Prevalence of Toxocara and Toxascaris infection among human and animals in Iran with meta-analysis approach.

BACKGROUND: Toxocariasis is a worldwide zoonotic parasitic disease caused by species of Toxocara and Toxascaris, common in dogs and cats. Herein, a meta-analysis was contrived to assess the prevalence of Toxocara/Toxascaris in carnivore and human hosts in different regions of Iran from April 1969 to June 2019. METHODS: The available online articles of English (PubMed, Science Direct, Scopus, and Ovid) and Persian (SID, Iran Medex, Magiran, and Iran Doc) databases and also the articles that presented in held parasitology congresses of Iran were involved. RESULTS: The weighted prevalence of Toxocara/Toxascaris in dogs (Canis familiaris) and cats (Felis catus) was 24.2% (95% CI: 18.0-31.0%) and 32.6% (95% CI: 22.6-43.4%), respectively. Also, pooled prevalence in jackal (Canis aureus) and red fox (Vulpes vulpes) was 23.3% (95% CI: 7.7-43.2%) and 69.4% (95% CI: 60.3-77.8%), correspondingly. Weighted mean prevalence of human cases with overall 28 records was 9.3% (95% CI: 6.3-13.1%). The weighted prevalence of Toxocara canis, Toxocara cati, and Toxascaris leonina was represented as 13.8% (95% CI: 9.8-18.3%), 28.5% (95% CI: 20-37.7%) and 14.3% (95% CI: 8.1-22.0%), respectively. CONCLUSION: Our meta-analysis results illustrate a considerable prevalence rate of Toxocara/Toxascaris, particularly in cats and dogs of northern parts of Iran. The presence of suitable animal hosts, optimum climate and close contact of humans and animals would have been the reason for higher seroprevalence rates of human cases in our region. Given the significance clinical outcomes of human Toxocara/Toxascaris, necessary measures should be taken.

Cross-reactivity of Toxocariasis with Crude Antigen of Toxascaris leonina Larvae by ELISA.

Roundworms of Toxocara canis and Toxascaris leonina are common gastrointestinal helminths of canids over the world. Humans are infected with T. canis larvae through ingestion of infective eggs in contaminated environments or larvae by consumption of raw or uncooked meat or livers. Recently, patients of clinically diagnosed toxocariasis are increasing and require correct diagnosis in Korea. The present study investigated serological cross-reactivity between crude antigens of T. canis (TCLA) and T. leonina (TLLA) larvae. We collected serum specimens from 177 toxocariasis patients who were clinically suspected in the Seoul National University Hospital and 115 healthy controls. An ELISA method for toxocariasis was used to evaluate diagnostic efficacy of TLLA for serodiagnosis of human toxocariasis. The IgG ELISA using TLLA gave 14 (14.3%) positives of 98 TCLA positive specimens among 177 suspected toxocariasis patients. Most of them showed high absorbances with TCLA. In conclusion, there is a partial cross reaction between serum specimens of toxocariasis and TLLA.

Alteration of cytokine production during visceral larva migrans by Toxascaris leonina in mice.

To determine alteration of immune responses during visceral larva migrans (VLM) caused by Toxascaris leonina at several time points, we experimentally infected mice with embryonated eggs of T. leonina and measured T-helper (Th) cell-related serial cytokine production after infection. At day 5 post infection (PI), most larvae were detected from the lungs, spleen, intestine, and muscle. Expression of thymic stromal lymphopoietin (TSLP) and CCL11 (eotaxin) showed a significant increase in most infected organs, except the intestine. However, expression of the CXCL1 (Gro-α) gene was most highly enhanced in the intestine at day 14 PI. Th1-related cytokine secretion of splenocytes showed increases at day 28 PI, and the level showed a decrease at day 42 PI. Th2-related cytokine secretion of splenocytes also showed an increase after infection; in particular, IL-5 level showed a significant increase at day 14 PI, and the level showed a decrease at day 28 PI. However, levels of Th17-related cytokines, IL-6 and IL-17A, showed gradual increases until day 42 PI. In conclusion, Th1, Th2, and Th17-related cytokine production might be important in immune responses against T. leonina VLM in experimental mice.

Alteration of Cytokine Production during Visceral Larva Migrans by Toxascaris leonina in Mice

To determine alteration of immune responses during visceral larva migrans (VLM) caused by Toxascaris leonina at several time points, we experimentally infected mice with embryonated eggs of T. leonina and measured T-helper (Th) cell-related serial cytokine production after infection. At day 5 post infection (PI), most larvae were detected from the lungs, spleen, intestine, and muscle. Expression of thymic stromal lymphopoietin (TSLP) and CCL11 (eotaxin) showed a significant increase in most infected organs, except the intestine. However, expression of the CXCL1 (Gro-alpha) gene was most highly enhanced in the intestine at day 14 PI. Th1-related cytokine secretion of splenocytes showed increases at day 28 PI, and the level showed a decrease at day 42 PI. Th2-related cytokine secretion of splenocytes also showed an increase after infection; in particular, IL-5 level showed a significant increase at day 14 PI, and the level showed a decrease at day 28 PI. However, levels of Th17-related cytokines, IL-6 and IL-17A, showed gradual increases until day 42 PI. In conclusion, Th1, Th2, and Th17-related cytokine production might be important in immune responses against T. leonina VLM in experimental mice.

Immunization of proteins from Toxascaris leonina adult worm inhibits allergic specific Th2 response.

Recently, the influence of parasitic infections on the incidence of allergic diseases has become the focus of increased attention. In order to ascertain whether parasite-derived proteins could inhibit the allergic specific Th2 response, we applied excretory-secretory protein (Tl-ES) or total protein (Tl-TP) of the adult worm Toxascaris leonina to asthma model mice prior to or simultaneously with OVA challenge, after which we assessed the OVA-specific Th2 responses. The group subjected to immunization with Tl-ES and Tl-TP (immunized group) evidenced a thinning of the bronchial epithelial and muscle layer, a disruption and shedding of epithelial cells, a reduction in the number of goblet cells, and a reduction in mucus production as compared to the group treated with Tl-ES coupled with OVA challenge (challenge with OVA groups) and the OVA-induced asthma group. The administration of Tl-ES and Tl-TP, regardless of injection time, was shown to inhibit the recruitment of inflammatory cells into the airway, and in particular, macrophages, neutrophils, and lymphocytes were significantly reduced as the result of the parasite proteins. However, the total number of eosinophils was slightly reduced as the result of the administration of parasite proteins. Sensitization and OVA challenge was shown to accelerate the secretion of Th2 cytokines (IL-4 and IL-5) within the lung, but in the immunized groups, those levels were lower. The administration of Tl-TP and OVA challenge group also evidenced a significant reduction in IL-4 levels as compared to the OVA-challenged group. The concentrations of Th2 cytokines in the Tl-ES and OVA challenge group were more similar to those observed in the OVA-challenged group. The concentration of IL-10 and TGF-beta in the lung was decreased substantially in the OVA-only challenge group, but the Tl-TP immunized group exhibited significantly induced IL-10 cytokine. OVA-specific IgG2a, IgG1, and IgE levels in the immunized groups were significantly lower than those detected in the OVA-challenged group. In conclusion, parasite-derived protein is able to inhibit OVA-specific Th2 responses, and in particular, immunization with parasite proteins exerts a more profound protective effect than is seen with the treatment of allergic reactions. The results of our study are encouraging in terms of our further understanding of the molecular basis of immune evasion by nematodes.

Characterization of antigenic property of Toxocara canis and Toxascaris leonina adults and larvae through immunodiagnostic electrophoresis (SDS-PAGE) and western blot technique.

Differential molecular studies were performed by sodium dodecyle sulphate polyacrylamide gel electrophoresis--SDS-PAGE--between somatic antigen of Toxocara canis and Toxascaris leonina, adults and larvae, recovered from dogs. SDS-PAGE of both adults somatic antigen showed two closely similar bands (90.00, 91.95 KDa and 69.25-70.56 KDa). Each parasite had characteristic bands clustered in different molecular weights. While for their larval antigen, T. canis showed a very different antigenic profile when analysed in comparison to T. leonina antigen except at one band (66.85-66.89 KDa). The Western blot analysis showed four prominent bands represented immunoreaction between the separated somatic antigen of T. canis adults and experimentally immunized rabbit with the corresponding parasite (125.37, 117.73, 90.00 and 69.25 KDa). While separated antigen of T. leonina adults immune reacted with the corresponding hyperimmune rabbit sera at 119.04, 91.95 and 70.56 KDa. The Western blot showed cross reactive immune bands between T. canis and T. leonina adults somatic antigen at two bands (90.00, 91.95 KDa and 69.25-70.56 KDa). The polypeptide bands reacted at 125.37 KDa and 117.73 KDa can be used as specific finger print for T. canis adults while that at 119.04 KDa was specific for T. leonina adult worm.

Cross-reactions of sera from Toxascaris leonina and Ascaris suum infected mice with Toxocara canis, Toxascaris leonina and Ascaris suum antigens.

The ELISA method using larval ES products and homogenized Toxocara canis, Toxascaris leonina and Ascaris suum adult worms extract, was used to determine the possible cross-reactions in BALB/c and C57BL/10 mice inoculated with embryonated eggs or adult worms extract of T. leonina of T. leonina or A. suum in single and multiple doses. When we used sera of mice infected with embryonated eggs of T. leonina against different heterologous Ag, no cross-reactions against T. canis ES and A. suum ES Ag were observed using a single dose. Similarly, in multiple doses no response against T. canis ES Ag was observed. In mice inoculated with adult worms extract of T. leonina cross-reactions with T. canis ES and A. suum ES Ag did not occur. Sera from BALB/c mice infected with embryonated eggs of A. suum, was tested using ES Ag from both A. suum and T. canis and no reactions were observed. This fact confirmed the resistance of this murine strain to A. suum embryonated eggs. When we used sera of susceptible C57BL/10 mice infected against different heterologous Ag, we observed no cross-reactions against T. canis ES Ag. In the case of both BALB/c and C57BL/10 and C57BL/10 mice immunized with a single dose of A. suum adult crude extract no cross-reactions were seen against ES T. canis Ag and with sera from C57BL/10 mice against ES T. leonina. These facts confirmed the specificity of the ES T. canis Ag.

Cross-reactions of sera from Toxocara canis-infected mice with Toxascaris leonina and Ascaris suum antigens.

The ELISA method using larval excretory-secretory (E/S) products and homogenized Toxocara canis, Toxascaris leonina and Ascaris suum adult worm extract were used to determine possible cross-reactions in BALB/c and C57BL/10 mice, inoculated with embryonated eggs or adult worm extract of T. canis in single and multiple doses. When we used sera of mice infected with embryonated eggs of T. canis against different heterologous antigens, we observed no cross-reactions in BALB/c mice against A. suum E/S and adult worm extract antigens with a single dose. In multiple doses this was absent too against T. leonina adult worm extract in BALB/c mice, and in both strains against A. suum E/S and adult worm extract. In BALB/c mice inoculated with adult worm extract of T. canis we did not observe cross-reactions with A. suum E/S antigen with both inoculation doses. In the remainder of the experiments, we observed cross-reactions of different intensities.

Comparison of isolates and species of Toxocara and Toxascaris by biosynthetic labelling of somatic and ES proteins from infective larvae.

Infective-stage larvae of three different isolates of Toxocara canis were intrinsically ([35S]methionine) labelled in culture, to determine the presence of similarities or differences in the somatic and ES antigens expressed between larvae derived from different hosts and different geographical regions. Two other closely related ascaridids, Toxascaris leonina which infects cats and dogs, and Toxocara vitulorum (Neoascaris vitulorum) which infects cattle, were also compared to T. canis larvae by this method. Overall comparisons were made by 1- and 2-dimensional electrophoresis, while immunological cross-reactivities between the different species were analysed by radio-immunoprecipitation. Our results show that extensive physicochemical characteristics are shared between T. canis isolates, both from different hosts and different geographical locations. A substantial overlap was revealed when T. canis and T. vitulorum antigens were compared, whereas Toxascaris was found to produce a distinct antigen profile: this result was independent of whether methionine- or Iodogen-labelled products were being considered. Antigen recognition by polyclonal antibodies raised to all three species and to the cat ascaridid Toxocara cati, revealed considerable cross-reactivities. The cross-reactions were especially prominent between the Toxocara species, a fact further substantiated when reactivity of T. canis ES-specific monoclonal antibodies were tested against T. leonina and T. vitulorum antigens. The ES antigens of T. leonina were not recognized by the T. canis monoclonals, whereas the majority of these antibodies precipitated antigens of T. vitulorum. One which did not react with T. vitulorum was monoclonal antibody Tcn 2, indicating its species-specific reactivity and therefore its potential for the specific diagnosis of human toxocariasis.

Dynamics of antibody production in mice infected with Toxascaris leonina Linstow, 1909.

Using counterimmunoelectrophoresis and ELISA tests the dynamics of antibody production in serum of mice experimentally infected with Toxascaris leonina was studied. The production of antibodies using both tests has already been detectable in serum of mice from 7 days post infection (DPI) and their level persisted till the end of the experiment, i.e. till 77 DPI. The most positive were reactions of sera with Antigens 1 and 3.

Comparison of counterimmunoelectrophoresis with indirect haemagglutination test in the detection of antibodies in rabbits experimentally infected with various species of ascarids.

Counterimmunoelectrophoresis (CIEP) and indirect haemagglutination (IHA) were used for the detection of antibodies in 437 sera of rabbits experimentally infected with Ascaris suum, Toxocara canis and Toxascaris leonina. CIEP showed 44.0-52.3% positivity in A. suum, 25.5% in T. canis and 19.7-29.2% in T. leonina infection, whereas the positivity detected by IHA was 59.8-90.2% in A. suum, 44.8% in T. canis and 59.6% in T. leonina infection. A comparison of the two tests reveals that CIEP is a suitable, rapid and simple method for orientation examinations in ascarid infections.

Toxocara infection in pigs. The use of indirect fluorescent antibody tests and an in vitro larval precipitate test for detecting specific antibodies.

An in vitro larval precipitate test using second-stage Toxocara canis larvae and an indirect fluorescent antibody (IFA) test employing cuticles of T. canis larvae as antigen were evaluated using antisera produced in pigs experimentally infected with T. canis, T. cati, Ascaris suum, Toxascaris leonina and Parascaris equorum. The former test was both specific and sensitive and is suggested as a reliable and simple method of detecting Toxocara antibodies in pigs. The latter test was considered unsuitable because of cross-reactions that occurred when sera from pigs infected with other ascarids were tested. An IFA test for Ascaris antibodies, employing cuticles of A. suum larvae as antigen, is described. The degree of specificity of this test suggests that it may be of value in the detection of antibodies to Ascaris in pigs under natural conditions.