Alternativas terapêuticas no combate à Esquistossomose Mansônica / Alternative therapeutic agents to combat Manson´s schistosomiasis

A esquistossomose mansônica é classificada pelo Ministério da Saúde como uma doença negligenciada, causada pelo trematódeo intravascular Schistosoma mansoni. As precárias condições de higiene estão diretamente relacionadas às áreas endêmicas, bem como à pobreza e ao baixo desenvolvimento econômico. Na atualidade, o praziquantel é o fármaco de escolha utilizado para o tratamento dessa patologia. No entanto, o mesmo é relativamente tóxico devido à sua baixa solubilidade, além de relatos acerca de parasitas resistentes ao tratamento. Nesse contexto, faz-se necessário buscar novas alternativas terapêuticas que possam ser utilizadas no tratamento dessa doença. Esta revisão trata da busca por uma nova quimioterapia e sugere a possibilidade de que formas mais adequadas de vetorização de medicamentos já existentes sejam capazes de associar vantagens terapêuticas ao fármaco de escolha para o tratamento proposto, de forma que a população infectada receba seus benefícios.

Manson´s schistosomiasis is classified by the Ministry of Health as a neglected disease caused by the intravascular trematode Schistosoma mansoni. Endemic areas are directly related to poor hygienic conditions, as well as poverty and a low level of economic development. Currently, praziquantel is the drug of choice used to treat this condition, but it is relatively toxic, due to its low solubility, and there are reports of the parasite developing resistance to the treatment. In this context, there is a need to search for new therapeutic agents that can be used to treat this disease. This review covers the search for a new chemotherapy and suggests the possibility that the best existing drug vectorization systems may be able to combine therapeutic advantages with the drug of choice for the treatment, to the benefit of the infected population.

Differential regulation of granuloma size and hepatic fibrosis in schistosome infections

Granuloma size is the variable most frequently used to evaluate the immunopathogenesis of schistosome infections. However, hepatic fibrosis is at the least an equally relevant variable. Hepatic fibrosis and the size of circumoval granulomas are frequently dissociated in experimental murine Schistosoma mansoni and S. japonicum infections. Virtually nothing is known of the immunoregulation of schistosomal hepatic fibrosis. This review notes many of the studies which have found discrepancies in granuloma volume and hepatic fibrosis, attempts to put them in perspective and to evaluate methods of calculating changes in collagen synthesis or content.

Hepatosplenic lesions induced by experimental Schistosoma malayensis in rabbits.

Two groups of three rabbits each were infected with 250 cercariae of the Baling and Koyan strain of Schistosoma malayensis. Changes induced by both strains included periportal hepatocellular necrosis and fibrosis. Vascular changes such as portal phlebitis and thrombophlebitis and varying degrees of pericholangitis were also present. Amyloid deposition was noted. A comparative study of the changes induced in rabbits by S. malayensis, S. mekongi and S. japonicum showed that the hepatic lesions induced by the Baling strain of S. malayensis were similar to that induced by S. japonicum, and were more severe than that induced by S. mekongi or the Koyan strain.

quantitative assessment of collagen in non schistosomal and schistosoma associated urinary bladder carcinoma

Forty urinary bladder samples were obtained for study, they included 4 benign bilharzial cystitis cases and 36 urinary bladder carcinomas [14 associated with schistosomiasis and 22 without evidence of schistosomal infestation]. The cases were subjected to a quantitative assessment of their collagen content by two methods: Colorimetric micromethod for collagen quantitation and morphometric analysis of collagen by use of an image analyzer. The results obtained by both methods pointed out that benign bilharzial cystitis cases contained more total collagen than the malignant cases and the malignant bilharzial cases were more fibrogenic than the non-bilharzial. Differences between the various histological subtypes were also seen with squamous cell carcinoma displaying more desmoplasia than adenocarcinoma and transitional cell carcinoma. Transitional cell carcinoma associated with bilharziasis was close in collagen content to squamous cell carcinoma without bilharziasis. It was apparent from these results that the total amount of collagen in addition to the distribution pattern of the fibrotic process in schistosomal cases around the newly formed blood vessels and lymphatics both play a role in determination of the unique behavior of such neoplasms

Prevalence of intestinal parasitic infections in Kuwait

Individuals who were suspected of suffering from intestinal parasitic infections during the calender year of 1986 were examined macroscopically and microscopically for the identification of parasites at the 6 general hospitals in Kuwait city and its suburbs. A total of 1,437 females and 2,335 males were positive for parasites, and 2,228 individuals were reported being negative. The prevalence of potentially pathogenic parasites was 67% of the total, while the commensals reached 33%. Of the first group Giardia lamblia and Trichuris trichiura were the commonest followed by Strongyloides stercoralis and Hymenolepis nana. Among the commensals Entamoeba coli was encountered frequently, followed by Trichomonas hominis and Endolimax nana. The highest rate of infection was found among Kuwaiti nationals followed by the Bangladeshis, Sri Lankans, Indians and Egyptians. The high prevalence rate among Kuwaitis indicates that there is a high transmission rate of parasitic infections possibly due to importation of disease with imported labour for domestic help and poor hygiene from both parties. Therefore, it is recommended that domestic helpers, arriving from endemic areas, be routinely checked. Effective chemotherapy and proper education should be implemented

Effects of physico-chemical factors on the infection of mice with Schistosoma japonicum and S. mekongi cercariae.

The three physico-chemical characteristics of water tested-pH, temperature and salinity were found to affect the infection of mice by cercariae of S. japonicum and S. mekongi. For both species of schistosomes, the range of optimal pH that showed highest infection and worm recovery rates was between 5.4-7.4 and decreased as the pH increased. Cercariae exposed to temperatures between 15 degrees-30 degrees C showed the highest infection and worm recovery rates. As temperature decreased or increased, the infection and worm recovery rates decreased. Sodium chloride concentration at low level (0.5-200 ppm) did not have great effect on the infection and worm recovery rates. The infection and worm recovery rates decreased as salinity increased. High sodium chloride concentration at 3200 ppm for S. mekongi cercariae and at 6400 ppm for S. japonicum cereariae inhibited cercarial penetration and no infection occurred.

Effects of cercarial concentration and length of exposure on the infection of mice by Schistosoma japonicum and S. mekongi cercariae.

The effects of cercarial concentration and length of exposure on the infection of mice by Schistosoma japonicum and S. mekongi were studied under laboratory conditions. For all cercarial concentrations of 10, 20 and 30, mice exposed for 1 min acquired little or no infection. Total worm recovery tended to rise with an increase either in cercarial concentration or exposure time. The highest infection rate and worm burden were obtained in mice exposed for 64 min to 30 cercariae per mouse. The present investigation suggested that exposures of 1 min or less carried little risk of infection at low cercarial concentration. There was a greater risk of infection in prolonged exposure to low cercarial concentration. Prolonged exposures to high cercarial concentration carried the greatest risk of high infection rate and worm burden.