Seroprevalence of Toxocara infection in middle-class and disadvantaged children in northern Spain (Gipuzkoa, Basque Country)

Urticaria and silent parasitism by Ascaridoidea: Component-resolved diagnosis reinforces the significance of this association

Urticaria remains a major problem in terms of aetiology, investigation, and management, and although parasitic diseases are considered potential causes, the absence of a consistent link between parasitic infections and skin allergy symptoms leads to the need for a deeper study of parameters that support this association. The objectives of this study were to analyse a possible relationship between parasitism by Ascarididae (Toxocara canis and Anisakis simplex) and the clinical expression of urticaria and to identify possible parasitic molecular markers for improving the diagnosis of unknown urticaria aetiology. The prevalence of Toxocara and Anisakis infestations was evaluated by measuring the levels of specific IgG (sIgG) and IgE (sIgE) antibodies against crude extracts and isolated components from whole larvae of Anisakis simplex (Ani s 1, Ani s 3 and Ani s 7) and Toxocara canis (TES-120, TES-70, TES-32 and TES-26) using immunologic and molecular diagnostic methods. A cross-sectional study was performed in a group of 400 individuals. The study group consisted of 95 patients diagnosed with urticaria (55 with chronic urticaria and 40 with acute urticaria). A control group consisted of 305 subjects without urticaria (182 diagnosed with respiratory allergy and 123 without allergy). Statistically significant differences were demonstrated in the seroprevalence of specific IgG and IgE antibodies between the urticaria patients and the healthy general population when isolated ascarid antigens were evaluated. The prevalence of IgG antibodies against Ani s 1, IgE antibodies against TES-120 and IgE antibodies against TES-70 were significantly different between the control individuals (healthy general population) and patients with urticaria. Moreover, the urticaria patient group demonstrated a higher seroprevalence of antibodies (sIgE and sIgG) against Anisakis simplex larva whole extract than the control group but just with statistically diferences when sIgE was evaluated. The presence of IgE and/or IgG antibodies against Ani s 3 (tropomyosin) can help to discriminate between patients with and without urticaria. Both ascarids seem to be associated with urticaria, although in our region, Anisakis seems to have greater involvement than Toxocara in this relationship. Molecular diagnostics can be used to associate urticaria with parasite infestations. Tropomyosin and Ani s 1 were the most relevant markers to demonstrate the association between urticaria and the most relevant Ascarididae parasites in our region.

Seroprevalence of human toxocarosis in Europe: A review and meta-analysis

Toxocarosis is distributed worldwide and represents the most prevalent zoonotic helminth infection in industrialized countries, thereby posing a substantial risk for public health. Thus, toxocarosis is one of CDC's Neglected Parasitic Infections that has been targeted for public health action. This systematic review and meta-analysis summarizes Toxocara seroprevalence in general populations from Europe, populations suspected of Toxocara infection and defined risk groups. Random-effects meta-analysis of proportions based on 41 publications resulted in an overall seroprevalence of 6.2% (95% CI: 4.7-8.3%) in the general population of Europe. Subgroup analysis according to decades (1970-2010s) revealed a significant increase in seroprevalence, with the highest value (12.4%; 95% CI: 6.5-22.3%) in the 2010s (χ²=17.87, df=4, P=0.001). There were no significant differences between pooled prevalence rates of European sub-regions (χ²=3.01, df=3, P=0.389). Furthermore, meta-analysis of seroprevalence according to age groups, based on data from 22 publications, indicated a significantly higher pooled seroprevalence of 14.9% (95% CI: 8.5-24.8%) in people more than 50 years of age than in younger age cohorts (χ²=8.33, df=2, P=0.016). Occupational groups exposed to contaminated soil and infected animals bear substantial risk for acquiring Toxocara infection. Due to the close link between animal infection and human Toxocara exposure, a "One Health" approach for the prevention of Toxocara infection in both humans and animals is required.

New insight into the diagnostic cut-off value of serum anti-Toxocara IgG for ocular toxocariasis in uveitis patients

Uveitis is one of the commonest causes of vision loss worldwide and its exact etiology is still not clarified in most patients. The current study is a trial to assess the efficacy of serum anti-Toxocara immunoglobulin G (IgG) by enzyme-linked immunosorbent assay (ELISA) as a diagnostic tool for ocular toxocariasis (OT) and to detect OT prevalence and the associated ocular manifestations in sera of patients with uveitis. One hundred and twelve patients (62 females and 50 males) with uveitis were diagnosed by ophthalmologists, radiologists and rheumatologists according to ocular manifestations, laboratory and radiological investigations. Serum anti-Toxocara IgG titers were determined by ELISA in sera of all patients. Our results revealed that OT is highly associated with intermediate and posterior uveitis. Children and young adult females, especially those residing in rural areas, complained mainly of diminution of vision in the left eye, with strabismus and leukocoria. At a cut-off value of 0.258, the sensitivity and specificity of IgG ELISA were 93.3% and 100%, respectively. In conclusion, at a novel cut-off value of 0.258 the serum anti-Toxocara IgG ELISA is predicted to be a diagnostic tool for OT regarding sensitivity and specificity. Also, it has potential importance in the interpretation and differential diagnosis of OT. Thus, serum anti-Toxocara IgG ELISA should be a routine test for screening of suspected cases.

Epidemiology of Toxocariasis in England and Wales

Toxocara infection occurs through ingestion of parasite eggs excreted by dogs and cats, and can cause severe morbidity. The burden of disease in England and Wales is not well described, and the impact of public health campaigns conducted in the mid-1990s is uncertain. This paper uses data from two extensive databases to explore the trends in this disease in England and Wales from the 1970s to 2009.

Helminthosis and eosinophilia in Spain (1990-2015)

The finding of blood eosinophilia in a patient is a relatively frequent reason to refer him/her to a Clinical Department of Infectious Diseases. The doctor usually intends to rule out a parasitic disease in the autochthonous population, travelers or immigrants. It is uncommon for an eosinophilia to be produced by protozoa infection, whereas helminth parasites are more frequently associated with an increase of eosinophil counts in the infected patient. Eosinophilia can be the only abnormal finding, or it could be part of more complex clinical manifestations suffered by the patient. Furthermore, many, but not all, helminth infections are associated with eosinophilia, and the eosinophil level (low, high) differs according to parasite stages, helminth species, and worm co-infections. The purpose of the present article is to carry out a systematic review of cases and case series on helminth infections and eosinophilia reported in Spain from 1990 to 2015, making a distinction between autochthonous and imported (immigrants and travelers) cases, and studying their relationship with immunodepression situations.

Seroprevalence and risk factors of Toxocara infection among children in Shandong and Jilin provinces, China

This cross-sectional study was aimed to investigate the Toxocara serology in children in Shandong and Jilin provinces, China using an enzyme-linked immunosorbent assay (ELISA). The overall Toxocara seroprevalence among the study population (n=1458) was 19.3%, sick children (26.4%) had significantly higher seroprevalence than clinically healthy children (14.4%) (P<0.05), and the highest Toxocara seroprevalence was found in children suffering from chronic cough (40.6%), followed by recurrent abdominal pain (40.0%), recurrent headache (38.1%), slight fever (36.2%), and recurrent vomiting (31.6%). Place of residence, education level, type of school, keeping dogs at home, contact with dogs and cats and exposure with soil were found to be associated with Toxocara infection. Our findings show that children infection with Toxocara is common in Shandong and Jilin provinces, eastern and northeastern China, indicating an immediate need for implementing strategies and measures to prevent and control Toxocara infection in children in China.

Study of Toxocara seroprevalence among patients with allergy and healthy individuals in Bulgaria

Data in the literature addressing the ability of Toxocara infection in humans to induce development of atopic disease are controversial. The aim of our study was to determine the seroprevalence of anti-Toxocara antibodies in three groups of people: subjects with allergic symptoms and presence of allergen-specific IgE, subjects with allergic symptoms and absence of allergen-specific IgE, and clinically healthy blood donors. Serum samples from all subjects were tested by ELISA and Western blot for presence of specific antibodies against Toxocara canis. The results of our study did not support the link between toxocariasis and allergic manifestations in atopic patients. Among subjects with allergic symptoms and absence of atopy was found seroprevalence of 2·2% in Western blot. Same index in patients with atopy was 0·8%, and in clinically healthy blood donors 4·0%. Our study gives us grounds to consider that it is appropriate persons with allergic reactions, without evidence of atopy to be tested for presence of anti-Toxocara antibodies in the course of their diagnostic evaluation. Data from clinically healthy persons suggest that there is a 'hidden' infection among the population, which is not clinically manifested.

Toxocariasis: seroprevalence in abandoned-institutionalized children and infants

Toxocariasis is an infection that has worldwide distribution. Toxocara canis is the most relevant agent due to its frequent occurrence in humans. Soil contamination with embryonated eggs is the primary source of T. canis. This study aimed to determine the seroprevalence of toxocariasis in 10-month to 3 year-old abandoned infants, considered to be at high risk because of their orphanhood status and early age. Blood samples were collected from 120 children institutionalized in an orphanage in the city of La Plata. In this study, we observed 38.33% of seropositive cases for T. canis by ELISA and 45% by Western blot techniques; significant differences among groups A (<1 year), B (1-2 years) and C (>2 years) were also found. In research group A, children presented a seropositivity rate of 23.91%, in group B of 42.85% and in group C of 56%, which indicates an increase in frequency as age advances, probably because of greater chances of contact with infective forms of the parasite since canines and soil are frequently infected with T. canis eggs. Abandoned children come from poor households, under highly unsanitary conditions resulting from inadequate or lack of water supply and sewer networks, and frequent promiscuity with canines, which promotes the occurrence of parasitic diseases. These children are highly vulnerable due to their orphanhood status and age.

Seroprevalence and modifiable risk factors for Toxocara spp. in Brazilian schoolchildren

BACKGROUND

Toxocariasis is a worldwide helminthic zoonosis caused by infection with the larvae of the ascarid worms that comprise the Toxocara spp. Children are particularly prone to infection because they are exposed to the eggs in sandboxes and playgrounds contaminated with dog and cat feces. Certain behaviors, such as a geophagy habit, poor personal hygiene, a lack of parental supervision, close contact with young dogs, and ingestion of raw meat, as well as gender, age, and socioeconomic status, affect the prevalence of the disease. However, previous studies of the risk factors for toxocariasis have generally produced inconsistent results. An epidemiological cross-sectional study was conducted to evaluate the seroprevalence of IgG anti-Toxocara spp. antibodies and associated factors in schoolchildren from a region in the southeast of Brazil.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 252 schoolchildren aged 1 to 12 years (120 males and 132 females) were assessed. An enzyme-linked immunosorbent assay based on Toxocara canis larval excretory-secretory antigens was used to determine outcomes. A questionnaire was used to collect information on children, family, and home characteristics. Clinical and laboratory data completed the dataset investigated in this study. Seroprevalence was 15.5% (95%CI 11.5-19.8). Geophagy (aPR 2.38 [95%CI 1.36-4.18], p-value 0.029) and the habit of hand washing before meals (aPR 0.04 [95%CI 0.01-0.11], p-value ≤ 0.001) were factors associated with increased and decreased seroprevalence, respectively. The income factor and its related variables lost statistical significance after adjustment with a multiple Poisson regression model.

CONCLUSIONS/SIGNIFICANCE

The current study confirms that toxocariasis is a public health problem in the evaluated area; modifiable factors such as soil contact and personal hygiene appear to have a greater influence on the acquisition of infection than sociodemographic attributes, thus representing direct targets for disease prevention and control.

An agent-based model of exposure to human toxocariasis: a multi-country validation

Seroprevalence data illustrate that human exposure to Toxocara is frequent. Environmental contamination with Toxocara spp. eggs is assumed to be the best indicator of human exposure, but increased risk of exposure has also been associated with many other factors. Reported associations are inconsistent, however, and there is still ambiguity regarding the factors driving the onset of Toxocara antibody positivity. The objective of this work was to assess the validity of our current conceptual understanding of the key processes driving human exposure to Toxocara. We constructed an agent-based model predicting Toxocara antibody positivity (as a measure of exposure) in children. Exposure was assumed to depend on the joint probability of 3 parameters: (1) environmental contamination with Toxocara spp. eggs, (2) larvation of these eggs and (3) the age-related contact with these eggs. This joint probability was linked to processes of acquired humoral immunity, influencing the rate of antibody seroreversion. The results of the simulation were validated against published data from 5 different geographical settings. Using simple rules and a stochastic approach with parameter estimates derived from the respective contexts, plausible serological patterns emerged from the model in nearly all settings. Our approach leads to novel insights in the transmission dynamics of Toxocara.

Laboratory diagnosis of human toxocariasis

Toxocariasis is a helminth zoonosis caused by infection with the larvae of Toxocara spp. ascarid worms. Only two species, Toxocara canis and Toxocara cati, are recognised as causative agents of human disease. The best choice for serodiagnosis of the generalised forms of toxocariasis, visceral larva migrans (VLM) or covert toxocariasis, relies upon the initial use of TES-ELISA, after which any positive result should subsequently be tested by Western blotting (WB). Covert toxocariasis is mostly a benign infection, so a large majority of infected subjects are asymptomatic or have very few symptoms and therefore go undiagnosed. In this form, this helminthosis is often self-limiting, leaving residual specific antibodies. A positive serodiagnosis caused by residual antibodies that do not have any diagnostic significance can be associated with any infectious or non-infectious disease. If separated from the ongoing clinical and laboratory context, such a positive result has no diagnostic value and should be only taken into account after the possible etiologies of any observed syndromes have been ruled out. Unlike the methods used for the immunodiagnosis of bacterial, viral or protozoal (toxoplasmosis) infections, it is not possible with toxocariasis to assess the age of the presence of specific IgG using the levels of specific IgM because IgM antibodies can be found throughout the course of helminthiasis. The detection of other classes of immunoglobulins, namely IgE and IgA, the subclasses, namely IgG4 or circulating Ag was proven to be unable to discriminate between active and self-cured generalised toxocaral infections. Currently, the diagnosis of an active covert toxocariasis relies upon indirect arguments, e.g., the presence of otherwise unexplained symptoms along with blood eosinophilia and/or elevated levels of eosinophil cationic protein (ECP). This situation is far from ideal and more research should be carried out to solve this difficult problem.

Developmental age, physical fitness andToxocaraseroprevalence amongst lower-secondary students living in rural areas contaminated withToxocaraeggs

Scarce and inconclusive information on general biological impact ofToxocarainvasion on paratenic hosts, and people in particular, has led us to undertake a comprehensive study of the problem. The study has been conducted in a rural environment, which is considered a toxocarosis risk factor. In total 200 soil samples have been screened forToxocaraeggs by flotation, of which 14·5% were positive. Backyards close to households were most heavily contaminated with infectious eggs – 21·7% of positive samples. ELISA serological tests performed on 242 lower-secondary students found 14·5% of the studied population to be definitely positive – 16·5% of boys and 12·8% of girls, respectively. The odds of being infected withToxocarawere 2 times (CI: 1·15–3·85) more likely for individuals who owned a cat than those who did not own a cat. Strong significant correlation between seropositivity and the presence of a dog in a household was found with boys. The level of developmental age was significantly higher in seropositive than in seronegative students. No significant correlation has been observed between the motor abilities and seropositivity of students. Seropositive boys had significantly lower end-of-year grades than their seronegative counterparts.

Seroprevalence of Toxocara canis infection among asymptomatic children with eosinophilia in Croatia

A total of 142 serum specimens from Croatian children aged 3-18 years, with peripheral eosinophilia and without any clinical symptoms, were tested for the presence of Toxocara canis IgG antibodies using an enzyme-linked immunosorbent assay (ELISA) and Western blot method. The overall T. canis seropositivity rate in the samples tested was 31%. There was no statistical difference in the seroprevalence rate between boys (32.1%) and girls (29.7%, chi2 = 0.092, P = 0.761). The T. canis seropositivity varied significantly between age groups both in boys (Fisher's test P < 0.001) and girls (Fisher's test P = 0.007). The highest seroprevalence rate was found in boys aged 11-14 (42.9%) and girls aged 7-10 (44.2%). Our results showed a high seroprevalence rate of T. canis infection among children with eosinophilia. It is important that testing for toxocariasis should be included in a differential diagnosis of eosinophilia, especially in children.

A serological and epidemiological evaluation of risk factors for toxocariasis in children in central Poland

The level of specific anti-Toxocara IgG was examined in 343 children from central Poland with suspected Toxocara infection. Based on the presence of specific IgG antibodies and clinical signs and symptoms, toxocariasis was confirmed in 249 patients. The serological results of diagnosed cases were analysed in connection with epidemiological data (contamination of soil around the children's homes and presence of a dog or a cat). A higher prevalence of soil contamination with Toxocara eggs was found in suburban and rural areas (30.9% and 24.6%, respectively) whereas it was lower in urban areas (10.3%). In about 40% of the children whose households were not contaminated, a decrease in the antibody level was observed 2 years after treatment for toxocariasis, while there was no such decline in those living in contaminated places. The logistic regression model employed to determine the correlation between seropositivity in the children and selected epidemiological risk factors showed a statistically significant relationship in connection only with dog ownership (P = 0.0238). The present results have demonstrated the high risk of toxocariasis for children from rural and suburban areas in Poland. The sero-epidemiological investigations indicated that re-infection might be the reason for persistence of seropositivity after treatment.

A putative role for Toxocara species in the aetiology of multiple sclerosis

Multiple sclerosis (MS) is a disease of unknown aetiology. The finding of monoclonal antibodies in MS has been attributed to various infectious agents. Nematodes, such as Toxocara species have not been explored as possible aetiologic agents of MS. Some epidemiological studies have found an association between exposure to stress and household pets prior to the diagnosis of MS. In a case known to the authors, slight malaise and eosinophilia in peripheral blood preceded the diagnosis of MS by one year in a middle-aged man who lived in rural surroundings with cats in the household. The ubiquitary parasite Toxocara catis or canis is prevalent and serum antibodies are found regularly in populations examined. It is able to develop into the larval stage in human beings. The hypothesis presented here is that MS could be initiated by such infections in previously unexposed subjects under conditions of long-term stress.

Human toxocariasis: incidence among residents in the outskirts of Campinas, State of São Paulo, Brazil

With the aim of estimating the incidence of infection by Toxocara among residents in the outskirts of Campinas (State of São Paulo, Brazil) two serological surveys, using ELISA anti-Toxocara tests, were performed in January 1999 and January 2000, involving, respectively, 138 and 115 individuals, 75 of which examined in both occasions. Among this group 67 individuals did not show the presence of anti-Toxocara antibodies in 1999, and 12 presented seroconversion in the second survey, revealing an annual incidence rate of 17.9%.

Human toxocariasis: a seroepidemiological survey in the municipality of Campinas (SP), Brazil

The occurrence of human Toxocara infection was evaluated in three neighborhoods of the periphery of the Campinas municipality (Jardim Santa Mônica, Jardim São Marcos and Jardim Campineiro) in 1999. Forty residences and 138 residents were randomly selected by drawing lots and were submitted to a seroepidemiological survey, which included blood collection for the immunoenzymatic detection (ELISA) of anti-Toxocara antibodies and a blood count, and the application of a semi-structured questionnaire for the evaluation of epidemiological data. Significant levels of anti-Toxocara antibodies were detected in 23.9% of the 1999 samples. No significant difference in the frequency of infection according to age was observed. Environmental contamination with Toxocara eggs was observed in 12.3 and 14.0% of 57 soil samples collected in the same region in December 1998 and July 1999, respectively. Univariate analysis and multiple logistic regression of the data obtained from the questionnaires and of the results of the serological tests, suggest a significant influence of socioeconomic variables on the frequency of human infection with Toxocara under the conditions prevalent in the study area.

Increased serum IgE in alcoholics: relationship with Th1/Th2 cytokine production by stimulated blood mononuclear cells

BACKGROUND

Increased serum immunoglobulin (Ig) E values are frequently found in alcoholics. Cytokines produced by T-helper-2 (Th2) lymphocytes are required for IgE synthesis. Chronic alcoholism is associated with altered cytokine balance. This study analyzed the relationship between Th1 and Th2 cytokine production by stimulated peripheral blood mononuclear cells (PBMCs) and serum IgE levels, both in atopic and nonatopic alcoholics.

METHODS

Twenty-five patients admitted to the hospital with alcohol withdrawal syndrome were included in the study. Five were classified as atopic and 20 as nonatopic by means of skin-prick tests. Interleukin-4 (IL-4), IL-10, IL-12, IL-13, and interferon gamma were measured in the supernatants of 48-hr cultures of PBMCs stimulated with phytohemagglutinin. Total serum IgE was measured by chemiluminescent enzyme immunoassay. Results were compared with those of 15 healthy controls (seven atopics and eight nonatopics).

RESULTS

Total serum IgE concentrations were higher in alcoholics than in controls, in both atopic and nonatopic subjects. The ratio of IL-4 to interferon gamma production by phytohemagglutinin-stimulated PBMCs (as an approach to Th2/Th1 balance) was significantly lower in alcoholics than in healthy controls, both in the atopic and in the nonatopic group. No difference was observed regarding IL-10, IL-12, and IL-13 production between alcoholics and controls. No correlation was demonstrated between cytokine production and total serum IgE levels in any group.

CONCLUSIONS

Increased total serum IgE is observed in alcoholics together with a paradoxically low ratio of Th2 to Th1 cytokine production by phytohemagglutinin-stimulated PBMCs. These findings are independent of the atopic status of patients.

Toxocarosis as zoonosis. A review of literature and the prevalence of Toxocara canis antibodies in 511 serum samples

A total of 511 serum samples from children aged between 6 months to 15 years old, with different clinical signs-living in the region of Northern Greece - were tested by ELISA (enzyme links immunosorbent assay) technique, for the detection of specific IgG and IgM antibodies against T. canis antigen. The reason IgM was detected was because IgM levels are elevated in the acute phase of toxocara infection, in spite of their notorious non-specificity. In this seroepidemiologic survey of children, a remarkably high percentage (12.5&#x0025;) reacted positively to this method. Sixteen (3.1&#x0025;) out of 511 sera showed IgG antibodies, 43 (8.4&#x0025;) showed IgM, while 5 (1&#x0025;) showed both IgG and IgM antibodies against T. canis E/S (excretory - secretory) antigen. Females were significantly more infected than males. Seropositivity rate was highest in children over the age of 10.