Experimental bilharzial squamous metaplasia of the urinary bladder in hamsters

A Study on the Etiological Factors of Bilharzial Bladder Cancer in Egypt: 5-Urinary Nitrite in a Rural Population

Urinary nitrite was present in 5.6 % of 2379 individuals from a rural population infested with « Schistosoma haematobium ». A higher frequency was observed in symptomatic patients with active bilharzial cystitis (25 %) and patients with bladder cancer associated with schistosomiasis (66.2 %); conversely, urinary nitrite was absent in normal urban individuals. The frequency of urinary nitrite was higher in females (6.4%) than males (4.6%), and was more frequent in adults than extremes of age. The presence of urinary nitrite was associated with urinary infection and was commonly accompaned by cellular atypia in urine, in the form of dysplasia. Under these circumstances, carcinogenic nitrosamines are liable to be produced in the bladder from urinary nitrite and amines. These observation support the possible role of urinary bacterial infection, commonly associated with bilharzial cystitis, in bladder carcinogenesis.

Hamster Weight Patterns Predict the Intensity and Course of Schistosoma haematobium Infection

Although Syrian golden hamsters are widely used as hosts for experimental infection by Schistosoma haematobium , surprisingly little is known about the course of infection and associated intensity (as defined by measures of parasite burden). As such, we sought to define inexpensive, simple, noninvasive, and accurate methods for assessing and predicting the severity of disease in S. haematobium -infected hamsters in order to prevent premature hamster sacrifice and unexpected morbidity and mortality. Through monitoring the weight and behavior of infected hamsters, we determined that the weight-loss patterns of infected hamsters are highly correlated with commonly used measures of the severity of infection (i.e., numbers of eggs passed in the stool, worm burdens, and total egg yields). In contrast, we found no significant correlation between hamster weight-loss patterns and egg yields from liver and intestinal tissues. Our findings suggest that a more complex relationship exists among worm burden, fecundity, and egg passage in the feces than previously appreciated. Regardless, our data may be useful for workers seeking to optimize harvests of S. haematobium eggs and worms from infected hamsters for downstream applications.

A novel mouse model of Schistosoma haematobium egg-induced immunopathology

Schistosoma haematobium is the etiologic agent for urogenital schistosomiasis, a major source of morbidity and mortality for more than 112 million people worldwide. Infection with S. haematobium results in a variety of immunopathologic sequelae caused by parasite oviposition within the urinary tract, which drives inflammation, hematuria, fibrosis, bladder dysfunction, and increased susceptibility to urothelial carcinoma. While humans readily develop urogenital schistosomiasis, the lack of an experimentally-tractable model has greatly impaired our understanding of the mechanisms that underlie this important disease. We have developed an improved mouse model of S. haematobium urinary tract infection that recapitulates several aspects of human urogenital schistosomiasis. Following microinjection of purified S. haematobium eggs into the bladder wall, mice consistently develop macrophage-rich granulomata that persist for at least 3 months and pass eggs in their urine. Importantly, egg-injected mice also develop urinary tract fibrosis, bladder dysfunction, and various urothelial changes morphologically reminiscent of human urogenital schistosomiasis. As expected, S. haematobium egg-induced immune responses in the immediate microenvironment, draining lymph nodes, and systemic circulation are associated with a Type 2-dominant inflammatory response, characterized by high levels of interleukin-4, eosinophils, and IgE. Taken together, our novel mouse model may help facilitate a better understanding of the unique pathophysiological mechanisms of epithelial dysfunction, tissue fibrosis, and oncogenesis associated with urogenital schistosomiasis.

Urogenital schistosomiasis (infection with parasitic Schistosoma haematobium worms, the most common human-specific Schistosoma species globally) affects over 112 million people worldwide. S. haematobium worms primarily lay eggs in the bladder, upper urinary and genital tracts, and the host immune response to these eggs is considered to cause almost all associated disease in these organs. Resulting conditions include hematuria (bloody urine), urinary frequency, fibrosis (internal scarring) of the urinary tract, increased risk of bladder cancer, and enhanced susceptibility to contracting HIV. Approximately 150,000 people die annually from S. haematobium-induced obstructive kidney failure alone, making this species one of the deadliest worms worldwide. Despite the importance of S. haematobium, a lack of an experimentally manipulable model has contributed to the paucity of research focusing on this parasite. We have circumvented the barriers to natural S. haematobium oviposition in the mouse bladder by directly microinjecting parasite eggs into the bladder wall. This triggers inflammation, hematuria, urinary frequency, fibrosis, egg shedding, and epithelial changes that are similar to that seen in clinical S. haematobium infections. Our model may provide new opportunities to better understand the basic molecular and cellular immunology of urogenital schistosomiasis and thereby contribute to the development of new diagnostics and therapeutics.

Mutagenicity evaluation of Schistosoma spp. extracts by the umu-test and V79/HGPRT gene mutation assay

Schistosomiasis has been suspected of being a risk factor for various types of cancers for sometime, e.g., bladder cancer, colorectal cancer and hepatic cancer. Among them, the etiological relationship between urinary schistosomiasis and bladder cancer is now widely accepted. However, mechanisms of the carcinogenesis are still unclear. Here, we tested the mutagenicity of the parasite extracts by the umu-test and hypoxanthine guanine phosphoribosyltransferase (HGPRT) gene mutation assay, which both overcome disadvantages of the Ames plate assay. Adult worm extracts and egg extracts of Schistosoma haematobium and Schistosoma mansoni were tested. Under our experimental conditions, neither worm nor egg extracts were shown to have any mutagenicity in both tests even in the presence of S9 mix. Our results suggest that there is very little possibility of immediate gene mutation due to the parasite-derived substances in schistosomiasis-related carcinogenesis.