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Gastrointestinal (GI S/S are often interrelated, hence it will be wise to see all categories of GI S/S. Also, see the separate file on Worms) Abdominal Pain, Nausea & Vomiting, Acute Diarrhea, Chronic Diarrhea, Intestinal Obstruction, Liver/Spleen Disorders/Organomegaly/Jaundice.
Amebiasis: See full discussion (Worldwide): Amebiasis is an amebic gastrointestinal infection (sometimes affecting other systems) that may be asymptomatic, chronic, or acute. Symptoms may include abdominal pain, diarrhea (with blood), weight loss, dehydration. Systemic dissemination is usually to the liver, but may also involve the brain, heart (pericarditis), lungs, and genitalia. Invasive amebiasis is treated with metronidazole and colonization without symptoms is treated with paromomycin or iodoquinol.
Anisakiasis (Mexico, Central and South America, Japan): Anisakiasis is a nematode (roundworm) infection of the stomach or intestinal wall with Anisakis. Manifestions vary according to primary site of infection and improvement usually occurs within a few weeks. Acute gastric anisakiasis has an acute onset of progressive epigastric pain, nausea, and vomiting within hours of ingesting lavae. Acute intestinal manifests as low-grade fever, colicky lower (or diffuse) abdominal pain, nausea, vomiting, and diarrhea. Chronic anisakiasis produces chronic symptoms similar to gastritis, peptic ulcer disease, inflammatory bowel disease, and other GI disorders. Treatment is symptomatic, and in a few cases, surgical.
Ascariasis: See full discussion (Worldwide): Ascariasis is a nematode or roundworm infection with Ascaris lumbricoides causing transient respiratory symptoms initially and chronic gastrointestinal symptoms. The adult worms are more than 20 cm. in length, hence are easily seen in stool and may also emerge from the nose or mouth as a result of coughing or vomiting. Treatment is with albendazole single dose of 400 mg po (not FDA approved) or mebendazole or pyrantel pamoate.
Giardiasis: See full discussion (Worldwide): Giardiasis or giardia is caused Giardia lamblia, a protozoan transmitted via water or food contaminated with human feces; and is also transmitted sexually (usually anal-oral). Many infected persons are asymptomatic, while others experience diarrhea as the primary symptom. Diarrhea ranges from one loose stool/day to frequent copious watery stools, may be acute or chronic, and continuous or intermittent (with bouts of constipation). When copious, stools often contain mucous, but seldom blood, and are greasy/steatorrheic, frothy and foul-smelling. Other common symptoms are abdominal pain, nausea and vomiting, anorexia, flatulence, fatigue, and weight loss. The acute phase may last days or weeks, with resolution usually spontaneous. Some patients develop chronic giardiasis, which persists for many years. Metronidazole 250 mg. tid x 5 days is a common treatment. Alternatives include furazolidone, albendazole, and paramomycin. Empiric treatment is common.
Hymenolepiasis (Americas, Mediterranean, Near East, India, Australia): Hymenolepsis nana is the smallest and most common tapeworm (cestode) parasitizing humans. H. nana is spread by the fecal-oral route and is especially common in institutions. Most infected persons are asymptomatic, but very high loads may produce anorexia, abdominal pain, and diarrhea. Treatment is with praziquantel 25 mg/kg in one po dose.
Salmonellosis (Worldwide): Salmonella sp. infections are well known in the Western world. In addition to the usual mild GI Salmonella sp. infections (more severe in the elderly), the more virulent Salmonella typhi causes typhoid fever.
Schistosomiasis or Bilharzia: See full discussion (Numerous areas of the world, especially Africa and Asia with variants and locations noted in the full discussion). Schistosomiasis is caused by Schistosoma sp. and encompasses several syndromes, not all of which are evident in all infected persons. Initial symptoms may include a pruritic, papular rash - most commonly in persons who do not live in endemic areas. Acute schistosomiasis (Katayama fever) occurs in primary infection 1-2 months after exposure to heavy parasite loads. Symptoms may include fever of several weeks duration, headache, urticaria, cough, hepatosplenomegaly, lymphadenopathy, diarrhea, and eosinophilia. Hematuria and dysuria occur in some infections. Symptoms tend to gradually diminish over several months, but may intensify as more eggs are deposited. Chronic hepatosplenic schistosomiasis is a consequence of eggs retained in tissue and prolonged infection - usually > 10 years duration. The liver may be large or small and firm with nodularity. Portal hypertension, splenomegaly, or esophageal or gastric varices may occur. Hematemesis and splenomegaly are common presenting symptoms, with normal liver function. Periportal fibrosis and portal hypertension is associated with glomerulonephritis (proteinuria, renal failure) and pulmonary hypertension (cor pulmonale). Granulomatous tissue in the bowel results in bloody diarrhea. The last (chronic) stage varies according to species, with some species primarily affecting the liver and intestines, and one species affecting primarily the urinary tract. In general, patients with chronic schistosomiasis tend to present in developed countries with lethargy, colicky abdominal pain, mucoid/bloody diarrhea, or dysuria and hematuria. Salmonella infection concurrent with schistosomiasis is common and is resistant to treatment unless the schistosomiasis is also treated. Complications include progression of liver, kidney, or other organ dysfunction for many years after transmission has been interrupted - especially with heavy infection and re-exposure. Central nervous system lesions occur, but rarely. Treatment is according to species: For S. haematobium and S. mansoni, praziquantel 20/kg po bid for one day; for S. japonica and S. mekongi, praziquantel 20/kg po tid for one day are the treatments of choice. S. mansoni may also be treated with oxamniquine in a single po dose (with food) of 15 mg/kg. S. haematobium in North and East Africa may be treated with metrifonate 7.5-10 mg/kg every other week for a total of 3 doses.
Strongylodiasis (Most of the tropical world): Strongylodiasis is a nematode (roundworm) infection by Strongyloides stercoralis following larval penetration of the skin. A minority of infected persons are asymptomatic. Cutaneous manifestions may occur at the site of penetration (often feet), and include inflammation, serpiginous or urticarial tracts, and pruritis. Intestinal manifestations follow cutaneous, and include abdominal pain, nausea, flatulence, and diarrhea. Larval migration to lungs results in a variety of pulmonary symptoms, ranging from cough to pneumonia, pleural effusion, and miliary abscesses. Hyperinfection syndrome causes life-threatening CNS, cardiac, and wide-ranging gastrointestinal problems. Treatment is with ivermectin 200 mcg/kg/day po for two days. Albendazole and thiabendazole have also been used.
Tapeworms and cysticercosis (Worldwide, but endemic in certain areas): Tapeworm or cestode infections result from the ingestion of Taeniasis sp. eggs, often found in undercooked meat or excreted proglottids (segments) of the adult tapeworm. Depending on the species, adult tapeworms reach a length of eight meters and live as long as 25 years. The beef tapeworm (Taeniasis saginata) usually causes gastrointestinal discomfort and weight loss. Awareness of infection often is through discovery of proglottids in the stool. Manifestations of intestinal infection with the pork tapeworm (Taeniasis solium) are similar to those of the beef tapeworm. However, ingestion of food that is fecally contaminated with T. solium eggs results in cysticercosis. The symptoms of cysticercosis are caused by the presence of cysticeri (encapsulated larvae) and the resulting inflammatory reaction or space-occupying lesions. The incubation period is as long as five years. Manifestions are most commonly varied neurologic problems, including fever, headache, CVA, hydrocephalus, seizures, and other symptoms of increased intracranial pressure. Visual manifestations may be from increased intracranial pressure or a cyst in the eye. Cysts are also found in subcutaneous and muscle tissue. Treatment of intestinal tapeworms is with a single dose of praziquantel 5-10 mg/kg. Treatment of cysticercosis is with albendazole 5 mg/kg po tid for 8-30 days or praziquantel 20 mg/kg po tid for 14 days. Therapy may increase symptoms, in which case dexamethasone helps reduce distress. Also see echinococcosis and hymenolepiasis.
Trematodes (flukes): See schistosomiasis above or full discussion and see trematode infection, liver below. Trematodes, biliary duct-dwelling cause diseases including clonorchiasis and opisthorchiasis. (1) Clonorchiasis (China, Taiwan, Korea, Japan, Vietnam, and other areas of Asia) is a liver fluke (Clonorchis sinensis) infection of the biliary tract following ingestion of raw or pickled fish. Symptoms include upper abdominal pain, irregular high fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day. (2) Opisthorchiasis (Eastern Europe and Russia; Thailand) is a liver fluke infection of the biliary tract following ingestion of raw or pickled fish. Most infected persons have no significant symptoms. If the parasite load is high, symptoms may include upper abdominal pain, feeling that something is moving in the liver, hepatomegaly with tenderness, jaundice, intermittent fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day.
Trematodes, liver-dwelling cause fascioliasis (Worldwide where sheep and cattle are raised): Infection occurs after ingestion of contaminated water or water-dwelling vegetation, e.g., watercress. Acute fascioliasis is characterized by fever, abdominal pain (especially hepatic), nausea, diarrhea, and hepatomegaly. Cough may also occur. Liver enzymes and erythrocyte sedimentation rates are usually elevated, and anemia is common. Chronic disease results in a variety liver and gallbladder abnormalities. Bithionol 30-50 mg/kg orally qod for 10-15 doses is the treatment of choice as this is written. Bithionol is available in the U.S. from CDC. Triclabendazole in a single dose of 10 mg/kg may become the drug of choice when available in the U.S. (Rosenblatt, 1999).
Tapeworms and cysticercosis (Worldwide, but endemic in certain areas): Tapeworm or cestode infections result from the ingestion of Taeniasis sp. eggs, often found in undercooked meat or excreted proglottids (segments) of the adult tapeworm. Depending on the species, adult tapeworms reach a length of eight meters and live as long as 25 years. The beef tapeworm (Taeniasis saginata) usually causes gastrointestinal discomfort and weight loss. Awareness of infection often is through discovery of proglottids in the stool. Manifestations of intestinal infection with the pork tapeworm (Taeniasis solium) are similar to those of the beef tapeworm. However, ingestion of food that is fecally contaminated with T. solium eggs results in cysticercosis. The symptoms of cysticercosis are caused by the presence of cysticeri (encapsulated larvae) and the resulting inflammatory reaction or space-occupying lesions. The incubation period is as long as five years. Manifestions are most commonly varied neurologic problems, including fever, headache, CVA, hydrocephalus, seizures, and other symptoms of increased intracranial pressure. Visual manifestations may be from increased intracranial pressure or a cyst in the eye. Cysts are also found in subcutaneous and muscle tissue. Treatment of intestinal tapeworms is with a single dose of praziquantel 5-10 mg/kg. Treatment of cysticercosis is with albendazole 5 mg/kg po tid for 8-30 days or praziquantel 20 mg/kg po tid for 14 days. Therapy may increase symptoms, in which case dexamethasone helps reduce distress. Also see echinococcosis and hymenolepiasis.
Trichuriasis (trichocephaliasis or whipworm) (Worldwide, especially tropical and subtropical areas): Trichuriasis is a nematode (roundworm) infection with Trichuris trichiura. Heavy infections may result in abdominal cramping, nausea, vomiting, flatulence, diarrhea, tenesmus, and weight loss. Mild infections are usually asymptomatic. Treatment is with albendazole single po dose of 400 mg (not FDA approved) or mebendazole 100 mg po bid for 3 days. Ivermectin is sometimes also used in combination with albendazole.
Nausea and Vomiting (Nausea and some vomiting are common features of many GI infections)
Amebiasis: See full discussion (Worldwide): Amebiasis is an amebic gastrointestinal infection (sometimes affecting other systems) that may be asymptomatic, chronic, or acute. Symptoms may include abdominal pain, diarrhea (with blood), weight loss, dehydration. Systemic dissemination is usually to the liver, but may also involve the brain, heart (pericarditis), lungs, and genitalia. Invasive amebiasis is treated with metronidazole and colonization without symptoms is treated with paromomycin or iodoquinol.
Ascariasis: See full discussion (Worldwide): Ascariasis is a nematode or roundworm infection with Ascaris lumbricoides causing transient respiratory symptoms initially and chronic gastrointestinal symptoms. The adult worms are more than 20 cm. in length, hence are easily seen in stool and may also emerge from the nose or mouth as a result of coughing or vomiting. Treatment is with albendazole single dose of 400 mg po (not FDA approved) or mebendazole or pyrantel pamoate.
Bacillus cereus (Worldwide): Bacillus cereus is a pathogen causing self-limited food poisoning with vomiting or diarrhea.
Giardiasis: See full discussion (Worldwide): Giardiasis or giardia is caused Giardia lamblia, a protozoan transmitted via water or food contaminated with human feces; and is also transmitted sexually (usually anal-oral). Many infected persons are asymptomatic, while others experience diarrhea as the primary symptom. Diarrhea ranges from one loose stool/day to frequent copious watery stools, may be acute or chronic, and continuous or intermittent (with bouts of constipation). When copious, stools often contain mucous, but seldom blood, and are greasy/steatorrheic, frothy and foul-smelling. Other common symptoms are abdominal pain, nausea and vomiting, anorexia, flatulence, fatigue, and weight loss. The acute phase may last days or weeks, with resolution usually spontaneous. Some patients develop chronic giardiasis, which persists for many years. Metronidazole 250 mg. tid x 5 days is a common treatment. Alternatives include furazolidone, albendazole, and paramomycin. Empiric treatment is common.
Leishmaniasis: See full discussion or brief discussions of the various types (visceral, cutaneous, mucocutaneous) (East and North Africa, Middle East, Southern Europe, Central, South, and East Asia, South America, West Mexico): The protozoal parasite species Leishmania is transmitted by sandflies. Major types of leishmaniasis include visceral leishmaniasis or kala-azar, cutaneous leishmaniasis, and mucocutaneous leishmaniasis (espundia). Incubation is usually 2-6 months or longer and relapse may occur as many as 10 years after first episode. Signs and symptoms vary according to the type of leishmaniasis. See visceral leishmaniasis, cutaneous leishmaniasis, and mucocutaneous leishmaniasis (espundia).
Rotavirus (Worldwide): Rotavirus noninflammatory diarrhea is the most common cause of dehydrating diarrhea in children worldwide. Rotavirus gastroenteritis is more severe in children than adults. Treatment is supportive.
Staphylococcus aureus infection (Worldwide): S. aureus produces an eneterotoxin that causes an acute and short-lived gastroenteritis, for which treatment is supportive.
Tapeworms and cysticercosis (Worldwide, but endemic in certain areas): Tapeworm or cestode infections result from the ingestion of Taeniasis sp. eggs, often found in undercooked meat or excreted proglottids (segments) of the adult tapeworm. Depending on the species, adult tapeworms reach a length of eight meters and live as long as 25 years. The beef tapeworm (Taeniasis saginata) usually causes gastrointestinal discomfort and weight loss. Awareness of infection often is through discovery of proglottids in the stool. Manifestations of intestinal infection with the pork tapeworm (Taeniasis solium) are similar to those of the beef tapeworm. However, ingestion of food that is fecally contaminated with T. solium eggs results in cysticercosis. The symptoms of cysticercosis are caused by the presence of cysticeri (encapsulated larvae) and the resulting inflammatory reaction or space-occupying lesions. The incubation period is as long as five years. Manifestions are most commonly varied neurologic problems, including fever, headache, CVA, hydrocephalus, seizures, and other symptoms of increased intracranial pressure. Visual manifestations may be from increased intracranial pressure or a cyst in the eye. Cysts are also found in subcutaneous and muscle tissue. Treatment of intestinal tapeworms is with a single dose of praziquantel 5-10 mg/kg. Treatment of cysticercosis is with albendazole 5 mg/kg po tid for 8-30 days or praziquantel 20 mg/kg po tid for 14 days. Therapy may increase symptoms, in which case dexamethasone helps reduce distress. Also see echinococcosis and hymenolepiasis.
Trichinosis (trichinella) (Worldwide): Trichinosis is a nematode (roundworm) infection with Trichinella sp. from ingestion of meat that contains cysts, especially undercooked pork or meat from a carnivore. Infection ranges from light and asymptomatic to heavy and life-threatening. Manifestations vary according to the life cycle of the worms: Initially there is malaise, nausea, cramping abdominal pain, and diarrhea. Gastrointestinal symptoms are followed in 1-6 weeks by fever, eosinophilia, periorbital and facial edema, conjunctivitis, dysphagia, dyspnea, cough, myalgia, and muscle spasms. Complications include meningitis and other neurological disorders, myocarditis, pneumonia, and nephritis. The current treatment of choice is mebendazole 300 mg po tid for 10 days (sometimes with prednisone to control symptoms).
Trichuriasis (trichocephaliasis or whipworm) (Worldwide, especially tropical and subtropical areas): Trichuriasis is a nematode (roundworm) infection with Trichuris trichiura. Heavy infections may result in abdominal cramping, nausea, vomiting, flatulence, diarrhea, tenesmus, and weight loss. Mild infections are usually asymptomatic. Treatment is with albendazole single po dose of 400 mg (not FDA approved) or mebendazole 100 mg po bid for 3 days. Ivermectin is sometimes also used in combination with albendazole.
Amebiasis: See full discussion (Worldwide): Amebiasis is an amebic gastrointestinal infection (sometimes affecting other systems) that may be asymptomatic, chronic, or acute. Symptoms may include abdominal pain, diarrhea (with blood), weight loss, dehydration. Systemic dissemination is usually to the liver, but may also involve the brain, heart (pericarditis), lungs, and genitalia. Invasive amebiasis is treated with metronidazole and colonization without symptoms is treated with paromomycin or iodoquinol.
Bacillus cereus (Worldwide): Bacillus cereus is a pathogen causing self-limited food poisoning with vomiting or diarrhea and abdominal cramps.
Campylobacter enteritis (Worldwide): Campylobacter enteritis is caused by gram negative non-spore forming rods (Campylobacter sp.) resulting in acute gastroenteritis characterized by fever, abdominal pain, and acute watery (sometimes bloody) diarrhea . Campylobacter fetus causes systemic infections that are sometimes fatal.
Cholera (Southeast Asia, India, Middle East, East and North Africa): Cholera is an endemic and epidemic acute Vibrio cholera (bacterial) infection transmitted via feces or vomitus-contaminated water. Raw or under-cooked seafood may also be contaminated and result in cholera infection. The incubation period is 1-5 days. Most infections are subclinical, but 10% or fewer infected persons experience sudden and explosive diarrhea (first fecal, then watery and mucous-flecked), vomiting, and prostration leading rapidly to fluid and electrolyte depletion, metabolic acidosis, shock, renal failure, and death. Rehydration (Ringer's lactate initially for severe cases, then oral rehydration therapy; or in milder cases, oral rehydration therapy throughout) is critical. After vomiting ends, the duration of symptoms is shortened by tetracycline 500 mg po qid for 3 days or furazolidone 400 mg daily for 3 days or a single dose of 300 mg doxycycline.
Clostridium botulinum and C. perfringens (Worldwide): C. botulinum causes botulism (see above) and C. perfringens causes gas gangrene and also enteritis or food poisoning especially from poultry.
Escherichia coli (Woldwide): E. coli are gram negative motile or nonmotile short rods that are a common cause of urinary tract and epidemic diarrheal diseases.
Rotavirus (Worldwide): Rotavirus noninflammatory diarrhea is the most common cause of dehydrating diarrhea in children worldwide. Rotavirus gastroenteritis is more severe in children than adults. Treatment is supportive.
Salmonellosis (Worldwide): Salmonella sp. infections are well known in the Western world. In addition to the usual mild GI Salmonella sp. infections (more severe in the elderly), the more virulent Salmonella typhi causes typhoid fever.
Shigellosis or bacillary dysentary (Worldwide): Acute diarrheal illness from Shigella sp. transmitted via fecal-oral route. Shigellosis is especially common in children. Treatment is supportive and focused on prevention of dehydration.
Staphylococcus aureus infection (Worldwide): S. aureus produces an eneterotoxin that causes an acute and short-lived gastroenteritis, for which treatment is supportive.
Trichuriasis (trichocephaliasis or whipworm) (Worldwide, especially tropical and subtropical areas): Trichuriasis is a nematode (roundworm) infection with Trichuris trichiura. Heavy infections may result in abdominal cramping, nausea, vomiting, flatulence, diarrhea, tenesmus, and weight loss. Mild infections are usually asymptomatic. Treatment is with albendazole single po dose of 400 mg (not FDA approved) or mebendazole 100 mg po bid for 3 days. Ivermectin is sometimes also used in combination with albendazole.
Vibrio parahaemolyticus and other vibrio species (worldwide): Vibrio are motile, anaerobic, curved, gram-negative rods that cause (according to species) gastrointestinal (notably cholera) and septic illnesses; and wound, skin, and opthalmic infections. In the U.S., Vibrio parahaemolyticus is transmitted by ingestion of undercooked seafood. In the U.S., infection results in abdominal pain, nausea, vomiting, and watery diarrhea; while in South Asia, infection causes more serious dysentery, but is seldom life-threatening. Treatment is supportive.
Amebiasis: See full discussion (Worldwide): Amebiasis is an amebic gastrointestinal infection (sometimes affecting other systems) that may be asymptomatic, chronic, or acute. Symptoms may include abdominal pain, diarrhea (with blood), weight loss, dehydration. Systemic dissemination is usually to the liver, but may also involve the brain, heart (pericarditis), lungs, and genitalia. Invasive amebiasis is treated with metronidazole and colonization without symptoms is treated with paromomycin or iodoquinol.
Clonorchiasis (China, Taiwan, Korea, Japan, Vietnam, and other areas of Asia) is a liver fluke (Clonorchis sinensis) infection of the biliary tract following ingestion of raw or pickled fish. Symptoms include upper abdominal pain, irregular high fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day.
Cryptosporidiosis (Worldwide, with increased prevalence in tropical areas): Cryptosporidiosis is a protozoan (Cryptosporidium sp.) infection of the GI tract causing diarrhea which ranges from self-limited to chronic secretory, high volume and ultimately fatal. Immunocompromised persons are at increased risk. There is not currently a satisfactory treatment.
Giardiasis: See full discussion (Worldwide): Giardiasis or giardia is caused Giardia lamblia, a protozoan transmitted via water or food contaminated with human feces; and is also transmitted sexually (usually anal-oral). Many infected persons are asymptomatic, while others experience diarrhea as the primary symptom. Diarrhea ranges from one loose stool/day to frequent copious watery stools, may be acute or chronic, and continuous or intermittent (with bouts of constipation). When copious, stools often contain mucous, but seldom blood, and are greasy/steatorrheic, frothy and foul-smelling. Other common symptoms are abdominal pain, nausea and vomiting, anorexia, flatulence, fatigue, and weight loss. The acute phase may last days or weeks, with resolution usually spontaneous. Some patients develop chronic giardiasis, which persists for many years. Metronidazole 250 mg. tid x 5 days is a common treatment. Alternatives include furazolidone, albendazole, and paramomycin. Empiric treatment is common.
HIV/AIDS: HIV/AIDS is found world-wide, and is especially common in sub-Saharan Africa, Southeast Asia, and India. Heterosexual transmission is common in these areas. Readers are referred to the CDC and other current sources of information (See links).
Hookworm: See full discussion (Most tropical and subtropical areas of the world). An important cause of anemia, hookworms are intestinal parasites (nematodes, including Ancylostoma duodenale, Unicinaria stenocephala, and Necator americanus) whose larvae are transmitted from soil through the skin. Incubation is 2-8 weeks. Most people (with small parasite loads) are asymptomatic. Entry points are sometimes pruritic. Higher loads result in anorexia or increased appetite, abdominal discomfort, weight loss, nausea and vomiting, diarrhea and/or constipation, and anemia. Respiratory symptoms occur in a few patients. Infants and children may experience severe anemia, protein deficiency, and developmental delays. Treatment is with mebendazole, albendazole, or pyrantel pamoate. None of these are safe in pregnancy and neither mebendazole nor albendazole should be given to children under 1 year of age. The anemia should be treated with ferrous sulfate.
Hymenolepiasis (Americas, Mediterranean, Near East, India, Australia): Hymenolepsis nana is the smallest and most common tapeworm (cestode) parasitizing humans. H. nana is spread by the fecal-oral route and is especially common in institutions. Most infected persons are asymptomatic, but very high loads may produce anorexia, abdominal pain, and diarrhea. Treatment is with praziquantel 25 mg/kg in one po dose.
Leishmaniasis: See visceral leishmaniasis below
Schistosomiasis or Bilharzia: See full discussion (Numerous areas of the world, especially Africa and Asia with variants and locations noted in the full discussion). Schistosomiasis is caused by Schistosoma sp. and encompasses several syndromes, not all of which are evident in all infected persons. Initial symptoms may include a pruritic, papular rash - most commonly in persons who do not live in endemic areas. Acute schistosomiasis (Katayama fever) occurs in primary infection 1-2 months after exposure to heavy parasite loads. Symptoms may include fever of several weeks duration, headache, urticaria, cough, hepatosplenomegaly, lymphadenopathy, diarrhea, and eosinophilia. Hematuria and dysuria occur in some infections. Symptoms tend to gradually diminish over several months, but may intensify as more eggs are deposited. Chronic hepatosplenic schistosomiasis is a consequence of eggs retained in tissue and prolonged infection - usually > 10 years duration. The liver may be large or small and firm with nodularity. Portal hypertension, splenomegaly, or esophageal or gastric varices may occur. Hematemesis and splenomegaly are common presenting symptoms, with normal liver function. Periportal fibrosis and portal hypertension is associated with glomerulonephritis (proteinuria, renal failure) and pulmonary hypertension (cor pulmonale). Granulomatous tissue in the bowel results in bloody diarrhea. The last (chronic) stage varies according to species, with some species primarily affecting the liver and intestines, and one species affecting primarily the urinary tract. In general, patients with chronic schistosomiasis tend to present in developed countries with lethargy, colicky abdominal pain, mucoid/bloody diarrhea, or dysuria and hematuria. Salmonella infection concurrent with schistosomiasis is common and is resistant to treatment unless the schistosomiasis is also treated. Complications include progression of liver, kidney, or other organ dysfunction for many years after transmission has been interrupted - especially with heavy infection and re-exposure. Central nervous system lesions occur, but rarely. Treatment is according to species: For S. haematobium and S. mansoni, praziquantel 20/kg po bid for one day; for S. japonica and S. mekongi, praziquantel 20/kg po tid for one day are the treatments of choice. S. mansoni may also be treated with oxamniquine in a single po dose (with food) of 15 mg/kg. S. haematobium in North and East Africa may be treated with metrifonate 7.5-10 mg/kg every other week for a total of 3 doses.
Strongylodiasis (Most of the tropical world): Strongylodiasis is a nematode (roundworm) infection by Strongyloides stercoralis following larval penetration of the skin. A minority of infected persons are asymptomatic. Cutaneous manifestions may occur at the site of penetration (often feet), and include inflammation, serpiginous or urticarial tracts, and pruritis. Intestinal manifestations follow cutaneous, and include abdominal pain, nausea, flatulence, and diarrhea. Larval migration to lungs results in a variety of pulmonary symptoms, ranging from cough to pneumonia, pleural effusion, and miliary abscesses. Hyperinfection syndrome causes life-threatening CNS, cardiac, and wide-ranging gastrointestinal problems. Treatment is with ivermectin 200 mcg/kg/day po for two days. Albendazole and thiabendazole have also been used.
Tapeworms and cysticercosis (Worldwide, but endemic in certain areas): Tapeworm or cestode infections result from the ingestion of Taeniasis sp. eggs, often found in undercooked meat or excreted proglottids (segments) of the adult tapeworm. Depending on the species, adult tapeworms reach a length of eight meters and live as long as 25 years. The beef tapeworm (Taeniasis saginata) usually causes gastrointestinal discomfort and weight loss. Awareness of infection often is through discovery of proglottids in the stool. Manifestations of intestinal infection with the pork tapeworm (Taeniasis solium) are similar to those of the beef tapeworm. However, ingestion of food that is fecally contaminated with T. solium eggs results in cysticercosis. The symptoms of cysticercosis are caused by the presence of cysticeri (encapsulated larvae) and the resulting inflammatory reaction or space-occupying lesions. The incubation period is as long as five years. Manifestions are most commonly varied neurologic problems, including fever, headache, CVA, hydrocephalus, seizures, and other symptoms of increased intracranial pressure. Visual manifestations may be from increased intracranial pressure or a cyst in the eye. Cysts are also found in subcutaneous and muscle tissue. Treatment of intestinal tapeworms is with a single dose of praziquantel 5-10 mg/kg. Treatment of cysticercosis is with albendazole 5 mg/kg po tid for 8-30 days or praziquantel 20 mg/kg po tid for 14 days. Therapy may increase symptoms, in which case dexamethasone helps reduce distress. Also see echinococcosis and hymenolepiasis.
Trematodes, liver-dwelling cause fascioliasis (Worldwide where sheep and cattle are raised): Infection occurs after ingestion of contaminated water or water-dwelling vegetation, e.g., watercress. Acute fascioliasis is characterized by fever, abdominal pain (especially hepatic), nausea, diarrhea, and hepatomegaly. Cough may also occur. Liver enzymes and erythrocyte sedimentation rates are usually elevated, and anemia is common. Chronic disease results in a variety liver and gallbladder abnormalities. Bithionol 30-50 mg/kg orally qod for 10-15 doses is the treatment of choice as this is written. Bithionol is available in the U.S. from CDC. Triclabendazole in a single dose of 10 mg/kg may become the drug of choice when available in the U.S. (Rosenblatt, 1999).
Trichinosis (trichinella) (Worldwide): Trichinosis is a nematode (roundworm) infection with Trichinella sp. from ingestion of meat that contains cysts, especially undercooked pork or meat from a carnivore. Infection ranges from light and asymptomatic to heavy and life-threatening. Manifestations vary according to the life cycle of the worms: Initially there is malaise, nausea, cramping abdominal pain, and diarrhea. Gastrointestinal symptoms are followed in 1-6 weeks by fever, eosinophilia, periorbital and facial edema, conjunctivitis, dysphagia, dyspnea, cough, myalgia, and muscle spasms. Complications include meningitis and other neurological disorders, myocarditis, pneumonia, and nephritis. The current treatment of choice is mebendazole 300 mg po tid for 10 days (sometimes with prednisone to control symptoms).
Trichuriasis (trichocephaliasis or whipworm) (Worldwide, especially tropical and subtropical areas): Trichuriasis is a nematode (roundworm) infection with Trichuris trichiura. Heavy infections may result in abdominal cramping, nausea, vomiting, flatulence, diarrhea, tenesmus, and weight loss. Mild infections are usually asymptomatic. Treatment is with albendazole single po dose of 400 mg (not FDA approved) or mebendazole 100 mg po bid for 3 days. Ivermectin is sometimes also used in combination with albendazole.
Tropical sprue (Tropical areas of the world): Tropical sprue is a malabsorption disorder of unknown etiology (possibly coliform organisms) that affects residents of or visitors to endemic or epidemic areas. Note that the disorder may occur years after leaving the tropics. Common manifestations are anorexia, abdominal distension, weight loss, and other findings consistent with malabsorption disorders; and decreased iron, folate, and B12. Treatment is with folate, B12, and 2-4 weeks of antibiotic therapy (sulfonamide or tetracycline with folic acid).
Visceral leishmaniasis (kala-azar): See full discussion (East and North Africa, Middle East, Southern Europe, Central, South, and East Asia, South America, West Mexico): Cardinal signs of visceral leishmaniasis are prolonged fever, splenomegaly, anemia, leukopenia, or hypergammaglobulinemia. A cutaneous nodule may or may not appear at the site of the bite. Systemic symptoms include gradual onset fever that often rises and falls twice/day, fatigue, weight loss, dizziness, cough, and diarrhea. Visceral manifestations include pronounced splenomegaly (hard, non-tender) and to a lesser extent hepatomegaly. Other manifestations may include generalized lymphadenopathy; hyperpigmented skin of the forehead, abdomen, hands, and feet in light-skinned persons; skin lesions in dark-skinned persons; signs of bleeding (petechiae, epistaxis, bleeding gums); jaundice and ascites; and progressive wasting. Onset may also be acute, with the above manifestations appearing a few weeks after infection. Treatment has traditionally been unsatisfactory because of drug toxicities, poor responses, multiple disease syndromes, and other factors - including recently, the emergence of antimony-resistant strains. Orally administered miltefosine has recently shown great promise. Other treatments include intravenous sodium stibogluconate (a pentavalent antimony compound) for 10-60 days depending on where the disease was contracted and whether illness is first or second episode.
Ascariasis: See full discussion (Worldwide): Ascariasis is a nematode or roundworm infection with Ascaris lumbricoides causing transient respiratory symptoms initially and chronic gastrointestinal symptoms. The adult worms are more than 20 cm. in length, hence are easily seen in stool and may also emerge from the nose or mouth as a result of coughing or vomiting. Treatment is with albendazole single dose of 400 mg po (not FDA approved) or mebendazole or pyrantel pamoate.
Strongylodiasis (Most of the tropical world): Strongylodiasis is a nematode (roundworm) infection by Strongyloides stercoralis following larval penetration of the skin. A minority of infected persons are asymptomatic. Cutaneous manifestions may occur at the site of penetration (often feet), and include inflammation, serpiginous or urticarial tracts, and pruritis. Intestinal manifestations follow cutaneous, and include abdominal pain, nausea, flatulence, and diarrhea. Larval migration to lungs results in a variety of pulmonary symptoms, ranging from cough to pneumonia, pleural effusion, and miliary abscesses. Hyperinfection syndrome causes life-threatening CNS, cardiac, and wide-ranging gastrointestinal problems. Treatment is with ivermectin 200 mcg/kg/day po for two days. Albendazole and thiabendazole have also been used.
Tapeworms and cysticercosis (Worldwide, but endemic in certain areas): Tapeworm or cestode infections result from the ingestion of Taeniasis sp. eggs, often found in undercooked meat or excreted proglottids (segments) of the adult tapeworm. Depending on the species, adult tapeworms reach a length of eight meters and live as long as 25 years. The beef tapeworm (Taeniasis saginata) usually causes gastrointestinal discomfort and weight loss. Awareness of infection often is through discovery of proglottids in the stool. Manifestations of intestinal infection with the pork tapeworm (Taeniasis solium) are similar to those of the beef tapeworm. However, ingestion of food that is fecally contaminated with T. solium eggs results in cysticercosis. The symptoms of cysticercosis are caused by the presence of cysticeri (encapsulated larvae) and the resulting inflammatory reaction or space-occupying lesions. The incubation period is as long as five years. Manifestions are most commonly varied neurologic problems, including fever, headache, CVA, hydrocephalus, seizures, and other symptoms of increased intracranial pressure. Visual manifestations may be from increased intracranial pressure or a cyst in the eye. Cysts are also found in subcutaneous and muscle tissue. Treatment of intestinal tapeworms is with a single dose of praziquantel 5-10 mg/kg. Treatment of cysticercosis is with albendazole 5 mg/kg po tid for 8-30 days or praziquantel 20 mg/kg po tid for 14 days. Therapy may increase symptoms, in which case dexamethasone helps reduce distress. Also see echinococcosis and hymenolepiasis.
Trematodes, liver-dwelling cause fascioliasis (Worldwide where sheep and cattle are raised): Infection occurs after ingestion of contaminated water or water-dwelling vegetation, e.g., watercress. Acute fascioliasis is characterized by fever, abdominal pain (especially hepatic), nausea, diarrhea, and hepatomegaly. Cough may also occur. Liver enzymes and erythrocyte sedimentation rates are usually elevated, and anemia is common. Chronic disease results in a variety liver and gallbladder abnormalities. Bithionol 30-50 mg/kg orally qod for 10-15 doses is the treatment of choice as this is written. Bithionol is available in the U.S. from CDC. Triclabendazole in a single dose of 10 mg/kg may become the drug of choice when available in the U.S. (Rosenblatt, 1999).
Liver/Spleen Disorders/Organomegaly/Jaundice
Amebiasis: See full discussion (Worldwide): Amebiasis is an amebic gastrointestinal infection (sometimes affecting other systems) that may be asymptomatic, chronic, or acute. Symptoms may include abdominal pain, diarrhea (with blood), weight loss, dehydration. Systemic dissemination is usually to the liver, but may also involve the brain, heart (pericarditis), lungs, and genitalia. Invasive amebiasis is treated with metronidazole and colonization without symptoms is treated with paromomycin or iodoquinol.
Ascariasis: See full discussion (Worldwide): Ascariasis is a nematode or roundworm infection with Ascaris lumbricoides causing transient respiratory symptoms initially and chronic gastrointestinal symptoms. The adult worms are more than 20 cm. in length, hence are easily seen in stool and may also emerge from the nose or mouth as a result of coughing or vomiting. Treatment is with albendazole single dose of 400 mg po (not FDA approved) or mebendazole or pyrantel pamoate.
Babesiosis (Europe, U.S., Mexico): Babesiosis is a rare tick-borne protozoal infection (Babesia sp.) of red blood cells. Babesiosis is self-limited with a duration of weeks to months and is characterized by irregular fever, chills, diaphoresis, headache, myalgia, and fatigue. Moderate hemolytic anemia, jaundice, hemoglobinuria, and hepatosplenomegaly are common. Treatment is focused on symptoms.
Brucellosis or undulant fever: See full discussion (Worldwide, especially Africa, Asia, and the Middle East). Brucellosis is caused by gram negative coccobacilli (Brucella abortus and other B. biovars) transmitted through contaminated milk, animal products, and related. Fever, chills, sweats, aches, fatigue, and joint pain are the most common manifestations. The most commonly affected systems (with a variety of manifestations) are cardiac, respiratory, gastrointestinal, genitourinary, and central nervous system. Long-term treatment 3-8 or more weeks) with medication combination is necessary. Doxycycline + rifampin or TMP/SMX DS tablets + rifampin are commonly used.
Chagas' Disease or American trypanosomiais: See full discussion (Most of Latin America): Chagas' disease is a protozoan infection with Trypanosoma cruzi transmitted by insect bite. Patients may be asymptomatic or have a lesion at the site of the bite; and symptoms of prolonged fever, tachycardia, fatigue, weakness, splenomegaly, and lymphadenopathy. Myocarditis or meningoencephalitis may also occur. Most patients experience spontaneous remission of symptoms, followed by a lifelong low-grade parasitemia. There is not currently a satisfactory treatment for any stage of Chagas' disease. Current treatment includes nifurtimox 8-10 mg/kg/day po qid for 90-120 days or benznidazole 5 mg/kg/day po for 60 days. These long-term therapies are toxic to some patients. In the United States, nifurtimox is available only from the Centers for Disease Control and benznidazole is not available in the U.S.
Clonorchiasis (China, Taiwan, Korea, Japan, Vietnam, and other areas of Asia) is a liver fluke (Clonorchis sinensis) infection of the biliary tract following ingestion of raw or pickled fish. Symptoms include upper abdominal pain, irregular high fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day. See trematodes below.
Echinococcosis (Hydatid disease): See full discussion (Most of the world; endemic in South America, North Africa, Middle East, Southern Europe - especially in areas where sheep are raised). Echinococcosis or hydatid disease is a tapeworm infection that often is asymptomatic, especially in the lengthy early stages. Echinococcus embryos trapped in various organs (especially the liver or lung) develop into hydatid cyst(s), which grow and eventually cause dysfunction according to the function or area of the organ(s). Surgical excision of the cyst remains the treatment of choice. Albendazole is given pre and post-operatively. Drug treatment includes albendazole or mebendazole or praziquantel - all with poor cure rates.
Helminthiasis: See ascariasis (summary or full discussion), echinococcosis/hydatid disease (summary or full discussion), schistosomiasis (summary or full discussion).
Hemorrhagic fevers (HFs): See full discussion of HFs. The major HFs include hemorrhagic fever with renal syndrome, hantavirus pulmonary syndrome, South American HFs, Lassa HF, Marburg and Ebola HFs, Kyasanur Forest HF, Omsk HF, Crimean-Congo HF, Chikungunya fever, dengue fever and HF, and Rift Valley fever (distribution is noted in the full discussion). The viral hemorrhagic syndrome (VHS) results from widespread increased permeability of microvasculature. Depending on the severity of vascular instability and decrease in platelet function, presentation may range from mild to severe illness; and hemorrhagic manifestations are not always apparent. A common course of illness begins with an abrupt onset of fever, myalgia, cutaneous flushing, and conjunctival suffusion. Within several days, the patient's condition worsens to include syncope, photophobia, headache, hyperesthesia, abdominal pain, nausea/vomiting, anorexia, and prostration. Treatment is primarily supportive, except that Lassa fever, South American HFs, and possibly Crimean-Congo HF and Rift Valley HF may be treated with a slow infusion of IV ribavirin.
Hepatitis (any): Hepatitis B surface antigen carrier rates in the tropics are > 40 times greater than in the West. Persons from China and Southeast Asia are at highest risk and perinatal transmission is common.
Histoplasmosis (Africa, Americas, East Asia, Australia): Best known in the West as an opportunistic infection of HIV, histoplasmosis is found among immigrants as the classic small-form histoplasmosis (primarily pulmonary) and as African histoplasmosis (primarily bone and cutaneous). Treatment is with amphotericin B initially, and itraconazole or fluconazole are used for maintenance therapy.
Leptospirosis: See full discussion (Worldwide, especially tropical areas of Latin America and Southeast Asia): Leptospirosis is a spirochette (Leptospira interrogans) infection transmitted primarily through exposure to water contaminated with urine from infected animals. Leptospirosis varies from asymptomatic to a severe or fatal illness. There are two common forms (anicteric and icteric or Weil's syndrome). Anicteric leptospirosis is the more common and milder form, and often is biphasic, with the first phase characterized by sudden onset high fever with chills, headache, conjunctival suffusion, cough and pulmonary chest pain, abdominal pain, nausea and vomiting, and myalgia. The illness may resolve after about one week with no further manifestations; or, after one to three days, recur with milder and more varied symptoms than in the first phase - except that aseptic meningitis may occur. Icteric leptospirosis or Weil's syndrome is the more severe form and is characterized by symptoms as described above (except not usually biphasic); and after about one week, the development of decreased renal function, pulmonary complications, jaundice, and/or hemorrhagic manifestations. Treatment includes antibiotics (doxycycline, penicillin, or others) and support.
Malaria: See full discussion (Tropical Africa, Asia, South and Central Americas; East China, Middle East): Malaria is caused by the protozoas Plasmodium falciporum, P. vivax, P. ovale, and P. malariae and is transmitted by mosquito bite, parenteral injection, or congenitally. Malaria is usually characterized by sudden onset of high fever, sweating, chills, uncontrollable shaking, headache, and splenomegaly. Fever tends to wax and wane in 48-72 hour cycles, though cycles may be irregular, especially with infection by P. falciporum. Onset may also be insidious, with less dramatic symptoms such as fever, headache, dyspnea, abdominal pain, nausea, diarrhea, myalgias, and splenomegaly. P. falciporum may cause parasitemia resulting in a life-threatening condition characterized by hemolysis, jaundice, anemia, acute renal failure, and hemoglobinuria. Cerebral malaria, also life-threatening, is characterized by gradual onset of severe headache, drowsiness, delerium, and coma. Seizures may also occur and are most common in children. P. faciporum causes death in as many as 25% of untreated cases. Treatment depends on the organism, immune status of the patient, and severity of the attack. Oral chloroquine is a mainstay of treatment except for infection with chloroquine-resistant P. falciporum. P. falciporum presents the greatest challenge because of severity of attacks as well as the existence of multidrug (especially chloroquine)-resistant strains. Combination drug treatment is common, e.g., mefloquine combined with artesunate for multidrug-resistant strains as described in the full discussion.
Opisthorchiasis (Eastern Europe and Russia; Thailand) is a liver fluke infection of the biliary tract following ingestion of raw or pickled fish. Most infected persons have no significant symptoms. If the parasite load is high, symptoms may include upper abdominal pain, feeling that something is moving in the liver, hepatomegaly with tenderness, jaundice, intermittent fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day. See trematodes below.
Q fever (Worldwide): Q fever is a rickettsial zoonosis (infection with gram negative Coxiella burnetii) contracted primarily from inhalation of dust contaminated by infected animals, especially sheep, cattle, and goats; and also other mammals. Other routes of infection include contact with milk and tissue from infected animals. Manifestations of acute Q fever include fever, fatigue, headache, cough, abdominal pain, nausea, diarrhea, and myalgia. Pneumonia develops in a small number of patients. Other complications are hepatitis, pericarditis, myocarditis, and meningoencephalitis. Hepato/splenomegaly and endocarditis are common in chronic Q fever. Endocarditis is frequently associated with purpuric rash, renal insufficiency, stroke, and heart failure. Treatment of acute Q fever is with doxycycline or a quinolone. Chronic Q fever requires combination therapy such as rifampin and doxycycline.
Schistosomiasis or Bilharzia: See full discussion (Numerous areas of the world, especially Africa and Asia with variants and locations noted in the full discussion). Schistosomiasis is caused by Schistosoma sp. and encompasses several syndromes, not all of which are evident in all infected persons. Initial symptoms may include a pruritic, papular rash - most commonly in persons who do not live in endemic areas. Acute schistosomiasis (Katayama fever) occurs in primary infection 1-2 months after exposure to heavy parasite loads. Symptoms may include fever of several weeks duration, headache, urticaria, cough, hepatosplenomegaly, lymphadenopathy, diarrhea, and eosinophilia. Hematuria and dysuria occur in some infections. Symptoms tend to gradually diminish over several months, but may intensify as more eggs are deposited. Chronic hepatosplenic schistosomiasis is a consequence of eggs retained in tissue and prolonged infection - usually > 10 years duration. The liver may be large or small and firm with nodularity. Portal hypertension, splenomegaly, or esophageal or gastric varices may occur. Hematemesis and splenomegaly are common presenting symptoms, with normal liver function. Periportal fibrosis and portal hypertension is associated with glomerulonephritis (proteinuria, renal failure) and pulmonary hypertension (cor pulmonale). Granulomatous tissue in the bowel results in bloody diarrhea. The last (chronic) stage varies according to species, with some species primarily affecting the liver and intestines, and one species affecting primarily the urinary tract. In general, patients with chronic schistosomiasis tend to present in developed countries with lethargy, colicky abdominal pain, mucoid/bloody diarrhea, or dysuria and hematuria. Salmonella infection concurrent with schistosomiasis is common and is resistant to treatment unless the schistosomiasis is also treated. Complications include progression of liver, kidney, or other organ dysfunction for many years after transmission has been interrupted - especially with heavy infection and re-exposure. Central nervous system lesions occur, but rarely. Treatment is according to species: For S. haematobium and S. mansoni, praziquantel 20/kg po bid for one day; for S. japonica and S. mekongi, praziquantel 20/kg po tid for one day are the treatments of choice. S. mansoni may also be treated with oxamniquine in a single po dose (with food) of 15 mg/kg. S. haematobium in North and East Africa may be treated with metrifonate 7.5-10 mg/kg every other week for a total of 3 doses.
Toxocariasis (Worldwide): Toxocariasis is the most common visceral larva migrans and is due to infection with the tissue nematode (roundworm) toxocara canis or T. cati. Toxocariasis is most common among children who eat feces-contaminated dirt. Most infections are small load and asymptomatic except for mild eosinophilia. Heavy worm loads, decreased immune competence, and other factors may lead to malaise, fever, cough and wheezing, hepatomegaly, anorexia, and weight loss. Ocular toxocariasis also occurs and usually leads to decreased vision. For symptomatic infections, the treatment of choice is diethylcarbamazine 6 mg/kg/day po tid for 10 days. Asymptomatic infections are not necessary to treat.
Toxoplasmosis (Worldwide): Toxoplasmosis is infection with Toxoplasma gondii, an obligate intracellular parasite (protozoan) usually transmitted by ingestion of undercooked meat or contaminated soil. There are two forms of toxoplasmosis, congenital and acquired. Congenital toxoplasmosis is associated with maternal infection shortly before conception, and is characterized by CNS involvement (convulsions, microcephaly or hydrocephaly, mental retardation and blindness) and liver involvement. Choreoretinitis is also common. Acquired toxoplasmosis is a well-known problem among immunocompromised persons, leading commonly to encephalitis, multiple organ infection, and death if not quickly treated. Among immunocompetent persons, toxoplasmosis is most commonly manifested by cervical lymphadenopathy, and less frequently by malaise, fatigue, fever, and headache. Choreoretinitis is common among both immunocompromised and immunocompetent persons. Treatment depends on immunocompetence and degree of symptomatology, and includes multi-drug regimes (commonly pyrimethamine + sulfadiazine or clindamycin) for 4-52 weeks; and in immunocompromised patients, lifelong maintenance therapy.
Trematodes (flukes): See schistosomiasis above or full discussion and see trematode infection by affected system below. Trematodes, biliary duct-dwelling cause diseases including clonorchiasis and opisthorchiasis. (1) Clonorchiasis (China, Taiwan, Korea, Japan, Vietnam, and other areas of Asia) is a liver fluke (Clonorchis sinensis) infection of the biliary tract following ingestion of raw or pickled fish. Symptoms include upper abdominal pain, irregular high fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day. (2) Opisthorchiasis (Eastern Europe and Russia; Thailand) is a liver fluke infection of the biliary tract following ingestion of raw or pickled fish. Most infected persons have no significant symptoms. If the parasite load is high, symptoms may include upper abdominal pain, feeling that something is moving in the liver, hepatomegaly with tenderness, jaundice, intermittent fever, lymphadenopathy, myalgia, and arthralgia. The condition may be chronic and include intermittent fever, vague abdominal symptoms, anorexia, and fatigue. Eosinophilia is pronounced. Treatment is with praziquantel 25 mg/kg po tid for one day.
Trypanosomiasis (African) or African sleeping sickness (Tropical Africa): Trypanosomiasis is caused by protozoal parasites, Trypanosoma brucei rhodesiene or T b gambiense, transmitted by bite of the tsetse fly. T b rhodesiene infections are more virulent than T b gambiense; and in the former, patients experience three stages of illness (trypanosomal chancre, hemolymphatic, and meningoencephalitic) as opposed to two stages in the latter (trypanosomal chancre and meningoencephalitic) with significantly milder symptoms. The painful trypanosomal chancre (3-10 cm) appears about two days after the bite and lasts 2-4 weeks. The hemolymphatic stage is characterized by high fevers lasting several days, with symptom-free periods of days to weeks. Less common manifestations of this stage are severe headache, malaise, arthralgia, lymphadenopathy, circinate rash, pruritis, and hepatosplenomegaly. Weight loss and debilitation also occur, and myocarditis may develop. The meningoencephalitic stage is characterized by progressive apathy, nighttime insomnia and daytime somnolence, anorexia, retarded speech, extrapyramidal signs (tremors, fasciculations, choreiform movements, and Parkinsonian-like appearance), and finally, coma and death. Treatment is complex and toxic, and depends on the infecting organism and stage of illness. Among the medications currently in use are suramin, melarsoprol, pentamidine, eflornithine, and corticosteroids.
Visceral leishmaniasis (kala-azar): See full discussion (East and North Africa, Middle East, Southern Europe, Central, South, and East Asia, South America, West Mexico): Cardinal signs of visceral leishmaniasis are prolonged fever, splenomegaly, anemia, leukopenia, or hypergammaglobulinemia. A cutaneous nodule may or may not appear at the site of the bite. Systemic symptoms include gradual onset fever that often rises and falls twice/day, fatigue, weight loss, dizziness, cough, and diarrhea. Visceral manifestations include pronounced splenomegaly (hard, non-tender) and to a lesser extent hepatomegaly. Other manifestations may include generalized lymphadenopathy; hyperpigmented skin of the forehead, abdomen, hands, and feet in light-skinned persons; skin lesions in dark-skinned persons; signs of bleeding (petechiae, epistaxis, bleeding gums); jaundice and ascites; and progressive wasting. Onset may also be acute, with the above manifestations appearing a few weeks after infection. Treatment has traditionally been unsatisfactory because of drug toxicities, poor responses, multiple disease syndromes, and other factors - including recently, the emergence of antimony-resistant strains. Orally administered miltefosine has recently shown great promise. Other treatments include intravenous sodium stibogluconate (a pentavalent antimony compound) for 10-60 days depending on where the disease was contracted and whether illness is first or second episode.
Yellow fever (most of tropical and subtropical South America and Africa): Yellow fever (YF) is caused by an arbovirus transmitted by the Aedes aegypti mosquito from one human to another (the urban form of YF) or from monkeys to humans (the jungle or sylvan form of YF). YF is characterized by sudden onset flu-like (non-specific) symptoms occurring in two stages with a short intervening remission. The first stage of severe YF has a sudden onset of fever, chills, intense headache, lumbosacral back pain, myalgia, nausea and vomiting, conjunctival injection, dark urine, and bradycardia in relation to fever. After a 12-24 hour remission, there is an "intoxication" or hepatorenal stage that features reemergence of generalized symptoms including increased temperature, increased nausea and vomiting, abdominal pain, jaundice, and prostration. Complications of severe YF include jaundice, dehydration, decreased renal function, delirium, and hemorrhagic symptoms. Terminal signs include progressive tachycardia, intractable hiccups, and shock. Lab findings include albuminuria, leukopenia, abnormal liver function, increased prothrombin times. Treatment is supportive, i.e, control of fever, vomiting, dehydration, and pain.