Avaliação de diferentes metodologias para o diagnóstico parasitológico da esquistossomose mansoni

Abstract

Schistosomiasis mansoni is a major parasitic disease in the world and is known to be endemic in about 54 countries in the American and African continents. In Brazil the number of infected is estimated at 7 million. In different clinical forms, schistosomiasis mansoni resembles many other diseases. So this lack of specificity and symptoms variety hinder its diagnosis only by clinical examination. The disease is diagnosed using stool examinations. The Kato/Katz technique is the procedure recommended by the World Health Organization (WHO) for the diagnosis of Schistosoma mansoni, because it associates low cost and easy execution. Currently, there are commercial Kits available, in order to minimize the operational difficulties and improve the sensitivity of parasitological diagnosis, especially in areas of low endemicity. This study comparatively evaluated the effectivity of four stool parasitological techniques in diagnosing cases of schistosomiasis. Stool samples were examined by the Kato/katz and spontaneous sedimentation techniques, Midi Parasep® and Paratest® kits. One sample was collected from each individual and for each sample were prepared two slides of the four methods. A total of 442 coproparasitological exams were accomplished with migrants from endemic areas for schistosomiasis, of three cities under Health Superintendence Office of Alfenas (HSO) jurisdiction. The positivity rate of Kato/Katz technique for schistosomiasis was 1,8%. The positivity rate schistosomiasis by the spontaneous sedimentation technique and Paratest® was of 0,45%. By Midi Parasep® Kit the positivity rate was of 0,23%. The lower effectivity of spontaneous sedimentation and Midi Parasep® and Paratest® can be demonstrated by low agreement diagnostic with the reference examination (Kato/Katz). Kato/Katz and spontaneous sedimentation techniques showed low cost for the exam stool, about R$ 0,82 per exam and R$ 0,48 per exam, respectively. However, are those with greatest degree of exposure of the expert to biological samples. Midi Parasep® and Paratest® Kits showed the lowest degree of exposure to fecal sample, but are relatively more expensive for perform the fecal exam, about R$ 3,10 per exam and R$ 1,65 per exam, respectively. Regarding intestinal parasites, by the "gold standard" were found 97 (21,9%) individuals parasitized. The positivity rates of intestinal parasitosis detected by the Kato/Katz, spontaneous sedimentation, Midi Parasep® and Paratest®, were respectively, 5,2%, 19,5%, 17,6% e 18,3%. The results showed that the Kato/Katz technique presented best of performance diagnosising of schistosomiasis mansoni. Thus, epidemiological surveillance should implement the Kato/Katz technique in order to prevent the establishment of transmission of schistosomiasis.