Detection of Toxoplasma gondii in faeces of privately owned cats using two PCR assays targeting the B1 gene and the 529-bp repetitive element

RPA-CRISPR/Cas9-based method for the detection of Toxoplasma gondii: A proof of concept

Toxoplasma gondii is a widespread and specialized intracellular protozoan pathogen that affects one third of the world' s population, posing a great threat to public health. As the definitive host, cats excrete oocysts and play a crucial role in the transmission of toxoplasmosis. The current diagnostic tools usually require bulky equipment and expertize, which hinders the efficient diagnosis and intervention of Toxoplasma infection in cats. In this study, we combined (RPA) with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technique to establish an easier method for the detection of T. gondii oocysts in cat fecal samples. The sensitivity, specificity, and practicability of the established RPA-CRISPR/Cas9 method were evaluated using a lateral flow strip, with the limitation of detection determined at 10 plasmid copies/μL (corresponding to about one oocyst), cross reactivity to none of Giardia lamblia, Cryptosporidium sp., Microsporidium biberi and Blastocystis hominis that also commonly found in cats, and comparable performance in detecting T. gondii in clinical samples to conventional PCR amplification. This RPA-CRISPR/Cas9 method provides an alternative to conventional molecular tools used in the clinical diagnosis of Toxoplasma infection in cats and other animals.

Prevalence and Molecular Characterization of Toxoplasma gondii and Toxocara cati Among Stray and Household Cats and Cat Owners in Tehran, Iran

Toxoplasma gondii and Toxocara spp. are the most critical parasites common between humans and cats. The close association of cats with humans in urban areas persuaded us to investigate the prevalence of these parasites in stray and household cats and their possible role in the owners' infection. Herein, 132 and 33 fecal samples of stray and household cats, respectively, and 33 blood samples of their owners were collected in Tehran, Iran. The prevalence of T. gondii was determined by targeting the B1 gene in the feces of stray and household cats and the blood of cat owners. Furthermore, genotypes of T. gondii were identified based on the multilocus genotyping of BTUB, GRA6, SAG3, and APICO loci. Toxocara spp. were detected by targeting the second internal transcribed spacer (ITS-2) of the ribosomal DNA of these parasites in the cats' feces and the humans' blood. Also, Toxocara IgG was assessed in the human serum samples. The B1 gene amplification showed that 15.2% of stray cats, 18.2% of household cats, and 51.5% of cat owners were infected with T. gondii. The multilocus sequence analysis revealed the predominance of genotype I of T. gondii in stray cats and genotype II of T. gondii in household cats and cat owners. The amplifying of ITS-2 revealed a high prevalence of T. cati infection (47.0%) in stray cats, whereas no infection was found in the feces of household cats or the serum of cat owners. Likewise, Toxocara IgG was not detected in the serum of humans. The lower prevalence of T. gondii in stray/household cats than in the cat owners indicates the limited impact of close contact with infected cats in human toxoplasmosis. However, the high prevalence of T. cati infection in stray cats can cause contamination of the environment by excreting eggs that may lead to infecting humans through soil or water. Therefore, public health education in urban management planning is necessary for routine urban cat deworming programs and for training the healthcare workers to prevent, control, and treat these infections.

Standardization of the PCR Technique for the Detection of the Toxoplasma gondii B1 Gene in Meat and Water Samples and Cloning of the Product for Use as Control

INTRODUCTION

Toxoplasmosis is caused by the parasite Toxoplasma gondii. The infection is generally asymptomatic and the most severe cases occur in immunosuppressed patients. The main route of transmission is the ingestion of water or food contaminated with cysts of the parasite. The objective of this work was the standardization of the PCR for the detection of the T. gondii B1 gene in meat and water samples and cloning of the product for use as a control.

METHODS

The optimal reaction conditions of the different components of the PCR were determined and the technique was used to detect DNA from meat and water samples. Bands were purified and cloned into a pGEM-T-Easy vector and used as a control in the PCR.

RESULTS

Optimal PCR conditions were; 100 µM dNTP, 0.4 µM primers, and 0.5 U Taq polymerase. The product obtained from the PCR was cloned with a simple cloning strategy with efficient results. With the standardized PCR and using the cloned DNA as a control, T. gondii DNA was detected in 90% of the positives samples of meat and water and there was no amplification in the negative samples.

CONCLUSIONS

The PCR assay standardized in this study was demonstrated to be an effective technique to detect T. gondii DNA in meat and water samples. The cloning of PCR product and its application as a control in molecular diagnosis of toxoplasmosis might improve the reproducibility of this method and avoid the use of patient samples or cultures, which present several limitations.

Rapid detection of Toxoplasma gondii DNA in cat feces using colorimetric loop-mediated isothermal amplification (LAMP) assays targeting RE and B1 genes

Toxoplasma gondii is an obligate protozoan parasite that can infect mammals and birds. Cats are the definitive host of T. gondii and have a very important role in transmission of toxoplasmosis due to the shedding of millions of unsporulated oocysts, that become infective in the environment. Since cats play a major key role in the epidemiology of toxoplasmosis, rapid and accurate diagnosis of infected cats has utmost importance. In this study, we developed a novel colorimetric loop mediated isothermal amplification (LAMP) assay detecting T. gondii RE gene and modified a previously developed colorimetric LAMP assay targeting B1 gene to detect T. gondii DNA in cat feces for the first time. The analytical sensitivity of colorimetric LAMP assays was determined using plasmid controls. The clinical sensitivities of both colorimetric LAMPs were determined using cat fecal DNA samples that were confirmed to be positive by two different real-time PCRs in our previous study. According to the results, analytical sensitivities of both assays were 1 copy plasmid/reaction. Using real-time PCR as a reference method, sensitivities of colorimetric LAMP assays targeting RE and B1 genes were 100% and 97.56% whereas specificities of both assays were 100%. Overall, the colorimetric LAMP RE assay developed in this study brings an advantage in the diagnosis of T. gondii in cat fecal samples since it has higher sensitivity, does not need for experienced personnel, and can be applied in basic laboratories or in the field.

Towards an Integrated Approach for Monitoring Toxoplasmosis in Southern Italy

Simple Summary

Toxoplasmosis is a significant public health issue worldwide, caused by the intracellular protozoan Toxoplasma gondii. It has a heteroxenous life cycle in which felines act as definitive reservoirs and a wide range of warm-blooded animals, including humans, act as intermediate hosts. Due to the complex life cycle, monitoring, prevention and control of this parasite are very difficult. A thorough analysis of the epidemiology of T. gondii in humans, animals and food as well as the risk factors associated with the infection are needed to plan adequate control strategies in a given geographical area. Based on this, an integrated approach for monitoring toxoplasmosis was developed and conducted in an endemic area of southern Italy. The main tasks of this approach were based on the following strategies: parasitological and risk factor analysis for T. gondii in livestock farms, serological and molecular monitoring in meat-producing livestock at slaughterhouses, hospital discharge records (HDRs) analysis and outreach activities. The findings of this study confirmed the spread of T. gondii infection in southern Italy with high prevalence values in ruminants and the need of valid control strategies based on comprehensive and transdisciplinary actions according to the One Health approach.

Abstract

Toxoplasmosis is a widespread worldwide zoonotic infection caused by the intracellular protozoan Toxoplasma gondii. This protozoan infection is considered one of the most important food-borne parasitic zoonoses globally. Beyond its impact on public health, toxoplasmosis has also important veterinary implications, because it causes miscarriage or congenital malformations in livestock with negative economic impacts. An integrated monitoring programme aimed to deepen the epidemiological data on toxoplasmosis and to identify the risk factors that may favour T. gondii infections in animals and humans was conducted in an endemic area of southern Italy. The monitoring activities were based on the following tasks: (i) parasitological analysis and risk factors for T. gondii in livestock (sheep, goat, cattle and water buffalo) farms; (ii) serological and molecular monitoring at slaughterhouse in meat-producing livestock; (iii) analysis of hospital discharge records (HDRs); (iv) outreach activities (information, dissemination and health education) to farmers, vet practitioners and school-age children. The present study confirmed a very high seroprevalence of T. gondii infection in livestock farms (e.g., up to 93.1% in sheep farms) in southern Italy and highlighted the potentially significant public health risk in this area.

Copro-PCR in the detection and confirmation of Toxoplasma gondii oocysts in feces of stray and domiciled cats

Molecular methods such as Copro-PCR stand out in the diagnosis of T. gondii, because they are highly sensitive and specific, and can distinguish T. gondii from other morphologically similar coccids. The purpose was the detection of Toxoplasma gondii copro-prevalence by polymerase chain reaction in 149 fecal samples from stray and domiciled cats, using three distinct markers (B5-B6, 18S and 529bp RE). Oocysts of T. gondii/H. hammondi were detected in 15.4% by parasitology fecal tests (PFT), and 4% of these oocysts were positively identified as T. gondii by Copro-PCR. The presence of T. gondii genetic material was detected in 16.1%, but 12% of the samples that tested positive by Copro-PCR were negative in PFT. Samples with discordant results were subjected to a new Copro-PCR with 18S marker and a 529, and of the 17 samples, 9 contained T. gondii genetic material. A comparison of the PFT and the molecular methods showed the latter was more sensitive, since it detected 22.1% while the PFT detected 15.4%. Demonstrating the high sensitivity and specificity of the Copro-PCR, particularly with the association of primers (k=0.809), but also confirms the importance of using molecular techniques in laboratories, since Copro-PCR was able to detect samples considered negative by PFT.

Toxoplasma gondii infection in domestic and wild felids as public health concerns: a systematic review and meta-analysis

Felidae as definitive hosts for Toxoplasma gondii play a major role in transmission to all warm-blooded animals trough oocysts dissemination. Therefore the current comprehensive study was performed to determine the global status of T. gondii infection in domestic and wild felids aiming to provide comprehensive data of interest for further intervention approaching the One Health perspective. Different databases were searched by utilizing particular key words for publications related to T. gondii infecting domestic and wild feline host species, worldwide, from 1970 to 2020. The review of 337 reports showed that the seroprevalence of T. gondii in domestic cats and wild felids was estimated in 37.5% (95% CI 34.7-40.3) (I² = 98.3%, P < 0.001) and 64% (95% CI 60-67.9) (I² = 88%, P < 0.0001), respectively. The global pooled prevalence of oocysts in the fecal examined specimens from domestic cats was estimated in 2.6% (95% CI 1.9-3.3) (I² = 96.1%, P < 0.0001), and that in fecal samples from wild felids was estimated in 2.4% (95% CI 1.1-4.2) (I² = 86.4%, P < 0.0001). In addition, from 13,252 examined soil samples in 14 reviewed studies, the pooled occurrence of T. gondii oocysts was determined in 16.2% (95% CI 7.66-27.03%). The observed high rates of anti-T. gondii antibodies seroprevalence levels and oocyst excretion frequency in the felids, along with soil (environmental) contamination with oocysts may constitute a potential threat to animal and public health, and data will result of interest in further prophylaxis programs.

A real-time quantitative polymerase chain reaction for the specific detection of Hammondia hammondi and its differentiation from Toxoplasma gondii

Introduction

Hammondia hammondi and Toxoplasma gondii are closely related protozoan parasites, but only T. gondii is zoonotic. Both species use felids as definitive hosts and cannot be differentiated by oocyst morphology. In T. gondii, a 529-base pair (bp) repetitive element (TgREP-529) is of utmost diagnostic importance for polymerase chain reaction (PCR) diagnostic tests. We identified a similar repetitive region in the H. hammondi genome (HhamREP-529).

Methods

Based on reported sequences, primers and probes were selected in silico and optimal primer probe combinations were explored, also by including previously published primers. The analytical sensitivity was tested using serial dilutions of oocyst DNA. For testing analytical specificity, DNA isolated from several related species was used as controls. The newly established TaqMan PCR (Hham-qPCR1) was applied to tissues collected from H. hammondi-infected gamma-interferon gene knockout (GKO) mice at varying time points post-infection.

Results

Ten forward and six reverse primers were tested in varying combinations. Four potentially suitable dual-labelled probes were selected. One set based on the primer pair (Hham275F, Hham81R) and the probe (Hham222P) yielded optimal results. In addition to excellent analytic specificity, the assay revealed an analytical sensitivity of genome equivalents of less than one oocyst. Investigation of the tissue distribution in GKO mice revealed the presence of parasite DNA in all examined organs, but to a varying extent, suggesting 100- to 10,000-fold differences in parasitic loads between tissues in the chronic state of infection, 42 days post-infection.

Discussion

The use of the 529-bp repeat of H. hammondi is suitable for establishing a quantitative real-time PCR assay, because this repeat probably exists about 200 times in the genome of a single organism, like its counterpart in T. gondii. Although there were enough sequence data available, only a few of the primers predicted in silico revealed sufficient amplification; the identification of a suitable probe was also difficult. This is in accord with our previous observations on considerable variability in the 529-bp repetitive element of H. hammondi.

Conclusions

The H. hammondi real-time PCR represents an important novel diagnostic tool for epidemiological and cell biological studies on H. hammondi and related parasites.

Molecular Detection and Genetic Diversity of Toxoplasma gondii Oocysts in Cat Faeces from Klang Valley, Malaysia, Using B1 and REP Genes in 2018

The major route for Toxoplasma gondii (T. gondii) infection is through the ingestion of foods contaminated with oocyst from cat faeces. The microscopic detection of T. gondii oocysts in cat faeces is challenging, which contributes to the failure of detecting or differentiating it from other related coccidian parasites. This study aims to detect T. gondii oocysts in cat faeces using two multicopy-target PCR assays and to evaluate their genetic diversity. Cat faecal (200) samples were collected from pet cats (PCs; 100) and free-roaming cats (FRCs; 100) within Klang Valley, Malaysia, and screened for coccidian oocysts by microscopy using Sheather's sucrose floatation. PCR assays were performed on each faecal sample, targeting a B1 gene and a repetitive element (REP) gene to confirm T. gondii oocysts. Additionally, the PCR amplicons from the REP gene were sequenced to further confirm T. gondii-positive samples for phylogenetic analysis. Microscopy detected 7/200 (3.5%) T. gondii-like oocysts, while both the B1 gene and the REP gene detected 17/200 (8.5%) samples positive for T. gondii. All samples that were microscopically positive for T. gondii-like oocysts were also shown to be positive by both B1 and REP genes. The BLAST results sequenced for 16/200 (8.0%) PCR-positive T. gondii samples revealed homology and genetic heterogeneity with T. gondii strains in the GenBank, except for only one positive sample that did not show a result. There was almost perfect agreement (k = 0.145) between the two PCR assays targeting the B1 gene and the REP gene. This is the first report on microscopic, molecular detection and genetic diversity of T. gondii from cat faecal samples in Malaysia. In addition, the sensitivities of either the B1 gene or REP gene multicopy-target PCR assays are suitable for the accurate detection of T. gondii from cat faeces.

All about toxoplasmosis in cats: the last decade

Toxoplasma gondii infections are common in humans and animals worldwide. Toxoplasmosis continues to be of public health concern. Cats (domestic and wild felids) are the most important host in the epidemiology of toxoplasmosis because they are the only species that can excrete the environmentally resistant oocysts in feces. Cats can excrete millions of oocysts and a single cat can spread infection to many hosts. The present paper summarizes information on prevalence, persistence of infection, clinical signs, and diagnosis of T. gondii infections in domestic and wild cats for the past decade. Special emphasis is paid to genetic diversity of T. gondii isolates from cats. Review of literature indicates that a unique genotype (ToxoDB genotype #9 or Chinese 1) is widely prevalent in cats in China and it has been epidemiologically linked to outbreaks of clinical toxoplasmosis in pigs and deaths in humans in China; this genotype has rarely been detected in other countries. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Prevalence and genotyping of Toxoplasma gondii in stray cats in Mashhad area, Iran

BACKGROUND

Cats as a definitive host have an important role in the epidemiology of toxoplasmosis in humans and animals. The aim of the study was to determine the frequency of Toxoplasma gondii infection and isolate and identify the genotypes of T. gondii in stray cats in the Mashhad suburb.

METHODS

From April 2016 to August 2017, 175 fecal samples from stray cats and 31 brain samples from cats killed in driving accidents were collected. The fecal samples were examined by fecal flotation technique and T. gondii-specific PCR. The brain samples were investigated by T. gondii-specific PCR and consequently examined by mice bioassay. The DNA of T. gondii isolated was genotyped using SAG1, SAG2, SAG3, BTUB and GRA6 as PCR-restriction fragment length polymorphism (PCR-RFLP) markers.

RESULTS

In the present study, Toxoplasma-like oocysts were microscopically observed in 2.2% (4/175) fecal samples. The presence of Toxoplasma oocysts was confirmed in one microscopy-positive sample by PCR. In addition, T. gondii DNA was detected in 4% (7/175) microscopy-negative samples using PCR. T. gondii was isolated from one brain PCR-positive sample by mice bioassay. The isolate was avirulent and many T. gondii cysts were observed in mice brain. The isolate was successfully genotyped by PCR-RLFP analysis. The isolated genotyped was type II. Besides, eight Toxoplasma-positive fecal samples contained insufficient DNA and only amplified at SAG-3 locus in PCR. These samples were also showed type II pattern at this locus.

CONCLUSIONS

Parasitological and molecular results showed low frequency of Toxoplasma infection in the stray cats, and identified the genotype of T. gondii isolate as type II, for the first time in Mashhad area, Khorasan Razavi Province.

Environmental transmission of Toxoplasma gondii: Oocysts in water, soil and food

Toxoplasma gondii is a zoonotic protozoan parasite that can cause morbidity and mortality in humans, domestic animals, and terrestrial and aquatic wildlife. The environmentally robust oocyst stage of T. gondii is fundamentally critical to the parasite's success, both in terms of its worldwide distribution as well as the extensive range of infected intermediate hosts. Despite the limited definitive host species (domestic and wild felids), infections have been reported on every continent, and in terrestrial as well as aquatic environments. The remarkable resistance of the oocyst wall enables dissemination of T. gondii through watersheds and ecosystems, and long-term persistence in diverse foods such as shellfish and fresh produce. Here, we review the key attributes of oocyst biophysical properties that confer their ability to disseminate and survive in the environment, as well as the epidemiological dynamics of oocyst sources including domestic and wild felids. This manuscript further provides a comprehensive review of the pathways by which T. gondii oocysts can infect animals and people through the environment, including in contaminated foods, water or soil. We conclude by identifying critical control points for reducing risk of exposure to oocysts as well as opportunities for future synergies and new directions for research aimed at reducing the burden of oocyst-borne toxoplasmosis in humans, domestic animals, and wildlife.

Sequence variation in the B1 gene among Toxoplasma gondii isolates from swine and cats in Italy

The evaluation of the genetic variations of Toxoplasma gondii among isolates of a wide variety of animal hosts can provide significant information for better understanding the epidemiology and population structure of the parasite in different geographical areas. The aim of this study was to provide information on T. gondii genetic diversity in host species living in central Italy, which could act as a potential source of human infection. Seventy-seven feline faecal samples, and 36 and 20 diaphragm pillar tissue samples from pigs and wild boars were collected in Umbria (central Italy). The samples were tested by a nested-PCR protocol amplifying an informative region within the B1 gene, a multi-copy genetic target, showing a good rate of variability. Thirty-six specimens (27.07%) belonging to 10 pigs, 13 wild boars and 13 cats, tested positive to the B1 nested-PCR screening. Of these, 23 good quality sequences (8 from wild boars, 5 from pigs, and 10 from cats) were analyzed. A comparison of the B1 DNA sequences showed that a single homogeneous nucleotide substitution (C/T) was present at position 31 in the isolates from pigs and wild boars compared with the sampled cats and other hosts (including humans) available in GenBank™. The present results suggest the existence of a T. gondii genetic diversity for swine host species, based on a SNP (C/T) of the B1 gene. Further studies are needed to draw more solid conclusions on the discriminatory power of the B1 target by collecting more swine samples from much broader geographical areas.