The One Health approach recognizes that the health of humans, domestic and wild animals, and the wider environment (including ecosystems) are closely linked and interdependent; the term aims to sustainably balance and optimize the overall health of our planet and its inhabitants (1). The approach mobilizes multiple sectors, disciplines and communities at varying levels of society to work together to foster well-being and tackle threats to health and ecosystems, while addressing the collective need for clean water, energy and air, safe and nutritious food, taking action on climate change, and contributing to sustainable development (2). The One Health approach supports global health security by collaboration and communication at the human-animal-environment interface to address shared health threats such as zoonotic diseases, and others. The zoonotic parasitic diseases transmitted by dogs´ feces are considered under this approach, since it interferes with animal and human health, and its propagation generally occurs in the environment (3). In addition, the concept of one health contemplates the consequences produced by climate change (1), a determining factor in the transmission of canine soil-transmitted helminths (cSTH).

The high number of free-roaming dogs found in urban areas can serve as a source of pathogens which may be dangerous to humans; dogs can act as definitive hosts for a high number of parasites (3), some of which are considered zoonotic because they can cause disease in humans. Toxocara canis, Toxocara cati, and Ancylostoma caninum are, respectively, the primary species of zoonotic cSTHs. Other species of non-zoonotic cSTHs could also be present, e.g., Toxascaris leonina, and T. vulpis (4, 5), although they are not dangerous for humans, they do have an effect on animal health. For this reason, epidemiological studies aid in determining the parasitological status of the population, parasite burden and potential risk areas (6).

Toxocariasis is a parasitic disease transmitted usually from dogs and/or cats that are infected with T. canis and T. cati (3), to humans. Hosts include cats, dogs, foxes, coyotes, and wolves. These hosts harbor the nematodes in their guts, shedding the eggs in their feces. The embryonated eggs remain infectious for years outside the host. In the wild, carnivorous animals such as cats and dogs consume infected meat or simply soil containing the eggs, and the parasite persists in their gut. Additionally, transplacental transmission has been documented in dogs and cats (7, 8).

In general, individuals infected with these species are asymptomatic, but some develop clinical syndromes which include visceral larva migrans (VLM), ocular larva migrans (OLM), neurotoxocariasis (NT) and covert/common toxocariasis (CT) and can associate with allergic, neurological and/or visual disorders, or cognitive and intellectual deficits in children (9). Recent epidemiological research has estimated that ~1.4 billion people worldwide (10), particularly in subtropical and tropical regions, are infected with, or exposed to Toxocara species, indicating that human toxocariasis is a neglected tropical disease (NTD). Diagnosis in humans is based on clinical, epidemiological, and serological data. Indirect IgG ELISA is a widely used serological method for toxocariasis and western blots can be used to confirm positive ELISA findings to reduce false-positive results (11).

Embryonated Toxocara spp. eggs in the environment are considered as the most important source of human toxocariasis. These eggs, however, are also a source of infection for definitive and paratenic hosts (12). To become infective, Toxocara spp. eggs need specific conditions of temperature and soil (13, 14), which are present in public squares and parks from different tropical and subtropical countries (15). In this study, canine fecal samples from different parks and squares from San Juan Province, Argentina, were analyzed. The samples were collected during the four seasons (autumn, winter, spring, and summer) in each selected area, with the aim to estimate the association between seasons, weather, presence of cSTH eggs and zoonotic risk.

Through the sampling of fecal canine samples collected from 34 of the main urban parks and squares of the City of San Juan (San Juan, Argentina), the presence of different cSTH species was detected, including Toxocara spp., which is a zoonotic parasite that poses a risk to humans. The overall prevalence of cSTH found in this study was 8.9%, which is lower than the prevalence reported in other studies from urban areas in Argentina (33–36), and similar to the prevalence reported in Ushuaia (37) (Supplementary Table 1). Herein, the most prevalent cSTH was T. vulpis, while in other studies the most prevalent species found was A. caninum (33, 35, 38–40). The same pattern was observed in other countries such as Australia and Nigeria, where this hookworm species was the most prevalent (41, 42). In some of these studies, infection by protozoan species was higher than helminth infections (37); in this study, protozoan parasites were not detected, although the modified Ziehl-Neelsen technique (43), which is more sensitive, was not used.

In this study, T. vulpis was the most prevalent cSTH, this could be due to the longer survival time of eggs of this species in the soil; this might be increasing the chances for dogs that frequent the parks/squares to become reinfected (44). Moreover, T. vulpis has a prepatent period of 3 months, therefore antiparasitic treatment should be routinely repeated at monthly intervals to kill all the worms as they mature and prevent contamination of the environment (3). On the other hand, Toxocara spp. and T. leonina require only a few weeks to mature (1–2 months), and with a second dose of anthelmintic administered 2 or 3 weeks after the first one, the dogs would be free of all the worms. Considering that the samples analyzed herein are from the environment and that the status of each definitive host is unknown, we could assume that canine deworming is either not being performed or not given in periodic intervals.

Unfortunately, since fecal environmental samples were used, the association with characteristics of the dogs themselves (i.e., age, free-roaming or kept, underlying conditions, among others) (45) and with the conduct of care of the owners (i.e., antiparasitic treatment) (46) could not be considered. Moreover, the setting where this study was conducted was urban and the prevalence and variety of parasites found might be greater in rural areas where there is also exposure to other animals (4, 47, 48).

Additionally, differences in prevalence could also be due to the climatic and soil conditions of San Juan, given that it is an area with very low precipitation and other studies have shown that the average amount of rainfall was found to be strongly associated with the environmental contamination of parks with cSTH (41). Through the analysis of the association between the presence of Toxocara spp. and environmental characteristics, in this study, the regression analysis revealed that shadow significantly contributes to the increased prevalence of the parasites as measured by the TMI, as previously observed in other studies (28–32). The presence of trees and their shadows, along with other factors like irrigation and management of the park (not considered in this study), could create an ecological urban niche for the parasites to develop in the soil regardless of the general dry environment of San Juan. The significantly higher prevalence of Toxocara spp. observed in the autumn coincides with increased air humidity, lower wind speed and sun radiation, these environmental conditions could potentially facilitate transmission of Toxocara spp. eggs. This was confirmed under laboratory conditions in a previous study (32). In addition, other studies have shown that Argentina and Brazil have optimal humidity conditions for the development of Toxocara spp. eggs (49–51). Nevertheless, extreme temperatures (high or low) are also important as they can lead to desiccation of eggs and larval stages or arrested development of infective stages in the environment (52).

The cSTH species found herein were not homogeneously spread throughout the city, and there were areas that had conditions that were more appropriate for the transmission from one dog to another. In general, the cSTH detected in this study were found in the areas surrounding the Capital Department. Nonetheless, when analyzing per species, the prevalence of Toxocara spp. was greater than expected within the Capital Department, which is the most densely populated. These areas with the detection of a higher prevalence of Toxocara spp. than expected may be used to guide public health measures for screening of antibodies specific for Toxocara spp. in humans, especially children, given that Toxocariasis is a silent disease that could be acquired during infancy and have severe consequences (9). Further studies could be conducted to determine the possible risk factors associated with these areas (53). Unfortunately, evaluation of the egg’s viability and ability to become infective (54) was not performed, future studies must be conducted to evaluate these, given its implications on the risk to public health.

The regular administration of anthelmintic treatments and the promotion of responsible dog ownership, including picking up dog feces and hand hygiene are important measures which need to be adopted to minimize environmental contamination with Toxocara spp. and other STHs (41). Multidisciplinary research, formulated under “one health approaches” can deliver reinforced tools for exploring zoonotic parasites, including cSTHs (46).

Due to the low number of public squares and parks studied herein (N = 34), future studies with a higher number of squares and public parks should be conducted to improve the correlations analysis.

This is the first study in San Juan, Argentina to describe the presence of cSTH parasite species in public areas. The specific localization of squares and parks infected with cSTH eggs aim to provide information to design strategies to lower the cSTH infection burden in dogs and to provide information to direct serological screening of the human population, specifically for Toxocara spp. Given the zoonotic nature of these cSTHs we hope this information will help to reinforce activities of control programs, focusing on the “One Health” approach.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

HA, VP, and MP: conceptualization. MP, HA, LS, PA, and VP: methodology. HA and MP: formal analysis. HA, PA, and SM: investigation. HA, LS, and MP: data curation. GG: statistical analysis. LS: spatial analysis. HA, GG, and LS: writing—original draft preparation. MP: writing—review and editing. VP and MP: supervision. All authors contributed to the article and approved the submitted version.

This work was supported by Fundación Mundo Sano and Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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