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.

[Toxocariasis in children from a subtropical region]. / Toxocariosis en niños de una region subtropical.

Toxocariasis is present worldwide but people living in areas with sanitary deficiencies are considered at the highest risk of infection, particularly children. The aim of this work was to know clinical and immunological aspects of infantile toxocariasis in a subtropical region in Argentina. For this purpose, 182 children of both sexes, 0-16 years old and with eosinophilia higher than 10%, living in Resistencia City (Northeast Argentina) were studied. Clinical examination, personal and epidemiological data recording, parasitological fecal examination and dosage of Toxocara canis IgG and IgM levels by EIE were performed; all positive sera were confirmed by Western Blot. Out of 182 children, 122 were positive for T. canis-IgG (67.0%); 28.8% lack of potable drinking water at home, 58.8% lack of sewerage facilities, 91.1% referred a close contact with dogs or cats, 30.0% had a history of geophagia and 86.7% lived along streets without pavement. The clinical forms of the infection were: 77.8% asymptomatic, 6.7% ocular larva migrans and 15.5% visceral larva migrans. In 22 children the serological follow up until 18 months after treatment showed 10 children without change in IgG levels, in 11 it decreased but remained high, and in one it increased. There were 19 children with high levels of T. canis-IgM; in 8 it decreased along treatment, in one it remained stable and 10 of them became negative. There was one child considered as a re-infection case. Results highlight the importance that health authorities should assign to this infection in regions with sanitary deficiencies, where toxocariasis is usually not recognized as a relevant public health problem.

Toxocariosis en niños de una region subtropical / Toxocariasis in children from a subtropical region

La toxocariosis está presente en todo el mundo, pero se considera en mayor riesgo a los habitantes de zonas com deficiencias sanitarias y particularmente a los niños. El objetivo de este trabajo fue conocer aspectos inmunológicos y clínicos de la infección infantil en un área subtropical de Argentina, para lo cual se estudiaron 182 niños de ambos sexos de la ciudad de Resistencia (Noreste de Argentina), de 0 a 16 años, con eosinofilia mayor al 10%. Se realizaron exámenes clínicos, encuestas epidemiológicas, exámenes copropa-rasitológicos y dosajes de IgG e IgM anti Toxocara canis por EIE; los sueros positivos fueron confirmados por Western Blot. De los 182 niños estudiados, 122 resultaron seropositivos (67%), 28.8% no contaban con agua potable en su domicilio, 58.8% no tenían cloacas, 91.1% habían tenido contacto con perros y/o gatos, 30.0% tenían antecedentes de geofagia y 86.7% vivían sobre calles sin pavimento. La infección se presentó en forma asintomática en el 77.8% de los casos, como larva migrans ocular en el 6.7% y como larva migrans visceral en el 15.5 % de los casos. En 22 niños el seguimiento serológico post-tratamiento hasta los 18 meses mostró que la IgG se mantuvo estable en 10 casos, en 11 disminuyó pero manteniendo valores elevados y em uno aumentó. Hubo 19 casos con IgM positiva; 8 disminuyeron sus títulos, uno se mantuvo estable y 10 se negativizaron. Hubo un caso de reinfección. Estos resultados reafirman la importancia que las autoridades sanitárias deben asignar a esta infección, particularmente en las regiones carenciadas, en las que habitualmente no se reconoce a la toxocariosis como un problema relevante de salud pública. (AU)

Toxocariosis en niños de una region subtropical / Toxocariasis in children from a subtropical region

La toxocariosis está presente en todo el mundo, pero se considera en mayor riesgo a los habitantes de zonas com deficiencias sanitarias y particularmente a los niños. El objetivo de este trabajo fue conocer aspectos inmunológicos y clínicos de la infección infantil en un área subtropical de Argentina, para lo cual se estudiaron 182 niños de ambos sexos de la ciudad de Resistencia (Noreste de Argentina), de 0 a 16 años, con eosinofilia mayor al 10%. Se realizaron exámenes clínicos, encuestas epidemiológicas, exámenes copropa-rasitológicos y dosajes de IgG e IgM anti Toxocara canis por EIE; los sueros positivos fueron confirmados por Western Blot. De los 182 niños estudiados, 122 resultaron seropositivos (67%), 28.8% no contaban con agua potable en su domicilio, 58.8% no tenían cloacas, 91.1% habían tenido contacto con perros y/o gatos, 30.0% tenían antecedentes de geofagia y 86.7% vivían sobre calles sin pavimento. La infección se presentó en forma asintomática en el 77.8% de los casos, como larva migrans ocular en el 6.7% y como larva migrans visceral en el 15.5 % de los casos. En 22 niños el seguimiento serológico post-tratamiento hasta los 18 meses mostró que la IgG se mantuvo estable en 10 casos, en 11 disminuyó pero manteniendo valores elevados y em uno aumentó. Hubo 19 casos con IgM positiva; 8 disminuyeron sus títulos, uno se mantuvo estable y 10 se negativizaron. Hubo un caso de reinfección. Estos resultados reafirman la importancia que las autoridades sanitárias deben asignar a esta infección, particularmente en las regiones carenciadas, en las que habitualmente no se reconoce a la toxocariosis como un problema relevante de salud pública.

Larva migrans by Baylisascaris transfuga: fatal neurological diseases in Mongolian jirds, but not in mice.

Raccoon roundworms (Baylisascaris procyonis) and other Baylisascaris species cause patent or latent larva migrans (LM) in a variety of mammals and birds, including humans. It is not clear whether LM by Baylisascaris transfuga, roundworms of bears, is associated with clinical neurological disorders. To clarify this issue, ICR and BALB/c mice as well as Mongolian jirds (Meriones unguiculatus) were orally inoculated with 2,000-5,000 embryonated eggs of B. transfuga. In mice, the ascarid caused symptomatic LM of limited extent and duration, whereas the infection was fatal in jirds; i.e., they exhibited general signs such as severe depression and emaciation on days 8-11 postinfection (PI) and died, or they developed progressive and fatal neurological disorders after day 14 PI. Histological examination showed B. transfuga larvae in the brain of all mice and jirds examined, and the larvae collected from them developed to a size comparable with that of B. procyonis. There existed, however, critical differences in host reactions against larvae localized in the brain of mice and jirds; B. transfuga larvae found in mice were surrounded by granulomatous reactions and immobilized, whereas larvae found in jirds were free from any host reaction and mobile, causing extensive malacia.

Strongyloides ratti: the role of interleukin-5 in protection against tissue migrating larvae and intestinal adult worms.

To determine the role of interleukin-5 (IL-5) and eosinophils in protection against Strongyloides ratti, mice treated with anti-IL-5 monoclonal antibody (mAb) were infected with S. ratti larvae. Strongyloides ratti egg numbers in faeces (EPG) in mAb treated mice were higher than those in control mice on days 6 and 7 after inoculation. The numbers of migrating worms in mAb treated mice 36 h after inoculation were higher than those observed in control mice. Intestinal worm numbers in mAb treated mice 5 days after inoculation were higher than those in control mice. These results show that eosinophils effectively protected the host against S. ratti infection by mainly the larval stage in primary infections. The involvement of eosinophils in protection against secondary infection was also examined. Before secondary infection, mice were treated with anti-IL-5 mAb and infected with S. ratti. Patent infections were not observed in either mAb treated or control Ab treated mice. The numbers of migrating worms in the head and lungs of mAb treated mice increased to 60% of that in primary infected mice. Intestinal worms were not found in mAb treated mice or in control mice after oral implantation of adult worms. Eosinophils were therefore mainly involved in protection against tissue migrating worms in secondary infections.

Evaluation of the antigenic similarities of adult-worm extracts from three Gnathostoma species, using sera from Mexican and Japanese patients with Gnathostoma infections.

The antigenic similarities of adult-worm extracts of Gnathostoma spinigerum, G. hispidum and G. doloresi, all of which are important food-borne parasites causing larva migrans in humans, were evaluated. The 40 sera used came from gnathostomiasis cases in Mexico, where G. binucleatum is endemic, or in Japan, where G. doloresi predominates. When used as the fixed antigens in microplate-ELISA, the adult-worm extracts from the three different species of Gnathostoma were found to have equal binding capacity to the Gnathostoma-specific IgG antibodies in the sera of the Mexican and Japanese patients. The correlation coefficients for the optical densities seen in the ELISA, between any two of the three Gnathostoma extracts, were all >0.900. The dose-response curves produced when four sera were tested, in the microplate-ELISA, against the three different Gnathostoma extracts were nearly identical, indicating that the antigens in each of the extracts had similar avidity. Furthermore, the results of competitive-inhibition ELISA indicated that the antigenic specificities of the three extracts were almost identical. An antigen of 40 kDa, which SDS-PAGE and immunoblot analysis revealed to be present in all three extracts, was recognized by the sera from the gnathostomiasis cases. When the sera were investigated by dot-blot ELISA, they also gave similar results whichever extract was used as the antigen source. It appears that, in the serodiagnosis of gnathostomiasis by microplate- or dot-ELISA, each of the three adult-worm extracts would be equally useful, regardless of the causative species of Gnathostoma.

Recombinant expression of Toxocara canis excretory-secretory antigen TES-120 in Escherichia coli.

The gene encoding the excretory-secretory antigen TES-120 of dog ascarid worm Toxocara canis was cloned into the bacterium Escherichia coli. The specificity of the recombinant TES-120 antigen produced by the bacterium was investigated. A total of 45 human serum samples from patients infected with differenthelminthes and protozoa, including 8 cases of toxocariasis, were tested against the recombinant antigens in immunoblot assays. The results from the assays revealed that the recombinant TES-120 antigen reacted with sera from toxocariasis patients only. This highly specific recombinant TES-120 antigen can potentially be used for the development of an inexpensive serodiagnostic assay for human toxocariasis.

Toxocara infestations in humans: symptomatic course of toxocarosis correlates significantly with levels of IgE/anti-IgE immune complexes.

Infestations of humans with the parasitic nematode T. canis are common in both developing and industrialized countries. Most infestations induce a clinically inapparent course of infection, however, severe clinical manifestations, i.e. visceral larva migrans (VLM) or ocular larva migrans (OLM) syndromes are observed. To find an explanation for the different courses of toxocarosis we examined several serological parameters: the expression of (i) specific IgE (Immunoblot, IB), (ii) specific IgG subclasses (IgG1-4, ELISA and the formation of (iii) IgE/anti-IgE immune complexes. Serum samples were obtained from persons with symptomatic (VLM, OLM) and asymptomatic course (AS) of the infestation. As antigen, T. canis excretory/secretory (TES) antigen from L3 larvae was used. Reactivity of IgE against SDS-PAGE separated TES antigens was marginally higher in toxocarosis patients (35%) than in asymptomatics (24%), but without statistical significance. TES-specific IgG (1-4), predominant subclass in all three groups was IgG1, followed by IgG2, IgG4 and IgG3. Subclass IgG1, 2, 4 showed significant differences between patients with VLM associated symptoms and asymptomatic persons (P < 0.001) but not between patients with OLM associated symptoms and asymptomatics. Significantly elevated levels of IgE/anti-IgE immune complexes were detected in sera of patients with symptomatic course of the disease, both VLM and OLM (P < 0.001). Whereas specific IgG may act via antibody dependent cell-mediated cytotoxicity mechanisms, IgE/anti-IgE immune complexes might possibly participate in VLM and OLM by inducing type III hypersensitivity.

Immunological studies on human larval toxocarosis.

The aim of the study was to characterize the antiparasite humoral response in patients with the syndrome of visceral larval toxocarosis. Specific IgG, specific IgE and total IgE immunoglobulins against Toxocara canis excretory/secretory antigens (TES) were detected by using ELISA technique. Antibody response was studied in complete sera as well as in immunoglobulin fractions (IgG and IgE), isolation of which was performed on Protein A Sepharose. It was observed that removal of IgG from the serum samples resulted mostly in increasing levels of anti-Toxocara IgE antibodies what agrees with the theory of the blocking effect of IgG in the immune response. The results demonstrated a little correlation between slgG and slgE in the sera of symptomatic patients, examined in ELISA reaction.

IgE and IgG antibodies in Toxocara canis infection. A clinical evaluation.

The relationship between IgE and IgG antibodies against the metabolic exoantigen of Toxocara canis (TEX antigen) in sera of selected patients with the ocular and visceral form of the disease have been investigated. The specificity and sensitivity of the TEX antigen employed in immunoenzymatic and radioimmunologic assays have been verified. Six hundred and forty-one sera from healthy donors were tested as controls. Our data emphasize the importance of IgE antibodies to ocular larva migrans syndrome and suggest that they play a significant role as a marker of infection. In the visceral form, IgG antibodies seem to mask the presence of IgE by a competitive mechanism toward the same epitopes of the parasite. In fact, IgE antibody titers increase after depletion of IgG from serum.

[Intracerebral granuloma with serum anti-human ascaris antibody: case report].

A 1.5-year-old girl with a convulsion attack due to intracerebral granuloma in the right frontal lobe is reported. Her serum was positive with anti-human ascaris antibody, although no ova of the parasites were detected in the feces. She had grown up intimately with several cats in the home. These findings suggested that the granuloma was due to larva migrans of toxocara, which cross-reacts immunologically with human ascaris. Histological examination of the granuloma revealed no eosinophilic infiltration. No systemic reactions such as eosinophilia and hepatomegaly were found except for elevation of protein in cerebrospinal fluid. These were similar to those of ocular type of toxocara larva migrans.

Cutaneous larva migrans.

Cutaneous larva migrans, or creeping eruption, is an infection caused by certain nematode larvae and, occasionally, fly maggots. After penetrating human skin, the larvae remain in the epidermis and wander aimlessly. The burrows may be intensely pruritic. Systemic reactions may include profound eosinophilia. Oral or topical thiabendazole is effective therapy.

Larva migrans with eosinophilic papular folliculitis.

A patient with typical larva migrans lesions associated with a highly pruritic papular folliculitis is presented. The time course of the evolution and the pathological picture - with local accumulation of lymphocytes, mast cells and eosinophils - mirror a typical thymus-dependent reaction to parasitic infestation. The papular and serpiginous lesions did not respond to the same type of therapy.

[Titers of antibodies for visceral for larva migrans in hospitalized patients]. / Títulos de anticuerpos para larvas migratorias viscerales en pacientes hospitalizados.

The antibody titers for Toxocara and Ascaris were investigated in 49 patients of both sexes and hospitalized because of several pathological conditions, finding an 18% with high titer for Toxocara and 22% for Ascaris. Thirty-seven percent of those with positive titer for Ascaris showed ascaris eggs in the stool. Fifty-five percent of those with positive titer for Toxocara had had contact with dogs and cats and 33%, with dogs only. A correlation among the symptoms, chest x-ray, protein electrophoresis, relative eosinophilia and the elevation of antibodies could not be established; however, the patients with high titers for Ascaris and Toxocara showed an absolute eosinophilia higher than the mean. The diagnosis of systemic infection by larvae of Toxocara and Ascaris can be suspected when there is relative eosinophilia of 10% or more, but its confirmation is still difficult except when finding the parasite "in situ". The serological test can help, but it is not definitive. The recently developed tests are more sensitive and open new expectancies.

Serum and vitreous Toxocara antibody in nematode endophthalmitis.

Five patients had a clinical diagnosis of nematode endophthalmitis and had both a serum and vitreous titer for Toxocara antibody. All five patients had a vitreous titer that was equal to or greater than the serum titer. Serum and vitreous obtained from ten other patients who had no evidence of endophthalmitis did not show this correlation. This study provides the clinician with a further understanding of the meaning of a positive enzyme-linked immunosorbent assay titer as well as an additional area for analysis in selected patients with ocular inflammation.