Agent Summary
Statements
Laboratory-associated infections with Ascaris spp.; Strongyloides spp.; hookworms; and Enterobius spp. have been reported (91, 110, 151). Allergic reactions to various antigenic components of nematodes (e.g., aerosolized Ascaris antigens) may represent an individual risk to sensitized persons. Laboratory animal-associated infections (including arthropods) have not been reported, but infective larvae in the feces of nonhuman primates infected with Strongyloides spp. are a potential infection hazard for laboratory and animal care personnel.
LABORATORY HAZARDS: Eggs and larvae in freshly passed feces of infected hosts are usually not infective; development to the infective stages may take periods of one day to several weeks. Trichinella is of concern since fresh or digested tissue may contain larvae and would be infective if ingested. Ingestion of the infective eggs or skin penetration of infective larvae are the primary hazards to laboratory and animal care personnel. Arthropods infected with filarial parasites pose a potential hazard to laboratory personnel. In laboratory personnel with frequent exposure to aerosolized antigens of Ascaris spp. development of hypersensitivity is common.
RECOMMENDED PRECAUTIONS: Biosafety Level 2 practices and facilities are recommended for activities with infective stages listed. Exposure to aerosolized sensitizing antigens of Ascaris spp. should be avoided. Primary containment (e.g., biological safety cabinet) may be required for work with these materials by hypersensitive individuals. Appropriate treatment for most nematode infections exists, and information on dosage, source of drugs, etc. is available (5).
AGENT: Protozoal Parasites of Humans
Laboratory-associated infections with Toxoplasma spp.; Plasmodium spp. (including P. cynomologi); Trypanosoma spp.; Entamoeba spp.; Coccidia spp.; Giardia spp.; Leishmania spp.; Sarcocystis spp.; and Cryptosporidia spp. have been reported (29, 68, 91, 110, 151, 162). In addition, no laboratory infections with Babesia spp. or Microsporidia spp. have been reported but could result from accidental needlestick or ingestion of cysts, oocysts, or spores in feces.
Although laboratory animal-associated infections have not been reported, a direct source of infection for laboratory personnel may be contact with lesion material from rodents with cutaneous leishmaniasis and with feces or blood of experimentally or naturally infected animals.
Laboratory-related infections with Cryptosporidia have occurred with regularity in almost every laboratory working with this agent, especially those in which calves are utilized as the source of oocysts. Other experimentally-infected animals pose potential risks as well. There is circumstantial evidence that airborne transmission of oocysts of this small organism may occur. Rigid adherence to protocol should reduce the occurrence in laboratory and animal care personnel.
LABORATORY HAZARDS: Infective stages may be present in blood, feces, lesion exudates, and infected arthropods. Depending on the parasite, ingestion, skin penetration through wounds or microabrasions, accidental parenteral inoculation, and transmission by arthropod vectors are the primary laboratory hazards. Aerosol or droplet exposure of the mucous membranes of the eyes, nose, or mouth with trophozoites are potential hazards when working with cultures of Naegleria fowleri, Leishmania spp., T. cruzi, or with tissue homogenates or blood containing hemoflagellates. Immunocompromised individuals should avoid working with live organisms. Because of the grave consequences of toxoplasmosis in the developing fetus, serologically negative women of childbearing age who might become pregnant should not work with Toxoplasma in the same laboratory room where these materials are handled.
RECOMMENDED PRECAUTIONS: Biosafety Level 2 practices and facilities are recommended for activities with infective stages of the parasites listed. Infected arthropods should be maintained in facilities which reasonably preclude the exposure of personnel or their escape to the outside. Primary containment (e.g., biological safety cabinet) or personal protection (e.g., face shield) may be indicated when working with cultures of Naegleria fowleri, Leishmania spp., T. cruzi or with tissue homogenates or blood containing hemoflagellates (81). Gloves are recommended for activities where there is the likelihood of direct skin contact with infective stages of the parasites listed. Appropriate treatment for most protozoal infections exists, and information on dosage, source of drugs, etc., is available (5).
AGENT: Trematode Parasites of Humans (Schistosoma spp. and Fasciola spp.)
Laboratory-associated infections with Schistosoma spp. and Fasciola spp. have been reported, none associated directly with laboratory animals (91, 110, 151).
LABORATORY HAZARDS: Infective stages of Schistosoma spp. (cercariae) and Fasciola spp. (metacercaria) may be found, respectively, in the water or encysted on aquatic plants in laboratory aquaria used to maintain snail intermediate hosts. Skin penetration by schistosome cercariae and ingestion of fluke metacercaria are the primary laboratory hazards. Dissection or crushing of schistosome-infected snails may also result in exposure of skin or mucous membrane to cercariae-containing droplets. Additionally, metacercaria may be inadvertently transferred from hand to mouth by fingers or gloves following contact with contaminated aquatic vegetation or surfaces of aquaria. Most laboratory exposures to Schistosoma spp. would predictably result in low worm burdens with minimal disease potential. Safe and effective drugs are available for the treatment of schistosomiasis.
RECOMMENDED PRECAUTIONS: Biosafety Level 2 practices and facilities are recommended for activities with infective stages of the parasites listed. Gloves should be worn when there may be direct contact with a water containing cercariae, or vegetation containing metacercaria from naturally or experimentally infected snail intermediate hosts. Long-sleeved laboratory coats or other protective garb should be worn when working arouquaria or other water sources that may contain schistosome cercariae. Snails and cercariae in the water of laboratory aquaria should be killed by chemicals (e.g., hypochlorites, iodine) or heat before discharge to sewers. Appropriate treatment for most trematode infections exists, and information on source of drugs, dosage, etc. is available (5).
AGENT: Cestode Parasites of Humans - Echinococcus granulosus, Taenia solium (cysticercus cellulosae) and Hymenolepsis nana.
Although no laboratory-associated infections with either E. granulosus or T. solium have been reported, the consequences of such infections following the ingestion of infective eggs of E. granulosus or T. solium are potentially grave. H. nana is a very cosmopolitan parasite, does not require an intermediate host, and is directly transmissible by ingestion of feces of infected humans or rodents.
LABORATORY HAZARDS: Infective eggs may be present in the feces of dogs or other canids (the definitive hosts of E. granulosus), or in the feces of humans (the definitive host of T. solium). Ingestion of infective eggs from these sources are the primary laboratory hazard. Cysts and cyst fluids of E. granulosus are not infectious for humans. Ingestion of cysts containing the larval stage of T. solium (Cysticercus cellulosae) readily produces human infection with the adult tapeworm. With either parasite, the ingestion of a single infective egg from the feces of the definitive host could potentially result in serious disease. Ingestion of the eggs of H. nana in the feces of the definitive host could result in intestinal infection.
RECOMMENDED PRECAUTIONS: Biosafety Level 2 practices and facilities are recommended for work with infective stages of these parasites. Special attention should be given to personal hygiene practices (e.g., handwashing) and avoidance of ingestion of infective eggs. Gloves are recommended when there may be direct contact with feces or surfaces contaminated with fresh feces of dogs infected with E. granulosus, humans infected with T. solium adults, or humans or rodents infected with H. nana. Appropriate treatment for many cestode infections exists, and information concerning source of drugs, dosage, etc., is available (5).