Immunizations
Required Vaccinations
No vaccinations are required to enter this country.
Recommended Vaccinations
Routine Immunizations
Your trip is a good occasion for a reminder to keep your routine immunizations updated; more than 80% of adults in developed countries have not maintained their immunization status. The following vaccinations are recommended for your protection and to prevent the spread of infectious diseases.
Tetanus, Diphtheria, Pertussis, Measles, Mumps, Rubella, Poliomyelitis should be reviewed and updated if necessary. Note: Many of these vaccine preventable illnesses are making a resurgence due to non-vaccination, incomplete vaccination, and waning immunity. It is important to keep your routine immunization up-to-date.
Seasonal influenza vaccination is recommended for all travellers over 6 months of age, especially for children, pregnant women, persons over 65, and those with chronic health conditions such as asthma, diabetes, lung disease, heart disease, immune-suppressive disorders, and organ transplant recipients. Note: In the northern hemisphere the flu season typically runs from November to April and from April to October in the southern hemisphere. If the flu vaccine is not available at the time of departure, contact your doctor or travel health clinic regarding influenza anti-viral protection.
Pneumococcal vaccine is recommended for persons over the age of 65 and persons of any age suffering from cardiovascular disease, diabetes, renal disorders, liver diseases, sickle cell disease, asplenia, or immuno-suppressive disorders.
Public health officials have launched a media campaign to "Stop Whooping Cough" that urges adults to get vaccinated against pertussis before being around an infant. (Numbers have increased in several states: Utah, Minnesota and Oregon). For the latest information on Pertussis outbreaks please go to: ProMED-mail. Pertussis - USA: waning immunity. ProMED-mail 2013; March 16: 20130316.1590032. <www.promedmail.org>. Accessed March 18, 2013.
Measles has been reported from New York City, Massachusetts, North Carolina and Texas. For the latest information on Measles outbreaks please go to: ProMED-mail. Measles update (19). ProMED-mail 2013; May 13: 20130513.1708416. <www.promedmail.org>. Accessed May 14, 2013.
Hepatitis A
The Hepatitis A virus (HAV) is primarily transmitted from person to person via the fecal-oral route, including through contaminated water and food, such as shellfish or uncooked vegetables and fruit, prepared by infected food handlers.
The virus is present worldwide, but the level of prevalence depends on local sanitary conditions. HAV circulates widely in populations living in areas with poor hygiene infrastructure. In these areas, persons usually acquire the virus during childhood when the illness is asymptomatic (but still infective to others) or mild, and end up developing full immunity. Large outbreaks in these countries are rare. In contrast, a large number of non-immune persons are found in highly industrialized countries where community wide outbreaks can occur when proper food handling or good sanitation practices are not maintained including in daycare centres, prisons, or mass gatherings.
In many cases, the infection is asymptomatic (persons do not exhibit symptoms). Those with symptoms will usually get ill between 15 to 50 days after becoming infected. Symptoms include malaise, sudden onset of fever, nausea, abdominal pain, and jaundice after a few days. The illness can range from mild to severe lasting from one to two weeks or for several months. Severe cases can be fatal especially in older persons. Most infections are asymptomatic in children under six years of age, but infants and children can continue to shed the virus for up to six months after being infected, spreading the infection to others. Many countries are now including vaccination against Hepatitis A in their childhood vaccination schedules.
Prevention: Practice good personal hygiene, including washing your hands frequently and thoroughly, drink boiled or bottled water, eat well cooked foods, and peel your own fruits.
All non-immune persons, especially travellers, should be vaccinated. Two vaccines are available for persons over one year of age. Two doses are needed for full protection (the second dose is given 6 to 12 months after the first dose (HAVRIX) or 6 to 18 months after the first dose (VAQTA). TWINRIX is a vaccine against Hepatitis A and Hepatitis B. It is available for persons over 18 years of age. Three doses are needed for full protection. The second dose is given 1 month after the first, and the third 6 months later. For an accelerated schedule four doses are needed at 0, 7, 21, 31 days and the last dose 12 months later.
Selective Vaccinations
Hepatitis B
The Hepatitis B virus is transmitted through infected blood products, sexual intercourse, or infected items such as needles or razor blades, and may cause severe liver damage.
Vaccination is recommended for persons on working assignments in the health care field (dentists, physicians, nurses, laboratory technicians), or for those working in close contact with the local population (teachers, aid workers, missionaries), or persons foreseeing sexual relations with locals. This vaccine is often combined with the Hepatitis A vaccine and affords excellent long-term protection for both viral diseases.
Note: Due to the high rate of Hepatitis B carriers among the local indigenous populations of Alaska, vaccination is recommended for persons intending to live or work in these communities.
The recommendations for vaccinations outlined above are intended as guidelines only. Your immunization needs depend on your health status, previous immunizations received, and your travel itinerary. Seek further advice from your doctor or travel health clinic.
Health Risks
Air Pollution
Outdoor air pollution (a mix of chemicals, particulate matter, and biological materials that react with each other) contributes to breathing problems, chronic diseases, increased hospitalization, and premature mortality. Cities and rural areas around the world are affected by air pollution.
No matter where you travel, you will not be able to escape air pollution. Exposure and concentration of pollutants can affect your health. When planning your trip, consider your health status, age, destination, length of trip and season to help you mitigate the effects of air pollution.
Short term symptoms of exposure to air pollution include itchy eyes, nose and throat, wheezing, coughing, shortness of breath, chest pain, headaches, nausea, and upper respiratory infections (bronchitis and pneumonia). It also exacerbates asthma and emphysema. Long term effects include lung cancer, cardiovascular disease, chronic respiratory illness, and developing allergies. Air pollution is also associated with heart attacks and strokes.
Prevention: Comply with air pollution advisories (ask around and observe what locals are doing) and avoid strenuous activity. If you have asthma or chronic obstructive pulmonary disease (COPD), carry an inhaler, antibiotic, and oral steroid (consult your doctor to see what is best for you). It is recommended that older travellers get a physical exam that includes a stress and lung capacity test prior to departure. Newborns and young children should minimize exposure as much as possible or consider not travelling to areas with poor air quality. Ask your medical practitioner if a face mask is advisable for you.
>> For city and country air pollution levels, see the World Health Organization.
Ciguatera Fish Poisoning
Ciguatera poisoning is caused by eating fish that has been contaminated by a dinoflagellate-produced toxin. Large fish become contaminated with the toxin when they eat reef fish that feed on these small organisms. Ciguatera is the most commonly reported marine seafood toxin poisoning. Any reef fish can cause ciguatera poisoning, but species such as barracuda, moray eel, grouper, red snapper, amberjack, parrotfish, sturgeon, ulua, and sea bass are the most commonly involved. The occurrence of toxic fish is sporadic, and not all fish of a given species or from a given area will be toxic.
Travellers need to be aware of the areas where the toxin exists and of the local fish that have been associated with the toxin. Outbreaks are seasonal but can also occur after major storms. Ciguatoxin does not affect the taste or smell of fish. It cannot be destroyed by cooking, smoking, freezing or any other method of food preparation. Large fish (over 6 lbs or 13.2 kg) are more likely to contain ciguatoxin. It is recommended not to eat large reef fish, as well as not eating fish liver, intestines, heads, and roe, where the toxin is concentrated.
For more information, see Centers for Disease Control and Prevention.
Occasionally reported from Hawaii and Florida.
Coccidioidomycosis
Coccidioidomycosis, also known as 'Valley Fever', is caused by inhaling the fungal spores Coccidioides immitis and C. posadasii found in dust and soil particles in arid areas of the USA, Central America, and South America.
Travellers are at risk of Coccidioidomycosis doing outdoor activities such as camping, mountain biking and motocross, archaeological excavations as well as farming and mining which disturb the ground and generate dust clouds. Windstorms and earthquakes can also spread the fungus.
In the majority of cases, the infection is asymptomatic (persons do not exhibit symptoms). Those with symptoms get ill between 7 to 21 days after inhaling the fungi. Flu-like symptoms include fever, headache, muscle pain, dry cough, weight loss, rash, and pneumonia. In rare cases, the illness may progress to lung disease and affect the central nervous system, as well as the joints, bones and skin. The elderly and persons with chronic health conditions such as diabetes are at greater risk. Once infected, a person is immune to the disease. Treatment may include anti-fungal therapy.
Prevention: Travellers should limit exposure to outdoor dust and take dust-control measures, including driving in air-conditioned vehicles, wetting the soil before undertaking soil disrupting activities, and wearing a tight fitting dust mask that filters small particles. There is no preventive vaccine or medication against Coccidioidomycosis.
The arid areas of the Sonora Desert in Arizona, including Phoenix and Tucson, and the San Joaquin Valley of California report the highest incidence. New Mexico, western Texas, Nevada and Utah are also endemic.
Coccidioidomycosis infection is on the rise in the southwestern United States. Risk of infection is highest in dry summer months. For the latest information on coccidioidomycosis outbreaks please go to: ProMED-mail. Coccidioidomycosis (03): increased cases. ProMED-mail 2013; March 29: 20130329.1609769. <www.promedmail.org>. Accessed April 03, 2013.
Lyme Disease
Lyme Disease is caused by bacteria belonging to the genus Borrelia transmitted through the bite of infected ticks belonging to the Ixodes genus. Borrelia burgdorferi is the predominant cause of the illness in North America, and Borrelia afzelii and Borrelia garinii in Europe and Asia. Ticks get infected when they feed on deer, birds, and rodents who are reservoirs for the bacteria and spread it to humans typically by nymphs (immature ticks).
Travellers involved in outdoor activities in forested areas are at risk, including campers, hikers, and hunters. Brushing against vegetation or walking in city parks known to have infected ticks can also put a person at risk.
Lyme Disease usually progresses in three stages. One of the first symptoms (for approximately 70% to 80% of persons) is a small bump and skin rash at the site of the bite which usually goes away after 1 or 2 days. Anywhere from 3 to 30 days, the rash expands to an encircled red patch (known as Erythema migrans or Bull's Eye rash) which is warm to the touch but not painful or itchy. The rash may produce lesions. Other symptoms include fever, headache, muscle and joint pain, chills, fatigue, and swollen lymph nodes. Contact your healthcare practitioner immediately if you develop symptoms.
If untreated, the illness progresses to the second stage within days or weeks of getting infected. Symptoms include severe headaches, meningitis, swollen joints, skin lesions, heart palpitations, dizziness, persistent fatigue, sleep disturbance, as well as loss of muscle tone in the face (Bell's palsy). Some of these symptoms usually disappear within weeks or months. However, if untreated, the illness will progress to a third stage which includes arthritis and chronic pain, numbness, tingling of hands and feet, and short-term memory loss.
If treated promptly, Lyme Disease usually takes 2 to 4 weeks to cure and includes antibiotics such as doxycycline, amocicillin, or ceftriaxone.
Prevention: Travellers who engage in hiking, camping, or similar outdoor activities in wooded regions of endemic areas should take measures to prevent tick bites, including applying a DEET-containing repellent to exposed skin and permethrin spray (or solution) to clothing and gear. When hiking in wooded areas, stay in the middle of the trail and avoid tall grasses and shrubs. Wear light coloured clothing, and long shirts and pants tucked into socks. Carefully examine your clothing, gear, and pets for ticks before entering a dwelling.
Regularly check your body for ticks and promptly remove using tweezers by grasping the tick's head and mouth parts as much as possible and by pulling perpendicular from the skin. Thoroughly disinfect the bite site with soap and water or alcohol. If travelling in an endemic area, you may want to save the tick in a zip-lock bag or empty container to have it analyzed through your healthcare practitioner. There is no preventive vaccine or medication against Lyme Disease.
>> For Lyme Disease images, life cycle, and distribution maps, see Infection Landscapes.
Lyme disease has been reported from all continental states, except Alaska. High risk states are Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, and Wisconsin. States with moderate to high risk include District of Columbia, Illinois, Indiana, Iowa, North Dakota, and West Virginia.
A new report finds cases of Lyme disease in Wisconsin have nearly doubled in the past couple of years. Increased incidence has been noted in the states of Oregon and Washington as well (Ticks usually become active in April). The incidence of Lyme disease has increased in the USA. Latitude and population density were correlated with higher increases, with states in the north seeing increases and southern states seeing stable or declining rates. For the latest information on Lyme disease outbreaks please go to: to: ProMED-mail. Lyme disease - USA (02): increased incidence. ProMED-mail 2013; April 17: 20130417.1651205. <www.promedmail.org>. Accessed April 17, 2013.
Sexually Transmitted Infections
Avoid unprotected sexual contact. If you are going to have sex with a stranger, use latex or polyurethane condoms consistently and correctly. Bring your own condoms from home.
Some countries continue to have entry restrictions for travellers with HIV / AIDS. See NAM aidsmap for details on this country.
West Nile Virus
The West Nile Virus (WNV) belongs to the Flaviviridae family. It is transmitted to humans and animals through the bite of infected Culex mosquitoes which are active from dusk to dawn. The mosquitoes acquire the virus from feeding on infected birds. Human to human transmission does not occur. The virus is commonly found in North America, Europe, Africa, the Middle East, and West Asia.
Risk to travellers is low. However, there is greater risk for long term travellers visiting endemic areas. Older persons and those with immuno-compromised systems or pre-existing health conditions are also at increased risk of contracting West Nile Virus.
The majority of cases are asymptomatic (persons do not exhibit symptoms). Approximately 1 in 5 people have symptoms which include a fever, headaches, nausea, vomiting, muscle aches, including a rash (typically on the torso) and swollen glands. Symptoms usually last a few days to several weeks. More severe symptoms of the illness include high fever, disorientation, tremors, convulsions, paralysis, and coma that can cause neurological damage. Fatalities can occur. The focus for hospitalized patients is supportive treatment of symptoms and prevention of secondary infections.
Prevention: Travellers should take measures to prevent mosquito bites both indoors and outdoors, especially during the daytime. Insect-bite prevention measures include applying a DEET-containing repellent to exposed skin, applying permethrin spray (or solution) to clothing and gear, wearing long sleeves and pants, getting rid of water containers around dwellings and ensuring that door and window screens work properly. There is no preventive medication or vaccine against West Nile Virus for humans.
>> For West Nile Virus images, life cycle, and distribution maps, see Infection Landscapes.
Most cases of West Nile Virus occur during the mid- to late-summer and fall.West Nile virus has become endemic in the continental USA following its introduction in 1999.
The US has reported its first human case of West Nile virus in Mississippi. For the latest information on West Nile virus outbreaks please go to: ProMED-mail. West Nile virus - USA: (MS). ProMED-mail 2013; April 09: 20130409.1633975. <www.promedmail.org>. Accessed April 09, 2013.
LOW HEALTH RISKS TO TRAVELLERS
Dengue
Dengue is a viral infection caused by four types of viruses (DENV) belonging to the Flavivirdae family. The viruses are transmitted through the bite of infected Aëdes aegypti and A. albopictus female mosquitoes that feed both indoors and outdoors during the daytime (from dawn to dusk). Dengue is present in tropical and subtropical areas of Central America, South America, Africa, Asia, and Oceania. It's found predominantly in urban and suburban settings and higher rates of transmission occur during rainy seasons.
All travellers are at risk during epidemics. Long-term travellers and aid or missionary workers going to areas where Dengue is endemic are at higher risk.
In some cases, Dengue infection is asymptomatic (persons do not exhibit symptoms). Those with symptoms get ill between 4 to 7 days after the bite. The infection is characterized by flu-like symptoms which include a sudden high fever coming in separate waves, pain behind the eyes, muscle, joint, and bone pain, severe headache, and a skin rash characterized by bright red spots.
The illness may progress to Dengue Hemorrhagic Fever (DHF). Symptoms include severe abdominal pain, vomiting, diarrhea, convulsions, bruising, and uncontrolled bleeding. High fever can last from 2 to 7 days. Complications can lead to circulatory system failure and shock, and can be fatal. Exposure to one type of Dengue virus does not provide immunity to the other three types. Contracting Dengue more than once increases the risk of developing Dengue Hemorrhagic Fever.
Prevention: Travellers should take measures to prevent mosquito bites during the daytime. Insect-bite prevention measures include applying a DEET-containing repellent to exposed skin, applying permethrin spray (or solution) to clothing and gear, wearing long sleeves and pants, getting rid of water containers around dwellings and ensuring that door and window screens work properly. There is currently no preventive medication or vaccine against Dengue.
There is risk of Dengue in Miami-Dade County and Palm Beach County.
Hantavirus
Hantavirus Pulmonary Syndrome (HPS) is a rare infection caused by viruses belonging to the Bunyaviridae family. It is a zoonosis (an animal disease that can spread to humans) transmitted by infected deer mice and other wild rodents through their urine, feces, and saliva. HPS viruses are found in the Americas, while related viruses causing Hemorrhagic Fever with Renal Syndrome (HFRS) exist worldwide.
Travellers can get ill when they breath aerosols (air droplets) contaminated with the virus. Campers, hikers, and cave explorers are at risk if they come into direct contact with infected rodents or their nesting areas. HPS and HFRS are also occupational hazards for trades workers (plumbers, electricians), pest control workers, and wildlife researchers.
Hantavirus Pulmonary Syndrome symptoms usually appear 2-4 weeks after infection and include fever, backache, muscle aches especially in the thighs, hips, and shoulders), general weakness and fatigue. Some people may also experience abdominal pain, diarrhea, and vomiting. The disease may progress to more severe symptoms, usually 10 days later, with difficulty breathing, shortness of breath, and coughing.
Hemorrhagic Fever with Renal Syndrome symptoms usually appear 1-2 weeks after infection and are much more severe than in patients with Hantavirus Pulmonary Syndrome. Infected persons experience fever, intense headaches, back and abdominal pain, chills, nausea, blurred vision, red eyes, or a rash. The disease may progress into uncontrolled bleeding, kidney failure, and shock. If untreated, both HPS and HFRS can be fatal.
Prevention: Travellers should avoid direct contact with wild rodents by choosing camp sites that are open and dry, do not rest on grassland or haystacks, and remove food sources that may attract rodent activity. Rodent control in and around the home remains the best way to prevent infection. There is no preventive medication or vaccine against Hantavirus.
>> For Hantavirus images, life cycle, and distribution maps, see Infection Landscapes.
Leptospirosis
Leptospirosis is caused by bacteria belonging to the genus Leptospira. It is a zoonosis (an animal disease that can spread to humans) affecting domestic and wild animals such as cattle, dogs, cats, pigs, and rodents. Humans can become sick when they come into contact with water, food, soil, and mud contaminated with the urine of infected animals. The bacteria can enter through skin abrasions and mucous membranes of the mouth, eyes, and nose. Leptospirosis occurs worldwide, but is endemic (usually seasonally) in tropical and subtropical areas with poor sanitation and in agricultural areas with livestock operations or rodent infestations. Outbreaks can also occur after storms, heavy rainfalls, or floods.
Travellers involved in adventure travel or outdoor activities such as swimming, canoeing, whitewater rafting, kayaking, or camping are at risk. Visiting farms, rice paddies, or sugar cane fields can also increase risk of exposure. Leptospirosis is an occupational hazard for farmers, veterinarians, rescue workers and military personnel.
The infection is characterized by flu-like symptoms which can appear anywhere from 2 to 30 days (usually 7 to 10 days) after being infected. Symptoms include sudden fever, headache, muscle pain, chills, red itchy eyes, difficulty urinating, a skin rash, nausea, vomiting, and diarrhea. A second, more severe, phase of the illness – also known as Weil's disease – may progress to kidney or liver failure, jaundice, cardiac failure, meningitis (inflammation of the brain), and respiratory failure. Treatment usually includes antibiotics. Human to human transmission of leptospires bacteria is rare.
Prevention: Avoid swimming or wading in water potentially contaminated with urine, including in canals, swamps, lakes, and rivers. If this cannot be prevented, wear protective clothing and footwear when coming into contact with potentially infected water, soil, or animals. Outdoor sports travellers and persons with occupational risk may want to consult their healthcare provider about taking preventive medication to avoid infection. In North America, there is currently no commercially available vaccine against Leptospirosis.
Has been known to occur in Hawaii.
Plague
Plague is mostly a zoonotic bacterial infection of rodents caused by Yersinia pestis and is transmitted to humans and animals through bites by infected fleas. Person to person infection can occur through respiratory secretions. Rapid diagnosis and treatment with antibiotics is imperative since untreated infection has a high mortality rate. The Plague vaccine is no longer commercially available.
Most travellers are not at risk from the Plague, however, persons who may be occupationally exposed to wild rodents (anthropologists, archeologists, geologists, spelunkers) or hunters, hikers, and campers in endemic areas must avoid contact with rodents.
Known areas of risk are present in remote areas of Arizona (northeastern part), California (all areas bordering Nevada from Lake Tahoe to the Mexican border), Colorado (the central part of the state with scattered areas in the south borderng New Mexico), Idaho (areas bordering the southern part of western Montana and areas bordering Wyoming), Montana (southwest part), Nevada (northeastern part), New Mexico (the entire state), Oregon (central areas and southeastern parts bordering California and Nevada), Texas (areas extending from the city of Lubbock to the border with New Mexico), Utah (scattered areas in the central and southern parts of the state), Washington (central and eastern parts of the state), Wyoming (the southern half and in the north around the Big Horn Mountains).
A second person became infected with the plague in Oregon. For the latest information on Plague outbreaks please go to: ProMED-mail. Plague - USA (05): (OR), 2nd case. ProMED-mail 2012; September 16: 20120916.1296380. <www.promedmail.org>. Accessed September 17, 2012.
Rocky Mountain Spotted Fever
Rocky Mountain Spotted Fever (RMSF) is a tick-borne rickettsial illness. It is caused by the bacteria Rickettsia rickettsii. The organism that causes RMSF is transmitted by the bite of an infected tick. The American dog tick (Dermacentor variabilis) and Rocky Mountain wood tick (Dermacentor andersoni) are the primary vectors which transmit RMSF bacteria. The brown dog tick Rhipicephalus sanguineus has also been implicated as a vector as well as the tick Amblyomma cajennense.
Travellers to endemic areas who have exposure to tick habitats could be at risk for Rocky Mountain Spotted Fever. Tick-bite prevention measures include applying DEET-containing repellent to exposed skin and permethrin spray or solution to clothing and gear.
Rocky Mountain Spotted fever is endemic in the United States and occurs mostly in the southeast.
Food and Water Safety
Water is potable and safe to drink.
Milk is pasteurized and safe to drink. Butter, cheese, yoghurt, and ice cream are safe.
Local meat, poultry, seafood, vegetables, and fruits are safe to eat.
Gastro-intestinal infections are the most common illnesses affecting travellers and can occur in any country you are visiting. Proper food handling, drinking purified water, and maintaining good personal hygiene are key to prevention. Below is a summary of the agents causing gastro-intestinal illnesses.
Bacterial Contamination
It is estimated that about 85% of traveller’s diarrhea is caused by bacteria of which the following are the most important agents:
Enterotoxigenic Escherichia coli (ETEC) and Enteroaggregative Escherichia coli (EAEC) account for most cases of traveller’s diarrhea associated with contaminated food and water world wide. They are the cause of large outbreaks in developed countries when food and water sanitation have not been properly maintained. Symptoms include watery stools, abdominal cramps, and possible vomiting lasting three to seven days.
Campylobacter jejuni is more prevalent in developing countries and is associated with contaminated water, undercooked food, and unpasteurized milk. Symptoms include diarrhea, abdominal cramps, and fever lasting from two to ten days.
Salmonella enteritidis is associated with contaminated eggs, poultry, milk, fruits, and uncooked vegetables. Symptoms include diarrhea, vomiting, abdominal cramps, and fever lasting from four to seven days. Infected persons can become asymptomatic carriers and shed the bacteria for years, becoming the source of infection for others through poor hygiene practices.
Shigellosis is a human infection caused by one of four species and transmitted by fecal-oral route due to unsanitary conditions, contaminated food and water, and overcrowded living conditions. Symptoms include diarrhea, abdominal cramps, fever, and may cause bloody diarrhea and mucous lasting four to seven days.
Vibrio cholera is associated with contaminated water, raw and undercooked seafood. Cholera infection in travellers is rare; symptoms include watery diarrhea and vomiting lasting three to seven days, but can lead to severe dehydration and death in undernourished persons. Vibrio parahaemolyticus is also related to the consumption of raw and undercooked seafood. Vibrio vulnificus is associated with contaminated shellfish and raw oysters in particular, and has caused septicemia in persons with liver disorders.
Viral Contamination
Gastro-intestinal infections caused by viruses account for about 5%. The main agents are Norovirus, associated with outbreaks at large gatherings and on cruise ships, and Rotavirus, which is more prevalent in developing countries. Symptoms include vomiting, diarrhea, fever, and myalgia lasting 12 to 60 hours.
Protozoal Contamination
Gastro-intestinal infections with protozoa account for about 10% of traveller’s diarrhea, but may cause prolonged illnesses (lasting weeks) and cause serious complications if not diagnosed in a timely manner.
Giardia lamblia (Giardiasis) and Entamoeba hystolytica (Amebiasis) are the most important agents in this category and both infections are acquired through contaminated food and water, as well as person to person transmission due to poor hygiene practices. Cryptosporidium and Cyclospora cayetanensis are implicated with contaminated food, water, and fresh produce (berries).
Toxins Causing Food Poisoning
Clostridium perfringens is the most important agent causing food poisoning in developed countries. The spores of the bacterium germinate on cooked food that is cooled and stored at room temperature over a prolonged period of time. After ingestion, the spores produce an enterotoxin in the small intestine causing abdominal pain, diarrhea, and vomiting. Foods implicated are meats and poultry.
Staphylococcus aureus enterotoxins are spread by unsanitary practices of infected persons. The foods implicated are custards, creamy desserts, meats, and salads.
Clostridium botulinum bacteria produce a very potent toxin. It is associated with improperly canned food, lightly preserved vegetables, salted fish, and meats. Symptoms include nausea, vomiting, and neurological symptoms such as blurred and double vision, paralysis of respiratory and motor muscles that may progress rapidly.
Seafood Poisoning
Fish and shellfish can be contaminated with the toxins produced by marine micro-organisms called dinoflagellates found in all oceans, especially in coral reef areas. Larger fish have usually more toxins accumulated in the skin, musculature, and organs, as these toxins are passed up through the food chain. The toxins are not destroyed through cooking, smoking, or freezing, they are odorless and tasteless, and do not alter the appearance of the fish.
Ciguatera Fish poisoning is the most common illness in this category. The most affected fish are amberjack, barracuda, grouper, kahala, parrotfish, sea bass, red snapper, surgeon fish, ulua. Symptoms usually appear within a few hours but can be delayed for a day or more and include nausea, vomiting diarrhea, muscle pain, itchiness, dizziness and temperature reversal (hot feels cold and cold feels hot). Symptoms can last for months. Persons who had a previous episode of ciguatera fish poisoning should avoid a second exposure as symptoms will be more severe. Prevention: Avoid large fish (more than 2.5 to 3 kilos [6 lbs]) or fillet of large fish, avoid head, roe, intestines and liver where the toxin is more concentrated.
Scombroid poisoning is the result of improper handling and refrigeration of fish containing high levels of natural occurring histidine (amino acid in protein). Contamination with bacteria will convert histidine to histamine-causing symptoms similar to allergic reactions, which occur very rapidly and include headache, abdominal cramps, diarrhea, itching, flushed face, and paralysis may occur. Scombroid poisoning occurs worldwide and affects fish from the Scombridae family: yellow tuna, mackerel, skipjack, and bonito. It can also affect other species such as herring, bluefish, sardine, anchovy, amberjack, and mahi-mahi. Prevention: Proper handling and immediate refrigeration of catch.
Shellfish poisoning is associated with the algal blooms (red tides) occurring in temperate and tropical areas. Shellfish – oysters, clams, cockles, mussels, crabs, lobsters – filter or ingest toxins produced by dinoflagellates micro-organisms. Each different toxin produces characteristic symptoms:
- Symptoms of diarrheic shellfish poisoning occur about 30 minutes to hours after ingestion and include nausea, vomiting, and diarrhea. Recovery occurs within two to three days.
- Symptoms of neurotoxic shellfish poisoning appear rapidly after ingestion and include tingling of mouth, arms and legs, stomach upset, and severe muscle pain. Recovery occurs within two to three days.
- Symptoms of paralytic shellfish poisoning appear rapidly after ingestion and include nausea, numbness of face arms and legs, headache, loss of coordination and dizziness, in severe cases respiratory failure and paralysis may lead to death.
- Symptoms of amnesic shellfish poisoning occur within 24 hours of ingestion and include vomiting, diarrhea, and disorientation. Permanent short-term memory loss has been observed, and in severe cases seizures, paralysis, and death may occur. Persons with kidney disease are especially vulnerable.
Puffer Fish poisoning (Fugu) is caused by a tetrodotoxin accumulating mainly in the liver, intestines and ovaries of puffer fish, ocean sunfish, globe fish, and porcupine fish. Symptoms appear between six and 20 hours and include profuse sweating, salivation, headache, hypothermia, and neurological symptoms of paralysis and respiratory failure. The mortality rate is very high.
