Illnesses from Insects

Chikungunya

Chikungunya is a viral disease transmitted to humans by the bite of infected Aedes mosquitoes. It is often confused with dengue. After an incubation period of 1 to 12 days, symptoms occur, including sudden onset of fever and joint pain that can be severe; headache, muscle pain, weakness, chills, and GI symptoms also occur. Some patients develop a rash. Most recover within 7 to 10 days, but some continue to have symptoms for a month or more. Chikungunya occurs in tropical and subtropical areas, especially Africa, the Americas, Asia, the Caribbean, and the Indian subcontinent. Urban epidemics in India and Sri Lanka account for most cases.

Prevention: No vaccine is available. Travelers should be especially vigilant in applying insect repellent during daytime hours; mosquitoes that spread chikungunya are daytime feeders with 2 peaks of biting activity during the day: early morning and mid-to-late afternoon hours. During overcast days or when indoors, however, mosquitoes will feed all day. (See Mosquitoes.)

Dengue

Dengue is a viral infection that is spread to humans by the bite of Aedes mosquitoes. Dengue infections are widespread in most tropical and subtropical countries of the Americas, Asia, the Caribbean, the Indian Ocean islands, and the South Pacific. Also known as "breakbone fever," dengue occurs more frequently during warm, humid seasons, and transmission is more intense in urban areas, including downtown business areas. Anyone in an endemic area who has not previously been exposed to the currently circulating serotype is at risk of acquiring dengue.

About 2 to 5 days after being bitten, the victim experiences a sudden high fever, generalized weakness, and intense muscle, joint, and back pain (hence the term "break bone fever"). A rash may appear in some people. Dengue is usually self-limited, with an average duration of 6 days. Most persons with dengue do not need to be hospitalized, but those with persistent fever should seek medical attention as soon as possible.

Severe forms of dengue (dengue hemorrhagic fever and dengue shock syndrome) are rare in travelers. The symptoms for these forms of the infection begin like classic dengue but progress to severe abdominal pain and persistent vomiting; if left untreated, the illness can progress to bleeding at sites of minimal trauma, circulatory failure, shock, and death. Seek medical attention immediately if these symptoms appear.

Prevention: No vaccine is available or approved for travelers. Travelers should be especially vigilant in applying insect repellent during daytime hours; mosquitoes that spread dengue are daytime feeders with 2 peaks of biting activity during the day: early morning and mid-to-late afternoon hours. During overcast days or when indoors, however, mosquitoes will feed all day. (See Mosquitoes.)

Japanese Encephalitis

Japanese encephalitis (JE) is a viral disease that is spread to humans by the bite of the Culex mosquito. JE occurs in Asia, and most human infections occur in rural, agricultural areas. Risk is very low for short-term rural travelers not engaging in extensive unprotected outdoor activities. Risk for travelers who confine their travel to highly urban environments is nearly nonexistent, although rare cases have been reported from suburban areas adjacent to agricultural land.

Symptoms appear abruptly, with headache, high fever, nausea, and vomiting. If the illness progresses, it can lead to paralysis or death. There is no effective drug treatment for JE; the disease can only run its course, but it is still vital to seek supportive medical treatment.

Prevention: Personal protection measures and insect precautions are vital if traveling in a risk area. Make sure to use repellent during the Culex mosquitoes' peak biting times, which is between dusk and dawn. A vaccine is available but is not recommended for all travelers going to risk areas. Vaccination may be recommended for those who will be traveling extensively or making frequent short trips in rural areas or visiting an epidemic area. The vaccine series consists of 2 doses given 28 days apart and should be completed at least 1 week before potential exposure. The second dose may be given 7 days after the first dose in the case of imminent departure. For frequent or continued exposure, a third dose given 1 year after the first dose is necessary.

Malaria

Malaria is transmitted through the bite of the Anopheles mosquito and is the most frequent infectious cause of death for travelers going to the tropics and subtropics. Malaria is found in many parts of the world including Africa, Central and South America, the Indian subcontinent, the Middle East, the islands of the South Pacific, and Southeast Asia. Most malaria occurs in sub-Saharan Africa.

Symptoms usually develop within 10 days of exposure, or—less commonly—months or even years later. Symptoms always include fever and influenza-like symptoms such as chills, sweats, headaches, muscle aches, and/or a vague feeling of illness. Vomiting, abdominal pain, diarrhea, cough, and jaundice (yellowing of the skin and whites of the eyes) can also occur.

Travelers who have been in a malaria-endemic area within the past year and have a fever or influenza-like symptoms should seek immediate medical attention.

Of the 5 types of malaria that cause human disease, P. falciparum usually occurs about 10 to 12 days after infection and is a medical emergency. If not treated immediately and properly, it can be fatal. Illness caused by the milder types (P. vivax, P. ovale, P. malariae) is not usually life-threatening but can be a serious health risk for the very young, the elderly, and persons with underlying illness. A less common cause of malaria, P. knowlesi, can cause a severe and potentially fatal infection. Malaria caused by P. vivax and P. ovale may eventually resolve without treatment but can relapse periodically until properly treated.

Prevention: Antimalarial drugs and insect precautions are important safeguards when traveling to a malarious area. Remember to observe insect precautions even if using preventive medications, and be especially vigilant using repellent between dusk and dawn when Anopheles mosquitoes are most active.

A travel medicine specialist can best explain which destinations require preventive measures and can help choose an appropriate antimalarial drug for that destination. Travelers must take the antimalarial drug before, during, and after travel to a malarious area. Taking the drug before travel allows the drugs to build up to an effective level and gives the health care provider time to assess any side effects. Continuing the drug after leaving a malarious area suppresses most attacks of longer-incubating malaria.

Atovaquone-proguanil is the primary and most often prescribed drug for all malaria species in all areas with malaria, especially for short-term travelers. Atovaquone-proguanil should not be used by pregnant women, people with severe renal failure, or those who are allergic to either of the drug components.

  • Atovaquone-proguanil is taken by mouth once daily. Start taking it 1 day before arrival in a malarious area, take it daily while in the risk area, and continue to take it daily for 1 week after leaving the risk area. Take this drug with a meal or milk, at the same meal time each day. Missed doses can be taken later in the day but should not be doubled the next day if missed completely.

Mefloquine is an alternative drug for all malaria species; for long-stay travelers, it is often the most convenient regimen. Minor side effects include stomach distress, dizziness, headache, and vivid dreams, which tend to be mild or temporary. Be aware that mild dizziness is a possible side effect and may impact travelers who plan to drive, pilot a plane, or operate machinery. Severe side effects can include serious neurological and psychiatric side effects that can persist for months, years, or permanently, even after discontinuation of mefloquine. Mefloquine is not recommended for persons who are allergic to mefloquine or related compounds, persons with active depression or recent history of depression or any psychiatric disorder, and persons with a history of convulsions.

  • Mefloquine is taken by mouth once a week. Start taking the drug 2 to 3 weeks before arriving in a malarious area, take it while in the risk area, and continue to take it for 4 weeks after leaving the risk area. Missed doses should be taken as soon as possible that same week, with the normal schedule resuming the next week. Do not take a double dose if a dose is completely missed one week.

Doxycycline is an alternative drug for all malaria species. It may also be recommended for travel to areas of southeastern Asia where malaria is resistant to mefloquine, or for people who can't use mefloquine or atovaquone-proguanil. Skin sensitivity to sunlight is a potential side effect that can lead to severe sunburn, especially in tropical sun. To lower this risk, use a sunscreen that blocks both UVA and UVB rays, avoid prolonged exposure to the sun, and wear protective clothing and a hat. Women who take doxycycline may develop yeast infections and should an antifungal drug with them. Do not take this drug if pregnant, younger than 8 years in the U.S. (or 12 years in the U.K.), or allergic to doxycycline or tetracycline.

  • Doxycycline is taken by mouth once daily. Start taking it 1 day before arrival in a malarious area, take it daily while in the risk area, and continue to take it daily for 4 weeks after leaving the risk area. Take this drug with food or at least 8 ounces of fluid while sitting or standing (to prevent throat or stomach irritation). Do not take Pepto-Bismol or antacids because they can interfere with absorption of doxycycline. Late doses can be made up the same day, resuming the normal schedule the next day. Do not take a double dose if a dose is completely missed one day.

Chloroquine is an alternative drug for limited areas where there is no resistance to this drug. Chloroquine is effective and safe and has also been shown to be safe for infants and pregnant women. Minor side effects include upset stomach, headache, dizziness, blurred vision, and itching. Serious side effects are uncommon. Rarely, seizures or psychosis have occurred. Those who have epilepsy may be at risk for seizures. Those who are allergic to chloroquine or have retinal or visual field changes should not take the drug.

  • Chloroquine is taken by mouth once a week. Start taking the drug 1 week before arrival in a malarious area, continue taking it while in the risk area, and take it for 4 weeks after leaving the risk area. Take chloroquine with meals or in divided, twice-weekly doses to avoid stomach upset. If a dose is missed, take it as soon as possible that same week and then resume the normal schedule the next week. Do not take a double dose if a dose is completely missed one week.

Primaquine is not considered a first-line drug of choice for prevention of malaria. It should be used for prevention of malaria only when none of the other drugs listed above can be used and only for travel to areas that have only P. vivax malaria. Travelers who are pregnant or have low levels of glucose-6-phosphate dehydrogenase (G6PD) should not take this drug.

  • For prevention, primaquine is taken by mouth once daily. Start taking it 1 day before arrival in the malarious area, take it daily while in the risk area, and continue to take it daily for 1 week after leaving the risk area. Take with food (to reduce stomach irritation). Late doses can be made up on the same day. Do not double the dose if a dose is completely missed.
  • Another use for primaquine is in preventing certain kinds of malaria (P. vivax and P. ovale) from occurring ("relapsing") months or even years after routine preventive medications have been stopped, generally for people who have had prolonged exposure in certain malarious areas.

Other regimens may be recommended by health care providers in certain circumstances. Travelers should understand why their regimen has been chosen, how to take the medication appropriately, and should carry written instructions.

Self-treatment: In rare situations, it may be prudent to carry a drug for self-treatment of malaria; however, this is a temporary measure, and medical attention should be sought as soon as possible. Take the drug promptly, according to a health care provider's instructions, if fever and illness occur during travel and medical care is not available within 24 hours.

Either artemether-lumefantrine (Coartem) or atovaquone-proguanil (Malarone) should be used for self-treatment.

  • The adult self-treatment dose for artemether-lumefantrine consists of 6 doses taken over 3 days. On the first day, 4 tablets are taken followed by 4 more tablets 8 hours later. On the second and third days, 4 tablets are taken every 12 hours. Artemether-lumefantrine needs to be taken with food; do not take with grapefruit juice. Artemether-lumefantrine should not be used by pregnant women, persons with a heart condition called QTc prolongation, or those with an allergy to either component of the drug.
  • The adult self-treatment dose for atovaquone-proguanil consists of 4 tablets taken once daily for 3 days. Atovaquone-proguanil should be taken with milk or a meal. Atovaquone-proguanil should not be used by pregnant women, persons with renal failure, or those who are allergic to either component of the drug.

An alternative to artemether-lumefantrine or atovaquone-proguanil for self-treatment is quinine plus doxycycline, but this drug has a much more complex schedule of doses and is frequently associated with adverse effects.

Note: The treatment drug should not be the same as the drug being used for prevention.

Yellow Fever

Yellow fever is a viral disease transmitted by Aedes mosquitoes; the major areas of risk are parts of Africa and South America. Although incidence of infection among travelers is very low, the fatality rate in nonimmune travelers is nearly 50%. Yellow fever is named for the characteristic jaundice (yellow eyes and skin) that results from viral invasion of liver cells in severe cases. Most cases begin with a sudden headache, fever, and muscle aches.

Prevention: Yellow fever vaccine consists of a single injected dose, given at least 10 days before entering a risk area. Because the disease can be fatal and the vaccine is highly effective, health care providers may recommend vaccination if traveling to an area of yellow fever risk. Proof of yellow fever vaccination may be required for entry to some countries. (See Required Vaccines and International Certificate of Vaccination or Prophylaxis.) Travelers should be especially vigilant in applying insect repellent during daytime hours regardless of vaccination status; mosquitoes that spread yellow fever are daytime feeders with 2 peaks of biting activity during the day: early morning and mid-to-late afternoon hours. During overcast days or when indoors, however, mosquitoes will feed all day.

Zika Virus Infection

Zika virus infection is a viral disease transmitted to humans by the bite of infected Aedes mosquitoes and is closely related to dengue. However, Zika virus infection causes milder illness, including fever, malaise, headache, rash, joint and muscle pain, and inflamed eyes. Zika virus infection occurs in at least 60 countries of Africa, the Americas, the Caribbean, Pacific Islands, and Southeast Asia. Sexual transmission also occurs but is uncommon. Infection during pregnancy has resulted in children with congenital central nervous system malformations.

Prevention: Use repellent during the mosquitoes' peak biting times; mosquitoes that spread Zika virus are daytime feeders with 2 peaks of biting activity during the day: early morning and mid-to-late afternoon hours. During overcast days or when indoors, however, mosquitoes will feed all day. Abstinence or condom use is recommended if a male sexual partner has history of recent travel to risk areas. Pregnant women with a sexual partner (male or female) residing in or returning from a Zika-risk area should abstain from sexual activity or use barrier methods. (See Mosquitoes.)

See Additional Illnesses for less common illnesses that may be contracted from insects or other arthropods.