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SECTION I - INFECTIOUS AGENT
NAME: Toxoplasma gondii
SYNONYM OR CROSS REFERENCE: Toxoplasmosis, congenital toxoplasmosis.
CHARACTERISTICS: Obligate intracellular sporozoan; both sexual and asexual reproductive cycles occur in
the gastrointestinal tract of felines; major morphologic forms of the parasite are oocyst, trophozoite, and tissue
cyst; oocyst is ovoid, measures 10-12 um in diameter; trophozoites are crescent shaped and measure 3 X 7 um; tissue
cysts measure 10-200 um in diameter.
SECTION II - HEALTH HAZARD
PATHOGENICITY: Most infections are asymptomatic with a localized lymphadenopathy accompanied with fever,
sore throat, rash mimicking infectious mononucleosis in some individuals; immunocompromised host suffers from widespread
dissemination of the infection with pneumonitis, myocarditis, and encephalitis; congenital cases can result in
abortion and stillbirth, live births result in severe central nervous system involvement along with chorioretinitis.
EPIDEMIOLOGY: Worldwide; 3-70% of healthy adults are seropositive; increased cases of cerebral toxoplasmosis
in AIDS patients; higher incidence in the tropics and lower in cold, and regions.
HOST RANGE: Cats and other felines; most warm blooded animals both domestic and wild; humans.
INFECTIOUS DOSE: Not known
MODE OF TRANSMISSION: Consuming undercooked infected meats (pork, mutton, beef); ingestion of infective
oocysts in milk, food or water; inhalation of oocysts; transplacental; contact with soil containing infected cat
feces; transmission through blood transfusions or organ transplantations is possible although rare.
INCUBATION PERIOD: 5-23 days
COMMUNICABILITY: Not directly transmitted from person to person except in utero; oocysts shed by cats become
infective 1-5 days later and remain infectious for up to 1 year in water or moist soil; cysts in meat are infectious
as long as meat is edible and uncooked.
SECTION III - DISSEMINATION
RESERVOIR: Definitive hosts are cats; intermediate hosts are sheep, goats, rodents, swine, cattle, chicken,
and birds.
ZOONOSIS: Yes, direct or indirect contact of mucous membrane with feces from infected animals.
VECTORS: None
SECTION IV - VIABILITY
DRUG SUSCEPTIBILITY: Sulfonamides and pyrimethamines are effective.
SUSCEPTIBILITY TO DISINFECTANTS: Oocysts are susceptible to iodine and formalin; trophozoites and tissue
cysts are susceptible to most disinfectants; 1% sodium hypochlorite (20% commercial bleach), 70% ethanol.
PHYSICAL INACTIVATION: Oocysts are inactivated by temperature >66o C; trophozoites are inactivated at
pH < 4.0, tissue cysts are inactivated by freezing and thawing
SURVIVAL OUTSIDE HOST: Oocysts are very stable and can survive up to I year in water or moist soil-, trophozoites
can survive in body fluids up to 1 day; tissue cysts can survive for weeks at room temperature in body fluids.
SECTION V - MEDICAL
SURVEILLANCE: Monitor patients for clinical signs and confirm by demonstration of agent in tissues or
fluids; serological tests.
FIRST AID/TREATMENT: Pyrimethamine combined with sulfadiazine is indicated for patients with organ involvement;
spiramycin (available via FDA) for pregnant women.
IMMUNIZATION: None
PROPHYLAXIS: Pyrimethamine-tine combined with sulfadiazine and folic acid in special cases.
SECTION VI - LABORATORY HAZARDS
LABORATORY-ACQUIRED INFECTIONS: Most common lab-acquired parasitic infection, twenty-eight cases with
one death reported up to 1976; cases were caused by accidental inoculation, performing autopsies, and splashing.
SOURCES/SPECIMENS: Blood and blood products; semen; feces.
PRIMARY HAZARDS: Accidental parenteral inoculation, ingestion, contamination of broken skin and mucous membranes.
SPECIAL HAZARDS: Feces from infected animals, ie. changing litter.
SECTION VII - RECOMMENDED PRECAUTIONS
CONTAINMENT REQUIREMENTS: Biosafety level 2 practices and containment facilities for activities involving
infectious stages of the parasite; work should be conducted in a biosafety cabinet.
PROTECTIVE CLOTHING: Laboratory coat; gloves when skin contact with infectious materials is unavoidable.
OTHER PRECAUTIONS: Pregnant women should be discouraged from working with Toxoplasma spp.
SECTION VIII - HANDLING INFORMATION
SPILLS: Allow aerosols to settle; wearing protective clothing, gently cover spill with absorbent paper
towel and apply 1% sodium hypochlorite (20% commercial bleach), starting at the perimeter and working towards the
center; allow sufficient contact time (30 mins.) before clean up.
DISPOSAL: Decontaminate all wastes before disposal; steam sterilization, chemical disinfection, incineration.
STORAGE: In sealed containers that are appropriately labeled.
Date prepared: October 11, 1997 Prepared by: Canadian Office of Biosafety Information edited by the Colorado State
University Office of Biosafety- June 16, 1998.
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