Search PubMed⌕ Search

Biomedical subjects

D D Mara

Publications and source records attributed to D D Mara.

At least 37 records · Page 2Linked to original sources
PubMed1995

An environmental classification of housing-related diseases in developing countries.

A preliminary environmental classification of housing-related diseases in developing countries is presented. This groups these diseases into six categories: those related to defects in (1) buildings and the peridomestic environment, (2) water supply, (3) sanitation, (4) refuse storage and collection and (5) food storage and preparation; and (6) industry-related diseases resulting from housing location (close to polluting industries or on contaminated land) and from the use of the home as a workplace. Each category has three subcategories: communicable diseases (including zoonoses), non-communicable diseases, and mental illnesses and psychosocial disorders.

Developing Countries↗
PubMed1992

Wastewater reuse in agriculture and the risk of intestinal nematode infection.

The increasing use of wastewater for crop irrigation in arid and semi-arid zones means that wastewater parasitology is becoming on important research area. The World Health Organization's (WHO) current guideline states that only treated wastewater containing no more than one human intestinal nematode egg per litre should be used for irrigation. This guideline was based on very limited epidemiological evidence. In this article Rachel Ayres, Rebecca Stott, Duncan Mara and Donald Lee describe their recent work in Yorkshire and northeast Brazil and suggest that their results may be the first evidence for relaxing the WHO guideline for restricted irrigation to no more than ten intestinal nematode eggs per litre.

Journal Article↗
PubMed1992

Influence of pH, Oxygen, and Humic Substances on Ability of Sunlight To Damage Fecal Coliforms in Waste Stabilization Pond Water.

Simple beaker experiments established that light damages fecal coliforms in waste stabilization ponds by an oxygen-mediated exogenous photosensitization. Wavelengths of up to 700 nm were able to damage bacteria. The ability of wavelengths of >425 nm to damage fecal coliforms was dependent on the presence of dissolved sensitizers. The sensitizers were ubiquitous in raw sewage, unaffected by sewage treatment, not derivatives of bacteriochlorophyll or chlorophyll, absorbed well in UV light, and had a slight yellowish color; they are therefore believed to be humic substances. The ability of light to damage fecal coliforms was highly sensitive to, and completely dependent on, oxygen. Scavengers of H(2)O(2) and singlet oxygen could protect the bacteria from the effects of sunlight, but scavengers of hydroxyl radicals and superoxides could not. Light-mediated damage of fecal coliforms was highly sensitive to elevated pH values, which also enabled light with wavelengths of >425 nm (in the presence of the sensitizer) to damage the bacteria. We conclude that humic substances, pH, and dissolved oxygen are important variables in the process by which light damages microorganisms in this and other environments and that these variables should be considered in future research on, and models of, the effects of light.

Journal Article↗
PubMed1991

Seasonal effects on the reported incidence of acute diarrhoeal disease in northeast Thailand.

This paper examines the seasonal variation in the reported incidence of acute diarrhoea for selected areas in the northeast of Thailand. Charts are presented which show rainfall, temperature and reported incidence of acute diarrhoea for the period 1982 to 1987. Incidence of diarrhoea appears to be inversely related to a sharp decrease in temperature around January each year. Although rainfall does not appear to have a direct effect on the relative incidence of acute diarrhoea, there is always a consistent reduction during July or August, after the rains have begun. Seasonal changes in climate may be indirectly related to other factors which have an important bearing on diarrhoeal disease. Rainwater collection is an important water source in this region and the affect this has on water use is discussed in relation to faeco-oral disease transmission.

Acute Disease↗
PubMed1989

Simple method for the detoxification of wastewater ultrafiltration concentrates for rotavirus assay by indirect immunofluorescence.

A simple method for the detoxification of ultrafiltration concentrates of wastewaters for rotavirus assay by the indirect immunofluorescence technique has been developed. Polyacrylamide (Bio-Gel) or dextran (Sephadex G50) beads were mixed with concentrates (0.5 g/10 ml, wt/vol) of wastewaters seeded with simian rotavirus SA11 and allowed to stand for 2 h. The supernatant was decontaminated with antibiotics and then assayed for rotaviruses. Concentrates from raw sewage and treated effluents seeded with SA11 were used to infect MA104 or LLC MK2 cell lines. The concentrates, particularly those from raw sewage and anaerobic waste stabilization ponds, were very toxic to the tissue culture cells. These toxic effects were determined by the detachment and subsequent loss of cells after incubation with concentrates and assay medium for 24 h. They were either completely eliminated or were reduced by greater than 80% after treatment with beads.

Animals↗
PubMed1988

The faecal coliform fingertip count: a potential method for evaluating the effectiveness of low cost water supply and sanitation initiatives.

A rapid and simple procedure for the enumeration of faecal coliform bacteria present on the fingertips is described. The distribution of individual faecal coliform fingertip counts within households has been compared with a number of variables related to the availability of water supply and sanitation facilities. This showed a strong association between the fingertip count and the possession of in-house water connections. It is proposed that this test might provide a reliable indication of the effectiveness of certain public health interventions.

Bacteriological Techniques↗
PubMed1986

Removal of intestinal nematode eggs in tropical waste stabilization ponds.

The removal of intestinal nematode eggs in waste stabilization ponds treating domestic waste-water was studied in northeast Brazil. Anaerobic and primary facultative ponds achieved Ascaris spp. removals of 88-98% and 99-100%, and hookworm removals of 91-97% and 98-100%, respectively. Egg-free effluents were produced by a single primary facultative pond with a retention time of 18.9 days, and by an anaerobic and a secondary facultative pond in series with retention times of 6.8 and 5.5 days. It is concluded that effluents with less than or equal to 1 egg per litre can be produced by a 1 day anaerobic pond followed by a 5 day secondary facultative and a 5 day maturation pond.

Ascaris↗
PubMed1985

Bacteriological methods for distinguishing between human and animal faecal pollution of water: results of fieldwork in Nigeria and Zimbabwe.

Bacteriological techniques have traditionally been used to detect faecal pollution of drinking water supplies. Recently, methods have been developed to distinguish between human and animal faecal pollution in temperate climates. The present study assessed the applicability and practicality of these methods in tropical countries. Fieldwork in Nigeria and Zimbabwe has shown that animal faecal pollution can reliably be identified by the detection and enumeration of Rhodococcus coprophilus using modified M3 agar, whereas human faecal contamination can be identified by the detection of sorbitol-fermenting bifidobacteria. Each of these organisms was detected only in the faeces of the type (human or animal) that it was meant to indicate. Although Streptococcus bovis has been used in the past in mainly temperate countries to distinguish animal from human faecal contamination, the present study has shown that this organism is not a reliable indicator of animal pollution in the tropics because it was excreted by a proportion of the human population in both Nigeria and Zimbabwe. Water sources known to be contaminated by human or animal excreta were examined for these indicator organisms. The results correlated with the results obtained from examining human and animal faecal specimens for these organisms. The role of these bacteriological methods in water pollution control programmes is discussed.

Animals↗
PubMed1983

Sorbitol-fermenting bifidobacteria as specific indicators of human faecal pollution.

Bifidobacteria were consistently present in the faeces of both man and pigs but only occasionally in the faeces of cattle and sheep, and they were not isolated from faecal samples from other animals; total counts of bifidobacteria were obtained by membrane filtration with YN-17 medium, a modification of Resnick and Levin's YN-6 medium. Mannitol-fermenting strains of bifidobacteria were isolated from both human and animal faeces, but sorbitol-fermenting strains were obtained only from human samples. These sorbitol-fermenting strains were identified as either Bifidobacterium adolescentis or B. breve and their numbers were obtained by membrane filtration of Human Bifid Sorbitol agar (HBSA). Sorbitol-fermenting bifidobacteria are specific indicators of human faecal pollution of waters and wastewaters.

Animals↗
PubMed1983

Investigation of the survival characteristics of Rhodococcus coprophilus and certain fecal indicator bacteria.

Rhodococcus coprophilus and Clostridium perfringens survived in fresh water samples held at 5, 20, and 30 degrees C for over 17 weeks, whereas Escherichia coli and fecal streptococci disappeared after 5 weeks at all three temperatures. R. coprophilus survived for more than 8 months in sterilized sewage and deionized water at all three temperatures, whereas in normal sewage held at 20 degrees C, the survival time was 12 to 26 weeks. In samples held at 30 degrees C, survival times were shorter, probably because of interbacterial competition or protozoal predation. The results indicate that R. coprophilus may be a useful indicator of the presence of remote fecal pollution of farm animal origin, but not of recent pollution, when enumerated alone in polluted waters or wastewaters.

Actinomycetales↗
PubMed1981

Occurrence of Rhodococcus coprophilus and associated actinomycetes in feces, sewage, and freshwater.

Freshwater, sewage, and fecal samples from various sources were examined for Rhodococcus coprophilus, associated actinomycetes, Escherichia coli, and fecal streptococci. Rhodococcus coprophilus was isolated consistently from feces of farm animals, poultry reared in proximity to farm animals, freshwater, and wastewater polluted with animal fecal wastes. It was not isolated from samples of human feces. The ratio of R. coprophilus total actinomycetes was higher in feces from cattle, sheep, ducks, and geese than in specimens from pigs, horses, and fowl. In samples from two freshwater streams polluted by fecal material from farm animals, the ratios of R. copropilus to total actinomycetes were similar to those found in fecal specimens from cattle and sheep. Ratios of fecal coliform to fecal streptococci could not distinguish between fresh human and animal fecal samples and, furthermore, were not reflected in the stream waters polluted by animal fecal material. R. coprophilus has potential in water and dairy bacteriology as a specific indicator organism of fecal pollution due to farm animal wastes.

Actinomycetaceae↗
PubMed1973

A single medium for the rapid detection of Escherichia coli at 44 degrees C.

Lactose tryptone ricinoleate broth (0.3% lactose, 2% Oxoid tryptone, 0.1% Na ricinoleate; pH 7.1) was found to be as good as the currently recommended combination of lactose ricinoleate broth and tryptone water for the detection of Escherichia coli in the positive tubes of presumptive coliform counts.

Culture Media↗
PubMedDate not supplied

The accumulation, distribution and viability of human parasitic nematode eggs in the sludge of a primary facultative waste stabilization pond.

Investigations into the enumeration, distribution and viability of nematode eggs in the sludge from a primary facultative waste stabilization pond showed that pond sludges are not nematologically safe for immediate land application. Up to 12% of Ascaris lumbricoides eggs were viable after the pond had been in operation for 2.5 years. Eggs were recovered from the sludge along the full length of the pond, although there were significant decreases in egg concentration and viability with increasing distance from the inlet.

Animals↗