The distribution and abundance of Enterobius vermicularis in a South Indian fishing community

The distribution and abundance of Enterobius vermicularis in a fishing community in South India, as determined by counting worms expelled following mass anthelmintic chemotherapy, was examined in samples of patients stratified by age, sex and family grouping. The results of a worm expulsion study in January 1984 are compared with those of a second expulsion programme in November 1984, following an 11-month period of reinfection. The prevalence of Enterobius infection was consistently high in all age groups of both males and females. A comparison of the overall prevalence and intensity of infection in the January and November surveys revealed significant increases in both the percent infected and the mean number of worms harboured in November relative to the initial level. No significant trends in the intensity of Enterobius according to host age or sex were detected in either survey. The frequency distribution of Enterobius was found to be highly aggregated in the population as a whole and within age groups. At both sampling dates, the most heavily infected 25% of the community harboured over 90% of the total pinworms recovered. There was a significant pattern within most age groups for individuals to re-acquire worm burdens of a similar magnitude to their initial pre-treatment burdens. Heavy infections were found to be associated with household. A selective or targetted approach to treatment of heavily infected individuals or households is likely to be an efficient means of reducing parasite abundance on a community-wide basis. It must be stressed, however, that treatment must be applied at frequent intervals in order to achieve a long-term reduction in pinworm abundance and to avoid the possibility of increasing the intensity of infection, as was observed in this community.</p

Relationships between the synthesis of N-nitrosodimethylamine and immune responses to chronic infection with the carcinogenic parasite, Opisthorchis viverrini, in men

This study investigated the relationship between immune responses to infection with the liver fluke. Opisthorchis viverrini, and the synthesis of the carcinogen, N-nitrosodimethylamine (NDMA) in humans. It also examined associations between synthesis of nitric oxide (NO) and nitrosation of amines, in vivo. Antibody and T cell responses to fluke antigens and post-alcohol urinary NDMA excretion were assessed among three groups of 40-50 men with no, moderate and heavy liver fluke infection. Markers of NO synthesis (nitrate, nitrite) and nitrosation (nitrosamino acids) were also measured in biological fluids. Assessments were carried out under controlled conditions which minimised intake of exogenous nitrate and nitrite and were carried out at two time points, namely before and 4 months after elimination of the infection with praziquantel treatment. No statistically significant variation was observed in the amount of NDMA excreted between the 3 groups. However, during active infection, a strong negative association was observed between in vitro lymphoproliferative responses to some liver fluke antigens and NDMA excretion. After treatment this association was reduced. Multivariate statistical models revealed a highly significant relationship between NDMA levels and urinary nitrate, stimulation indices for two T cell responses to two parasite antigens (MW 37 kDa and 110 kDa) and gall bladder dimensions. NDMA levels after treatment were best described by the ratio between parasite-specific IgG2 and IgE, background levels of T cell proliferation, a urinary marker of nitrosation (N-nitrosothioproline) and usual level of alcohol consumption. These results suggest that individual background immunologic activity, parasite-specific responses and/or parasite products and NO synthesis are important determinants of endogenous generation of nitrosamines in O.viverrini-infected humans

Cholangiocarcinoma in north east Thailand. A hospital-based study

The population of Northeast Thailand has one of the highest known rates of cholangiocarcinoma (cancer of the bile ducts). We sought firstly to obtain an estimate of the frequency of hospital-based diagnosis of cholangiocarcinoma in the northeastern province of Khon Kaen. All pathology, ultrasound and in-patient and out-patient records were searched for cases diagnosed in tertiary hospitals in a random calendar month in 1988. A total of 203 persons from various parts of northeastern Thailand were newly-diagnosed in the two hospitals, 75 of whom resided in Khon Kaen province. We estimated the minimal age-standardised annual incidence rate in this province to be 135.4 per 100,000 among males and 43.0 per 100,000 among females (world standard). Truncated standardised incidence rates (ages 35-64 years only) were 334.2 and 104.3 per 100,000 for males and females respectively. Secondly we aimed to assess the feasibility of secondary prevention by early clinical diagnosis. However, the symptoms and signs observed were typically non-specific and associated with advanced disease in patients with cholangiocarcinoma who presented to hospital. Primary preventive measures appear to be the key to decreasing the mortality from this disease

Relationships between the synthesis of N-nitrosodimethylamine and immune responses to chronic infection with the carcinogenic parasite, Opisthorchis viverrini, in men

This study investigated the relationship between immune responses to infection with the liver fluke, Opisthorchis viverrini , and the synthesis of the carcinogen, N-nitrosodimethylamine (NDMA) in humans. it also examined associations between synthesis of nitric oxide (NO) and nitrosation of amines, in vivo . Antibody and T cell responses to fluke antigens and post-alcohol urinary NDMA excretion were assessed among three groups of 40-50 men with no, moderate and heavy liver fluke infection. Markers of NO synthesis (nitrate, nitrite) and nitrosation (nitrosamino acids) were also measured in biological fluids. Assessments were carried out under controlled conditions which minimised intake of exogenous nitrate and nitrite and were carried out at two time points, namely before and 4 months after elimination of the infection with praziquantel treatment. No statistically significant variation was observed in the amount of NDMA excreted between the 3 groups. However, during active infection, a strong negative association was observed between in vitro lymphoproliferative responses to some liver fluke antigens and NDMA excretion. After treatment this association was reduced. Multivariate statistical models revealed a highly significant relationship between NDMA levels and urinary nitrate, stimulation indices for two T cell responses to two parasite antigens (MW 37 kDa and 110 kDa) and gall bladder dimension. NDMA levels after treatment were best described by the ratio between parasite-specific IgG2 and IgE, background levels of T cell proliferation, a urinary marker of nitrosation (N-nitrosothioproline) and usual level of alcohol consumption. These results suggest that individual background immunologic activity, parasite-specific responses and/or parasite products and NO synthesis are important determinants of endogenous generation of nitrosamines in O.viverrini -infected humans