Unwanted souvenirs can plague world travelers.
"You're not going to see these things in businessmen who are staying in Hiltons and eating Western food when they go overseas," Dr. Sukhjit Takhar said at the 12th International Conference on Emergency Medicine. "These are diseases people contract when they are traveling for longer than a couple of weeks, or when they are really getting immersed in the local culture or eating the local food."
Taking a good travel history is the first step in diagnosing an internationally acquired disease, said Dr. Takhar, an emergency physician at the University of California San Francisco-Fresno.
"Find out where they went, and what they did. Were they staying in a hotel or out in the jungle dissecting monkeys? How long have they been back? This will give you an idea of the incubation period," Dr. Takhar said.
Also ask them if they took any medicine when they began to feel ill. Many travelers self-medicate with antibiotics, which can quell symptoms but not fully cure the illness.
Apart from acute diarrhea, systemic febrile illnesses are the most common syndromes among returning travelers. Most of those will be either malaria or dengue fever.
Among all travelers, 35% will have malaria, which causes about 150 fatalities in returned travelers each year; and 10% will have dengue. More than 60% of travelers with a systemic febrile illness coming from Africa will have malaria, Dr. Takhar added. About 30% of ill travelers returning from Southeast Asia will have dengue fever.
Because of the prevalence, morbidity, and mortality of malaria, especially that caused by the Plasmodium falciparum parasite, patients who appear to have the disease should receive immediate treatment, even if they don't present acutely ill to the ED. "Malaria symptoms are cyclical, so up to 40% of patients will be afebrile when you see them in the ED," Dr. Takhar said.
Falciparum malaria is the most dangerous form, provoking a flulike illness followed by paroxysmal fevers that last 8-12 hours and culminate in a drenching sweat. After that, the patient may feel well. The less common vivax malaria is also a less serious illness but causes similar symptoms.
The time since onset of symptoms is a clue to the type of malaria, Dr. Takhar said. The incubation period for falciparum malaria is about 10-14 days, while that of vivax malaria may be longer.
A blood smear will diagnose either form, with the parasites appearing in the erythrocytes. If the index of suspicion for malaria is high, however, and the patient reports travel to endemic areas, consider treating presumptively, Dr. Takhar advised. "They can look well and then decompensate very quickly, so don't wait around for a consult from a specialist."
The treatment of choice in the United States is now quinidine. "Chloroquines don't work very well any more, because the parasites have become resistant," he said, and the most potent antimalarial, artemether--an extract of the wormwood plant--isn't readily available in the United States.
A negative smear doesn't eliminate the possibility of malaria. "You can have a negative smear and still have it. The patient might have taken some doxycycline or azithromycin when he started feeling bad. Both of these have some antimalarial properties," he said. "If you don't see the parasites, get another smear in 12-24 hours."
A negative malaria smear in a febrile patient with a low white blood cell count, thrombocytopenia, and recent travel to the tropics may point to another mosquito-borne illness: dengue fever.
Diagnosing Dengue Fever
The prevalence of dengue has grown dramatically in recent decades. It's now found in more than 100 countries in Africa, Central and South America, the Caribbean, Asia, Southeast Asia, and even around the Mediterranean.
"Travelers who don't protect themselves from mosquitoes in these areas will very likely come down with this illness," he said.
The dengue virus causes a severe flulike illness with high fever, headache, retro-orbital pain, and a myalgia so painful that dengue is nicknamed "breakbone fever," Dr. Takhar said.
While most cases are self-limiting and require only supportive care, the hemorrhagic form can be deadly. In addition to petechiae, patients may have plasma leakage leading to pleural effusion, dropping platelets, rising hematocrit, and ascites.
Again, treatment is supportive. "You need to give IV fluids, but because these patients leak plasma, you should also put in a central line to measure central venous pressure," he said. Don't give any aspirin or ibnprofen for the pain, because those agents can exacerbate bleeding.
Tick Bites and Flatworms
Rickettsial diseases are sometimes seen in those who travel to Africa during tick season (April-November). Fever, myalgia, and headache characterize the illnesses; an eschar at the site of the tick bite is another clue. Most rickettsial infections respond quickly to doxycycline.
African travelers who swam in lakes may bring home a load of schistosomes. These flatworms live in freshwater snails, which release the larvae into the water. The larvae burrow into a swimmer's skin and take up residence in the liver. After maturing (up to 10 mm long), the worms mate and move into the rectal and mesenteric veins, where they release their eggs. The eggs pass into the intestine, bladder, or rectum, and are excreted.
The worms live up to 4 years, so natives of endemic areas can have huge loads that create chronic disease. However, travelers usually come down with an acute case, called Katayama fever. Symptoms include abdominal pain, cough, diarrhea, eosinophilia, fever, fatigue, and hepatosplenomegaly. Early in the course, the patient may have urticaria and a rash where the larvae penetrated the skin.
Diagnosis is by fecal smear or urinalysis positive for the flatworm's eggs. Schistosomal antibodies can also be positive. Praziquantel is the usual treatment, Dr. Takhar said. It should probably be prescribed by an infectious disease specialist who can provide adequate follow-up.
BY MICHELE G. SULLIVAN
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|Title Annotation:||Infectious Diseases|
|Author:||Sullivan, Michele G.|
|Publication:||Internal Medicine News|
|Date:||Jul 15, 2008|
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