The interaction of gram negative bacteria and S. mansoni in mice with experimental schistosomiasis

[Schistosoma-associated chronic septicemic salmonellosis: evolution of knowledge and immunopathogenic mechanisms]

Chronic septicemic salmonellosis is an individualized clinical entity characterized by prolonged fever with enlargement of the liver and spleen that occurs in Schistosoma-infected individuals who are coinfected with Salmonella. Several immunopathogenic mechanisms are involved, and they depend on the peculiarities of the interactions between Salmonella and various species of the genus Schistosoma. The modifications to the immune system that are caused by parasite infection are responsible for the evolution of the disease. In this review, we analyze the evolution of the knowledge on this entity and discuss the possible immuno-physiopathogenic mechanisms that contribute towards its development.

Experimental models of Schistosoma mansoni infection

Experimental models of Schistosoma mansoni infections in mammals have contributed greatly to our understanding of the pathology and pathogenesis of infection. We consider here hepatic and extrahepatic disease in models of acute and chronic infection. Experimental schistosome infections have also contributed more broadly to our understanding of granulomatous inflammation and our understanding of Th1 versus Th2 related inflammation and particularly to Th2-mediated fibrosis of the liver.

Pathology of pyogenic liver abscess in children

Little is known about preexisting lesions in livers of children with pyogenic liver abscess (PLA). Study of these lesions may elucidate possible predisposing factors for the disease. In Vitória, state of Espirito Santo, Brazil, PLA in children is frequently associated with helminthic infections and eosinophilia. We hypothesize that nematode infection with larvae migrating through the liver is a predisposing factor for PLA, because the infection induces immunomodulation and likely trapping of bacteria in liver granulomas. In this report, we describe observations of 22 cases of PLA in children studied at autopsy (16 cases) or in surgical biopsies (6 cases), including 17 boys and 5 girls ranging in age from 1 to 13 years (mean 4.6 years, median 3.5 years). Multiple abscesses in both lobes were found in 13 cases and a single abscess was found in the right lobe in 10 cases. All cases showed histologically classical pyogenic inflammation without morphological evidence of amoebiasis. In six cases there were granulomas similar to those caused by larva migrans visceralis (from Toxocara or other nematodes) in liver tissue not affected by the abscess. Nematode antigens in central areas of necrosis of granuloma in all six cases and fragments of a larva, possibly of Toxocara, were found on samples immunohistochemically stained with polyclonal anti-Toxocara antibodies. There were numerous eosinophils in abscesses with Charcot-Leyden crystals. Eosinophils were found frequently in portal triads far from the abscess wall. In four cases, in which bile duct ascariasis was found, worms were noted in the bile ducts, and eggs were found in liver parenchyma surrounding the abscess in two cases. Foreign-body granulomas were found in one case in which penetrating trauma was the cause of abscess. In one case there was one histiocytic granuloma whose origin was not determined. The observation of six cases of granuloma similar to larva migrans visceralis (or produced by other nematode larva) in liver tissue not directly affected by the abscess supports the hypothesis that helminth infections with larva migrating through the liver are a predisposing factor for pyogenic hepatic abscess in children.

Schistosomiasis. Pathophysiology, diagnosis, and treatment

Globally, schistosomes infect 1 in 30 people. Tourists travel to endemic areas, whereas students, workers, and expatriates travel to nonendemic areas. Physicians around the world need to remain aware of this common parasitic infection. Pathology results from parasite eggs that lodge in the intestines and liver. Intestinal schistosomiasis is most often asymptomatic and presents with occult gastrointestinal bleeding. Hepatosplenic schistosomiasis develops insidiously because of cumulative fibrotic injury. Stigmata of liver failure are absent unless comorbid viral or alcoholic hepatitis is present. Patients with end-stage hepatosplenic schistosomiasis die from variceal hemorrhage. Diagnosis of schistosomiasis is confirmed by finding eggs in stool or biopsy specimens. Antischistosome antibodies may identify infected tourists returning from endemic areas. Circulating schistosome antigens distinguish current from past infections. Praziquantel is the schistosomicidal drug of choice. Most cases of hepatosplenic schistosomiasis resolve after effective treatment. Prophylactic propranolol may prevent hemorrhage in praziquantel-treated patients with high-grade varices. Sclerotherapy is also efficacious. When necessary, patients with hepatosplenic schistosomiasis tolerate decompressive surgery well.