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 Infectious agents cause most shellfish-associated illness. Hepatitis A, Norwalk virus, Vibrio parahaemolyticus, and Vibrio vulnificus all have been transmitted through shellfish ingestion. Toxic illness caused by shellfish has been recognized for several hundred years.The toxins responsible for most shellfish poisonings are water-soluble, heat and acid-stable, and are not inactivated by ordinary cooking methods. The main toxin responsible for PSP is principally saxitoxin, but also gonyautoxin.
Native Americans are known to have warned early settlers to avoid shellfish during the summer months. Since that time, at least 4 distinct shellfish-poisoning syndromes have been identified, as follows:
* Paralytic shellfish poisoning (PSP)
* Neurologic shellfish poisoning (NSP)
* Diarrheal shellfish poisoning (DSP)
ed by microscopic algae in the form of dinoflagellates and diatoms.
* Amnestic shellfish poisoning (ASP)
All 4 syndromes share some common features and primarily are associated with bivalve mollusks (eg, mussels, clams, oysters, scallops). These shellfish are filter feeders and, therefore, accumulate toxins produced by microscopic algae in the form of dinoflagellates and diatoms.Fish and shellfish poisoning is a common but often unrecognized group of illnesses related to food. Three of these illnesses include ciguatera, scombroid, and paralytic shellfish poisoning.
How to differentiate fresh shellfish from the old shellfish
When purchasing shellfish, you will need to look for signs of freshness and safety when going through the stock. The most obvious and easiest sign to catch is the look of the shellfish. The outer part of the shellfish must be fresh and the shell part must be tightly closed. This works for most types of shellfish such as scallops, clams, mussels and oysters. When testing prawns, try and press the body to see if it will spring back when you release. Another important factor to consider is the smell of the shellfish itself.
Paralytic shellfish poisoning
Definition
Paralytic shellfish poisoning (PSP) is a nervous system disease caused by eating cooked or raw shellfish that contain environmental toxins. These toxins are produced by a group of algae (dinoflagellates). It is unclear whether these toxins are related to the "blooming" of the algae, also called red tide because the algae can turn the water reddish brown. PSP occurs mostly in May through November.
Causes and symptoms
PSP develops usually within minutes after eating a contaminated shellfish, most commonly a mussel, clam, or oyster. Symptoms include headache, a floating feeling, dizziness, lack of coordination, and tingling of the mouth, arms, or legs. Muscle weakness causing difficulty swallowing or speaking may occur. Abdominal symptoms such as nausea, vomiting, and diarrhea can also occur. Unlike ciguatera and scombroid, PSP may have a much more serious outcome. PSP may cause difficulty breathing related to weakness or paralysis of the breathing muscle. The symptoms may last for six to 12 hours, but a patient may continue to feel weak for a week or more.
Diagnosis
PSP diagnosis is based on symptoms after eating shellfish, even if the shellfish are adequately cooked. No blood or urine test is available to diagnose the illness, but tests in mice to detect the toxin from the eaten fish can be done by public health officials.
Treatment
The treatment of PSP is mostly supportive. If early symptoms are recognized, the doctor will try to flush the toxin from the gastrointestinal tract with medications that create diarrhea. Vomiting may be induced if the patient has no signs of weakness. In cases where the muscles of breathing are weakened, the patient may be placed on a respirator until the weakness goes away. However, this measure is not usually needed. Likewise, the use of a machine to clean the blood (dialysis) has been used in severe cases.
Tags: paralytic shellfish poisoning PSP neurologic shellfish poisoning NSP diarrheal shellfish poisoning DSP amnestic shellfish poisoning ASP brevetoxin brevotoxin shellfish toxicity shellfish poisoning shellfish exposure shellfish ingestion |
