Aggravation of symptom severity in adult attention-deficit/hyperactivity disorder by latent Toxoplasma gondii infection: a case-control study

The impact of Toxocara-seropositivity on attention and motor skills in children with attention-deficit hyperactivity disorder

BACKGROUND

The study aims to compare neurological soft signs and executive functions between Toxocara-seropositive and seronegative groups in children with attention-deficit/hyperactivity disorder.

METHODS

The study included 60 boys with ADHD, aged 7-12. After blood samples were taken, the Stroop Color Word Test and Judgment of Line Orientation test (JLOT) were implemented to measure executive functions. Neurological soft signs were evaluated with Physical and Neurological Examination for Subtle Signs (PANESS).

RESULTS

Serological tests were positive for Toxocara antibodies in 20 cases. There was no significant difference between Toxocara seropositive and seronegative regarding age, socioeconomic status, developmental stages, and ADHD severity. However, Toxocara-seropositive children had higher Stroop time and Stroop interference scores and lower JLOT scores than Toxocara-seronegative children. Furthermore, Toxocara-seropositive children exhibited more neurological soft signs, such as gait and station abnormalities, dysrhythmia, and a longer total time in timed movements compared to Toxocara-seronegative children.

CONCLUSION

Our study indicates a link between Toxocara-seropositivity and impaired neurological soft signs and executive functions in ADHD. Further research is needed to understand ADHD mechanisms, develop practical treatments considering immunological factors, and thoroughly evaluate how Toxocara seropositivity affects executive functions and motor skills in children with ADHD.

Parasitic infections as potential risk factors for attention deficit hyperactivity disorder (ADHD) in children

Attention deficit hyperactivity disorder (ADHD) represents a mysterious neuropsychiatric alarming concern due to indefinite etiopathogenesis among children. Notably, the studies which investigated the correlation between ADHD and parasitic infections are insufficient. Therefore, this research aimed to assess the correlation between ADHD and some tissue dwelling and intestinal parasitic infections in children. The study was conducted on 200 children, including 100 children suffering from ADHD (Group I) and 100 healthy children as a control group (Group II). All caregivers fulfilled predesigned sociodemographic form and Conners parent rating scale (CPRS-48) questionnaire. Blood samples were collected to determine hemoglobin level as well as relative eosinophilic count. The presence of anti-Toxoplasma IgG and anti-Toxocara IgG in serum by Enzyme-Linked Immunosorbent Assay (ELISA) was further investigated. Also, micronutrients as zinc, iron, and copper levels were measured. Schistosoma antigen was investigated in urine samples. Stool samples were subjected to direct wet smear, concentration technique and modified Ziehl-Neelsen (MZN) staining for coccidian parasites detection. Cryptosporidium parvum, Giardia lamblia and Entamoeba histolytica antigens were investigated in stool samples. Group I expressed more liability to sociodemographic risk factors, decreased levels of Hb, iron, zinc, and copper with statistically significant difference (P < 0.001). Comparison between Group I and Group II regarding the detected parasitic infections exhibited statistically significant difference except Schistosoma antigen positivity which expressed no statistical significance. The present study concluded that the parasitic infections with their consequences are potential risk factors in children with ADHD indicating that their early diagnosis and treatment may help in ADHD prevention.

Screening of Toxoplasmosis in Owned and Stray Dogs of District Faisalabad, Pakistan through Latex Agglutination and Indirect ELISA

INTRODUCTION

Toxoplasma gondii (an intracellular protozoan) causes toxoplasmosis in warm-blooded animals, including humans and dogs. The present study was carried out to investigate the seroprevalence of canine toxoplasmosis in the owned and stray populations of dogs in Faisalabad District, Punjab, Pakistan.

MATERIALS AND METHODS

Commercially available Latex Agglutination Test (LAT) kits were used for the screening of samples (139 stray and 150 owned), followed by confirmation through ELISA. For the statistical analyses, chi-square was used to correlate the prevalence of toxoplasmosis with various factors.

RESULTS

The overall prevalence of toxoplasmosis, determined by the LAT, was 22.5% and, by ELISA, was 21.8%. A nonsignificant association of toxoplasmosis was determined among owned and stray dogs. Among owned dog breeds, Bulldogs showed 28.30% prevalence, and among stray dogs, the highest prevalence was determined in Bhakarwal dogs (39.29%). Young and female dogs showed a slightly higher prevalence of toxoplasmosis than adults and males, respectively.

CONCLUSIONS

The present study determined by LAT and ELISA in owned dogs showed the same results, while a little variation was found in the stray dogs. It is concluded that both owned and stray dogs are infected with toxoplasmosis in Faisalabad District, and based on this, it is recommended that province-wide epidemiological studies be carried out to examine the prevalence of Toxoplasma and develop policies in order to control toxoplasmosis.

Seroprevalence and Genetic Characterization of Toxoplasma gondii among Children with Neurodevelopmental Disorders in Egypt

Toxoplasma gondii is a parasite with a special predilection for the central nervous system. Toxoplasmosis's contribution to the triggering of many neurodevelopmental disorders was established. This study aimed to detect the seroprevalence and genotypes of T. gondii strains in children with neurodevelopmental disorders. The study included 180 children with neurodevelopmental disorders and 180 children in the control group. Assessment of seropositivity of Toxoplasma IgM and IgG antibodies in patients and controls was carried out. Genetic characterization of T. gondii was obtained by nested polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) technique targeting dense granule gene (GRA6). Our results showed that the overall seroprevalence of T. gondii antibodies in the patient and controls was 35.6% and 11.7%, respectively. Nested PCR showed positivity in 11.1% of the patient group for T. gondii DNA. T. gondii seropositivity rate was significantly high in patients with hydrocephalus and also in patients with epilepsy. Positive nested PCR was significantly high in children with hydrocephalus only. Genotyping using nested PCR-RFLP showed genotype I (80%) followed by atypical strains (20%) with no association with any specific clinical presentation. In conclusion, among toxoplasmosis-positive children with neurodevelopmental disorders, analysis of T. gondii GRA6 locus revealed the predominance of type I genotype followed by atypical strains.

Molecular Characterization of Toxoplasma gondii in Cats and Its Zoonotic Potential for Public Health Significance

Toxoplasmosis is a globally distributed disease of warm-blooded animals. It is caused by the opportunistic parasite Toxoplasma gondii (T. gondii). One-third of the global human population is believed to be infected with T. gondii. Cats serve as final host of T. gondii and are the main source of contamination of soil and water. This study aimed to detect genotypes of T. gondii in cats. Fecal samples (n = 400) were collected from districts of South Punjab (Khanewal and Sahiwal), and were processed by polymerase chain reaction (PCR) followed by sequencing and phylogenetic analysis. The obtained oligonucleotide sequences (T. gondii) were submitted to the GenBank database, and the evolutionary tree was constructed using MEGA-X software. Seven fecal samples (3.5%) from cats were positive. Five out of thirteen fecal samples (38.46%) found to be positive for T. gondii with microscopy were confirmed by PCR. After phylogenetic analysis with 3 clonal types and atypical strains, isolates of T. gondii in current study were more closely linked to a typical strain (AF249696). Besides genotyping from cats, seroprevalence from humans and ruminants is still considered to be the best and easiest way to identify the Toxoplasma. Blood samples were collected from sheep and goats (n = 2000 each), and human blood samples (n = 400) were collected from the same vicinity. Seroprevalence was determined using a commercial enzyme-linked immunosorbent assay (ELISA) kit. In Khanewal, the blood samples of 292 goats (29.2%) and 265 sheep (26.5%), and 6 fecal samples from cats (3%) were positive. Out of 200 human blood samples, 52 were positive, with a seroprevalence of 26%. In the Sahiwal district, the blood samples from 49 humans, 235 sheep and 348 goats were positive, with seroprevalence of 24.5%, 23.5% and 34.8%, respectively. The present study revealed the current circulating genotype of T. gondii from cats in the districts Khanewal and Sahiwal and the seroprevalence of the organism in small ruminants and humans living in the same vicinity. Further genotype analyses of the organism from ruminants and humans are needed.

Association of Toxoplasma gondii Seropositivity With Cognitive Function in Healthy People: A Systematic Review and Meta-analysis

IMPORTANCE

The parasite Toxoplasma gondii has been associated with behavioral alterations and psychiatric disorders. Studies investigating neurocognition in people with T gondii infection have reported varying results. To systematically analyze these findings, a meta-analysis evaluating cognitive function in healthy people with and without T gondii seropositivity is needed.

OBJECTIVE

To assess whether and to what extent T gondii seropositivity is associated with cognitive function in otherwise healthy people.

DATA SOURCES

A systematic search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline. A systematic search of PubMed, MEDLINE, Web of Science, PsycInfo, and Embase was performed to identify studies from database inception to June 7, 2019, that analyzed cognitive function among healthy participants with available data on T gondii seropositivity. Search terms included toxoplasmosis, neurotoxoplasmosis, Toxoplasma gondii, cognition disorder, neuropsychological, and psychomotor performance.

STUDY SELECTION

Studies that performed cognitive assessment and analyzed T gondii seroprevalence among otherwise healthy participants were included.

DATA EXTRACTION AND SYNTHESIS

Two researchers independently extracted data from published articles; if needed, authors were contacted to provide additional data. Quantitative syntheses were performed in predefined cognitive domains when 4 independent data sets per domain were available. Study quality, heterogeneity, and publication bias were assessed.

MAIN OUTCOMES AND MEASURES

Performance on neuropsychological tests measuring cognitive function.

RESULTS

The systematic search yielded 1954 records. After removal of 533 duplicates, an additional 1363 records were excluded based on a review of titles and abstracts. A total of 58 full-text articles were assessed for eligibility (including reference list screening); 45 articles were excluded because they lacked important data or did not meet study inclusion or reference list criteria. The remaining 13 studies comprising 13 289 healthy participants (mean [SD] age, 46.7 [16.0] years; 6586 men [49.6%]) with and without T gondii seropositivity were included in the meta-analysis. Participants without T gondii seropositivity had favorable functioning in 4 cognitive domains: processing speed (standardized mean difference [SMD], 0.12; 95% CI, 0.05-0.19; P = .001), working memory (SMD, 0.16; 95% CI, 0.06-0.26; P = .002), short-term verbal memory (SMD, 0.18; 95% CI, 0.09-0.27; P < .001), and executive functioning (SMD, 0.15; 95% CI, 0.01-0.28; P = .03). A meta-regression analysis found a significant association between older age and executive functioning (Q = 6.17; P = .01). Little suggestion of publication bias was detected.

CONCLUSIONS AND RELEVANCE

The study's findings suggested that T gondii seropositivity was associated with mild cognitive impairment in several cognitive domains. Although effect sizes were small, given the ubiquitous prevalence of this infection globally, the association with cognitive impairment could imply a considerable adverse effect at the population level. Further research is warranted to investigate the underlying mechanisms of this association.