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Biomedical subjects

S C Rawlins

Publications and source records attributed to S C Rawlins.

At least 19 recordsLinked to original sources
PubMed2001

American cutaneous leishmaniasis in Guyana, South America.

The 185 patients who presented at the dermatology clinic of Georgetown Public Hospital, Guyana, between 1992 and 1998, with skin ulcers indicative of American cutaneous leishmaniasis (ACL) were retrospectively reviewed. The laboratory-confirmed cases of ACL were identified and the corresponding data were analysed for risk factors such as age, gender, areas of residence and of possible exposure to the causative agent (Leishmania braziliensis guyanensis), ethnic origin, longevity of the ulcers, and treatment regimes prior to the definitive diagnosis. Eighty-one (43%) of the 185 subjects were confirmed to be infected with Le. b. guyanensis. Although 53 (66%) of the cases lived in or close to the capital city, Georgetown, most of the cases had travelled to (and probably been infected in) region X in the interior of Guyana (32%) or regions VII (23%), VIII (23%), IX (11%), VI (5%), I (3%) or III (3%), usually because they were involved in the mining (41%) or lumber (21%) industries, the army or hunting. Almost all (95%) of the cases were male and most (58%) were aged 20-39 years. In general, the cases had had their skin lesions for many days before presenting for treatment: 46% for 1-5 weeks and 3% for > 6 months. Prior to presentation at the clinic, many of the cases had attempted to cure themselves, using local herbal remedies (37%), antibiotics and antifungal remedies (39%), other creams (5%), household chemicals (9%) or miscellaneous remedies such as lead salts (especially lead sulphate) and battery acid, all without success. Recommendations are made for an epidemiological study of active ACL among forest workers, eco-tourists and residents of high-risk areas. Diagnostic centres need to be sited in the regions most at-risk, particularly in or near environments in which the main vectors - sandflies such as Lutzomyia umbratilis, Lu. anduzei and Lu. whitmani - are known to be prevalent.

Adolescent↗
PubMed2000

Lymphatic filariasis in the Caribbean region: the opportunity for its elimination and certification.

In order to support the case for a certification of elimination of lymphatic filariasis (LF) in some Caribbean countries, we compared the prevalence of circulating Wuchereria bancrofti antigen in communities in Guyana, Suriname, and Trinidad. For the study, we assayed school children in six communities in Guyana, five communities in Suriname, and three communities in Trinidad for the prevalence of circulating W. bancrofti antigen, using a new immunochromatographic test for LF. We also assayed adults in these three countries, with a special focus on Blanchisseuse, Trinidad, where mass treatment for LF elimination had been carried out in 1981. The prevalences of W. bancrofti circulating antigen found in the school children populations ranged from 1.7% to 33.2% in Guyana and were 0.22% overall in Suriname and 0.0% in Trinidad. Among adults in two Guyana communities the prevalences were 16.7% and 32.1%. The results were all negative from 211 adults in communities in the north, center, and south of Trinidad, as well as from 29 adults in Suriname. The data suggest that contrary to reports of LF endemicity from the World Health Organization, LF may no longer be present in Trinidad and may be of very low prevalence in Suriname. Trinidad and Tobago and other Caribbean nations proven negative could seek to be awarded a certificate of LF elimination. In Suriname the small localized pocket of infected persons who may serve as a reservoir of LF infection could be tested and appropriately treated to achieve LF elimination. Such LF-positive countries as Guyana should access new international resources being made available for LF elimination efforts. An adequate certification program would help identify which countries should seek the new LF elimination resources.

Adult↗
PubMed1999

Ivermectin treatment of mansonellosis in Trinidad.

This study was conducted to determine the efficacy and long-term effects of an intervention programme based on a single dose of Ivermectin (6 mg) administered during a double-blind placebo study of 40 persons with Mansonella ozzardi infections in Blanchisseuse, Trinidad. After four years, ivermectin reduced microfilariae levels by 82.2%. Short- and long-term effectiveness of the drug is contingent upon the initial microfilariae levels of the patient. We conclude that a single dose of ivermectin reduces microfilariae densities and provides both short- and long-term reductions in M ozzardi microfilaraemia.

Adult↗
PubMed1998

Spatial distribution of insecticide resistance in Caribbean populations of Aedes aegypti and its significance.

To monitor resistance to insecticides, bioassays were performed on 102 strains of the dengue vector Aedes aegypti (L.) from 16 countries ranging from Suriname in South America and through the chain of Caribbean Islands to the Bahamas, where the larvicide temephos and the adulticide malathion have been in use for 15 to 30 years. There was wide variation in the sensitivity to the larvicide in mosquito populations within and among countries. Mosquito strains in some countries such as Antigua, St. Lucia, and Tortola had consistently high resistance ratios (RR) to temephos, ranging from 5.3 to 17.7. In another group of countries--e.g., Anguilla and Curaçao--mosquitoes had mixed levels of resistance to temephos (RR = 2.5-10.6), and in a third group of countries, including St. Kitts, Barbados, Jamaica, and Suriname, mosquitoes had consistently low levels of resistance to temephos (RR = 1-4.6) (P < 0.05). On occasion significantly different levels of resistance were recorded from neighboring A. aegypti communities, which suggests there is little genetic exchange among populations. The impact of larval resistance expressed itself as reduced efficacy of temephos to kill mosquitoes when strains were treated in the laboratory or in the field in large container environments with recommended dosages. Although a sensitive strain continued to be completely controlled for up to 7 weeks, the most resistant strains had 24% survival after the first week. By week 6, 60% to 75% of all resistant strains of larvae were surviving the larval period. Responses to malathion in adult A. aegypti varied from a sensitive population in Suriname (RR = 1.3) to resistant strains in St. Vincent (RR = 4.4), Dominica (RR = 4.2), and Trinidad (RR = 4.0); however, resistance was generally not on the scale of that observed to temephos in the larval stages and had increased only slightly when compared to the levels that existed 3 to 4 years ago. Suggestions are made for a pesticide usage policy for the Caribbean region, with modifications for individual countries. This would be formulated based on each country's insecticide-resistance profile. Use of physical and biological control strategies would play a more critical role than the use of insecticides.

Aedes↗
PubMed1998

A comparison of surveillance systems for the dengue vector Aedes aegypti in Port of Spain, Trinidad.

When the currently used larval surveillance system (visual inspection) for the dengue vector Aedes aegypti was compared with the surveillance for the presence of eggs by ovitrapping in Port of Spain, Trinidad, it was found that the latter (39.1%) was significantly more sensitive than the visual inspection system (10.1%). At the same time, the presence of the nuisance mosquito Culex quinquefasciatus was detected in 38.4% of the households. Both Ae. aegypti and Cx. quinquefasciatus showed preference for ovipositional attractants in ovitraps: hay infusion > yeast suspension > plain tap water. Although all the socioeconomic and geographic areas produced both mosquito species in 1996, upper middle class (UMC) areas (8.6-43.4%) produced more Ae. aegypti than did lower middle class (LMC) areas (7.8-38.8%), which produced more than working class (WC) areas (3.9-29.9%). For Cx. quinquefasciatus, the order of production was reversed with WC areas (50.1%) > LMC areas (30.0%) > UMC areas (26.0%). Change in vector surveillance strategies incorporating some ovitrapping and stratified sampling are recommended for Caribbean countries.

Aedes↗
PubMed1997

Evaluation of Caribbean strains of Macrocyclops and Mesocyclops (Cyclopoida:Cyclopidae) as biological control tools for the dengue vector Aedes aegypti.

Fifteen Caribbean strains of copepods were assessed for their predation ability against mosquito larvae. Macrocyclops albidus from Nariva. Mesocyclops aspericornis from Oropouche, and Mesocyclops longisetus from E1 Socorro, Trinidad, were most effective against Aedes aegypti but not against Culex quinquefasciatus. Mesocyclops longisetus and Me. aspericornis prevented any mosquito survival over 25 wk of observation despite weekly challenges with Ae. aegypti. The copepods were tolerant to dosages of the insecticide temephos that are usually toxic to mosquito larvae. This indicated that copepods could be incorporated into an integrated control system. To determine whether pathogenic microbes might be introduced with copepods into drinking water, microbial studies were done on the copepods. These showed the presence of only Aeromonas sobria, Pseudomonas sp., Alcalignes sp., and gram-positive bacilli. Although none of these are highly pathogenic to humans, the application of these copepods has not yet been recommended for use in drinking water.

Aedes↗
PubMed1995

Mass chemotherapy with diethylcarbamazine for the control of Bancroftian filariasis: a twelve-year follow-up in northern Trinidad, including observations on Mansonella ozzardi.

A microfilaria survey was conducted in Trinidad in 1992, 12 years after mass treatment with spaced doses of diethylcarbamazine citrate (DEC-C) for the control of Bancroftian filariasis; 348 persons were examined using thick blood smears and a membrane filtration technique. They included 104 who had participated in the mass chemotherapy campaign in 1980. No Wuchereria bancrofti microfilariae were detected among 66% of the population examined. In 1980, 86 of 592 persons examined were found to be infected with W. bancrofti, 140 with Mansonella ozzardi and 44 with mixed infections, while in 1992, only M. ozzardi infections persisted despite treatment with DEC-C. Of the 104 persons reexamined 12 years later, 46 had M. ozzardi, of which five were new cases, but none had W. bancrofti. During both the 1980 and 1992 surveys, low microfilariae rates for M. ozzardi were observed among those 19 years of age or younger. Of the 302 persons newly examined in 1992, 29 were infected with significantly (P < 0.001) more males (79.3%) than females (20.9%) being microfilaremic. The combined results showed similar prevalence rates for M. ozzardi from 23.3% to 21.6% in 1980 and 1992. Nuclepore membrane filtration and thick blood films were very efficient in demonstrating the presence of microfilariae. The usefulness of these methods and spaced treatment using DEC-C are also discussed.

Adolescent↗
PubMed1995

Resistance in some Caribbean populations of Aedes aegypti to several insecticides.

Thirty-four strains of Aedes aegypti larvae from 17 Caribbean countries were bioassayed for sensitivity to temephos, malathion, fenitrothion, fenthion, and chlorpyrifos. There were fairly high levels of resistance in Tortola (10-12-fold resistance) and Antigua (6-9-fold resistance) strains to temephos and to fenthion (Tortola, 7-10-fold; Antigua, 6-10-fold resistance). Most other strains showed some resistance to malathion, fenitrothion, and chlorpyrifos, but only moderate levels. Adult populations of Ae. aegypti--Aruba, Jamaica, Trinidad, Puerto Rico, St. Lucia, and Antigua strains--also showed moderate resistance to malathion. Mosquito control field data supported the laboratory findings. Doubling the diagnostic dosage of temephos for larval Ae. aegypti was only partially effective against a more resistant strain, and even so, the chemical lost its limited efficacy over a short period of time. Integrated strategies for Ae. aegypti control to mitigate the negative effects of insecticide resistance in the Caribbean strains are suggested.

Aedes↗
PubMed1994

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 microfilariae, 87.8% (ELISA IgG), 65.9% (ELISA IgM) and 73.2% (IHA) occurred in samples with sub-diagnostic 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% sensitivity, 96.4% specificity, 97.1% positive predictable value and 44.3% negative predictive value. A membrane filtration system (92.7%) was slightly better than a centrifugation technique (90.2%), but more efficient than a thick smear preparation (75.6%) for the detection of microfilariae. The filtration system was vastly superior for yields of microfilariae. 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%), followed by the broad 30-69-year age groups (10-12%). 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.

Adolescent↗
PubMed1993

Evaluation of methods for the laboratory diagnosis of malaria in Guyana.

When 297 blood samples taken from patients attending a fever clinic in Georgetown Public Hospital were examined microscopically, after thick and thin blood films had been stained with Giemsa, one hundred and forty-two (47.8%) were microscopically positive for malaria. After processing the patient's serum, samples by the Indirect Fluorescent Antibody (IFA) technique, specific IgG and IgM antibodies were detected in 239 (81.3%) and 179 (60.1%), respectively, of the sera. Based on the microscopical findings, the IFAT gave positive predictive and negative values of 54.4% and 81.8% (IgG), and 57.5% and 67.8% (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 were not. The microscopical method will continue to be the gold standard-the best available criterion for the validation of our tests-for diagnosis of acute malaria.

Animals↗
PubMed1993

Significant changes in gastrointestinal tract parasitic infections in children of St. Kitts over the 9-year period 1982-1991.

When 239 (1982) and 361 (1991) five- and nine-year-old children in St. Kitts were assessed for the presence of parasitic infections, there were significant reductions in the prevalence of trichuriasis from 83% to 58%, of ascariasis from 24% to 8.6% and of giardiasis from 15% to 9.4%. Anthelminthic use, which appeared to be the most important responsible intervention tool, remained roughly at the same level at 59-51%. However, the types of anthelminthics used changed over the period. Piperazine citrate, which was used by 66% in 1982, only had 35% usage in 1991. Albendazole which was not used at all in 1982 was taken by 32% of the children in 1991 and at the same time use of laevo-tetramisole increased by 20% from 14%. Suggestions are made for an island-wide mass intervention programme to manage parasitic infections.

Anthelmintics↗
PubMed1991

Effects of single introduction of Toxorhynchites moctezuma upon Aedes aegypti on a Caribbean Island.

In March 1989, first instar Toxorhynchites moctezuma larvae were introduced into all potential Aedes aegypti oviposition sites (n = 214) that contained water in the village of Clifton on Union Island in St. Vincent and The Grenadines. One month after this introduction, the mean number of adult Ae. aegypti collected with a backpack aspirator in houses in Clifton dropped significantly. Sixty-four percent fewer males and 80% fewer females were collected after introduction of the predator. In the untreated village of Ashton, the overall drop was 24%, with males showing an increase of 27% and females a drop of 55%. The average wing length of females collected in Clifton increased slightly, whereas it remained the same in Ashton.

Aedes↗
PubMed1990

Infective arthritis due to Blastocystis hominis.

A patient with rheumatoid arthritis taking prednisone developed Blastocystis hominis acute diarrhoea, which was associated with increased inflammation and effusion of the left knee. B hominis organisms were found in synovial fluid from the left knee. The patient responded dramatically to metronidazole treatment. B hominis may become disseminated in immunosuppressed patients with diarrhoea and may cause infective arthritis.

Adult↗
PubMed1990

Comparative organophosphorus insecticide 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 greater than Jamaica greater than Puerto Rico greater than St. Lucia greater than Trinidad greater than Union Island. Toxorhynchites moctezuma was much less susceptible to temephos than the Ae. aegypti strain, indicating its possible usefulness in an integrated management program.

Aedes↗