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M A Fernando

Publications and source records attributed to M A Fernando.

At least 37 records · Page 2Linked to original sources
PubMed1993

Species and strain differentiation of Eimeria spp. of the domestic fowl using DNA polymorphisms amplified by arbitrary primers.

Eimeria spp. from the domestic fowl were examined for genetic relatedness by the random amplified polymorphic DNA (RAPD) assay. Nine different oligonucleotide decamers with arbitrary DNA sequences were tested as primers to amplify DNA from six Eimeria species infecting chickens. Two strains each of E. acervulina and E. tenella were used. Depending on the species/strain-primer combination, between 1 and 12 DNA segments ranging in size from 0.16 to 4.95 kb were amplified. The two strains of E. acervulina showed minor and major differences in their amplified DNA patterns, giving a similarity coefficient of 61%. The two strains of E. tenella seemed to be more closely related, yielding a similarity coefficient of 98%. The differences observed between species were greater than those found between strains with every primer used, indicating that the RADP assay could be a useful tool for the study of relationships among these coccidia. The results obtained in this study also indicate the presence of unique, species-specific, amplified DNA segments that could be exploited to identify Eimeria species of the chicken.

Animals↗
PubMed1992

Excreta disposal behaviour and latrine ownership in relation to the risk of childhood diarrhoea in Sri Lanka.

A case-control study of environmental and behavioural risk factors for childhood diarrhoea was conducted in Kurunegala district, Sri Lanka. From five hospitals, 2458 children aged less than 5 years and suffering from diarrhoea were recruited as clinic cases, and a further 4140 reporting with complaints other than diarrhoea were recruited as clinic controls. Community-based cross-sectional surveys were also conducted in three of the five areas served by these hospitals, and from these a further 1659 children were recruited as community controls. Children from households where excreta were reported to be disposed of in a latrine were less likely to have diarrhoea than children whose families improperly disposed of excreta. The results obtained from comparisons of cases with clinic controls (adjusted odds ratio [OR] 1.42, 95% confidence interval [CI] : 1.01-1.98), and of cases with community controls (OR 1.35, 95% CI : 0.85-2.13) were in agreement, suggesting that no important selection bias operated on this association. If the observed proportion (91%) of improper excreta disposal among the population could be reduced to 50%, 12% of childhood diarrhoea episodes would be prevented. Although latrine ownership may be a necessary condition for safe excreta disposal behaviour, diarrhoeal morbidity may only be reduced in Sri Lanka if behavioural changes take place concomitant with the construction of sanitation facilities.

Case-Control Studies↗
PubMed1992

Measurement of the cytotoxic effects of different strains of Mycoplasma equigenitalium on the equine uterine tube using a calmodulin assay.

The cytopathic effects induced by five strains of Mycoplasma equigenitalium for cells of equine uterine tube explants were tested by measuring changes in cellular and extracellular concentrations of calmodulin (CaM). Calmodulin concentrations in samples of total homogenate (TH) and total homogenate supernates (THS) of the infected equine uterine tube explants were significantly lower than respective measurements on noninfected controls. In tissue culture medium fractions (TCM) of some infected explants, CaM concentrations were significantly higher than noninfected controls (p > 0.95). The results suggest that M. equigenitalium colonization on ciliated cells of the equine uterine tube can affect the permeability of the cell membrane leading to leakage or release of CaM during cell breakdown. Measurement of CaM concentrations in samples of TH revealed significant differences in the cytotoxic effects induced by different strains of M. equigenitalium on the equine uterine tube (EUT). The data suggests that some strains of M. equigenitalium may have a role in reproductive failure in the mare. In addition comparisons of the means of the concentrations of CaM in samples of TH or THS in EUT explants from four mares in the follicular and four in the luteal phase of the estrous cycle were found to be not significantly different.

Animals↗
PubMed1992

Characterization of Eimeria tenella unsporulated oocyst-specific cDNA clones.

A cDNA library was constructed with poly(A)+ RNA from unsporulated oocysts of Eimeria tenella in pUC18. After screening, 4 cDNA clones that hybridized to RNA of unsporulated and sporulating oocysts but not to RNA of either sporulated oocysts or second generation merozoites were isolated and characterized. Each of the cDNA clones is unique. The loci for 2 of the clones are on E. tenella chromosome 7, the site of the third is located on chromosome 6 and the last clone hybridizes, for the most part, to chromosome 5 but also to other E. tenella chromosomes. The cognate RNAs for each of the cDNA clones show differential patterns of hybridization during oocyst sporulation with the levels of RNA being low at the start of sporulation (0 hr), increasing to peak levels between 6.5 and 23 hr after the onset of sporulation and, in each case, decreasing to low hybridization levels at 48 hr after initiation of sporulation. These results establish that specific mRNA levels are differentially regulated during sporulation.

Animals↗
PubMed1991

Eimeria spp. of the domestic fowl: resolution of chromosomes by field inversion gel electrophoresis.

The molecular karyotypes of five species of chicken coccidia, viz., Eimeria acervulina, E. brunetti, E. maxima, E. necatrix, and E. tenella, were determined using field inversion gel electrophoresis (FIGE). Each species has a distinctive set of resolvable chromosomes which range from about 1 to greater than 5.7 megabases. We were able to resolve at least 8 chromosomes for E. acervulina, 5 for E. brunetti, 10 for E. maxima, 6 for E. necatrix, and 9 for E. tenella. If the value of 67 megabases for the genomic DNA of E. tenella is accurate, then under the conditions used here only about 60% of its chromosomal complement has been resolved.

Animals↗
PubMed1990

Menarcheal age and endemic goitre.

A total of 13,566 school girls from 17 districts in Sri Lanka recalled their date of menarche for a study on the prevalence of goitre. Seventy-four percent (10,036) did not have any signs of goitre, and the recalled mean age of menarche for this group was 13.6 years. This figure was significantly lower than the mean age of 13.9 years observed in the goitrous group. The mean age was lowest for thyroid grade 0 and highest for thyroid grades 1b and above. The mean age in high prevalence areas was significantly higher both among goitrous and nongoitrous groups, and in different areas of prevalence the mean age was higher among the goitrous than the nongoitrous. These findings strongly suggest a delay in sexual maturation among girls living in endemic goitre areas and among girls with evidence of goitre.

Adolescent↗
PubMed1990

The anthropometric status of children in Kurunegala district in Sri Lanka: its relation to water supply, sanitation and hygiene practice.

Anthropometric data for 1295 children were collected during cross-sectional surveys conducted in Kurunegala District, Sri Lanka between March 1987 and March 1988. The relationship between anthropometric status and a range of water, sanitation and hygiene-related exposures was examined. After taking account of socioeconomic and other potential confounding factors, some evidence was found that boiling of water was associated with improved height-for-age. It seems unlikely that boiling of water alone could be responsible for the observed increase in height-for-age. Boiling of water may be acting as a "marker" for a range of hygiene and child-care behaviours. No convincing evidence of any other association was found. In particular, water source was not associated with anthropometric status. A concurrent study conducted in the same population found evidence of a substantial reduction in diarrhoea morbidity associated with the use of improved sources. These findings, taken together, lend support to the hypothesis that interventions for the control of diarrhoea may have no detectable impact on anthropometric status.

Anthropometry↗
PubMed1990

Childhood diarrhoea in Sri Lanka: a case-control study of the impact of improved water sources.

Between January 1987 and March 1988 a case-control study of the impact of improved water sources on childhood diarrhoea was conducted in Kurunegala District, Sri Lanka. Two thousand four hundred and fifty eight cases of diarrhoea were recruited at five of the hospitals in the district. Another 4140 children presenting at the same hospitals with complaints other than diarrhoea were recruited as controls. Data from the five hospitals suggest that children in households drawing their drinking water from handpumps suffer 46% fewer episodes of diarrhoea than children in families using unprotected traditional sources (95% c. i. 29-59%), while children in families using protected traditional wells suffer 35% fewer episodes than children in families using unprotected traditional sources (95% c. i. 27-41%). There were, however, substantial differences between the different hospitals. Among children recruited at one of the hospitals, the reduction in diarrhoea rates associated with the use of improved sources was estimated to be 93% compared with an average of 18% for the other four hospitals. In common with other case-control studies conducted in Malawi and the Philippines, little evidence of confounding of the association between diarrhoea and water supply was observed. Our results suggest that, in Sri Lanka, the use of improved water supplies, including protected traditional wells, rather than unprotected traditional sources may lead to a substantial reduction in diarrhoea morbidity among children under five years of age.

Case-Control Studies↗
PubMed1990

Health impact evaluation of improved water supplies and hygiene practices in Sri Lanka: background and methodology.

Between January 1987 and March 1988 a Health Impact Evaluation (HIE) of the Rural Water Supply and Sanitation Project (RWSSP) was conducted in Kurunegala District. Four related activities were undertaken: 6598 children were recruited into a case-control study of diarrhoea morbidity conducted in five hospitals; an additional 1649 children from the catchment areas of three of the five hospitals were recruited as a community comparison group; environmental microbiology was performed on water samples collected during 3092 visits to the homes of children recruited into the study; diagnostic stool microbiology was performed for 371 children with diarrhoea and 121 controls. In this paper the seasonality of reported diarrhoea and the socio-demographic characteristics and health-related behaviours of each study group are examined. Cases, clinic controls and the community comparison group were all drawn from the essentially rural settlements typical of the southern part of the dry zone of Sri Lanka. The majority of households in these settlements are Sinhalese buddhist, and the main economic activity is subsitence farming. There was some evidence of differences between the three groups, community recruits tending to come from larger and wealthier households than the children recruited at the hospitals. Issues arising in the design and analysis of this Health Impact Evaluation are discussed. In particular, potential sources of bias are examined and the question of validity investigated.

Case-Control Studies↗
PubMed1990

Determinants of water quality, availability and use in Kurunegala, Sri Lanka.

Between January 1987 and February 1988, 4590 homes of children under five years of age were visited in three areas of Kurunegala district, Sri Lanka and data were collected on water related practices. 60% of the population used protected wells, 30% used unprotected sources and 10% used handpumps on boreholes or piped supplies. 90% of households had a source less than 1 km away. Mean water consumption was above 25 litres per capita per day and did not correlate with the distance to source. Samples of drinking water were collected and faecal coliform levels were determined in samples of stored water from 3092 households and in samples from the water sources used by 1043 of these households. The absence or presence of organisms in each sample, and the geometric mean count in samples with organisms were used as indices of contamination. Both indices changed with season and varied between areas and between types of water source. The proportion of positive source samples was uniformly high with the exception of piped supplies and handpumps. The mean count was highest for unprotected sources. There was no evidence that ground water contamination occurred in boreholes. With stored samples, boiling appeared to reduce contamination markedly. The proportion of positive stored water samples was also lower with the use of different vessels for collection and storage, with storage inside the house, and with use of a storage container other than an earthenware pot. Because surface water pollution appears to be important it is proposed that headwalls and drainage aprons be built around unprotected sources. Faecal contamination at the source may have more public health significance than contamination of stored water. In this respect public hygiene may play an important role in reducing water pollution at handpumps or protected wells.

Case-Control Studies↗
PubMed1989

Endemic goitre in Sri Lanka.

This survey examined 59,158 children from 87 schools in 17 out of 24 districts in Sri Lanka for goitre. The overall prevalence rate was 18.8%: 23.2% for girls and 14.0% for boys. Prevalence in districts varied from 30.2% in Kalutara to 6.5% in Matale. It was higher in rural than urban areas, and in inland than coastal areas. The sex ratio of prevalence rates was directly related and the ratio of palpable to visible goitre was inversely related to the severity of the endemic. It is suggested that for a rapid epidemiological assessment when the latter ratio is less than four, it is indicative of endemicity for public health purposes and calls for intervention. The iodination of salt is both practical and feasible in Sri Lanka.

Adolescent↗
PubMed1988

Eimeria maxima (Apicomplexa): a comparison of sporozoite transport in naive and immune chickens.

This study compared the early stages of infection in naive and immune chickens infected with Eimeria maxima. An immunoperoxidase stain was developed and used to detect sporozoites and early schizonts in tissue sections of intestinal epithelium. A significantly higher proportion of sporozoites was present in the crypts of naive chickens, 48 hr postinoculation of oocysts, compared to immune chickens. Sporozoites in immune birds tended to remain in the lamina propria rather than migrate to the crypts. Sporozoites were found within intraepithelial lymphocytes (IEL's) in the epithelium, the lamina propria, and the crypts of both naive and immune chickens. Parasites in IEL's of immune birds at the ultrastructural level and there were no apparent morphological abnormalities. Livers and spleens, of both immune and naive chickens that had been inoculated with Eimeria maxima, produced patent infections when fed to susceptible chickens. Infections could be transferred up to 72 hr post-inoculation of the donor birds. Peak oocyst production in the recipient birds occurred 7-8 days after the transfers. This time period approximates the prepatent period in a natural infection and thus implies that the extraintestinal stage was a sporozoite.

Analysis of Variance↗
PubMed1987

Electron microscopic investigation of intracellular events after ingestion of Rhodococcus equi by foal alveolar macrophages.

It has been suggested that R. equi causes pulmonary disease in foals by persisting within the lung as a facultative intracellular parasite of alveolar macrophages. This paper describes an ultrastructural study of the intracellular events after ingestion of R. equi by foal alveolar macrophages, in an attempt to determine the mechanism of intracellular survival of R. equi. Secondary lysosomes of alveolar macrophages recovered from foals by bronchoalveolar lavage were labelled with electron-dense ferritin, and the cells were challenged with either viable or formalin-killed R. equi. After 0-, 3-, 8- or 24-h incubation, the cells were fixed and processed for electron microscopy. There was no evidence of phagosome-lysosome fusion after ingestion of either viable or non-viable R. equi by foal alveolar macrophages. Rhodococcus equi persisted and multiplied within dilated phagosomes, which were often lined by elongate microvillous structures. After 24-h incubation, 75% of the ingested bacteria were still structurally intact. Macrophages with ingested viable R. equi were irreversibly damaged and released intracellular bacteria into the surrounding medium. These data confirm that R. equi is a facultative intracellular parasite of foal alveolar macrophages and is able to persist and multiply within the phagosome, apparently inhibiting phagosome-lysosome fusion by some as yet unknown mechanism.

Animals↗
PubMed1987

Transport of Eimeria necatrix sporozoites in the chicken: effects of irritants injected intraperitoneally.

Light and electron microscopic observations confirmed that Eimeria necatrix sporozoites first enter villous epithelial cells of the chicken small intestine and are transported to the crypts by mononuclear cells. Ultrastructurally, these cells resemble granulated intraepithelial lymphocytes (IEL) rather than macrophages, as suggested previously. The injection of chickens intraperitoneally (i.p.) with a variety of irritants, including proteose peptone, at the time of oocyst inoculation or up to 12 hr postinoculation (PI) resulted in a delay in the arrival of sporozoites at the crypt. Significantly fewer sporozoites had arrived at the crypt by 24 hr PI in i.p.-injected birds as compared to controls. This delay in the arrival of sporozoites at the crypts was reflected by a delay in the development of intestinal lesions and in peak oocyst production. However, there was no significant decrease in the total numbers of oocysts produced by these birds as compared to controls, indicating that no significant loss of sporozoites occurs during the possible rerouting of the parasites. The presence of infective stages in extraintestinal sites was detected by transferring various tissues to coccidia-free recipients. Infection was transferable by gut, liver, and spleen from irritant-injected and control birds at all time intervals studied (12, 24, 36, and 48 hr PI). Infection was also transferable with blood and kidney, but not consistently. A small number of oocysts was passed by the recipients of peritoneal wash from irritant-injected birds at 12 hr PI. In all transfers, the prepatent period was normal, suggesting that the migrant stages are sporozoites.

Animals↗
PubMed1987

Eimeria spp. of domestic fowl: the migration of sporozoites intra- and extra-enterically.

Chickens were dosed orally with sporulated oocysts of Eimeria acervulina, E. brunetti, E. maxima, or E. praecox and the subsequent presence, in various tissues, of parasites capable of inducing patent infections was detected by transferring the tissues to coccidia-free recipients. Similar results were obtained with each of the 4 species studied, irrespective of whether initial development occurs in the superficial (E. praecox, E. brunetti) or crypt (E. acervulina, E. maxima) epithelium. Infection was transferable by gut scrapings and liver homogenates at all time intervals (3, 6, 12, 18, 24, and 36 hr postinoculation) studied. Infection was also transferable with blood and with splenic homogenates but not consistently. Transfers made within a short time of the inoculation of donors were more successful in producing patent infections in the recipients. In all transfers the prepatent period was normal for the species. These findings suggest that sporozoites enter the mucosa very shortly after inoculation, and some of them pass to the liver and spleen and then leave these tissues at a somewhat slower rate, possibly to reenter the mucosa. Sporozoites in the lamina propria of the gut were found within host mononuclear cells in all 4 species studied. Most of the cells harbouring E. maxima and some of those with E. praecox were identified as intraepithelial lymphocytes while all others could only be identified as agranular mononuclear cells that were not characteristically macrophages.

Animals↗