Table 1.

Parasites to which laboratory workers could be exposeda

ParasiteRoutes of exposureaInfectious stage(s)Protective measuresDiagnostic testingbCommon clinical manifestations of infectionc
Blood and tissue protozoa
Acanthamoeba spp.Wound, eye (aerosol?) (needle?)Trophozoite, cystGloves, mask, gown, class 2 BSCa, wound and needle precautionsBrain biopsy, culture, corneal scraping (serology?)Headache, neurologic impairment, skin abscess, pneumonitis, keratitis, conjunctivitis
Babesia spp.Needle, wound, vectorIntraerythrocytic stages, sporozoiteGloves, wound and needle precautionsBlood smear, serology, animal inoculationFever, chills, fatigue, anemia
Balamuthia mandrillaris Wound (aerosol?) (needle?)Trophozoite, cystGloves, mask, gown, class 2 BSC, wound and needle precautionsBrain biopsy, culture (serology?)Headache, neurologic impairment, skin abscess (pneumonitis?)
Leishmania spp.Needle, wound, transmucosal, vectorAmastigote, promastigoteGloves; wound, mucous membrane,d and needle precautionsCutaneous: lesion scraping, biopsy and impression smear, culture, animal inoculation Visceral: serology, biopsy, culture, animal inoculation Mucosal: serology, biopsy, culture, animal inoculationCutaneous: nodules/ulcers Visceral: fever (early), hepatosplenomegaly and pancytopenia (late) Mucosal: naso-oropharyngeal mucosal lesions
Naegleria fowleri Transmucosal (nasopharynx), aerosol (needle?)Trophozoite (flagellate?) (cyst?)Gloves, mask, gown, class 2 BSC, wound and needle precautionsCSF exam and cultureHeadache, stiff neck, coma, neurologic impairment (including sense of smell)
Plasmodium spp.Needle, wound, vectorIntraerythrocytic stages, sporozoiteGloves, wound and needle precautionsBlood smear, serology, culture, animal inoculationFever, chills, fatigue, anemia
Sarcocystis spp.OralSarcocyst; oocyst or sporocystGloves, hand washingStool exam, muscle or cardiac biopsyGastrointestinal symptoms, eosinophilic myositis
Toxoplasma gondii Oral, needle, wound, transmucosal (aerosol?)Oocyst, tachyzoite, bradyzoiteGloves, hand washing; wound, mucous membrane, and needle precautionsSerology, animal inoculation, tissue cell cultureAdenopathy, fever, malaise, rash
Trypanosoma cruzi (American trypanosomiasis)Needle, wound, transmucosal, vector (aerosol?)TrypomastigoteGloves; wound, mucous membrane, and needle precautionsBlood smear, culture, biopsy, animal inoculation, xenodiagnosis, serologySwelling and/or redness at inoculation site, fever, rash, adenopathy, electrocardiographic changes
Trypanosoma brucei rhodesiense andgambiense (African trypanosomiasis)Needle, wound, transmucosal, vector (aerosol?)TrypomastigoteGloves; wound, mucous membrane, and needle precautionsBlood smear, CSF exam, culture, biopsy, animal inoculation, serologySwelling and/or redness at inoculation site, fever, rash, adenopathy, headache, fatigue, neurologic signs
Intestinal protozoae
Cryptosporidium parvum Oral, transmucosal (aerosol?e)Oocyst (sporozoite)Gloves, hand washing, mucous membrane precautionsStool exams with concentration and special stains, immunodiagnostic test for antigen in stoolSymptoms of gastroenteritis
Cyclospora cayetanensis Orale Oocyst (sporozoite)Gloves, mask, hand washingUV fluorescence microscopy, stool exams with concentration and special stainsSymptoms of gastroenteritis
Entamoeba histolytica Orale CystGloves, mask, hand washingStool exams with concentration, immunodiagnostic test for antigen in stool, serology (for invasive disease)Symptoms of gastroenteritis (stools may be bloody)
Giardia lamblia Oral (aerosol?e)CystGloves, mask, hand washingStool exams with concentration, immunodiagnostic test for antigen in stoolSymptoms of gastroenteritis
Isospora belli Orale Oocyst (sporozoite)Gloves, mask, hand washingUV fluorescence microscopy, stool exams with concentration and special stainsSymptoms of gastroenteritis
Other protozoa
 Microsporidian spp.f Eye (aerosol?), transmucosal, oral (wound?) (needle?)SporeGloves, mask, gown, hand washing, class 2 BSC, wound and needle precautionsMicroscopic exam and culture of corneal scraping, skin biopsy specimen, feces, urine, sputum, bronchoalveolar lavage, muscle biopsy specimen, CSFKeratoconjunctivitis, skin ulceration, diarrhea, cystitis, pneumonitis
Helminthsg
Ascaris lumbricoides OralEggGloves, mask, hand washingStool examCough, fever, pneumonitis; abdominal cramps, diarrhea or constipationh
Enterobius vermicularis OralEggGloves, mask, hand washing, nail cleaningScotch tape testPerianal pruritus
Fasciola hepatica OralMetacercariaGloves, mask, hand washingExam of stool or bile for eggs, serologyRight upper quadrant pain, biliary colic, obstructive jaundice, elevated transaminase levels
 HookwormPercutaneousi LarvaGloves, gown, hand washingStool examAnimal speciesj: cutaneous larva migrans or creeping eruption (skin) Human species: diarrhea, abdominal pain, anemiah
Hymenolepis nana OralEggGloves, mask, hand washingStool examAbdominal pain, diarrhea
Schistosomaspp.Percutaneousi CercariaGloves, gown, hand washingStool exam, serologyAcute schistosomiasis: dermatitis, fever, cough, hepatosplenomegaly, adenopathy
Strongyloides stercoralis Percutaneousi LarvaGloves, gown, hand washingStool exam (motile larvae may be seen in wet preparations), serologyCough and chest pain followed by abdominal pain and crampingh
Taenia solium OralEgg, cysticercusGloves, hand washingCysticercosis: serology, brain scan, soft tissue X ray Worm: stool examCysticercosis: neurologic symptoms Worm: usually asymptomatic but may cause vague abdominal symptoms
Trichinella spiralis OralLarvaGloves, mask, hand washingSerology, muscle biopsyAbdominal and muscle painh
Trichuris trichiura OralEggGloves, mask, hand washingStool examAbdominal pain, tenesmush
  • a The parasites listed here should be handled in accordance with BSL-2 standards. Laminar-flow biological safety cabinets (class 2 BSCs), other physical containment devices, and/or personal protective equipment (e.g., face shield) should be used whenever procedures with a high potential for creating aerosols or droplets are conducted. See the text for discussion of additional parasites. See the text and other tables for more details about routes of exposure. In this table, the “needle” route signifies parenteral transmission (i.e., percutaneous transmission, via a contaminated sharp such as a needle) and the “wound” route signifies contamination (e.g., via a spill or splash) of a preexisting abrasion, cut, or break in the skin.

  • b PCR and other molecular techniques could also be useful for detecting infection with some of the listed parasites.

  • c The clinical manifestations can be highly variable, depending in part on such factors as the species of the parasite, the size of the inoculum, and the stage of the infection. The listed manifestations are by no means all-inclusive and do not necessarily include some of the more serious manifestations of illness (e.g., cerebral malaria and myocarditis and encephalitis from toxoplasmosis).

  • d Use of a class 2 BSC provides optimal protection against exposure of the mucous membranes of the eyes, nose, and mouth.

  • e The possibility of becoming infected from swallowing inhaled infectious aerosols or droplets has been raised forC. parvum (N. Hojlyng, W. Holten-Andersen, and S. Jepsen, Letter, Lancet ii:271–272, 1987) and G. lamblia(154). The same principle could apply to the other intestinal protozoa. C. parvum oocysts can bypass the gastrointestinal tract and establish a pulmonary infection directly.

  • f Some species of microsporidia have been recognized to be pathogens in immunocompromised persons, especially patients with AIDS, and occasionally have been found to cause disease in persons with normal immune systems (27). Laboratorians could be exposed to microsporidian spores from clinical specimens or cultures; several species belonging to four genera are now culturable. Although no laboratory-acquired infections with microsporidia have been reported to date, the risk for such infections could increase as research on microsporidia increases.

  • g Eosinophilia is common for those helminthic infections with an invasive tissue stage.

  • h Symptoms are unusual unless the infecting inoculum is heavy, which would be unlikely in most laboratory-acquired infections.

  • i Parasite can penetrate intact skin.

  • j Cutaneous larva migrans usually is caused by animal hookworms, typically Ancylostoma spp., and sometimes by animal and human Strongyloides spp. and other species.