Immunoglobulin M antibodies are not specific for serodiagnosis of human toxocariasis

Who Let the Dogs Out? Unmasking the Neglected: A Semi-Systematic Review on the Enduring Impact of Toxocariasis, a Prevalent Zoonotic Infection

Toxocariasis remains an important neglected parasitic infection representing one of the most common zoonotic infections caused by the parasite Toxocara canis or, less frequently, by Toxocara cati. The epidemiology of the disease is complex due to its transmission route by accidental ingestion of embryonated Toxocara eggs or larvae from tissues from domestic or wild paratenic hosts. Even though the World Health Organization and Centers for Disease Control classified toxocariasis amongst the top six parasitic infections of priority to public health, global epidemiological data regarding the relationship between seropositivity and toxocariasis is limited. Although the vast majority of the infected individuals remain asymptomatic or experience a mild disease, the infection is associated with important health and socioeconomic consequences, particularly in underprivileged, tropical, and subtropical areas. Toxocariasis is a disease with multiple clinical presentations, which are classified into five distinct forms: the classical visceral larva migrans, ocular toxocariasis, common toxocariasis, covert toxocariasis, and cerebral toxocariasis or neurotoxocariasis. Anthelmintic agents, for example, albendazole or mebendazole, are the recommended treatment, whereas a combination with topical or systemic corticosteroids for specific forms is suggested. Prevention strategies include educational programs, behavioral and hygienic changes, enhancement of the role of veterinarians, and anthelmintic regimens to control active infections.

Toxocariasis in children with digestive system diseases

Toxocariasis is common among children and causes digestive diseases. The aim of the work was to study the development of toxocariasis in children with digestive diseases. The serum levels of specific IgG to Toxocara canis and Ascaris, levels of IL-4 and TNF-α were determined in 63 children. In addition, tests for parasites and a retrospective survey in order to assess sanitation and hygiene practices were conducted. All children were divided into two groups: group I includes 19 (30.2%) patients seropositive for toxocariasis, and group II – 44 (69.8%) children without any parasites. The level of IL-4 was higher in group I (18.0 ± 6.4 pg/ml) than in group II (7.2 ± 2.0 pg/ml) (P < 0.001. While the level of TNF-α did not differ significantly between groups I (4.5 ± 2.1 pg/ml) and II (3.6 ± 1.1 pg/ml) (P > 0.05). A higher incidence of Toxocara was observed among rural residents (78.9%). Children with toxocariasis more often had soil-pica (42.1%), played with dogs (100%), and did not wash their hands (84.2%) compared to the group of uninfected children. It was noted that hygienic habits and place of living contribute to Toxocara canis infection. IL-4 levels were considerably higher in group I than in group II that can be accounted for the host immune response activation, at the same time, the levels of TNF-α did not differ. Children without toxocariasis had also increased levels of IL-4, which may be related to past helminthic infection. Keywords: children., digestive diseases, interleukin-4, toxocariasis, tumor necrosis factor - α

Human Toxocariasis: 2010 to 2020 Contributions from Brazilian Researchers

This is a review of the published contributions made by Brazilian researchers between 2010 and 2020 on the natural history of human toxocariasis and the effects of human toxocariasis on nonhuman paratenic hosts.

Humoral immune response of pigs infected with Toxocara cati

Toxocara cati is one of the causative agents of human toxocariasis. Serological methods are used for diagnosis in paratenic hosts like humans but the humoral immune response triggered by this parasite is unknown. We characterized the humoral immune response to T. cati excretory-secretory antigens (TES) in pigs as animal model during the acute and chronic stages of infection. ELISA and Western Blot techniques were used to determine antibody response. Pigs were experimentally inoculated with 100,000 infective Toxocara cati eggs. Blood was collected at 7, 14, 21 and 28 days post-inoculation (d.p.i.) to assess the acute stage of infection and 90, 120 and 180 d. p.i. for chronic stage analysis. ELISA showed values higher than the cut-off of specific IgM and IgG at 7 d. p.i. with significant differences at 0 and 7 d. p.i. for IgM and at 14, 21 and 28 d. p.i. for IgG in the acute stage. Higher and stable levels were detected in the chronic stage. Western Blot showed bands from 102 to 38 kDa detected by specific IgM and IgG. More immunogenic bands were identified by specific IgG. In the chronic stage of infection a band near 31 kDa was the only band detected by IgM until 150 d. p.i. Specific IgG recognized bands between 102 and 31 kDa. This study demonstrates how the humoral immune response evolves in the acute and chronic stages of infection and provides evidence on the role of the pig as a paratenic host of T. cati.

Seroprevalence Brazil

This chapter presents an overview of the seroprevalence of toxocariasis in Brazil and discusses how this zoonosis is studied, diagnosed, and treated in the Brazilian population. Toxocariasis in humans has a high prevalence in several regions of Brazil; however, this disease is neglected because of lack of knowledge, non-specific clinical signs, and difficult diagnosis. Most studies conducted in Brazil have estimated the prevalence of toxocariasis, i.e., the number of people who presented the disease at any given time. However, a few studies have determined disease incidence (number of new cases in a population at risk) and identified risk factors for Toxocara canis infection. Despite the high seroprevalence, the Brazilian population is not well aware of toxocariasis. Thus, the need of the hour is to raise awareness about this parasitic infection because of its worldwide distribution and potential health risk.

Clinical pathology of larval toxocariasis

Human toxocariasis is a worldwide helminth zoonosis caused by roundworms of the genus Toxocara. Toxocariasis is the most common helminth infection in many countries. Disease caused by Toxocara can be classified into five clinical forms: generalised, neurological, ocular, covert, and asymptomatic. The clinical pathology of toxocariasis largely depends on the form of infection, the intensity of the infection, the larvae localisation, and the age of the host. Because histological and molecular examination of toxocariasis is limited by difficulties in obtaining material to analyse, clinical diagnosis is often based on nonspecific tests, such as the detection of eosinophilia and hyperimmunoglobulinemia E (Hyper-IgE). Specific analysis uses an initial ELISA test to detect anti-Toxocara IgG and requires confirmation for all positive results via Western blot. This strategy does not distinguish between actual and recent infections, making the monitoring of disease a challenge for clinicians. Additional research will be required to distinguish active disease from the presence of recent infection.

Humoral response of mice infected with Toxocara canis following different infection schemes

The study was focused on the dynamics of humoral response to Toxocara canis excretory-secretory antigens (TES antigens) in mice experimentally infected by T. canis L3 larvae in different ways. In particular, we compared the effect of infection with two doses of 1000 larvae vs. repeated infections with a low number of larvae (daily infection with 10 larvae and weekly infection with 100 larvae in the course of 22 weeks). In ELISA, all infections, including both schemes with lower larval doses, elicited significant antibody response. Elevated levels of total IgE and TES-antigen-specific IgM were detected on day 12 after the first infection, followed by IgG and IgG1, and later by IgG3, IgG2a and IgG2b; specific IgE response was not detected. It seems that the high levels of IgM and IgG1 represent the best markers of infection. In addition, gradual increase of IgG2a and IgG2b could help in determination of the infection course. As a byproduct of our work, a new method of infection by repeated drinking of larvae was introduced; it minimizes the pain and discomfort for the experimental mice.