Characterisation of the vascular pathology in Sigmodon hispidus (Rodentia: Cricetidae) following experimental infection with Angiostrongylus costaricensis (Nematoda: Metastrongylidae)

BACKGROUND Angiostrongylus costaricensis is a nematode that causes human abdominal angiostrongyliasis, a disease found mainly in Latin American countries and particularly in Brazil and Costa Rica. Its life cycle involves exploitation of both invertebrate and vertebrate hosts. Its natural reservoir is a vertebrate host, the cotton rat Sigmodon hispidus. The adult worms live in the ileo-colic branches of the upper mesenteric artery of S. hispidus, causing periarteritis. However, there is a lack of data on the development of vasculitis in the course of infection. OBJECTIVE To describe the histopathology of vascular lesions in S. hispidus following infection with A. costaricensis. METHODS Twenty-one S. hispidus were euthanised at 30, 50, 90 and 114 days post-infection (dpi), and guts and mesentery (including the cecal artery) were collected. Tissues were fixed in Carson’s Millonig formalin, histologically processed for paraffin embedding, sectioned with a rotary microtome, and stained with hematoxylin-eosin, resorcin-fuchsin, Perls, Sirius Red (pH = 10.2), Congo Red, and Azan trichrome for brightfield microscopy analysis. FINDINGS At 30 and 50 dpi, live eggs and larvae were present inside the vasa vasorum of the cecal artery, leading to eosinophil infiltrates throughout the vessel adventitia and promoting centripetal vasculitis with disruption of the elastic layers. Disease severity increased at 90 and 114 dpi, when many worms had died and the intensity of the vascular lesions was greatest, with intimal alterations, thrombus formation, iron accumulation, and atherosclerosis. CONCLUSION In addition to abdominal angiostrongyliasis, our data suggest that this model could be very useful for autoimune vasculitis and atherosclerosis studies.

An indirect immunofluorescence antibody test employing whole eggs as the antigen for the diagnosis of abdominal angiostrongyliasis

Abdominal angiostrongyliasis is a potentially fatal zoonotic disease with a broad geographical distribution throughout Central and South America. This study assessed the performance of Angiostrongylus costaricensis eggs as the antigen in an indirect immunofluorescence assay for the determination of parasite-specific IgG and IgG1 antibodies. For prevalence studies, an IgG antibody titre > 16 was identified as the diagnostic threshold with the best performance, providing 93.7 percent sensitivity and 84.6 percent specificity. Cross reactivity was evaluated with 65 additional samples from patients with other known parasitic infections. Cross reactivity was observed only in samples from individuals infected with Strongyloides stercoralis. For clinical diagnosis, we recommend the determination of IgG only as a screening test. IgG1 determination may be used to increase the specificity of the results for patients with a positive screening test.

Impactos socioeconômicos de uma doença emergente / Socioeconomic impacts of an emerging disease

Em 1995, ocorreu uma praga de lesmas identificadas como Sarasinula linguaeformis (Semper, 1885), que prejudicou as lavouras situadas entre os municípios de Nova Itaberaba e Planalto Alegre, no oeste do estado de Santa Catarina, Brasil. Neste artigo analisamos os impactos socioeconômicos provocados pela ocorrência desta praga, que sinalizou a possibilidade, posteriormente verificada, da emergência de casos de angiostrongilíase abdominal. Os dados foram coletados através de observação do estudo soroepidemiológico realizado na região durante o período de agosto de 2000 a agosto de 2001 pela equipe de pesquisa da Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), entrevistas com técnicos da Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina S.A. (Epagri-SC) e com cinquenta famílias locais. Para avaliar esses impactos, elaboramos algumas categorias de análise, como: prejuízo econômico; medidas preventivas e mudança de hábitos; estigma e preconceito, que surgiram à luz das narrativas dos sujeitos entrevistados. Ficou evidente a necessidade de se procederem a estudos sobre os aspectos sociológicos dos problemas epidemiológicos, além dos estritamente médico-sanitários.

In 1955 a population explosion of the slug Sarasinula linguaeformis (Semper, 1885) damaged crop plantations in the municipalities of Nova Itaberaba and Planalto Alegre, western of Santa Catarina State, Brazil. In this article we analyze the socioeconomic impacts caused by the emergence of this plague, which raised the suspicion, eventually confirmed, of the occurrence of human cases of abdominal angyostrongiliasis. The data were collected through the observation of a serological study during the period of August 2000 to August 2001 by a research team from the Catholic University of Rio Grande do Sul (PUCRS) together with field technicians from the Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina S.A. (Epagri-SC), and with the members of 50 local families. In order to analyze these impacts, we elaborated several analytical categories as economic losses; preventive measures, habit change and social prejudice, that emerged from the narratives of the residents interviewed. It became evident the need for sociological analyses of epidemiological problems, in addition to strictly medico-sanitary considerations.

Worms, slugs and humans: the medical and popular construction of an emerging infectious disease / Vermes, caramujos e humanos: as construções médica e popular de uma doença infecciosa emergente

The identification of the worm Angiostrongylus costaricensis parasitizing land snails and humans in Southern Brazil suggests under-diagnosis and under-notification of patients with abdominal angiostrongyliasis. This article analyzes how the concept of abdominal angiostrongyliasis was constructed in different ways in Costa Rica and Brazil and how these changes affected the understanding of its clinical and epidemiological diagnosis. The research shows that abdominal angiostrongyliasis is, de facto, a sociocultural construct, although the parasites and vectors are real. The analisys also shows the importance of an interdisciplinary approach for understanding disease.

A identificação do verme Angiostrongylus costaricensis em humanos e caramujos, no sul do Brasil, sugere a ocorrência de subdiagnóstico e subnotificação de pacientes com angiostrongilíase abdominal. O artigo analisa as diferentes construções do conceito de angiostrongilíase abdominal na Costa Rica e no Brasil e a influência dessas variações em seu diagnóstico clínico e epidemiológico. Demonstra que a angiostrongilíase abdominal é, de facto, um constructo sociocultural, embora parasitas e vetores sejam reais. Também destaca a importância da abordagem interdisciplinar para a compreensão da doença.

Use of heterologous antigens for the immunodiagnosis of abdominal angiostrongyliasis by an enzyme-linked immunosorbent assay

Angiostrongylus costaricensis has a broad geographic distribution spanning from North to South America and the infections of vertebrates with this nematode can result in abdominal complications. Human infections are diagnosed by histological or serological methods because the isolation of larvae from feces is not feasible, as most parasites become trapped in intestinal tissues due to intense eosinophilic inflammation. Because A. costaricensis is difficult to maintain in the laboratory, an immunodiagnostic IgG enzyme-linked immunosorbent assay (ELISA) using antigens from the congeneric Angiostrongylus cantonensis species was evaluated against a panel of serum samples from patients who were histologically diagnosed with A. costaricensis infections. Sera from uninfected individuals and individuals infected with other parasites were used as controls. The sensitivity and specificity of the assay were estimated at 88.4 percent and 78.7 percent, respectively. Because the use of purified or cloned antigens has not been established as a reliable diagnostic tool, the use of heterologous antigens may provide a viable alternative for the development of an ELISA-based immunodetection system for the diagnosis of abdominal angiostrongyliasis.

Abdominal angiostrongyliasis: report of two cases with different clinical presentations / Angiostrongilíase abdominal: relato de dois casos com diferentes apresentações clínicas

Abdominal angiostrongyliasis is a sporadic infectious disease caused by the nematode Angiostrongylus costaricensis. It usually presents as acute abdomen, secondary to mesenteric ischemia, and pronounced eosinophilia. In some cases its course is insidious and transient, and the diagnosis is suspicious. The disease is confirmed by the detection of A. costaricensis elements in surgical specimen. The treatment is supportive, with avoidance of antihelminthic administration due to a possible erratic migration followed by worsening of the disease. We report two cases, both with intense eosinophilia and serum IgG-ELISA positive to A. costaricensis. The first case presented ileal perforation and was surgically treated. The second one showed hepatic nodules at ultrasound and was only symptomatically treated, evolving to an apparent protracted resolution. These two cases exemplify different clinical forms of the disease, one of them with liver involvement.

A angiostrongilíase abdominal é doença esporádica decorrente da infecção pelo nematódeo Angiostrongylus costaricensis. Costuma manifestar-se como abdome agudo secundário a isquemia mesentérica, além de marcada eosinofilia. Pode também apresentar-se de forma insidiosa e transitória, exigindo alta suspeita clínica para o diagnóstico. A doença é confirmada pela identificação de elementos do A. costaricensis em peças cirúrgicas. O tratamento é apenas de suporte, devendo-se evitar o uso de anti-helmínticos pela possibilidade de migração errática do verme com piora do quadro. Aqui foram apresentados dois casos, ambos com acentuada eosinofilia e ELISA-IgG sérico positivo para A. costaricencis. O primeiro caso cursou com perfuração ileal e foi tratado cirurgicamente. O segundo caso apresentou nódulos hepáticos ao ultrassom e foi tratado sintomaticamente, evoluindo para lenta resolução. Estes dois casos exemplificam diferentes formas de apresentação clínica da doença, uma delas com envolvimento hepático.

Individual serological follow-up of patients with suspected or confirmed abdominal angiostrongyliasis

Abdominal angiostrongyliasis (AA) is a zoonotic nematode infection caused by Angiostrongylus costaricensis, with widespread occurrence in the Americas. Although the human infection may be highly prevalent, morbidity is low in Southern Brazil. Confirmed diagnosis is based on finding parasitic structures in pathological examination of biopsies or surgical resections. Serology stands as an important diagnostic tool in the less severe courses of the infection. Our objective is to describe the follow up of humoral reactivity every 2-4 weeks up to one year, in six individuals with confirmed (C) and ten suspected (S) AA. Antibody (IgG) detection was performed by ELISA and resulted in gradually declining curves of reactivity in nine subjects (56 percent) (4C + 5S), that were consistently negative in only three of them (2C + 1S) after 221, 121 and 298 days. Three individuals (2C + 1S) presented with low persistent reacitivity, other two (1C + 1S) were serologically negative from the beginning, but also presenting a declining tendency. The study shows indications that abdominal angiostrongyliasis is usually not a persistent infection: although serological negativation may take many months, IgG reactivity is usually declining along time and serum samples pairing may add valuable information to the diagnostic workout.