Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention

Towards a Preventive Strategy for Toxoplasmosis: Current Trends, Challenges, and Future Perspectives for Vaccine Development

With its facultative ability to induce various types of infection in its hosts, Toxoplasma gondii remains a fascinating and enigmatic pathogen. As a parasite, despite its primitive unicellular structure, it possesses a highly sophisticated arsenal of invasive and defensive tools. Toxoplasmosis has gained widespread significance as a zoonotic disease capable of inducing severe illnesses in humans and drastic economic losses in the veterinary field. Although around a third of the world's population is infected with Toxoplasma gondii, immunocompromised people, pregnant women, and neonates are more vulnerable to the most severe forms of the disease. Hence, development of a preventive strategy is urgently needed to combat T. gondii infection in both humans and animals. Successful triggering of host immune responses and development of specific immune responses against the different strains and antigens of T. gondii has encouraged researchers to focus on vaccination as a feasible preventive control strategy against toxoplasmosis. In the last few years, vaccine development against T. gondii infections has seen great advances and achievements being made at the research level and, to a lesser extent, in veterinary applications. Currently, only one live attenuated vaccine is available for reducing abortions and fetal losses in pregnant ewes. Otherwise, researchers have investigated numerous classes of vaccine, including live attenuated, recombinant subunit, and vectored. In this chapter we discuss the most commonly investigated vaccines against toxoplasmosis, recombinant DNA and protein vaccines, with special focus on their methodologies and mechanisms of action.

Co-administration of interleukins 7 and 15 with DNA vaccine improves protective immunity against Toxoplasma gondii

Toxoplasma gondii is an obligatory intracellular parasite, which can infect all warm-blooded animals including humans. Cytokines, including IL-15 and IL-7, play a critical role in the regulation of the homeostasis of naive and memory T cells. Co-administration the DNA vaccine with cytokines may improve its efficacy. IL-7 and IL-15 from splenic tissues of Kunming mice were cloned, and eukaryotic plasmid pVAX-IL-7-IL-15 was constructed. Kunming mice were administrated with DNA vaccine expressing T. gondii calcium-dependent protein kinase 1 (TgCDPK1), pVAX-CDPK1, in the presence or absence of IL-7 and IL-15 plasmids (pVAX-IL-7-IL-15), immune responses were analyzed including lymphoproliferative assay, cytokine and serum antibody measurements, flow cytometric surface markers on lymphocytes, and thus protective immunity against acute and chronic T. gondii infection was estimated. Mice injected with pVAX-CDPK1 supplemented with pVAX-IL-7-IL-15 showed higher Toxoplasma-specific IgG2a titers, Th1 responses associated with the production of IFN-γ, IL-2 as well as cell-mediated cytotoxic activity where stronger frequencies of IFN-γ secreting CD8+ and CD4+ T cells (CD8+/CD4+ IFN-γ+ T cells) compared to controls. Co-administration of pVAX-IL-7-IL-15 and pVAX-CDPK1 significantly (P < 0.05) increased survival time (18.07 ± 5.43 days) compared with pVAX-CDPK1 (14.13 ± 3.85 days) or pVAX-IL-7-IL-15 (11.73 ± 1.83 days) alone, and pVAX-IL-7-IL-15 + pVAX-CDPK1 significantly reduced the number of brain cysts (73.5%) in contrast to pVAX-CDPK1 (46.0%) or pVAX-IL-7-IL-15 alone (45.0%). Our results indicate that supplementation of DNA vaccine with IL-7 and IL-15 would facilitate specific humoral and cellular immune responses elicited by DNA vaccine against acute and chronic T. gondii infection in mice.

Major Parasitic Zoonoses Associated with Dogs and Cats in Europe

Some of the most important zoonotic infectious diseases are associated with parasites transmitted from companion animals to man. This review describes the main parasitic zoonoses in Europe related to dogs and cats, with particular emphasis on their current epidemiology. Toxoplasmosis, leishmaniosis, giardiosis, echinococcosis, dirofilariosis and toxocariosis are described from the animal, as well as from the human host perspectives, with an emphasis on parasite life cycle, transmission, pathogenicity, prevention and identification of knowledge gaps. In addition, priorities for research and intervention in order to decrease the risks and burden of these diseases are presented. Preventing zoonotic parasitic infections requires an integrated multidisciplinary 'One Health' approach involving collaboration between veterinary and medical scientists, policy makers and public health officials.

Toxoplasma gondii seroprevalence in pet cats in Norway and risk factors for seropositivity

OBJECTIVES

The aims of the study were to estimate Toxoplasma gondii seroprevalence in pet cats in Norway and to evaluate risk factors for seropositivity. Additionally, serum biochemistry and haematological variables for T gondii seropositive and seronegative cats were compared.

METHODS

A convenience sample of surplus sera submitted to the Central Laboratory, Norwegian University of Life Sciences, was collected. The samples were from healthy cats and cats with a variety of diseases. Analyses for IgG antibodies to T gondii were performed with a commercial direct agglutination test, with 1:40 as the threshold value. For risk factor analysis a logistic regression model of the relationship between predictors and the outcome was applied.

RESULTS

One hundred and ninety-six of 478 cats were seropositive for T gondii, and the estimated seroprevalence in the study sample was 41.0% (95% confidence interval 36.6-45.4). Compared with domestic cats, pedigree cats had reduced risk for Toxoplasma seropositivity (odds ratio [OR] 0.42). Males had increased risk (OR 1.63) compared with females. The effect of age was highly significant, and an increase in the cats' age across the interquartile range (IQR; 52-160 months/4-13 years of age) doubled the risk of Toxoplasma seropositivity (OR 2.11). The risk for Toxoplasma seropositivity among cats living in Oslo was significantly reduced (OR 0.51) when compared with the rest of Norway.

CONCLUSIONS AND RELEVANCE

Pet cats in Norway appear to be commonly exposed to T gondii. Signalment and geographical region influenced the odds of Toxoplasma seropositivity, whereas health status did not.

DNA vaccination with genes encoding Toxoplasma gondii antigens ROP5 and GRA15 induces protective immunity against toxoplasmosis in Kunming mice

OBJECTIVES

To evaluate the protective efficacy of a DNA vaccine encoding Toxoplasma gondii rhoptry protein 5 (ROP5) and GRA15 antigens.

METHODS

We constructed eukaryotic plasmids expressing pVAX-ROP5 and pVAX-GRA15, and measured the immune responses to these DNA vaccines.

RESULTS

Kunming mice immunized with pVAX-ROP5 or pVAX-GRA15 showed significantly increased serum IgG2a titers; Th1 responses association with the production of IFN-γ, IL-2, IL12 p40 and IL-12 p70; cell-mediated cytotoxic activity with increased frequencies of IFN-γ secreting CD8(+) T cells (CD8(+) IFN-γ+ T cells), as well as prolonged survival time (19.4 ± 4.9 days for ROP5; 17.8 ± 3.8 days for GRA15) and brain cyst reduction (57.4% for ROP5; 65.9% for GRA15) compared to control mice. Co-administration with pVAX-ROP5 and pVAX-GRA15 boosted the cellular and humoral immune responses, and significantly increased cyst reduction (79%) and prolonged the survival of immunized mice (22.7 ± 7.2 days).

CONCLUSION

Co-immunization of pVAX-ROP5 and pVAX-GRA15 increase the protective efficacy.

Causes of endogenous uveitis in cats presented to referral clinics in North Carolina

OBJECTIVE

To investigate the causes of endogenous uveitis in cats presenting to referral ophthalmology clinics in North Carolina.

PROCEDURE

Medical records of cats diagnosed with endogenous uveitis at North Carolina State University's College of Veterinary Medicine (NCSU-CVM) or Animal Eye Care Associates of Cary, NC between 2003 and 2015 were reviewed. Inclusion criteria were cats that had complete diagnostic workups, including clinical, clinicopathological, serological, and histopathological data, as well as imaging modalities. Serology was consistently completed for feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), feline coronavirus (FCoV), Toxoplasma gondii, and Bartonella spp.

RESULTS

One hundred and twenty cats met the inclusion criteria. Seroprevalence of FeLV (2.7%), FIV (7.3%), FCoV (34.7%), T. gondii (23.7%), and Bartonella spp. (43.2%) was observed, with a combined seroprevalence of 59.2%. Nineteen cats (15.8%) were diagnosed with feline infectious peritonitis (FIP) based on clinical, hematological, serological, histopathological, and necropsy findings. The average age of all cases was 7.62 years, while the average age of cats diagnosed with FIP was 1.82 years. Neoplasia was diagnosed in six cats (5.0%). No underlying etiology was found in 49 cats (40.8%).

CONCLUSIONS

Both idiopathic and neoplastic causes of uveitis were less prevalent than previously reported in studies, while seropositivity was higher than previously reported for the study area. This may be due to improved diagnostic capabilities or that cats with infectious disease were more likely to be referred. Because of the high prevalence of FIP, young cats with uveitis should be evaluated for hyperglobulinemia and FCoV serology should be performed as minimal diagnostics.

Prevalence of toxoplasmosis in pregnant women and vertical transmission of Toxoplasma gondii in patients from basic units of health from Gurupi, Tocantins, Brazil, from 2012 to 2014

Introduction

Toxoplasmosis is a parasitary disease that presents high rates of gestational and congenital infection worldwide being therefore considered a public health problem and a neglected disease.

Objective

To determine the prevalence of toxoplasmosis amongst pregnant women and vertical transmission of Toxoplasma gondii in their newborns attended in the Basic Units of Health (BUH) from the city of Gurupi, state of Tocantins, Brazil.

Methods

A prevalence study was performed, including 487 pregnant women and their newborns attended in the BUH of the urban zone of the city of Gurupi, state of Tocantins, Brazil, during the period from February 2012 to February 2014. The selection of the pregnant women occurred by convenience. In the antenatal admission they were invited to participate in this study. Three samples of peripheral blood were collected for the detection of specific anti-T. gondii IgG, IgM and IgA through ELISA, for the polimerase chain reaction (PCR) and IgG avidity during pregnancy. When IgM antibodies were detected the fetal and newborn infection investigation took place. The newborn was investigated right after birth and after one year of age through serology and PCR to confirm/exclude the vertical transmission. The analyses were performed in the Studies of the Host-Parasite Relationship Laboratory (LAERPH, IPTSP-UFG), Goiania, state of Goias, Brazil. The results were inserted in a data bank in Epi-Info 3.3.2 statistic software in which the analysis was performed with p≤5%.

Results

The toxoplasmosis infection was detected in 68.37% (333/487, CI95%: 64.62–72.86). The toxoplasmosis chronic infection prevalence was of 63.03% (307/487, CI95%: 58.74–67.32). The prevalence of maternal acute infection was of 5.33% (26/487; CI95%: 3.3–7.3) suspected by IgM antibodies detection in the peripheral blood. The prevalence of confirmed vertical transmission was of 28% (7/25; CI95%: 10.4–45.6).

Conclusions

These results show an elevated prevalence of toxoplasmosis in pregnant women and vertical transmission of T. gondii in the city of Gurupi, state of Tocantins, Brazil.

The prevalence of antibodies to Toxoplasma gondii in sheep in the Western Cape, South Africa

The seroprevalence of Toxoplasma gondii antibodies in a sample of 292 merino sheep farmed in a semi-intensive manner in the Overberg region of the Western Cape, South Africa, was investigated. Antibody seroprevalence was determined by enzyme-linked immunosorbent assay. Of the total sample, 23 sheep tested positive for T. gondii antibodies (8%; 95% CI: 4.7688-10.9846). There was no statistically significant relationship between seroprevalence and age of the sheep. The highest seroprevalence was found in sheep between 28 and 40 months old; a total of 19 sheep were seropositive by 40 months. No seropositive sheep were found in the age group between 16 and 28 months. The seroprevalence reported in this study is higher than what has previously been reported for the Western Cape (6%) and across South Africa on average (4.7%). As sheep farming is economically significant in South Africa, the presence of T. gondii amongst sheep may pose a production threat to the small-stock industry as well as to public health and food security. We therefore recommend further surveillance to identify high-risk animal populations so that local control measures can be put in place.

Fatal Toxoplasma gondii infection in the giant panda

Toxoplasma gondii can infect nearly all warm-blooded animals. We report an acute fatal T. gondii infection in the endangered giant panda (Ailuropoda melanoleuca) in a zoo in China, characterized by acute gastroenteritis and respiratory symptoms. T. gondii infection was confirmed by immunological and molecular methods. Multilocus nested PCR-RFLP revealed clonal type I at the SAG1 and c29-2 loci, clonal type II at the SAG2, BTUB, GRA6, c22-8, and L358 loci, and clonal type III at the alternative SAG2 and SAG3 loci, thus, a potential new genotype of T. gondii in the giant panda. Other possible pathogens were not detected. To our knowledge, this is the first report of clinical toxoplasmosis in a giant panda.

Improved orthologous databases to ease protozoan targets inference

Background

Homology inference helps on identifying similarities, as well as differences among organisms, which provides a better insight on how closely related one might be to another. In addition, comparative genomics pipelines are widely adopted tools designed using different bioinformatics applications and algorithms. In this article, we propose a methodology to build improved orthologous databases with the potential to aid on protozoan target identification, one of the many tasks which benefit from comparative genomics tools.

Methods

Our analyses are based on OrthoSearch, a comparative genomics pipeline originally designed to infer orthologs through protein-profile comparison, supported by an HMM, reciprocal best hits based approach. Our methodology allows OrthoSearch to confront two orthologous databases and to generate an improved new one. Such can be later used to infer potential protozoan targets through a similarity analysis against the human genome.

Results

The protein sequences of Cryptosporidium hominis, Entamoeba histolytica and Leishmania infantum genomes were comparatively analyzed against three orthologous databases: (i) EggNOG KOG, (ii) ProtozoaDB and (iii) Kegg Orthology (KO). That allowed us to create two new orthologous databases, “KO + EggNOG KOG” and “KO + EggNOG KOG + ProtozoaDB”, with 16,938 and 27,701 orthologous groups, respectively.

Such new orthologous databases were used for a regular OrthoSearch run. By confronting “KO + EggNOG KOG” and “KO + EggNOG KOG + ProtozoaDB” databases and protozoan species we were able to detect the following total of orthologous groups and coverage (relation between the inferred orthologous groups and the species total number of proteins): Cryptosporidium hominis: 1,821 (11 %) and 3,254 (12 %); Entamoeba histolytica: 2,245 (13 %) and 5,305 (19 %); Leishmania infantum: 2,702 (16 %) and 4,760 (17 %).

Using our HMM-based methodology and the largest created orthologous database, it was possible to infer 13 orthologous groups which represent potential protozoan targets; these were found because of our distant homology approach.

We also provide the number of species-specific, pair-to-pair and core groups from such analyses, depicted in Venn diagrams.

Conclusions

The orthologous databases generated by our HMM-based methodology provide a broader dataset, with larger amounts of orthologous groups when compared to the original databases used as input. Those may be used for several homology inference analyses, annotation tasks and protozoan targets identification.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1090-0) contains supplementary material, which is available to authorized users.

Seroprevalence of and Risk Factors for Toxoplasma gondii Infection in Cats in Estonia

In Estonia, northeastern Europe, Toxoplasma gondii seroprevalence in humans has not declined, in contrast to many other countries. The reasons for this are unknown. Domestic cats are important hosts in the epidemiology of the parasite, but information on local feline T. gondii infections has been lacking. An epidemiological cross-sectional study was conducted to estimate the seroprevalence of T. gondii and the risk factors associated with seropositivity in cats in Estonia. Surplus from blood samples that had been collected for unrelated diagnostic purposes from 306 pet cats and 184 shelter cats were analyzed for anti-T. gondii immunoglobulin G antibodies by using a direct agglutination test. Two questionnaires were designed to reveal relevant risk factors for seropositivity. The overall seroprevalence of T. gondii in cats in Estonia was 60.8%. Older age, outdoor access, hunting, living outside the city in the countryside, and not being a purebred cat were among the risk factors associated with seropositivity. T. gondii is highly prevalent in domestic cats in Estonia. This suggests that the environment has been contaminated with T. gondii. Seropositivity indicates previous oocyst shedding, and most of the cats had outdoor access. The increase in T. gondii seroprevalence with age indicates acquired infections, and most of the risk factors were lifestyle-related. Cat owners could diminish the risk of T. gondii infection and also limit the spread of the parasite by not allowing their cats to roam free.

Protective immunity against acute toxoplasmosis in BALB/c mice induced by a DNA vaccine encoding Toxoplasma gondii 10 kDa excretory-secretory antigen (TgESA10)

Toxoplasma gondii 10 kDa excretory-secretory antigen (TgESA10) is involved in the early stages of host invasion. The aim of this study was to evaluate the immune protective efficacy of a DNA vaccine encoding TgESA10 gene against acute T. gondii infection in mice. The gene sequence encoding TgESA10 was inserted into the eukaryotic expression vector pVAX I, and the efficacy of intramuscular vaccination of BALB/c mice with pVAX-ESA10 was analyzed. Mice immunized with pVAX-ESA10 elicited high titers of total IgG, IgG1, IgG2a, IgA and IgM antibodies, while IgE showed no changes. Analysis of cytokine profiles revealed significant increases of IFN-γ, IL-4 and IL-17, while no significant changes were detected in TGF-β1. Additionally, we found that pVAX-ESA10 enhanced the activation of CD4(+) and CD8(+) T cells and the expression of MHC-I and MHC-II molecules in spleen in mice. Immunization with pVAX-ESA10 significantly prolonged survival time (14.3 ± 1.7 days) after challenge infection with the virulent T. gondii RH strain, compared with the control groups which died within 8 days. These results suggested that TgESA10 DNA vaccine could trigger strong humoral and cellular responses and induce partial protection against acute toxoplasmosis.

Toxoplasma gondii, Dirofilaria immitis, feline immunodeficiency virus (FIV), and feline leukemia virus (FeLV) infections in stray and pet cats (Felis catus) in northwest China: co-infections and risk factors

This study was conducted to estimate the prevalence of Toxoplasma gondii, Dirofilaria immitis, feline immunodeficiency virus (FIV), and feline leukemia virus (FeLV) infections among stray and pet cats in Lanzhou, northwest China, and to identify the influence of age, gender, and regions on seropositivity. T. gondii antibodies were examined in cat sera by the modified agglutination test (MAT). The circulating antigens of D. immitis and FeLV and specific antibodies to FIV were examined using kits commercially available. The overall prevalence of T. gondii, FIV, FeLV, and D. immitis was 19.34, 9.12, 11.33, and 3.04 %, respectively. For the genetic characterization of T. gondii genotypes in cats, genomic DNA was extracted from the seropositive cats and the T. gondii B1 gene was amplified using a semi-nested PCR. DNA samples giving positive B1 amplification were then genotyped using multilocus PCR-RFLP. Two T. gondii genotypes (ToxoDB#9 and ToxoDB#1) were identified. Results of the multivariate logistic regression analysis showed that older cats are more likely to be seropositive than juveniles for T. gondii, FIV, FeLV, and D. immitis. This is the first report of T. gondii genotypes in cats in northwest China. Moreover, the present study is the first study of retrovirus and D. immitis seroprevalence in cats in China. The results revealed that T. gondii, FIV, and FeLV infections are common in stray and pet cats in northwest China.

The prevalence of antibodies to Toxoplasma gondii in horses in Changji Hui Autonomous Prefecture, Xinjiang, northwestern China

Toxoplasmosis is a worldwide zoonosis caused by Toxoplasma gondii, which can infect warm-blooded animals and humans. The present study was performed to investigate the seroprevalence of T. gondii in horses in Xinjiang, northwestern China. A total of 637 blood samples were collected from seven regions in Changji Hui Autonomous Prefecture, Xinjiang in 2011 and assayed for T. gondiiantibodies using the modified agglutination test (MAT). Risk factors (age, gender, and region) related to seroprevalence were determined by a multivariate logistic regression analysis. A total of 200 horses (31.4%, 95% CI 27.79–35.00) were seropositive for T. gondii. Age, gender, and region present no association with seroprevalence (p>0.05) in the logistic regression analysis. The results indicated that T. gondii is widely prevalent in horses in Xinjiang, northwestern China, representing a serious threat to animal and human health. Therefore, more careful measures should be performed to control and prevent T. gondii infection in horses from Xinjiang, northwestern China.

Early detection of Toxoplasma gondii-infected cats by interferon-gamma release assay

Felines, the only definitive hosts that shed the environmentally-durable oocysts, are the key in the transmission of Toxoplasma gondii to all warm-blooded animals. They seroconvert as late as the third week and begin to shed oocysts as early as 3-8 days after being fed tissue cysts. Early detection of Toxoplasma-infected cats is crucial to evaluate Toxoplasma-contaminated environment and potential risks to public health. Moreover, it is fundamental for Toxoplasma infection control. Interferon-gamma release assay (IGRA) is a blood-based test assessing the presence of IFN-γ released by the T-lymphocytes directed against specific antigens, which is an ideal assay for early detection of Toxoplasma-infected cats. Here, cats were orally infected with the tissue cysts and blood was collected for toxoplasmic antigen stimulation, and the released IFN-γ was measured by ELISA. Results showed that Toxoplasma-infection was detected by IGRA as early as 4 days post-infection (dpi); while serum Toxoplasma IgM and IgG were detected by ELISA at 10 dpi and 14 dpi, respectively. Our findings demonstrated that IGRA-positive and ELISA-negative samples revealed an early Toxoplasma infection in cats, indicating a new strategy for the early diagnosis of Toxoplasma infection by combining IGRA and ELISA. Therefore, IGRA could emerge as a reliable diagnostic tool for the exploration of cat toxoplasmosis prevalence and its potential risks to public health.

Genome-wide expression patterns of calcium-dependent protein kinases in Toxoplasma gondii

Background

Calcium-dependent protein kinases (CDPKs) are found in plants and some Apicomplexan parasites but not in animals or fungi. CDPKs have been shown to play important roles in various calcium-signaling pathways such as host cell invasion, egress and protein secretion in Toxoplasma gondii. The objectives of the present study were to examine the T. gondii CDPK genes expression patterns during different development stages and stress responses.

Methods

We carried out a comprehensive expression analysis of CDPK genes based on previously published microarray datasets, and we also used real time quantitative RT-PCR to study ten T. gondii CDPK genes expression patterns under acid, alkali, high temperature and low temperature conditions.

Results

Microarrays analysis indicated that some TgCDPK genes exhibited different expression levels in IFN-γ stimuli conditions or at different developmental stages, suggesting that CDPK genes may play different roles in these processes. Expression profiles under low temperature, high temperature, acid and alkaline indicated that most CDPK may be involved in regulating high temperature, acid and alkaline signaling pathways.

Conclusions

We present a genome-wide expression analysis of CDPK genes in T. gondii for the first time, and the mRNA levels change with abiotic and biotic stresses, suggesting their functional roles in these processes. These results will provide a solid basis for future functional studies of the CDPK gene family in T. gondii.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0917-z) contains supplementary material, which is available to authorized users.

Toxoplasma gondii Infection Suppresses House Dust Mite Extract-Induced Atopic Dermatitis in NC/Nga Mice

PURPOSE

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects humans and animals via congenital or postnatal routes, and it is found worldwide. Modulation of the immune system by parasite infection is proposed to suppress allergic inflammation. Growing evidences have shown that interleukin (IL)-10-producing regulatory B cells (B(regs)) and CD4+CD25+FoxP3+ regulatory T cells (T(regs)) induced by parasite infection play a critical role in allergic or autoimmune diseases because these cells regulate negatively cellular immune responses and inflammation. Currently, the role of IL-10-producing regulatory B cells in host immune response during T. gondii infection is unknown. In this study, we investigate whether T. gondii infection can suppress the development of unrelated atopic dermatitis (AD)-like lesions.

METHODS

AD is a chronically relapsing inflammatory skin disease accompanied by severe itching; for this, we used NC/Nga mice, a well-known experimental model of systemic AD. Repeated exposure to Dermatophagoides farinae crude extract (DfE), known as a major environmental allergen, evokes AD-like skin lesions in NC/Nga mice under specific pathogen-free conditions. NC/Nga mice were intraperitoneally infected with 10 cysts of T. gondii.

RESULTS

T. gondii infection significantly ameliorated AD-like skin lesions in NC/Nga mice. The subpopulation of B(regs) and T(regs) in the AD mice was expanded in the course of T. gondii infection. In addition, T. gondii infection inhibited Th2 and enhanced Th1 immune response in the DfE-treated AD mice.

CONCLUSIONS

We have experimentally demonstrated for the first time that T. gondii infection ameliorated AD-like skin lesions in a mouse model of AD. Our study could in part explain the mechanisms of how parasite infection prevents the development of allergic disorder. Therefore, these immunemechanisms induced by T. gondii infection may be beneficial for the host in terms of reduced risk of allergic immune reactions.

Cloning and Expression of Major Surface Antigen 1 Gene of Toxoplasma gondii RH Strain Using the Expression Vector pVAX1 in Chinese Hamster Ovary Cells

Background:

Toxoplasmosis is an opportunistic protozoan infection with a high prevalence in a broad range of hosts infecting up to one-third of the world human population. Toxoplasmosis leads to serious medical problems in immunocompromised individuals and fetuses and also induces abortion and mortality in domestic animals. Therefore, there is a huge demand for the development of an effective vaccine. Surface Antigen 1 (SAG1) is one of the important immunodominant surface antigens of Toxoplasma gondii, which interacts with host cells and primarily involved in adhesion, invasion and stimulation of host immune response. Surface antigen 1 is considered as the leading candidate for development of an effective vaccine against toxoplasmosis.

Objectives:

The purpose of this study was to clone the major surface antigen1 gene (SAG1) from the genotype 1 of T. gondii, RH strain into the eukaryotic expression vector pVAX1 in order to use for a DNA vaccine.

Materials and Methods:

Genomic DNA was extracted from tachyzoite of the parasite using the QIAamp DNA mini kit. After designing the specific primers, SAG1 gene was amplified by Polymerase Chain Reaction (PCR). The purified PCR products were then cloned into a pPrime plasmid vector. The aforementioned product was subcloned into the pVAX1 eukaryotic expression vector. The recombinant pVAX1-SAG1 was then transfected into Chinese Hamster Ovary (CHO) cells and expression of SAG1 antigen was evaluated using Reverse Transcriptase Polymerase Chain Reaction (RT-PCR), Immunofluorescence Assay (IFA) and Western Blotting (WB).

Results:

The cloning and subcloning products (pPrime-SAG1 and pVAX1-SAG1 plasmid vectors) of SAG1 gene were verified and confirmed by enzyme digestion and sequencing. A 30 kDa recombinant protein was expressed in CHO cells as shown by IFA and WB methods.

Conclusions:

The pVAX1 expression vector and CHO cells are a suitable system for high-level recombinant protein production for SAG1 gene from T. gondii parasites and are promising approaches for antigen preparation in vaccine development.

Seroprevalence and genetic characterization of Toxoplasma gondii in cancer patients in Anhui Province, Eastern China

Background

Recent studies have indicated the predominance of Toxoplasma gondii genotype Chinese 1 in animals in China. However, little is known of the genetic features of the parasite in humans. This study aims to determine the prevalence of anti-T. gondii antibodies based on which the genetic character of the parasite was identified in cancer patients in China.

Methods

A total of 1014 serum samples with malignant neoplasms were collected from six tertiary-care hospitals (HAUCM, APH, HAMU, XAH, FHH and HBMC) from January, 2012 to August, 2013. Antibodies against T. gondii were examined by enzyme-linked immunosorbent assay (ELISA). Blood samples were subsequently used for PCR assay to detect T. gondii DNA (gra6). The DNA positive samples were subjected to genotyping using a multiplex multilocus nested PCR-RFLP at 10 loci, including sag1, sag2, sag3, btub, gra6, l358, c22-8, c29-2, pk1 and apico. Samples from the patients were anonymous and only data with regard to age and gender was available at sample collection.

Results

Overall, 8.38% (85/1014) of the examined patients showed positive antibodies against T. gondii. Among them, 61 (6.02%) were seropositive only for IgG, 16 (1.58%) were only for IgM, and 8 (0.79%) were found to be positive for both IgG and IgM. The seroprevalence of antibodies to Toxoplasma ranged from 5.8% to 11.0%, without regional difference (χ² = 4.764, P = 0.445). No significant differences of the positive rates of T. gondii infection were noted in genders (male, 8.96%; female, 7.45%) (χ² = 0.707, P = 0.400) and in ages (χ² = 1.172, P = 0.947). Of 1014 DNA samples, 36 (3.55%) were positive for T. gondii by nested PCR at gra6 locus and nine gave rise to complete genotyping results. All samples with achieved PCR-RFLP genotyping showed a common genetic character of type Chinese 1 (ToxoDB#9).

Conclusion

Seroprevalence of toxoplasmosis in immunosuppressed individuals is rarely reported in China and we presented a positive rate of 8.38% in cancer patients. Toxoplasma genomic DNA genotyping demonstrated a common genetic character of Chinese 1, indicating a possible pathogenic origin of animals in human infection.

Prevalence of IgG Antibodies to Toxoplasma gondii in Veterinary and Undergraduate Students at Virginia Tech, Blacksburg, Virginia

Toxoplasma gondii is a globally distributed parasitic protozoan that infects humans and other warm-blooded vertebrates. Felids are the only definitive host for T. gondii, and they excrete oocysts in their faeces. The national prevalence in humans is declining in the United States. This zoonotic organism is of particular interest due to its importance in pregnant women, in individuals with altered immune systems, and in reactivated ocular infections. Exposure to the parasite in humans is usually associated with consumption of raw or undercooked meat or by accidental ingestion of oocysts. It was hypothesized that veterinary students would have a greater chance at exposure to the parasite than an average population of undergraduate students due to increased contact with cats who are infected. A commercially available ELISA was used to examine serum samples from 336 students (252 veterinary students and 84 undergraduate students) at Virginia Polytechnic Institute and State University and the Virginia-Maryland Regional College of Veterinary Medicine for serum IgG antibodies to T. gondii antigen. The prevalence of T. gondii in these subjects was 5.6% in veterinary school students (n = 252) and 2.4% in undergraduates (n = 84). There was no significant difference (P > 0.05) in the prevalence of T. gondii antibodies in veterinary versus undergraduate students. The overall prevalence of 4.8% in all students in this study reflects the continuing decline of antibodies to T. gondii in humans in the United States.

Seroepidemiological analysis of toxoplasmosis in college students

Background

Toxoplasmosis is a zoonosis caused by an obligate intracellular parasite, Toxoplasma gondii, which affects warm-blooded animals including humans. Its prevalence rates usually vary in different regions of the planet.

Methods

In this study, an analysis of the seroprevalence of toxoplasmosis among Brazilian students was proposed by means of IgG specific antibodies detection. The presence of anti-Toxoplasma gondii antibodies by indirect fluorescent antibody test (IFAT) was also evaluated in order to compare it with enzyme-linked immunosorbent assay (ELISA) and to assess the use of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and o-phenylenediamine dihydrochloride chromogens.

Results

The IFAT method showed a seroprevalence of 22.3%. These results were similar to those obtained by ELISA (24.1%). The seroprevalence was directly estimated from the IgG avidity, which showed that in a sample of 112 students, three of them had acute infection, an incidence of 1.6% in the studied population.

Conclusion

In this study, the use of different chromogenic substrates in immunoenzymatic ELISA assays did not display different sensitivity in the detection of T. gondii-reagent serum. The extrapolation of results to this population must be carefully considered, since the investigation was conducted on a reduced sample. However, it allows us to emphasize the importance of careful and well prepared studies to identify risk factors for toxoplasmosis, to adopt preventive measures and to offer guidance to at-risk populations about the disease.

Seroprevalence and risk factors of Toxoplasma gondii and Neospora caninum infections in small ruminants in China

Little information is available about the seroprevalence of Toxoplasma gondii and Neospora caninum infections in sheep and goats in China. In the present investigation, the seroprevalence of T. gondii and N. caninum infections in sheep and goats were investigated in Qinghai province, China between January 2012 and June 2013. A total of 1250 serum samples (600 sheep and 650 goats) collected from 8 administrative regions of Qinghai province, China were evaluated by enzyme-linked immunosorbent assay for the detection of specific antibodies, and sera positive were subsequently confirmed with indirect fluorescent antibody test. Specific IgG against T. gondii were detected in 21.33% (95% confidence interval [CI]: 18.06-24.61%) (128/600) and 29.54% (95% CI: 26.03-33.05%) (192/650) and against N. caninum in 10.33% (95% CI: 7.9-12.77%) (62/600) and 7.23% (95% CI: 5.24-9.22%) (47/650) of the sheep and goats, respectively. The risk factors significantly associated with T. gondii and N. caninum seroprevalence were the presence of cats and dogs, the pasturing system, the herd size, the hygiene in the farms. The results of the present survey indicate that T. gondii and N. caninum infections are highly prevalent in sheep and goats in Qinghai province, China. This is the first time that antibodies to N. caninum have been detected in sheep and goats in China.

Seroprevalence and risk factors of Toxoplasma gondii infection in domestic sika deer (Cervus nippon) in northeastern China

Toxoplasmosis is a worldwide zoonosis caused by Toxoplasma gondii, which can infect warm-blooded animals and humans. A serological survey was undertaken to examine the seroprevalence and risk factors associated with T. gondii infection in sika deer in northeastern China. 114 (13.46%, 95% CI 11.16-15.76) out of 847 serum samples were positive to T. gondii by modified agglutination test (MAT) at a 1:25 cut-off, with titers of 1:25 in 44, 1:50 in 32, 1:100 in 17, 1:500 in 11, 1:1500 or higher in 10. These samples were collected between November 2012 and October 2013 from Inner Mongolia, Jilin and Heilongjiang provinces in China. However, statistically significant differences were not observed between T. gondii seroprevalence and genders or regions of sika deer in the logistic regression analysis (P>0.05) and left out of the final model. Seroprevalence of T. gondii infection in male sika deer was 14.07% (95% CI 11.14-17.01), slightly higher than that in the female (12.38%) (95% CI 8.69-16.06) and seroprevalence of T. gondii infection in Harbin, Changchun city, Jilin city and Chifeng city were 12.02% (95% CI 7.60-16.44), 15.51% (95% CI 11.52-19.50), 12.27% (95% CI 7.23-17.31) and 12.50% (95% CI 7.38-17.63), respectively. Seasons of sampling were considered as main risk factors associated with T. gondii infection, autumn (15.32%) were more than two times (OR=1.98, 95% CI=1.18-3.33, P=0.01) at risk of acquiring T. gondii infection compared to winter (8.37%). Our results indicated a widespread exposure to T. gondii among sika deer in China. To our knowledge, this is the first report of T. gondii seroprevalence in sika deer in China.

Functional analysis of rhomboid proteases during Toxoplasma invasion

Host cell invasion by Toxoplasma gondii and other apicomplexan parasites requires transmembrane adhesins that mediate binding to receptors on the substrate and host cell to facilitate motility and invasion. Rhomboid proteases (ROMs) are thought to cleave adhesins within their transmembrane segments, thus allowing the parasite to disengage from receptors and completely enter the host cell. To examine the specific roles of individual ROMs during invasion, we generated single, double, and triple knockouts for the three ROMs expressed in T. gondii tachyzoites. Analysis of these mutants demonstrated that ROM4 is the primary protease involved in adhesin processing and host cell invasion, whereas ROM1 or ROM5 plays negligible roles in these processes. Deletion of ROM4 blocked the shedding of adhesins such as MIC2 (microneme protein 2), causing them to accumulate on the surface of extracellular parasites. Increased surface adhesins led to nonproductive attachment, altered gliding motility, impaired moving junction formation, and reduced invasion efficiency. Despite the importance of ROM4 for efficient invasion, mutants lacking all three ROMs were viable and MIC2 was still efficiently removed from the surface of invaded mutant parasites, implying the existence of ROM-independent mechanisms for adhesin removal during invasion. Collectively, these results suggest that although ROM processing of adhesins is not absolutely essential, it is important for efficient host cell invasion by T. gondii.

Apicomplexan parasites such as Toxoplasma gondii express surface proteins that bind host cell receptors to aid invasion. Many of these adhesins are subject to cleavage by rhomboid proteases (ROMs) within their transmembrane segments during invasion. Previous studies have demonstrated the importance of adhesin cleavage for parasite invasion and proposed that the ROMs responsible for processing would be essential for parasite survival. In T. gondii, ROM5 was thought to be the critical ROM for adhesin shedding due to its robust protease activity in vitro and posterior localization on the parasite surface. Here, we knocked out all three ROMs in T. gondii tachyzoites and found that ROM4, but not ROM5, was key for adhesin cleavage. However, none of the ROMs individually or in combination was essential for cell entry, further emphasizing that essential pathways such as invasion typically rely on redundant pathways to ensure survival.

Innate resistance against Toxoplasma gondii: an evolutionary tale of mice, cats, and men

Recent studies have revealed remarkable species specificity of the Toll-like receptors (TLRs) TLR11 and TLR12 and the immunity-related GTPase (IRG) proteins that are essential elements for detection and immune control of Toxoplasma gondii in mice, but not in humans. The biological and evolutionary implications of these findings for the T. gondii host-pathogen relationship and for human disease are discussed.

Prevalence of Toxoplasma infection in veterinary laboratory sciences students comparing to ordinary people: a case-control study

Toxoplasma gondii causes the foremost widespread protozoan infection with a broad variety of host range, which consists of regarding of almost all warm-blooded vertebrates. There are some opinions concerning the probable occupational influence on infections to Toxoplasma in veterinary services personnel. The present study aimed to examine influence of studying in veterinary laboratory sciences as a risk factor on the prevalence rate of Toxoplasma infection in the students. In this case-control study, 80 blood samples were taken from veterinary laboratory sciences students (VLSS) as a case group and 80 blood samples from ordinary people of general population as a control group with the relatively same age, gender and health condition. Anti-Toxoplasma IgG levels in the serum samples were determined using quantitative ELISA method. According to the results, 27 (33.75 %) out of 80 samples of the cases group and also 29 (36.2 %) out of 80 samples of the control group were infected by the parasite. No statistically significant difference observed in the infection rate between the case and control groups (P = 0.740, OR 0.931; 95 % CI 0.61, 1.421). The mean serum antibody concentration in infected subjects of case and control groups showed no statistically significant difference (P = 0.618, t = 0.502). Normality of the data was assumed using Kolmogorov-Smirnov test (P = 0.806, Z = 0.641). Based on the results, in veterinary laboratory science students, toxoplasmosis is not related to their career and also the subjects of this group as the other people have the same risk to infect by this protozoan parasite.

Seroprevalence, risk factors and genotyping of Toxoplasma gondii in domestic geese (Anser domestica) in tropical China

BACKGROUND

Little information is available about the seroprevalence of Toxoplasma gondii infection in geese (Anser domestica) in China. In the present investigation, the seroprevalence, risk factors and genotyping of T. gondii in geese were investigated in Hainan province, tropical China.

FINDINGS

A total of 600 serum samples and 150 brain tissue samples were collected from six administrative regions in tropical China, and assayed for T. gondii antibodies by Indirect Haemagglutination (IHA) test. Genomic DNA was extracted from the 30 brain tissues of seropositive geese and T. gondii B1 gene was amplified using a semi-nested PCR. DNA samples giving positive B1 amplification were then genetically characterized using multi-locus PCR-RFLP. Overall, 17% (95% CI: 14-20) of the animals were positive for T. gondii antibodies. Presence of cats in the household (odds ratio, OR 3), hygiene (OR 2.3) and presence of stray cat around the house (OR 2.3) were considered as main risk factors associated with T. gondii infection. Of 30 DNA samples, three were positive for the T. gondii B1 gene, two showed complete genotyping results. Only one genotype (type II) was identified.

CONCLUSIONS

The results of the present survey indicated the presence of T. gondii infection in geese in tropical China. Therefore, it is imperative that improved integrated measures be carried out to prevent and control T. gondii infection in geese in this province. This is the first report documenting the occurrence of T. gondii genotype in geese in China.

Detection of Toxoplasma gondii oocysts in soils in northwestern China using a new semi-nested PCR assay

BACKGROUND

Toxoplasma gondii is a zoonotic pathogen that can infect a range of animals and humans. Ingestion of T. gondii oocysts in soil is a significant transmission route for humans and animals acquiring toxoplasmosis. In the present study, we developed a new semi-nested PCR method to determine T. gondii oocysts distribution in soils in northwestern China.

RESULTS

The one tube semi-nested PCR assay was developed to detect the oocysts of T. gondii in soil, targeting the repetitive 529 bp fragment of T. gondii genomic DNA. Then a total of 268 soil samples, including 148 samples from Gansu Province and 120 samples from Qinghai Province, northwestern China, were examined by the semi-nested PCR method. One third of the positive samples were sequenced. The sensitivity of the semi-nested PCR assay was 10(2)  T. gondii oocysts in 5 g soil sample. Investigation of soil samples from northwestern China showed that 34 out of 268 soil samples (12.69%) were T. gondii positive. Sequences of the partial 529 bp fragments varied from 0-1.2% among the sequenced samples. The prevalence of T. gondii oocysts in soil from cities (24/163) was slightly higher than that in soils from pasturing areas (10/105) (P = 0.21). Among the different regions in cities, the prevalence of T. gondii oocysts in soils from parks was 14.15%, whereas that in soils from schools was 19.05%.

CONCLUSIONS

The present study firstly reported the prevalence of T. gondii oocysts in soils in northwest China using a novel semi-nested PCR assay, which provided baseline data for the effective prevention and control of toxoplasmosis in this region.

Animals are key to human toxoplasmosis

Toxoplasma gondii is an extremely sucessfull protozoal parasite which infects almost all mamalian species including humans. Approximately 30% of the human population worldwide is chronically infected with T. gondii. In general, human infection is asymptomatic but the parasite may induce severe disease in fetuses and immunocompromised patients. In addition, T. gondii may cause sight-threatening posterior uveitis in immunocompetent patients. Apart from few exceptions, humans acquire T. gondii from animals. Both, the oral uptake of T. gondii oocysts released by specific hosts, i.e. felidae, and of cysts persisting in muscle cells of animals result in human toxoplasmosis. In the present review, we discuss recent new data on the cell biology of T. gondii and parasite diversity in animals. In addition, we focus on the impact of these various parasite strains and their different virulence on the clinical outcome of human congenital toxoplasmosis and T. gondii uveitis.

Protective efficacy of Toxoplasma gondii calcium-dependent protein kinase 1 (TgCDPK1) adjuvated with recombinant IL-15 and IL-21 against experimental toxoplasmosis in mice

Background

Toxoplasma gondii can infect all warm-blooded animals including humans. Infection with T. gondii is probably the leading cause of posterior uveitis in humans and the most comment route of transmission is raw and undercooked meat from infected animals. T. gondii calcium-dependent protein kinase 1 (TgCDPK1) plays a critical role in direct parasite motility, host-cell invasion, and egress.

Methods

We constructed a DNA vaccine expressing TgCDPK1 inserted into eukaryotic expression vector pVAX I and evaluated the immune protection induced by pVAX-CDPK1 in Kunming mice. Mice immunized with pVAX-CDPK1 intramuscularly and/or with a plasmid encoding IL-15 and IL-21 (pVAX-IL-21-IL-15). The immune responses were analyzed including lymphoproliferative assay, cytokine, antibody measurements, lymphocyte surface markers by flow cytometry and protective efficacy were measured as survival and cysts numbers after challenge 1 to 2 months post vaccination.

Results

Immunization with pVAX-CDPK1 or pVAX-IL-21-IL-15 alone developed strong humoral responses and Th1 type cellular immune responses, and the significantly (P < 0.05) increase of both the percentages of CD4+ and CD8+ T cells compared with all the controls (blank control, PBS, and pVAX). Co-injection of pVAX-IL-21-IL-15 significantly increased humoral and cellular immune responses compared to the group of pVAX-CDPK1 or pVAX-IL-21-IL-15. Challenge experiments showed that co-administration of pVAX-IL-21-IL-15 and pVAX-CDPK1 significantly (P < 0.05) increased survival time (19.2 ± 5.1 days) compared with pVAX-CDPK1 (17.3 ± 4.3 days) or pVAX-IL-21-IL-15 (12.0 ± 2.0 days) alone, and pVAX-IL-21-IL-15 + pVAX-CDPK1 significantly reduced the number of brain cysts (72.7%) in contrast to pVAX-ROP13 (45.7%) or pVAX-IL-21-IL-15 alone (43.6%).

Conclusions

TgCDPK1 is identified to be a promising vaccine candidate for inducing a strong humoral and cellular response against T. gondii infection, and thus synergistic of mIL-21 and mIL-15 can induce non-specific immune responses, but also facilitate specific humoral as well as cellular immune responses elicited by DNA vaccine against acute and chronic T. gondii infection in mice.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-487) contains supplementary material, which is available to authorized users.

Genetic characterization of Toxoplasma gondii isolates and toxoplasmosis seroprevalence in stray cats of İzmir, Turkey

Currently, some Toxoplasma gondii genotypes are being associated with serious clinical presentations. A recent report showing the Africa 1 genotype in two local congenital toxoplasmosis cases acquired in Turkey formed the basis of this study because atypical Africa 1 genotype is most frequently detected in animals and patients from sub-Saharan Africa. Since stray cats are considered as the linkage between wild life and urban life in T. gondii transmission, the present study aimed to isolate and characterize T. gondii strains circulating in stray cats of İzmir (Western Turkey). A secondary objective was to determine toxoplasmosis seroprevalence in this cat population. Tissues obtained from 100 deceased stray cats were bioassayed and isolated strains were genotyped using 15 microsatellite markers. In addition, toxoplasmosis seroprevalence was analyzed in 1121 cat sera collected from several large veterinary clinics in İzmir. Among the 22 isolates, 19 were Type II (86.3%), two were Type III (9%) and one was Africa 1 genotype (4.5%). The overall seropositivity rates in cats were 42-48% and 33.4-34.4% according to IFA and ELISA, respectively. Seroprevalence in deceased cats was significantly higher than in healthy cats (P = 0.0033). Finding both the major clonal Type II lineage together with the Type III lineage also found in Middle East, and an atypical genotype, Africa 1 appears consistent with the specific geographic location of Turkey between three continents and raises the possibility of transportation of these strains between continents through trade routes or long distance migratory birds. In addition, the first large study of toxoplasma seroprevalence in a stray cat population was also reported. The relatively high seropositivity rates and the variety of T. gondii genotypes confirm the local stray cat population as a risk factor for human toxoplasmosis in İzmir.

Molecular and Serological Evaluation of Toxoplasma gondii Infection in Reared Turkeys in Fars Province, Iran

Background:

Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. This parasite infects most of warm-blooded animals, including birds. Turkeys are one of these animals which might be infected by this parasite. Little is known about the prevalence of T. gondii in turkeys in Iran.

Objectives:

The current study aimed to evaluate the rate of Toxoplasma infection in turkeys in Fars Province, Southern Iran.

Materials and Methods:

Sera and tissues (brain, neck and tongue) of 54 turkeys were collected from Shiraz slaughterhouse in Fars province. Anti-Toxoplasma antibodies were assessed in the collected sera using modified agglutination test (MAT), while tissues were evaluated by polymerase chain reaction (PCR) and bioassay methods.

Results:

T. gondii antibodies (MAT titer: ≥ 1:40) were found in 89.8% of turkeys. T. gondii DNA was detected in 61.6% of turkey tissues and brain had the highest rate of infection. Brain tissues from each animal were bioassayed and Toxoplasma tissue cysts were found in 11.5% and Toxoplasma DNA in 62% of inoculated mice.

Conclusions:

Results of this study validated a relatively high level of Toxoplasma infection in reared turkeys and turkey meat might be considered as an infection sources for human.

Seroepidemiology of Toxoplasma gondii infection in Bai and Han ethnic groups in southwestern China

Eating raw pork and/or liver is a custom of the Bai ethnic group in China. Most people living in Dali Bai Autonomous Prefecture, Yunnan Province, southwestern China are of Bai ethnicity. Little is known of the seroprevalence of Toxoplasma gondii in Bai and Han ethnic populations in this region. In the present survey, a total of 555 and 595 blood samples were obtained from Bai and Han ethnic groups in Dali urban and rural areas, respectively. Enzyme-linked immunosorbent assay was performed to examine T. gondii IgG antibodies. Total positive rate of anti-T. gondii IgG in Bai and Han groups in this region was 21·6% (248/1150). The total seroprevalence of T. gondii was significantly higher in the Bai ethnic group (32·3%, 179/555) than in the Han ethnic group (11·6%, 69/595) (P < 0·01). The results of statistical analysis indicated that there was no significant difference between cat feeding/non-cat feeding groups in the Bai ethnic group, the most important risk factor was consumption of raw pork and/or liver for the Bai group, but feeding a cat may be the main route of T. gondii infection for the Han group. Therefore, it is essential to implement integrated strategies to prevent and control T. gondii infection in this unique region of the world.

What makes a feline fatal in Toxoplasma gondii's fatal feline attraction? Infected rats choose wild cats

Toxoplasma gondii is an indirectly transmitted protozoan parasite, of which members of the cat family (Felidae) are the only definitive hosts and small mammals such as rats serve as intermediate hosts. The innate aversion of rodents to cat odor provides an obstacle for the parasite against successful predation by the feline definitive host. Previous research has demonstrated that T. gondii appears to alter a rat's perception of the risk of being preyed upon by cats. Although uninfected rats display normal aversion to cat odor, infected rats show no avoidance and in some cases even show attraction to cat odor, which we originally termed the "Fatal Feline Attraction." In this study, we tested for the first time whether the "Fatal Feline Attraction" of T. gondii-infected rats differed according to the type of feline odor used, specifically whether it came from domestic cats (Felis silvestris catus) or wild cats-cheetahs (Acinonyx jubatus) or pumas (Felis concolor). In two-choice odor trials, where wild and domestic cat odors were competed against one another, consistent with previous findings we demonstrated that infected rats spent more time in feline odor zones compared with uninfected rats. However, we further demonstrated that all cat odors are not equal: infected rats had a stronger preference for wild cat odor over that of domestic cats, an effect that did not differ significantly according to the type of wild cat odor used (cheetah or puma). We discuss these results in terms of the potential mechanism of action and their implications for the current and evolutionary role of wild, in addition to domestic, cats in transmission of T. gondii.

First report of Toxoplasma gondii seroprevalence in pet parrots in China

Toxoplasmosis, caused by the obligate intracellular protozoan parasite Toxoplasma gondii, has become a serious public health problem worldwide. T. gondii can infect almost all warm-blooded animals, including parrots. However, little is known of T. gondii infection in parrots in China. Antibodies against T. gondii in 311 parrots including 202 Budgerigars (Melopsittacus undulatus), 26 Lovebirds (Agapornis sp.), 22 Cockatiels (Nymphicus hollandicus), and 61 Alexandrine Parakeets (Psittacula eupatria) in the cities of Beijing and Weifang in north China were tested using the modified agglutination test (MAT). Twenty-six (8.36%) out of 311 serum samples were positive for T. gondii at the cutoff of 1:5. Among the four species, a higher seroprevalence of T. gondii was found in Cockatiels (13.64%, 95% confidence interval [CI] 0.00-27.98), although the difference was not statistically significant (p=0.61). Seropositivity rates against T. gondii in male parrots (10.43%, 95% CI 5.74-15.12) were not statistically different from that in female parrots (6.08%, 95% CI 2.23-9.93, p=0.17). The seropositivity of T. gondii in parrots from Weifang and Beijing was 11.11% (95% CI 6.13-16.09) and 5.70% (95% CI 2.08-9.31), respectively. The seroprevalence varied in parrots of different age groups, ranging from 5.71% (95% CI 1.27-10.15) to 13.00% (95% CI 6.41-19.69), however, the difference among age groups was not statistically significant (p=0.12). The seroprevalence of T. gondii infection in parrots in summer (11.63%, 95% CI 6.84-16.42) was significantly higher than in spring (4.32%, 95% CI 0.94-7.70, p=0.02). The results of the present survey indicated that parrots in China are exposed to T. gondii. To our knowledge, this is the first report of T. gondii seroprevalence in parrots in China.

Veterinary vaccines against toxoplasmosis

Toxoplasma gondii is a cosmopolitan protozoan parasite that infects a wide range of mammal and bird species. Common infection leads to high economic (e.g., abortions in sheep) and human (e.g., congenital toxoplasmosis or neurotoxoplasmosis in humans) losses. With one exception (Toxovax for sheep), there are no vaccines to prevent human or animal toxoplasmosis. The paper presents the current state and challenges in the development of a vaccine against toxoplasmosis, designed for farm animals either bred for consumption or commonly kept on farms and involved in parasite transmission. So far, the trials have mostly revolved around conventional vaccines and, compared with the research using laboratory animals (mainly mice), they have not been very numerous. However, the results obtained are promising and could be a good starting point for developing an effective vaccine to prevent toxoplasmosis.

Evaluation of immune responses in mice after DNA immunization with putative Toxoplasma gondii calcium-dependent protein kinase 5

Toxoplasma gondii can cause serious public health problems and economic losses worldwide. Calcium-dependent protein kinases (CDPKs) are key mediators of T. gondii signaling pathways and are implicated as important virulence factors. In the present study, we cloned a novel T. gondii CDPK gene, named TgCDPK5, and constructed the eukaryotic expression vector pVAX-CDPK5. Then, we evaluated the immune protection induced by pVAX-CDPK5 in Kunming mice. After injection of pVAX-CDPK5 intramuscularly, immune responses, determined with lymphoproliferative assays and cytokine and antibody measurements, were monitored, and mouse survival times and brain cyst formation were evaluated following challenges with the T. gondii RH strain (genotype I) and the PRU strain (genotype II). pVAX-CDPK5 effectively induced immune responses with increased specific antibodies, a predominance of IgG2a production, and a strong lymphocyte proliferative response. The levels of gamma interferon (IFN-γ), interleukin 2 (IL-2), and IL-12(p70) and the percentages of CD3(+) CD4(+) and CD3(+) CD8(+) cells in mice vaccinated with pVAX-CDPK5 were significantly increased. However, IL-4 and IL-10 were not produced in the vaccinated mice. These results demonstrate that pVAX-CDPK5 can elicit strong humoral and cellular Th1 immune responses. The survival time of immunized mice challenged with the T. gondii RH strain (8.67 ± 4.34 days) was slightly, but not significantly, longer than that in the control groups within 7 days (P > 0.05). The numbers of brain cysts in the mice in the pVAX-CDPK5 group were reduced by ∼40% compared with those in the control groups (P < 0.05), which provides a foundation for the further development of effective subunit vaccines against T. gondii.

Experimental infection of Calomys callosus with atypical strains of Toxoplasma gondii shows gender differences in severity of infection

There is a significant genetic diversity of Toxoplasma gondii in Brazil. Two parasite isolates were recently obtained from chickens in Uberlândia, Minas Gerais state, Brazil, namely, TgChBrUD1 and TgChBrUD2. In this study, we investigated Calomys callosus susceptibility to these atypical T. gondii strains. Male and female animals were intraperitoneally infected with tachyzoites and monitored to evaluate body weight change, morbidity, and mortality. Immunohistochemical assay and qPCR were performed to determine the parasitism in liver, spleen, and brain. Our data showed that TgChBrUD2-infected males died earlier than TgChBrUD1-infected males and 100% of mortality was observed after 10 and 12 days of infection, respectively. Also, TgChBrUD1-infected females died earlier than TgChBrUD1-infected males and 100% of mortality was observed after 9 and 12 days of infection, respectively. Both strains were able to induce a decrease in body weight of males, but only the TgChBrUD1 strain induced an increase in body weight of females. TgChBrUD2-infected females had significantly higher parasite load in both liver and spleen in comparison to TgChBrUD1-infected females, but no significant difference was found between genders or strains when males were infected. There was higher parasitism in the liver than the brain from both males and females infected with either strain. In conclusion, C. callosus specimens are susceptible to both T. gondii atypical strains with differences between males and females in severity of infection. These findings open new prospects for understanding different aspects of T. gondii infection, including reinfection and vertical transmission with these atypical strains when utilizing this experimental model.

Toxoplasmosis and pregnancy

Question Congenital toxoplasmosis is a dangerous fetal infection. Why is routine screening for Toxoplasma gondii infection during pregnancy not available for most Canadians? Answer Low prevalence of the infection, high cost associated with testing, low sensitivity of screening tests, false-positive test results, and limitations of treatment effectiveness are all cited as reasons for not routinely screening for T gondii infection in Canada. Currently, screening for the detection of T gondii is only performed in Nunavik and other parts of northern Quebec owing to the high prevalence of infection in this region. Congenital toxoplasmosis causes neurologic or ocular disease (leading to blindness), as well as cardiac and cerebral anomalies.

Seroprevalence and genetic characterization of Toxoplasma gondii in three species of pet birds in China

Background

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is one of the most common zoonosis worldwide, affecting a wide range of warm-blooded mammals and birds worldwide. However, no information on T. gondii infection in pet birds in China is available. Therefore, this study was performed to determine the prevalence of T. gondii infection in pet birds in Gansu province, China.

Methods

A total of 687 blood samples were collected from pet birds (Carduelis spinus, Alauda gulgula, Cocothraustes migratorlus) in three representative administrative regions in Gansu province, northwest China between August 2011 and September 2012 T. gondii antibodies were determined using the modified agglutination test (MAT). Genomic DNA was extracted from the brain tissues of seropositive pet birds and T. gondii B1 gene was amplified using a semi-nested PCR.DNA samples giving positive B1 amplification were then genetically characterized using multi-locus PCR-RFLP.

Results

The overall T. gondii seroprevalence was 11.21% (77/687). C. spinus had the highest T. gondii seroprevalence (11.65%), followed by A. arvensis (11.39%) and C. migratorlus (5.26%), these differences were not statistically significant (P > 0.05). Of 77 DNA samples, 8 were positive for the T. gondii B1 gene, four showed complete genotyping results. Only one genotype (the Type II variant: ToxoDB genotype #3) was identified.

Conclusions

The results of the present survey indicated the presence of T. gondii infection in pet birds in Gansu province, China. These data provide base-line information for the execution of control strategies against T. gondii infection in pet birds. To our knowledge, this is the first report documenting the occurrence of T. gondii prevalence and genotype in pet birds in China.

Routine screening of harmful microorganisms in beach sands: implications to public health

Beaches worldwide provide recreational opportunities to hundreds of millions of people and serve as important components of coastal economies. Beach water is often monitored for microbiological quality to detect the presence of indicators of human sewage contamination so as to prevent public health outbreaks associated with water contact. However, growing evidence suggests that beach sand can harbor microbes harmful to human health, often in concentrations greater than the beach water. Currently, there are no standards for monitoring, sampling, analyzing, or managing beach sand quality. In addition to indicator microbes, growing evidence has identified pathogenic bacteria, viruses, and fungi in a variety of beach sands worldwide. The public health threat associated with these populations through direct and indirect contact is unknown because so little research has been conducted relating to health outcomes associated with sand quality. In this manuscript, we present the consensus findings of a workshop of experts convened in Lisbon, Portugal to discuss the current state of knowledge on beach sand microbiological quality and to develop suggestions for standardizing the evaluation of sand at coastal beaches. The expert group at the "Microareias 2012" workshop recommends that 1) beach sand should be screened for a variety of pathogens harmful to human health, and sand monitoring should then be initiated alongside regular water monitoring; 2) sampling and analysis protocols should be standardized to allow proper comparisons among beach locations; and 3) further studies are needed to estimate human health risk with exposure to contaminated beach sand. Much of the manuscript is focused on research specific to Portugal, but similar results have been found elsewhere, and the findings have worldwide implications.

Survey of Toxoplasma gondii and Neospora caninum, haemotropic mycoplasmas and other arthropod-borne pathogens in cats from Albania

Background

Albania is a country on the western part of the Balkan Peninsula. The Mediterranean climate is favourable for the stable development of many arthropod species, which are incriminated as vectors for various agents. Recently, several papers have reported on epidemiological aspects of parasitic diseases including vector-borne disease agents of dogs with zoonotic characteristics in Albania. However, data on the epidemiology of feline parasitic and bacterial agents in Albania is scarce.

Methods

Serum and EDTA-blood samples collected from 146 domestic cats from Tirana during 2008 through 2010 were examined for exposure to Toxoplasma gondii, Neospora caninum, Leishmania infantum, and Anaplasma spp. with IFAT, for infection with L. infantum, A. phagocytophilum, Bartonella spp. and haemotropic mycoplasmas with conventional PCR and real-time PCR and for Dirofilaria immitis with antigen ELISA. Additionally blood smear microscopy was carried out for detection of blood-borne pathogens.

Results

Antibodies to T. gondii (titre ≥1:100) were demonstrated in 91 cats (62.3%). Antibodies to N. caninum (titre ≥1:100), L. infantum (titre ≥1:64) and Anaplasma spp. (titre ≥1:100) were found in the serum of 15 (10.3%), 1 (0.7%) or 3 (2.1%) cats, respectively. DNA of haemotropic mycoplasmas was detected in the blood of 45 cats (30.8%), namely Candidatus Mycoplasma haemominutum (21.9%), Mycoplasma haemofelis (10.3%), and Candidatus Mycoplasma turicensis (5.5%), with ten cats harbouring co-infections of two mycoplasmas each; blood from one cat was PCR positive for Bartonella henselae. No DNA of Leishmania spp. and A. phagocytophilum or circulating D. immitis antigen was detected in any cat sample. The overall prevalence of haemotropic mycoplasmas was significantly higher in male compared to female cats (40.6% vs. 24.1%, p = 0.0444); and age was associated positively with the prevalence of antibodies to T. gondii (p = 0.0008) and the percentage of haemotropic mycoplasma infection (p = 0.0454).

Conclusions

With the broad screening panel including direct and indirect methods applied in the present study, a wide spectrum of exposure to or infection with parasitic or bacterial agents was detected.