Print version ISSN 0036-4665
Rev. Inst. Med. trop. S. Paulo vol.44 no.1 São Paulo Jan./Feb. 2002
Rubens RODRIGUEZ(1,2) Aventino A. AGOSTINI(1,2), Sérgio Machado PORTO(2), Augusto José Oliveira OLIVAES(2), Susana L. BRANCO(3), Júlia Pasquali GENRO(3), Antonio Carlo LAITANO(3), Rafael Lucyk MAURER(3) & Carlos GRAEFF-TEIXEIRA(3)
Angiostrongylus costaricensis is a parasitic nematode of wild rodents. Several other vertebrate species including man may become infected by ingestion of the third stage larvae produced by the intermediate hosts, usually slugs from the family Veronicellidae. There is a report of the diagnosis of abdominal angiostrongyliasis in Canis familiaris with lesions resembling those found in human disease. As a preliminar evaluation of the adequacy of a canine model for pathogenetic studies, a dog was inoculated with 75 L3 of A. costaricensis. Infection was established and fist stage larvae were found in feces up to 88 days post infection, sometimes in very large numbers (9.5 x 104 L1/g). No clinical manifestations or significant lesions were detected. These are indications that dog may play a role as a reservoir host for A. costaricensis.
KEYWORDS: Metastrongyloidea; Angiostrongylus costaricensis; Canis familiaris; Abdominal angiostrongyliasis
Angiostrongylus costaricensis is a nematode parasitc of wild rodents. The adult worm lives inside the mesenteric arteries or its branches and may accidentally infect man1. There is a report from Costa Rica of a natural infection of Canis familiaris with intestinal lesions similar to those described in humans2. For this reason a preliminar experiment was planned to evaluate the usefullness of dogs as an experimental model for pathological studies on abdominal angiostrongyliasis. One adult animal (9 kg) of undefined strain was inoculated per os with 75 third stage larvae (L3) of Angiostrongylus costaricensis, Santa Rosa strain. Metastrongylid larvae with a delicate groove next to the tip of the tail1 were detected in faeces from the 28th day post-infection (dpi) up to 88th dpi. Daily L1 output (Fig. 1) was very variable with several periods when no larvae was detected as well as days when a huge number was detected (maximum of 9.5 x 104L1/g). The identification of these larvae as A. costaricensis was obtained after passage through Biomphalaria glabrata (Esteio strain) and Swiss mice, where adult worms were recovered inside the mesenteric arteries. The dog remained asymptomatic and no significant macroscopic lesions were visualized at a laparotomy performed at 94th dpi. No significant changes occurred in haemoglobin concentration along the period of observation (data not shown). A slight increase in peripheral blood eosinophils was detected in the first 90 days of infection (Fig. 2). IgG antibodies were detected by ELISA (female worm crude antigen at 7 mg/ml, sample dilution at 1:100 and peroxidase conjugated anti-dog IgG at 1:1000) with a three fold sustained increase from 54th to the 93rd dpi and a return to baseline values (Fig. 3). At microscopic examination, a biopsy taken from the adipose tissue next to splenic hilum showed a recanalized thrombosis in a small artery, surrounded by an intense neutrophilic infiltration. No parasitic structure was identified.
In southern Brazil, several transmission foci are localized in urban areas where wild rodents are not easily found. Since sinantropic rodents are not as well adapted hosts to A. costaricensis as the wild rodents like Oligoryzomys nigripes3 another vertebrate species should play the role of definitive host. The present preliminary data indicate the possible role of Canis familiaris as a reservoir host for A. costaricensis. Dog is a natural host for another metastrongylid species, Angiostrongylus vasorum (Baillet, 1866), a nematode living inside the pulmonary arteries4. The asymptomatic course of infection and the abscence of macroscopical lesions at laparotomy at 94th dpi may be part of a spectrum of the disease in C. familiaris, not fully appreciated in a single preliminary experimental infection. If the low morbidity is a rule, dog would not be a good experimental model for pathological studies. But this data may also mean that dog is a well-adapted host for A. costaricensis and it may have in urban areas the role played by rodents in the wild cycle of abdominal angiostrongyliasis5.
Cães podem ser hospedeiros reservatórios do Angiostrongylus costaricensis
Angiostrongylus costaricensis é um nematódeo parasita de roedores silvestres. Várias espécies de vertebrados incluindo o homem, podem se infectar pela ingestão das larvas de terceiro estágio (L3) produzidas no hospedeiro intermediário, geralmente lesmas da família Veronicellidae. Existe um relato do diagnóstico de angiostrongilíase abdominal em Canis familiaris com lesões semelhantes ao encontrado na doença humana. Visando uma avaliação preliminar da utilidade do modelo canino para estudos de patogenia, um cão foi inoculado com 75 larvas L3 do A. costaricensis. O animal se infectou e larvas de primeiro estágio foram encontradas nas fezes até 88 dias após a inoculação, às vezes em número muito elevado (9,5 x 104 L1/g). Não foram detectadas manifestações clínicas ou significantes lesões nos intestinos. Estas são indicações de que cães possam ser hospedeiros reservatórios do A. costaricensis.
To Eva Medeiros for technical help. Finantial support: PUCRS, UPF, CNPq, FAPERGS.
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4. MORERA, P. Life history and redescription of Angiostrongylus costaricensis Morera and Céspedes, 1971. Amer. J. trop. Med. Hyg., 22: 613-621, 1973. [ Links ]
5. ROSEN, L.; ASH, L.R. & WALLACE, G.D. Life history of the canine lungworm Angiostrongylus vasorum (Baillet, 1866). Amer. J. vet. Res., 31: 131-143, 1970. [ Links ]
Received: 11 May 2001
Accepted: 7 December 2001
(1) Instituto de Patologia de Passo Fundo, Passo Fundo, RS, Brasil.
(2) Instituto de Ciências Biológicas, Universidade de Passo Fundo, Passo Fundo, RS, Brasil.
(3) Laboratórios de Parasitologia Molecular, Insituto de Pesquisas Biomédicas e de Biologia Parasitária, Faculdade de Biociências da PUCRS, Porto Alegre, RS, Brasil.
Correspondence to: Dr. Carlos Graeff Teixeira, Laboratório de Parasitologia Molecular, Instituto de Pesquisas Biomédicas, PUCRS, Av. Ipiranga 6690, 90619-000 Porto Alegre, RS, Brasil; email: email@example.com