Fish and shellfish poisoning

Fish and shellfish poisoning is a common but often unrecognized group of illnesses related to food which includes ciguatera, scombroid, and paralytic shellfish poisoning. Ciguatera is a food-related illness that causes abdominal and neurological symptoms. It is caused by eating fish that have a toxin calledciguatoxin, usually red snapper, grouper, and barracuda. Ciguatera is commonon many of the islands in the Pacific Ocean. Most cases occur one to six hours after eating the contaminated fish. Initial symptoms are abdominal cramps,nausea, vomiting, or watery diarrhea. The most common symptoms involve the nervous system and include numbness and tingling around the lips, tongue, and mouth; itching; dry mouth; metallic taste in the mouth; and blurry vision. In more prominent cases, patients may complain of temporary blindness, a slow pulse, and a feeling of loose teeth. Patients may also have thestrange symptom of reversal of hot and cold skin sensations. In very severe cases, there may be breathing difficulties or low blood pressure. Ciguatera isdiagnosed by the symptoms after eating fish. There are no tests to detect the poisoning in people, but researchers have developed a test for the toxin left on remaining fish. The treatment for this illness is fluids (by mouth or through a vein) and medications to decrease the itching or to treat vomiting and/or diarrhea. Neurological symptoms may be treated with amitriptyline and other medications. Although death can occur, most patients with ciguatera recover. Recovery can be slow and some symptoms can last for weeks or months. Knowing the kinds of fish linked to ciguatera can help a person avoid eating high-risk fish.

Scombroid is a fish-associated illness caused by eating improperly refrigerated fish. Fish linked to this disease include yellowfin tuna, skipjack, bonito, and mackerel. Bacteria that are normally found in fish act directly on a chemical (called histidine) in the flesh of fish that are not properly cooled when stored, producing histamine and other chemicals that cause the illness when the fish is eaten. Symptoms occur as soon as 10 minutes after eating the fish, and can be confused with a fish allergy. Scombroid causes flushing of the face, sweating, a burning feeling in the mouth or throat, vomiting, diarrhea, and headaches. A rash that looks like a sunburn may occur, and a small number of patients have hives. Some patients have a metallic or peppery taste intheir mouths. In more severe cases, rapid pulse, blurred vision, and difficulty breathing can occur. Symptoms usually last about four hours. Scombroid poisoning is diagnosed on symptoms occurring after eating fish. There are usually no tests to detect it. Experimentally, however, elevated levels of histamine-related products have been found in the urine. It may be possible to testremaining fish flesh for histamine levels. Scombroid goes away on its own, but Antihistamines like diphenhydramine (Benadryl) shorten its duration. Some doctors have found that cimetidine (Tagamet) given through a vein may also behelpful. In rare, more severe cases, epinephrine (adrenaline) may be used. Sombroid is usually not serious. Adequate storage of the target fish prevents scombroid. Since the fish does not appear spoiled or smell bad, the consumer cannot detect the risk before eating it.

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. PSP occurs mostly in May through November. PSP develops usually within minutesafter 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. Symptoms include muscle weakness causing difficulty swallowing or speaking, difficulty breathing related to weakness or paralysis of the breathing muscle, nausea, vomiting, and diarrhea. The symptoms last 6-12 hours, but a patient may feel weak for a week or more. PSP diagnosis is based on symptoms after eating shellfish. No diagnostictest is available, but tests in mice to detect the toxin from the eaten fishcan be done. PSP can have a serious outcome. If early symptoms of PSP 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 is not weak. In severe cases, the patient may be placed on a respiratoror a machine to clean the blood (dialysis). The prognosis is quite good, especially if the patient passes the first 12 hours, when most deaths occur, without needing breathing support. Controlling PSP requires detecting rising numbers of algae in coastal waters by microscopic examination. By law, shellfishbeds are closed when levels of the toxin-producing organisms are above acceptable standards.

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