Seroprevalence against Toxoplasma gondii in domiciled cats in Japan

A serological survey with latex agglutination test to detect anti-Toxoplasma gondii antibodies was conducted on 800 serum samples collected from domiciled cats at animal hospitals in various areas of Japan. The overall prevalence was 6.0% (48/800). Among 48 positive individuals, there was no specific distribution of strength of antibody titers; the titers were 1:64 in 8 cats, 1:128 in 12, 1:256 in 8, 1:512 in 10, 1:1,024 in 8 and 1:2,048 in 2. The maximum prevalence was 15.4% in 13 cats at 17-23 yrs old group, whereas all were negative in 58 cats aged 12-16 yrs. The age groups in the order of higher prevalence were 8, 4, 10, 5, 3, and 7 yrs, showing no aging effect to the prevalence. In terms of rearing conditions of those cats, they were classified into 4 groups, i.e., indoor, free, outdoor, and others. The prevalence in the outdoor group (11.1%) was significantly higher (p < 0.05) than that in the free group (4.8%). Epidemiological aspects observed in the domiciled cats were different from those reported in the stray cats.     

Seroprevalence of Toxoplasma gondii and Trichinella spiralis in North Carolina black bears (Ursus americanus)

Serum samples from 143 hunter-killed black bears were collected during the 1996 and 1997 black bear hunting seasons in eastern North Carolina. All samples were tested for antibodies to Toxoplasma gondii by the modified agglutination test. Antibodies to T. gondii were present in 120 of 143 (84%) bears. Females had significantly higher titers than males (Wilcoxon rank sums test, P = 0.045), and titers increased with age (Jonckheere test, P = 0.01). Samples collected during 1996 (n = 79) were tested for antibodies to Trichinella spiralis by enzyme-linked immunosorbent assay. No samples were positive for antibodies to T. spiralis.     

Seroprevalence of Bartonella henselae and Toxoplasma gondii infections among pet cats in Kanagawa and Saitama Prefectures

Seroprevalence of Bartonella henselae and Toxoplasma gondii was investigated among 471 pet cats obtained from seven private animal hospitals in Kanagawa and Saitama Prefectures during the period from May 1994 to June 1995. 'Furthermore, 67 randomly selected from the 471 serum samples were examined for the feline immunodeficiency virus (FIV) antibody and feline leukemia virus (FeLV) antigen. The antibody to B. henselae was examined by an indirect immunofluorescent antibody test. T. gondii, FIV and FeLV infections in cats were detected with respective commercial kits. Of the cat serum samples tested, 43 (9.1%) were found to be seropositive for B. henselae and 41 (8.7%) for T. gondii. The B. henselae-positive rate (12.9%) of male cats was significantly higher than that (5.2%) of female cats. On the other hand, T. gondii-positive rate was 9.1% in male and 8.7% in female cats and there was no significant difference in the positivity between sexes. The positive rate in each hospital varied from 0 to 19.5% for B. henselae and 4.9 to 18.8% for T. gondii. The ages of B. henselae- and T. gondii-positive cats were distributed from < 1-year-old to 14-year-old and the seropositivity increased with age of cats. Of the 67 cat serum samples, 16 and 6 cases were positive for FIV and FeLV, respectively. There was no relationship between these viral and B. henselae infections in cats.     

Prevalence of Toxoplasma gondii antibodies in wild and domestic animals in northern California

Wild and domestic animals from 3 geographic-climatologic areas in northern California were tested for antibodies against Toxoplasma gondii. A total of 2,796 serum samples representing 37 species of wild mammals, 35 species of wild birds, and 5 species of domestic animals were tested by the indirect hemagglutination test. Of 1,174 wild mammal serums tested, 10.8% were positive, which compared with 14.7% of the 1,221 domestic mammal serums. Of 229 wild carnivores tested, 45% were seropositive, including 69% of 86 bobcats, 28% of 58 coyotes, 48% of 25 raccoons, 27% of 26 gray foxes, 22% of 32 striped skunks, a civet cat, and a mink. Serologic evidence of infection was found in 38% of 47 rural domestic cats, but none of the 7 dogs tested was seropositive. Of 160 murid rodents (rats and house mice) in rural habitats, 4% were seropositive, which compared with 2% of 399 cricetine rodents (mostly deer mice) collected from wilderness habitats. Seven percent of 56 wild Artiodactyla (deer and feral pigs) were seropositive, which compared with 15% of 1,048 domestic sheep tested. Of 401 birds tested, 3.5% had antibodies against T gondii. The highest prevalence of antibodies among birds was in crows (14%). Toxoplasma was isolated from 1 raven, by mouse inoculation. In general, the highest prevalence of seropositive carnivores, rodents, and sheep was in the coastal region below 100 ft elevation, where the weather is cool and damp for much of the year. In the central valley the highest prevalence among sheep was in areas under irrigation. The prevalence of antibodies was lowest in the mountain areas, where climatologic extremes prevail at various seasons of the year.     

Gut-derived intraepithelial lymphocytes induce long term immunity against Toxoplasma gondii

Intraepithelial lymphocytes (IEL) of the intestine represent an important barrier in the prevention of infection against orally acquired pathogens. Adoptive transfer of Ag-primed IEL into a naive host can protect against challenge. Using a murine model, we demonstrate in two genetically distinct mouse strains (C57BL/6 and CBA/J) that protective IEL can be isolated at specific times after oral infection with cysts containing bradyzoites. Adoptive transfer of IEL obtained from the intestine of infected mice at these specific times can provide long term protection, as determined by mortality and cyst number against challenge. The protective IEL appear to be CD8+, TCR-alpha/beta and are at least partially dependent upon the presence of TCR-gamma/delta T cells in the host. Endogenous production of the pivotal cytokine, IFN-gamma, is essential for host immunity. These findings demonstrate that gut-derived IEL represent a potentially important mechanism to provide long term immunity to the host.     

Macrophage function and host resistance against infection with Toxoplasma gondii

The role of macrophages on the course of an infection with Toxoplasma gondii has been examined. Stimulation of macrophage function by killed Bordetella pertussis cells did not show any beneficial effect as an increased susceptibility became apparent. The functional blockade of macrophages by dextran sulfate or carbon particles did not result in a higher susceptibility of mice to the lethal primary infection with T. gondii. Thus in vivo macrophages apparently do not play an essential role as effector cells as they do in infections with other obligate intracellular infective organisms such as Listeria monocytogenes. The spleen is apparently of crucial importance for resistance against T. gondii infection, since death occurred earlier in splenectomized mice than in control animals.     

Prevalence of Neospora caninum and Toxoplasma gondii antibodies in sera from camels from Egypt

Sera from camels from Egypt were examined by the direct agglutination tests incorporating mercaptoethanol for antibodies to Neospora caninum and Toxoplasma gondii. Antibodies to N. caninum were found in 6 of 161 camels in titers of 1:40 (2 camels) and 1:80, 1:160, 1:640, and 1:1280 in 1 camel each, using N. caninum formalin preserved whole tachyzoites as antigen. Antibodies to T. gondii were found in 17.4% of 166 camels in titers of 1:25 (3 camels), 1:50 (18 camels). and > 1:500 (8 camels) using T. gondii tachyzoites. All 6 camels with N. caninum antibodies had no T. gondii antibodies in 1:4 dilution of serum, indicating specificity of the reaction. This is the first report of N. caninum prevalence in Egypt.     

Detection of IgA antibodies as important markers of acute primary infection with Toxoplasma gondii

The diagnosis of Toxoplasma gondii infection is currently based on immunological tests, but tests for IgM and IgG antibodies alone are often insufficient to estimate the risk of active disease, especially during pregnancy and in immunodeficient patients. Classically the study of anti-toxoplasma immunity involves titration of IgG antibodies, which reflect immunity to the parasite, and IgM antibodies which of present, reveal acute infection. However, technical advances have shown the limitations of these tests as tests for IgM can be positive because of residual specific IgM or even in subjects free of acute infection due to the existence of natural interfering IgM. In addition, IgM can be absent in children with congenital toxoplasmosis or subjects with secondary reactivation. The purpose of our study was to evaluated of IgA antibodies to T. gondii in serum samples which were positive in screening test. Our results confirm the diagnostic value of testing for anti-toxoplasma IgA antibodies. These antibodies are absent in uninfected subjects and are detected rapidly after primary infection. The determination of IgA complements IgM determination for the diagnosis of toxoplasmosis.     

Heat shock proteins of Toxoplasma gondii

We have investigated heat shock protein (HSP) expression in mouse-virulent and -avirulent strains of Toxoplasma gondii by performing Western blot analysis using a monoclonal antibody against HSP65 of Mycobacterium bovis and a polyclonal antiserum against HSP70 of Plasmodium falciparum as primary antibodies. We initially observed that murine macrophages express HSP65 when infected with either virulent or avirulent strains, a result which contradicts previous reports. Differential HSP expression consistent which virulence was observed between strains, with high levels of a 70kDa HSP (HSP70) only detected in virulent strains in vivo. This protein was not observed in virulent strains in the immunocompromised mouse or in vitro, suggesting induction by immunological stress. This protein was only poorly expressed in avirulent strains. A 65kDa protein was observed in all strains in vivo and in vitro, suggesting a shared epitope with HSP70. These results are consistent with the hypothesis that the induced expression of HSP70 in virulent strains of T. gondii by immunological stresses may provide protection for these strains against cell damage associated with invasion of the host, allowing the virulent strains to persist as tachyzoites without the requirement for the encystation observed in avirulent strains.     

Seroprevalence of selected disease agents from free-ranging black bears in Florida

Streptococcus pneumoniae is a common cause of meningitis. Nitric oxide (NO) has been implicated in causing cerebral edema. Modulating NO production in cerebrospinal fluid (CSF) may have a role in the treatment of bacterial meningitis. Experimental S. pneumoniae meningitis was induced in a rabbit model to determine CSF parameters and NO concentrations. An electrochemical probe in the CSF throughout the 7-hour experiment monitored NO concentrations. The animals had S. pneumoniae (10(5)) injected intracisternally and incubated for 1 hour. Cerebrospinal fluid 200-300 microl was obtained by intracisternal puncture at zero, 2, 4, and 7 hours after drug administration to measure glucose, protein, and lactic acid by standard chemical methods. White blood cell count was measured by hemocytometry. Three groups of five animals were used-control (C), ceftriaxone (CTX), and ceftriaxone plus dexamethasone (CTX+D). Ceftriaxone concentrations in CSF were obtained by microdialysis and analyzed by high-performance liquid chromatography. Mean (+/- SEM) CSF white blood cell count was significantly higher at 2 hours in the C group than in the other two groups (C 7307 +/- 1302, CTX 605 +/- 345, CTX+D 730 +/- 43/mm3, p<0.002). Ceftriaxone induced a significant rise in protein at 4 hours compared with the other groups (C 364 +/- 107, CTX 1158 +/- 797, CTX+D 365 +/- 100 mg/dl, p<0.02). Cerebrospinal fluid lactic acid was significantly different at 4 and 7 hours between C and CTX+D groups (4-hr C 8.0 +/- 2.2, CTX+D 2.0 +/- 0.4 mmol/L, p<0.05; 7-hr C 10.2 +/- 2.4, CTX+D 2.8 +/- 0.8 mmol/L, p<0.01). Median NO concentrations were significantly elevated in the control group compared with the other two groups (C 11.7, CTX 6.8, CTX+D 6.5 micro, p<0.02 C vs CTX, p<0.01 C vs CTX+D). Average (+/- SEM) NO concentrations were significantly higher in the C group at 4 hours (18.1 +/- 0.4, CTX 5.8 +/- 1.8 microM, p<0.05; CTX+D 11.5 +/- 4.0 microM, p>0.05), whereas they did not rise significantly until 7 hours in the CTX group (CTX 18.7 +/- 0.7, C 8.9 +/- 0.4 microM, p=0.055; CTX+D 8.1 +/- 2.2 microM, p<0.05). These results indicate that ceftriaxone with or without dexamethasone significantly decreases lactic acid concentrations and white cell penetration into the CSF in an experimental model of S. pneumoniae meningitis. In addition, ceftriaxone induced a significant elevation in CSF protein. Median NO production in the CSF was significantly attenuated by ceftriaxone.     

Toxoplasma gondii infection in advanced HIV infection

OBJECTIVE: To study Toxoplasma encephalitis (TE) in advanced HIV infection, including predictive factors, possible prophylactic regimens and impact on survival. DESIGN: Epidemiological analysis of data collected prospectively during the Alpha study, a double-blind, randomized clinical trial, comparing two doses of dideoxyinosine in patients with advanced HIV disease. PATIENTS: First episode of TE occurred in 75 out of 499 patients participating in the trial. METHODS: Kaplan-Meier estimates and semi-parametric Cox's model were used. RESULTS: A low CD4 cell count and a positive Toxoplasma serology were strongly predictive of the occurrence of TE. In patients with CD4 counts < 100 x 10(6)/l and a positive Toxoplasma serology at entry to the study, the 12-month TE incidence was 25.4%. Patients who were receiving at entry any of the following potentially antitoxoplasmic drugs: trimethoprim-sulphamethoxazole, pyrimethamine, dapsone, pyrimethamine-sulphadoxine or sulphadiazine, had a lower TE incidence than those who were not; 6.2 versus 18.8%, respectively (P < 0.001). The rate of survival 12 months after TE was 29.6%. Even after adjusting the major prognostic covariates, TE was predictive of death (P < 0.001; relative risk, 1.8). CONCLUSIONS: The high HIV incidence, morbidity and mortality in high-prevalence areas suggests that primary prophylaxis should be given in patients at high risk for toxoplasmic reactivation.     

Prevalence of Toxoplasma gondii in Canadian market-age pigs

Triacylglycerol lipase (L3) was purified from Aspergillus oryzae RIB128 by ammonium sulfate fractionation, acetone precipitation, anion-exchange chromatography, and gel filtration. The purified enzyme was formed from a glycoprotein and a monomeric protein with molecular masses of 25 and 29 kDa, by SDS-PAGE and gel filtration, respectively. The optimum pH at 40 degrees C was 5.5 and the optimum temperature at pH 5.5 was 40 degrees C. The enzyme was stable between a pH range of 4.0-7.5 at 30 degrees C for 24 h, and at up to 30 degrees C at pH 5.5 for 1 h. Heavy metal ions, detergents, DFP, and DEP strongly inhibited the enzyme activity. The lipase hydrolyzed not only triacylglycerols but also monoacylglycerols and diacylglycerols. The enzyme had higher specificity toward triacylglycerols of middle-chain saturated fatty acids than short-chain or long-chain fatty acids. The enzyme had 1,3-positional specificity. The N-terminal amino acid sequence of the enzyme was not significantly similar to that of other lipases with published sequences.     

IL-15 augments CD8+ T cell-mediated immunity against Toxoplasma gondii infection in mice

Cytokines of the Th1 profile are important mediators of protective host immunity against Toxoplasma gondii infection in mice. In this study we describe the effect of the recently identified cytokine, IL-15, on prevention of murine infection with T. gondii. Administration of exogenous rIL-15 with soluble Toxoplasma lysate Ag (TLA) provides complete protection against a lethal parasite challenge, whereas treatment with either rIL-15 or TLA alone is not protective. Following immunization with TLA/rIL-15, there is a significant proliferation of splenocytes expressing the CD8+ phenotype in response to TLA. A significant rise in the level of serum IFN gamma was observed in vaccinated mice. Adoptive transfer of CD8+ T cells, but not CD4+ T cells, from TLA/rIL-15-vaccinated mice protects naive mice from a lethal parasite challenge. These CD8+ T cells exhibit enhanced CTL activity against target macrophages infected with T. gondii. Mice that have been immunized are protected against lethal parasite challenge for at least 1 mo postvaccination. These observations demonstrate that TLA when administered with exogenous rIL-15 generates toxoplasmacidal Ag-specific CD8+ T cells. These T cells proliferate upon exposure to parasite Ag, exhibit long term memory CTL against infected target cells, and may be involved in host immune memory to this parasite.     

Differential study of two strains of Toxoplasma gondii

This study aimed to differentiate between the virulent and avirulent strains of T. gondii by studying morphometric measurement using C.I.A.S., determination of the relative DNA content and extract, SDS poly acrylamide gel electrophoresis and isoenzyme on cellulose acetate gel. Identifying these differences may be useful in studying different disease types and in pathogenic mechanisms. Besides, the presence of common proteins between them may be of value for diagnostic purposes and for formulation of vaccines.     

Genotypic analysis of Toxoplasma gondii isolates from pigs

To determine the prevalence of the 3 primary clonal lineages of Toxoplasma gondii (strain types I, II, and III) in a potential food source of infection for humans, we analyzed 43 isolates of T. gondii that had been collected from pigs at an abattoir in Iowa. Parasites were harvested as in vitro-grown tachyzoites, and their genotypes were determined at the SAG1 and SAG2 loci. On the basis of the allele identified at the SAG2 locus, isolates were grouped into 1 of the 3 primary lineages. Type II strains were by far the most prevalent, accounting for 83.7% of the isolates. The type III genotype was identified in only 16.3% of the isolates. These prevalences differ significantly from a previous sampling of isolates from animals but are similar to the frequencies with which they occur in human disease cases. Similar to the previously characterized strain P89, strains P62 and P105 appeared to have recombinant genotypes. The type I genotype was not identified in the isolates from pigs although these strains have previously been shown to account for approximately 10-25% of toxoplasmosis cases in humans.     

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.     

Mechanisms of innate resistance to Toxoplasma gondii infection

The interaction of protozoan parasites with innate host defences is critical in determining the character of the subsequent infection. The initial steps in the encounter of Toxoplasma gondii with the vertebrate immune system provide a striking example of this important aspect of the host-parasite relationship. In immuno-competent individuals this intracellular protozoan produces an asymptomatic chronic infection as part of its strategy for transmission. Nevertheless, T. gondii is inherently a highly virulent pathogen. The rapid induction by the parasite of a potent cell-mediated immune response that both limits its growth and drives conversion to a dormant cyst stage explains this apparent paradox. Studies with gene-deficient mice have demonstrated the interleukin-12 (IL-12)-dependent production of interferon gamma (IFN-gamma) to be of paramount importance in controlling early parasite growth. However, this seems to be independent of nitric oxide production as mice deficient in inducible nitric oxide synthase (iNOS) and tumour necrosis factor receptor were able to control early growth of T. gondii, although, they later succumbed to infection. Nitric oxide does, however, seem to be important in controlling persistent infection; treating chronic infection with iNOS metabolic inhibitors results in disease reactivation. Preliminary evidence implicates neutrophils in effector pathways against this parasite distinct from that described for macrophages. Once initiated, IL-12-dependent IFN-gamma production in synergy with other proinflammatory cytokines can positively feed back on itself to induce 'cytokine shock'. Regulatory cytokines, particularly IL-10, are essential to down-regulate inflammation and limit host pathology.     

Detection by enzyme immunosorbent assay of Toxoplasma gondii IgG antibodies in dried blood spots on PKU-filter paper from newborns

OBJECTIVE: To assess the relative efficacy of a pacing esophageal stethoscope and intermittent boluses (40 mg) of gallamine in correcting sinus bradycardia (SB) during coronary artery surgery. DESIGN: The study was prospective, randomized, and controlled. SETTING: A community hospital. PARTICIPANTS: Fifty patients scheduled for elective coronary artery surgery. INTERVENTIONS: The patients were randomly allocated to receive treatment for an SB (less than 60 BPM) with either transesophageal atrial pacing (TAP) or gallamine. MEASUREMENTS AND MAIN RESULTS: Heart rate, blood pressure, and systemic hemodynamics were measured. The electrocardiogram was monitored for rate, rhythm, and conduction abnormalities. Twenty-four of the 25 TAP patients could be paced at a rate of 70 BPM after SB. Cardiac index increased from 1.90 to 2.56 L/min/m2. In the gallamine group, heart rate was increased from 50 to 66 BPM, but cardiac index only increased to 2.2 L/min/m2, and 2 patients developed nodal rhythms. Eight of these patients had peak heart rates over 80 BPM, and two were over 90 BPM. CONCLUSIONS: The ability to reliably and precisely control heart rate was superior with TAP compared with intermittent bolus dosing with gallamine.