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The Hippocratic concept of health and disease stressed the relation between man and his environment. Human beings have been traveling since the most ancient times. They travelled for exploration, trade, conquest and to spread religion. During those journeys through unfamiliar terrain and uncharted seas, wrath of weather, terrain, infections and environmental diseases caused considerable mortality and morbidity amongst the travelers. Not only travelers risked their own health and life, they were also responsible for translocation of communicable diseases from one continent to another. During middle-ages Plague spread from Asia to Europe through travelers. Syphilis was imported to Europe from Americas by the returning explorers. Today the speed of travel has become very fast, making it possible to reach any part of the globe within a day. Fast speed of travel though convenient, can also facilitate the spread of infection to the entire globe within a short time as happened in 2009 in case of Influenza A(H1N1) infection, within two months of occurrence of first few cases in Mexico, disease assumed pandemic proportion . Travel has been identified as one of the six key contributory factors for disease emergence .
Every year millions of people travel from one country to another and a larger number within one's own country. From USA and Canada more than 10 million people travel to developing countries every year. World Travel and Tourism Council has marked India as the world's fastest growing market for tourism. Large numbers of foreigners visit India every year for holiday, work and adventure tourism. In 2009 around 5.11 million foreigners visited our country. With the improvement in resources and facilities, more Indians are traveling from one place to another, within the country. With travel, comes the potential for exposure to conditions and diseases that are vastly different from those encountered in a traveler's home country or region. The risk increases as one travels from a sheltered environment of a developed country to a developing country. It has been seen that 56 million visits abroad were made by UK citizens every year, out of which 8% were to developing countries. The risk of illness to which they are exposed is 600 fold in Mexico and 1835 fold in Indian subcontinent as compared to risk in visiting any other European country .
Travel to India exposes the traveler to various health problems caused by tropical infections like malaria, typhoid, dengue, traveler's diarrhea, illnesses due to environmental conditions (altitude and climate) and accidents depending on the season of travel and areas visited. Problems of high altitude and desert are of special relevance.
Travel Medicine (TM) (Emporiatrics) has emerged as a specialty during last three decades. TM helps to protect the traveler against the risk of potentially dangerous diseases and to educate the traveler on ways to stay healthy. Key element of travel medicine is preparation of the traveler before departure to any destination and the advice should be tailored to that particular destination. There is a need to understand travel medicine with special reference to our country. It also depends on the duration of stay, type of stay, mode of travel (road, air, train, sea, foot, cycle or boat), purpose of visit and the areas to be visited. The pre travel evaluation is an opportunity to review the traveler's health history (including immunizations), specific itinerary, and then to formulate customized recommendations for him/her based on the above requirements [3, 4].
Addressing the traveler's need for vaccines for preventable diseases, on a given trip constitutes only one of the objectives for the pre-travel clinic visit. Advice on the prevention of diseases for which there are no vaccines, health problems resulting from environmental conditions and hazards, accidents and injuries, and advice for emergency self-care in remote areas, are additional important considerations. Travelers visiting primarily urban tourist areas have a lower risk for exposure to contaminated food or water. In contrast, travelers who explore beyond the usual tourist routes or who spend extended periods of time in small villages or rural areas are at greater risk of acquiring infectious diseases because of exposure to potentially contaminated water and food. Consequently, additional vaccines, booster doses of childhood vaccines or other prophylaxis are recommended for such travelers. Travelers at the extremes of age (young children and the elderly), pregnant women, and immunocompromised (e.g., HIV-infected) persons are particularly vulnerable to certain infectious diseases. Importance of specialised travel clinics has been highlighted to reduce the incidence of illness among travelers visiting high risk areas for malaria and viral hepatitis A . Pre travel consultation should ideally be sought 4-8 weeks before journey and can also be used as an occasion to educate the traveler about the overall preventive health.
To have a correct appraisal regarding the health needs of the travelers / tourists from India and other countries it is essential for health care workers to know the followingÂ [6-8].
(a) Health status of traveler (extremes of age, pregnant women, chronic diseases, medication, health concerns in the place to be visited).
(b) Traveler's destination (Disease profile of the country).
(c) Mode of transport.
(d) Specific Itinerary (malaria may be confined to some areas).
(e) Accommodation - five star or adventurous.
(f) Duration of travel (long duration travelers may require different prophylactic regimen for malaria).
(g) Purpose of travel.
(h) Weather / climate during the visit.
(i) Activities - jungle trekking, water sports, adventure.
(j) Urban or rural travel.
(k) Immunization status of the traveler and specific immunization / preventive measures recommended by the local authorities.
(l) Nearest health facility for treatment and the channel of evacuation, and availability of health insurance.
TYPES OF TRAVELERS
Reasons for travel within India by both Indian and foreign visitors are varied and a brief description of important ones will help in understanding the health needs of the traveler. The following merits attention.
Pilgrimage and Festival Travelers Hinduism, Buddhism and Sikhism have originated on the Indian soil. India has large number of shrines of major religions which attract devotees from all over the world. Many holy places are located in remote and high altitude areas of Jammu Kashmir, Himachal Pradesh and Uttarakhand. Every year many festivals are celebrated and numerous fairs ("Melas") are organized at religious places throughout the country. Devotees throng these places unmindful of unfavourable weather and terrain, overcrowding and unsanitary living conditions. Depending on the season and place they are exposed to adverse effects of extreme climatic conditions, infections and accidents.
(b) Holiday Travelers Large population from the south visits the cities and religious places in North and high altitude areas during summer. An unprepared traveler is likely to get exposed to both tropical diseases and vagaries of weather and altitude.
(c) Education, Work and Health Tours Educational tours and excursions usually take place in summer and rainy seasons to many places including mountainous and high altitude areas to which the traveler is not used to or acclimatized. Thus they get exposed to infectious diseases endemic in that area and also weather and altitude related illnesses. Injuries due to accidents are not uncommon in such travels and tours. Many patients travel to other cities and states for more affordable health care. Their conditions may get worsened, as adequate health care facilities are not available en route.
(d) Adventure Travelers Many tourists from our country and abroad visit hilly regions of India for mountaineering, trekking, skiing, river rafting, paragliding, camping and wind surfing. As the traveler will be undergoing rigorous activity and will be exposed to hazardous terrain and poor sanitation, they need to be guided on the necessity of immediate first aid and arrangements for evacuation to the nearest medical facility.
A large number of travelers from USA and European countries visit India. They face different hygiene standards and are exposed to locally endemic diseases to which they are not immune. The immigrants from developing to developed countries in Europe and USA, who travel back to their native country for purpose of visiting their friends and relatives (VFRs), are considered at higher risk of developing diseases like malaria and typhoid during their travel . They have to observe all protective measures and may have to take chemoprophylaxis for diseases like malaria. Some diseases may manifest on their return to home country where medical personnel may not be familiar with the manifestations of tropical diseases endemic in our country. This risk needs to be identified and travelers have to be educated during pre-travel evaluation and on their return to their country. Medical tourism to India is also gaining popularity among Westerners who are attracted to availability of low cost treatment and medical expertise in our country.
HEALTH RISKS TO TRAVELERS
There are four major components of health threat to travelers in India viz., arthropod borne diseases, diarrhoeal diseases, effects of weather (heat and cold) and altitude, and that due to accidents. One should also keep in mind the aggravation of preexisting illnesses. Principal causes of death are usually road traffic accidents, drowning and exacerbation of chronic diseases. We shall outline the prevalence of some of the common diseases area wise and their major manifestations. The reader is advised to refer to standard textbooks available on the subject for detailed information on individual diseases.
Arthropod Borne Diseases in Travelers
Arthropods are responsible for transmission of innumerable diseases. List of arthropod borne diseases in India is as per Table 1 [1, 9].
Malaria Malaria, a major risk to travelers, is a serious, but usually preventable infection that can be fatal. About 25000 travelers from industrialized countries acquire malaria every year out which 150 die . This disease is caused by sporozoan parasites of the genus Plasmodium and transmitted to man by certain species of infected, female anopheline mosquitoes. In most of the states the maximum transmission is during the period July to November but can occur throughout the year. Transmission of malaria stops above the heights of 2000 m. There are four species: P. vivax, P. falciparum, P. malariae, and P. ovale, but only the first two are common in India. A typical paroxysm has an initial short 'cold' stage of shivering, followed by the long 'hot' stage when temperature rapidly increases, and finally the 'wet' stage when profuse sweating brings down the temperature. The periodicity, duration and severity of paroxysms depend upon the species of plasmodium. The two important clinical types of malaria are the benign tertian (vivax) and the malignant tertian (falciparum); daily (quotidian) fever is more common with the mixed infection. Persons who are partially immune or who have been taking prophylactic drugs may show an atypical clinical picture. In India falciparum malaria resistant to chloroquine is widespread as such all-serious malaria infection should be treated as resistant cases to avoid mortality [7, 11].
All non-immune travelers are at risk for this infection. In addition, in semi immune population, poor compliance with preventive measures and prophylactic drug regimen increase the risk of infection. Several recent studies indicate that fewer than 50% of travelers adhere to basic recommendations for malaria prevention. Keys to the prevention of malaria include both personal protective measures against mosquito bites, especially between dusk and dawn, and malaria chemoprophylaxis . Travelers to malaria-risk areas, including infants, children, and former residents of the Indian subcontinent, should observe all the above precautions. Persons residing within India and entering highly endemic zones and areas harbouring drug resistant parasites should take chemoprophylaxis (either (a) or (b) of under mentioned regimens), besides observing all the preventive measures. The approach to malaria prevention can be summarized as follows:
(a) Avoid being bitten by mosquitoes, especially between dusk and dawn (use insect repellents, bed nets, wearing of full sleeve shirts after dusk and screened sleeping accommodation).
(b) Take antimalarial drugs (chemoprophylaxis) to suppress infection.
(c) Immediately seek medical help for diagnosis and treatment if fever develops one week or more after entering or up to 3 months of departure from a risk area . Although P vivax and P ovale can remain dormant in liver for up to one year or longer and cause fever even after 3 months of return from risk area.
Chemoprophylaxis Due to widespread resistance of P. Falciparum to chloroquine and sulfadoxine-pyrimethamine, use of these drugs for chemoprophylaxis is not recommended in India. One of the following three regimens is recommended for travelers [7, 11].
Doxycycline: is useful for short term chemoprophylaxis of less than six weeks duration. It is to be given 100 mg orally once a day, to be started 1-2 days before travel to malaria endemic areas and continued for four weeks after leaving such areas. It is contraindicated in pregnant women and children below 8 years.
Mefloquine: It is useful for long term prophylaxis and is to be given as one tablet of 250 mg salt orally, once a week in adults, to be started 2 weeks before travel to endemic areas and to be continued for 4 weeks after leaving such areas. Although not totally safe, it can be used in pregnancy if exposure is unavoidable in high risk areas. It is contraindicated in patients with certain psychiatric conditions, seizures and cardiac conduction abnormalities.
Atovaquone-proguanil: 1 tablet (250 mg atovaquone and 100 mg proguanil) orally once a day, to be taken 1-2 days before commencing travel and continued for 7 day after leaving such areas.
Chloroquine and proguanil combination although safe in pregnancy offers only limited protection against highly resistant P falciparum .
Filariasis The term lymphatic filariasis is given to describe the disease produced by Wuchereria bancrofti and Brugya malayi . Both these infections are endemic in India. This disease is prevalent in almost all the states except those in the western part of the country. The endemic areas are Uttar Pradesh (UP), Bihar, Odisha, Tamil Nadu, Andhra Pradesh, South Kanara District of Karnataka, Kerala, and Maharashtra states. The largest single endemic focus of B. malayi infection is along the coast of Kerala. This disease is rarely diagnosed in a foreign traveler on return to their homeland. However necessary precautionary measures to prevent mosquito bite should be undertaken.
In the acute stage of infection, symptoms are related to allergic inflammatory reactions to adult worms in the lymphatics and include recurrent swelling and tenderness of the genital organs and extremities, fever with chills, malaise, and headaches. After many years of infection, chronic elephantiasis of the limb or scrotum can occur, but it is virtually unheard of for an expatriate to develop these gross deformities. Eosinophilia in the range of 1000 to 2500/ mm3 or higher is a prominent characteristic in the acute stage of infection, but eosinophils may well be normal in chronic infections. Treatment of all species of blood filariae is with diethylcarbamazine.
Tropical Pulmonary Eosinophilia is a disease syndrome related to occult infection with animal or human filariae and is seen mainly in India and other tropical countries. This hypersensitive immune reaction leads to pulmonary symptoms, radiologic changes, lymphadenopathy, a positive filariasis serology test, and hypereosinophilia (3000/ mm3 or greater). It responds to treatment with diethylcarbamazine (DEC). Measures for prevention and control of infection are the same as for malaria control. No chemoprophylaxis is recommended to the traveler visiting these endemic zones.
Chikungunya Chikungunya is an arbovirus and is transmitted among humans in urban areas by Aedes aegypti mosquito. It is responsible for a dengue like illness in India. Mostly seen in eastern, southeastern and central parts of India but any urban area can be affected where the vector is available. The brisk onset follows an incubation period of 2-3 days. Fever and severe arthralgia are accompanied by chills and constitutional symptoms such as headache, photophobia, conjunctival injection, anorexia and abdominal pain. Migratory polyarthritis usually affects the small joints, with lesser involvement of the larger joints. The disease was named Chikungunya ("that which bends up") first time in Tanzania because of its characteristic symptoms of pain in joints. Co-occurrence of chikungunya and Dengue has been reported from Maharashtra. Traveler should take precaution against mosquito bites and only symptomatic treatment is recommended.
Dengue Dengue has emerged as one of the most common infections associated with travel. The four Dengue viruses (DENV) are arboviruses belonging to Flavi virus group. Man is the sole reservoir of infection. The important vector species in India is an urban-dwelling Aedes aegypti mosquito, which bites during daytime mostly early in the mornings and evening before dusk. The disease is prevalent throughout India in most of the cities and towns. Eggs of mosquito are laid in any vessel that catches standing water. The growth of urban slums has provided ample breeding sites of the Aedes vectors. Eggs can be accidentally transported to other countries in used tyre shipments. New comers from non-infected locality are particularly susceptible and amongst them the disease appears with dramatic suddenness. A case is infective to mosquitoes during the first 4-5 days of the illness(maximum 12 days). The mosquito remains infective for the whole of its life span of 3 to 4 weeks after it becomes infective. Other modes of transmission of Dengue are exposure to DENV infected blood through blood transfusion, organ transplantation and nosocomial injury . Vertical transmission of Dengue from infected woman to her fetus is known. The febrile illness, characterized by severe muscle joint and bone pain and sometimes a macular rash, usually lasts 5 to 6 days and terminates abruptly. Lifelong immunity develops as a result of infection but is serotype specific; cross protection among serotypes does not occur.
Dengue Hemorrhagic Fever (DHF)/Dengue Shock syndrome It occurs almost exclusively in previously infected patients as a result of antibody-dependent enhancement and an exaggerated immune response. Thrombocytopenia is invariably present, with increased vascular permeability and haemorrhagic manifestations. Dengue shock syndrome, characterized by severe hypotension, may develop in small proportion of cases. Mortality is 40-50% without hospital care. The diagnosis of dengue fever and DHF is primarily clinical. Treatment is supportive. Expert treatment, rendered timely, can reduce the mortality to less than 1% . Personal protective measures like barrier clothing and applying mosquito repellents are helpful during outbreaks. Avoid salicylate-containing compounds.
Japanese Encephalitis Japanese encephalitis (JE) is an acute viral infection transmitted to man by infected female mosquitoes belonging to Culex vishnui complex. Both domestic pigs and wild birds serve as reservoirs of infection. Man is the accidental host. The basic cycle in India is pig-mosquito-pig. Travelers doing extensive travel in rural endemic areas, such as hiking, bicycling, and camping, as well as expatriates are at greatest risk of exposure although transmission may also occur in urban areas. JE is a public health problem in Krishna-Godavari delta, West Bengal, foothills of Arunachal Pradesh and the Brahmaputra valley in Assam, Eastern UP and Bihar. The case fatality rate is high. JE has now become an important vector borne disease, with yearly reporting of JE epidemics from UP, Bihar, Andhra Pradesh etc. Treatment is mostly symptomatic and supportive. During out break the safest method of prevention is to use mosquito net. There is an effective inactivated vaccine that should be given to high-risk groups, especially children, in inter epidemic period. The vaccine is recommended for persons staying for more than a month in rural endemic areas or if the risk of exposure is high due to involvement in activities like cycling or camping . Indigenously developed mouse brain killed vaccine is available which has to be given in three doses. Two doses are given at 7-14 days interval followed by third dose after one month. A booster dose is required after 3 years . New inactivated Vero cell culture derived JE vaccines are now available which require two doses, 4 weeks apart, for primary immunization . A new live attenuated JE-Yellow fever chimeric vaccine is also under development.
Leishmaniasis Man is the only known reservoir of infection in India. Under the common head of 'Leishmaniasis' are included at least three diseases (kala-azar, oriental sore and espundia or Mucosal Leishmaniasis), caused by what morphologically and ecologically appears to be the same protozoa .
Kala-azar (Visceral Leishmaniasis) In India the endemic potential is the heaviest in Bihar, extending eastwards through Bengal, Bangladesh to Assam, westwards through Eastern UP up-to Lucknow from where it tails off rapidly and southwards along the eastern coast through Chennai up to Tuticorin.
Kala-azar has staged a comeback particularly in Bihar and West Bengal. Incubation period varies widely from 2 weeks to 2 years; in the majority of cases it is 3 to 6 months. In case of dermal leishmaniasis the incubation period is more fixed within the limits of 2 to 4 months.
Visceral leishmaniasis is characterized by irregular fever of long duration, enlargement of the spleen and liver, anaemia and leucopenia, progressive emaciation and development of a strange, earthy greasy, dusky pigmentation of skin giving the disease its name. Co-infection with HIV leads to faster progression of visceral Leishmaniasis and these patients may present with atypical features.
Oriental Sore (Cutaneous Leishmaniasis) In India it is common in the western portions of the Indo-Gangetic plains extending eastwards up to Varanasi and westwards continuing into Pakistan. Outbreaks of oriental sore have started appearing in Rajasthan. There have been some sporadic cases from UP and some other states. The lesions are usually multiple but may be single and are invariably on the exposed parts of the body. The scalp and palms are never affected. After healing a depressed scar is left. Important preventive measures for Leishmaniasis include avoiding Sand fly bites by using insect repellents, insect nets and application of insecticide to clothing. Amphotericin B is being used as first line drug in Bihar. Lipid formulations of Amphotericin B are available and considered less toxic.
Leptospirosis Leptospirosis is an acute febrile zoonotic infection, caused by spirochaetes of genus leptospira. Rodents and dogs are the most important reservoir of infection in urban areas, while cattle, pigs, goats, voles, jackals, foxes and mongoose are the reservoir in rural areas. Serious form of leptospirosis is also called Weil's disease.
Leptospira exist in some animal species like rats without producing any disease. Such animals may shed Leptospira in urine for prolonged periods. Alkaline pH of urine facilitates growth and survival of Leptospira. The increase in adventure travel to exotic tropical locales has meant that hiking, swimming, and fishing, need to be considered as risk factors. The immediate source of infection to man is through contact with the soil contaminated with infective excreta, especially urine. Bathing in contaminated water also has given rise to outbreaks. The outbreaks may therefore occur among occupationally exposed persons (in sewers, slaughterhouses and mines) and travelers who expose themselves to the above situations. Organisms enter a new host through abrasions in the skin or through intact mucous membranes like conjunctiva, vagina and pharynx, and rarely through the intestinal mucosa. This occurs in endemic and epidemic forms in many parts of India including Andaman and Nicobar Islands. Outbreaks have been reported from Maharashtra, Delhi, Tamil Nadu, Odisha, Gujarat and Karnataka. Outbreak in and around Mumbai typically follows flooding due to heavy rains and in Odisha after cyclones. Wading through floodwaters seems to predispose to infection .
Up to 40% individuals exposed to contaminated water develop asymptomatic sub clinical infection and only a few develop symptomatic disease. In majority of symptomatic patients, mild anicteric leptospirosis occurs, while 5 to 10 % develop severe leptospirosis (Weil's disease) due to infection by L. icterohaemorrhagiae. Clinical manifestations include fever, jaundice, acute kidney failure, and haemorrhage in skin and mucus membrane and lungs. There may be aseptic meningitis, severe myalgias, myocarditis, pneumonia and shock.
Mild Leptospirosis can be treated with oral antibiotics like doxycycline, amoxicillin or ampicillin whereas severe disease requires parenteral antibiotics like penicillin, cefotaxime or ceftriaxone. A mild Jarisch-Herxheimer reaction may occur during treatment. To prevent exposure to this infection the traveler should avoid rat-infested areas, living in trenches and swimming in infected pools. Wearing of protective clothing and observing proper sanitation will help. Chemoprophylaxis with doxycycline (200 mg once weekly) or azithromycin (250 mg once or twicw a week) is effective when short-term exposure is inevitable as during flood, cyclones and adventure travel [6, 8, 9].
Rickettsioses In India various types of rickettsial infections have been reported to occur sporadically, endemically and as epidemics. Louse borne epidemic typhus, is transmitted by the body louse, is both endemic and epidemic in mountainous regions (Jammu and Kashmir) and highlands. Infection with R. prowazeckii causes severe headache, high fever and other nonspecific symptoms after an 8- to 12 day incubation period. If left untreated, mortality is high. Recovery is prolonged. Murine borne endemic typhus is caused by R. typhi transmitted from rats to the human by the rat flea (Xenopsyllacheopis). The disease ranges from mild to severe form with a mortality of 1 to 4%. Mite borne Scrub typhus is endemic in Asia. Whole of Shivalik range from Kashmir to Assam, Eastern and Western Ghats and the Vindhyachal and Satpura ranges in the central part of India the disease is endemic. Trombiculid mites transmit the causative organism, R. tsutsugamushi. The typical terrain for the mite to thrive are man made rural and urban wastelands, domestic sub-urban waste lands around the edges of moist depressions, the scrub at the outskirts of the forests and low lying patches overgrown with elephant grass inside thick forests. With treatment, mortality is low. The diagnosis is by serologic tests. Doxycycline or chloramphenicol is given for 7 to 15 days and for 48 hours after defervescence of fever. Azithromycin 500 mg OD for three days is also recommended. Treatment of louse-infested individuals can be carried out by application of 10 percent DDT, 1 percent Malathion or 1 percent lindane powder, propoxur (1%) to the person as well as his clothing .
Indian tick typhus is caused by R. conorii and is transmitted to man through the bite of hard ticks as Rhipicephalus sanguineus in Kashmir, Ixodesricinus in Almora and Haemaphysalis leachi varindica in Manipur. They are persistent bloodsuckers; while feeding they attach firmly and cannot be easily removed. The ticks are acquired by man from domestic animals such as cattle, horses and dogs. The disease is sporadic in all parts of India, particularly hilly terrain. A tick bite transmits the disease to the humans and produces eschar in the skin. Selecting a proper campsite by adventure travelers, keeping it free from animals and dogs, insecticide spray of the area, antirodent measures, and personal protective measures like wearing of proper clothing and use of repellents can prevent it. [6, 9].
Kyasanur Forest Disease (KFD) The disease was first recognized in 1957 as discrete clinical entity due to an arbovirus in the forest area (Kyasanur) in Shimoga district of Karnataka. The first report of the disease pertained to deaths of monkeys and the simultaneous occurrence of human cases with fatalities in the nearby villages. Man acquires the infection from bites of infected hard ticks during the nymphal stage. Personal protective measures include adequate clothing and use of tick repellents for most of the Rickettsioses. The repellant material used for personal protection against ticks and mites are dibutyl-phthlate (DBP), diethyltoluamide (DEET) and benzyl benzoate. These are more effective when applied to the clothing than to the skin. The effect may last for nearly six washings or four weeks, which ever is earlier. However, if it is ironed, the concentration falls below effective limits. DEET may be used for application on the exposed parts of the body to reinforce the use of protective clothing treated with DBP, when working in an uncontrolled area, or under acute emergency when application of DBP on the clothing prior to entry is impossible. Wearing of shirts with rolled down sleeves tightly buttoned at the cuffs, the lower ends of trousers tucked in socks and wearing of anklets considerably reduce the risk against ticks and mites. The immediate vicinity of a tree base should be avoided for resting, so also the green edges of a stream or irrigation channel. Before retiring at night one should take a bath and carefully search the body and clothing for presence of ticks. If a tick is found attached to the body it should be removed immediately, by making the surrounding skin taut, slipping the point of a flat needle or a scalpel under the mouth parts and then removing the mouth parts by raising the point of the needle with a minimum of tissue damage. Use of mosquito net gives some protection against soft ticks.
Fly and Water Borne Diseases (Excremental Diseases)
The housefly is a mechanical carrier of the causative organisms of diarrhoeas, dysenteries, gastroenteritis, cholera, enteric group of fevers, intestinal worms, poliomyelitis, viral hepatitis A, other entero viruses, trachoma, conjunctivitis, anthrax, and yaws. Most of the fly borne diseases are transmitted by contaminated water supply. Many helminthic infections get transmitted through this and cause disease in man. The best way to avoid the diseases is to maintain high level of sanitation. Travelers should take food only from hygienic places and should not eat food, which is cooked and kept, in the open. The water should be taken after proper boiling and / or filtration. Food and waterborne diseases are the number one cause of illness in travelers (Table 2). Traveler's diarrhoea can be caused by viruses, bacteria, or parasites, which are found throughout the region and can contaminate food or water. Infections may cause diarrhoea and vomiting (E. Coli, salmonella, cholera, and parasites), fever (typhoid fever and toxoplasmosis), or liver damage (viral hepatitis). Some of the common diseases a traveler would be exposed are mentioned below [6, 8].
Cholera It is a serious acute intestinal disease caused by Vibrio cholera (Classical or El Tor), a gram negative, comma shaped, and actively motile organism. The large deltaic area of the Ganges and Brahmaputra in Bengal is its homeland. It is also reported in Assam, Bihar, Odisha and Tamil Nadu. Both classical and El Tor biotypes cause cholera and they are divided into three serotypes-Ogawa, Inaba, and Hikojima. It can occur in many forms - sporadic, endemic, epidemic or pandemic. Classical cholera is a disease of water-borne transmission, whereas El Tor spreads by both water and food. Transmission is normally through infected drinking water, shellfish, and food contaminated by flies or on the hands of carriers. Fruits and vegetables washed with contaminated water may transmit the infection. The morbidity and mortality are greatest among the very young and very old. During fairs, floods and famines or wars and conflicts, when there are unprecedented movements of refugees, the disease assumes alarming proportions. This has a characteristic seasonal pattern, which varies from place to place. In the North and the Eastern part of India the peak of the cholera season is during the hot, dry months of April to July and ends with the monsoon. It can also occur following the monsoon rains in some parts. Fatality rates in untreated cases may exceed 30-40 percent. El Tor is more resistant than classical Vibrio, and causes carrier in 5% of infections. It survives for up to 2 weeks in fresh water and 8 weeks in salt water. Treatment should be started as rapidly as possible to reduce the risk of shock. About 80-90% of patients can be adequately treated with oral rehydration salt (ORS) solution alone. Severely ill patients are treated with intravenous fluids and electrolytes, and antibiotics which shorten the duration of diarrohea and reduce the need of rehydration fluid. Effective antibiotics are doxycycline (single dose), tetracycline, erythromycin, azithromycin and ciprofloxacin. Last two drugs can also be used in single dose.
Strict personal hygiene is vital and drinking water should come from a clean piped supply or be boiled. Routine anti-cholera vaccination at present is not helpful in the prevention and control of cholera and hence not recommended. Any traveler visiting these endemic areas for religious purpose, festivals or as tourist during the vulnerable period should observe all the personal protective measures and vaccination if advised. Traditional killed cholera vaccine meant for intramuscular use is not recommended because of low immunogenic potential and adverse effects caused by it. Two types of whole cell killed oral cholera vaccines are available, both offering sustained protection of over 50% lasting for two years in endemic setting. Both vaccines need to be administered in two doses, between 7 days and 6 weeks apart [6-8, 12].
Enteric Fever Salmonella typhi causes typhoid fever and the causal organisms for paratyphoid fevers are Salmonella paratyphi A, B, and C. Man is the only reservoir of infection. The source of infection is the faeces or urine of cases and carriers (convalescent or chronic) and spreads through contaminated water, food, milk and vegetables. This disease occurs all through the year (peak July-September). This period coincides with the rainy season and an increase in fly population. Organisms survive for over a month in ice and ice cream and up to 70 days in soil irrigated with sewage under moist winter conditions. Typhoid bacilli grow rapidly in milk without altering its taste or appearance. Vegetables grown in sewage farms or washed in contaminated water are a positive health hazard. These factors are compounded by pollution of drinking water supplies, open-air defecation and urination, low standards of food and personal hygiene. Recent data indicate that in S. typhi endemic regions, the rate of clinical typhoid amongst persons positive for human immunodeficiency virus (HIV) is 25-fold higher than HIV-negative individuals in younger age group.
The term 'enteric fever' includes both the typhoid and paratyphoid fevers. When the disease is water-borne, the incubation period tends to be longer. The disease is characterized by typical continuous fever for 3-4 weeks, relative bradycardia, with involvement of lymphoid tissues and considerable constitutional symptoms. The disease responds to antimicrobial (fluoroquinolones and third generation cephalosporins) therapy. For Nalidixic acid - resistant infection, choices are ceftriaxone, Azithromycin and high dose ciprofloxacin. Preventive measures are personal hygiene and avoiding foods likely to be infected, and use of bleaching powder and individual water sterilizing powder when going on trekking. Administration of injectable Vi capsular polysaccharide vaccine or oral live attenuated typhoid vaccine offers protection. Typhoral (oral typhoid vaccine) Ty21a is given to adults and children more than 6 years of age, in 3 doses (4 doses in US), one capsule on days 1, 3, 5 [irrespective of age, one hour before a meal with cold or lukewarm milk or water]. Protection commences two weeks after taking the last capsule and lasts for 3 years. A booster dose is recommended once every 5 years. Injectable Vi capsular typhoid vaccine (minimum age 2 years) can be given where oral vaccine is not available as per the schedule. Vaccine for paratyphoid is not available at present [7, 8].
Dracunculiasis Dracunculus medinensis (Guinea worm) is a nematode infesting the tissue of man. Infection occurs in people who drink unprotected ground water sources contaminated with infective larvae derived from Cyclops, which is the intermediate host. Between 9 and 14 months later gravid females, 70 to 120 cm long, migrate within the subcutaneous connective tissues, usually reaching extremities. The worm expels the larvae into water, when the patient enters a pond. Larvae are ingested by the Cyclops and become infective 2 weeks after ingestion. No effective drug treatment is available. Treatment with mebendazole was associated with aberrant migration of worms .Worm has to be pulled out slowly and gradually through the dermal lesion by winding it on a stick. Personal prophylaxis is by avoiding contaminated drinking water or by brief boiling or filtering through cloth. The worm has nearly been eradicated from India.
Bacillary Dysentery It is caused by Shigella group of (S. dysenteriae, S. flexneri, S. boydii, S. sonnei) gram negative non-motile organisms. These organisms do not thrive in water and chlorination readily kills them. Transmission is through faeco-oral route. Incubation period is 1 to 2 days, sometimes about a week. It is characterized by diarrhoea with blood and mucus in stools. When given early, antibiotics can shorten the duration of illness. Ciprofloxacin is the drug of choice. Other drugs shown to be effective are ceftriaxone and azithromycin. Observance of personal and domestic hygiene will help in prevention.
Amoebic Dysentery It is caused by a protozoal parasite Entamoeba histolytica. Though amoebiasis is a world problem it is more prevalent in tropical countries. The infection is acquired by ingestion of food or water contaminated by viable cysts of Entamoeba histolytica. In the intestinal tract the trophozoites are liberated from the cysts and they invade the colonic mucous membrane. Only 10% of infected individuals develop symptoms. The illness is characterized by gastrointestinal and constitutional symptoms and runs a chronic course with periodic acute exacerbations. The symptoms may develop in a traveler after he returns to his home in India or abroad. In amoebic dysentery there is diarrhoea with blood and mucus in stools as a result of heavy infection. Symptoms of amoebic colitis develop 2-6 weeks after the ingestion of cysts. Metronidazole in a dose of 500 to 750 mg thrice daily after food for 5 to 10 days is useful for all patients with amoebiasis. Tinidazole is probably more effective in reducing clinical failure. Patients with invasive amoebiasis should receive a luminal amoebicide after treatment with tissue amoebicide. Paramomycin, iodoquinol and Diloxanidefuroate are the luminal amoebicides. Consumption of safe drinking water, avoiding raw vegetables, salads and taking food in hygienic places help in prevention [6, 7, 14 ].
Travelers' Diarrhoea (TD) TD has been defined as the occurrence of three or more loose stools each day or any number of loose stools accompanied by abdominal cramps, fever or vomiting. Usually seen in travelers from a developed to an underdeveloped country but can also be seen in Indians traveling within India. It affects 20% to 70% of travelers when travel is confined to 2 weeks. Incidence is high among very young (40%), and in the 15 to 29 years age group (29%) due to ingestion of higher volume of potentially contaminated food. Unpeeled fruits, uncooked vegetables (salads) and prepared meals stored at inadequate temperature or cooked at insufficient temperature are the main source of enteric pathogens for travelers. TD is caused by (a) Bacteria: E. Coli, Enterotoxigenic (ETEC),other species of E Coli, Shigella, Salmonella, and Campylobacter jejuni, and a new organism Aeromnas spp (b) Virus: Novoviruses, Rotaviruses and astroviruses; (c) Parasites: Giardia lamblia, Entamoeba histolytica, Cryptosporidium. Onset of diarrhoea is usually within the first week of travel and the duration of illness is short, lasting 24 hours to one week or longer. Clinical characteristics of illness are related to the organism responsible . This can cause significant morbidity, resulting in considerable inconvenience, embarrassment, and disruption of travel and business arrangements. Severe diarrhoea can cause impaired absorption of important medications (oral contraceptives, antiepileptic drugs, anticoagulants, or antimalarials) with disastrous consequences. Modest dehydration can compromise certain medical conditions (renal insufficiency, diabetes mellitus, cardiomyopathies, and inflammatory bowel disease). Compliance with traditional dietary recommendations (ingestion of safe food and beverages) prevents travelers' diarrhoea in a majority of travelers (boil, cook, peel or forget). It is preferable to wash hands frequently while traveling, particularly before preparing and taking food. Vaccines have a limited role in prevention, although oral Cholera vaccine Dukoral in two doses one week apart gives immunity against cholera as well as enterotoxogenic E Coli (50% short term protection) [5,8].
Bismuth subsalicylate when used as a prophylactic can reduce travelers' diarrhoea from 40% to 14%. Prompt replacement of fluids and electrolyte is essential. Prophylactic antibiotics are not recommended for most travelers. These can be used in immunosuppressed patients. Prompt use of antibiotics on occurrence of diarrhoea can limit the duration of illness. Fluoroquinolones, and azithromycin are effective in treatment. Rifaximin in dose of 200 mg thrice a day has been shown to be effective against noninvasive strains of E Coli and has emerged as the drug of choice for noninvasive travelers' diarrhoea . Antimotility drugs like loperamide and diphenoxylate are useful when combined with antibiotics. Loperamide in combination with antibiotic is safe even in infection with invasive pathogens .
Food Poisoning Food poisoning is an acute gastroenteritis caused by ingestion of food or drink contaminated with either living bacteria or their toxins or inorganic chemical substances and poisons derived from plants and animals. It is recognized by the sudden occurrences of group of illness within a short period of time among individuals who have consumed one or more foods in common. It can occur when canned meat is used or milk preparations are made from pooled milk in bulk. They are mostly seen on religious and festival occasions when large gatherings partake the meal. Outbreaks are common when the environmental temperature is high. Treatment is symptomatic. Observing all precautions for proper sanitation, eating only well cooked food and other sanitary measures will prevent food poisoning. The food poisoning may occur as a result of eating any of the following : -
(a). Fungi like Amanita phalloides instead of edible mushroom or eating sprouting potatoes, which contains excess of alkaloid solanine.
(b). Food contaminated by agricultural or industrial activities, fertilizers and pesticides, metallic poisons as a result of faulty cooking or storing in cheap enamel dishes or galvanized pans.
(c). Food infected with organisms like salmonella, clostridium and staphylococcus
Viral Hepatitis An acute or sub acute febrile infectious disease characterized by sudden onset, nausea, anorexia and abdominal discomfort followed by dark coloured urine, light coloured stools and appearance of jaundice in sclera or skin is caused by various viruses like viral hepatitis A, B, C, D, E and G viruses. Hepatitis A and hepatitis E virus infection have a faecal oral route transmission. Hepatitis A virus epidemics have occurred in India and cases are associated with heavy rainfall. Hepatitis E virus infection is essentially water borne disease. Person to person spread is the most common mode of transmission. Water should be boiled before use. Personal hygiene must be maintained at an extremely high level.
Previously unvaccinated travelers to India should receive hepatitis A vaccine. Two doses are required, second dose to be given 6 to 24 months after first dose. Vaccine given even on the day of departure protects the traveler because of long incubation period of hepatitis A. A combination hepatitis A and typhoid (vi cps) vaccine offers protection against both water borne diseases. Use of immune globulin for travel prophylaxis of hepatitis A has become obsolete now . Hepatitis B vaccine if not received earlier should also be advised for travelers to India. Combination hepatitis A and B vaccine is also available (to be given at 0, 1 and 6 months). A very rapid schedule of days 0, 7 and 21 with booster dose at 12 months has also been proposed .
Helminthiasis Hookworm disease (Ankylostomiasis) is fairly common throughout India. Areas of heavy infection are Himalayan regions, from UP to Assam. Cases of Schistosoma hematobium have been reported from Andhra Pradesh, Kerala, Rajasthan, Maharashtra, Punjab and Bihar. Tapeworm infestation can occur in travelers who eat uncooked beef or pork. The infestation may remain asymptomatic or discovered on routine examination of blood and stool. Definite treatment is available for specific infestation. The infestation is detected in the returned travelers who show eosinophilia after return. Delay or misdiagnosis can occur, as the link with the travel destination may not be apparent .
Wherever potable water is not available purification is done on a small scale to prevent water borne diseases. The methods recommended are (a) Boiling for 10 to 15 minutes, (b) Chemical disinfection by using bleaching powder, (c) Use of chlorine tablet. (d) Filtration by use of ceramic, membrane and carbon block filters .
Animal Borne Diseases
Rabies Rabies is a fatal disease caused by a filterable neurotropic virus, which is transmitted to man through the saliva of infected animals. The immediate source of infection is from the rabid domestic, street or pet dogs or cats. In rural areas wild dogs, foxes, jackals, wolves or mongooses may also attack human beings. The canines suffer and die of the disease within 10 days after the symptoms appear. Risk of bite exists from stray dogs in India, to adventure travelers, expatriate workers, field biologists and people going on conventional tours. Man to man transmission although rare is possible. The incubation period varies in human from a minimum of 9 days to many months but is usually between 4 and 8 weeks. If the dog is suspected to be rabid, immunization as available in that area should be taken immediately. Thorough cleansing of all wounds with soap and water and use of povidone iodine 1% solution is recommended. Suturing of the wound is to be avoided. Human rabies immunoglobulin 20 IU per kg body weight or 40 IU of equine immunoglobulin should be infiltrated promptly around the wound and remaining volume should be administrated IM at an anatomical site distant from vaccine administration. A full course of post-exposure anti-rabies vaccination is the only specific preventive treatment. Post-exposure prophylaxis (PEP) consists of a regimen of one dose of immunoglobulin (passive immunization) and five doses (1 mL into deltoid muscle) of rabies vaccine over a period of 28 days (0, 3, 7, 14, and 28). CDC has recently changed it to four doses on days 0, 3, 7 and 14 . Three types of cell culture vaccines are available in India, namely purified chick embryo cell vaccine (PCECV), purified vero cell rabies vaccine (PVRV) and human diploid cell vaccine (HDCV). As the disease is potentially fatal, one should avoid exposure to dog bite. Preexposure prophylaxis is recommended for high risk group, and consists of three doses of rabies vaccine 1 mL per dose given on days 0, 7, and 21. Preexposure rabies vaccine does not eliminate the need for treatment after the bite of a rabid animal, but it reduces the number of vaccine doses required in the post exposure regimen. If a person has received preexposure rabies immunization, PEP consists of two additional vaccine doses each 1.0 mL intramuscularly on days 1 and 3. Bites of rats and mice do not require anti-rabies postexposure prophylaxisÂ .
Brucellosis The disease is caused by Brucella a gram negative, non-motile cocobacillus. Brucellosis is a zoonosis causing abortions in cattle (Brucella abortus), and recurrent febrile infectious disease called the 'undulant fever' or 'abortus fever'