Ação do hipoclorito de sódio sobre metacercárias de Fasciola hepatica

Abstract

Fasciola hepatica parasites the hepatic parenchyma and bile ducts of various species of mammals, including the human being and is considered a neglected zoonosis with cosmopolitan distribution. Infection of definitive hosts and human beings, acidental hosts, occurs through the ingestion of metacercariae that are adhered to the leaves of vegetables cultivated inside or in the vicinity of a watercourse or by the ingestion of contaminated water. The Agencia Nacional de Vigilância Sanitária (ANVISA) recommends that use of sodium hypochlorite (NaClO) for the disinfection of horticultural products and for the control of pathogens; however, there is no scientific reference to the action of NaClO on F. hepatica metacercariae. In this study we evaluated the efficacy of NaClO on F. hepatica metacercariae. Four groups of C57BL/6J mice (n = 9, for each group) were infected with metacercariae treated with NaClO. Group I: 0.2% NaClO; Group II: 0.02% NaClO; Group III: 0.002% NaClO and; Group IV: control group of mice infected with non-treated metacercariae. Metacercariae (n = 500), retrieved from Galba cubensis, were incubated in 1000 μL/ NaClO concentration for 15 min at 25 °C. In the next step, 10 metacercariae were inoculated in each mouse for infectivity analysis. Infected mice were evaluated for 90 days post infection (dpi). During the experimental period animals were maintained in welfare conditions and feed with ration and water ad libitum. The survival curve and clinical signs were also evaluated. In animals that have died, macroscopic assessment of liver lesions, liver histopathological analysis and parasites recovery were performed. Mice that have survived for 90 days were submitted to three parasitological stool examination (egg count per gram of feces – EPG). 10 metacercariae for each studied group were fixed with 4% paraformaldehyde for 48 hours at 4°C and analyzed through scanning electron microscopy (SEM). The collected data were analyzed using variance tests (Tukey). Jaundice, lethargy, prostration and bristly hair were observed in experimental animals on the 20 th dpi. From the 4 th week of infection, 78% of studied mice died in group I, 89% in group II and 87% in groups III and IV. Necrotic-hemorrhagic lesions and diffuse to disseminated jaundice were observed in animals’ livers. Histopathological examination showed areas of hepatocyte destruction, diffuse inflammatory infiltrates, hemorrhage and necrosis by coagulation. Parasites 4 mm long x 3 mm wide were also recovered from infected animals in the 4 th week post infection. In the 90 th dpí animals that have survived were EPG negative. SEM showered integrity of metacercariae’s external membrane. In conclusion, F. hepatica metacercariae treated with NaClO were able to develop and to establish infection in mice.