Food Poisoning At Sea
By Domenic A. Sammarco, R.Ph., EMT
As with most travelers, sailors are prone to food poisoning and should be knowledgeable on the facts and possible corrective action as to possibly prevent and treat this acute illness. Please use the following information to assist you and your crew on preventing food poisoning.
The human body, and especially the gastrointestinal tract, is home to hundreds of different types of bacteria. All of these bacteria produce various chemicals as they go about their business of reproducing and turning sugars to energy. Some of these chemicals are harmless and go unnoticed. Others actually help us digest food. Some chemicals, however, can damage or inflame our internal organs. Bacteria that produce such chemicals are the disease-causing (pathogenic) bacteria. In infectious diseases, it's actually these toxic chemicals and not the bacteria themselves that make you ill.
Most cases of food poisoning occur when people eat food containing bacterial toxins. Contrary to popular belief, the bacteria themselves are usually long dead or gone when this happens. If they were still there, it wouldn't technically be food poisoning, but a food borne gastrointestinal infection. Salmonella and bacterial gastroenteritis are examples of such infections.
The other kind of food poisoning occurs when inorganic poisons or non-bacterial organic poisons (such as poisonous toadstools) find their way into people's stomachs. Both types are covered here, but other illnesses caused by bacterial poisons, such as botulism, are covered in their own sections.
The main types and causes of food poisoning include:
Staphylococcus: This universal bacterium causes many skin infections. People who have staphylococcus infections and handle food can transfer these bacteria to others. The bacteria then breed and produce an enterotoxin (stomach poison), which causes a temporary attack of diarrhea and stomachache. The types of foods most likely to carry Staph toxins are custards, cream pies, milk, fish and processed meat.
Mushrooms and toadstools: Dozens of species can cause muscarine poisoning. These poisons attack the central nervous system, causing partial or complete paralysis in severe cases. The mushroom Amanita phalloides and its cousins are the deadliest of all food poisons. Even with modern medical treatment, about 50% of cases result in death after a few days. However, this is a very rare occurrence.
Fish: Some fish, like the puffer fish, are naturally poisonous. A poison similar to that naturally found in the puffer fish can also occur in many edible Caribbean and Pacific species. It's called ciguatera poison, and it's produced by a tiny sea parasite called a dinoflagellate, also known as "red tide". The poison attacks the nervous system, and can be fatal. The other kind of fish poison, called scromboid poison, is concentrated histamine produced by the mass death of bacteria in the fish after it was caught. Histamine is the chemical that causes the airways to become inflamed and blocked in asthmatics. It has similar effects on other organs.
Shellfish: Clams, mussels, oysters and scallops are particularly prone to ingesting red tide, and therefore may contain ciguatera poison. In North America the red tide arrives between June and October. Shellfish eaten during those months are potentially dangerous.
Insecticides: There are many types of poisons found in insecticides, including benzene-based poisons like DDT that have effects similar to gasoline, but the most dangerous types are the organophosphates, which are basically nerve gas for insects, but the chemicals involved are themselves dangerous.
These represent a tiny fraction of the possible causes of food poisoning. Others include wild nuts, leaves, flowers and berries, under-ripe tubers, botulism, cadmium from containers, lead or arsenic from fertilizers, and acids and lead from pottery. Then there are the stomach infections caused by eating contaminated food: shigellosis, salmonella, infant botulism, some types of E. coli and Clostridium perfringens are among the food borne diseases you can catch in North America.
Symptoms and Complications
Many of the poisons listed here attack the central nervous system and cause symptoms typical of nerve poisons. Eating a red-tide-contaminated shellfish, for example, will produce weakness or paralysis around the mouth in a few minutes, which slowly spreads to the rest of the body. Other neurologic signs of ciguatera poisoning include face pain, headache, itching and odd sensations of alternating hot and cold.
Symptoms of mushroom poisoning also have a nervous element. Shrunken eye pupils, tears, salivation or frothing at the mouth, sweating, vertigo, confusion, coma, and sometimes convulsions appear within two hours of eating a poisonous mushroom. Insecticides based on organophosphates cause very similar symptoms. They're likely to be milder, since it is extremely rare for really large doses of insecticide to be eaten accidentally.
Scromboid (histamine) fish poisoning causes the symptoms of excess histamine. Flushing, skin rash, and pain from overstimulation of affected organs, namely the stomach and intestines, appear within a few minutes. Fortunately, the histamine is in the gastrointestinal tract and not the respiratory tract, where it could cause a serious, sometimes fatal, asthma attack. Fish containing toxic levels of histamine, unlike fish contaminated by red tide (ciguatera) poison, often taste unusually bitter or spicy.
Almost all forms of poisoning also produce nausea/vomiting, abdominal cramps and diarrhea. This is the result of the body trying to get rid of the offending substance. This is what most people think of when they think of food poisoning. Staphylococcus enterotoxin poisoning produces only these symptoms, which usually appear 2-8 hours after eating the poison. The whole episode tends to last much less than a day.
Making The Diagnosis
Getting the right diagnosis early can be vital in poisoning. Some poisons have specific antitoxins that will cure them completely, but you can't take the antitoxin if you don't know what the toxin is.
When people are poisoned in groups, it's usually easier to pinpoint the cause. Often, there's only one food that all sick the sick people ate, and this can be studied to find the nature of the poison. Such details may be the only clue, because you can't easily test people for poisons the way you test them for infection.
Treatment and Prevention
Some poisons have specific drugs that effectively counteract their toxicity. More often, a drug is given that's known to be effective against a certain type of poisoning. Mushroom (muscarine) poisoning, for example, can be countered with atropine, which is the drug that soldiers carry in case of nerve gas attack.
Whether or not there's an antidote, the most important part of treatment is often evacuating the poison from the body. Emesis is the deliberate induction of vomiting. It's usually done with ipecac syrup, but soapy water works in a crisis. The earlier it's done, the better. You might consider doing this yourself if you're confronted with food poisoning far from a hospital. Only induce vomiting if you see clear signs of dangerous poisoning (i.e., not just Staph), and if the victim is fully conscious and not convulsing.
At hospital, the efforts to clear the poison will continue. The techniques used are gastric lavage, in which a tube is inserted by mouth into the stomach and the stomach is pumped clean with liquids, Charcoal, which when swallowed absorbs poisons faster than the lining of the stomach does, may also be administered. People suffering from nerve poisons, like mushrooms, botulism, and ciguatera, also need to be watched for signs of respiratory failure and given artificial breathing assistance if necessary. Kidney dialysis and replacement of lost fluids and nutrients may also be required.
You can't always prevent food poisoning. Ciguatera poison, for example, is tasteless, and can't be destroyed by cooking or even radiation. We have yet to invent a process that could find and neutralize the poison without destroying the fish or shellfish, so if you want to be truly safe you'll have to stick to Atlantic fish.
Some foods are more prone than others to infection. Green vegetables and carrots, for example, are less likely to be toxic than fish or meat. On the other hand, the last sizable outbreak of salmonella in Canada was caused by cantaloupe.
The following advice won't protect you against all types of food poisoning, but you'll know you did your best:
- Wash your hands thoroughly before and during cooking.
- Try to keep different food and food types separate.
- If you're keeping leftovers, refrigerate them immediately.
- When reheating food, cook it thoroughly enough that the core reaches at least 75oC or 168oF. This won't remove all poisons or even kill all bacteria, but it helps against some common kinds.
- Pay special attention to thoroughly cooking meat and poultry.
If you have a skin infection like impetigo (staphylococcus), don't prepare food for others while spots or sores are visible.
Every captain should maintain a well-stocked first-aid cabinet with the proper selection of pharmaceuticals for your voyage. A trained pharmacist should be able to review your voyage or travel plans and develop an appropriate ship's formulary based on environmental, endemic and duration of time at sea. For further information please contact us at Marine Medical Systems 1-800-272-3008.