Duration Health

Travel and Tropical Medicine

Jet lag, parasitic infections, and malaria

Jet lag


Jet lag occurs when travelers cross several time zones rapidly by plane and have to adjust to the new time schedule of their destination. The body’s circadian rhythms (also known as the wake-sleep schedule or “biological clock”) are forcibly recalibrated. It takes approximately one day per time zone crossed for the body to reset its clock. The occurrence and severity of jet lag depends on different factors, but generally it occurs most often when more than three times zones are crossed, is more severe the more time zones that are crossed, and it occurs more often in older individuals. Eastward travel causes more jet lag than westward travel: eastward travel causes difficulty falling asleep at bedtime at the new destination, so it’s hard to get up the next morning, and with westward travel, waking up too early affects sleep time.

The most common symptoms of jet lag include difficulty falling asleep at the usual bedtime, waking up too early, and disturbed sleep. Other symptoms include fatigue, difficulty concentrating, headache, irritability, gastrointestinal symptoms, and lack of appetite.

Contributing factors to a feeling of jet lag include lack of sleep and decreased movement on the airplane, dehydration, altered normal mealtimes and exercise routines, and culture shock when the final destination is reached. Alcohol and caffeine ingestion at different times of the day while traveling versus when at home can also contribute.


General treatment for jet lag includes gradually adjusting the sleep schedule to the destination time before travel, figuring out the best sleep times after arrival to adjust to the destination, and light exposure (sunshine is a great source). To aid in resetting the body’s biological clock, melatonin can be taken. For fatigue and difficulty concentrating, stimulants like caffeine or exercise may help. For headache, ibuprofen or acetaminophen may improve symptoms. If dehydrated, oral fluids will help (avoid heavily caffeinated drinks). For gastrointestinal symptoms or lack of appetite, smaller meals before and during flight may help.

When to Worry

If symptoms of jet lag last longer than two weeks, something else may be causing your difficulty to sleep and you should seek medical attention.

Parasitic infections


Travelers can acquire infections from parasites through contaminated food or water, directly through fecal-oral contact, bites from mosquitoes or other insects (vector-borne), and person-to-person contact (for example, lice). Parasites are classified as protozoa, helminths (worms), or ectoparasites (fleas and lice). The most common parasites acquired through ingesting contaminated food or water are Giardia, Cryptosporidium, and Cyclospora. Other diseases caused by parasites in contaminated food or water that are not as common are amebiasis, ascariasis, trichinosis, taeniasis (tapeworm), and fascioliasis. Parasitic diseases that are vector-borne include malaria, leishmaniasis, Chagas disease, lymphatic filariasis, African sleeping sickness, and onchocerciasis (river blindness).

Before traveling, especially internationally, the traveler should schedule a travel medicine provider visit and seek information on the CDC’s Travelers’ Health website (https://www.cdc.gov/travel).

Symptoms of parasitic infections vary widely depending on the causative organism.

Giardia can cause: diarrhea, gas, greasy stools that tend to float, stomach or abdominal cramps, upset stomach or nausea/vomiting, and dehydration (loss of fluids)

Scabies can cause: intense itching (pruritus) especially at night, pimple-like (papular) itchy rash, rash can include tiny blisters (vesicles) and scales; scratching the rash can cause skin sores and sometimes the sores become infected by bacteria

Head lice can cause: itching (pruritus) on the head, a tickling feeling or a sensation of something moving in the hair, irritability and sleeplessness, and sores on the head caused by scratching, which can sometimes become infected with bacteria

Body lice can cause: itching (pruritus) on infested parts of the body, and sores on the body caused by scratching, which can sometimes become infected with bacteria

Pubic lice can cause: itching (pruritus) in the pubic and groin area, sores caused by scratching, which can sometimes become infected with bacteria, visible lice eggs (nits) or lice crawling or attached to pubic hair or (less commonly) other hairy areas of the body (eyelashes, eyebrows, beard, mustache, armpits, chest, back)

Taeniasis (tapeworm) can cause: upset stomach, abdominal pain, loss of appetite, weight loss, tapeworm segments may be seen after they have passed through the anus or in the feces


There are a number of medications used to treat parasitic infections depending on the causative organism, and most of these medications are able to treat more than one type of parasite. Metronidazole is used to treat giardiasis. Ivermectin is used to treat scabies, lice, and infections acquired during travel outside the U.S., such as lymphatic filariasis and onchocerciasis. Albendazole is used to treat taeniasis (tapeworm), hookworm and pinworm.

When To Worry

Seek immediate medical care if you have any of the following:



Malaria is caused by the protozoan parasite Plasmodium, carried by bite of the female Anopheles mosquito. There are 4 major species that cause malaria: P. falciparum, P. vivax, P. ovale, P. malariae (P. knowlesi is another species that causes disease less frequently). Malaria is responsible for over 200 million infections and almost 1/2 million deaths annually globally. Symptoms include high fevers, shaking chills, flu-like illness, headache, myalgias, malaise, and mental confusion. Whether malaria results in death depends on the infecting parasite, severity of the disease (seizures, coma, respiratory distress) and susceptible populations (very old, very young, underlying diseases). Symptoms can appear in as short as 7 days or up to several months after exposure. It must be diagnosed microscopically in a laboratory, although there are rapid antigen tests available (rapid diagnostic tests, or RDTs) which can be done in remote areas without lab access.

Malaria-carrying mosquitoes are found in the following areas of the world: Africa, Central America, South America, some parts of the Caribbean, Asia (South Asia, Southeast Asia, Middle East), Eastern Europe, and the South Pacific. Malaria is not endemic to the U.S., however, there are approximately 2000 cases of malaria diagnosed every year in the U.S., mostly in travelers returning from malaria-endemic countries; the vast majority of cases are from African countries.

There is no vaccine for malaria, so prevention is key. Travelers to countries where malaria is found should use EPA-registered insect repellents such as DEET or picaridin, sleep under bed netting, avoid outside activity at night if not protected (Anopheles mosquitoes are most active between dusk and dawn), and wear long-sleeved shirts, long pants and hats, all preferably treated with permethrin, another insect repellent. In most cases, travelers should also take medication for malaria prevention.

Prevention and Treatment

All travelers should consider taking malaria prophylaxis when traveling to malaria endemic countries. The drugs taken should cover the species prevalent in the areas of travel. Before traveling, especially internationally, the traveler should schedule a travel medicine provider visit or seek information on the CDC’s Travelers’ Health website (https://www.cdc.gov/travel) about malaria prophylaxis. Drugs are not 100% effective and should be combined with the other prevention measures mentioned above. Other considerations for the choice of malaria prophylaxis are cost of the medication, convenience of the regimen, adverse effects, and potential drug interactions. In some circumstances like pregnancy or pediatrics, some drugs may not be safe. Prophylaxis may not be necessary if travel is exclusively in cities where local malaria transmission is low or nonexistent because of mosquito control measures, or if there is widespread drug resistance in a certain area.

The drugs used most commonly for malaria prophylaxis are all oral agents and include: atovaquone-proguanil (generic for Malarone®), mefloquine (generic for Lariam®), doxycycline, chloroquine and hydroxychloroquine, primaquine, and tafenoquine.

If a traveler contracts malaria, they should be treated in a healthcare facility, whether in the country where they are traveling, or in another if better facilities are available. Depending on the traveler’s itinerary and circumstances, antimalarial treatment can be dispensed before a trip as stand-by emergency treatment (SBET), to be taken if the traveler contracts malaria, but the traveler must be carefully educated about this and should contact a health provider before taking medication for treatment.

Stand-by emergency treatment should be obtained from a reliable supply like in the U.S. before travel because many counterfeit medications exist globally; as well, a traveler should avoid depleting the local supply of the medication in resource-deprived countries. The two drug combinations used most frequently for stand-by emergency treatment are atovaquone-proguanil (generic for Malarone®) and artemether-lumefantrine.

When To Worry
Seek immediate medical care for the following symptoms of malaria:

Quick Guide

If you have the following symptoms after travel across several time zones

  • difficulty falling asleep at the usual bedtime, waking up too early, or disturbed sleep
  • fatigue
  • difficulty concentrating
  • headache
  • irritability
  • gastrointestinal symptoms
  • lack of appetite

You may have

jet lag

Consider using


traveling east: 2-5mg orally after dark, 30 minutes before bedtime in the new time zone or if on the plane, then take for the next 4 nights in the new time zone, after dark, 30 minutes before bedtime (if still drowsy the day after using this medication, try a lower dose)

traveling west: a dose is not needed for first travel night, but then take 2-5mg orally for the next 4 nights in the new time zone, after dark, 30 minutes before bedtime (may not always be needed for westbound travel)


ibuprofen 600 mg every 6 hours as needed for pain


acetaminophen 1000 mg every 6-8 hours as needed for pain (do not exceed 3000 mg per day)

If you have risk factors such as

  • contaminated drinking water or uncooked food
  • backpacking or camping and drinking untreated water from lakes or rivers
  • working in a childcare setting
  • close contact with someone with giardiasis
  • travel to developing countries
  • exposure to human feces


symptoms including

  • diarrhea
  • gas
  • greasy stools that tend to float
  • stomach or abdominal cramps
  • upset stomach or nausea/vomiting
  • dehydration (loss of fluids)

You may have


Consider using

metronidazole* (generic for Flagyl®) 500 mg orally every 12 hours for 7 days

*Off-label use. Metronidazole is not FDA-approved for the treatment of giardiasis.

If you have

  • intense itching (pruritus), especially in the web spaces of the fingers, and especially at night
  • pimple-like (papular) itchy rash
  • rash with tiny blisters (vesicles) and scales

You may have


Consider using

permethrin 5% cream, applied from neck down and left on for 12 hours


ivermectin* 15 mg by mouth once

*Off-label use. Ivermectin is not FDA-approved for the treatment of scabies.

If you

  • are traveling to a malaria-endemic region
  • have been advised to take malaria prophylaxis by a healthcare provider

Consider using

atovaquone-proguanil (generic for Malarone®) 250 mg atovaquone and 100 mg proguanil hydrochloride 1 tablet orally daily; begin 1–2 days before travel to malarious areas, take daily at the same time each day while in the malarious area, and for 7 days after leaving such areas


mefloquine (generic for Lariam®) 250 mg orally once weekly; begin at least 2 weeks before travel to malarious areas, take weekly on the same day of the week while in the malarious area, and for 4 weeks after leaving such areas


doxycycline 100mg orally daily; begin 1–2 days before travel to malarious areas, take daily at the same time each day while in the malarious area, and for 4 weeks after leaving such areas


Doxycycline is an antibiotic, and belongs to a class of medications called tetracyclines. Doxycycline can be used to treat multiple types of infections, including respiratory tract infections, tick-borne illness, E. coli, Cholera, Lyme disease, Yersinia (bubonic plague), Tularemia, and more. This medication should be taken with food.

Prescription only


Atovaquone-proguanil (generic for Malarone) is used for malaria prophylaxis in areas with chloroquine-resistant Plasmodium falciparum, and can be used in most parts of the world where malaria occurs. Take it daily for 1-2 days before possible exposure to malaria, and continue daily for 7 days after leaving an exposed area. If you plan to travel to malaria-endemic areas, discuss with your Duration Health provider to determine which prophylaxis is appropriate for you.

Prescription only


Metronidazole (generic for Flagyl) is an antiprotozoal and antibiotic, which means it fights bacteria as well as other organisms that cause disease. Metronidazole can be used to treat infections in the abdomen.

Prescription only


Ivermectin is used to treat parasite infections. It is FDA-approved to treat two parasitic infections, strongyloidiasis and onchocerciasis, which are relatively rare in the United States. It is also often used in an off-label manner to treat scabies and lice. This medication should be taken on an empty stomach.

Prescription only



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