Prevalence of Toxoplasma gondii Infection in Household Cats in Korea and Risk Factors

Several epidemiological surveys have reported the prevalence of Toxoplasma gondii infection in stray cats in Korea, but little information is available on T. gondii infection in household cats. The aim of the present study was to assess the prevalence and risk factors of T. gondii infection among household cats reared in Seoul, Korea. A total of 474 blood samples were collected from clinically healthy household cats. All samples were tested using ELISA and PCR. The risk factor analysis was based on a questionnaire filled out by the owners. The overall positive rate for ELISA and PCR assays was 2.2% (10/437) and 2.1% (10/474), respectively. With regard to the origin of cats, the positive rates among cats adopted from the animal shelter and veterinary clinic for stray cats were significantly different (P<0.05). Our study demonstrated that the positive rate of T. gondii infection in household cats was low and that this low prevalence was assumed to be associated with keeping the cats indoors and restriction of eating raw food and uncooked meat. Therefore, we suggest that the owners check the origin of the cats prior to adoption to prevent infection of other animals, including humans.     

IgG Avidity Antibodies against Toxoplasma gondii in High Risk Females of Reproductive Age Group in India

Toxoplasma gondii is an obligate intracellular protozoan that is distributed worldwide. Recently, several tests for avidity of Toxoplasma IgG antibodies have been introduced to help discriminate between recently acquired and distant infections. The study was conducted in Jawaharlal Nehru Medical College and Hospital, India from February 2011 to September 2012. Serum specimens were subjected to Toxoplasma IgM ELISA and IgG avidity ELISA test. Out of 48 patients with abortions, 17 (35.4%) were positive for IgM ELISA, and 8 (16.6%) had low IgG avidity antibodies. Out of 48 patients with other obstetric problems, 23 (47.9%) were positive for IgM ELISA, and 17 (35.4%) had low IgG avidity antibodies. Combining both groups on avidity test, only 25 of 40 (62.5%) IgM-positive women had low-avidity IgG antibodies suggesting a recent T. gondii infection in these women. More importantly, 15 (37.5%) of the IgM-positive women had high-avidity antibodies suggesting that the infection was acquired before gestation The relation of IgM seropositivity with the following risk factors was not found to be statistically significant; contact with cats (0.13), non-vegetarian food habits (0.05), and low socio-economic status (0.49). While, for IgG avidity ELISA, only contact with cats (0.01) was significantly associated with seropositivity. All other risk factors have P-values of >0.05 (not significant). IgG avidity test when used in combination with IgM test was a valuable assay for diagnosis of ongoing or recently acquired T. gondii infection in India.     

宠物弓形虫的感染及其防控

弓形虫病是一种世界性分布的人兽共患寄生虫病,对人类,尤其是妇女、儿童危害很大,估计全世界有1/3人受到该病的威胁。孕妇感染弓形虫后导致早产、流产、胎儿发育畸形;弓形虫是免疫功能低下患者的主要死亡原因之一。犬、猫是弓形虫的中间宿主和终末宿主,是人类感染弓形虫的主要来源。随着我国经济的迅速发展和人民生活水平的不断提高,城市中饲养犬、猫作为宠物的人越来越多,人、宠物间的亲密接触增加了弓形虫病传播给人的机会。加强对宠物犬、猫弓形虫病的研究及防控势在必行。本文就弓形虫的危害、宠物犬猫弓形虫感染及其防控措施作以综述。     

Infection of the athymic rat by Toxoplasma gondii

In contrast to normal rats which are resistant to T. gondii infection (10(7) tachyzo?tes), athymic rats did not survive an intraperitoneal infection with 10(3) toxoplasma. When nude rats were injected intravenously with lymph node cells from hirsute littermates, they became resistant in a dose-dependent manner to the infection. In addition, reconstituted athymic rats having survived for more than 4 months the first infection were also protected against a second challenge with 10(5) tachyzo?tes. Anti-T. gondii antibody levels detected in reconstituted athymic rats were related to protection. These preliminary findings suggest that T-dependent immunity is essential in the development of effector mechanisms involving antibodies in resistance to toxoplasmosis.     

Evidence for Heterotrimeric GTP-Binding Proteins in Toxoplasma gondii

Toxoplasma gondii , an intracellular protozoan parasite, resides within a host-derived vacuole that is rapidly modified by a parasite-secreted membranous tubular network. In this study we investigated the involvement of heterotrimeric G proteins in the secretory pathway of T. gondii. Aluminum fluoride (AIF_n), a specific activator of heterotrimeric G proteins, induced secretion from isolated tachyzoites of T. gondii in vitro, as seen by light optics and electron microscopy. In Western blot analyses, antibodies to G protein α subunits reacted with 39–42 kDa proteins from T. gondii isolates. Antibodies to G_oα and G_sα coupled to the fluorescent probe fluorescein isothiocyanate localized to the paranuclear region of T. gondii. G_i3α immunoprobes were confined to the cytoplasmic matrix of T. gondii and also labeled the parasitophorous vesicle. Fluorescein isothiocyanate-conjugated GA/1, an antipeptide antisera directed toward the GTP binding site common to G protein α subunits, was confined to the lateral cytoplasmic domain of the parasites where secretion is most prominent. In time-sequence studies using the GA/1 probe, the immunoreactive material shifted position daring invasion of target cell to areas of active secretion.     

Evidence for de novo sphingolipid biosynthesis in Toxoplasma gondii

Glycolipids are important components of cellular membranes involved in various biological functions. In this report, we describe the identification of the de novo synthesis of glycosphingolipids by Toxoplasma gondii tachyzoites. Parasite-specific glycolipids were identified by metabolic labelling of parasites with tritiated serine and galactose. These glycolipids were characterised as sphingolipids based on the labelling protocol and their insensitivity towards alkaline treatment. Synthesis of parasite glycosphingolipids were inhibited by threo-phenyl-2-palmitoylamino-3-morpholino-1-propanol and L-cycloserine, two well-established inhibitors of de novo sphingolipid biosynthesis. The identified glycolipids were insensitive towards treatment with endoglycoceramidase II indicating that they might belong to globo-type glycosphingolipids. Taken together, we provide evidence for the first time that T. gondii is capable of synthesising glycosphingolipids de novo.     

Long-Term Study of Toxoplasma gondii Infection in a Swedish Sheep Flock

The infection rate of Toxoplasma gondii was studied during 6 years in a sheep flock in central Sweden. The flock consisted of 165-249 breeding ewes of which 20-35% were lambs less than 1 year old. Most ewes were slaughtered when 5 years old. The sheep were kept indoors from end of September to early May. Lambing took place in March and April. Individual serum samples were collected twice a year, once just before turning the sheep out to pasture in the spring, and again after housing in the autumn. Sera were analysed by ELISA for antibodies to T. gondii. The seroprevalence varied between 10% and 45% during the 6 years of observation. Seroconversion was detected predominantly at the autumn sampling, indicating that in most cases infection was acquired at pasture. Subclinical effects of T. gondii infection on lamb weight, litter size, total litter weight and ewe weight were also studied. Lambs born to chronically infected ewes were lighter at birth than those of uninfected ewes, but this disparity was no longer evident at weaning.     

Seroepidemiology of Toxoplasma gondii Infection among Healthy Blood Donors in Taiwan

Toxoplasma gondii is an opportunistic, zoonotic pathogen with a worldwide distribution. There are large variations in the seroprevalence of T. gondii infection in different regions of the world. Although toxoplasmosis became a notifiable communicable disease in Taiwan in 2007, little is known about its epidemiology among the general population. This cross-sectional study aimed to survey the seroprevalence of T. gondii infection and its risk factors among healthy blood donors in Taiwan. Through collaborating with the Taiwan Blood Services Foundation, a total of 1,783 healthy blood donors from all six-branch blood service centers participated in this study. The blood samples were tested for the presence of T. gondii antibodies and DNA using enzyme immunoassays and real-time PCR, respectively. Structured questionnaires were used to gather information on risk factors for T. gondii infection. Of the 1,783 participants, 166 (9.3%) tested positive for anti-Toxoplasma IgG, while 5 (0.28%) tested positive for anti-Toxoplasma IgM. The five IgM positive donors had high avidity antibodies suggestive of past infection. No active parasitemia was detected by real-time PCR assays. Multivariate logistic regression showed that undercooked pork meat consumption (adjusted odds ratio [OR] = 2.9; 95% confidence interval [CI]: 1.3–6.5), raw mussels consumption (adjusted OR = 5.3; 95% CI: 1.5–19.1), having a cat in the household (adjusted OR = 2.0; 95% CI: 1.2–3.2), a lower education level (adjusted OR = 1.6; 95% CI: 1.1–2.3), and donation place in eastern Taiwan (adjusted OR = 2.5; 95% CI: 1.6–3.9) were independent risk factors for Toxoplasma seropositivity. These findings provide information on the seroprevalence and epidemiology of T. gondii infection among healthy blood donors in Taiwan.     

Association between Toxoplasma gondii infection and metabolic syndrome in obese adolescents: A possible immune-metabolic link

BackgroundToxoplasmosis as a global disease is considered as a triggering factor responsible for development of several clinical diseases. However, Toxoplasma gondii (T. gondii) is an understudied parasite of potential interest in obesity research. The current study aimed to explore the role of latent T. gondii infection in the pathogenesis of metabolic syndrome (MetS) in obese adolescents through studying the relationship between serum interferon-gamma [IFN-γ] and serum chemerin in context of MetS components.MethodsEighty-three obese adolescents were serologically screened for T. gondii-IgG antibodies and compared to 35 age-matched healthy T. gondii-seronegative controls. Participants were evaluated for anthropometric measurements, total-fat mass [FM], trunk-FM, serum lipid profile, IFN-γ, and chemerin levels. Homeostatic Model Assessment of insulin resistance (HOMA-IR) was calculated.ResultsThe prevalence of MetS was significantly higher within obese T. gondii-seropositive group compared to obese T. gondii-seronegative group (P = 0.033). Seropositive obese MetS group displayed significantly higher trunk-FM, HOMA-IR, chemerin, and IFN-γ compared to seronegative obese MetS group. Serum chemerin and IFN-γ were strongly correlated (P < 0.001) and were positively correlated with BMI, WC, total-FM, trunk-FM, HOMA-IR, cholesterol, triglycerides and negatively correlated with HDLC. HOMA-IR was a common predictor for serum chemerin (P = 0.030) and IFN-γ (P < 0.001).ConclusionsThe study results suggest that T. gondii infection may exert an immune-metabolic effect that may have a potential role in the development of MetS among obese adolescents.     

CCR5 Controls Immune and Metabolic Functions during Toxoplasma gondii Infection

CCR5, an important receptor related to cell recruitment and inflammation, is expressed during experimental Toxoplasma gondii infection. However, its role in the immunopathology of toxoplasmosis is not clearly defined yet. Thus, we inoculated WT and CCR5^-/- mice with a sub lethal dose of the parasite by oral route. CCR5^-/- mice were extremely susceptible to infection, presenting higher parasite load and lower tissue expression of IL-12p40, IFN-γ, TNF, IL-6, iNOS, Foxp3, T-bet, GATA-3 and PPARα. Although both groups presented inflammation in the liver with prominent neutrophil infiltration, CCR5^-/- mice had extensive tissue damage with hepatocyte vacuolization, steatosis, elevated serum triglycerides and transaminases. PPARα agonist Gemfibrozil improved the vacuolization but did not rescue CCR5^-/- infected mice from high serum triglycerides levels and enhanced mortality. We also found intense inflammation in the ileum of CCR5^-/- infected mice, with epithelial ulceration, augmented CD4 and decreased frequency of NK cells in the gut lamina propria. Most interestingly, these findings were accompanied by an outstanding accumulation of neutrophils in the ileum, which seemed to be involved in the gut immunopathology, once the depletion of these cells was accompanied by reduced local damage. Altogether, these data demonstrated that CCR5 is essential to the control of T. gondii infection and to maintain the metabolic, hepatic and intestinal integrity. These findings add novel information on the disease pathogenesis and may be relevant for directing future approaches to the treatment of multi-deregulated diseases.     

Developmental differentiation between tachyzoites and bradyzoites of Toxoplasma gondii

An important event in the pathogenesis of toxoplasmosis is the interconversion between the bradyzoite and the tachyzoite stage of Toxoplasma gondii within the intermediate host. The factors that influence either cyst formation (bradyzoites) or reactivation (tachyzoites) are unknown. Uwe Gross, Wolfgang Bohne, Martine Soête and Jean Fran?ois Dubremetz here describe current knowledge about the mechanisms that might lead to the induction of stage differentiation of this protozoan parasite.     

Antigenic differences between endozoites and cystozoites of Toxoplasma gondii

Antigenic differences between the cystozoite and endozoite of Toxoplasma gondii were found using fluorescent antibody staining. Antisera against the cystozoite reacted against only the cystozoite, whereas antisera against the endozoite reacted against both endozoite and cystozoite. Absorption of sera with endozoites removed only positive reactions with endozoites. These findings are the first to suggest antigenic differences between these two forms of Toxoplasma.     

Toxoplasma gondii Migration within and Infection of Human Retina

Toxoplasmic retinochoroiditis is a common blinding retinal infection caused by the parasite, Toxoplasma gondii. Basic processes relating to establishment of infection in the human eye by T. gondii tachyzoites have not been investigated. To evaluate the ability of tachyzoites to navigate the human retina, we developed an ex vivo assay, in which a suspension containing 1.5×10⁷ parasites replaced vitreous in a posterior eyecup. After 8 hours, the retina was formalin-fixed and paraffin-embedded, and sections were immunostained to identify tachyzoites. To determine the preference of tachyzoites for human retinal neuronal versus glial populations, we infected dissociated retinal cultures, subsequently characterized by neuron-specific enolase or glial fibrillary acidic protein expression, and retinal cell lines, with YFP-expressing tachyzoites. In migration assays, retinas contained 110–250 live tachyzoites; 64.5–95.2% (mean  = 79.6%) were localized to the nerve fiber layer, but some were detected in the outer retina. Epifluorescence imaging of dissociated retinal cultures 24 hours after infection indicated preferential infection of glia. This observation was confirmed in growth assays, with significantly higher (p≤0.005) numbers of tachyzoites measured in glial verus neuronal cell lines. Our translational studies indicate that, after entering retina, tachyzoites may navigate multiple tissue layers. Tachyzoites preferentially infect glial cells, which exist throughout the retina. These properties may contribute to the success of T. gondii as a human pathogen.