Post-Travel Parasitic Disease Including Evaluation of Eosinophilia

Introduction

As the world becomes increasingly interconnected, international travel continues to rise among residents of the United States. With that, the risk for acquiring travel-associated infections is increasing. Although many of these infections are mild and self-limited, several cause symptoms that can persist for months to years, and others can lead to hospitalization and even death. A few post-travel infections are apparent soon after returning; however, parasitic infections can be difficult to diagnose because they present with non-specific symptoms, they have variable and sometimes long incubation periods, there is limited availability of diagnostic testing, and healthcare professionals may have insufficient knowledge about these conditions. Obtaining a complete travel history is helpful in developing a differential diagnosis in a symptomatic returning traveler; however, it is often the presence of peripheral eosinophilia that prompts healthcare professionals to consider parasitic infections. This chapter will discuss parasitic diseases in the returning traveler and will categorize these diseases in terms of whether or not they cause peripheral eosinophilia.

Peripheral eosinophilia

Peripheral eosinophilia, defined as ≥500 eosinophils/µL, is often subdivided into mild (≥500 eosinophils/µL), moderate (≥1,500 eosinophils/µL), and severe (≥5,000 eosinophils/µL). Most tests will also report eosinophil percentage, which is the proportion of eosinophils out of 100 white blood cells. A normal eosinophil percentage is less than 5%; however, the degree of eosinophilia should not be determined by percentage alone because percentage can be influenced by the number of other cell types present. For example, if a patient has leukopenia, the eosinophil percentage would be relatively higher, but the absolute count may remain within normal limits.

Eosinophils are multifunctional pro-inflammatory cells that are formed in greater numbers in response to a variety of conditions, including medications and allergic or eosinophilic drug reactions, malignancy, autoimmune disorders, atopic disorders, and parasitic infection. The majority of eosinophils reside in tissue, particularly in the gastrointestinal tract; however, in pathologic conditions, eosinophils are recruited to other anatomic sites through the peripheral blood vessels. The presence of eosinophils outside of tissues or blood (e.g., in cerebral spinal fluid) should be considered an abnormal finding. Peripheral eosinophilia is present in many parasitic infections. Eosinophils liberate helminthotoxic proteins and reactive oxygen species that play a key role in eradicating an invading parasite.

Eosinophilia can be an important clinical finding when diagnosing a parasitic disease, but it is not a perfect metric. This chapter provides general guidelines on the degree of eosinophilia expected in various parasitic diseases; however, an individual host's immune response may not fit the expected degree of eosinophilia. Concomitant medications or medical conditions might also impact the degree of eosinophilia; for example, a coexisting bacterial or viral infection might suppress peripheral eosinophilia.

Presence of eosinophilia may not correlate with other laboratory findings. For example, stool ova and parasite tests are commonly ordered when evaluating a patient for a parasitic disease. Ova are produced by adult intestinal helminths, but eosinophilia may be present earlier in infection when larvae or immature parasites are migrating within the host. In this case, a stool ova and parasite test may be negative because there are not yet mature adult helminths producing ova. For example, in the case of strongyloidiasis, an intestinal helminth, stool ova and parasite tests are commonly negative, and serology is needed for diagnosis.

Absolute eosinophil count does not predict the severity of disease. In general, elevated eosinophil counts and symptoms are both associated with a naïve host. If a person has frequent exposure to a parasite, it is less likely they will have a significant eosinophilia or symptoms. For this reason, the resources provided in this chapter are most applicable to U.S. residents returning from travel to endemic countries, rather than new immigrants from endemic countries, although even the expatriate or very long-term returning traveler may have diminished peripheral eosinophilia because of repeated exposure (see Post-Arrival Medical Screening for Newly Arrived Refugees, Immigrants, and Migrants, and Long-Term Travelers and Expatriates chapters).

Evaluation for parasitic diseases

For a complete discussion of the clinical evaluation of a returning traveler, see the Post-Travel Evaluation of the Ill Traveler chapter. As with all diseases of returning travelers, history gathering is of particular importance, although the physical examination and laboratory testing can also provide clues.

Specific exposures

Many parasitic infections are the result of highly specific exposures, such as ingesting raw crayfish or freshwater fish. Considering the patient's location of travel and symptoms, healthcare professionals can question travelers about exposures related to parasitic diseases of interest.

Time to symptom development

Incubation time can be an important differentiator between parasitic diseases producing similar symptoms; however, it can be difficult to discern exactly when a patient was exposed. Patients may not remember ingesting a specific food item, and bites of some vectors might not produce symptoms at the time of the bite. This can be even more challenging if the exposure occurred several weeks or months prior, as is the case with some parasitic diseases.

Physical examination

A thorough skin exam is particularly important; several parasites enter the body by penetrating the skin, either after direct contact with freshwater, after direct contact with contaminated soil, or after the bite of an infected insect vector. Additionally, knowing the potential migratory patterns of a specific parasite within the host can help healthcare professionals perform a focused physical examination. For example, if a parasite commonly migrates to the liver, it may be prudent to evaluate for right upper quadrant pain.

Laboratory testing

Healthcare professionals should consider obtaining a complete blood count with differential to assess for peripheral eosinophilia. If peripheral eosinophilia is identified, additional organ-specific laboratory testing may be warranted. Disease-specific testing is available for some parasitic infections; however, understanding who performs these tests, when it is appropriate to order them, and how to interpret them can be difficult. The Centers for Disease Control and Prevention's (CDC's) Division of Parasitic Diseases and Malaria offers consultation services that help healthcare professionals with diagnosis and management of suspected parasitic diseases. Information on how to utilize the healthcare professional consultation services is available. CDC's Division of Parasitic Diseases and Malaria DPDx team is also available to assist laboratorians and pathologists in the diagnosis of parasitic diseases through review of specimens. Information on offered services and submission process is available.

Parasitic diseases in the returning traveler

The remainder of this chapter focuses on resources that assist healthcare professionals in establishing a differential diagnosis in symptomatic clinic patients returning from short- or long-term travel or residence outside of the United States. Figure 10.6.1 is a flow diagram separating conditions by presence or absence of peripheral eosinophilia and common presenting symptoms. A subsequent series of tables (Tables 10.6.1–10.6.8) and short summaries provide more information on each parasite. Specific prevention and treatment information for each parasitic disease can be found by accessing the internet address in the first column of each table. In general, travelers should avoid raw or undercooked food, including fresh vegetables or salad that may have been washed in contaminated water; wash hands with soap or use hand sanitizer as often as possible and especially prior to meals; wear shoes when walking on potentially contaminated soil or sand; use insect repellant and cover arms and legs to prevent insect bites; and take medications and vaccinations recommended by their travel medicine specialist. More information on disease prevention during travel can be found in The Pre-Travel Consultation; Food and Water Precautions for Travelers; Water Disinfection for Travelers; and Mosquitoes, Ticks, and Other Arthropods. Healthcare professionals seeking diagnostic or treatment assistance with any of these parasitic diseases can also reach out to the Parasitic Disease Branch's clinical inquiries service using the information above.

Figure 10.6.1

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This diagram aids clinicians in diagnosing a symptomatic, clinic patient returning from travel or residence outside the U.S. Symptomatic patient returning from travel or residence outside the U.S. History, physical examination (with particular attention to skin findings, jaundice, abdominal pain, altered mental status, nuchal rigidity, pulmonary consolidation, lymphadenopathy), and general laboratory investigations (including complete blood count with differential). Concern for parasitic infection based on history, examination, and initial laboratory evaluation. Presence of peripheral eosinophilia, (Mild 500-1,499 cells/pL, Moderate 1,500-4,999 cells/uL, Severe 25,000 cells/jL). Fever and abdominal pain. Clonorchiasis, Fascioliasis, Opisthorchlasis, Paragonimiasis. Gastrointestinal

Symptoms without

Fever. Angiostrongyliasis, Anisakiasis, Ascariasis, Cystic echinococcosis, Hookworm, Strongyloidiasis, Trichuriasis. Pulmonary Symptoms. Paragonimiasis. Fever and Myositis. Muscular sarcocystosis, Trichinellosis. Allergic or

Dermatologic/ Soft Tissue. Anisakiasis, Ascariasis, Gnathostomiasis, Lolasis, Lymphatic filariasis, Onchocerciasis, Scabies, Schistosomiasis. Fever and Central Nervous System Symptoms, Angiostrongyliasis, Baylisascariasis, Gnathostomiasis, Urinary Symptoms. Schistosomiasis. Absence of peripheral eosinophilia, (<500 cells/pL). Alveolar echinococcosis, Amebiasis, Cryptosporidiosis, Cutaneous larva migrans, Cyclosporiasis, Cysticercosis, Giardiasis, Leishmaniasis, cutaneous, Leishmaniasis, visceral, Malaria

Pinworm, Taeniasis, Toxoplasmosis, Trypanosomiasis, African Trypanosomiasis, American (Chagas disease).

Show Text Description

Parasitic causes of eosinophilia, fever, and abdominal pain

Clonorchiasis (Clonorchis sinensis)

Common symptoms in the acute phase include abdominal pain and fever, as well as sequelae of intermittently obstructed biliary ducts, including right upper quadrant pain, jaundice, pancreatitis, or ascending cholangitis, occurring near the end of the acute phase. Chronically, hepatomegaly and malnutrition can occur. Chronic infection can also be associated with cholangiocarcinoma. All travelers to endemic areas could intentionally or accidentally ingest raw freshwater fish or snails and be at risk for infection.

Fascioliasis (Fasciola hepatica)

Common symptoms in the acute phase of infection include abdominal pain and fever that can be accompanied by urticaria or cough. The chronic or biliary phase begins when immature worms reach the bile ducts, mature into adult worms, and start producing eggs. Chronic infection can result in biliary disease and liver fibrosis, which can be symptomatic but are more likely to be discovered by abnormal laboratory results or signs of advanced liver disease. All travelers (both short- and long-term travelers and expatriates) to endemic areas could accidentally ingest contaminated raw vegetables (watercress) or water and be at risk for infection.

Opisthorchiasis (Opisthorchis felineus, Opisthorchis viverrini)

Common symptoms in the acute phase are like that of fascioliasis, including abdominal pain and fever. The chronic phase begins after 30 days of infection and is characterized by biliary obstruction (adult worms) and sequelae, including pancreatitis or ascending cholangitis. Chronic infection can be associated with cholangiocarcinoma. All travelers to endemic areas could intentionally or accidentally ingest raw freshwater fish and be at risk for infection.

Paragonimiasis (Paragonimus westermani, Paragonimus africanus, Paragonimus mexicanus)

See Parasitic Causes of Eosinophilia, Fever, and Pulmonary Symptoms section in this chapter.

Table 10.6.1: Parasitic causes of eosinophilia, fever, and abdominal pain

Parasitic causes of eosinophilia and gastrointestinal symptoms without fever

Angiostrongyliasis (Angiostrongylus costaricensis)

Parasites from rats infect slugs or snails. Animals that ingest snails or slugs, such as freshwater crabs, frogs, and shrimp, also carry the parasite. Common symptoms in the acute phase include nausea, vomiting, and abdominal pain characteristic of eosinophilic gastritis. Occasionally, pruritic rash can occur. This species of parasite does not cause neurologic manifestations. All travelers to endemic areas could intentionally or accidentally ingest raw or undercooked slugs, snails, crabs, frogs, or shrimp and be at risk for infection.

Anisakiasis (Pseudoterranova decipiens, Anisakis simplex)

Anisakis invades the stomach or intestinal wall of humans. Parasites are acquired ingesting infected fish or squid that share an environment with whales, sea lions, or crustaceans. Within hours to days, people can experience abdominal pain, nausea, vomiting, bloating, diarrhea, and hematochezia. Occasionally, pruritic rashes occur. Some infected people experience a tingling sensation during or after ingestion. All travelers to endemic areas could intentionally or accidentally ingest raw or undercooked fish or squid and be at risk for infection.

Ascariasis (Ascaris lumbricoides)

Ascariasis is a type of soil-transmitted helminth. Ascaris eggs are passed in the feces of infected humans, which can be accidentally ingested through contaminated water or soil. Symptoms can be nondescript and are often characterized by intermittent, vague abdominal pain. Heavy infections can lead to intestinal blockage. Cough can result from pulmonary migration of larvae. All travelers to endemic areas can be at risk for infection.

Cystic Echinococcosis (Echinococcus granulosus)

Cystic echinococcosis, also known as hydatid disease, is caused by infection with the larval stage of Echinococcus granulosus. Symptoms can take years to manifest, and the nature and severity of symptoms depend on the location and size of the cystic lesions that develop. Cysts are most common in the liver, followed by the lungs, and can impede nearby structures. Cysts can rupture, and leakage of cystic fluid can lead to anaphylaxis and death. Eosinophilia is more likely to be present when there is leakage of cystic fluid, stimulating a host immune response. Long-term travelers and expatriates are at higher risk for infection than short-term travelers.

Hookworm (Necator americanus, Ancylostoma duodenale)

Hookworms are a type of soil-transmitted helminth. They are transmitted by larvae penetrating the skin. Acute infection with human hookworm is usually characterized by gastrointestinal symptoms and pulmonary symptoms, depending on the location of parasite migration. If worm burden is high enough, chronic infection can lead to anemia and protein deficiency. Long-term travelers and expatriates are at higher risk of clinically significant disease, but all travelers could be exposed to the parasite and become infected.

Strongyloidiasis (Strongyloides stercoralis)

Strongyloides enters the body through exposed skin, such as bare feet. After penetration, larvae migrate to the small intestine and into the lymphatics and bloodstream to the lungs, where they can be coughed up and swallowed. The first symptom can be a local pruritic rash at the site of skin penetration. Cough and tracheal irritation can develop as the larvae migrate to the lungs. Coughed-up larvae that are swallowed can become adult worms in the small intestine and cause abdominal pain, diarrhea, constipation, and anorexia. Rarely, chronic infection can lead to arthritis, cardiac arrythmias, intestinal obstruction, nephrotic syndrome, and other systemic issues. People with human T-lymphotropic virus type I (HTLV-1) infection are more likely to become infected with Strongyloides and, once infected, are more likely to develop severe infection. Long-term travelers and expatriates are at greatest risk for infection; however, duration of infection can be many years or lifelong due to autoinfection. Furthermore, if a patient with subclinical strongyloidiasis becomes immunocompromised, they can develop a hyperinfection syndrome or disseminated disease that can be fatal.

Trichuriasis (Trichuris trichiura)

Trichuriasis, also known as whipworm, is considered a soil-transmitted helminth. All travelers to endemic areas are at risk of encountering soil, food, or water that is contaminated with human feces. People can suffer light or heavy infections. The heavier the infection, the more likely the infected person will experience frequent, painful bowel movements, sometimes with hematochezia. Rectal prolapse can occur.

Table 10.6.2: Parasitic causes of eosinophilia and gastrointestinal symptoms without fever

Parasitic causes of eosinophilia, fever, and pulmonary symptoms

Paragonimiasis (Paragonimus westermani, Paragonimus africanus, Paragonimus mexicanus)

Common symptoms in the acute phase include abdominal pain and fever, corresponding with the parasite penetrating the duodenal wall. Parasites can migrate to the lungs, where they cause cough, hemoptysis, and pleural effusion. Rarely, parasites can migrate to the central nervous system. All travelers to endemic areas could intentionally or accidentally ingest raw crab or crayfish and be at risk for infection.

Table 10.6.3: Parasitic causes of eosinophilia, fever, and pulmonary symptoms

Parasitic causes of eosinophilia, fever, and myositis

Muscular Sarcocystosis (Sarcocystis nesbetti)

Infection occurs when humans ingest food, water, or soil contaminated with the feces of a sporocyte-shedding reptilian host. As the parasite migrates into muscle tissues, infected individuals can experience muscle pain, edema, and fever. There are other Sarcocystis species that cause gastrointestinal disease. All travelers to endemic areas can be at risk for infection if they are exposed to feces from the host species.

Trichinellosis (Trichinella spirals)

Several animal species can be hosts to Trichinella, including pigs, rats, black and polar bears, moose, and wild boar. As the parasite migrates into muscle tissues, infected individuals can experience periorbital and facial edema, fever, myalgias, conjunctivitis, or splinter hemorrhages. This can be preceded by gastrointestinal symptoms such as diarrhea, vomiting, and abdominal pain, as well as rash. Occasionally, life-threatening myocarditis, central nervous system (CNS) involvement, and pneumonitis can occur. All travelers to endemic areas can be at risk for infection if they are exposed to raw or undercooked meat infected with the parasite.

Table 10.6.4: Parasitic causes of eosinophilia, fever, and myositis

Parasitic causes of eosinophilia with allergic or dermatologic symptoms

Anisakiasis (Pseudoterranova decipiens, Anisakis simplex)

See Parasitic Causes of Eosinophilia and Gastrointestinal Symptoms Without Fever section in this chapter.

Ascariasis (Ascaris lumbricoides)

See Parasitic Causes of Eosinophilia and Gastrointestinal Symptoms Without Fever section in this chapter.

Gnathostomiasis (Gnathostoma spinigerum)

The parasite can migrate to subcutaneous tissues, which can be associated with intermittent migratory swellings, often on the torso or upper limbs. The swellings can be erythematous, pruritic, and painful and can recur over months to years. The parasite can also migrate to deeper tissues; in these cases, symptoms are dependent on the involved organ. Neurognathostomiasis can be associated with fatal eosinophilic meningitis and myeloencephalitis. All travelers to endemic areas who are accidentally or intentionally consuming raw or undercooked freshwater fish, amphibians, or poultry are at risk of infection.

Lymphatic Filariasis (Wuchereria bancrofti, Brugia malayi, Brugia timori)

Lymphatic filariasis is caused by microscopic, thread-like worms spread from person to person by mosquitoes. Adult worms live in the human lymph vessels, mate, and produce millions of microscopic worms that over time can damage the lymphatic vessels. Only about 20%–30% of people with lymphatic filariasis will develop a long-term complication. Lymphedema, particularly of the leg(s), is the most common complication, along with hydrocele in men and, less commonly, chyluria. The presence of eosinophilia is associated with microfilaremia. Rarely, infected individuals can develop a syndrome called tropical pulmonary eosinophilia that presents with cough, shortness of breath, and wheezing. Long-term travelers and expatriates are at greatest risk of infection because infection generally requires repeated exposures.

Loaisis (Loa loa)

Loiasis, also called African eye worm, is transmitted to humans by repeated bites of deer flies that breed in the rainforests of Central and West Africa. The most common symptoms of loaisis are Calabar swellings—localized, non-tender swellings usually found on the arms and legs near joints—and visible eye worm. Skin manifestations, including pruritus or hives, as well as muscle or joint pains, can occur. It is important to know if a person has loaisis before treating for onchocerciasis or lymphatic filariasis because some of the medications (e.g., DEC, ivermectin) used to treat these conditions can cause serious and deadly reactions in a person with Loa loa co-infection. Long-term travelers and expatriates are at greatest risk of infection.

Onchocerciasis (Onchocerca volvulus)

Onchocerciasis, or river blindness, is caused by a parasitic worm transmitted through repeated bites of blackflies that live near fast-flowing streams and rivers, usually in more rural areas. Infected individuals may not experience symptoms for many months as symptoms are caused by the body's response to dead or dying larvae (microfilariae). Symptoms include pruritic skin rashes, subcutaneous nodules, and vision changes. Infection can lead to optic neuritis, corneal lesions, and blindness. Long-term travelers and expatriates living in endemic areas are at greater risk for infection as infection generally requires repeated insect bites.

Scabies (Sarcoptes scabiei var. hominis)

Scabies is caused by an infestation of the skin by a mite that burrows into the upper layer of the skin and lays eggs. The most common symptoms of scabies are pruritus and rash, particularly at night. Fingers, wrists, elbows, armpits, waist, buttocks, and genitals are commonly affected. An infested person can spread scabies even if they are asymptomatic. Long-term travelers and expatriates are at greater risk for scabies, but anyone with prolonged skin-to-skin contact with an infected person is at risk.

Schistosomiasis (Schistosoma spp.)

Refer to the Schistosomiasis chapter for further information.

Table 10.6.5: Parasitic causes of eosinophilia with allergic or dermatologic symptoms

Parasitic causes of eosinophilia, fever, and central nervous system symptoms

Angiostrongyliasis (Angiostrongylus cantonensis)

Parasites from rats infect slugs or snails. Animals that ingest snails or slugs, such as freshwater crabs, frogs, and shrimp, also carry the parasite. Infection usually presents with eosinophilic meningitis causing symptoms of headache, fever, malaise, and varying degrees of neurologic dysfunction. Humans can also acquire an ocular form of the disease, causing uveitis, blurred vision, and vision loss. Infection can be fatal. All travelers to endemic areas could intentionally or accidentally ingest raw or undercooked slugs, snails, crabs, frogs, or shrimp and be at risk for infection.

Baylisascaris (Baylisascaris procyonis)

Humans acquire the infection if they accidentally ingest infective eggs in soil or water contaminated with raccoon feces. Larvae migrate from the intestines throughout the body. Symptoms are dependent on the location of migration. The brain and spinal cord (neural larva migrans) and the eye (ocular larva migrans) can be impacted. Neural larva migrans could present with nausea, fatigue, confusion, and loss of muscle control. It is likely to produce an eosinophilic meningoencephalitis and can quickly progress to coma and death. Although rare, all travelers contacting racoon feces could be at risk, most often children or hunters and trappers.

Gnathostomiasis (Gnathostoma spinigerum)

See Parasitic Causes of Eosinophilia with Allergic or Dermatologic Symptoms section.

Table 10.6.6: Parasitic causes of eosinophilia, fever, and central nervous system symptoms

Parasitic causes of eosinophilia and urinary symptoms

Schistosomiasis (Schistosoma spp.)

Refer to the Schistosomiasis chapter for further information.

Table 10.6.7: Parasitic causes of eosinophilia and urinary symptoms

Parasitic infection without peripheral eosinophilia

Alveolar Echinococcosis (Echinococcus multilocularis)

Alveolar echinococcosis is caused by infection with the larval stage of E. multilocularis, a tapeworm found in foxes, coyotes, and dogs. Alveolar echinococcosis cases are quite rare in humans. Symptoms can take years to manifest, and the nature and severity of symptoms depend on the location and size of the lesions. The liver is the most common location, with spread occurring to the lungs and, less commonly, the brain. The larval forms of E. multilocularis do not fully mature into cysts, instead causing "tumor-like" vesicles that invade and destroy surrounding tissues, causing discomfort or pain, weight loss, and malaise. Alveolar echinococcosis is often fatal, with a mortality rate between 50% and 75%. All travelers to endemic areas are at risk of infection, most often hunters, trappers, or those living on farms.

Amebiasis (Entamoeba histolytica)

Refer to the Post-Travel Diarrhea chapter for further information.

Cryptosporidiosis (Cryptosporidium hominis, Cryptosporidium parvum)

Refer to the Post-Travel Diarrhea chapter for further information.

Cutaneous Larva Migrans (Ancylostoma caninum, Ancylostoma braziliense, Uncinaria stenocephala)

Larval stages of dog and cat hookworms can cause human skin infections. These hookworm larvae are often found in sand or soil and can lead to creeping eruption when they contact human skin. A serpiginous, erythematous track appears in the skin at the site of contact with the hookworm larva. The tracks are usually pruritic and swollen. Tracks are often found on the feet, lower legs, and buttocks but can be found anywhere that contacts contaminated soil. All travelers are at risk of infection (see the Post-Travel Dermatologic Conditions chapter).

Cyclosporiasis (Cyclospora cayetanensis)

Refer to the Post-Travel Diarrhea chapter for further information.

Cysticercosis (Taenia solium)

Transmission occurs through ingestion of eggs excreted by a human carrier of the adult T. solium tapeworm. After ingestion, eggs hatch in the intestine and access the bloodstream, where they can spread throughout the body. Once in an organ, they can mature into cysts over weeks to months. Symptoms depend on number, size, and location of cysts. Cysts can develop in the muscles, eyes, brain, or spinal cord. Cysts in the brain or spinal cord cause the most serious form of disease—neurocysticercosis—and can present with confusion, balance issues, headache, or seizure. Long-term travelers and expatriates who might accidentally contact contaminated human feces, either directly or through contaminated food, are at greatest risk of infection.

Giardiasis (Giardia duodenalis)

Refer to the Post-Travel Diarrhea chapter for further information.

Leishmaniasis (Leishmania spp.)

Refer to the Leishmaniasis chapter for further information.

Malaria (Plasmodium spp.)

Refer to the Malaria chapter for further information.

Pinworm (Enterobius vermicularis)

Enterobiasis is also known as pinworm infection. Pinworm eggs deposit on human perianal folds and infect via self-inoculation (hand-to-mouth contact after scratching infected area) and close person-to-person contact. The most common symptom is perianal itching, especially at night, which can lead to excoriations and bacterial superinfection. Adult worms may be visible near the anus within 2–3 hours of self-inoculation or close person-to-person contact. All travelers to endemic areas are at risk of infection, especially if in close contact with children.

Taeniasis (Taenia saginata, Taenia solium)

Taeniasis is acquired after ingesting larval tapeworms in contaminated raw or undercooked beef (T. saginata) or pork (T. solium). Symptoms typically include abdominal pain, anorexia, diarrhea, nausea, insomnia, anxiety, and perianal pruritus. All travelers to endemic areas who may accidentally or intentionally ingest contaminated raw or undercooked beef or pork may be at risk for infection.

Toxoplasmosis (Toxoplasma gondii)

Toxoplasmosis is a common cause of foodborne infection globally. All travelers could accidentally or intentionally ingest contaminated food, soil, water, raw or undercooked meat or shellfish and be at risk for infection. T. gondii can also be transmitted congenitally if a woman is infected during or shortly before pregnancy. Symptoms are typically influenza-like with prolonged fever, elevated liver enzymes, lymphadenopathy, and lymphocytosis. Infants with congenital toxoplasmosis can display visual and cognitive impairments.

Trypanosomiasis, African (Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense)

Trypanosomiasis is transmitted by the bite of an infected tsetse fly. It is endemic in specific areas of Sub-Saharan Africa. A map of at-risk areas can be found here: WHO | World Health Organization. Tsetse flies inhabit rural forests and savannahs with a particular affinity for thick vegetation near water sources. Symptoms of T. rhodesiense can include chancre at the bite site, high fever, headache, myalgia, skin rash, and thrombocytopenia. CNS involvement can occur within a few weeks of exposure and result in disturbed sleep-wake cycle, confusion, and, if untreated, death within months. Symptoms of T. gambiense usually do not appear until months to years after exposure and can include arthralgia, facial edema, fever, headache, lymphadenopathy, or pruritus. CNS involvement occurs after months to years and is characterized by sleep-wake cycle disturbance and other neurologic changes. T. gambiense progresses more slowly but can lead to death if left untreated. Long-term travelers and expatriates are at greatest risk for infection.

Trypanosomiasis, American (Trypanosoma cruzi)

Human infection occurs when the feces of an infected triatomine insect enters the body, often at a break in the skin from an insect bite. Acute illness can be characterized by a chagoma (indurated swelling) at the site of infection. If the portal of entry was the conjunctiva, unilateral bipalpebral swelling can result (Romaña's sign). Of those acutely infected, 20%–30% will develop chronic manifestations years later, including cardiac arrythmia and gastrointestinal problems. Long-term travelers and expatriates in Latin American regions are at greatest risk because they are more likely to be in contact with the insect's environment.

Table 10.6.8: Parasitic infection without peripheral eosinophilia