Sero-epidemiology of Toxocara canis infection among aboriginal schoolchildren in the mountainous areas of north-eastern Taiwan

Prevalence of antibodies to Toxocara canis and its associated risk factors in socio-economically deprived nomadic communities of Pakistan

Toxocariasis is an important zoonotic disease caused by Toxocara (T.) canis with considerably higher prevalence in developing countries. The data on its epidemiology, especially in socioeconomically deprived nomadic communities, are scarce in Pakistan. Therefore, this study was conducted to determine the prevalence of anti-T. canis antibodies and its associated risk factors in nomadic communities located in and around Multan, Pakistan. A total of 184 sera samples were collected from nomadic communities by simple random sampling technique. The descriptive epidemiological data of participants were collected on well-designed questionnaires. Prior consent was also obtained from the participants to use the data generated from their samples without showing their identity. All the samples were analysed for the detection of anti-T. canis antibodies using commercially available Enzyme-Linked-Immunosorbent-Assay (ELISA) kits having 91% sensitivity and 96% specificity (Bordier Affinity Products, Switzerland). The overall seroprevalence of toxocariasis among nomadic communities was 27.7% (51/184). Various factors, including age, known disease history, nutritional status, contact with dogs, practice of hand washing after contact with dogs, use of unwashed vegetables, body mass index, and drug abuse, showed significant correlation (p < 0.05) with toxocariasis in nomadic communities. Conversely, other factors, including gender, marital status, educational status, awareness about zoonotic diseases, source of drinking water, occupation, location, hand washing before taking food, exposure to soil, and hygienic eating behaviour, showed non-significant correlation (p > 0.05) with seroprevalence of toxocariasis. Results also showed that >50% of seropositive cases were asymptomatic, whereas cough and abdominal pain were recorded in 19.6% and 11.76% of seropositive cases, respectively. Keeping in view, it is suggested to conduct surveys at mass level to rule out the exact disease status at national level and to include nomadic communities in local, national, and regional disease control programs through provision of better healthcare facilities and awareness about the disease.

One health approach to toxocariasis in Brazilian indigenous populations, their dogs, and soil contamination

Introduction

Although socioeconomic vulnerability and lifestyle factors may contribute to the transmission of Toxocara spp., no study has investigated indigenous populations in Brazil using the One Health approach.

Methods

Accordingly, this study assessed anti-Toxocara spp. antibodies in Brazilian indigenous people and healthcare professionals by enzyme-linked immunosorbent assay. Presence of Toxocara spp. eggs (feces and hair) in dogs as definitive hosts and in soil samples of the indigenous communities were also recovered and molecularly investigated.

Results

Overall, 342/463 (73.9%) indigenous individuals and 46/147 (31.3%) non-indigenous healthcare professionals were seropositive for Toxocara spp. In addition, T. canis eggs were retrieved from 9/194 (4.6%) dog fecal samples and 4/204 (2.0%) dog hair samples, mainly from the Paraná State communities (3/42; 7.1%). Soil contamination was observed only in the Paraná State communities (36/90; 40.0%), with the molecular detection of T. canis. River water consumption was also associated with indigenous seropositivity (Odds ratio, 11.4).

Discussion

Indigenous individuals in Paraná State communities were 2.72-fold more likely to be seropositive than those in São Paulo State, likely due to a lack of sanitary infrastructure. In this scenario, a primarily soil-transmitted disease may also have become waterborne, with embryonated eggs probably spread to water supplies by rain. Full-time healthcare professionals in daily contact with indigenous communities were 9.2-fold more likely to be seropositive than professionals who visited sporadically, suggesting exposure to Toxocara spp. during their work and raising health concerns. In addition, the findings herein showed a significantly higher seroprevalence in indigenous people than in healthcare workers (χ2 = 85.5; p < 0.0001), likely due to overtime exposure to Toxocara spp. In conclusion, Brazilian indigenous communities are highly exposed to toxocariasis, with poor infrastructure and contact with contaminated river water as associated risk factors and a higher risk of infection in healthcare professionals working full-time in these communities.

Seroprevalence of anti-Toxocara canis antibodies and associated risk factors among dog owners in the rural community of Nakhon Si Thammarat province, southern Thailand

Background

Human toxocariasis is a zoonotic parasitic disease caused by the Toxocara canis and T. cati nematodes larvae. Dog owners are at a higher risk of acquiring T. canis infection, and there is no available evidence regarding the seroprevalence of T. canis infection among dog owners in Thailand. Therefore, this study aimed to investigate the seroprevalence of T. canis infection and associated risk factors among dog owners in rural areas of Thailand.

Methods

A total of 132 dog owners, including 25 men and 107 women, were recruited for this study. Serum anti-T. canis IgG antibodies were detected using a commercial enzyme-linked immunosorbent assay (ELISA) kit, and information on risk factors was collected using a questionnaire. In addition, hematological parameters were analyzed by the auto hematology analyzer. Risk variables associated with T. canis infection were investigated using univariate and multivariate logistic regression models.

Results

The overall seroprevalence of T. canis was 76.5% (101/132). Men were more likely to be infected with T. canis than women. Univariate analysis revealed that dog owners who did not practice handwashing before meals (p = 0.005) or after contact with soil (p = 0.035) or dogs (p = 0.049) had a substantially higher risk of acquiring T. canis infection. After adjusting for confounders, not practicing handwashing before meals remained a significant risk factor for T. canis infection (p = 0.038). The mean number of eosinophils was significantly higher in the seropositive group than in the seronegative group.

Conclusions

This is the first serological report of T. canis infection among dog owners reflecting the high rate of T. canis seropositivity in rural areas of southern Thailand. This study also provides group-specific data concerning modifiable risk behaviors for more effective T. canis infection control and prevention strategies in Thailand.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41182-022-00425-4.

The first two cases of neurotoxocariasis in Taiwan

Toxocariasis is a zoonosis disease with high sero-prevalence in Southeast Asian. Neurotoxocariasis has never been reported in Taiwan. Herein, we presented 2 cases of neurotoxocariasis. The first case is a 48-year-old man with febrile headache, rapid progressive cognitive problems and later thoracic myelitis. Meningeal enhancements on the corresponding sites were found on magnetic resonance imaging (MRI). Eosinophilic pleocytosis was present in peripheral blood and cerebrospinal fluid (CSF). A positive Toxocara canis larval excretory-secretory antigen (TcES)-based immunoblotting test for CSF confirmed the diagnosis. The second case is a 42-year-old woman of progressive headache with features of increased intracranial pressure. CSF analysis showed lymphocytic pleocytosis initially and eosinophilic pleocytosis later. Her brain MRI was normal. The diagnosis was confirmed by the presence of anti-TcES IgG in CSF. The two cases were soonly cured by mebendazole. Neurotoxocariasis presented a broad spectrum of neurological symptoms and the CSF profile can be non-eosinophilic pleocytosis. The prevalence of neurotoxocariasis may be seriously underestimated due to low awareness of physicians and lack of standard conventional diagnostic test in Taiwan. The two cases of neurotoxocariasis firstly reported in Taiwan will raise physician's awareness in recognizing this curable disease particularly in managing patients with aseptic meningitis or meningoencephalitis of undetermined pathogen.

Seroprevalence of Toxocara spp. infection in Southeast Asia and Taiwan

Human toxocariasis is a worldwide neglected zoonotic parasitic disease and caused mainly by Toxocara canis, and to a lesser event, by T. cati. There are only 16 epidemiological studies and 5 clinical toxocariasis case reports in 11 Southeast Asia countries and Taiwan (SEAT) that were found by searching data from PubMed in the period from January 1992 to August 2019. The overall seroprevalence in SEAT varied from 3.9% to 84.6% chiefly detected by using T. canis larval excretory-secretory antigen (TcES)-based ELISA. Playing with dogs or contacting Toxocara eggs from the contaminated soil or vegetables or eating raw meats/viscera containing encapsulated larvae seem likely the major risk factors leading to human toxocariasis in SEAT. Nevertheless, undertaking comprehensive seroepidemiological studies to establish the baseline data and beware of clinical toxocariasis cases by physicians as well as establishing adequate serodiagnostic methods in detection of Toxocara infection, e.g., TcES-based immunoblotting method in helminth endemic SEA are strongly required.

Seroprevalence of Toxocara canis infection and associated risk factors among primary schoolchildren in rural Southern Thailand

BACKGROUND

Human toxocariasis is a parasitic zoonosis caused by a parasite in the genus Toxocara and is transmitted mainly by the accidental ingestion of embryonated Toxocara canis (dog roundworm) or T. cati (cat roundworm) eggs. Several studies reported that children were the main population at risk for T. canis infection. Currently, no reports on the seroprevalence of T. canis infection in Thailand are available, and its status remains unknown among children who live in rural areas of southern Thailand.

OBJECTIVE

This study aimed to investigate the seroprevalence of T. canis infection and its associated risk factors among primary schoolchildren in rural areas of Nakhon Si Thammarat Province, Thailand.

METHODS

A total of 177 schoolchildren between 6 and 13 years of age were recruited between June and July 2019. Serum anti-T. canis IgG antibodies were detected with a commercial ELISA kit. A questionnaire administered by direct interviews was used to collect demographic and behavioral risk factor data.

RESULTS

The overall seroprevalence of T. canis infection was 58.2% (103 of 177). The univariate analysis revealed that schoolchildren who did not practice handwashing before a meal (crude odds ratio (COR) = 3.67, 95% CI 1.93-6.95, P < 0.001), did not practice hand washing after animal contact (COR = 2.89, 95% CI 1.53-5.47, P = 0.001), and drank untreated water (COR = 1.87, 95% CI 1.00-3.48, P = 0.049) had an increased risk of acquiring T. canis infection. However, after adjusting for confounders, only a lack of handwashing before a meal remained a significant risk factor (adjusted odds ratio (AOR) = 2.20, 95% CI 1.11-4.34, P = 0.023). Age, sex, owning a dog, and eating fresh vegetables were not significantly associated with T. canis infection in the current study.

CONCLUSIONS

This is the first serological investigation of T. canis infection among schoolchildren in Thailand. The high rate of Toxocara seropositivity reflected high levels of exposure to T. canis among schoolchildren in rural areas of southern Thailand. The results also provide baseline data regarding modifiable risk behaviors for effective T. canis infection prevention strategies in southern Thailand, especially strengthening hand washing practices among schoolchildren.

Frequency of Toxocariasis among Patients Clinically Suspected to Have Visceral Toxocariasis: A Retrospective Descriptive Study in Sri Lanka

Introduction

Human toxocariasis is caused by several species of the nematode Toxocara. Two common clinical syndromes are ocular and visceral larva migrans.

Objectives

To determine the Toxocara antibody positivity in clinically suspected VLM patients and to describe demographic factors and clinical manifestations of seropositive patients.

Methods

522 clinically suspected patients were studied between 1993 and 2014. Relevant data was gathered from referral letters. Serum samples were subjected to Toxocara antigen ELISA.

Results

Overall, seropositivity was 50.2% (262), of which 109 (40.8%) were positive at high level of Toxocara antibody carriage and 153 (58.4%) were positive at low levels. The seropositives ranged from 3 months to 70 years (mean = 7.8). Younger age group had higher levels of seropositivity and it was statistically significant. Majority of children under 5 years were seropositive (47.7%, n = 125). Seropositivity was common in males (55.3%, n = 145). Clinical manifestations of seropositives include lymphadenopathy (24.1%) skin rash (22.5%), dyspnoea (21.7%), fever (21%), hepatosplenomegaly (9.2%), and abdominal pain (3.8%). 197 (75.2%) seropositive cases had eosinophilia. These symptoms were not statistically significant.

Conclusions

This study confirms toxocariasis as an important cause of childhood ill health identifying common clinical symptoms recommending preventive measures to limit transmission.

Field evaluation of a rapid diagnostic test to detect antibodies in human toxocariasis

Human toxocariasis which is caused mainly by the larvae of Toxocara canis and Toxocara cati, is a worldwide zoonotic disease that can be a potentially serious human infection. The enzyme-linked immunosorbent assay (ELISA) using T. canis excretory-secretory (TES) antigens harvested from T. canis larvae is currently the serological test for confirming toxocariasis. An alternative to producing large amounts of Toxocara TES and improved diagnosis for toxocariasis is through the development of highly specific recombinant antigens such as the T. canis second stage larva excretory-secretory 30 kDa protein (recTES-30). The aim of this study was to evaluate the sensitivity and specificity of a rapid diagnostic kit (RDT, named as iToxocara kit) in comparison to recTES-30 ELISA in Serendah Orang Asli village in Selangor, Malaysia. A total of 133 subjects were included in the study. The overall prevalence rates by ELISA and RDT were 29.3% and 33.1%, respectively, with more positive cases detected in males than females. However, no association was found between toxocariasis and gender or age. The percentage sensitivity, specificity, positive predictive value and negative predictive value of RDT were 85.7%, 90.1%, 80% and 93.2%, respectively. The prevalence for toxocariasis in this population using both ELISA and RDT was 27.1% (36/133) and the K-concordance test suggested good agreement of the two tests with a Cohen's kappa of 0.722, P<0.01. In addition, the followed-up Spearman rank correlation showed a moderately high correlation at R=0.704 and P<0.01. In conclusion, the RDT kit was faster and easier to use than an ELISA and is useful for the laboratory diagnosis of hospitalized cases of toxocariasis.

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.

Prevalence and risk factors associated with Toxocara canis infection in children

The objective of this study was to determine seroprevalence and identify risk factors associated with Toxocara canis infection. A clinical and epidemiological questionnaire and body mass index were used to assess the risk factors associated with human toxocariasis in 108 children with an age range of 2-16 years. Antibodies against Toxocara canis were detected using an ELISA test kit. Chi-square analysis and odds ratio (OR) were used to identify risk factors associated with Toxocara canis seropositivity. The prevalence of antibodies against Toxocara canis was greater (P = 0.02) in males than females (28.84% and 16.07%, resp.). Chi-square analysis and odds ratio revealed just one variable with P < 0.05, and OR > 1.0 was associated with seropositivity: the possession of dogs under one year old (OR = 1.78). Although not significant, the OR values suggest that other factors may be epidemiologically important for Toxocara presence such as not washing hands before meals, malnutrition, obesity, and use of public parks. Children in the age group >12 and <16 years old had higher seroprevalence to Toxocara canis (17.59%) than the >2 and <11 years old age group (4.62%). Toxocariosis infection needs to be prevented by pet deworming and hygienic measures after contact with dogs.

Analysis of the course and treatment of toxocariasis in children-a long-term observation

Toxocariasis is a helminthozoonotic disease caused by ascarid larvae of Toxocara genus: Toxocara canis and Toxocara cati. In the reported study, the clinical course of toxocariasis and administered therapy were evaluated in 103 children. The majority of the children (68.9%) were from the rural environment, with a prevalence of boys (62.1%). At diagnosis of infection, 36 (35%) children reported recurrent abdominal pain, 19 (18.4%) headache, 6 (5.8%) loss of appetite, 2 subfebrile conditions, and 2 arthralgia, Moreover, 23 (22.3%) children demonstrated symptoms of atopic diseases; in 30 (29.1%) children, moderate enlargement of lymphatic nodes was noted. In five children (4.9%), ophthalmic examination revealed unilateral changes in the eye: in two cases retinitis; in one case fibrotic lesions in the vitreous body, complicated 1 year from diagnosis by retinal detachment; and in other children parafoveal lesions and cataract. Only two children with ocular changes at diagnosis reported visual disorders. In 64.3% of children, eosinophilia was observed. A covert form of the disease was diagnosed in 95.1% of the children and an ocular form in 4.9%. In all the children, antiparasitic treatment was implemented, repeated several times in some of them. After therapy, the mean titer of specific antibodies, the number of children with abdominal pains and enlarged lymphatic nodes were decreased, while headaches maintained at unchanged levels. In approximately one fourth of the children with negative results of antibodies after the therapy, the symptoms of the disease were still reported. Evaluation of the efficacy of treatment is not easy due to non-characteristic symptoms and low kinetics of specific anti Toxocara IgG decrease; however, high IgG titers suggest non-effective treatment of concomitant infection requiring subsequent therapy. Due to risk of ocular form, which may develop in any stage of the disease, irrespectively of specific antibodies concentrations, it seems justified to implement antiparasitic treatment in all children infected with T. canis.

Protective and risk factors for toxocariasis in children from two different social classes of Brazil

The aim of this study was to analyze the prevalence of Toxocara spp. antibodies in children from two different socioeconomic classes in the Presidente Prudente municipality, São Paulo State, Brazil, and the protective and risk factors associated with toxocariasis. One hundred and twenty-six middle-class (MC) and 126 disadvantaged children (DC) were included in this study. Anti-Toxocara ELISA test was performed in order to evaluate seroprevalence. A survey was applied to the children's guardians/parents in order to analyze the protective and risk factors. The overall prevalence was 11.1%, and of 9.5% (12/126) and 12.7% (16/126) for MC and DC subgroups, respectively. Toxocara seropositivity was inversely proportional to the family income. A high household income was considered a protective factor for toxocariasis in the total population and in both MC and DC subgroups. Being a girl was considered a protective factor for the total population and for both subgroups. Whilst being an owner of cat was a risk factor for children belonging to the total and for both MC and DC subgroups, having dog was considered as a risk factor for only the MC. Epidemiologic protective/factor risks can be distinct depending on the strata of the same population. Thus, it is relevant to evaluate these factors independently for different socioeconomic classes in order to design future investigations and programs for preventing the infection of human beings by Toxocara spp. and other geohelminths.

Helminth coinfection does not affect therapeutic effect of a DNA vaccine in mice harboring tuberculosis

Background

Helminthiasis and tuberculosis (TB) coincide geographically and there is much interest in exploring how concurrent worm infections might alter immune responses against bacilli and might necessitate altered therapeutic approaches. A DNA vaccine that codifies heat shock protein Hsp65 from M. leprae (DNAhsp65) has been used in therapy during experimental tuberculosis. This study focused on the impact of the co-existence of worms and TB on the therapeutic effects of DNAhsp65.

Methodology/Principal Findings

Mice were infected with Toxocara canis or with Schistosoma mansoni, followed by coinfection with M. tuberculosis and treatment with DNAhsp65. While T. canis infection did not increase vulnerability to pulmonary TB, S. mansoni enhanced susceptibility to TB as shown by higher numbers of bacteria in the lungs and spleen, which was associated with an increase in Th2 and regulatory cytokines. However, in coinfected mice, the therapeutic effect of DNAhsp65 was not abrogated, as indicated by colony forming units and analysis of histopathological changes. In vitro studies indicated that Hsp65-specific IFN-γ production was correlated with vaccine-induced protection in coinfected mice. Moreover, in S. mansoni-coinfected mice, DNA treatment inhibited in vivo TGF-β and IL-10 production, which could be associated with long-term protection.

Conclusions/Significance

We have demonstrated that the therapeutic effects of DNAhsp65 in experimental TB infection are persistent in the presence of an unrelated Th2 immune response induced by helminth infections.

From 14 diseases considered by WHO as Neglected Tropical Diseases, four involve helminth infections, such as schistosomiasis and soil-transmitted helminthiasis. Toxocariasis is a soil-transmitted worm highly prevalent in many developing countries, while schistosomiasis causes an annual mortality of 14,000 deaths per year, with 200–300 million infected people and 10% at risk of infection worldwide. Additionally, tuberculosis (TB) remains one of the leading causes of morbidity and mortality in many settings, particularly in the world's poorest countries. Mycobacteria and helminths are co-endemic and induce opposing patterns of immune responses in the host, recognized as Th1 and Th2 respectively. These co-existing patterns could be associated with the failure of TB vaccines. In this sense, we investigated the inflammatory and immune response in a coinfection model with T. canis or S. mansoni and M. tuberculosis analyzing the effects of an immunotherapy that has previously shown efficacy in experimental TB. This immunotherapy is based on a DNA vaccine that codifies a mycobacterial heat shock protein (hsp65), which can prevent TB in a prophylactic and also therapeutic setting. In this work, we show that helminth coinfection does not abrogate the therapeutic effects of DNAhsp65 vaccine against TB.