The estimated population of the study area is approximately 5,000 people. Recruitment was conducted through informational posters at the health center and community meetings. A total of 157 residents participated, providing informed consent for blood and stool sample collection. While all participants provided blood samples, 16 individuals did not return stool samples, resulting in a total of 141 stool samples collected. A survey was carried out on each participant to collect information on their socioeconomic conditions, potentially linked to parasite prevalence (survey details are provided in Supplementary material). Participants, who owned dogs as pets, were offered a diagnostic test to identify intestinal parasites in their dogs.

All samples were collected at the health center and then transported to the Institute of Parasitology of the Universidad Austral de Chile. For the diagnosis of parasitosis in fecal samples, each participant received a container with 35 mL of PAF (Phenol, Alcohol, and Formaldehyde) fixative and a 15 mL conical-bottom tube with 8 mL of 70% ethanol, along with oral and written instructions for proper sample collection. Participants deposited fecal samples from three different days (every other day) into PAF containers (21). A single sample from the final collection day was placed in the 70% ethanol tube for molecular analysis. Containers with PAF were stored at 2–5°C, while the ethanol tube were stored at −20°C until processing. To obtain serum, blood samples were collected by health center staff by venipuncture in tubes without anticoagulant and centrifuged at 3,000 rpm for 5 min. The serum was extracted and then frozen at −20°C until the ELISA test was performed.

Fecal samples, from both human and dog, were processed using the Modified Burrows Method (PAFS) (21) and following the recommendations of the National Reference Laboratory of the Instituto de Salud Pública de Chile.

A commercial ELISA kit (NovaLisa from Novatec) was used to detect IgG anti-Toxocara canis antibodies. The test was performed according to the manufacturer’s instructions. Indeterminate results were sent for confirmation to the national reference laboratory at the Institute of Public Health, Santiago, Chile.

Ten human stools samples, previously diagnosed with Blastocystis sp. or with G. duodenalis by microscopy, were further analyzed using next-generation sequencing (NGS) at the Austral-OMICS laboratory (specialized unit for supporting scientific research). Samples were selected to represent each of the sampling sectors. For G. duodenalis the β-Giardina gene was targeted, while for Blastocystis sp. the 18rRNA gene was analyzed. A detailed description of the technique is provided in Supplementary material.

Soil samples were collected from parks A, B, and C during two periods: October 2021 (spring) and May 2022 (autumn). In each park, areas of interest were defined as two meters perimeter the children’s playgrounds, as these locations have the highest presence of both humans and dogs. Within these sampling areas, three parallel imaginary lines were drawn, spanning from one end to the other. Sampling points were established at 1 m intervals and 5 g soil sample was collected from a depth of 3–5 cm. The collected soil samples were dried for 48 h at room temperature. The whole sample was then sieved with a grid into a metal container and processed using the zinc sulfate method (22, 23). For the physicochemical analysis, 300 g of soil from each sector was collected in a re-sealable plastic bag. In the case of parks A and B parks, one sample was taken for each study (parasitological and physicochemical), while in park C there were two soil types, therefore, one sample was taken from each soil type (C1 and C2).

The physicochemical analysis of the soil was carried out by the Forest Soil and Nutrition Laboratory of the Universidad Austral de Chile. The parameters measured were pH, % Total Carbon (TC), % Soil Organic Matter (SOM) and % Humidity.

A walking tour of each of the streets and passageways in the sector was conducted twice, in October 2021 (spring) and May 2022 (autumn). All samples of dog feces that were not dry for collection were obtained in each sector. For each sample, 5 g of stool were placed in containers with 15 mL of PAF fixative. Samples were then transported to the laboratory and processed using the Modified Burrows Method (PAFS) (21).

Participants who agreed to include their dogs in the research received a container with 15 mL of PAF fixative and were asked to collect 5 grams of feces. Finally, the collected stool samples were processed by the Modified Burrows Method (21).

A descriptive analysis of the data was performed using Chi-Square and a statistical significance level of 0.05 was established. To determine the magnitude of the observed relationship, the Odds Ratio (OR) was used, and a 95% confidence interval (CI) was established. Graphpad Prism 9 and IBM SPSS Statistics (Statistical Package for the Social Sciences) were used in the analysis of the data obtained.

One hundred forty-one people participated in the study, of whom 67.4% were women. The participants age ranged from 5 to 89 years, with an average age of 64 years, with most of them (76.6%) between 50 and 79 years old. In terms of educational level, 35.5% completed basic education (8 years), 47.5% completed secondary education (12 years) and 10.6% completed high education (more than 12 years). In addition, 65.3% of the participants are retired or housewives. In terms of income, 95.8% of the participants declare a monthly income less than or equal to US$ 660. Ninety-two point 9 % of the population declares to have at least one chronic non-transmissible disease. Also, 89.4% of the participants report having consumed only drinking water in the last year and 97.9% having access to sewerage.

The overall prevalence of parasites was 27.7% (CI: 20.9–35.6) (Figure 2A). Sixty-one point 5 % of positive patients had 1 parasitic agent, 33.3% had two parasitic agents, and 5.1% had 3 or more (Figure 2B). Among the positive patients, 61.5% correspond to women. The age distribution of patients with parasites shows that the majority correspond to patients over 60 years of age (Figure 3).

In terms of prevalence by species or taxa, the most prevalent parasites were Blastocystis sp. with 22% (CI: 15.9–29.5), followed by Ent. coli with 11.3% (CI: 7.1–17.6) and Endolimax nana with 3.5% (CI: 1.5–8.0) (Figure 4A). As previously mentioned, in our study almost 40% of polyparasitism was observed (Figure 2B). Thus, Figure 4B described in detail the frequency of observation of each parasite related to other parasites taxa. Blastocystis sp. is the most frequently described singly (19 times) but also accompanied by Ent. coli (10 times).

Comparing each of the components of the socioeconomic survey with the presence of parasites, it was found that living with pets is a statistically significant factor (χ² = 4.9, p = 0.03). Thus, having pets increases the risk of harboring parasites almost threefold (OR: 2.9, [1.1–7.5]). No statistically significant differences were observed in any of the other socioeconomic factors studied (p > 0.05).

A total of 157 human serum samples were analyzed. The average age of the participants was 61 years, with a maximum of 89 years and a minimum of 4 years. Among them, 110 were women and 47 were men.

There was a global prevalence of 33% of anti-Toxocara canis IgG. Thus, 52 participants were positive, 101 negative and four undetermined. The undetermined samples were sent to the Institute of Public Health of Chile, and due to the detection limitations of the ELISA technique used, the result remained indeterminate.

Figure 5 shows the age distribution of the participants who were reactive to the ELISA, with the range between 51 and 80 years showing the highest prevalence with 85% of the cases.

A statistically significant difference was found between the prevalence of anti-Toxocara canis IgG and the educational level of the participants (p = 0.03), with a lower risk of being serologically reactive at a higher educational level (OR: 0.5; CI: 0.2–0.9).

No statistically significant differences were observed based on gender, income, chronic disease status, outdoor activities, symptoms, living with minors, pet ownership, or having a garden (p > 0.05). Similarly, there were no significant associations between anti-Toxocara canis IgG prevalence and prior parasite history, treatment, or living with treated individuals (p = 0.83), nor with dog ownership (p = 0.99) or enteroparasite presence (p = 0.65).

The samples analyzed by NGS correspond to samples positives by microscopy to G. duodenalis or Blastocystis sp. In 8 of the 10 samples, there was amplification, and the resulting sequences were compared with database built based on the sequences available in NCBI. For both parasites only one subtype was identified in each sample.

Three samples were sequenced for G. duodenalis, in two of them the A2 assembly was identified (~140,000 reads each). In the third, G. muris was identified, a parasite usually described in rodents, but with a very low number of reads (9,364 reads). However, due to the technique used in both samples identified as G. duodenalis assembly A2, a marginal number of reads corresponding to G. duodenalis assemblies D and E was also observed (~130 reads each), both corresponding to less than 0.1% of the total reads (Figure 6A).

For Blastocystis sp. six samples were sequenced with a total of 800,087 reads. Subtype identification was as follows: two samples with subtype 1; two samples for subtype 1, one sample with subtype 2, two samples with subtypes 3 and one sample with subtype 4 (Figure 6B).

A total of 8 soil samples were collected, 4 in spring and 4 in autumn. Of these, 7 contained at least 1 parasitic element. They showed a diversity of parasitic elements composed exclusively of nematode eggs. In spring, eggs of Trichuris vulpis, Toxocara sp. and Toxascaris leonina were found. While, in autumn, eggs of T. vulpis, Toxocara sp. and Uncinaria stenocephala were observed (Figure 7).

The results of the physicochemical analysis of soil samples indicate that parks A and B maintained similar characteristics in total carbon (TC) (%), soil organic matter (SOM) (%) and humidity (%) across both sampling periods. However, the pH in park A increased from 5.2 in spring to 6.3 in autumn. In contrast, significant changes were observed in park C, especially in C1, where TC (%) increased from 4.3% in spring to 8.2% in autumn, and SOM (%) increased from 7 to 14% during the same period.

A total of 180 samples were collected, of which 44.4% (CI: 37.4–51.7) showed the presence of parasites. The seasonal variations show that in spring there were 48.4% and in autumn 40% positive samples. The percentage of positive samples analyzed by sector and per season varied from 16.7% (sector B in autumn) to 79.2% (sector A autumn). In spring no statistically significant difference was observed by the chi-square test (χ²) between the frequency of observation of parasitic elements in dog feces and the sector in which the samples were collected (p > 0.05). In autumn a statistically significant difference was observed using chi-square (χ²) between the frequency of observation of parasitic elements in dog feces and the sector in which the samples were collected. (A vs. B p < 0.05, χ² = 18.8 and A vs. C p < 0.05, χ² = 14.2). Additionally, it was observed using the Odds Ratio (OR) that in sector A there was 19 times more probability of finding a positive dog stool sample compared to sector B (OR: 19; CI: 4.4–81.6) and 8.9 times more than in sector C (OR: 8.9; CI: 2.7–30.2). Finally, by performing a chi-square test (χ²), it was observed that only in sector A there is a statistically significant difference between the season of sampling (spring or autumn) and the percentage of positive samples (p < 0.05, χ² = 4.0). This shows that the spatial distribution of parasites is not homogeneous within the study area.

The parasite most present in these samples was T. vulpis with 27.2% (CI: 21.2–34.1) of positive samples, followed by U. stenocephala with 15.6% (CI: 11.0–21.6). It is important to point out, due to their zoonotic importance and the clinical presentation in humans, the presence of Toxocara sp. in 4.4% (CI: 2.3–8.5) and G. duodenalis in 1.7% (CI: 0.5–4.8) of the collected samples. Most of the parasitic elements were observed in both spring and autumn, except for T. leonina and Capillariidae gen. sp. which were only observed in spring (Figure 8).

According to the sector, T. vulpis and U. stenocephala were the most frequent species in all sectors (A, B and C). In Sector A, T. vulpis was found in 30.6% (CI: 19.5–44.5) and U. stenocephala in 18.4% (CI: 10.0–31.4) of the samples. In Sector B, T. vulpis was found in 32% (CI: 17.2–51.6) and U. stenocephala in 12% (CI: 4.2–30.0) of the samples. In Sector C, T. vulpis was found in 28.6% (CI: 13.8–50.0) and U. stenocephala in 19% (CI: 7.7–40.0) of the samples. All details about the frequency of parasites found for each sector and period are shown in Supplementary material. When performing the chi-square test (χ²), no statistically significant difference was observed between the total positive samples in spring versus the total positive samples in autumn (χ² = 1.3; p > 0.05) nor between the sample collection season (spring or autumn) and the frequency of any parasitic species (p > 0.05).

A total of 38 samples were collected from dogs with owners. A prevalence of 25.6% (CI: 14.6–41.1) was described. Four zoonotic species were observed D. caninum (2.6%; CI: 0.1–13.2), G. duodenalis (2.6; CI: 0.1–13.2), T. vulpis (15.4%; CI: 7.2–29.7) and T. leonina (5.1%; CI: 0.9–16.9) (Figure 9).

No statistically significant difference was found between the presence of parasites and whether pets go outside (χ² = 3.3, p = 0.07), nor between the presence of parasites and deworming within the last 6 months (χ² = 0.3, p = 0.57).

In Chile, recent studies on parasites in the general population are scarce, with the last study in the Los Rios region conducted over 20 years ago. The present study provides an update of the epidemiological data for intestinal parasitosis in humans. Thus, the global prevalence of intestinal parasitism observed in this study was 27.7%, a lower prevalence compared to previous studies in Chile, such as the 1997 study in Santiago, which reported a prevalence of 37.7% (24).

Blastocystis sp. was the most prevalent agent identified (22%), followed by Ent. coli (11.4%). In contrast to our results, a previous study carried out in Valdivia in 1987 reported higher prevalences, with 61.8% of Blastocystis sp. and 30% of Ent. coli (12). While Ent. coli and other non-pathogenic organisms identified directly cause disease, their presence indicates exposure to fecal contamination, often through contaminated food or water with feces. This is relevant despite high levels of potable water and sanitation services in Chile. Compared to other Latin American countries, Chile demonstrate a lower prevalence of intestinal parasites and polyparasitism. A possible explanation for this could be related to the quality of water sanitation (25). To support this claim, a study analyzed the Environmental Performance Index (EPI) in the drinking water category of 180 different countries. The results concluded that Chile is the leader in Latin America in sanitation and drinking water quality (26). However, even if our study demonstrated a lower prevalence of intestinal parasitosis and polyparasitism in Chile compared to past data and neighboring countries, likely reflecting improvements in sanitation and water quality, the persistence of intestinal protozoa like Blastocystis sp. and Ent. coli underscores ongoing exposure to fecal contamination, suggesting the need for continued public health efforts.

The causes of enteroparasitosis are multifactorial, influenced by factors such as basic sanitation, drinking water sources, overcrowding, environmental temperature, among others. These factors can significantly impact the probability of parasitosis and explain the variability in prevalence report across different studies, which are highly dependent on the characteristics of the population studied (27, 28). At the local level, the difference in prevalence described in a study performed in 1987 and the present study may be attributed to contrasting living conditions. The 1987 study focused on a rural population, where many lacked accesses to potable water, sanitary excreta disposal, and regulated garbage collection, conditions that are not present in the urban population of this study. Here, 98% of participants reported having access to sewerage system, 91% use only drinking water over the past year and 100% had garbage collection services (12).These improved conditions suggest that the parasitized patients in our study would likely acquire parasitosis through alternative routes, such as the consumption of poorly washed vegetables or coming into contact with soil contaminated with infective stages (28). Furthermore, the statistical analysis associating the presence of parasites with socioeconomic factors showed that living with pets is a statistically significant factor (χ² = 4.9, p = 0.03). Participants living with pets were found to be almost three times more likely to have parasites (OR: 2.9, [1.1–7.5]). This highlights zoonotic transmission as the most critical route of infection for intestinal parasites in this urban setting.

In the present study the prevalence of anti-Toxocara canis IgG obtained was 33%. In Chile, a prevalence of 8.8% was previously reported in 1989, 10% in 1998, and 24.4% in 2012 (18, 29, 30). A statistically significant difference was found between the prevalence of anti-Toxocara canis IgG and the level of education of the participants (p = 0.03) and a higher risk of having anti-Toxocara canis antibodies was found with a lower educational level (OR: 0.5; CI: 0.2–0.9). Although education has been associated as a predisposing factor in enteroparasitosis, in toxocariosis its relationship is not clearly established, thus an analysis performed in Pakistan on different human populations, found a statistical association in one group of human and no relationship with others depending mainly with the regular contact of each group with pet animals or livestock, a key factor in the transmission (31). In addition, most serological studies against T. canis have focused on children, as they are considered to be the largest population at risk, so education has not been a fully investigated as a factor.

All the other 17 factors studied in our socioeconomic survey showed no statistically significant difference associated to the prevalence of antibodies anti-Toxocara canis. Between them, no significant difference was described related to the presence of a garden or patio in the home or with pet ownership (p > 0.05). This is consistent with a study conducted in Niebla, Chile, in 2016, which found no statistical association with these variables (18, 32). Studies in Argentina and Venezuela have found statistical significance with dog ownership (33, 34). Since the dog is the definitive host of T. canis, this lack of association may indicate that the origin of infection comes from other sources such as the consumption of water or food contaminated with T. canis eggs, onychophagia, geophagy, etc. (35). In our study, we observed T. canis eggs throughout the sampling period, in urban parks and also in dog feces collected from the environment. These results, associated with the high prevalence of anti-Toxocara canis antibodies in humans, allow us to hypothesize that humans are in contact with the parasite from the environment in their own neighborhood and the high presence of the parasite in urban areas (parks and streets) is a source of human infection and should therefore be considered as an important public health issue for local authorities.

Giardia duodenalis assembly A2 was found in 2 sequenced samples. The A group has zoonotic potential, it is frequently found in companion animals (dogs, cats and horses) and livestock (cattle, sheep, goats, alpacas, pigs, etc.). This group can be divided into subsets, which are A1, A2, and A3. The A2 subset is usually found in human hosts, but has also been found in cats, dogs, horses, and other animals (36–38). Most human infections around the world are caused by the A2 and B genotypes (39). Several studies have reported an association between assembly A and intermittent diarrhea, while other studies have reported a correlation between subset B and severe or persistent diarrhea (40). In this case, the A2 subset found in the samples of our study suggests the possibility of zoonotic transmission involving domestic animals such as cats or dogs.

Regarding the diversity of subtypes in each patient, a single majority subtype was successfully identified in each case. Specifically, one patient had G. duodenalis subtype A2 with 137,999 reads, plus a minimal proportion of reads for other subtypes: 165 reads for subtype D and 101 reads for subtype E of G. duodenalis. In another patient with G. duodenalis subtype A2 (146,476 reads), 87 reads for Giardia muris were detected. These readings of other subtypes are attributed to the high sensitivity of the technique used, which can detect even single nucleotide variations, which may result in residual readings representing less than 0.1% of the total readings. These residual readings are not considered reliable for subtype identification, but artifacts generated by the technique. This situation may be due to sequencing errors, chimera formation during PCR, and/or the technology’s high sensitivity. Several strategies could be implemented to mitigate these artifacts in future analyses, such as increasing sequencing depth, applying stricter thresholds to filter out spurious reads, or improving quality controls during sample processing.

Among the samples analyzed by NGS containing Blastocystis sp., subtype (ST) 1 was found in 2 samples, 1 sample with ST 2, 2 samples with ST 3 and one sample with ST 4, while in 2 samples (20%) there was no amplification due to the low quality of the DNA extracted. The most common subtypes worldwide are ST 1, 2 and 3, while ST 4 is regularly detected in symptomatic patients in Spain and other European countries, but is rare in South American countries, although it has been previously reported in countries such as Colombia and Brazil (41, 42). Although some studies indicate that Blastocystis sp. may be associated with diarrhea, abdominal pain, irritable bowel syndrome, constipation and abdominal distension, it has not been determined whether these symptoms belong to a specific ST, it has also been described that subtypes 1 and 3 of Blastocystis sp. are frequently found in patients with irritable bowel syndrome (IBS). whose prevalence is not well documented in Chile. The 4 subtypes present in this study have also been detected in animals such as dogs, pigs, cows, rodents and others (41). In our study, most of the identified subtypes of Blastocystis sp. and G. duodenalis found in humans are potentially zoonotic parasites, which is consistent with the previously discussed finding that ownership domestic animal increases the risk of having intestinal parasites threefold.

Eggs of T. canis, U. stenocephala, T. vulpis, and T. leonina were found in the surveyed parks; all of which are associated with zoonotic transmission. The contamination of public spaces with parasitic elements is most likely due to the large number of stray dogs observed in the sector. Dogs can excrete up to 600 grams of feces per day on average and cover distances of up to 15 km per day (43), so it is very likely that they have had a significant impact on soil contamination. Similar findings were reported in a study carried out in Temuco (Chile), where eggs of Toxocara sp. and Trichuris sp. were found. However, in contrast to our study, the presence of Taenia sp. eggs was detected (14). This last difference could be related to differing levels of interaction between peri-urban or rural and urban environments (44). In urban settings, the dissemination of cestodes parasitic elements occurs mainly through the feces of carnivorous animals, such as stray dogs (45).

Interestingly, a greater diversity of zoonotic parasitic elements, particularly nematodes, was observed in spring compared to autumn. This is consistent with findings in New Zealand, where soil nematode diversity is higher during the spring season (46). The increased diversity of parasitic nematodes can be attributed to the improved weather conditions, which increases circulation of dogs in public areas, raising the possibility of soil contamination and the potential for parasite transmission (47, 48).

The physicochemical analysis of the soil showed that the pH range was from 5.3 in spring to 6.4 in autumn. The infective stages of geohelminths tolerate soil pH ranges between 4.6 and 9.4 (49). Other studies conducted in Ghana and Egypt have described a significant relationship between soil pH and the number of parasitic stages concluding that the highest number of parasitic elements are found in soils with pH between 5 and 8 (50, 51). Also, in the present study have been described a concentration of total carbon up to 14%, and it has been demonstrated that soils containing a higher amount of total carbon and soil organic matter are associated with a higher number of geohelminth eggs because it affects the porosity of the soil (52), therefore, species such as those belonging to the Ancylostomatidae family are favored in their development due to a soil with greater porosity that allows the infective larva to be kept close to the surface, providing greater oxygenation and facilitating contact with a susceptible host (53). Overall, the results suggest that the parks in our city possess physicochemical properties conducive to the survival and development of various zoonotic parasite species, highlighting the need for targeted public health measures.

In the study of feces of dogs with owners, a total of 39 samples were analyzed, revealing an overall prevalence of parasitosis of 25.6%. Among these, T. vulpis was observed in 15.4% of the samples, while G. duodenalis was found in 2.6%. Similar studies conducted in Chile, specifically in the cities of Talca and Cabrero, reported a predominance of T. canis eggs in Talca, with a frequency of 14%, and eggs from the Ancylostomatidae family in Cabrero, with frequency of 43%. Notably, in both studies T. vulpis ranked second in frequency with percentages ranging from 5 to 12.9% (54, 55). There was no statistically significant difference between parasitosis and dogs going outside their house freely (p > 0.05). Over half of the surveyed pets regularly went outside, contrasting with 27% reported in urban area of the Coquimbo region, Chile, but similar to the 50% reported in rural areas in the same region (56). The absence of a statistically significant difference between parasitosis and factors such as deworming or outdoor activities habits may be attributing to the limitations of this research. A limitation of the study could be the selection bias that may have occurred during the selection of the participants by the pet owners. Furthermore, the small number of samples analyzed (n = 39) could reduce the strength of the statistical analysis (57).

The frequency of one or more parasitic elements in these samples was 48.4% in spring and 40% in autumn, with no statistically significant differences between the two periods (p > 0.05). These frequencies were higher than those reported in a similar study conducted in Santiago de Chile, where 31.7% of the samples contained parasitic elements (58).

In our study the parasitic species did not vary significantly between the two sampling periods, with T. vulpis and U. stenocephala being the most frequently observed species, ranging from 23.5 to 30% and from 14.1 to 16.8%, respectively. In a study carried out in urban areas of Niebla and Corral, it was also found that these two species were the most common, with a difference in the frequency of observation, since in this study the percentages for T. vulpis ranged from 50.7 to 54.8%, while for U. stenocephala were between 65.7 and 83.4% (15). Additionally, our study detected Toxascaris leonina during the spring at a frequency of 2.1%, consistent with previous studies in the Los Ríos region, which reported frequencies of 3.3–8.0% (59, 60). It has also been documented in other areas in the country, such as Los Angeles (Chile), where it was detected in 1.33% of the samples (13), and in Santiago (Chile), where it was observed in 7.7% of the samples (58, 61). The frequency of protozoan parasites with zoonotic potential where only the presence of G. duodenalis cysts was found in 1.1% in spring and 2.4% in autumn. In various studies carried out in Italy, Germany, Poland, Colombia and Mexico, it has been seen that the prevalence of these parasite in dog feces ranges from 0 to 25% (61–66). In general, the presence of protozoan parasites such as G. duodenalis in dog feces is underestimated (66–68). This could be attributed to several factors, as the intermittent elimination of infective stages of parasites can lead to false negatives when observing an isolated sample microscopically (61, 65).

In summary, our study identified a 28% prevalence of intestinal parasites and a 33% prevalence of anti-T. canis antibodies in humans; also, a 26% prevalence in owned dogs and 44% frequency of parasites in dog stools collected from the street during spring and fall. Additionally, up to 30.5% (spring and fall) of soil samples from parks in the study area was found to contain parasitic elements. Thus, using a OneHealth approach, our study highlights that the prevalence of parasites in humans is influenced non only by human-to-human transmission, but also and significantly, by zoonotic and environmental transmission. The most striking example of this is the high presence prevalence of anti-T. canis antibodies in humans (over 30%) alongside the detection of Toxocara sp. eggs in both parks soil and environmental dog feces. The absence of T. canis in the feces of owned dogs suggests environmental transmission as a primary pathway. In addition, zoonotic subtypes of G. duodenalis (A2 assembly) and Blastocystis sp. subtypes 1,2,3 and 4 were detected in humans, which have also been reported in dogs and cats, reinforcing the role of pets in parasite transmission.

This study highlights the importance of adopting a OneHealth approach to parasitology research. The complex ecology of parasitic organisms demands an integrated perspective to fully understand their transmission pathways and develop effective control strategies. By emphasizing the interconnectedness of human, animal, and environmental health, we aim to contribute to the management and mitigation of this persistent public health issue.