The practice of medicine includes the prevention of disease and injury as well as the treatment of illness. Prevention is the preferred method for maintaining good health.
Aboard ship, maintenance of the health of passengers, crew, and staff is essential for a successful journey. Specific measures can be taken to prevent, control, or remove threats to the health of those aboard ship. Such measures may be aimed at preventing injury, chemical or other toxic exposure, or infectious diseases. Measures that prevent infectious disease include avoiding risky behaviors; proper sanitation and food hygiene; control of animals and insects that carry disease; and, when indicated, chemoprophylaxis (use of medication or other chemicals to prevent
disease), immunization, and quarantine. Presenting educational talks and distributing pamphlets on how to minimize disease risk are also helpful. Those in command of the vessel are ultimately responsible for ensuring that effective preventive measures are in place.
A communicable (or infectious) disease is an illness caused by a specific infectious agent (such as a bacterium, virus, or fungus) or by a substance the infectious agent produces (toxin). The infectious agent or its toxic product may be transmitted directly from an infected person, animal, or the environment to a susceptible host patient, or it may be transmitted indirectly through an intermediate plant or animal host or a vector (often an insect).
Life aboard ship is a unique environment; one that has duties, routines, and activities that can increase a person’s chances of acquiring a communicable disease. These elements include:
crowding (easier to pass a cold to other crew in the bunkroom);
physical stress (irregular sleep patterns, changes in diet, weather extremes, noise);
self-contained food and water systems (susceptible to lapses in proper maintenance and cross-contamination with infectious agents);
exposure to cargos (animals and animal products such as hides and wool);
travel to other countries (exposure to diseases such as malaria, typhoid fever and cholera through contaminated food or water).
**What influences the occurrence and spread of a communicable (infectious) disease?
Three factors:1) the agent (e.g., a type of bacteria);2) the host (the individual or groups who are exposed to the agent);3)the environment (route of transmission). Disease transmission requires an agent that is capable of causing a disease, a host that is susceptible to the agent, and an environment that permits the agent and host to come together. For an infectious disease to circulate within a population there must be a chain of transmission from one infected host to another and a suitable route of spread.
**Why is it essential to understand the principles of preventing and controlling communicable diseases? The answer: to ensure safety aboard the ship. If most of the crew are ill (an outbreak), fewer will be able to operate the ship safely; medical supplies may run low and care may become inadequate. To prevent disease, one can direct efforts at the specific agent (e.g., Staphylococcus aureus), the host(vaccination to prevent measles) and/or the environment (sanitation improvements to prevent Salmonella). One can also target a specific point in the chain of transmission(e.g., Escherichia coli and adequately cooked hamburgers). Thus, it is important to
know how various diseases are spread, what can be done to prevent their spread,and what can be done to control them once they appear.
An infectious agent or its toxic product causes communicable disease in a susceptible host. Organisms that can produce disease in humans range in size from submicroscopic viruses to the fish tapeworm, a parasite that can attain a length of more than 30 feet. Several groups of infectious agents and toxins (and some examples of the diseases they cause) may be classified as follows:
Bacteria: bacillary dysentery, cholera, plague, syphilis, tuberculosis;
Bacterial toxins: botulism, staphylococcal food poisoning;
Viruses: acquired immune deficiency syndrome (AIDS), hepatitis A, B and C, influenza, measles, common cold;
Rickettsiae: Rocky Mountain spotted fever, typhus fever;
Parasites: malaria, hookworm, African sleeping sickness;
Fungi: histoplasmosis, ringworm, athlete’s foot.Some illnesses may be caused by many agents. For example, infection with many different respiratory viruses can result in a common cold, and infectious diarrhea can be caused by many bacteria and viruses. Other diseases, such as tuberculosis or polio, occur only after infection with the specific infectious agent.
PREVENTION OF COMMUNICABLE DISEASES
Preventing communicable disease requires understanding the relationship between the agent with its reservoir, the susceptible host, and the route of transmission. To find ways to break the chain of disease transmission communicable diseases are prevented by:
increasing host resistance (through vaccinations);
modifying the environment (to eliminate reservoirs or to interrupt transmission);
inactivating the infectious agent.
Seagoing persons should be appropriately vaccinated against all diseases traditionally occurring during childhood (diphtheria, tetanus, poliomyelitis, measles, mumps, rubella, and chicken pox) and should consider vaccination to prevent hepatitis A and B. Though vaccines have reduced the occurrence of many of these diseases worldwide, susceptible travelers may still acquire these diseases.
Diphtheria and tetanus boosters are recommended every 10 years. Adults born after1957 should either have received two doses of MMR (measles, mumps, and rubell acontaining vaccine) or show evidence of immunity when their blood is tested for antibodies against these viruses. Vaccination against chicken pox is only necessary if there is no history of childhood infection. Vaccination against both hepatitis A and B and an inactivated poliomyelitis vaccine booster should be considered for adults who plan to travel and work in areas where these diseases are more common.
Hepatitis A is contacted by the oral fecal route, such as from contaminated food or water. Hepatitis B may be acquired by direct or indirect contact with body fluids from an infected person. Certain personal practices, such as avoiding contaminated needles (e.g., tattoo and syringe needles) and using condoms, help to prevent infection.
Travelers to endemic areas should consider vaccination for hepatitis A, typhoid fever,and cholera. Hepatitis A and/or typhoid vaccines are indicated for persons who travel regularly to less-developed countries and who anticipate eating locally prepared foods or drinking water. Travelers to less-developed countries are advised to avoid eating uncooked food, especially fish and shellfish, and to peel fruits themselves to minimize the risk of acquiring typhoid fever, cholera, hepatitis A, and other gastrointestinal diseases. Currently, no country or territory requires cholera
vaccination as a condition for entry. Local authorities, however, may require documentation of cholera vaccination when coming from endemic or epidemic areas;in such cases, a single dose of vaccine is sufficient to satisfy local requirements.
Certain diseases transmitted by mosquitos, such as yellow fever and Japanese encephalitis (a disease that occurs throughout eastern and southern Asia) may be prevented through vaccination and by avoiding mosquito bites by wearing appropriate clothing and using repellents and mosquito netting. Yellow fever vaccination is required at 10-year intervals for travel to many tropical American and African countries. Animal-borne disease such as plague and rabies may be
prevented by vaccine and avoidance of unknown animals. Meningococcal disease may be prevented with vaccination when traveling to regions of higher risk: the sub-Saharan east-west belt of Africa, the Middle East, and the Asian subcontinent.
Every seaman should keep with his or her passport and other papers, written evidence of the vaccines and prophylaxis received. The World Health Organization(WHO) publishes vaccine cards, which are recommended in order to keep an accurate record of all vaccinations (Fig 2-1). Up-to-date records will prevent repeated and unnecessary vaccinations when entering an infected port or one that requires vaccination documents. Some ports may require documentation of prior vaccination for yellow fever or cholera when traveling from areas with high disease activity.
NOTE: An International Certificate of Vaccination must be complete in every detail; if incomplete or inaccurate, it is not valid. This certificate is revised periodically, but older forms are usually acceptable. A copy of the International Certificate of Vaccination, (PHS-731) is available from most health departments and many medical practitioners.
Although some vaccinations require single dose administration, others require two or three doses given over a period of 2 weeks to 6 months. Without adequate planning, this may present a problem to merchant seamen. If no medical officer is available and qualified to administer vaccinations, it is recommended that seamen arrange for multi-dose vaccinations during lay overs ashore. Seamen should consult medical authorities at least 6 weeks before departure to obtain current health information on the countries that will be visited. Information on requirements and recommendations for the international traveler is Reservoir Eradication Exposure to infection can be prevented by eradicating the reservoir of infection,
closing the portals of exit from the sources, and eliminating the modes of transmission. For example, outbreaks of bubonic plague have been controlled by destroying rats and other rodents that can carry the plague bacteria. Providing proper environmental controls of air, dust, and dirt (which may harbor infectious agents) aboard ship may decrease the risk of communicable diseases among crew.Similarly, insect control may eliminate reservoirs for certain vector-borne diseases.
Interrupting Disease Transmission
Disease transmission can often be interrupted by the following:
rapid diagnosis and treatment of infectious diseases; isolation of patients from other crew members (when appropriate)
chemoprophylaxis before exposure (i.e. medication prophylaxis to prevent malaria);
practicing good personal hygiene (i.e. using insect repellents and wearing appropriate clothing).
Inactivating Infectious Agent
Infectious agents can be inactivated to reduce the spread of disease. Chemical methods include chlorinating water supplies and sewage effluents. Proper disinfection and maintenance of potable water systems can prevent waterborne diseases caused by bacteria and viruses. Disinfectants and fungicides are useful.
Physical methods for inactivating infectious agents include use of heat (proper cooking of foods) and cold (refrigeration of foods). Proper food handling, preparation,and storage help to prevent outbreaks of food borne and diarrhea diseases. These simple yet essential practices should be carried out by staff and crew members of the ship.
Personal hygiene is necessary to prevent infectious diseases. Many diseases are transmitted by the oral fecal route. Hands are often contaminated when urinating or defecating. This contamination can spread disease to the individual and to the entire crew. Regular Handwashing By Every Crew Member is critical to the health of the entire crew. If crewmembers frequently develop diarrhea, the source of contamination should be aggressively sought and corrected. Each head must be kept clean, so that handwashing is effective.
Hands should also be washed before touching food and before meals. Cigarettes can become contaminated in the same way, and spread disease. Always wash your hands before touching anything that will go into your mouth.
Food service workers should be especially cautious. They should be free of infectious disease when preparing food. Routine health screening is important.Further, they must use the recommended sanitation procedures for food purchase,storage and preparation. Handwashing is critical. They should wear gloves when handling food.
Safe Food Practices
The basics of food safety are the same on land and on sea. However, because so many people share the same environment, the same water, and the same meals on board a ship, a break in sanitation may allow diseases to spread quickly to many people or the entire crew. General principles include:
Maintain the potability (safety) of the water
Use reliable food suppliers
Keep the room temperature preparation times short
Keep raw and cooked foods entirely separate; also separate meat and fish,and fruit and vegetable prep areas; (including equipment, wiping cloths,storage areas, etc.);
Keep hot food items hot and cold food items cold;
Rapidly chill cooked foods (to 41o F/5o C or less) if they are not to be eaten immediately
Persons with diarrhea, vomiting, or open sores on their hands should not prepare food until they have fully recovered
All food handlers should wash hands frequently, especially after handling raw meat and fish
Protect food from insects, rodents, and other animals. The ship’s management should assure all food service workers understand and implement safe food practices.
Shellfish: Items containing seafood accounted for more than half of shipboard foodborne disease outbreaks investigated by CDC. Shellfish, especially scallops, accounted for four of the six seafood-related outbreaks on cruise ships. The more recent outbreaks showed that neither blanching nor marinating alone will make contaminated raw shellfish safe to eat. Steaming for at least 15 minutes may reduce the risk, if the entire product reaches a uniformly high temperature.
Crustaceans, such as lobster, crab, and shrimp, should also be cooked thoroughly.
The U.S. Food and Drug Administration (FDA) Food Code recommends cooking crustaceans such that the internal temperature reaches 145 Fahrenheit/63 Celsius for at least 15 seconds.
Eggs: Salmonella with raw eggs has long been recognized. It had been believed hat the Salmonella was due to unclean eggs or eggs contaminated internally through cracks in the shells, and that the contents of an intact egg were sterile.
However, research suggests that a worldwide epidemic of salmonella (Salmonella serotype enteritidis (SE)) is infecting the egg-forming organs of hens and is transmitted to the egg yolks as the eggs are formed inside the chickens. As a result,a perfectly normal-looking egg can harbor large numbers of SE organisms.
To prevent these outbreaks, the FDA and theCDC published the following guidelines:
Shell eggs should be maintained at an internal product temperature of 41oF/5o C or below until used;
Commercially pasteurized egg and egg products should be substituted for raw shell eggs in the preparation of uncooked, ready-to-eat menu items such as Caesar salad, uncooked hollandaise or bearnaise sauce, ice cream, etc.;
Pasteurized egg product should be substituted for shell eggs in recipes calling for pooled eggs
Eggs should be cooked to heat all parts to at least 145o F/63o C for 15 seconds or more;
Cooked eggs requiring holding before service should be held at an internal temperature of 140 F/60C or above.
The third guideline is especially important. Large outbreaks have been related to the use of bulk pooled eggs held for periods of time before cooking, or held on a steam table or buffet bar after partial cooking. Any recipe that calls for a large pool of eggs that are cracked ahead of time and held in a large container before cooking is of particular concern. A single infected egg can contaminate the entire pool. No outbreaks have been caused by pasteurized egg products.
Ground beef: While no food borne disease outbreaks aboard cruise ships have yet
implicated ground beef as the source, this item could serve as a source of infection with Escherichia coli O157:H7 if not cooked properly. The food borne bacterial organism E. coli O157:H7 is an emerging cause of food borne illness. Infection often leads to bloody diarrhea and occasionally to kidney failure and death. Most illness has been associated with eating dercooked, contaminated ground beef. E. coliO157:H7 lives in the intestines of some healthy cattle; meat can become contaminated during slaughter, and organisms can be thoroughly mixed into beef
when it is ground. Infection can be prevented by thoroughly cooking ground beef to at least 155F/68 C for at least 15 seconds, as recommended in the FDA Food.