INTRODUCTION

Endoparasites of humans and domestic animals can multiply under favorable conditions, and can be transmitted among the inhabitants of the house ^1,2. These favorable conditions are commonly associated to factors related to the individual (age, sex, nutritional status, etc.) ³, and/or socio-environmental risk factors such as the inadequate disposition of stool, unsuitable personal hygiene habits, and unequal access to education and health, among others ⁴.

In this regard, the number of slums has increased in Argentina, which lack basic services such as drinking water, electricity and adequate sanitation ⁵. The overall prevalence rates of endoparasites in Argentinean children and their pets have been reported to be 64.8% and 85.7% and 8.9% and 41%, respectively ^6,7,8.

Specifically, 3.6% of dwellings in the province of Corrientes are not adequate for living, 6.5% lack basic sanitary conditions, 11.0% are critically overcrowded, and 37% are located in vulnerable areas (near garbage dumps or flood-prone land) ⁹. However, few parasitological studies have taken these variables into account ¹⁰.

Therefore, we consider that the city of Corrientes, in northeastern Argentina, could represent a high-risk area for the transmission and maintenance of potentially zoonotic parasites. We also identified important gaps in parasitology research involving human, animal and environmental factors, i.e. operating under the One Health approach, which hinders the interpretation of all these factors together, as well as the opportunity to propose control and prevention measures.

This study aimed to examine the prevalence of intestinal parasites in children and domestic animals in two periurban neighborhoods of the Capital Department (Corrientes, Argentina). In addition, some human characteristics (sex and age), socio-environmental traits and hygiene practices were evaluated as possible risk factors for parasitic infection.

THE STUDY

Study area

The study was conducted in two suburban neighborhoods (A and B) of the Capital Department of Corrientes Province (27°28'00" S, 58°50'00" W), northeastern Argentina (Figure 1). These neighborhoods are characterized by poor sanitary conditions and a high degree of contact with domestic and synanthropic animals, among others.

Figure 1 Geographical location of the Province of Corrientes in northeastern Argentina (a), Capital Department (b) and the peri-urban neighborhoods analyzed (c). 

FINDINGS

DISCUSSION

Infected animals eliminate parasitic stages through their feces and contaminate the environment ¹³. In this sense, our results show that 58.6% of the dwellings were contaminated with parasitic species (particularly geohelminths) found in animal feces, most of them with zoonotic potential. We found that 39.6% of the households were contaminated, in addition to the presence of parasitic species in children’s feces; 32.7% of the dwellings recorded only the presence of parasitic species in children’s feces (mainly zoonotic protozoa). Therefore, it is evident that in these dwellings the conditions for the development of the life cycle, maintenance and transmission of both helminths and protozoa were optimal and constitute a serious epidemiological scenario for public health.

Parasites were found in more than 50% of the children, most of them presented only one species. This coincides with previous research carried out in Corrientes ^10,14 and other areas of Argentina ^2,15. The most prevalent protozoan species were Blastocystis and Giardia (35.6% and 21.2%, respectively), while Entamoeba coli was the least prevalent (6.8%). This pattern has been reported in infant populations in Argentina ⁷ and in the province of Corrientes, with prevalence rates similar to our results ¹⁰; however, more recently, locally, the prevalence of Blastocystis has been found to be considerably lower (16.7%) ¹⁴.

Worldwide, Giardia is known to be one of the main parasites causing diarrheal diseases (not viral or bacterial) in humans and other mammals ¹⁶; while Blastocystis has been associated with different intestinal and extraintestinal diseases in humans ¹⁷. Entamoeba coli is commensal, but is an indicator of environmental fecal contamination. These three protozoa share the same fecal-oral transmission pathway and their presence is associated with contaminated water or consumption of raw vegetables with feces from infected hosts ¹⁸. Deficient personal hygiene habits, particularly hand washing, have also been described ¹⁹. In that sense, it has been reported that parents tend to over-report their children’s hand washing behaviors, which would systematically diminish any apparent benefit and in some cases may even show negative effects ²⁰. In this sense, although mothers stated that most children washed their hands before eating and after leaving the bathroom, we found deficiencies in children’s general hygiene, a situation also reported by school authorities. Therefore, this type of result should be validated with a methodology that allows direct observation. Surprisingly, the presence of E. coli was associated with the frequency with which individuals bathed, but 86.3% of the mothers stated that their children bathed every day, supporting the need for direct observation.

As for animals, Giardia and Blastocystis were found in fecal samples from dogs (13.0% and 3.5%, respectively) and in one rabbit. Entamoeba coli was found in one dog and one pig. In the city of La Plata, Cociancic et al. ²⁾ reported a similar prevalence rate in dogs for Giardia and a higher prevalence for E. coli (10.3%), but they did not find Blastocystis. The prevalence was even lower for these protozoa in dogs from another locality in Argentina ¹⁵. In short, despite the low prevalence of these parasites in pets, we establish the role of animals as a source of environmental contamination and disseminators or as possible foci of animal-animal or human-animal transmission, in which case molecular studies are necessary to verify possible cross-transmissions.

As for helminths, we mainly found Enterobius vermicularis (10.2%) and, to a lesser extent, Hymenolepis nana (3.4%) and Ascaris lumbricoides (2.0%). Enterobius vermicularis has been widely reported in all provinces of Argentina, with a prevalence rate ranging from 13.6% to 50.9% ¹⁴. Different studies associated its presence with onychophagia ², poor nail and hand washing, overcrowding, and sharing beds and clothes ²¹. In our study, it is possible that the low prevalence is related to inefficient parental sampling.

Hymenolepis nana commonly infects humans and rodents. A prevalence rate similar to that found by our study has been reported in Argentina ^(14,22. In contrast, a prevalence rate higher than 20.0% was reported in the province of Misiones ⁷. Our results show that the presence of this parasite was associated with solid waste disposal. However, adults stated that garbage is collected in bags and then removed by the municipal collection service in all households where this helminth was found. It is important to note that we observed excessive accumulation of garbage both at the household level and in specific sectors of the neighborhoods evaluated. Therefore, there is evidence of inadequate waste disposal in this community, and we consider that this represents a risk, given the presence not only of rodents but also of domestic animals that were in direct contact with the waste.

A. lumbricoides was found in three children in three different dwellings. In contrast, a high prevalence of this parasite (38.9%) has been reported in other areas of Argentina ²³. Its presence in the environment is mainly related to open defecation, climatic conditions and soil, the latter determining the viability and maturation of the eggs. In Brazil, Gonçalves et al. ²⁴ determined the absence of latrines as a risk factor, showing that in South America, indigenous people usually live in conditions of extreme poverty.

Regarding the animals, ancylostoma, Toxocara canis and Trichuris vulpis were reported to be most prevalent in dogs (60.7%, 8.3% and 4.7%, respectively). This demonstrates high canine fecal contamination and poor pet health care in households. Similar results were reported in the city of Corrientes by Milano et al. ¹, and higher values were reported in the city of La Plata by Cociancic et al. ³. Ancylostoma larvae and T. canis can be transmitted to humans and cause cutaneous larva migrans syndrome and neural larva migrans syndrome, respectively ²⁵. Trichuris vulpis is a nematode of the large intestine of dogs and is of importance in veterinary medicine.

On the other hand, in agreement with Rivero et al. ¹⁵, co-infection of Giardia spp. and E. vermicularis was the most common and statistically significant, this could be due to the fecal-oral route of transmission that both parasite species share.

Regarding demographic variables, we found a significant association between age group and parasitosis, with school children being the group with the highest prevalence of parasites. Similar results have been reported by Rivero et al.¹⁵⁾ and Navone et al.¹⁴ This finding could be attributed to the fact that schoolchildren maintain close contact with the foci of parasitic infection through play and insufficient hygiene habits ²⁶.

The sample size was one of the limitations of our study, because we worked with a low number of dwellings and a low number of animal and human feces.

In conclusion, we found that a large number of the homes were contaminated with parasitic species, mostly helminths and protozoa of zoonotic importance, which shows the urgent need to improve sanitary control of children and animals in the area.