Exposição para síndromes de larva migrans em praças e parques públicos em cidades do Chile
Rubén MercadoI; Marlene T UetaII; Douglas CastilloI; Victor MuñozI; Hugo SchenoneI
IInstitut de Ciencias Biomédicas. Facultad de Medicina. Universidad de Chile. Santiago, Chile
IIDepartamento de Parasitologia. Instituto de Biologia. Universidade Estadual de Campinas (Unicamp). São Paulo, SP, Brasil
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.
Keywords: Larva migrans, transmission. Feces, parasitology. Dogs.
Entre novembro de 2001 e dezembro de 2002, 600 amostras de fezes de cão foram coletadas nas principais praças e parques públicos de 13 cidades do Chile, localizadas nas regiões norte ao estremo sul da nação. No laboratório, as amostras foram processadas mediante os métodos de sedimentação por centrifugação e de Harada-Mori. Ovos de Toxocara canis foram encontrados em 12 cidades em freqüências que variaram entre 1,9 a 12,5% por cidade, com média de 5,2%. Sete por cento das amostras apresentaram ovos e 9,5% larvas rabditóides ou filarióides de Ancylostomatidae. Strongyloides stercoralis não foi encontrado nas amostras estudadas. Praças e parques públicos do Chile apresentam riscos potenciais para aquisição de larva migrans visceral, ocular ou cutânea.
Descritores: Larva migrans, transmissão. Fezes, parasitologia. Cães.
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 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).
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.
Positive samples corresponding to species, genera or families of intestinal helminthes detected by means of the observation of eggs in 600 samples processed by centrifugal sedimentation method were as follows: 31 T. canis (5.2%), 9 T. leonina (1.5%), 2 Dipylidium caninum (0.3%), 31 Trichuris sp. (5.2%), 1 Ascaris sp. (0.2%), 42 Ancylostomatidae (7.0%), and 10 Taenidae (1.7).
The Figure shows the location of the cities studied and the frequency per city of samples with T. canis eggs: Arica (2/50) 4.0%, Antofagasta (1/50) 2.0%, Illapel (5/50) 10.0%, Viña de Mar (0/27), Valparaíso (5/40) 12.5%, San Felipe (3/44) 6.8%, Santiago (1/54) 1.9%, Rancagua (2/27) 7.4%, San Fernando (4/50) 8.0%, Concepción (3/49) 6.1%, Temuco (2/50) 4.0%, Valdivia (2/50) 4.0%, and Punta Arenas (1/54) 1.9%.
Ancylostomatidae larvae detected per city by the H-M method were as follows: Arica (1/50) 2.0%, Antofagasta (0/50), Illapel (4/55) 7.2%, Valparaiso (4/40) 10.0%, Viña del Mar (0/27), San Felipe (0/44), Santiago (0/54), Rancagua (2/27) 7.4%, San Fernando (12/50) 24.0%, Concepción (4/49) 8.2%, Temuco (20/50) 40%, Valdivia (10/50) 20%, and Punta Arenas (0/54).
The frequency of samples with Ancylostomatidae larvae detected in cities in the northern half of the country (Arica, Antofagasta, Illapel, Viña del Mar, Valparaiso, San Felipe, Santiago) compared to the southern half (Rancagua, San Fernando, Concepción, Temuco, Valdivia, Punta Arenas) were as follows: 9/320 (2.8%) and 48/280 (17.1%), respectively. The cities from the southern region presented a higher frequency of Ancylostomatidae larvae (p<0.01).
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 the country contributes to reduce the presence of this parasite. In Campo Grande, Brazil, Ancylostomatidae eggs were detected in 56.8% of the samples studied (Araujo et al,1 1999).
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 parks) of the studied Chilean cities, being a potential risk factor for transmitting VLM, OLM, and CLM to people who circulate in these playgrounds.
Control measures for dog zoonotic nematodiases should be implemented in Chile to reduce the transmission risk of VLM, OLM and/or CLM in playgrounds throughout the country.
To Dr Jorge González of Parasitology Unit, Universidad de Antofagasta, Chile, and María Isabel Jercic of Parasitology Reference Laboratory, Instituto de Salud Pública de Chile for their laboratory support and assistance.
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2. Beaver PC, Jung RC. Animal agents and vectors of human diseases. 5th ed. Philadelphia: Lea & Febiger; 1985.
3. Grove DI, Northern C. Infection and immunity in dogs infected with human strain of Strongyloides stercoralis. Trans R Soc Trop Med Hyg 1982;76:833-8.
4. Mizgajska H. Toxocara spp. eggs in soil of public and private places in the Poznan area of Poland. Acta Parasitol 1995;40:211-3.
5. Oberg C, Franjola R, Leyán V. Helminths of the domestic dog (Canis familiaris) in Valdivia City, Chile. Bol Chil Parasitol 1979;34:21-6.
ICBM - Facultad de Medicina
Universidad de Chile
Casilla 9183 Santiago, Chile
Received on 21/8/2003
Reviewed on 12/1/2004
Approved on 18/3/2004