Isolation and molecular characterization of Toxoplasma gondii from chickens from Sri Lanka

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 100 free-range chickens (Gallus domesticus) from Sri Lanka was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). Antibodies were found in 39 chickens with titers of 1:5 in 8, 1:10 in 8, 1:20 in 4, 1:40 in 5, 1:80 in 5, 1:160 in 5, 1:320 in 2, 1:640 or more in 2. Hearts and brains of 36 chickens with MAT titers of 1:5 or more were bioassayed in mice. Tissues of 3 chickens with doubtful titers of 1:5 were pooled and fed to a cat; the cat shed T. gondii oocysts in its feces. Tissues from 61 chickens with titers of less than 1:5 were pooled and fed to 2 T. gondii-free cats; the cats did not shed oocysts. Toxoplasma gondii was isolated from 11 of 36 seropositive chickens by bioassay in mice. All 12 T. gondii isolates were avirulent for mice. Genotyping of 12 isolates using the SAG2 locus indicated that 6 were type III, and 6 were type II. This is the first report of genetic characterization of T. gondii from any host in Sri Lanka.     

High prevalence of viable Toxoplasma gondii infection in market weight pigs from a farm in Massachusetts

The ingestion of uncooked infected meat is considered important in the epidemiology of Toxoplasma gondii infection in humans and little is known of the prevalence of viable T. gondii in meat used for human consumption in the United States. In the present study, viable T. gondii was isolated from 51 out of 55 pigs destined for human consumption. Hearts and tongues (500 g) from fifty-five 6-mo-old pigs from a farm in Massachusetts were bioassayed for T. gondii by feeding them to T. gondii-free cats. Feces of these cats were examined for shedding of T. gondii oocysts. Fifty-one of 55 cats fed pig tissues each shed 25-810 million T. gondii oocysts in their feces. Two of these cats consumed tissues of pigs that were shown to be seronegative with the Sabin-Feldman dye test, the modified agglutination test, and the Western blot. Results indicate that until examination of meat for T. gondii infection is implemented in slaughterhouses, all meat should be cooked according to industry guidelines before human consumption.     

Tachyzoite-induced life cycle of Toxoplasma gondii in cats

The tachyzoite-induced cycle of Toxoplasma gondii was studied in 46 cats. Tachyzoites of the M-7741 or Me-49 strain of T. gondii were administered orally to cats by pouring into the mouth or by stomach tube, or by intraintestinal inoculation. Ten weaned cats that had been inoculated with tachyzoites directly in the intestine were killed 1, 3, 6, 9, 12, 15, 18, or 25 days later, and their tissues were studied histologically and bioassayed in mice. Toxoplasma gondii was demonstrable in the blood of 8 cats and in other tissues of all these 10. Four out of five 1- to 8-day-old cats fed tachyzoites by stomach tube became infected with T. gondii, and 1 became ill because of toxoplasmosis. All 19 weaned cats fed tachyzoites (poured into the mouth) became infected, and 6 died of acute toxoplasmosis 9-15 days after being fed T. gondii. Six out of 12 weaned cats fed tachyzoites by stomach tube became infected but were asymptomatic. Overall, 12 out of 26 cats observed for 19 days or more shed oocysts with a prepatent period (pp) of 19 days or more, with the sole exception of 1 cat that shed oocysts with a pp of 5 days. Enteroepithelial stages of T. gondii were not found in any cat before oocysts were shed. Cats shed up to 360 million oocysts in a day, and oocysts were shed for 4-6 days.     

Toxoplasma gondii isolates from free-ranging chickens from the United States

Prevalence of Toxoplasma gondii infection in chickens is a good indicator of the strains prevalent in their environment because they feed from ground. The prevalence of T. gondii was determined in 118 free-range chickens from 14 counties in Ohio and in 11 chickens from a pig farm in Massachusetts. Toxoplasma gondii antibodies (> or = 1: 5) were found using the modified agglutination test (MAT) in 20 of 118 chickens from Ohio. Viable T. gondii was recovered from 11 of 20 seropositive chickens by bioassay of their hearts and brains into mice. The parasite was not isolated from tissues of 63 seronegative (< or = 1:5) chickens by bioassay in cats. Hearts, brains, and muscles from legs and breast of the 11 chickens from the pig farm in Massachusetts were fed each to a T. gondii-negative cat. Eight cats fed chicken tissues shed oocysts; the 3 cats that did not shed oocysts were fed tissues of chickens with MAT titers of 1:5 or less. Tachyzoites of 19 isolates of T. gondii from Ohio and Massachusetts were considered avirulent for mice. Of 19 isolates genotyped, 5 isolates were type II and 14 were type III; mixed types and type I isolates were not found.     

Characterization of Toxoplasma gondii isolates in free-range chickens from Argentina

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 61 free-range chickens (Gallus domesticus) from provinces of Santiago del Estero and Entre Rios, Argentina was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT) and were found in 25 chickens; titers were 1:5 in 6 chickens, 1:10 in 1 chicken, 1:20 in 2 chickens, 1:40 in 1 chicken, 1:80 in 2 chickens, 1:60 in 4 chickens, 1:120 in 2 chickens, 1:640 in 3 chickens, and 1: 1,280 or higher in 4 chickens. Hearts, pectoral muscles, and brains of 22 seropositive (MAT 1:10 or higher) chickens were bioassayed individually in mice. Tissue from 39 chickens with titers of 1:5 or less were pooled and fed to 3 T. gondii-free cats. Feces of cats were examined for oocysts, but none was found. Toxoplasma gondii was isolated from 17 of 22 chickens with MAT titers of 1:10 or higher. Genotyping of these 17 isolates using polymorphisms at the SAG2 locus indicated that 4 were Type I, 3 were Type II, and 10 were Type III. Toxoplasma gondii isolates (2 Type I and I Type III) from 3 chickens were virulent for mice and 1 Type I was not mouse virulent. Prevalence of T. gondii antibodies in chickens varied among regions, being 3 times greater in the humid Pampeana region (61.2%) than in the semiarid plain of Santiago del Estero (20%).     

High prevalence of toxoplasmosis in cats from Egypt: isolation of viable Toxoplasma gondii, tissue distribution, and isolate designation

Cats are important in the epidemiology of Toxoplasma gondii because they are the only hosts that excrete environmentally resistant oocysts in feces. In the present study, 158 feral cats from Giza, Egypt, were examined for T. gondii infection. Antibodies to T. gondii were found in 97.4% with the modified agglutination test. Viable T. gondii was isolated from tissues (brain, heart, tongue) of 115 of 137 cats by bioassay in mice. These isolates were designated TgCatEg 1-115; none of these isolates was virulent to out-bred Swiss Webster mice. Of the 112 seropositive cats whose tissues were bioassayed individually, T. gondii was isolated from the hearts of 83 (74.1%), tongues of 53 (47.3%), and brains of 36 (32.1%). Toxoplasma gondii oocysts were not detected in rectal contents of any of the 158 cats, probably related to high seropositivity (chronic infection) of cats surveyed. The high prevalence of T. gondii in feral cats in Egypt reported here indicates a high environmental contamination with oocysts.     

Isolation, tissue distribution, and molecular characterization of Toxoplasma gondii from free-range chickens from Guatemala

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 50 free-range chickens (Gallus domesticus) from Guatemala was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). Antibodies were found in 37 (74%) chickens with titers of 1:5 (11), 1:10 (7), 1:20 (11), 1:40 (1), 1:80 (1), 1:160 (3), 1:1,280 (2), and 1:2,560 (1). Hearts, pectoral muscles, and brains of 19 chickens with MAT titers of 1:20 or more were bioassayed individually in mice. Tissues from the remaining 31 chickens with titers of 1:10 or lower were pooled and fed to 4 T. gondii-free cats (13 chickens with titers of less than 1:5 to 1 cat, 11 chickens with titers of 1:5 to 2 cats, and 7 chickens with titers of 1:10 to 1 cat). Feces of cats were examined for oocysts; they did not shed oocysts. Toxoplasma gondii was isolated from 8 chickens with MAT titers of 1:20 or more (from 1 of 11 chickens with a titer of 1:20 and all 7 chickens with a titer of 1:80 or more) from the heart, brain, and pectoral muscle (3); heart and pectoral muscle (1); and heart alone (4). Genotyping of these 8 isolates with the SAG2 locus indicated that 5 were type III and 3 were type 1. This is the first report of isolation of T. gondii from chickens from Guatemala.     

Isolation, tissue distribution, and molecular characterization of Toxoplasma gondii from chickens in Grenada, West Indies

The prevalence of Toxoplasma gondii in free-range chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 102 free-range chickens (Gallus domesticus) from Grenada was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). Antibodies were found in 53 (52%) chickens with titers of 1:5 in 6, 1:10 in 4, 1:20 in 4, 1:40 in 4, 1:80 in 15, 1:160 in 9, 1: 320 in 5, 1:640 in 4, and 1:1,280 or greater in 2. Hearts, pectoral muscles, and brains of 43 seropositive chickens with MAT titers of 1:20 or greater were bioassayed individually in mice. Tissues of each of 10 chickens with titers of 1:5 and 1:10 were pooled and bioassayed in mice. Tissues from the remaining 49 seronegative chickens were pooled and fed to 4 T. gondii-free cats. Feces of cats were examined for oocysts; they did not shed oocysts. T. gondii was isolated from 35 of 43 chickens with MAT titers of 1:20 or greater; from the hearts, brains, and pectoral muscles of 2, hearts and brains of 20, from the hearts alone of 11, and brains alone of 2. T. gondii was isolated from 1 of 10 chickens with titers of 1:5 or 1:10. All 36 T. gondii isolates were avirulent for mice. Genotyping of these 36 isolates using polymorphisms at the SAG2 locus indicated that 29 were Type III, 5 were Type I, 1 was Type II, and 1 had both Type I and Type III. Genetically, the isolates from Grenada were different from those from the United States; Type II was the predominant type from the United States. Phenotypically, all isolates from Grenada were avirulent for mice, whereas those from Brazil were mouse-virulent. This is the first report of isolation of T. gondii from chickens from Grenada, West Indies.     

Toxoplasma gondii infections in chickens from Venezuela: isolation, tissue distribution, and molecular characterization

The prevalence of Toxoplasma gondii, in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 46 free-range chickens (Gallus domesticus) from Venezuela was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). Antibodies were found in 16 (32%) chickens with titers of 1:5 in 1, 1:10 in 2, 1:40 in 2, 1:80 in 2, 1:160 in 2, 1:320 in 3, 1: 640 in 2, and 1:1,280 or higher in 2. Hearts, pectoral muscles, and brains of 13 chickens with MAT titers of 1:40 or more were bioassayed individually in mice. Tissues of each of 3 chickens with titers of 1:5 or 1:10 were pooled and bioassayed in mice. Tissues from the remaining 30 seronegative chickens were pooled and fed to 1 T. gondii-free cat. Feces of the cat were examined for oocysts; it did not shed oocysts. Toxoplasma gondii was isolated from 12 of 13 chickens with MAT titers of 1:40 or more. Toxoplasma gondii was isolated from pooled tissues of 1 of 2 chickens with titers of 1:10. Eight of these 13 isolates were virulent for mice. Genotyping of 13 of these isolates using the SAG2 locus indicated that 10 were type III, and 3 were type II. Phenotypically and genetically these isolates were different from T. gondii isolates from North America and Brazil. This is the first report of isolation of T. gondii from chickens from Venezuela.     

Toxoplasma gondii isolates of free-ranging chickens from Rio de Janeiro, Brazil: mouse mortality, genotype, and oocyst shedding by cats

Most isolates of Toxoplasma gondii can be grouped into 3 genetic lineages. In the present study, 67 isolates of T. gondii were obtained by bioassay in mice inoculated with brains and hearts of 96 asymptomatic chickens from an area highly endemic to human infection in Rio de Janeiro, Brazil. Of the 48 isolates genotyped using the SAG2 locus, 34 (70%) were of type I and 13 (27%) were of type III. No isolate of type II was recovered. Isolates from 1 chicken contained a type I and type III mixed infection, indicating natural multiparasite infection in the same animal. Cats fed mice infected with 11 type I strains shed 19-535 million oocysts in their feces, indicating that type I isolates can circulate in the environment.     

Molecular characterization of Toxoplasma gondii isolates from cats in Spain

Cats are important in the epidemiology of Toxoplasma gondii because felids are the only definitive hosts that can excrete environmentally resistant oocysts. Fresh samples of brain from 103 Spanish cats with antibodies to T. gondii were analyzed for T. gondii DNA using nested-PCR; 47 (45.5%) were found to be positive. Further characterization of DNA from 46 cats using RFLP-PCR at the 3' and 5' ends of the SAG2 locus revealed that 12 (26%) isolates were Type I and 34 (74%) were Type II; no Type III were found, and the 47th sample could not be classified to its genetic type. In addition, T. gondii was also isolated by bioassay in mice from 42 of 103 seropositive cats. This is the first report of T. gondii characterization from cats in Spain.     

Isolation of Toxoplasma gondii from the keel-billed toucan (Ramphastos sulfuratus) from Costa Rica

Pectoral muscles from a captive keel-billed toucan (Ramphastos sulfuratus) from Costa Rica were fed to a Toxoplasma gondii-free cat, and the cat shed oocysts. Laboratory mice fed these oocysts developed antibodies to T. gondii in their sera and T. gondii tissue cysts in their brains. The DNA extracted from the brains of infected mice was characterized using 10 polymerase chain reaction-restricted fragment length polymorphic markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). The isolate designated TgRsCrl was found to be non-clonal with Type I, II, and III alleles at different loci. This is the first isolation of T. gondii from this host.     

Experimental infections of Sarcocystis cruzi, Sarcocystis tenella, Sarcocystis capracanis and Toxoplasma gondii in red foxes (Vulpes vulpes)

Four littermate 6-wk-old red foxes (Nos. 1-4) were fed Toxoplasma gondii, Sarcocystis cruzi, S. tenella and S. capracanis. One littermate fox (No. 5) served as the control. Two foxes (Nos. 1, 2) were fed tissue cysts of T. gondii and two foxes (Nos. 3, 4) were fed oocysts of T. gondii. Twenty-one to 42 days later, the same five foxes were used to test the infectivity of meat of goat, sheep, and ox experimentally inoculated with Sarcocystis. Fox 2 was fed goat meat and shed S. capracanis-like sporocysts 10 days later. Foxes 3 and 4 were fed beef, and they shed S. cruzi-like sporocysts 9 days later. Fox 5 was fed sheep meat and shed S. tenella-like sporocysts 8 days later. Foxes were killed between 36 and 55 days of the experiment and their tissues were inoculated into mice to recover T. gondii. All foxes remained clinically normal and T. gondii was recovered from all inoculated foxes and not from the control. Sarcocystis sporocysts from foxes induced lethal infections in goats, sheep, and ox. The sporocysts, meronts, merozoites, and sarcocysts of fox-derived parasites were similar to those derived from coyotes or dogs. It was concluded that the red fox can act as a final host for the three pathogenic species of Sarcocystis in cattle, sheep, and goats.     

Tissue distribution and molecular characterization of chicken isolates of Toxoplasma gondii from Peru

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii antibodies in sera of 50 free-range chickens (Gallus domesticus) from Peru was 26% on the basis of the modified agglutination test (MAT). Hearts, pectoral muscles, and brains of seropositive (MAT > or =1:5) chickens were bioassayed individually in mice. Tissues from the remaining 37 seronegative chickens were pooled and fed to 2 T. gondii-free cats. Feces of cats were examined for oocysts; they did not shed oocysts. Toxoplasma gondii was isolated from the hearts of 10 seropositive chickens but not from their brains and pectoral muscles. Genotyping of these isolates using the SAG2 locus indicated that 7 isolates were type I and 3 were type III. Six of the 7 type-I isolates were avirulent for mice, which was unusual because type-I isolates are considered virulent for mice. The T. gondii isolates were from chickens from different properties that were at least 200 m apart. Thus, each isolate is likely to be different. This is the first report of isolation of T. gondii from chickens from Peru.     

Low virulence of oocysts of Czech Toxoplasma gondii isolates on the basis of biological and genetic characteristics

The virulence of the oocysts of 7 Czech Toxoplasma gondii isolates was tested. The oocysts were obtained by experimental infection of cats with the tissue cysts of T. gondii isolates from dogs, cats, and rabbits. The cats shed the oocysts in feces, with prepatent periods of 3-5 days postinfection (PI); the patent period was 7-18 days. The number of oocysts shed varied between 0.94 million and 47 million, with 0.66 million-39 million oocysts found in the daily samples of excrement. The cats ceased oocyst production at 11-22 days PI. Sporulated oocysts were used to prepare infective doses of 1 to 10(5) oocysts for oral infection of 10 mice. Deoxyribonucleic acid isolated from 4 T. gondii isolates was used in polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for amplification of the ROP1 gene and restriction of the product of amplification by restriction endonuclease DdeI. On the basis of their biological characteristics, all 7 isolates belonged to the group of "avirulent" strains. In the PCR-RFLP tests, 2 isolates, K9 and K19, showed an "avirulent" strain pattern.     

First biologic and genetic characterization of Toxoplasma gondii isolates from chickens from Africa (Democratic Republic of Congo, Mali, Burkina Faso, and Kenya)

The prevalence of Toxoplasma gondii in free-ranging chickens (Gallus domesticus) is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. In the present study, prevalence of T. gondii in chickens from Democratic Republic of Congo, Mali, Burkina Faso, and Kenya is reported. The prevalence of T. gondii antibodies in sera of 50 free-range chickens from Congo was 50% based on the modified agglutination test (MAT); antibody titers were 1:5 in 7, 1:10 in 7, 1:20 in 6, 1:40 in 1, and 1:160 or more in 4 chickens. Hearts, pectoral muscles, and brains of 11 chickens with titers of 1:20 or more were bioassayed individually in mice; T. gondii was isolated from 9, from the hearts of 9, brains of 3, and muscles of 3 chickens. Tissues of each of the 14 chickens with titers of 1:5 or 1:10 were pooled and bioassayed in mice; T. gondii was isolated from 1 chicken with a titer of 1:10. Tissues from the remaining 25 seronegative chickens were pooled and fed to 1 T. gondii-free cat. Feces of the cat were examined for oocysts, but none was seen. The results indicate that T. gondii localizes in the hearts more often than in other tissues of naturally infected chickens. Genotyping of these 10 isolates using the SAG2 locus indicated that 8 were isolates were type III, 1 was type II, and 1 was type I. Two isolates (1 type I and 1 type III) were virulent for mice. Toxoplasma gondii was isolated by mouse bioassay from a pool of brains and hearts of 5 of 48 chickens from Mali and 1 of 40 chickens from Burkina Faso; all 6 isolates were avirulent for mice. Genetically, 4 isolates were type III and 2 were type II. Sera were not available from chickens from Mali and Burkina Faso. Toxoplasma gondii antibodies (MAT 100 or more) were found in 4 of 30 chickens from Kenya, and T. gondii was isolated from the brain of 1 of 4 seropositive chickens; this strain was avirulent for mice and was type II. This is the first report on isolation and genotyping of T. gondii from any source from these 4 countries in Africa.     

Isolation of viable Toxoplasma gondii from feral guinea fowl (Numida meleagris) and domestic rabbits (Oryctolagus cuniculus) from Brazil

Toxoplasma gondii was isolated from a feral guinea fowl (Numida meleagris) and domestic rabbits (Oryctologus cuniculus) from Brazil for the first time. Serum and brains from 10 guinea fowl and 21 rabbits from Brazil were examined for T. gondii infection. Antibodies to T. gondii were found in 2 of 10 fowl and 2 of 21 rabbits by the modified agglutination test (titer 1∶25 or higher). Viable T. gondii (designated TgNmBr1) was isolated from 1 of the 2 seropositive fowl by bioassay in mice but not from the 8 seronegative fowl by bioassay in cat. Viable T. gondii was isolated from both seropositive rabbits (designated TgRabbitBr1, TgRabbitBr2) by bioassay in mice from 1 and by bioassay in cat from the other. The TgRabbitBr1 strain was highly virulent for out-bred mice; mice fed 1 infective oocyst died of acute toxoplasmosis. The remaining 2 isolates were relatively avirulent for mice; lethal dose for mice was 10,000 oocysts. All 3 isolates were grown in cell culture, and tachyzoite-derived DNA were genotyped using 10 PCR-restriction fragment length polymorphism markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). The TgNmBr1 was found to be clonal Type II, a rare finding in Brazil in any host. The rabbit isolates were atypical, similar to isolates from cats from Brazil (TgRabbitBr1 was identical to TgCatBr5, and TgRabbitBr2 was identical to TgCatBr1, a common genotype in Brazil denoted type BrII). This is the first genetic characterization of T. gondii isolates from the rabbits and guinea fowl in Brazil and the first host record for T. gondii in the guinea fowl.     

Biological and molecular characterizations of Toxoplasma gondii strains obtained from southern sea otters (Enhydra lutris nereis)

Toxoplasma gondii was isolated from brain or heart tissue from 15 southern sea otters (Enhydra lutris nereis) in cell cultures. These strains were used to infect mice that developed antibodies to T. gondii as detected in the modified direct agglutination test and had T. gondii tissue cysts in their brains at necropsy. Mouse brains containing tissue cysts from 4 of the strains were fed to 4 cats. Two of the cats excreted T. gondii oocysts in their feces that were infectious for mice. Molecular analyses of 13 strains indicated that they were all type II strains, but that they were genetically distinct from one another.     

Biological and genetic characterisation of Toxoplasma gondii isolates from chickens (Gallus domesticus) from S?o Paulo, Brazil: unexpected findings.

In spite of a wide host range and a world wide distribution, Toxoplasma gondii has a low genetic diversity. Most isolates of T. gondii can be grouped into two to three lineages. Type I strains are considered highly virulent in outbred laboratory mice, and have been isolated predominantly from clinical cases of human toxoplasmosis whereas types II and III strains are considered avirulent for mice. In the present study, 17 of 25 of the T. gondii isolates obtained from asymptomatic chickens from rural areas surrounding S?o Paulo, Brazil were type I. Antibodies to T. gondii were measured in 82 chicken sera by the modified agglutination test using whole formalin-preserved tachyzoites and mercaptoethanol and titres of 1:10 or more were found in 32 chickens. Twenty-two isolates of T. gondii were obtained by bioassay in mice inoculated with brains and hearts of 29 seropositive (> or =1:40) chickens and three isolates were obtained from the faeces of cats fed tissues from 52 chickens with no or low levels (<1:40) of antibodies. In total, 25 isolates of T. gondii were obtained by bioassay of 82 chicken tissues into mice and cats. All type I isolates killed all infected mice within 4 weeks whereas type III isolates were less virulent to mice. There were no type II strains. Tissue cysts were found in mice infected with all 25 isolates and all nine type I isolates produced oocysts. Infected chickens were from localities that were 18-200 km apart, indicating no common source for T. gondii isolates. This is the first report of isolation of predominantly type I strains of T. gondii from a food animal. Epidemiological implications of these findings are discussed.     

Sporulation and Survival of Toxoplasma gondii Oocysts in Seawater

ABSTRACT. We have been collaborating since 1992 in studies on southern sea otters ( Enhdyra lutris nereis ) as part of a program to define factors, which may be responsible for limiting the growth of the southern sea otter population. We previously demonstrated Toxoplasma gondii in sea otiers. We postulated that cat feces containing oocysts could be entering the marine environment through storm run-off or through municipal sewage since cat feces are often disposed down toilets by cat owners. The present study examined the sporulation of T. gondii oocysts in seawater and the survival of sporulated oocysts in seawater. Unsporulated oocysts were placed in 1.5 ppt artificial seawater, 32 ppt artificial seawater or 2% sulfuric acid (positive control) at 24 C in an incubator. Samples were examined daily for 3 days and development monitored by counting 100 oocysts from each sample. From 75 to 80% of the oocysts were sporulated by 3 days post-inoculation under all treatment conditions. Groups of 2 mice were fed 10,000 oocysts each from each of the 3 treatment groups. All inoculated mice developed toxoplasmosis indicating that oocysts were capable of sporulating in seawater. Survival of sporulated oocysts was examined by placing sporulated T. gondii oocysts in 15 ppt seawater at room temperature 22–24 C (RT) or in a refrigerator kept at 4 C. Mice fed oocysts that had been stored at 4C or RT for 6 months became infected. These results indicate that T. gondii oocysts can sporulate and remain viable in seawater for several months.