Microscopical and serological diagnosis of wuchereria bancrofti

Venous blood from 292 patients attending a Filaria Clinic in Georgetown, Guyana, was assayed by ELISA for IgG and IgM antibodies and by Indirect Haemagglutination Antibody Assay (IHA) against filaria parasites. They were also assayed by microscopic methods before and after concentration procedures for microfilaraemia. Of the 41 blood samples microscopically positive for Wuchereria bancrofti microfilfariae, 87.8 percent (ELISA IgG), 65.9 percent (ELISA IgM) and 73.2 percent (IHA) occurred in samples with subdiagnostic serological threshold titres of<1:32 (IgG and IgM) and <1:128(IHA). But indicators of value based on the standards of the presence of chronic and acute symptoms, the IgG and IgM diagnostic data gave 79.9 percent sensitivity, 96.4 percent specificity, 97.1 percent positive predictable value and 44.3 percent negative predictive value. A membrane filtration system (92.7 percent) was slightly better than a centrifugation technique (90.2 percent), but more efficient than a thick smear preparation (75.6 percent) for the detection of microfilariae. The filtration system was vastly supeior for yields of microfilariae. However, the Knott's concentration (sedimentation) was the most economical in terms of technical time and materials. Most microscopically confirmed filaria cases were in the 20 - 29-year age group (25 percent), followed by the broad 30--69-year age groups (10-12 percent). Males were significantly more commonly affected by the ratio 24.2:6.0. It is recommended that skills and materials for concentration of microfilariae from peripheral blood be maintained in all Caribbean countries. In known filaria endemic countries, it is recommended that the serological tool be used as an aid in diagnosis for patients with acute and chronic symptoms. (AU)

Water storage and dengue in Trinidad and Tobago: community perception and reality - abstract

A knowledge, attitude and practices (KAP) survey of 591 householders and inspection of 753 households for production of the dengue vector Aedes aegypti revealed that as many as 78 percent of households in Trinidad and Tobago stored water. Tanks (63 percent), drums/barrels (29 percent) and buckets (26 percent) were the commonest potential vector production sites, while drums >cans>buckets>tyres, proved to be the major actual producers of Ae aegypti. However, most of these were perceived as "useful by 100 percent of the population; 60 percent thought that old tyres were "useful" and only containers such as coconut shells and small bottles were perceived by 40 percent of the population as "garbage". Special messages of mosquito source reduction will need to be designed. Dengue was recognized as a "serious" illness but only 54 percent were aware of its manifestations. The urban population of Woodbrook where the experience of dengue (16.3 percent) was highest could better tell of the symptoms of dengue (56.8 percent). Conversely, in Tobago with no history of the disease, only 18.3 percent knew of any symptom of the illness. The community that had experienced the highest dengue prevalence as a whole showed least mosquito production - based on the house, container and Breteau indices for the whole country. The authors conclude that health education messages which emphasize the symptoms of Dengue and especially Dengue Haemorrhagic Fever (DHF) and link the transmission of these diseases to the nuisance mosquito, Ae, aegypti, may be one of the most important tools encouraging behaviour modification. This could lead to reduced mosquito production and a mitigation of dengue transmission (AU)

Evaluation of methods for the laboratory diagnosis of malaria in Guyana

When 297 blood samples taken from patients attending a fever clinic in Georgetowm Public Hospital were examined microscopically, after thick and thin blood films had been stained with Giemsa, one hundred and forty-two (47.8 percent) were microscopically positive for malaria. After processing the patients' serum samples by the Indirect Fluourescent Antibody (IFA) technique, specific IgG and IgM antibodies were detected in 239 (81.3 percent) and 179 (60.1 percent), respectively, of the sera. Based on the microscopical findings, the IFAT gave positive and negative values of 54.4 percent and 81.8 percent (IgG), and 57.5 percent and 67.8 percent (IgM), suggesting that the IgM would be more useful than the IgG in the diagnosis of current malaria. An odds ratio analysis showed that the presence of symptoms, IgG or IgM antibodies, as well as visits to endemic regions, could be good indicators of current malaria. Age and occupation are not. The microscopical method will continue to be the gold standard - the best available criterion for the validation of our tests - for our diagnosis of acute malaria. (AU)

Significant reductions in the rates of gastrointestinal tract parasitic infections in children of St. Vincent over a thirteen-year period (1979-1992) - abstract

When 314 (1979) and 207 (1992) five- to nine-year old school children in St. Vincent were investigated for the presence of parasitic infections, there were significant reductions in the prevalence of trichuriasis (75 per cent to 21.7 per cent), ascariasis (37 per cent to 8.6 per cent), amoebiasis (9 per cent to 2.8 per cent) and giardiasis (10 per cent to 5.3 per cent) over the 13-year interval. Anthelminthic use remained at 63 - 65 per cent, but the brands of worm medicines taken changed over the period. Thus, whilst piperazine citrate was used by 41 per cent of the children in 1979, only 4.8 per cent of them used it in 1992. Albendazole which was used by a great majority (42.5 per cent) in 1992 was never used in 1979. Commensals were observed in 211 (67 per cent) children in 1979, and in 83 (40 per cent) children in 1992 (AU)

A comparative study of available diagnostic tools for lymphatic filariasis - abstract

Venous blood from 300 patients attending a filaria clinic in Georgetown, Guyana, was taken and assayed by ELISA for IgG and IgM antibodies against filaria parasites, and by microscopic methods before and after concentration procedures for microfilaraemia. Negative serum titres (<1:32) of IgG and IgM coincided with 90 per cent and 65 per cent, respectively, of positive microscopy. A membrane filtration system (95 per cent) was slightly better than a centrifugation (92.5 per cent) technique, but significantly more efficient than a thick smear preparation (75 per cent) for the detection of microfilaraemia. The filtration system was vastly superior for yields of microfilaria. However, the Knott's concentration (sedimentation) was the most economical in terms of technician time and materials. Most microscopically confirmed filaria cases were in the 20 - 29 year-age group (25 per cent), followed by the broad 30 - 69 year-age group (10 - 12 per cent). Males were more commonly affected by the ratio of 2.6 : 1. Symptoms included swollen limbs, tenderness, fever, swollen glands, headache and joint pains but 17 (42.5 per cent) patients were asymptomatic (AU)

The comparative value of various diagnostic tests for malaria - abstract

When 300 blood samples taken from patients attending a fever clinic in Georgetown Public Hospital were examined microscopically, 47.6 percentwere found positive for malaria. IgG antibodies stored in filter paper or liquid serum gave 68 percent and 81 percent positive rate, repsectively. Sixty-one per cent (61 percent) of the patients had positive levels of IgG antibodies. Elevation of the cut-off point of IgG antibody titres from 1:256 to 1:1,024 help to reduced false positives of the indirect flourescent antibody test. Clinical symptoms, visits to endemic areas, occupation and its life styles, as well as age could assist in making a diagnosis. The microscopic method will continue to be the gold standard (AU)

Comparative organophosphorus insecticides susceptibility in Caribbean populations of Aedes aegypti and Toxorhynchites moctezuma

Aedes aegypti larvae from Antigua, Jamaica, Puerto Rico, St. Lucia, Trinidad and Union Island and predatory larvae, Toxorhynchites moctezuma, from Trinidad were tested for susceptibility to temephos, malathion, fenthion, fenitrothion and chlorpyrifos. There was some organophosphorus resistance in all strains of Ae. aegypti, in the approximate order: Antigua>Jamaica>Puerto Rico> St. Lucia> Trinidad> Union Island. Toxorhynchites moctezuma was much less susceptible to temephos than the Ae. aegypti strain, indicating its possible usefulness in an integrated management program. (AU)