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Rev. Inst. Med. trop. S. Paulo vol.44 no.1 São Paulo Jan./Feb. 2002
Angiostrongylus costaricensis is a nematode parasitic of rodents. Man may become infected by ingestion of the third stage larvae produced within the intermediate hosts, usually slugs from the family Veronicellidae. An epidemiological study carried out in a locality in southern Brazil (western Santa Catarina State) where these slugs are a crop pest and an important vector for A. costaricensis has documented for the first time the natural infection of Deroceras laeve with metastrongylid larvae. This small limacid slug is frequently found amid the folds of vegetable leaves and may be inadvertently ingested. Therefore D. laeve may have an important role in transmission of A. costaricensis to man.
KEYWORDS: Metastrongyloidea; Angiostrongylus costaricensis; Deroceras sp; Limacidae; Veronicellidae.
In 1993, Sarasinula linguaeformis (Semper, 1885) was identified as a crop pest at the locality of Linha Cambucica, Nova Itaberaba, State of Santa Catarina, Brazil (27° 00' 00" S; 53° 10' 00" W)6. Five years later, the affected area was estimated to extend for 1,000 hectares where approximately 65 peasant families lived. In 1999, a parasitological examination was performed and 86% of the slugs were found infected with Angiostrongylus costaricensis Morera and Céspedes, 1971 a parasitic nematode usually living inside mesenteric arteries of wild rodents4,5. The rodents eliminate first stage larvae (L1) in feces, and molluscs ingest them or are infected by penetration through the tegument to produce the infective third stage larvae (L3)8. The most important intermediate hosts are slugs from the family Veronicellidae7. Human infection may lead to abdominal disease of varied severity2.
A longitudinal prevalence study on molluscs and a seroepidemiological survey on the human population began in August 2000. A diurnal search for molluscs was conducted at places indicated by the local residents at three sites: CES (grassy and garden areas next to the Community's Church), MPS (the surroundings of Mr. M.P. house) and DPS (the surroundings of Mr. D.P. house). A nocturnal passive search at a crop field next to DPS was also undertaken resulting in a very small number of molluscs that were pooled together with DPS for examination. In the laboratory the molluscs were eviscerated and had their body minced and incubated at 37 °C for 2 hours, with a 0.03 % (w/v) Pepsin (Sigma, Saint Louis, USA P7125) in 0.7 % (v/v) hydrochloric acid solution. The preparation was left in Baermann funnels for a minimum of 1 hour and larvae were identified as metastrongylid by demonstration of a sub-terminal notch. A total of 465 molluscs identified by external morphology as Deroceras laeve (Müller, 1774) an introduced European species, Bradybaena similaris (Férussac, 1821) an introduced Asiatic species, Phyllocaulis variegatus (Semper 1885) and S. linguaeformis were examined and the results are shown in Table 1.
S. linguaeformis is the predominant species and presented with the highest prevalence (1.5%). The prevalence of 86% detected in a preliminary evaluation in May 1999 was much higher than that now reported herein. This may result from the seasonal variation of transmission already detected with the human infection2.
Deroceras reticulatum (Müller, 1774) and D. laeve have been identified as intermediate hosts for another metastrongylid worm producing human disease: Angiostrongylus cantonensis1. The relative lack of specificity of metastrongylid parasites for their intermediate hosts has also been previously noticed8. The few metastrongylid larvae found in the present study were dead what prevented their definitive identification as A. costaricensis, through experimental infection of rodents and recovery of adult worms. But the site was previously confirmed to be a focus with active transmission of A. costaricensis4. In several other foci in southern Brazil Deroceras sp. was not found infected with A. costaricensis3. These small limacid slugs may have an important role in transmission of abdominal angiostrongyliasis to man, since they may remain between the folds of vegetable leaves and be inadvertently ingested.
Infecção natural de Deroceras laeve com larvas de metastrongilídeos em um foco de transmissão da angiostrongilíase abdominal
Angiostrongylus costaricensis é um nematódeo parasita de roedores. O homem pode se infectar pela ingestão da larva de terceiro estágio produzida nos hospedeiros intermediários, geralmente lesmas da família Veronicellidae. Em estudo epidemiológico em curso numa localidade no sul do Brasil (oeste do Estado de Santa Catarina) onde aquelas lesmas constituem praga agrícola e importantes vetores do A. costaricensis, documentou-se pela primeira vez a infecção natural de Deroceras laeve com larvas de metastrongilídeos. Este pequeno limacídeo é freqüentemente encontrado entre as dobras de folhas de verduras e pode ser ingerido inadvertidamente. É possível que tenha um papel importante na transmissão de A. costaricensis para o homem.
Finantial support: PUCRS, CNPq, FAPERGS, Prefeitura Nova Itaberaba, EPAGRI and from the Government of Japan (Monbushu).
1. ALICATA, J.E - Biology and distribution of the rat lungworm, Angiostrongylus cantonensis, and its relationship to eosinophilic meningoencephalitis and other neurological disorders of man and animals. Advanc. Parasit., 3: 223-248, 1965. [ Links ]
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8. THIENGO, S.C. - Mode of infection of Sarasinula marginata (Mollusca) with larvae of Angiostrongylus costaricensis (Nematoda). Mem. Inst. Oswaldo Cruz, 91: 277-278, 1996. [ Links ]
Received: 5 April 2001
Accepted: 5 November 2001
(1) Laboratório de Parasitologia Molecular do Instituto de Pequisas Biomédicas e Laboratório de Biologia Parasitária, Faculdade de Biociências da PUCRS, Porto Alegre, RS, Brasil.
(2) Laboratório de Malacologia da Faculdade de Biociências da PUCRS, Porto Alegre, RS, Brasil.
(3) Centro de Pesquisas para Pequenas Propriedades, EPAGRI, Chapecó, SC, Brasil
(4) Department of Parasitology, Akita University School of Medicine, Akita 010-8543, Japan
Correspondence to: Dr. Carlos Graeff-Teixeira, Laboratório de Parasitologia Molecular, Instituto de Pesquisas Biomédicas, PUCRS, Av Ipiranga 6690, 90610-000 Porto Alegre, RS, Brasil; email: firstname.lastname@example.org