Seroprevalence of Toxocara canis infection in tropical Venezuela

Seroprevalence of human toxocariasis in Latin America and the Caribbean: a systematic review and meta-analysis

Introduction

The current study aimed to quantitatively synthesize available evidence regarding the seroprevalence of human toxocariasis in Latin America and the Caribbean.

Methods

A systematic research involving six electronic databases was conducted using a research strategy that combined MeSH terms with free terms. Article selection and information extraction were performed using a double and independent approach. The Newcastle-Ottawa tool was used to assess the risk of bias in the included articles. The meta-analysis used the random-effects approach, with subgroup analysis and sensitivity analysis for risk of bias also being performed.

Results

We included 101 articles with a total of 31,123 participants. The studies were conducted between 1990 and 2022, with Brazil accounting for the largest number of studies (n = 37). The overall seroprevalence of human toxocariasis was 31.0% (95% CI: 27.0-35.0%, I2 = 99%). The prevalence of the main characteristics observed in seropositive patients were as follows: ocular toxocariasis (30.0%), asymptomatic (26.0%), and presence of dogs at home (68.0%). In addition, the seroprevalence was lower in studies including only adults than in those including children or both. In contrast, no differences in seroprevalences were found between studies conducted in the community and hospital.

Conclusion

The overall seroprevalence of human toxocariasis in Latin America and the Caribbean was high. Notably, our findings showed that the seroprevalence was increased among populations who kept a dog at home but was decreased in populations comprising only adults. Our findings can be used to establish epidemiological surveillance strategies for the prevention and early identification of toxocariasis.

Low Toxocara Seroprevalence in People in Rural Durango, Mexico

The epidemiology of Toxocara infection in rural Mexico is largely unknown. Therefore, we sought to determine the seroprevalence of Toxocara infection in rural people in a northern Mexican state. We performed a cross-sectional seroprevalence study of 641 people living in rural Durango State including 282 subjects of the general population, 214 subjects of Huichol ethnicity, and 145 subjects of Mennonite ethnicity. Sera of participants were analyzed for the presence of anti-Toxocara immunoglobulin G (IgG) antibodies using a commercially available enzyme immunoassay. Three (0.5%) of the 641 subjects tested were positive for anti-Toxocara IgG antibodies. Of the 3 Toxocara seropositive subjects, two were females, aged 19 and 39 years, and one was male, aged 59 years. They had contacted with dogs, cleaned cat excrement, consumed unwashed raw fruits, contacted soil, or lived in a house with soil floors. Seroprevalence of Toxocara infection was similar among the 3 groups of population studied: 0.4% for the general population, 0.9% for Huicholes, and 0.0% for Mennonites (P = 0.41). In conclusion, the Toxocara seroprevalence found in subjects in rural Durango is low as compared with those reported in people from rural areas in other countries.

Seroprevalence and risk factors of toxocariasis in preschool children in Aragua state, Venezuela

BACKGROUND

Toxocariasis is a widespread zoonotic disease caused by the nematode Toxocara canis. In Venezuela, the magnitude of the disease is unknown and seroepidemiological studies have not been previously carried out in Aragua state.

METHODS

A cross-sectional field study was conducted in eight preschools in three municipalities from Aragua state in Venezuela. A total of 224 children aged between 1 and 6 years were studied (43.8% [98/224] male and 56.2% [126/224] female). Blood samples were obtained for detection of IgG antibodies against Toxocara spp. using ELISA. Participating families were given a questionnaire and children included in the study were clinically evaluated by paediatricians, and signs and symptoms observed were included in the questionnaires.

RESULTS

Anti-Toxocara spp. antibodies were detected in 29.0% (65/224) of children. The seroprevalence in the different preschools studied ranged between 4.2% and 60.6%. Leucocytosis and eosinophilia were also detected. Analysis of questionnaires indicated that boys were more at risk than girls. Younger children were also more at risk. Other significant risk factors were socio-economic strata (IV and V), inadequate improvised housing, earthen flooring indoors and outdoors and the presence of dogs in preschools.

CONCLUSIONS

The results from this work show the presence of infection and a high prevalence of antibodies against Toxocara spp. in the studied municipalities and indicate that toxocariasis poses a serious health problem to preschool children in Aragua state.

Epidemiology and control of child toxocariasis in the western Brazilian Amazon - a population-based study

Toxocara spp. infection and the seroconversion rate in the Amazon have been poorly investigated. This study analyzed individual and household-level risk factors for the presence of IgG antibodies to Toxocara spp. in urban Amazonian children over a period of 7 years and evaluated the seroconversion rates over a 1-year follow-up. In children < 59 months of age, the overall prevalence rate was 28.08% in 2003 and 23.35% in 2010. The 2010-2011 seroconversion rates were 13.90% for children 6-59 months of age and 12.30% for children 84-143 months of age. Multilevel logistic regression analysis identified child age, previous wheezing, and current infection with hookworm as significant associated factors for Toxocara spp. seropositivity in 2003. In 2010, age, previous helminthiasis, and having a dog were associated with seropositivity, whereas having piped water inside the household was a protective factor. Control programs mainly need to target at-risk children, water quality control, and animal deworming strategies.

The infectivity and antigenicity ofToxocara caniseggs can be retained after long-term preservation

Suspensions of fertilized eggs of Toxocara canis were mixed with 2% neutral formalin and preserved at 4 degrees C. When, after storage for 0, 12, 18, 21 and 24 months, samples of the eggs were incubated at 30 degrees C for 12 days, 96.8%, 92.6%, 74.1%, 51.0% and 19.3% of the eggs in the samples were found to embryonate. The embryonated eggs produced from the fertilized eggs preserved (in 2% neutral formalin at 4 degrees C) for 0, 12, 18 and 21 months were then tested for their infectivity to BALB/c mice, each mouse being given 800 embryonated eggs. The numbers of larvae recovered from the mice and the sites from which they were recovered, 2 or 14 days post-infection, appeared unaffected by the length of storage of the eggs. The infected mice all had similar eosinophil counts in their peripheral blood and similar serum titres of Toxocara-specific IgM and IgG antibodies, and cultures of their spleen cells produced similar amounts of interleukin-4, interleukin-5 and interferon-gamma when stimulated with concanavalin A. The results of SDS-PAGE indicated that egg preservation for at least 21 months had no effect on the excretory-secretory antigens in samples of medium from cultures of infective larvae released from the eggs. In summary, at least 50% of the fertilized eggs preserved in 2% neutral formalin at 4 degrees C for 21 months could fully embryonate and then had the same infectivity and antigenicity as embryonated fresh eggs.

Toxocariasis and epilepsy: systematic review and meta-analysis

Objective

Human toxocariasis is a zoonotic infection caused by the larval stages of Toxocara canis (T. canis) and less frequently Toxocara cati (T. cati). A relationship between toxocariasis and epilepsy has been hypothesized. We conducted a systematic review and a meta-analysis of available data to evaluate the strength of association between epilepsy and Toxocara spp. seropositivity and to propose some guidelines for future surveys.

Data Sources

Electronic databases, the database from the Institute of Neuroepidemiology and Tropical Neurology of the University of Limoges (http://www-ient.unilim.fr/) and the reference lists of all relevant papers and books were screened up to October 2011.

Methods

We performed a systematic review of literature on toxocariasis (the exposure) and epilepsy (the outcome). Two authors independently assessed eligibility and study quality and extracted data. A common odds ratio (OR) was estimated using a random-effects meta-analysis model of aggregated published data.

Results

Seven case-control studies met the inclusion criteria, for a total of 1867 participants (850 cases and 1017 controls). The percentage of seropositivity (presence of anti-Toxocara spp. antibodies) was higher among people with epilepsy (PWE) in all the included studies even if the association between epilepsy and Toxocara spp. seropositivity was statistically significant in only 4 studies, with crude ORs ranging 2.04–2.85. Another study bordered statistical significance, while in 2 of the included studies no significant association was found. A significant (p<0.001) common OR of 1.92 [95% confidence interval (CI) 1.50–2.44] was estimated. Similar results were found when meta-analysis was restricted to the studies considering an exclusively juvenile population and to surveys using Western Blot as confirmatory or diagnostic serological assay.

Conclusion

Our results support the existence of a positive association between Toxocara spp. seropositivity and epilepsy. Further studies, possibly including incident cases, should be performed to better investigate the relationship between toxocariasis and epilepsy.

Human toxocariasis is an infection caused by the larval stage of the worms Toxocara canis and less frequently Toxocara cati, common parasites of domestic and peridomestic dogs and cats. It is a cosmopolitan infection, occurring whenever the man-soil-dog relationship is particularly close, especially in tropical countries, where the humid climate favours the survival of parasite eggs in the soil, and in rural settings, where the poor hygiene increases the probability of human infection. Epilepsy affects nowadays at least 65 million of people worldwide and is particularly common in tropical areas, probably because of the presence of cases caused by infectious diseases largely absent in industrialized countries. For several decades, researchers have investigated the possible association between toxocariasis and epilepsy. In this study we conducted a statistical analysis of all the data available on the relationship between these two conditions. The combined results of the 7 studies included indicate an association between the two diseases. Further studies are necessary to demonstrate a causal relationship (i.e. toxocariasis causes epilepsy). Considering that toxocariasis is a preventable and common disease, a better understanding of the relationship between toxocariasis and epilepsy may contribute to improving prevention of epilepsy worldwide.

IgG Antibody responses in mice coinfected with Toxocara canis and other helminths or protozoan parasites

The immune response expressed by IgG antibodies in BALB/c mice experimentally infected with Toxocara canis, was studied with the aim of verifying the possible in vivo cross-reactivity between antigens of T. canis and other parasites (Ascaris suum, Taenia crassiceps, Schistosoma mansoni, Strongyloides venezuelensis and Toxoplasma gondii). Experiments included three groups of mice: one infected only by T. canis, another with one of the other species of parasites and a third concomitantly infected with T. canis and the other species in question. Animals were bled by orbital plexus at 23, 38 and 70 days post infection (p.i.). Sera were analyzed for anti-Toxocara antibodies by ELISA and Immunoblotting, using excretion-secretion antigens (ES), obtained from culture of third-stage larvae of T. canis. For all experiments a control group comprised by ten non-infected mice was used. Only in the case of A. suum infection, in these experimental conditions, the occurrence of cross-reactivity with T. canis was observed. However, in the case of co-infection of T. canis - S. mansoni, T. canis - S. venezuelensis and T. canis - T. crassiceps the production of anti-Toxocara antibodies was found at levels significantly lower than those found in mice infected with T. canis only. Co-infection with S. mansoni or S. venezuelensis showed lower mortality rates compared to what occurred in the animals with single infections. Results obtained in mice infected with T. canis and T. gondii showed significant differences between the mean levels of the optical densities of animals infected with T. canis and concomitantly infected with the protozoan only in the 23rd day p.i.

Visceral larva migrans in immigrants from latin america

To determine whether increased migration is associated with an increase in incidence of toxocariasis (visceral larva migrans), we analyzed clinical data obtained from immigrants from Latin America. Although infection with Toxocara sp. roundworm larvae is distributed worldwide, seroprevalence is highest in tropical and subtropical areas.

Human toxocariasis: a seroepidemiological survey in the Amazonian city of Yurimaguas, Peru

The aim of this study was to determine the seroprevalence of the infection by Toxocara in the general population of the Amazonian city of Yurimaguas, Peru. From March to August 2008, a total of 300 subjects were sampled and tested by means of a Toxocara ELISA-IgG test. A clinical and epidemiological questionnaire was used to assess the symptomatology and risk factors associated with human toxocariasis. The overall rate of seropositivity was 35.66%, with a significant high proportion in children (p < 0.001). The clinical evaluation revealed that 95.33% of the seropositive group had some type of symptomatology: headache (66.36%), respiratory compromise (63.55%), abdominal pain (54.21%), cutaneous signs (40.19%) and ocular manifestations (36.45%), and almost all of them were statistically significant (p < 0.001). Furthermore, 56.07% of the seropositive subjects presented at least one intestinal pathogen parasite with predominance of helminthes, but without significant association (p = 0.334). The analysis of risk factors showed only that the use of public places and geophagia exhibited a significant association with the seropositivity (p < 0.001). Clinical, serological and epidemiological findings associated to infection with Toxocara were observed in the present study and future studies should be done to assess this serious health problem.

Seroprevalence of human toxocariasis in Andean communities from the Northeast of Lima, Peru

The aim of this study was to assess the seroprevalence of human toxocariasis in three Andean communities from the Northeast of Lima, Peru. A total of 303 subjects including children and adults were studied and blood samples were collected to detect anti-Toxocara antibodies by ELISA-IgG test and by hematological examination; stool samples were collected also for parasitological examination. The overall seroprevalence of toxocariasis observed in the total population was 20.46%, with a significant high proportion in children from one to 10 years old (p = 0.034). Among the subjects with positive serology, 32.26% of them had respiratory disturbances, 22.58% hepatomegaly, 17.74% ocular signs or symptoms, 14.51% abdominal pain, 9.68% neurological involvement, and 4.84% cutaneous signs, but none of these clinical features were associated to a positive serology by multivariate analysis. Furthermore, 79.03% of seropositive subjects also harbored at least one intestinal parasite, which was associated to a positive serology (p < 0.05). The presence of pets within the houses, a previous history of pica or geophagia and the use of public places were also present in this population, but only the latter was associated to the serology (p < 0.05). In conclusion, clinical, serological, and epidemiological evidences for larval Toxocara infection were found in the studied population.

Frequency of eosinophilia and risk factors and their association with Toxocara infection in schoolchildren during a health survey in the north of Lima, Peru

During a health survey in a primary school from the district of Carabayllo (North of Lima, Peru), 200 schoolchildren (96 male and 104 female between five to 12 years old) were randomly selected and divided in two groups (as positive or negative group), according to the serologic result of the Toxocara ELISA test from a total population of 646 schoolchildren. All children were analyzed by hematologic tests to determinate the frequency of eosinophilia and leukocytosis. Additionally, all clinical and epidemiological data were also analyzed to determine their association with toxocariasis. From group of children with positive serology, 40% had some type of eosinophilia in contrast to 19% of children with negative serology, and their association was statistically significant (OR = 2.84, p < 0.001). From all signs and symptoms evaluated, only 'dry cough' was more frequent and statistically significant in the positive serology group (OR = 2.79, p < 0.001). Almost all risk factors evaluated were highly frequent and statistically associated to the positive serology. In conclusion, the presence of eosinophilia and the risk factors evaluated in this population were frequently associated to human toxocariasis.

Frequency of human toxocariasis in a rural population from Cajamarca, Peru determined by DOT-ELISA test

The aim of this study was to estimate the frequency of human toxocariasis in Cauday district, Cajamarca, Peru, using a dot-ELISA test. From June to October 2005, a total of 256 adult subjects were studied. Blood samples were collected for serology by a dot-ELISA test and for hematological examination. Parasitological examination was also carried out in stool samples to check cross-reactions in the dot-ELISA. The frequency observed was 44.92%, with a significant higher proportion of positivity in male subjects. From subjects with positive serology, 45.6% had respiratory symptoms, 40.44% abdominal pain, 32.35% hepatic symptoms, 14.7% cutaneous signs, 13.23% ocular manifestations, 43.38% eosinophilia, and all of these were statistically associated to serology. Among the population evaluated, 90.23% (231/256) were parasitized. From subjects with positive serology, 92.17% had at least one intestinal parasite and the most frequent were: Blastocystis hominis (68.38%), Giardia lamblia (28.68%), Hymenolepis nana (20.0%), Ascaris lumbricoides (15.65%), Entamoeba histolytica/E. dispar (13.24%), Cyclospora cayetanensis (4.41%), Cryptosporidium sp. (1.47%), Enterobius vermicularis (0.87%), Strongyloides stercoralis (0.87%), Taenia sp. (0.87%), and Trichuris trichiura (0.87%). The rate of false positives in the dot-ELISA test was improved by serum absorption each with A. suum antigens, with a decrease of cross-reactions. In conclusion, human toxocariasis is highly frequent in this population and some risk factors like dog/cat ownership, presence of pets within house, and previous history of geophagia were observed in the present study.

Clinical and serological evidence of Toxocara infection in school children from Morrope district, Lambayeque, Peru

The aim of this study was to estimate the frequency of human toxocariosis in a child population from Morrope district, Lambayeque, Peru. From October to December 2005, 182 school children (96 male and 86 female) were studied. Blood samples were collected for Toxocara ELISA-IgG test and hematological examination. Additionally, stool samples were collected for coproparasitological examination to check cross reactions. We found frequency of positives in 32.4% (59/182) with a significant higher proportion of positivity in male children (p < 0.00001). 71.2% of the children with positive serology (52 male and seven female), were between five and 10 years old, 77.96% had respiratory symptoms, 61.02% had ocular manifestations, 38.98% had hepatic symptoms, 38.98% had mild or moderate eosinophilia, signs statistically associated with seropositivity. 83.5% of studied population had some intestinal parasite, such as: Blastocystis hominis (53.3%), Giardia lamblia (31.3%), Entamoeba coli (29.1%), Entamoeba histolytica/E. dispar (1.1%), Hymenolepis nana (5.49%), and Ascaris lumbricoides (3.3%), but they had not any association with serology results. The ownership of dogs or/and cats were significantly associated with seropositivity to anti-Toxocara antibodies although the presence of such pets within the house was not. In conclusion, clinical and serological evidence of Toxocara infection exists in the studied population.

Epilepsy and toxocariasis: a case-control study in Italy

PURPOSE

To assess the relationship between epilepsy and toxocariasis in adult subjects by means of a case-control study in Catania, Italy.

METHODS

People with epilepsy (PWE) were randomly selected from the database of the center of epilepsy of our department. Epilepsy was diagnosed according to the definition proposed by the International League Against Epilepsy. One healthy control per each case was selected among subjects who went to the central laboratory for a hematological check. Control subjects underwent a complete neurological examination to exclude the presence of neurological disorders. PWE and controls were assessed serologically for antibodies against Toxocara canis (T. canis) by an immunoblotting assay.

RESULTS

Two hundred thirty-one PWE (110 men and 121 women) and 201 controls (126 men and 75 women) were enrolled in the study. Of the 231 PWE, 152 presented partial seizures. Antibodies anti-T. canis were found in 38 PWE (16.4%) and in 13 controls (6.6%) giving a crude OR of 2.85 (95% CI 1.47-5.51). Adjusted OR estimated by logistic regression was 3.90 (95% CI 1.91-7.98). This association was mainly due to a significant association between Toxocara antibodies and partial epilepsy (adjusted OR 4.69; 95% CI 2.24-9.80), while a positive, but not significant, association was found with generalized seizures (adjusted OR 1.74; 95% CI 0.60-5.05).

CONCLUSION

We found a significant association between T. canis seropositivity and epilepsy and a stronger association was found with partial epilepsy. Our finding suggests that toxocariasis may increase the risk of epilepsy.

Epilepsy and toxocariasis: a case-control study in Burundi

PURPOSE

A case-control study to assess the relationship between epilepsy and toxocariasis was carried out in the Kiremba population, Burundi.

METHODS

People with epilepsy (PWE) were diagnosed according to the definition proposed by the International League Against Epilepsy (ILAE). Seizures were classified according to the classification proposed by ILAE in 1981. One control per case was selected matched by age (+/-5 years). Control subjects also lived in Kiremba, had neither neurological disorders nor kinship with the PWE. Cases and controls were assessed serologically for antibodies against Toxocara canis by an immunoblotting assay. Odds ratios (ORs) and 95% CI were determined using conditional regression analysis for matched case-control study.

RESULTS

One hundred ninety-one PWE (99 men and 92 women) and 191 age-matched controls (72 men and 112 women) were enrolled in the study. Of the 191 PWE, 113 presented partial seizures while 73 generalized seizures and five were unclassifiable. Antibodies anti T. canis were found in 114 PWE (59.7%) and in 97 controls (50.8%). Multivariate analysis (conditional logistic regression) showed a significant association between positivity for T canis and epilepsy with an adjusted OR of 2.13 (95% CI 1.18-3.83; p-value 0.01).

CONCLUSIONS

We found a significant association between toxocariasis and epilepsy. In agreement with a previous study, our finding suggests that toxocariasis may increase the risk of developing epilepsy in endemic areas and could participate to the high burden of epilepsy in tropical areas.

Epilepsy and seropositivity rates of Toxocara canis and Toxoplasma gondii

PURPOSE

Increased seropositivity for Toxoplasma gondii and Toxocara canis have been observed in epileptic patients. Our aim is to determine whether there is any relationship between these agents and epilepsy in our cryptogenic epilepsy group.

MATERIAL AND METHODS

We studied specific IgG antibodies against T. gondii and T. canis in 100 cryptogenic epileptic patients and 50 healthy volunteers that had no history of epilepsy in their first degree relatives. We studied T. gondii and T. canis-specific IgG antibody serum levels and compared the values of these two groups.

RESULT

We found similar T. gondii and T. canis serum IgG antibodies in patients with cryptogenic epilepsy and in the control group, even though the control group included more animal owners.

CONCLUSION

We did not show any relationships between epilepsy and positive T. gondii and T. canis serology in our epileptic patients.

Clinical status and parasitic infection in a Wichí Aboriginal community in Salta, Argentina

In a study, carried out in 2000, of the clinical and parasitological status of a Wichi Aboriginal community living in the suburbs of Tartagal, northern Salta, Argentina, 154 individuals were screened for parasitic infections. Ninety-five faecal samples were also obtained from the same population. Ninety-three percent of the subjects were positive for 1 or more of the parasites investigated by direct test and 70.5% of them had parasitic superinfection. The most frequent helminths were Strongyloides stercoralis (50.5%) and hookworm (47.4%). We found low reinfection rates and a long reinfection period after treatment and provision of safe water and sanitation. Serum reactivity of these patients was analysed by enzyme-linked immunosorbent assay and indirect immunofluorescent assay and 22.1% of them had anti-Toxocara antibodies, 16.2% were positive for a complex antigen of Leishmania braziliensis, 29.9% were positive for a complex Trypanosoma cruzi antigen, and 17.5% were positive for a specific Trypanosoma cruzi antigen, Ag 163B6/cruzipain.

Human toxocariasis: frequency of anti-Toxocara antibodies in children and adolescents from an outpatient clinic for lymphatic filariasis in Recife, Northeast Brazil

In a transversal study on a sample of 386 children and adolescents from an outpatient clinic for filariasis in Recife, Northeast Brazil, the frequency of anti-Toxocara antibodies and its relation to age, gender, number of peripheral eosinophils, Wuchereria bancrofti microfilariae and intestinal helminths was determined. The total anti-Toxocara IgG antibody frequency was 39.4%, by ELISA technique. The difference in frequency between males (40.1%) and females (37.6%) was not statistically significant. The 6 to 10-year-old subset presented the highest frequency of anti-Toxocara antibodies (60%), and within this age group there was a statistically significant male bias. There was also a significant association between the number of eosinophils and the presence of anti-Toxocara antibodies. Intestinal parasite frequency was 52.1%, but no association was found between this data and the presence of anti-Toxocara antibodies. In the present sample, 42.2% of the patients were Wuchereria bancrofti carriers, however, again this was not associated with the presence of anti-Toxocara antibodies. In conclusion, anti-Toxocara antibodies were highly prevalent in this sample. The present data show that there is no cross correlation between anti-Toxocara IgG antibody and the presence of intestinal helminths and filariasis.

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%.

[Toxocariasis: clinical and laboratory features in 54 patients]

OBJECTIVE

To describe the clinical and laboratory findings in children with toxocariasis.

METHODS

Fifty-four children with reactive serology to Toxocara determined by ELISA were prospectively identified between January 1998 and September 2000. The patients were divided into three groups: asymptomatic children (n 24), those with visceral larva migrans (n 16) and those with ocular larva migrans (n 14). Age, serology titers, and eosinophil count at diagnosis were compared among the groups. The patients received treatment with albendazole 10-15 mg/kg/day for 15 days or thiabendazole 25 mg/kg/day in two series of 7 days.

RESULTS

The clinical features were as follows: 24 children (44.4 %) were asymptomatic, pneumonitis was found in 9 (16.7 %), hepatomegaly in 6 (11.1 %), acute posterior uveitis in 5 (9.3 %), strabismus in 5 (9.3 %), leukocoria in 4 (7.4 %), fever in 3 (5.6 %). There was 1 case of keratitis, 1 of cataracts, 1 of myocarditis and 1 case of pneumonia with pleural effusion. Some patients showed more than one clinical feature. Four children experienced loss of vision in the affected eye. No differences in age or serology titers were found among the groups. Eosinophil count was lower in the group with ocular larva migrans than in the other groups (p < 0.001). Children with active disease showed clinical improvement and a 70.4 % decrease in eosinophilic count one year after treatment. Serological titers showed an unpredictable pattern during the follow-up.

CONCLUSIONS

Most of the infected children were asymptomatic. In the post-treatment follow-up, clinical improvement and a decrease in eosinophilic count were observed. Further studies are needed to evaluate the efficacy of treatment, especially in asymptomatic children.

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.

Epilepsy, cysticercosis, and toxocariasis: a population-based case-control study in rural Bolivia

OBJECTIVE

To assess the relationship between epilepsy and infection with Taenia solium and Toxocara canis with a case-control study, in the rural area of the Cordillera Province, Bolivia.

METHODS

A preliminary two-phase door-to-door prevalence survey determined the prevalence of epilepsy and identified cases and control subjects. At least two control subjects per case were selected, matching on sex, age, and community of residence. Cases and control subjects were assessed serologically for antibodies against T. canis by ELISA and against T. solium by enzyme-linked immunoelectrotransfer blot (EITB).

RESULTS

The prevalence survey found 130 confirmed cases of epilepsy, of which 113 were eligible for the case-control study (59 partial seizures and 54 generalized seizures). Two hundred thirty-three control subjects were selected. Multivariable analysis for a matched case-control study was carried out. There was an association between EITB positivity for T. solium and epilepsy with an OR of 1.85 (95% CI 0.99 to 3.4) for all cases. A stronger association was found in those with partial epilepsy with a late onset of disease (15 years and older), where the OR was 3.66 (95% CI 1.10 to 12.10). A positive association was also found with T. canis for all cases with an OR of 2.70 (95% CI 1.41 to 5.19). This increased for those with late-onset partial epilepsy to an OR of 18.22 (95% CI 2.10 to 158.10).

CONCLUSION

This finding suggests that both neurocysticercosis and toxocariasis may in part explain the higher prevalence of epilepsy, particularly partial epilepsy, in developing countries.

[The association between human toxocariasis and pyogenic abscesses]

The association between hepatic abscesses and schistosomiasis mansoni was confirmed by clinical and experimental studies. Other parasites may cause systemic immunologic changes and local structural alterations in the affected organs that can facilitate the seeding of these areas by bacteria. Tropical pyomyositis, pyogenic liver and renal abscesses are frequent diseases in tropical areas. The visceral larva migrans syndrome is caused by the presence, in the human body, of larvae of worms that have other animals as their definitive host, most commonly being caused by Toxocara canis. The larvae migrate to various body organs leading to many inflammatory reactions in the form of granuloma and tissue necrosis. In this review we discuss the possible host-parasite-bacteria interactions that would favour the formation of abscesses in the organs involved by the larva of T. canis and present preliminary results of a clinical and experimental study undertaken during the last four years to define the role of this parasite in the pathogenesis of the abscesses.

Prevalence of anti-Toxocara antibodies in a random sample of inpatients at a children's hospital in Vitória, Espírito Santo, Brazil

In the streets of Vitória, in the State of Espírito Santo, Brazil, are large number of stray dogs, many of which are infected with Toxocara canis, suggesting a high risk for human infection. In order to investigate the prevalence of Toxocara infection in children in Espírito Santo we studied the prevalence of anti-Toxocara antibodies in 100 random inpatients over one year of age, at the Children's Hospital N.S. da Glória, the reference children's hospital for the State. All the sera were collected during the period between October 1996 and January 1997. The mean age was 6.6 +/- 4.1 yrs. (1 to 14 yrs., median 6 yrs.) and there were patients from all of the different wards of the hospital. Sixty-eight patients came from the metropolitan area of Vitória and the other 32 from 17 other municipalities. The anti-Toxocara antibodies were investigated by ELISA-IgG using a secretory-excretory antigen obtained from second stage larvae. All sera were adsorbed with Ascaris suum antigen before the test. Thirty-nine sera (39%) were positive, predominantly from boys, but the gender difference was not statistically significant (boys: 25/56 or 44.6%; girls: 14/44 or 31.8%; p = 0.311). The prevalence of positive sera was higher, but not statistically significant, in children from the urban periphery of metropolitan Vitória (formed by the cities of Vitória, Cariacica, Vila Velha, Serra and Viana) than in children from 17 other municipalities (44.1% and 28.1% respectively, p = 0.190). Although the samples studied do not represent all children living in the State of Espírito Santo, since the Children's Hospital N.S. da Glória admits only patients from the state health system, it is probable that these results indicate a high frequency of Toxocara infection in children living in Espírito Santo. Further studies of population samples are necessary to ascertain the prevalence of Toxocara infection in our country.

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

The prevalence of human toxocarosis in disadvantaged socioeconomic population in Europe is unknown. In Gipuzkoa the seroprevalence in middle-class children 2- to 5-years-old, and 6- to 16-year-olds, was zero (n = 135) and 4.4% (n = 320), respectively. In contrast, among socially and economically disadvantaged children the figures were 37% (n = 27) and 65.7% (n = 64). This high prevalence obliges us to consider toxocarosis as a public health problem.

Relationship between parasitical inoculum and immunological parameters in experimental toxocariasis

Swiss female mice were inoculated with different infective doses of Toxocara canis eggs to evaluate the percentage of recuperated larvae in different organs and immunological parameters such as spleen index (SI), liver index (LI) and lung index (LuI) and blood eosinophilia during 3 weeks post infectionem (p.i.) with only one challenge. It was found that T. canis larvae arrived at the liver between 10 and 15 hours p.i. by the food-fishhook technique. When the inoculum was more than 200 eggs, there was a reinvasion of liver and lungs at 504 hours p.i. The larval arrival at the brain was delayed in an inverse relationship to the inoculum but the percentage of recovery was about 7 and 8%. The organic indexes were in a direct relationship with the inoculum size and the increase in eosinophilic levels in massive infections (2000 eggs) was in agreement with a strong immune response.

Epidemiology of human toxocariasis in La Réunion

In La Réunion island (Indian Ocean) a seroepidemiological survey for toxocariasis was carried out among 387 subjects over 15 years old by Western blotting using Toxocara canis excretory-secretory larval antigens; 92.8% of the sera were positive. Statistical study, including logistic regression analysis, showed a significant correlation of Western blot results with sex, age, and absence of water supply. The final logistic model demonstrated that only the last 2 factors were significant multiplicative risk factors for toxocariasis. Sex was an independent risk factor. With this level of infection, we suggest that further surveys of ocular toxocariasis in children and teenagers of La Réunion would be advisable.

Comparable seropositivity for ascariasis and toxocariasis in tropical slum children

The seropositivities for infection by Ascaris lumbricoides and Toxocara canis were determined in children (1-15 years old) of a slum area of Caracas, Venezuela, and the levels that indicate the presence of active infection were defined. In children aged from 1 to 3 years, approximately 10% were positive for either parasite, and this figure increased to about 30% in 4- to 6-year-olds. For toxocariasis, the percentage of positivity remained at this level up to the age of 15 years. Whilst the positivity in children 10-15 years of age was comparable for Ascaris and Toxocara, a peak of positivity (50%) was found for Ascaris at 7-9 years of age. These results indicate that for these urban slum children, infection by Toxocara is essentially as common as that by Ascaris and, thus, that toxocariasis represents a potential public health problem in the tropical environment that is largely overlooked.

Standardization of dot-ELISA for the serological diagnosis of toxocariasis and comparison of the assay with ELISA

The dot-enzyme-linked immunosorbent assay (dot-ELISA) was standardized using somatic (S) and excretory-secretory (ES) antigens of Toxocara-canis for the detection of specific antibodies in 22 serum samples from children aged 1 to 15 years, with clinical signs of toxocariasis. Fourteen serum samples from apparently normal individuals and 28 sera from patients with other pathologies were used as controls. All samples were used before and after absorption with Ascaris suum extract. When the results were evaluated in comparison with ELISA, the two tests were found to have similar sensitivity, but dot-ELISA was found to be more specific in the presence of two antigens studied. Dot-ELISA proved to be effective for the diagnosis of human toxocariasis, presenting advantages in terms of yield, stability, time and ease of execution and low cost.

Immunodiagnosis of toxocarosis in humans: evaluation of a new enzyme-linked immunosorbent assay kit

Excretory/secretory (E/S) antigen derived from second-stage larvae of Toxocara canis maintained in defined medium in vitro has been well established worldwide for the immunodiagnosis of human toxocarosis by enzyme-linked immunosorbent assay. Such an enzyme-linked immunosorbent assay, based on the detection of human anti-T. canis (E/S antigen) serum immunoglobulin G, has recently been commercialized by Biokema-Affinity Products (Crissier-Lausanne, Switzerland). This commercial test kit was evaluated with regard to its application in a routine diagnostic laboratory and the reliability of the results. Of 78 patients with suspected clinical toxocarosis, 71 had anti-T. canis antibodies (positive serological result) corresponding to a diagnostic sensitivity of 91%; 14% of serum samples (n = 199) from patients with protozoan or with helminthic infections also showed positive reactions mainly related to infections with Trichinella, Strongyloides, and Fasciola species. An epidemiological study with 1,000 serum samples from randomly selected healthy blood donors and children in Switzerland demonstrated a seroprevalence of 2.7%. The test kit under evaluation had an overall diagnostic sensitivity of 91% and a relative specificity of 86%, the latter being related to some protozoan and helminthic infections. Because of the scarcity of such infections, potential cross-reactivity does not play a major role under the conditions found in the middle part of Europe. In conclusion, the application of the test kit provided for use in this study can be recommended for routine diagnostic use.

Visceral larva migrans: a seroepidemiological survey in five municipalities of São Paulo state, Brazil

An enzyme-linked immunosorbent assay (ELISA), employing antigens from Toxocara canis larvae and the absortion of suspected sera with Ascaris lumbricoides extracts was used in a seroepidemiological study performed in five municipalities of São Paulo State, Brazil (São Paulo, Campinas, Santos, Marília and Presidente Prudente) in order to determine the frequency of antibodies to Toxocara. In 2,025 blood samples collected, 806 proceeded from male subjects and 1,219 from females; 483 samples were collected from subjects under 15 years of age and the remaining 1,542 from subjects aged 15 years or over. Among the 2,025 sera investigated, 3.60% had antibodies to Toxocara at significant levels. A moderate predominance of infection with Toxocara among male subjects (3.72%) was observed, although the difference was not statistically significant when this rate was compared with that for female (3.28%). Related to age, a higher frequency of positive results was detected among subjects under 15 years (6.41%) against the older group (2.53%). A trend of more elevated rates of infection was observed in municipalities with high demographic densities (São Paulo, Campinas and Santos). Nevertheless, such findings only appeared to be statistically significant in subjects younger than 15 years.

Specificity of Toxocara ELISA in tropical populations

The diagnosis of human infection by Toxocara canis relies heavily upon serological tests, the specificity of which can be inadequate in regions of endemic helminthiasis. When different population groups of tropical Venezuela were evaluated using ELISA based upon Toxocara excretory-secretory antigen (TcESA), solid-phase adsorption of the sera with extracts of a wide variety of non-homologous parasites revealed the existence of significant cross-reactivity. This was effectively and conveniently overcome when the test sera were incubated in the presence of the soluble parasite extracts in a competitive inhibition ELISA. The mean reduction of ELISA values caused by pre-adsorption of the sera tested was 32.2%, and that caused by competitive inhibition was 42.3%, the effects of these two procedures being strongly correlated (r = 0.83). The magnitude of the reduction was inversely proportional to the actual ELISA value (r = -0.55), and ranged from a mean of 68.0% in sera from apparently healthy individuals of medium-high socio-economic level, down to 28.1% in heavily parasitized Amazon indians. Ascaris showed the greatest degree of cross-reactivity in these tests, although under conditions of competitive inhibition even sera with high levels of antibody against this parasite could be negative in Toxocara ELISA. Western blotting revealed a major 81,400 D component that was shared between Ascaris and TcESA. Our results indicate that the competitive inhibition of cross-reactivity by soluble non-homologous parasite extracts provides a convenient and economical means of increasing the specificity of ELISA for the determination of the seroprevalence of toxocariasis in tropical populations.