present upon examination. The signs and symptoms mimic bacterial meningitis, and occasionally nasal discharge, nasal obstruction or changes in taste and smell are present. Disease progression is swift; coma, leading to death, can occur 1-18 days after the onset of the symptoms (CDC, 2017a).
Diagnosis of PAM is made through the visualization of Naegleria fowleri under the microscope in a fresh, unfrozen, unrefrigerated cerebrospinal fluid (CSF) sample, as freezing the sample will kill the amoeba. Diagnosis can also be made via examination of tissue from a brain biopsy or autopsy specimen. Serology testing is currently being developed, but not considered a clinical diagnostic option at this time. Indirect immunofluorescent antibody (IFA) testing can measure serum antibody titers in a patient, but most will die before the immune response is mounted. When possible, the CDC requests specimens be sent for diagnostic confirmation to the CDC with fresh CSF, tissue obtained through a brain, or formalin-fixed and paraffin-embedded tissue. For further directions on sending tissue samples to the CDC, please see their website and search for the Free-Living Amoeba Testing Factsheet (CDC, 2018b).
To prevent infection, patients can be instructed to wear a nose clip to avoid any water entering the nasal passageway while swimming (CDC, 2019b).
There have only been four known survivors of PAM since its origin in 1962. Treatment recommendations are based on the survivor’s treatment combinations:
- Amphotericin B (AmBisome), 1.5 mg/kg/day in 2 divided doses is administered via IV for three days, then,
- Amphotericin B (AmBisome), 1 mg/kg/day via IV once daily for 11 days.
- Amphotericin B (AmBisome) 1.5 mg once daily, intrathecally for two days, then,
- Amphotericin B (AmBisome) 1 mg/day every other day, intrathecally for eight days.
- Azithromycin (Zithromax) 10 mg/kg/day once daily IV or PO for 28 days.
- Fluconazole (Diflucan) 10 mg/kg/day once daily IV or PO for 28 days.
- Rifampin (Rifadin, Rimactane) 10 mg/kg/day once daily IV or PO for 28 days.
- Miltefosine (Impavido) with a maximum dose of 2.5 mg/kg/day PO for 28 days.
- Dexamethasone (Decadron) 0.6 mg/kg/day in four divided doses IV for 4 days (CDC, 2019c).
The CDC suggests that any healthcare provider caring for a patient with suspected PAM or other amoeba infection contact the CDC Emergency Operations Center at 770-488-7100 to consult with experts in the management of these patients. Miltefosine (Impavido) is an antiparasitic that is mildly nephrotoxic, so dosing should be adjusted for individuals with renal conditions. There is increased risk of mortality with reduced doses, so the risk of nephrotoxicity should be balanced with the risk of dose reduction when deciding on treatment (CDC, 2019c).
Although PAM is extremely rare, just recently a 59-year-old North Carolina man was diagnosed with PAM in 2019 and died shortly thereafter. Of the 4 known survivors of PAM, only one endured life-altering brain damage (Mole, 2019). The Medscape website provides expert commentary on Brain-Eating Amoebas from CDC epidemiologist, Dr. Jennifer Cope. According to Cope (2013), boys are more likely to be impacted than girls due to the types of water activities males participate in that cause splashing into the nasal passages such as diving and watersports. In addition to swimming and water sports, two cases of PAM were reported in Louisiana in 2011 related to neti pots, which are used for sinus irrigation. The source was tracked to Naegleria fowleri-contaminated household tap water (Cope, 2013).
Algae Blooms and Brevotoxins
Algae are simple, nonflowering aquatic plant life that include seaweed and many single-celled organisms. They contain chlorophyll but lack true stems, roots, leaves, or vascular tissue. Among the single-celled algae are prokaryotic organisms called cyanobacteria or blue-green algae. These algae are found most frequently in fresh water sources within Florida and other parts of the country; however, they can also be found in estuarine and marine water in the US (United States Environmental Protection Agency [EPA], 2019b). Algae naturally help to sustain marine life as part of the food chain. However, when the conditions are right, specific algae can grow unconstrained and over-populate. The optimal conditions for this extreme growth are warm water and increased nutrients. Commonly referred to as blooms, they have been linked to the overuse of fertilizer and other gardening chemicals along with climate change. Increased temperatures cause significantly more algae blooms. Other parameters such as salinity (amount of sodium in a body of water), water flow, rainfall, wind speed, and wind direction can all impact how the bloom increases in size, where it forms, and how it moves to expose humans and animals. Algae blooms and their associated health and environmental impacts must be dealt with (Mosford, 2018).
When overgrowth occurs, the algae form a foam or scum-like mass known as an algae bloom. These blooms can be moved around by wind, waves, currents or tides. They release toxins into the ecosystem, making people and animals sick. When this occurs, the algae bloom is known as a "harmful algae bloom" or HAB (Florida Health, 2019).
In most cases, the HABs are short-lived, occur in late summer to early fall along the coast of Florida, and they vary in size and severity. Some HABs emit a foul odor due to the hydrogen sulfide gas that naturally occurs from decomposition within the bloom. The smell is compared to rotten eggs, causing most humans to avoid it whenever possible. In 2016 and 2018, the Florida Department of Health tested air quality around the HAB events and found the levels to be non-hazardous to human health, despite the unpleasant smell (Florida Health, 2019).
A HAB formed from blue-green algae creates problems for those who splash through the bloom, releasing cyanotoxins into the air. The primary toxin of concern is Beta-N-methylamino-L-alanine, or BMAA. BMAA can lead to acute illness in humans and may also be linked to long-term brain diseases. Humans should avoid this HAB as it can lead to illness of the respiratory, gastrointestinal or nervous system (CDC, 2019a). Exposure is through three routes: 1) skin contact, 2) inhalation, or 3) ingestion. The toxins mix with the water droplets and spray, allowing both humans and animals to inhale or ingest the toxin. Ingestion can also occur through eating or drinking water or food that is contaminated with the toxins. It is more difficult for the toxins to pass through the skin; however, skin exposure can cause topical irritation or rashes. The extent of the irritation will be dependent upon the length of time for exposure. The blue-green algae blooms are primarily blue, bright green, brown or red and have an odor similar to rotting plants. Pets can become sick from exposure and should be kept away from contaminated fish or marine animals (CDC, 2019a; Florida Health, 2019).
Exposure to drinking water with elevated concentrations of the cyanotoxins microcystin and cylindrospermopsin can lead to liver or kidney damage. Exposure to cyanobacteria and cyanotoxins can range from mild rashes, respiratory and gastrointestinal distress and in rare instances, death (EPA, 2019a). Table 1 shows the effects of specific cyanotoxins and the impact to humans.
Table 1: Cyanotoxins and Their Health Effects on Humans
Diagnosing cyanobacteria exposure
Symptoms will vary depending on the amount and type of exposure, but general symptoms may include:
- Nausea or vomiting
- Neurological symptoms
- Abdominal pain
- Skin, eye, throat, or nose irritation
- Blisters or rash
- Weakness or fatigue (CDC, 2019a).
Many people will present with coughing and eye irritation when in close proximity to the HAB and symptoms may subside upon leaving the area. In addition to the specific type of cyanotoxin exposure, increased exposure time and comorbidities of the patient leads to more severe symptoms (CDC, 2019a).
Treatment for cyanobacteria exposure
Early identification of patient exposure to an HAB can aid the provider in the diagnosis and guidance for potential treatment. Other illnesses with similar symptoms should be ruled out to ensure an accurate diagnosis. There are no specific tests or specific antidote treatment for cyanobacteria. Laboratory tests that may be performed to aid in the diagnosis, along with patient history, include:
- Electrolytes and liver function tests: BMP, ALT, AST,
- Renal function tests: BUN and creatinine,
- Serum glucose,
- Urine to check for proteinuria and glycosuria (severe toxicity), and/or
- Chest x-ray in patients presenting with respiratory symptoms (CDC, n.d.).
Specialized laboratories can perform confirmatory lab tests for cyanobacteria and cyanotoxins in feces, urine, gastrointestinal contents, tissues, blood, and water specimens (CDC, n.d.).
Treatment is primarily supportive and focuses on symptom management. Treatment for respiratory symptoms often includes the use of antihistamines and steroids. Gastrointestinal symptoms should be managed with anti-emetic or anti-diarrheal drugs. For eye exposure, the nurse should have the patient remove any contact lenses and assist them to irrigate the eyes for at least 15 minutes with normal saline. An ophthalmologist referral is suggested if symptoms persist after irrigation (CDC, n.d.).
Patient education related to cyanobacteria exposure should include the following:
- Avoid HAB contaminated waters.
- If exposure to contaminated waters occur, wash any exposed areas with soap and water.
- Initiate symptomatic treatment for respiratory or gastrointestinal conditions as indicated.
For pets who have been exposed through drinking contaminated water or eating contaminated marine animals, prompt veterinarian treatment should begin immediately as they can become very sick quickly (CDC, 2019a).
A second toxic algae bloom to consider is red tide caused by Karenia brevis (Florida Health, 2019). Karenia brevis produces brevotoxins, which are tasteless, odorless neurotoxic compounds that can cause toxicity through inhalation, oral, or dermal exposure. The most common route of transmission of Karenia brevis is through contaminated shellfish. Patients can also be exposed through the red tide algae blooms in coastal areas, such as most recently the southwest coast of Florida (CDC, 2018a).
For those who live in or visit Florida, the word "red tide" is likely familiar. Red tide is most often caused by the algae species, Karenia brevis, primarily found in the Gulf of Mexico. This HAB has a dark red or brown color and produces brevotoxins capable of killing marine animals and making humans and land animals sick. The Florida Department of Health encourages all residents and visitors to avoid any areas of red tide. Pets can become symptomatic from exposure to red tide and should also avoid these areas, as well as any contact with contaminated fish or marine animals (Florida Health, 2019).
Fish and any other marine life from a red tide area should not be consumed, and people/pets should avoid swimming or walking in water that is contaminated with red tide. Eating contaminated shellfish can lead to an illness called neurotoxic shellfish poisoning (NSP) (Florida Health, 2019).
Exposure to the HAB can induce red tide tickle, which is an illness characterized by a scratchy throat and cough secondary to breathing in the airborne brevotoxins. These toxins are released into the air when the wind or waves break open the algae cells. Healthy individuals can develop respiratory symptoms rapidly after exposure to HAB. In addition to red tide tickle, additional further respiratory problems, eye irritation, and nasal irritation are reported. For those with chronic respiratory conditions such as asthma, COPD, or emphysema, red tide can induce acute exacerbation of their preexisting symptoms. Other symptoms of NSP include nausea, vomiting, tingling of the mouth and tongue, dizziness and slurred speech. In most severe cases, the neurological symptoms can progress to partial paralysis (CDC, 2018a; Florida Health, 2019).
Symptomatic evaluation with a history of potential patient exposure to red tide can aide the healthcare provider in determining the diagnosis. Laboratory diagnosis can be achieved through the detection of brevotoxins or their metabolites in a urine specimen through immunoassay (CDC, 2018a).
Treatment for brevotoxins
For physical contact with red tide/brevotoxins, it is advised to immediately wash the contaminated area with soap and water. For rashes or skin irritation, hydrocortisone cream may be used to decrease the symptoms (Fleming, 2019).
Those with continued respiratory symptoms can be advised to take over-the-counter antihistamines. For more severe or persistent symptoms, patients should be evaluated by a healthcare provider and may prescribe stronger antihistamines, steroids, bronchodilators, inhalers, oxygen or other supportive therapy to ensure patency of the airway (Florida Health, 2019).
Protection from Aquatic Toxins
The healthcare provider can offer education to avoid exposure to toxins within waterways in the local environment. The primary way to avoid exposure to aquatic toxins is to avoid both fresh and salt water where algae blooms are present. Pets should not be allowed to lick their fur until the toxin is washed away. When visiting state or local waterways, patients should be encouraged to review official/health department reports and adhere to any warnings or local conditions that would direct activities in the water. If there is a notification of harmful algae in the public drinking water supply, all local or state guidelines should be followed to minimize risks. Finally, patients should avoid eating any seafood that may be contaminated from HABs and their toxins (CDC, 2019a).
The nurse should encourage patients to check the Searchable Database of Bloom Records found at Florida Health’s website, which shows a real-time map of current blooms and guidelines to avoid health concerns (Florida Health, 2013).
The CDC (2019a) reports that people can have exposure to HAB toxins up to four miles inland from a contaminated water source. Since marine HAB can cover hundreds of square miles, boaters, homeowners, residents, and tourists can be impacted by the toxins. Unfortunately, the only way to avoid exposure is to stay out of the area that is currently affected. This can be difficult for those who work or live in the area (CDC, 2019a). For aerosolized toxins, the use of particle filter masks when outdoors can decrease exposure. For those who live near the HAB, remaining indoors with air-conditioning can reduce the severity of respiratory symptoms (Florida Health, 2019). Ingestion can be prevented by avoiding raw seafood, especially oysters. Not only can shellfish and marine animals directly in the HAB area be contaminated by the toxins, but also larger fish that may feed on these local animals further up the food chain (CDC, 2019a). Fish that have been tested for exposure to blue-green algae have demonstrated that there is not a high accumulation of cyanotoxins in the edible parts, but there may be a high level in the organs. Florida Health suggests that the guts of fish are thrown away and that all fish are cooked well before eating (Florida Health, 2019).
Tap water can contain HAB toxins, but this is uncommon, even in areas with high levels of toxins. There are currently no federal guidelines related to acceptable levels of cyanobacteria or cyanotoxins in public drinking water. Exposure can also occur through healthcare facilities, but this risk remains very low. Nutritional supplements that contain algae could pose a risk for exposure to HAB toxins. During algae harvesting for the production of supplements, toxin-producing cyanobacteria could accidentally be included, contaminating the supplement (CDC, 2019a).
The CDC has suggestions on reducing exposure through the following:
- Avoid bodies of water that look discolored or smell bad.
- Avoid bodies of water that have foam, scum, or algae mats on the surface.
- Avoid bodies of water that contain or are near dead animals or dead fish, including those washing up on shore from the ocean.
- Boiling water does not remove algal toxins and can instead increase the number of toxins in the water by concentrating it.
- Follow all state and local water advisories (CDC, 2019b).
Patients should be cautioned to never drink from ponds, lakes or rivers, and do their best to avoid incidentally swallowing any water while swimming. Toxins or germs can be present even where the water does not look contaminated. The public should also avoid filling pools with water directly from lakes, rivers, or ponds as they may contain toxins or germs that cannot be killed through routine pool maintenance (CDC, 2019b).
Preventing the Formation of HABs
As with all health concerns, prevention is preferred over treatment. There are large-scale efforts across the US to reduce the incidence of HABs, primarily through decreasing the amount of nitrogen and phosphorus polluting our waterways. Suggestions to support these initiatives include:
- Use only recommended quantities of fertilizer on individual lawns to reduce the amount of runoff nutrients going into local waterways.
- Maintain septic systems to prevent the leakage of wastewater and seepage into nearby waterways. Wastewater is a rich source of nutrients for algae.
- To report an observed algal bloom in a lake or freshwater river in Florida, or for more information on Florida initiatives to clean up waterways and decrease the risk of aquatic toxins (Protecting Florida Together) please contact the Florida Department of Environmental Protection (DEP): 855-305-3909 or FloridaDEPgov/AlgalBloom
- To report stranded wildlife, fish kill, or information about red tide and other saltwater algal blooms in Florida, please contact Florida Fish & Wildlife Conservation Commission (FWC): 800-636-0511 (fish kills) 888-404-3922 (wildlife alert) or MyFWC.com/RedTide
- Other Florida Public Health Concerns: Contact the local County Department of Health or
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