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How Harmful Algae Affect Human Health

Updated on June 10, 2015
Toxic algae in seafood
Toxic algae in seafood | Source

Bodies of water attract those who love to be close to Nature. If you are one of them, then you should always be aware of the dangers they may contain, such as harmful algae. Awareness of these organisms can help you have a safer, more pleasant experience during picnics, fishing, swimming, or water exploring.

If you love water and you want to be safe in and around it, you should know more about harmful algae. Your health matters most and you do not need harmful algae to ruin it, in just a swim or two.

Harmful Algae Bloom

Detrimental algae are micro-algal blooms, red tides, phytoplankton blooms, and toxic algae. You should know that about three hundred species of micro algae form algal blooms. Almost one fourth of these algal species produce toxins. HAB (Harmful Algal Blooms) is the generic term for such events. In HAB, many organisms are involved. Take note that some algal species affect at low cell densities. In addition, not all HABs occur as blooms and not all HABs are algal.

Why HABs are Harmful

Below are some reasons HABs are harmful:

  1. In brackish or marine waters, can bring about massive fish kills.
  2. Alter marine and freshwater environments
  3. Incorporate toxins into seafood.
  4. Cause anoxia in marine life when present in dense concentrations.

The HAB issue is now getting serious, since man has already altered what used to be untouched bodies of water. HABs destroy livelihoods and coastal resources. Because of this, sustaining human populations becomes a challenge.

Affected seafood
Affected seafood | Source

Food Resources and Harmful Algae

Finfish and shellfish are affected by harmful algae. Though there are no visible effects, the algal toxins accumulate in the vital organs of these organisms. The toxins that stay in these aquatic food sources are transmitted to humans through their consumption. Contaminated seafood is a huge health threat. When cooked, the amount of toxins present in the seafood does not decrease or change at all. They are undetectable because the presence of the toxins does not affect the taste of the food. There is no straight forward way to detect algal toxins in food, so no one can really be sure if the seafood is safe or not.

Extensive monitoring and chemical analyses of the seafood are performed to reduce the risk of being poisoned. Developing countries have seafood as their sole food source. It is their primary source of protein. Aquaculture is an important resource now because of overfishing. High levels of quality control and surveillance are implemented to reduce the possibility of seafood poisoning.

Mussel | Source

Toxic Health Effects of Harmful Algae on Humans

People who reside in tropical regions are harassed by syndromes and conditions brought about by eating contaminated seafood. The diseases acquired from these algal toxins can be fatal. There is no accurate number of cases and fatalities from contaminated seafood. Most of them turn out to be unreported or undiagnosed.

As of today, the following are the recognized human syndromes, resulting from the ingestion of affected seafood:

1. CFP (Ciguatera Fish Poisoning)

CFP is not that lethal, but there have been fatalities. It is transmitted by a number of reef fish in the tropics. CFP brings about neurological, cardiovascular, and gastrointestinal conditions. It usually takes months or even years to recover from Ciguatera. From 1960 to 1984, 2,400 cases of CFP were recorded in French Polynesia. Activities such as tourism and hurricanes, have provides appropriate habitats for the dinoflagellates, which produce maitotoxin and ciguatoxin.

2. ASP (Amnesic Shellfish Poisoning)

This can be a life-threatening syndrome. ASP is caused by the domoic acid, accumulating in shellfish. This condition can also be fish-borne, so human consumption is inevitable. This disease has serious effects on humans, characterized by neurological and gastrointestinal conditions. The affected human can also suffer from memory loss. Canada is the present hub of this disease, but the causative organism cam spring up anywhere in the world. Be aware of Pseudo-nitzchia blooms. Symptoms appear a day after ingesting contaminated shellfish. The patient experiences disorientation, dizziness, permanent short-term memory loss, and headaches. Severe cases involve focal weakness, paralysis, seizures, and death.

3. DSP (Diarrhetic Shellfish Poisoning)

This type of condition spreads widely. It causes disturbances in the GI tract, such as abdominal cramps, diarrhea, and vomiting. DSP is not fatal at all. Patients get back on their feet in just a few days. Incidents of DSP have always been regarded as the usual stomach disorder. Chronic DSP is thought to help in tumor formation in the digestive tract.

4. PSP (Paralytic Shellfish Poisoning)

PSP is life threatening. It has neurological effects and has no antidote. Cases have grown in number over the years. About 15% out of 2,000 cases result in fatalities. After ingesting contaminated shellfish, symptoms appear fifteen minutes to ten hours. Usually, patients report having symptoms after only two hours of eating the bad fish product. Patients feel some tingling or numbness of the extremities and the face. Nausea, incoordination of muscles, headache, floating sensation, and dizziness follow. Severe cases involve respiratory failure, muscle paralysis, and death in two to twenty-five hours.

5. SFP (Scombrotoxic Fish Poisoning)

This is also known as histamine or scombroid poisoning. It is brought about by spoilage of bonito, tuna, or mackerel. When the finfish breaks down, histamine becomes the byproduct. Other substances in the spoiled fish prevent histamine from breaking down. As a result, the histamine accumulates in the fish. Once humans ingest the affected fish, symptoms start within two minutes to two hours. Expect diarrhea, vomiting, flushing, rashes, headache, and sweating. Metallic taste, swelling of the mouth, and abdominal pain may also occur. Mild symptoms disappear within two hours. Severe symptoms show in patients that take doxycycline and isoniazide, which slow down the histamine breakdown in their liver.

6. NSP (Neurotoxic Shellfish Poisoning)

This used to be confined in the Gulf of Mexico. Yet, in 1993, cases from New Zealand have been reported. NSP is characterized by neurological and gastrointestinal disturbances. Patients with NSP recover after a few days. Asthma-like symptoms are formed by the toxic aerosols. About one to three hours after ingesting contaminated shellfish, symptoms begin to show. Patients usually experience tingling of the extremities and of the mouth, numbness, gastrointestinal problems, and incoordination. They normally recover within two to three days.

Clams | Source

The Causative Organisms

Below are some of the known causative organisms of the given harmful algae:

a) Prymnesiophycae or Haptophycae

This organism has killed many fish, but is not considered a human health threat.

b) Dinophycae or Dinoflagellates

These cause PSP (Pyrodinium bahamense var. compressum and of Alexandrium), NSP (Gymnodinium breve), DSP (Dinophysis and Prorocentrum. Dinophysis), and Ciguatera (Gamberidiscus toxicus).

c) Bacillariophycae

This also causes ASP (P. multiseies, P. pseudoelicatissima , and Pseudo-nitzschia australis).

d) Cyanophycae

Nodularia and Trichodesmium are not associated with any human syndrome. They usually occur in brackish and freshwater environments. It becomes a human health threat when if it reaches the surface water, which is used for drinking water.

e) Raphidophycae

This poisonous organism extensively kills fish. It easily deteriorates when preserved. Scientists identify it through actual observation of live cells.

Infected shellfish
Infected shellfish | Source

Be mindful of the sources of your seafood. Make sure that they are not contaminated by any harmful algal bloom. Prevention is always better than cure. If you do happen to ingest a contaminated fish or shellfish, seek immediate medical attention.

Paralytic Shellfish Poisoning (Long Island)


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