Biosafety
Helminths (Nematodes) are regarded by the United States Center for Disease Control as Biosafety level 2 (BSL-2) organisms. Guidelines for classification of organisms, laboratory practice and shipping requirements are contained in a US government document Biosafety in Microbiological and Biomedical Laboratories* by the U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention and National Institutes of Health. Fifth Edition, 2007.
It is worth noting that neither of the human hookworm species (Necator americanus and Ancylostoma duodenale) are mentioned, presumably because they cause less serious disease or problems in the laboratory, than other listed species.
Relevant sections of the document are excerpted below.
Section VIII-C: Parasitic Agents
General Issues
Additional details about occupationally-acquired cases of parasitic infections, as well as recommendations for post exposure management, are provided elsewhere.1-3 Effective antimicrobial treatment is available for most parasitic infections.4 Immunocompromised persons should receive individualized counseling (specific to host and parasite factors) from their personal healthcare provider and their employer about the potential risks associated with working with live organisms.
BSL-2 and ABSL-2 practices,5 containment equipment, and facilities are recommended for activities with infective stages of the parasites discussed in this chapter. Microsporidia, historically considered parasites, are now recognized by most experts to be fungi; however, microsporidia are maintained in the parasitic agent section is this edition. These organisms are discussed here because a laboratory-acquired case of infection has been reported,6 and most persons currently still look for microsporidia associated with discussion of parasitic agents.
Importation of parasitic agents may require CDC and/or USDA importation permits. Domestic transport of this agent may require a permit from USDA/APHIS/VS.
Agent: Nematode Parasites
Nematode parasites that pose greatest occupational risk include the ascarids, especially Ascaris and Baylisascaris; hookworms, both human and animal; Strongyloides, both human and animal; Enterobius; and the human filariae, primarily Wuchereria and Brugia. Ancylostoma braziliense and A. caninum cause hookworm infection in cats and dogs, respectively. Ascaris lumbricoides causes ascariasis and is known as the large intestinal Agent Summary Statements- Parasitic Agents
roundworm of humans. Enterobius vermicularis, known as the human pinworm or seatworm, causes enterobiasis or oxyuriasis. Strongyloides, the threadworm, causes strongyloidiasis. Ancylostoma, Ascaris, and Strongyloides reside as adults in the small intestine of their natural hosts, whereas E. vermicularis colonizes the cecum and appendix.
Occupational Infections
Laboratory associated infections with Ancylostoma spp., A. lumbricoides, E. vermicularis, and Strongyloides spp. have been reported.1-3 Laboratory infections with hookworms and Strongyloides presumptively acquired from infected animals have been reported. Allergic reactions to various antigenic components of human and animal ascarids (e.g., aerosolized antigens) may pose risk to sensitized persons. Laboratory-acquired infections with these nematodes can be asymptomatic, or can present with a range of clinical manifestations dependent upon the species and their location in host. Infection with hookworm of animal origin can result in cutaneous larva migrans or creeping eruption of the skin. Infection with A. lumbricoides may produce cough, fever, and pneumonitis as larvae migrate through the lung, followed by abdominal cramps and diarrhea or constipation from adult worms in the intestine. Infection with E. vermicularis usually causes perianal pruritis, with intense itching. Infection with animal Strongyloides spp. may induce cutaneous larva migrans.
Natural Modes of Infection
Ancylostoma infection in dogs and cats is endemic worldwide. Human infection occurs through penetration of the skin. Cutaneous larva migrans or creeping eruption occurs when infective larvae of animal hookworms, typically dog and cat hookworms, penetrate the skin and begin wandering. Ancylostoma larvae can also cause infection if ingested. These larvae do not typically reach the intestinal tract, although A. caninum has on rare occasions developed into non-gravid adult worms in the human gut.
Ascaris lumbricoides infection is endemic in tropical and subtropical regions of the world. Infection occurs following accidental ingestion of infective eggs. Unembryonated eggs passed in the stool require two to three weeks to become infectious, and Ascaris eggs are very hardy in the environment.
Enterobius vermicularis occurs worldwide, although infection tends to be more common in school-age children than adults, and in temperate than in tropical regions. Pinworm infection is acquired by ingestion of infective eggs, most often on contaminated fingers following scratching of the perianal skin. Eggs passed by female worms are not immediately infective, but only require several hours’ incubation to become fully infectious. Infection with this worm is relatively short (60 days on average), and reinfection is required to maintain an infection.
Agent Summary Statements- Parasitic Agents
Strongyloides infection in animals is endemic worldwide. People become infected with animal Strongyloides when infective, filariform larvae penetrate the skin, and can develop cutaneous creeping eruption (larva currens).
LABORATORY SAFETY
Eggs and larvae of most nematodes are not infective in freshly passed feces; development to the infective stages may require from one day to several weeks. Ingestion of the infective eggs or skin penetration by infective larvae are the primary hazards to laboratory staff and animal care personnel. Development of hypersensitivity is common in laboratory personnel with frequent exposure to aerosolized antigens of ascarids. Ascarid eggs are sticky, and special care should be taken to ensure thorough cleaning of contaminated surfaces and equipment. Caution should be used even when working with formalin-fixed stool samples because ascarid eggs can remain viable and continue to develop to the infective stage in formalin.8
Working with infective eggs of other ascarids, such as Toxocara and Baylisascaris, poses significant risk because of the potential for visceral migration of larvae, including invasion of the eyes and central nervous system. Strongyloides stercoralis is of particular concern to immunosuppressed persons because potentially life-threatening systemic hyperinfection can occur. [1] [2] Lugol’s iodine kills infective larvae and should be sprayed onto skin or laboratory surfaces that were contaminated accidentally. The larvae of Trichinella in fresh or digested tissue could cause infection if accidentally ingested. Arthropods infected with filarial parasites pose a potential hazard to laboratory personnel.
Containment Recommendations
BSL-2 and ABSL-2 practices, containment equipment, and facilities are recommended for activities with infective stages of the nematodes listed here.5 Exposure to aerosolized sensitizing antigens of ascarids should be avoided. Primary containment (e.g., BSC) is recommended for work that may result in aerosolization of sensitization from occurring.
SPECIAL ISSUES
Treatment Highly effective medical treatment for most nematode infections exists.4 Transfer of Agent Importation of these agents may require CDC and/or USDA importation permits. Domestic transport of these agents may require a permit from USDA/APHIS/VS. A DoC permit may be required for the export of this agent to another country.
See Appendix C for additional information.
REFERENCES
1. Herwaldt BL. Laboratory-acquired parasitic infections from accidental exposures.
Clin Microbiol Rev. 2001:14:659-88.
Appendix C: Transportation of Infectious Substances
An infectious substance is a material known to contain or reasonably expected to contain a pathogen. A pathogen is a microorganism (including bacteria, viruses, rickettsiae, parasites, fungi) or other agent, such as a proteinaceous infectious particle (prion), that can cause disease in humans or animals. Infectious substances may exist as purified and concentrated cultures, but may also be present in a variety of materials, such as body fluids or tissues. Transportation of infectious substances and materials that are known or suspected to contain them are regulated as hazardous materials by the United State Department of Transportation (DOT), foreign governments, and the International Civil Aviation Organization, and their transportation is subject to regulatory controls. For transport purposes, the term “infectious substance” is understood to include the term “etiologic agent.”
TRANSPORTATION REGULATIONS
International and domestic transport regulations for infectious substances are designed to prevent the release of these materials in transit to protect the public, workers, property, and the environment from the harmful effects that may occur from exposure to these materials. Protection is achieved through rigorous packaging requirements and hazard communication. Packages must be designed to withstand rough handling and other forces experienced in transportation, such as changes in air pressure and temperature, vibration, stacking, and moisture. Hazard communication includes shipping papers, labels, markings on the outside of packagings, and other information necessary to enable transport workers and emergency response personnel to correctly identify the material and respond efficiently in an emergency situation. In addition, shippers and carriers must be trained on these regulations so they can properly prepare shipments and recognize and respond to the risks posed by these materials. Select agents include infectious substances that have been identified by the CDC and the USDA as having the potential to pose a severe threat to public health and safety. Persons who offer for transportation or transport select agents in commerce in the United States must develop and implement security plans for such transportation. A security plan must include an assessment of the possible transportation security risks for materials covered by the security plan and specific measures to reduce or eliminate the assessed risks. At a minimum, a security plan must include measures to address those risks associated with personnel security, en route security, and unauthorized access.
REGULATIONS
Department of Transportation. 49 CFR Part 171-180, Hazardous Materials Regulations. Applies to the shipment of infectious substances in commercial transportation within the United States. Information on these regulations may be obtained at the Internet website: http://hazmat.dot.gov. United States Postal Service (USPS). 39 CFR Part 20, International Postal Service (International Mail Manual), and Part 111, General Information on Postal Service (Domestic Mail Manual).
Appendix C
Regulations on transporting infectious substances through the USPS are codified in Section 601.10.17 of the Domestic Mail Manual and Section 135 of the International Mail Manual. A copy of the Domestic and International Mail Manuals may be obtained from the Government Printing Office by calling Monday through Friday, 7:30 a.m. - 9:00 p.m. EST: 202- 512-1800, 866-512-1800 (toll free). Occupational Health and Safety Administration (OSHA). 29 CFR Part 1910.1030, Occupational Exposure to Bloodborne Pathogens. These regulations provide minimal packaging and labeling for blood and body fluids when transported within a laboratory or outside of it. Information may be obtained from your local OSHA office or from the Internet website: http://www.osha.gov/. Technical Instructions for the Safe Transport of Dangerous Goods by Air (Technical Instructions). International Civil Aviation Organization (ICAO). Applies to the shipment of infectious substances by air and is recognized in the United States and by most countries worldwide. A copy of these regulations may be obtained from the ICAO Document Sales Unit at
(514) 954-8022, Fax: (514) 954-6769, E-Mail: sales_unit@icao.int, or from the Internet website: http://www.icao.org.
Dangerous Goods Regulations. International Air Transport Association (IATA).
These regulations are issued by an airline association, are based on the ICAO Technical Instructions, and are followed by most airline carriers. A copy of these regulations can be obtained from the Internet websites: http://www.iata.org/index.htm or http://www.who.int/en/, or by contacting the IATA Customer Care office at: Tel: +1 (514) 390 6726, Fax: +1 (514) 874 9659, for Canada and USA (800) 716-6326 (Toll free), Europe, Africa and Middle East +41 (22) 770 2751, Fax: +41 (22) 770 2674, TTY: YMQTPXB, or E-mail: “custserv@iata.org”.
TRANSFERS
Regulations governing the transfer of biological agents are designed to ensure that possession of these agents is in the best interest of the public and the nation. These regulations require documentation of personnel, facilities, justification of need and pre-approval of the transfer by a federal authority. The following regulations apply to this category: Importation of Etiologic Agents of Human Disease.42 CFR Part 71 Foreign Quarantine. Part 71.54 Etiological Agents, Hosts and Vectors. This regulation requires an import permit from the CDC for importation of etiologic agents, hosts or vectors of human disease. The regulation, application form, and additional guidance can be found at the CDC website: http://www.cdc.gov/od/eaipp/. Completed application forms may be submitted to the CDC Etiologic Agent Import Permit Program by Fax: (404) 718-2093 or by mail:
Centers for Disease Control and Prevention
Etiologic Agent Import Permit Program
1600 Clifton Road, N.E., Mailstop A-46
Atlanta, GA 30333.