Status of human toxocariasis, a neglected parasitic zoonosis in Iran: a systematic review from past to current.

Although human toxocariasis can lead to serious complications including neurological, ocular and visceral complications, there is a lack of comprehensive epidemiological information about the seroprevalence of Toxocara species in humans. In the present study, we analysed and reviewed the overall seroprevalence of human toxocariasis in Iran. The data collection was systematically undertaken on published articles using the PubMed, Google Scholar, ScienceDirect and Scopus databases. A total of 27 studies from the past two decades reporting seroprevalence of human toxocariasis met our eligibility criteria. The pooled proportion of Toxocara infection was estimated as 6.58% (95% confidence interval = 3.98-9.77). A wide variation between different studies was observed (Q statistic = 799.37, df = 26, P < 0.0001, and I2 = 96.7%). The seroprevalence rate of toxocariasis in the Iranian population is relatively high; contamination of the environment by eggs from the host as well as from household dogs and cats should be blamed.

Seroprevalence and associated risk factors of Toxocara infection in Korean, Manchu, Mongol, and Han ethnic groups in northern China.

Toxocariasis is a very prevalent zoonotic disease worldwide. Recently, investigators have focused more on Toxocara spp. seroprevalence in humans. Information regarding Toxocara seroprevalence in people from different ethnic backgrounds in China is limited. For this study, blood samples were collected from a total of 802 Han, 520 Korean, 303 Manchu, and 217 Mongol subjects from Jilin and Shandong provinces. The overall Toxocara seroprevalence was 16·07% (14·21% Han, 20·58% Korean, 11·22% Manchu, 18·89% Mongol). Living in suburban or rural areas, having dogs at home, exposure to soil, and consumption of raw/undercooked meat were risk factors for Toxocara infection. Exposure to soil was identified as the major risk factor for Toxocara seropositivity in all of the tested ethnicities. To the best of our knowledge, this is the first report concerning Toxocara infection in Manchus and Mongols in China. The present study provided baseline data for effective prevention strategies of toxocariasis in northeast China and recommends improvements in personal hygiene standards to achieve this goal.

Incidence of Ascaris suum-specific antibodies in Austrian patients with suspected larva migrans visceralis (VLM) syndrome.

The pig roundworm, Ascaris suum, is commonly found in domestic pigs all over the world. The transmission to humans takes place by ingestion of infective A. suum eggs present in soil because pig manure is widely used as fertilizer. The possible role of A. suum in the human visceral larva migrans (VLM) syndrome has been discussed controversially during past decades, even though various case reports, particularly from Japan document pulmonal, hepatic and even cerebral symptoms caused by migrating A. suum larvae after ingestion of infected row meat (liver) or contaminated vegetables. We examined 4481 sera by A. suum immunoblot (As-IB) and 5301 sera by Toxocara-ELISA from patients with symptoms associated with the VLM syndrome during three consecutive years (2012-2014). The incidence of A. suum-specific antibodies was 13.2 %, the incidence of T. canis specific antibodies 12.9 % and from a part of the As-IB positive sera (n = 417) additional Toxocara serology was performed to demonstrate the specificity of our tests. Only 56 out of the 417 (13.4 %) sera showed antibodies to both helminth species demonstrating that double infections exist. Interestingly the age distribution of the patients showed that 2.8 % of the Ascaris-positive patients were younger than 21 years, while in the Toxocara-positive group 13.4 % were <21 years. These results are in accordance with a Dutch study suspecting different ways of transmission as cause for this interesting age distribution. Due to the fact that large amounts of untreated pig manure are used as fertilizer and that the expulsion of adult A. suum worms causing intestinal ascariosis is extremely rare in Central European countries, the zoonotic potential of A. suum is considerably underestimated. We suggest that the performance of reliable immunoserological tests, in all industrialized countries where pigs are raised and their manure is used as fertilizer, could help to assess the actual potential of A. suum as causative agent of the VLM syndrome in humans.

Factors affecting disease manifestation of toxocarosis in humans: genetics and environment.

Toxocara canis is regarded as the main cause of human toxocarosis but the relative contribution of T. cati is probably underestimated; serological and other diagnostic methods used in most studies of this zoonotic disease do not distinguish between the two parasites. The definitive hosts for T. canis are caniidae. Pups generally have higher infection rates than adult animals and are a major source of eggs in the environment. Humans usually acquire T. canis infection by accidental ingestion of embryonated eggs or encapsulated larvae from the environment or contaminated food, such infections may lead to visceral larva migrans (VLM), ocular larva migrans (OLM) or covert toxocarosis (CT). Although a mixed Th1- and Th2-mediated immunological response, particularly with high levels of IgE and eosinophilia is observed, the underlying mechanisms of molecular and immunopathogenesis for the development of the symptomatic syndromes of VLM, OLM, or of asymptomatic CT are largely unclear. Studies have indicated that immunological defences against various infectious diseases may be highly influenced by complex interactions of environmental and host genetic factors e.g. MHC class I and II, also known as human leucocyte antigen (HLA). Toxocara spp. infections are associated with a polarized CD4(+) Th2 response with high IgE levels and eosinophilia, mediated mainly by HLA class II molecules. Associations have been made between HLA class II and pathological severity and host genetic effects on exposure to infection. Recent research suggests Foxp3(+) CD4(+)CD25(+)-expressing T regulatory (Treg) cells play a role in regulation of the immunopathology of granulomas in experimental toxocaral granulomatous hepatitis and in enhanced expression of TGF-ß1, which is an important factor for the local survival and function of Treg observed during T. canis invasion in the mouse small intestine, liver, muscle, and brain. Since the potential susceptibility loci HLA class II molecules, are considered involved in the regulation of a Th2-dominant immunity which is highly controlled by Foxp3(+) CD4(+)CD25(+) Treg cells by stimulation through TGF-ß1, which thus provides a beneficial environment to T. canis larvae but severe injuries to local organs. However, TGF-ß1 variant Leu10Pro known to be involved in disease severity warrants further elucidation as this too may have a role in the severity of human toxocarosis. Exploration of TGF-ß1 polymorphism, Foxp3(+) CD4(+)CD25(+) Treg cells, and MHC polymorphisms may allow insight into the contribution made by environmental and genetic factors in influencing disease syndrome type and severity in humans with toxocarosis.

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.

The role of worm infestation in allergic rhinitis.

The purpose of this study is to determine the relevance of the hygiene hypothesis; that is to determine if worm infestation has a protective role against the development of allergic rhinitis. A prospective case controlled study was conducted. Specific IgG levels to Toxocara were studied in 85 patients confirmed to have allergic rhinitis and were compared to levels in another 85 controls, with no form of allergy. The IgG assay was done using ELISA technique. There was a higher incidence of positive specific IgG to Toxocara in the controls as compared to allergic patients. The values were statistically significant [Chi square test (p=0.002)]. This negative association between worm infestation and allergic rhinitis suggests that a previous worm infestation could protect against the development of allergic rhinitis.

Epidemiological situation of toxocariasis in Iran: meta-analysis and systematic review.

Toxocariasis is the clinical terms applied to infection of human with ascarid nematodes in the order Ascaridida, named toxocara canis and toxocara cati. It is transmitted from dog and cat to humans. Accidental ingestion of parasite eggs causes ocular and visceral larva migrans in human. The aim of this study is to study epidemiology of toxocariasis in Iran using meta-analysis and systematic review. Using main key words of toxocariasis including epidemiology, Toxocara spp. Iran, dog and cat in databases such as SID, Google scholar, Pubmed, Magiran and Iranmedex, a number of 50 articles was extracted. A number of 27 articles of them were eligible for meta-analysis. Data extracted from articles and archived in excel software for analysis. Variance of each study obtained using binomial distribution. Heterogeny of studies surveyed using Cochrans Q test. Data analyzed using Random Effect Model test. Overall prevalence of toxocariasis obtained 21.6% in Iran. In total of 27 articles, 6911 samples including 1543 carnivores, (13 articles), 4569 human sera (10 articles) and 799 soil samples (4 articles) has been investigated. Seropositivity for human toxocariasis 15.8% (95%CI, 9.2-22.5), soil contamination for Txocara spp. eggs 21.6% (95%CI,-1.6-44.8) and dogs and cats infections with adult worm 26.8% (95%CI, 18.7-36.8) was obtained. Results of this study show that prevalence of toxocariasis has a growing trend in Iran. It could be decreased using education, culture making and giving information to people.

Seroprevalence and risk factors for canine toxocariasis by detection of specific IgG as a marker of infection in dogs from Salvador, Brazil.

Toxocara canis is a highly prevalent worldwide canine nematode responsible for enzootic and zoonotic infections. It is considered to be one of the main agents of human visceral and ocular larva migrans. False negative diagnosis may occur because adult infected dogs with "dormant" larvae may have negative fecal test results since they usually do not shed parasite eggs in their stools. During pregnancy, the larvae become active and infect the offspring through the placenta. A serological test can distinguish infected animals, thus increasing the accuracy of the diagnosis for epidemiological studies and prophylactic purposes. In the present work a serological investigation was carried out to study the risk factors for the acquisition of this infection in 301 dogs inhabiting the city of Salvador, northeast Brazil. A validated questionnaire was applied to the donors and caretakers to assess animal management practices. All dogs were submitted to clinical evaluation and blood collection. Serum samples were analyzed for IgG antibodies against excretory-secretory products of T. canis larvae, used as antigens, by indirect ELISA. The overall seroprevalence of anti-T. canis IgG antibodies was 82.7%. Risk factors for T. canis infection included sex, area of origin within the city, homemade leftover food intake, failure to receive regular vaccination against infectious diseases and lack of preventive anti-helminthic treatment. Most of these risk factors suggest a lack of veterinary care and poverty. The high frequency of seropositivity found for toxocariasis in dogs suggests that results based on parasitological fecal examination could underestimate the actual prevalence of the infection.

Presence of Toxocara canis eggs on the hair of dogs: a risk factor for Visceral Larva Migrans.

The close contact between dogs and humans poses a high risk of exposure to Toxocara canis eggs, which can lead to Visceral Larva Migrans (VLM) syndrome. The objective of this study was to investigate the existence of these nematode eggs on the hair of the perianal region in stray and owned dogs. Samples of hair from 104 dogs of different ages were collected: 25 (24%) were positive for T. canis eggs, with mean of 614.8 eggs per gram of hair. Puppies were responsible for 99% of the total number of eggs. The ages of the animal and hair length were factors that influenced the intensity of the observed eggs. This study showed that dog hair contaminated by T. canis eggs in different developmental stages represents a potential source of VLM infection for humans.

Visceral larva migrans among children in Kütahya (Turkey) and an evaluation of playgrounds for T. canis eggs.

This research was undertaken to determine the seroprevalence of Toxocara canis (T. canis) in children aged 3-13 years in Kütahya, to determine the presence of infected larvae in playground sandboxes, and to obtain a view of the general situation regarding visceral larva migrans (VLM) in the city. The blood sera of 119 children (54 girls, 65 boys) were tested for T. canis IgG, and 9 (7.6%) were found positive. In sand samples collected from playgrounds in nine different residential areas across the city, only two of them, in Inköy and Zafertepe neighborhoods, had T. canis larvae; in total, 3 of the 30 sand samples (10%) contained larvae. It is concluded that the main factor regarding VLM infection in children is outdoor playgrounds or playing areas.

Human toxocariasis: diagnosis, worldwide seroprevalences and clinical expression of the systemic and ocular forms.

Although human toxocariasis ranks among the most common zoonotic infections worldwide, it remains relatively unknown to the public. The causal agents are the nematode parasites Toxocara canis and T. cati, whose definitive hosts are dogs and cats, respectively. When embryonated eggs are accidentally ingested by humans, larvae hatch in the small intestine, penetrate the intestinal wall and migrate, via the bloodstream, to the liver, lungs, muscles, eye and central nervous system. Although most human infections are asymptomatic, two well-defined clinical syndromes are classically recognised: visceral larva migrans (a systemic disease caused by larval migration through major organs) and ocular larva migrans (a disease limited to the eyes and optic nerves). Two less-severe syndromes have recently been described, one mainly in children (covert toxocariasis) and the other mainly in adults (common toxocariasis). Here, the current laboratory diagnosis, epidemiology and main clinical features of both the systemic and ocular forms of human toxocariasis are reviewed. New developments in serological diagnosis are described, the available seroprevalence data are analysed, and the results of relevant clinical studies that have been published over the last decade are explored, to provide an updated overview of this neglected but highly prevalent human infection.

Human toxocariasis: contribution by Brazilian researchers / Toxocaríase humana: contribuição dos pesquisadores brasileiros

In the present paper the main aspects of the natural history of human infection by Toxocara larvae that occasionally result in the occurrence of visceral and/or ocular larva migrans syndrome were reviewed. The contribution by Brazilian researchers was emphasized, especially the staff of the Tropical Medicine Institute of São Paulo (IMT).

São abordados os principais aspectos da história natural da infecção humana por larvas de Toxocara que pode resultar na ocorrência da síndrome de larva migrans visceral e/ou ocular. Deu-se destaque, principalmente, à contribuição de pesquisadores brasileiros e, em especial, aos pertencentes ao quadro do Instituto de Medicina Tropical de São Paulo.

Toxocara seropositivity in Sri Lankan children with asthma.

BACKGROUND: Toxocariasis occurs in humans due to infection with Toxocara canis or T. cati, the nematode parasites of dogs and cats, respectively. The relationship between toxocariasis and asthma is complex, with some studies demonstrating that children with asthma were more likely to be Toxocara seropositive as compared to non-asthmatic children, and other studies indicating no such significant relationship. The aim of the present study was to investigate Toxocara seropositivity and its association with asthma in a selected group of Sri Lankan children. METHODS: Two groups of children were studied: group 1 included 100 children with confirmed bronchial asthma who were on regular inhaler steroid treatment for asthma; group 2 included 96 children who did not have physician-diagnosed asthma or upper respiratory tract infections, attending the same hospital. Diagnosis of Toxocara seropositivity was based on IgG Toxocara Microwell Serum Elisa Kits. Enzyme-linked immunosorbent assay was regarded as positive for a reading of 0.3 optical density units. Stool samples were examined for helminth ova. RESULTS: Toxocara seropositivity in children with asthma was 29% and this was significantly more than Toxocara seropositivity among non-asthmatic children (P < 0.001). Toxocara seropositivity was identified as a significant risk factor of asthma in a univariate model. Eosinophilia was seen in a significantly higher proportion of non-asthmatic and asthmatic children who were Toxocara seropositive. Toxocara seropositivity, however, was not identified as a significant risk factor in a multivariate model. CONCLUSIONS: The analysis confirmed previously identified risk factors for asthma but there was no association between the helminth parasitic infection, toxocariasis and bronchial asthma in children.

Human toxocariasis: contribution by Brazilian researchers.

In the present paper the main aspects of the natural history of human infection by Toxocara larvae that occasionally result in the occurrence of visceral and/or ocular larva migrans syndrome were reviewed. The contribution by Brazilian researchers was emphasized, especially the staff of the Tropical Medicine Institute of São Paulo (IMT).

Seroprevalence of human toxocariasis (visceral larva migrans).

A total of 455 patients who fulfilled the inclusion criteria were included in the study. The enrolled patients were subjected to a questionnaire (including sociodemographic and other risk factors) and thorough clinical examination was done for the patients. Sera were collected from patients and tested for anti-Toxocara IgG antibodies using ELISA. The overall anti- Toxocara seropositive was (7.7%). It was significantly higher than among the randomly selected 30 healthy controls. There were no significant differences between the seropositive and seronegative patients regarding age, sex, educational level and monthly family income of the patient. However, rural residence, poor house, pet's ownership and frequent contact with soil were found to be significant. Patients who had confirmed bronchial asthma were more than 2 times at higher risk of developing toxocariasis (OR, 2.33; 95% CI, 1.09-4.98) than those with other clinical diagnosis (PUO, hepatomegaly or heptosplenomegaly, lymphadenopathy, neurological disorders, gastrointestinal troubles and dermatitis). Patients with eosinophilia were at 149 times greater risk of being Toxocara seropositive compared to those without eosinophilia (OR, 148.7; 95% CI: 53.5-413.3). Multivariate regression analysis showed eosinophilia and contact with soil were the most important predictors of toxocariasis. OD of anti-Toxocara antibodies (ELISA) was significantly positive with eosinophilia level.

[Toxocariasis in children--difficult clinical problem]. / Toksokaroza u dzieci--trudny problem kliniczny.

Toxocariasis in humans is a zoonosis due to the migration of Toxocara canis or T. cati larvae in human body. This review provides basic information on pathology of infection and clinical signs and symptoms of toxocariasis in children. The cases diagnosed in the recent years in central Poland are presented. The disease was recognised accidentally based on the results of laboratory analysis performed for other reasons, when abnormalities suggesting an active helminthiasis were found (eosinophilia, elevated IgE level and/or anemia). The high rate of soil contamination in households of the patients demonstrated elevated risk of infection and reinfection in both, rural and urban areas. Presented data show the need for educational programs which should be implemented for prevention of Toxocara infection in children.

Seasonal prevalence of Toxocara ova in soil samples from public parks in Ankara, Turkey.

This survey was conducted to determine prevalence of Toxocara spp. eggs and seasonal variation of this prevalence in public parks in Ankara, Turkey. A total of 259 sand samples were collected from May 2005 to April 2006 in 40 public parks for determining prevalence. To attain seasonal variation, a total of 696 sand samples were collected from five public parks regularly throughout year. Prevalence of Toxocara spp. and combination of Toxascaris leonina and Taenia spp. was 15.05% and 0.38%. Overall, 45% of public parks were contaminated. There was a seasonal variation in prevalence. Prevalence of Toxocara spp., Toxascaris leonina, and Taenia spp. eggs during summer (4.21%) was lower than during spring (12.64%), autumn (13.21%), and winter (9.77%; p < 0.05). Average number of Toxocara spp. eggs was 2.57 per 50 g of sand, with average dimension of 70.1 mum. In conclusion, prevalence data are consistent with international data reported in other metropolitans. Our results indicate that the public parks in surveyed areas may be a source of toxocariasis. Effective preventive measures should be established.

Prevalence of anti-T. canis antibodies in stray dogs in Mexico City.

UNLABELLED: Toxocara canis is a common intestinal helminth found in dogs. In humans, it is a cause of Visceral Larva Migrans (VLM), a zoonosis rarely studied in Mexico. The aim of this study is to examine, by means of the indirect haemaglutination test (IHAT), the prevalence of antibodies of T. canis in the serum of stray dogs in Mexico City. METHODS AND MATERIALS: 141 stray dog serum samples from three different districts of the city were analyzed: Iztacalco (49), Iztapalapa (49) and Coyoacan (43). In each location three study groups were formed. Group I with 35 dogs (less than a year old), Group II with 91 dogs (ages 1