Exposure to larva migrans syndromes in squares and public parks of cities in Chile Exposição para síndromes de larva migrans em praças e parques públicos em cidades do Chile

Correspondence to: Rubén Mercado ICBM Facultad de Medicina Universidad de Chile Casilla 9183 Santiago, Chile E-mail: rmercado@med.uchile.cl Received on 21/8/2003. Reviewed on 12/1/2004. Approved on 18/3/2004. Abstract Between November 2001 and December 2002, 600 dog fecal samples were collected in main squares and public parks of 13 cities in Chile, from the extreme north to the extreme south of the country. The samples were processed in the laboratory by centrifugal sedimentation and the Harada-Mori methods. T. canis eggs were found in 12 cities. Detection rates ranged from 1.9 to 12.5% with an average of 5.2%. Seven percent of the samples had eggs and 9.5% had rhabditoid and/or filariform larvae of Ancylostomatidae. Strongyloides stercoralis were not found. Squares and public parks in Chile pose a potential risk of exposure to visceral, ocular, and/or cutaneous larva migrans syndromes.


Comunicações Breves Brief Communications
Larva migrans syndrome is mainly caused by the ingestion of larval eggs or skin penetration of larvae from intestinal nematodes of dogs and cats.Toxocara canis is the major causative agent of visceral larva migrans (VLM) and ocular larva migrans (OLM).Cutaneous larva migrans (CLM) is mainly produced by Ancylostomatidae larvae and Strongyloides stercoralis larvae, also originated in dogs, and can cause cutaneous lesions in humans.Clinical pictures of VLM and OLM vary from asymptomatic infections to severe liver, lung or eye involvement (Beaver &  Jung, 2 1985).
In Chile (population: 15,200,000), the proportion of domestic canine population is 1 per 7 people.The country's biogeographical conditions range from arid desert in the northern regions through moderate and agriculture climate in central regions to cold in the last three regions.These climatic differences may affect the transmission of zoonotic diseases to humans.The aim of the present study was to establish the transmission risk of VLM, OLM and CLM in public recreational green areas of Chilean cities and the role of dogs in the transmission of S. stercoralis to humans.
From November 2001 to December 2002 dog fecal samples were collected in 13 cities in Chile (Arica, Antofagasta, Illapel, Viña del Mar, Valparaíso, San Felipe, Santiago, Rancagua, San Fernando, Concepción, Temuco, Valdivia, and Punta Arenas), covering nearly the whole country.Dog fecal samples were collected directly from the grass of main squares or other public green areas in each city.All feces collected were considered as derived from dogs because they are the only quadruped domestic animals frequently seen defecating in urban public places in Chile.The minimum sample size to be collected (N=27) in each city was determined according to a previous study and it was widely achieved in most cities.Each sample was processed in the laboratory by centrifugal sedimentation and the Harada-Mori (H-M) method (Beaver & Jung, 2 1985).Statistical significance was determined using Epi Info 6.0 program's Chi-square test.
A total of 126 (21.0%) samples processed by centrifugal sedimentation and 72 (12.0%) by the H-M method presented eggs or larvae of intestinal helminthies, respectively.
S. stercoralis larvae were not observed in the fecal samples examined.
In all 13 studied cities, with the exception of Viña del Mar, T. canis eggs were found in 1.9 to 12.5%, with an average of 5.2%.These findings show that T. canis is widely distributed in the whole country.In playgrounds of Campo Grande, state of Mato Grosso do Sul, Brazil, T. canis eggs were found in 10.8% of the samples examined (Araujo et al, 1 1999).
The biogeographical characteristics -basically temperate temperatures and humid soils -of the southern half could facilitate the transmission of Ancylostomatidae infection from dogs.On the other hand, the rainless weather of the northern extreme of Human strains of S. stercoralis can infect dogs and epidemiological observations suggest that dog strains can infect humans (Grove & Northern, 3 1982).The absence of S. stercoralis larvae in the examined samples and in studies of autopsied dogs (Oberg et al, 5  1979) suggest that recreational areas do not play an important role in the transmission of strongyloidiases to humans in Chile.
T. canis and Ancylostomatidae eggs extensively contaminate recreational areas (squares and public .usp.br/rsp Exposure larva migrans in public places Mercado R et al The finding of Toxocara canis eggs spread by dogs is an indicator of the transmission risk of VLM or OLM in a certain biogeographical area (Mizgajka, 4 1995).

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Figure -The 13 Chilean cities studied for transmissible instars of dog intestinal nematodes to humans (positive samples/ examined samples and % of T. canis eggs detected).