Effect of Feline Immunodeficiency Virus Infection on Toxoplasma gondii-specific Humoral and Cell-mediated Immune Responses of Cats with Serologic Evidence of Toxoplasmosis

Serum samples from 89 cats with serologic evidence of toxoplasmosis were identified by using an enzyme-linked immunosorbent assay (ELISA) that detected Toxoplasma gondii -specific immunoglobulin M (IgM) or T. gondii -specific immunoglobulin G (IgG). Concurrent feline immunodeficiency virus (FIV) infection was detected in 36 cats using an ELISA for detection of FIV-specific IgG. The majority of the cats in both the FIV-seropositive and FIV-seronegative groups were male and >5 years of age. FIV-seropositive cats were more likely to have T. gondii IgM titers without IgG ( P > 0.05) or any T. gondii IgM titer ( P > 0.05) than were FIV-seronegative cats. FIV-seronegative cats (1328) had a higher T. gondii IgG geometric mean titer than did FIV-seropositive cats (724) and were more likely to have T. gondii IgG titers 1:2048 than were FIV-seropositive cats ( P > 0.05). Cats with serologic evidence of both T. gondii and FIV infections had persistent T. gondii IgM titers for >12 weeks. Lymphoblast transformation in response to concanavalin A, T. gondii -specific intracellular antigens, and T. gondii -specific secretory antigens was compared in T. gondii seropositive and FIV-seronegative cats, cats with serologic evidence of T. gondii infection alone, and cats with serologic evidence of concurrent FIV and T. gondii infections. Lymphocytes from all but one cat in the FIV-seropositive group responded to concanavalin A. Whereas lymphocytes from FIV-seronegative cats with serologic evidence of toxoplasmosis responded to T. gondii -specific antigens, four of five of the FIV-seropositive cats with concurrent serologic evidence of toxoplasmosis did not.     

Genetic and biologic characterization of Toxoplasma gondii isolates of cats from China

Cats are important in the epidemiology of Toxoplasma gondii infection because they are the only hosts that can excrete the environmentally resistant oocysts. In the present study, prevalence of T. gondii was determined in serum, feces, and tissues of 34 cats from People's Republic of China. Antibodies to T. gondii were assayed by the modified agglutination test and found in 27 of 34 (79.4%) cats with titers of 1:40 in one, 1:80 in one, 1:160 in three, 1:320 in three, 1:640 in eight, and 1:1280 or higher in 11 cats. T. gondii oocysts were not found in feces of any cat as ascertained by bioassay in mice. Tissues (brain, heart, and tongue) of 27 seropositive cats were pooled and bioassayed in mice (8 cats) or cats (19 cats). T. gondii was isolated from tissues of 17 of 27 seropositive cats. Genotyping of these 17 T. gondii isolates using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and a new SAG2, and an apicoplast marker Apico revealed two genotypes. This is the first report of genetic typing of T. gondii isolates from cats from China.     

Serologic prevalence of selected infectious diseases in cats with uveitis.

Serologic evidence of infection by Toxoplasma gondii, feline leukemia virus, feline coronaviruses, or feline immunodeficiency virus (FIV) is commonly found in cats with uveitis. Serum samples from 124 cats with uveitis were assayed by use of ELISA for the detection of T gondii-specific immunoglobulin M (IgM), IgG, and circulating antigens (Ag), as well as an ELISA for feline leukemia virus Ag, an ELISA for antibodies to FIV, and an indirect fluorescent antibody assay for antibodies to feline coronaviruses. Serologic evidence of infection by 1 or more of the infectious agents was detected in 83.1% of the samples. Serologic evidence of T gondii infection, defined as the detection of T gondii-specific IgM, IgG, or Ag in serum, was found in 74.2% of the samples. The seroprevalence of T gondii infection was significantly greater in cats with uveitis than in healthy cats from a similar geographic area. Serum samples from cats with serologic evidence of both T gondii and FIV infections were more likely to contain T gondii-specific IgM without IgG than samples from cats with serologic evidence of T gondii infection alone. Cats with serologic evidence of FIV and T gondii coinfection had a higher T gondii-specific IgM titer geometric mean and a lower T gondii-specific IgG titer geometric mean than did cats with serologic evidence of T gondii infection alone. Serologic evaluation for T gondii infection should include assays that detect IgM, IgG, and Ag, particularly in cats coinfected with FIV.     

A computer simulation of the prevention of the transmission of Toxoplasma gondii on swine farms using a feline T. gondii vaccine

Transmission of Toxoplasma gondii on swine farms was investigated using a deterministic dynamic computer simulation model. A primary focus was to evaluate a feline T. gondii vaccine. Animal populations (swine and cats) were compartmentalized based on the stage of T. gondii infection. Simulations were run under conditions of closed and equilibrium population size. Model parameters were varied in a factorial experimental design to test the following hypotheses: T. gondii infection in finishing pigs decreases with (1) vaccination of susceptible cats, (2) an increase in the proportion of cats captured for vaccination, (3) a decrease in the initial number of cats, (4) a decrease in the initial T. gondii prevalence in cats and (5) a decrease in oocyst-survival time. Seeding conditions included a total of 10, 20, 30, 40 or 50 cats, initial T. gondii prevalences in cats of 30, 60 or 90%, vaccination of 0, 50 or 75% of the cats and two vaccination schedules (the field schedule from a prior trial and a weaning-vaccination schedule). Simulations were run at oocyst-survival times of 52, 39 and 26 weeks. T. gondii prevalence in finishing pigs was recorded every week for 10 years. The probability of elimination of T. gondii from finishing pigs increased with a decrease in the number of cats and a decrease in oocyst-survival time.The last-year average prevalence was used as the outcome in a multiple linear regression analysis. Decreased T. gondii prevalence in finishing pigs was the result of a decrease in the initial number of cats on the farm (squared semipartial correlation coefficient (sr(2))=47%), decreased oocyst survival (sr(2)=35%), using the weaning-vaccination schedule (sr(2)=7%) and vaccination versus non-vaccination (sr(2)=5%). Unexpectedly, the initial T. gondii prevalence in cats had no effect on T. gondii prevalence in finishing pigs. The simulation supports the field trial indicating vaccine effectiveness. However, vaccination had less impact on decreasing T. gondii infection in finishing pigs than a decrease in the number of farm cats.     

Inoculation with Bartonella henselae followed by feline herpesvirus 1 fails to activate ocular toxoplasmosis in chronically infected cats

Infection by Toxoplasma gondii is very common in cats although most remain disease free. The factors that trigger development of uveitis in some cats infected with T gondii have not been elucidated, but infection by more than one organism may be contributory. In this study, cats chronically infected with T gondii were inoculated with Bartonella henselae followed by FHV-1 to test the hypothesis that immune stimulation by multiple infections will reactivate ocular toxoplasmosis. Anterior uveitis and chorioretinitis were not detected in the cats with chronic T gondii infection thus allowing rejection of the hypothesis using this experimental design.     

Nested PCR-based detection of Toxoplasma gondii in German shepherd dogs and stray cats in South Korea

The prevalence of Toxoplasma gondii was surveyed by using a nested polymerase chain reaction (PCR) that was targeted to T. gondii B1 gene in German shepherd dogs and stray cats. Sixty-four (46.3%) out of 138 German shepherd dogs and 50 (47.2%) out of 106 stray cats were tested positive by the nested PCR assay, respectively. There was no significant difference in gender or age in German shepherd dogs and stray cats. In the five positive dogs and five positive cats, the nucleotide partial sequence of the T. gondii B1 gene was identified by direct sequence analysis. All the sequences were identical to each other and the corresponding sequence, T. gondii B1 gene (Accession No. AF179871). The results suggest that the prevalence of T. gondii is high, and the nested PCR assay is useful for early detection of T. gondii for asymptomatic dogs and cats.     

Isolation and characterization of Toxoplasma gondii strains from stray cats revealed a single genotype in Beijing, China

Cats are essential in the epidemiology of Toxoplasma gondii because they are the only hosts that can excrete the environmentally resistant oocysts in nature. This study was aimed to determine the seropositivity, distribution of genotypes and mouse virulence of T. gondii from stray cats in Beijing, China. A total of 64 serum samples, 23 feces and tissue samples were collected from stray cats in Beijing. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). 57.8% (37/64) of these stray cats had titers of 1:20 or higher and were considered positive with infection. T. gondii oocysts were not found in feces of the 23 cats. Tissues of 23 cats were bioassayed in mice and 11 T. gondii isolates were obtained. The genotype of these isolates were identified by 11 PCR-RFLP markers, including SAG1, (3'+5')SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and an apicoplast marker, Apico. Only one genotype was identified. This genotype, designated as ToxoDB genotype #9, was previously reported in cats, pigs and human from Guangdong and Gansu provinces in China and animals from a few other countries. To determine mouse virulence of this lineage of parasites, one isolate was randomly selected and inoculated into BABL/c mice, the result showed that it is intermediately virulent to mice. These results indicated that an atypical, intermediately virulent T. gondii lineage is widespread in China. The high seropositivity of T. gondii in stray cats posts potential risk of transmission of the parasite to human population in the region.     

In vitro isolation and seroprevalence of Toxoplasma gondii in stray cats and pigeons in Lisbon, Portugal

Oral contamination with Toxoplasma gondii oocysts shed by cats into the environment has been linked to severe outbreaks of human toxoplasmosis. Pigeons (Columba livia) are highly susceptible to oral infection with oocysts and indirectly indicate soil contamination, since they feed from the ground. A seroprevalence study was performed on cats and pigeons captured in the city of Lisbon. Serum samples collected from 1507 pigeons captured at 64 feeding sites and 423 stray cats were screened for antibodies anti-T. gondii using a commercial direct agglutination test. Seroprevalence in pigeons was 2.6% (39/1507) (95% CI: 1.9-3.5%) and 37.5% (24/64) of pigeon flocks sampled showed to be infected with T. gondii. The proportion of infected pigeons within seropositive flocks ranged between 4.8% and 21.1%. Among cats, seroprevalence was 44.2% (187/423) (95% CI: 39.5-49.1%). Isolation of T. gondii from animal tissues was attempted by in vitro assay. Inoculation of brain homogenates from 20 pigeons and 56 cats into Vero cell cultures allowed isolation of T. gondii from 13 pigeons (65%) and 15 cats (26.8%). Inoculation of muscle homogenates (heart and limbs) prepared by acid-peptic digestion from a subset of 15 cats resulted in the recovery of T. gondii from 10 cats (66.7%).     

Seroprevalence of Toxoplasma gondii antibodies in clinically ill cats in the United States

OBJECTIVE: To determine regional seroprevalence estimates of Toxoplasma gondi-specific IgM and IgG in clinically ill cats throughout the United States. Sample Population-Sera from 12,628 clinically ill, client-owned cats. PROCEDURE: Toxoplasma gondii-specific IgM and IgG antibodies were detected by use of ELISAs. Sera from clinically ill cats previously submitted for T. gondii antibody testing were sequentially selected from our serum bank and the sample submission paperwork reviewed. The country was divided into 12 geographic regions. Overall prevalence as well as prevalence for each region, age group, season, sex (male vs female), and breed (domestic shorthair vs other) was calculated. Data were analyzed by logistic regression analysis. RESULTS: Overall, 31.6% of the cats were seropositive for T. gondii-specific IgM, IgG, or both. Percentage of cats seropositive for T. gondii antibodies ranged from 16.1% (southwestern United States) to 43.5% (northeastern United States). As age increased, odds of positive T. gondii antibody assay results (IgM alone, IgG alone, and any combination of IgM or IgG) increased. Males were more likely than females to be seropositive for T. gondii antibodies (IgG alone and any combination of IgM or IgG). Domestic shorthair cats were more likely than other breeds to be seropositive for T. gondii antibodies (IgM alone, IgG alone, and any combination of IgM or IgG). CONCLUSIONS AND CLINICAL RELEVANCE: Toxoplasma gondii-specific antibodies are common in serum samples of clinically ill cats from all regions of the United States. Seroprevalence increases as cats age and is higher in male and domestic shorthair cats, compared with females and other breeds.     

Genetic and biologic characteristics of Toxoplasma gondii infections in free-range chickens from Austria

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 free-range chickens (Gallus domesticus) from 11 Bio-farms in Austria was determined. Antibodies to T. gondii assayed by the modified agglutination test (MAT) were found in 302 of 830 (36.3%) chickens with titers of 1:10 in 50, 1:20 in 69, 1:40 in 53, 1:80 in 40, 1:160 or higher in 90. Hearts of 218 chickens with MAT titers of 10 or higher were bioassayed individually in mice. Tissues from 1183 chickens were pooled and fed to 15, T. gondii-free cats. Feces of the cats were examined for oocysts; 11 cats shed T. gondii oocysts. T. gondii was isolated from 56 chickens by bioassay in mice. Thus, there were 67 isolates of T. gondii from these chickens. Genotyping of these 67 isolates using the SAG2 locus indicated that all 33 were Type II. Phenotypically and genetically these isolates were different from T. gondii isolates from Brazil. None of the isolates was virulent for mice. This is the first report of isolation of T. gondii from chickens from Austria.     

Toxoplasma gondii antibody in domestic cats in Melbourne

OBJECTIVES: To determine the prevalence of Toxoplasma gondii in a population of domestic cats in Melbourne. DESIGN: An ELISA assay was used to measure T gondii antibody titres in 103 cats from north-eastern Melbourne. Cats were obtained from outer suburban areas (less than 30 km from the Melbourne GPO) and from rural areas (more than 30 km from the Melbourne GPO). RESULTS: Thirty-nine percent of cats were positive for T gondii IgG. Older cats tended to have higher antibody titres. There was no significant difference in the T gondii antibody titres between males and females, or between cats living in urban areas and cats from rural areas. CONCLUSIONS: A significant proportion of cats from Melbourne have been exposed to Toxoplasma. This may have implications for the health of wildlife and humans.     

Toxoplasma gondii in Romanian household cats: evaluation of serological tests, epidemiology and risk factors

Felines are the key species in the epidemiology of Toxoplasma gondii infection, as they are the definitive host of the parasite and are the only species that can shed resistant oocysts in the environment. Different assays are in use for the detection of antibodies against T. gondii in cats. However, assay validation studies are limited. For that reason it was our aim to first evaluate 6 serological tests (one commercial and 2 in-house ELISAs, ImmunoComb, IFAT and MAT) for antibodies (IgG) against T. gondii in cats by Bayesian modeling. Factors associated with seropositivity were evaluated by bivariable and multivariable methods. The test evaluation indicated the commercial ELISA had the highest Youden Index. The estimated sensitivity ranged between 95.7% and 97.1% and the specificity between 97.3% and 97.6%. Using this commercial ELISA 111 out of 236 cats (47%) were positive for T. gondii antibodies. Two peaks in the percentage of strong positive samples (S/P≥200) were observed, around 10-months-old and 8-years-old. In bivariable analysis the seroprevalence was significantly higher in adult cats, cats with mixed diet, with outdoor access, in cats from a rural area and in cats from centre and north-western Romania. Adult age (adults: OR 6.98; 95% CI: 2.02-24.14 and geriatrics (cats older than 10-years): OR 12.01; 95% CI: 1.60-90.15) and outdoor access (OR 6.38; 95% CI: 2.32-17.53) remained significant risk factors in the multivariable logistic regression analysis. Our results suggest that T. gondii infection is common in household cats in Romania, and especially in those with outdoor access.     

Detection of Toxoplasma gondii in the milk of experimentally infected lactating cats.

Tachyzoites of Toxoplasma gondii have been found in the milk of sheep, goats, cows and mice and infection by ingestion of raw goat milk has been documented in humans. Lactational transmission from infected cats to their kittens is suspected but the organism has not been detected in the milk. The purpose of this study was to demonstrate the presence of T. gondii in the milk of experimentally infected cats. Pregnant specific pathogen free cats were inoculated orally with T. gondii at various times prior to parturition. Feces were examined for oocyst shedding after sugar solution centrifugation. Milk was collected for polymerase chain reaction (PCR) and bioassay in mice. T. gondii was detected in the milk of five of six cats by either bioassay or PCR.     

Failure of FIV-infected cats to control Toxoplasma gondii correlates with reduced IL2, IL6, and IL12 and elevated IL10 expression by lymph node T cells

Increased susceptibility to intracellular pathogens in HIV-infected individuals and FIV-infected cats is attributed to a defective T-helper 1 (Th1) immune response. However, little is known about specific cytokine responses to secondary pathogens. To address this question, control and FIV-infected cats were challenged with Toxoplasma gondii, and lymph node cells analyzed for cytokine mRNA expression. Twenty-four weeks post-FIV infection, prior to T. gondii challenge, IL2 and IL12 mRNAs were depressed, whereas IL10 and IFNgamma mRNAs were increased in CD4+ and CD8+ subsets. Following T. gondii challenge, control cats showed increased expression of IL2, IFNgamma, IL10, IL12, and IL6 mRNAs. In contrast, IL2, IL6, IFNgamma, and IL12 mRNAs were suppressed in FIV-T. gondii co-infected cats, whereas IL10 remained at the high prechallenge levels. IFNgamma and IL10 mRNAs were produced by both CD4+ and CD8+ cells in FIV-T. gondii cats. Elevated IL10 may suppress a Th1 cytokine response to T. gondii challenge.     

Comparative infectivity of oocysts and bradyzoites of Toxoplasma gondii for intermediate (mice) and definitive (cats) hosts

Tachyzoites, bradyzoites (in tissue cysts), and sporozoites (in oocysts) are the three infectious stages of Toxoplasma gondii. The prepatent period (time to shedding of oocysts after primary infection) varies with the stage of T. gondii ingested by the cat. The prepatent period (pp) after ingesting bradyzoites is short (3-10 days) while it is long (18 days or longer) after ingesting oocysts or tachyzoites. The conversion of bradyzoites to tachyzoites and tachyzoites to bradyzoites is biologically important in the life cycle of T. gondii and it has been proposed that the pp can be used to study stage conversion. In the present study, infectivity of oocysts and bradyzoites released from tissue cysts of a recent isolate of T. gondii, TgCkAr23, to cats and mice was compared. Ten-fold dilutions of oocysts or bradyzoites were administered orally to cats, and orally and subcutaneously to mice. Of the 29 cats each fed 1-10 million oocysts only one cat shed oocysts and the pp was 23 days; all cats remained asymptomatic. In contrast, all mice administered the same 10-fold dilutions of oocysts either orally or subcutaneously died of toxoplasmosis. The results confirm that infectivity of the oocysts to cats is lower than for mice and that oocysts are non-pathogenic for cats. Of the 41 cats each fed 1-1,000 free bradyzoites, 15 shed oocysts with a short pp of 4-9 days, and all remained asymptomatic. The infectivity of bradyzoites to mice by the oral route was approximately 100 times lower than that by the subcutaneous route. The results confirm the hypothesis that the pp in cats is stage and not dose dependent, and that transmission of T. gondii is most efficient when cats consume tissue cysts (carnivory) or when intermediate hosts consume oocysts (fecal-oral transmission).     

Genetic characterization of Toxoplasma gondii isolates in dogs from Vietnam suggests their South American origin

Dogs are considered a potential risk for transmission of Toxoplasma gondii to humans because they can mechanically transmit oocysts to people and in certain parts of the world dog meat is consumed by humans. The prevalence of T. gondii in 42 dogs from rural Vietnam was determined. Antibodies to T. gondii were assayed by the modified agglutination test, and found in 21 (50%) of 42 dogs with titers of 1:20 in six, 1:40 in seven, 1:80 in two, 1:160 in two, 1:320 in two, 1:640 in one, and 1:1280 or higher in one. Hearts, tongues and brains of 21 seropositive dogs were bioassayed in cats, mice or both. Tissues from eight seropositive dogs were fed to eight T. gondii-free cats. Feces of cats were examined for oocysts. T. gondii was isolated from eight dogs by bioassay in cats. Genotyping of these eight T. gondii isolates using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and a new SAG2, and an apicoplast marker Apico revealed two genotypes. Both genotypes were previously identified from the dog isolates in Colombia, suggesting their South America origin. However, they are different from the predominant Type I, II and III lineages that are widely spread in North America and Europe. This is the first report of isolation of viable T. gondii from any host in Vietnam.     

Prevalence of chlamydia, toxoplasma, toxocara and ringworm in farm cats in south-west England

The prevalence of infection with Chlamydia psittaci, Toxoplasma gondii, Toxocara cati and Microsporum canis was examined in 51 cats on 22 sheep farms in the Bristol area. Serum antibody to C psittaci and T gondii was present in 45 per cent and 47 per cent of cats, respectively. At the time of sampling C psittaci was isolated from 6 per cent of the cats, T cati was identified in 63 per cent of faecal samples but neither T gondii nor M canis was isolated. When examined according to the farm of origin, 22.7 per cent of farms had cat populations with no evidence of infection with C psittaci or T gondii. Of the remainder, 45.5 per cent supported cat populations with evidence of both infections and 31.8 per cent had evidence of T gondii infection alone. None of the farms had cat populations with evidence of C psittaci infection alone. Two of the cats infected with C psittaci were excreting viable organisms in the faeces. The possible significance of this to the epidemiology of ovine enzootic abortion is discussed.     

Seroprevalence of Toxoplasma gondii antibodies in stray cats and dogs in the Bangkok metropolitan area, Thailand

Cats and dogs are the most popular pet animals worldwide. Cats are the natural reservoir of Toxoplasma gondii and excrete the resistant oocyst to environments. On the other hands, dogs play a role in the mechanical transmission of the parasite. Stray cats and dogs in the Bangkok metropolitan area are becoming a public concern because there is a considerable increase in their number annually. These facts indicate the risk of mechanically spreading zoonoses including toxoplasmosis to humans since human acquire the infection from infected mammals, either directly or indirectly. In the present study, the presence of T. gondii antibodies was examined in 592 cats and 427 dogs from October 2001 to September 2002 by using a latex agglutination test. T. gondii antibodies were detected in 65 (11.0%) of the 592 cats and 40 (9.4%) of the 427 dogs. The antibody titers in the positive animals ranged from 1:64 to 1:2048. Seroprevalence was significantly higher in female cats than in male cats. The present study suggested that T. gondii was widespread in the stray animals in the Bangkok metropolitan area; therefore, it is essential to control the number of stray cats and dogs in order to reduce the transmission of toxoplasmosis to animals and humans.     

Feline immunodeficiency virus, feline leukaemia virus, Toxoplasma gondii, and intestinal parasitic infections in Taiwanese cats

A population consisting of 70 breeder cats, 43 clinical cases, and 16 feral cats was examined for the presence of Toxoplasma gondii, feline immunodeficiency virus (FIV), and feline leukaemia virus (FeLV). No oocysts of T. gondii were observed in 96 faecal samples; faecal samples were not available from the feral cats. Other intestinal parasites identified included Isospora felis (three cats), Isospora rivolta (five), Dipylidium canium (two), Toxocara cati (four), Toxascaris leonina (one), and Ancylostoma sp. (two). Using a kinetics-based enzyme-linked immunosorbent assay on 117 sera including all the feral cats, nine had antibody to T. gondii antigen, three for antigens to FIV, and seven to the p27 antigen of FeLV. Of the nine cats with antibody to T. gondii, only one was also infected with FIV.     

Toxoplasma gondii infection in cats from São Paulo state, Brazil: seroprevalence, oocyst shedding, isolation in mice, and biologic and molecular characterization

Cats are the most important hosts in the epidemiology of Toxoplasma gondii infections in humans and animals. Serologic and parasitological prevalence of T. gondii were determined in 237 cats from 15 counties in S?o Paulo state, Brazil. Antibodies to T. gondii were found in a 1:25 dilution of serum of 84 (35.4%) out of 237 cats by the modified agglutination test (MAT). Samples of brain, heart, tongue, and limb muscles (total 50 g) of 71 of the seropositive cats were pooled for each cat, digested in pepsin and bioassayed in mice. Faeces (1 g) from the rectum of each cat were examined microscopically for T. gondii-like oocysts and verified by bioassay in mice; T. gondii oocysts were found in the faeces of three (1.3%) of 237 cats. T. gondii was isolated from tissue homogenates of 47 cats. The DNA obtained from these 47 tissue isolates was characterized using the SAG2 locus: 34 (72.4%) isolates were type I, 12 (25.5%) were type III and one (2.1%) was mixed with types I and III. No type II isolates were detected. Most (23/34) of the type I isolates killed all infected mice and 7 of 12 type III isolates did not kill infected mice. Characterization of the SAG2 locus directly from tissue homogenates from 37 of 46 cats was successful. Genotypes obtained from these primary samples were the same as those from the corresponding isolates obtained in mice. Genotyping of the three oocyst isolates revealed that two were type I and one was type III. Molecular and biologic characteristics of T. gondii isolates from animals from Brazil are different from those from other parts of the world.