An investigation of some risk factors for severe leptospirosis on Barbados

Between November 1979 and the end of December 1986 (7.17 years), 248 cases of leptospirosis were confirmed among hospital patients on Barbados (mean 35 per year; range 25-57). Considering the 235 who were greater than or equal to 15 years of age, the annual incidence of leptospirosis was 19.2/100,000 population (14.0 for all age groups). There were 173 males and 62 females, and for cases aged 15-34 leptospirosis was 9.6 times more common in men than women. Among men, incidence increased fairly steadily with age, and an even steadier increase was apparent in women up to age 64, with some decline in later years. The incidence of disease was much higher among agricultural than other workers and the un-employed. Highest case numbers were recorded in the parishes of St Michael (65 or 28 percent) and Christ Church (36 or 15 percent), though the incidence was lowest in these two parishes (13.1/100,000 and 17.4/100,000, respectively). The highest incidence rates were in St Andrew and St Joseph ((50.2 and 36.1/100,000, respectively). The incidence in areas with rainfall greater than or equal to 1600 mm (32.6/100,000) was nearly twice that in areas with rainfall less than 1600 mm (17.3/100,000). There is a clear link between cases of severe disease and recent rainfall. Using 134 patients greater than or equal to 15 years of age with fever due to other illnesses as controls, a higher proportion of cases than controls came from rural areas. The risk of contracting leptospirosis was increased for all categories of manual workers relative to the group at lowest risk (non-manual indoor workers). Sugar-cane workers were five times more likely to contract leptospirosis than were non-manual indoor workers, while those with rodents in their garden/yard were 1.8 times more likely to do so. Other risk factors examined did not show significant associations with the disease. Despite increasing mechanization and the use of more protective clothing, agricultural workers are still at high risk from leptospirosis. The annual range of cases is likely to stay much as it is in the foreseeable future. (AU)

Human T-lymphotropic virus type I (HTLV-I) seroprevalence in Jamaica - II geographic and ecological determinants

An island-wide cohort of 13,260 Jamaicans who applied for food-handling licenses during 1985 and 1986 were tested for antibodies to human T-cell lymphotropic virus type I (HTLV-I). Demographic and residence history data were linked to geographic measures of elevation, rainfall, crop-growing areas, population density, and additional measures of urbanization and correlated with HTLV-I antibody status. By logistic regression analysis (performed separately for men and women), men and women who currently resided at low elevation (ó1,000 ft (305 m)) were more likely to be HTLV-infected than were those residing at high elevation. Men, but not women, who were born in citrus-growing areas were more likely to be HTLV-I infected than were men who were born in other areas. By univariate analysis, there was a significant positive trend of increasing HTLV-I seroprevalence with increasing amount of annual rainfall associated with birthplace and primary residence areas. However, these associations did not remain in significance after adjusting for age and sex. These environmental associations raise the possibility of new modes of viral transmission or host response to infection, although they may simply be surrogates for socioeconomic status, breast-feeding habits, or sexual behaviour, which are known determinants of HTLV-I zero prevalence. (AU)

Seasonal abundance and diel landing periodicity of Sabethes chloropterus (Diptera: Culicidae) in Trinidad, West Indies

The seasonal occurrence and diel landing periodicity of Sabethes chloropterus (Humboldt) was studied weekly for 1 yr using the human bait catch in the Pt. Gourde Forest, Trinidad, WI. Population abundance remained low throughout the dry season (16 percent) but increased after the onset of the rains in May and peaked by the middle of the rainy season (July-October). The diurnal periodicity of landing was unimodal during the wet season with a major peak between 1200-1600 hours and bimodal during the dry season with peaks at 0800-1000 hours and 1200-1400 hours. This study documents for the first time the periodicity of landing by Sa. chloropterus at ground level and suggests reasons for failure to detect the yellow fever virus at this level. (AU)

Observations on the seasonal incidence and diel oviposition periodicity of haemagogus mosquitoes (Diptera: Culicidae) in Trinidad, W.I.: part I

The diel oviposition periodicity of sylvan Haemagogus janthinomys Dyar in the Pt. Gourde Forest, Trinidad, West Indies was monitored weekly for 53 weeks using conventional ovitraps. During the wet season (September to November 1981 and May to September 1982) a large well-defined unimodal peak occurred six to eight hours after sunrise (comprising 94 percent of eggs laid and 91 percent occurrences). During the dry season (December 1981 to May 1982), a small less-well-defined peak occurred two to four hours before sunset (comprising 6 percent of eggs laid). The combined data showed a diurnal oviposition pattern with eggs laid from noon to sunset. The numbers of eggs and of used ovitraps found during the wet season were significantly (P<0.001) higher than those found during the dry season.(AU)

Effects of 'closed' houses on the Aedes aegypti eradication programme in Trinidad

The effects of closed (i.e. locked) houses on the efficiency of control measures against Aedes aegypti (L.) were monitored weekly for 1 year (March 1981 to February 1982) using ovitraps in the towns of Felicity and Trinicity, treatment with larvicidal 1 percent temephos sand granules and perifocal treatment with 40 percent wp fenthion. In Felicity, only 6 percent of houses were closed and after each treatment cycle ovitrap indices showed 100 percent control. In Trinicity, 32 percent of houses were closed and after each treatment cycle reductions in ovitrap indices were less than 50 percent. Ae. aegypti eggs sampled in ovitraps totalled 493 (1-70 per positive paddle) in Felicity and 2310 (1-75 per positive paddle) in Trinicity. Ae. aegypti was successfully eliminated from Felicity during weeks 40-52 using focal/perifocal treatment monitored by ovitraps. Control failure in Trinicity was attributed to the survival of untreated Ae. aegypti populations in closed houses. Recommendations to improve gaining access for inspection and treatment of closed houses include having control/surveillance workers commence activities at 06.00 hours on weekdays, to work at weekends or during school holidays, or as a last resort to invoke court orders against households harbouring Ae. aegypti. (AU)

The medical geography of clinical leptospirosis in Barbados 1976 to 1982

This study examines the inter-relationship of the factors: host, agent and human activity in producing clinical leptospirosis in Barbados from 1976 through 1982. These inter-relationships are examined at 2 levels: the macro (parish) and the micro (district) levels. At the macro level the factors of rainfall, drainage and involvement in agriculture were found to have significant associations with the average morbidity pattern. When plotted relative to rainfall, 71.8 percent of the cases occurred in locations and months of above average rainfall. When plotted relative to drainage, 91.3 percent of the cases occurred in areas below 250 ft., where clay infilling in watercourses produced flood-prone environments, or in areas above 250 ft. which were within 220 yd. of watercourses. The net result is that rainfall and drainage combined accounted for 98.5 percent of cases at this level. The Rainfall-Agricultural Involvement multiple regression model explained 60 percent of the variation in parish morbidity over the time period. These factors, however, did not adequately explain micro-level patterns of morbidity. To understand these, human activity was examined. This analysis utilized an adaptation of 2 methodologies - the 24 hr. Recall Technique and Water Contact Studies. These were used to determine exposure to the physical environment, and its relation to the pattern of morbidity. For this examination 2 areas were studied - St. Philip South-West, a high morbidity area with more cases than could be explained by the moisture factor alone, and St. James East, with fewer. Exposure to the physical environment was found to vary according to location, sex and the pattern of human activity. These all had strong associations with morbidity. The micro-level study revealed that there are 2 distinct spheres of exposure - the home and the work environments - and there tends to be little overlap in these 2 spheres. The study also revealed that there was a spatial variation in the nature of contact with the environment which may be an important consideration in explaining the micro-level pattern of morbidity. (AU)

Seasonal variation in the population density of larvae of Boophilus microplus (Canestrini) (Acari: Ixodoidea) in Jamaican pastures

A study was made of the seasonal variation in population density of larvae of Boophilus microplus (Can.) in four locations in Jamaican pastures where the mean annual precipitation ranged from 59 to 222 cm. Variations in popualation density were related to rainfall. Generally, four months of heavy rains in August to November preceded singnificant increases in B. microplus populations in December to February, This was followed by a reduction then another slight increase, resulting in a bimodal pattern of activity. Although populations fell to very low levels by the end of the dry season, only in one focus were they depleted to undetectable levels.(AU)

The problem of human leptospirosis in Barbados

The results of a retrospective study of human leptospirosis cases occurring in Barbados during the period 1968-74, and of serological findings among high risk occupational groups, fever cases and health care patients monitored for the disease during 1975-77, indicate that infection by serotype fort-bragg of the Autumnalis group is widespread in this Caribbean island. The occupational groups most affected are sanitation workers and sugar-cane workers. Results of serological tests conducted at the principle hospital are comparable with the results obtained by the microscopic agglutination reference test procedure conducted at the Pan American Zoonosis Centre (CEPANZO) Summary

Contaminated roof-collected water as a possible cause of an outbreak of salmonellosis

Roof-collected rainwater is a common source in subtropical regions and has not been associated with human illness. In Trinidad, the West Indies, a church group attending a rural camp, developed gastrointestional illness, caused by Salmonella arechevalata. This rare serotype was isolated from stool specimens of campers, food eaten at the camp, and a water tap, which was supplied by a storage tank of roof collected rainwater. The surface of the roof, used as water catchment, was covered with bird faeces. It is postulated that rainwater, falling on the roof, washed off animal excrement which contained S. archevalata and led to the outbreak of salmonellosis through camper ingestion of contaminated food and water.(Summary)

The development distribution and availability of water in north Manchester

The development, distribution and availability of water in North Manchester is discussed. The sources and quality of water as well as the sophistication of the supply (whether house connection or standpipe) were discussed. Proximity of standpipes and the ratio of people per standpipe was stressed as an area of importance. Training of personnel directly responsible for the operation of the water supply is emphasized. (AU)

Control of Schistosoma mansoni transmission by chemotherapy in St. Lucia. II. Biological results

Chemotherapy of all persons infected with Schistosoma mansoni was begun in Marquis Valley, St. Lucia, in March 1974. From January 1972 to the start of chemotherapy, the infection rate in field Biomphalaria glabrata collected in the valley was 1.09 percent (117/10,736) and the rate in sentinel B. glabrata was 1.48 percent (56/3,790). From March 1974 through December 1975, no infections were detected in either field snails (11,742 collected) or sentinel snails (3,230 exposed). The accumulation data suggest that, because of differences in topography and average annual rainfall, S. mansoni transmission occurs in this valley during the rainy season, whereas in other St. Lucian valleys under study it occurs during the dry season (AU)

The influence of rainfall on the dynamics of some mosquito populations in savanna area of Surinam

Weekly collections of adult female mosquitos were made near Powaka, an Amerindian village, located in the savanna belt of northern Surinam. Culex portesi Senevet and Abbonnenc, C. spissipes (Theobald) and C. mollis Dyar and Knab were the most abundant mosquito species. In order to better understand the population dynamics of these species, correlation coefficients were calculated between population density and rainfall in consecutive weeks prior to the week of the "index catch". Also the relationships between parous rate and population density were analysed. It is concluded that the duration from egg hatching to first adult blood meal of Culex mollis, C. spissipes and C. portesi may take approximately 1 week, 3 to 4 weeks and 5 weeks, respectively. The length of the gonotrophic cycle is estimated to be about 3 weeks for Culex mollis and 2 weeks for C. spissipes as well for C. portesi. (AU)

Climate and painful crisis of sickle-cell disease in Jamaica

In a 10-year retrospective study a close correlation was found between low temperatures and hospital admissions for severe painful crises of sickle-cell disease.(Summary)

Public water supply in the Parish of Manchester

Since the establishment of bauxite mining and processing plants in the Parish of Manchester, rapid urbanisatiion has taken place and the water supply has become inadequate to supply the needs of the population. Recommendatons are made as to how the situaton may be improved. (AU)

Some components of the air spora in Jamaica and their possible medical application

The air spora was sampled at a single site in Jamaica from May 9, 1968 to May 9, 1969, using a Hiret spore trap. The components of the air spora were analysed to determine their frequencies, and an attempt has been made to explain their distribution with respect to changing environmental factors. Fungal spores were found to be the numerically dominant members of the air spora, comprising 98.73 percent whilst pollen comprised 0.40 percent of the total material observed. Few spore types made up the majority of the fungal of the fungal air spora, namely Cladosporium, Sporobolomycetaceae group, Diatrype, Glomerella, hyaline and coloured basidiospores, and septate fusiform spores. Seasonal periodicity studies on 25 fungal types showed that 16 attained a high number of spores released during wet periods, 4 during cooler months, and 5 showed no seasonal trends. Diurnal periodicity studies on 25 fungal spore types showed all had a maximum release of spores at some time during the day. However, this maximum release of spores was shown, for some spore types, to reflect the diurnal periodicity of rainfall whilst in others the diurnal periodicity persisted for up to 6 days after rainfall had ceased. The magnitude of the maxima for the numbers of spores released was also amplified by rainfall. Investigation of the effect of rainfall on the numbers of spores released showed that the amount and duration of rainfall, the time of day rain occurs, and the lenght of the dry period preceding rain were of varying importance to particular spore types. It was shown that meteorological factors, in particular rainfall, can greatly influence the numbers of the air spora. Thus changes in the weather can profoundly affect the allergic patient. (AU)