Belize Vector and Ecology Center monthly activity report February 2018

The Belize Vector and Ecology Center has embarked on vector surveillance initiatives that will allow us to determine changes in distribution and density of vectors and obtain information about population changes. In turn, this will allows us to monitor and evaluate adequate control methods. In this report, we have outlined the various activities that we have been conducting for the month of February.The Household Container Mapping is being conducted by teams consisting of BVEC employees and Vector Control representatives. So far we have mapped approximately 19.19% of the total structures in Orange Walk Town. Mapping data was updated for the month of February based on the amount of structures we did. Ovitrap Surveillance is being done in which 120 oviposition cups are set out to 60 pre-consented homes in Orange Walk Town. The hatch rate has been determined to be about 40% to 60% and there is interesting variation in the number of eggs collected per zone which may also be related to the position of ovicups and climatic conditions. The BG Sentinel Surveillance is being conducted in order to collect live adult Aedes mosquitoes in the field. There are 12 BG Sentinels in the town at 12 pre-consented homes. The traps so far have collected a number of Aedes mosquitoes as well as some from the Culex species and other types of flies. The adult Aedes mosquitoes collected in the traps are then sorted, identified and stored for testing using the Dengue Antigen Kit. Tests conducted so far have turned up negative which is a good sign and will continue testing while working on a pooling strategy depending on the number of adult females collected in the field. Larval Resistance Testing is another key component to the surveillance which will be done in conjunction with the ovitrap surveillance initiative. Currently eggs are being pooled and hatched so that there is enough larvae to meet the standard testing methods. BVEC also does Presentations and Training sessions in which we collaborate with schools and other groups to foster community engagement.

Back-projection and sensitivity analysis of the HIV-AIDS epidemic in the Caribbean

In this study we estimated past human immunodeficiency virus (HIV) incidence in 19 nations in the primarily English-speaking Caribbean and projected the course of the epidemic to the year 1999. We compared the results obtained from several different models of HIV incidence and different assumed incubation distributions. Linear and nonlinear optimization methods were used to fit several models (power, logistic, spline and step) to adult (age 15 years or older) AIDS incidence data derived from our existing surveillance system. All four models tested gave good fits to the data, with estimates of cumulative HIV incidence in 1993 ranging from 16,504 to 21,732. An increase in the assumed median of the AIDS incubation distribution by one year increased the estimates of current cumulative adult HIV incidence by approximately 12 percent; these estimates varied by as much as 6 percent between models. An adjustment of the data for possible reporting delay increased the estimates by approximately 7 percent and for underreporting by 25 percent. Despite their sensitivity to underlying assumptions, back-projection estimates provide useful insights into the patterns of HIV and AIDS incidence. The models indicate that HIV and AIDS incidences in the English-speaking Caribbean have been rising steadily, with adult HIV prevalence in the general population still less than 1 percent(AU)

A structured epidemic model incorporating geographic mobility among regions

A model for the spread of infectious diseases among discrete geographic regions is presented that incorporates a mobility process that describes how contact occurs between individuals from different regions. The general formulation of the mobility process is described, and it is shown that the formulation encapsulates a range of mobility behaviour from complete isolation of all regions (no mobility) to permanent migration between regions. It is then shown how this mobility process fits into an SIR epidemic model, and two examples are given extending its use. The examples include a model for disease transmission in a population with two distinct mobility patterns operating and a model developed to describe a 1984 measles epidemic on the Caribbean island of Dominica(AU)

A structured epidemic model incorporating geographic mobility among regions

A model for the spread of infectious diseases among discrete geographic regions is presented that incorporates a mobility process that describes how contact occurs between individuals from different regions. The general formulation of the mobility process is described, and it is shown that the formulation encapsulates a range of mobility behavior from complete isolation of all regions (no mobility) to permanent migration between regions. It is then shown how this mobility process fits into an SIR epidemic model, and two examples are given extending its use. The examples include a model for disease transmission in a population with two distinct mobility patterns operating and a model developed to describe a 1984 measles epidemic on the Caribbean island of Dominica (AU)

Evaluating a ten questions screen for childhood disability: reliability and internal structure in different cultures

This paper uses five strategies to evaluate the reliability and other measurement qualities of the Ten Questions screen for childhood disability. The screen was administered for 22,125 children, aged 2-9 years, in Bangladesh, Jamaica and Pakistan. The test-retest approach involving small sub-samples was useful for assessing reliability of overall screening results, but not of individual items with low prevalence. Alternative strategies focus on the internal consistency and structure of the screen as well as item analyses. They provide evidence of similar and comparable qualities of measurement in the three culturally divergent populations, indicating that the screen is likely to produce comparable data across cultures. One of the questions, however, correlates with the other questions differently in Jamaica, where it appears to "over-identify" children as seriously disable. The methods and findings reported here have general applications for the design and evaluation of questionnaires for epidemiologic research, particularly when the goal is to gather comparable data in geographically and culturally diverse settings (AU)

A comparison of efficacy of the key informant and community survey methods in the identification of childhood disabilities in Jamaica

A comparison of the efficacy of the key informant and the community survey methods for identifying children with disability was carried out in the Jamaican component of an international epidemiological study of children disability. Approximately 130 key informants were exposed to a two-day workshop giving information on sign of disability, aspects of the project, and available services. Questionnaires were given to enable the informants to refer children and they were reminded six months later. In the survey method, eight community workers completed a house-to-house survey of all families and administered the 10-question screen with probes on 5475 children, 2 to 9 years old. Seventeen referrals were made by the key informants; of these, two were found to have disabilities. Of the 821 children who tested positive on the 10-question screen on the house-to-house survey, 193 had disabilities. We concluded that the key informant method would not be a satisfactory way of identifying cases of childhood disability. (AU)

Comparative research in social epidemiology: measurement issues

The aim of comparative research in soical epidemiology is to determine how risk factors for disease may vary within and between sociocultural and ethnic groups and in relation to outcomes. This aim assumes that measurement equivalence within and between social groups can be established, an assumption usually left untested. A model is presented here for deriving cross-culturally valid measures that are also intraculturally sensitive. Measurements so derived can then be used to compare cross-cultural and intracultural effects in a single analytic model. This approach is illustrated by pooling data on social stressors, social supports, and blood pressure from three studies. (AU)

Persistence of leptospiral agglutinins in Trinidadian survey subjects

Participants in a survey for leptospiral agglutinating antibodies undertaken in Trinidad, West Indies, in 1977-78, were further monitored for up to 5-and-a-half years. 52 individuals with a titre >1:400 were matched for age, sex and occupation with seronegative subjects. They were re-bled twice (on average 2.38 and 4.84 years leater), and changes of titre were noted. At the first follow-up, 78 percent of negative controls remained negative, and 22 percent, showed titre changes. Among the seropositive subjects, 47 percent showed a fall in titre, 38 percent showed no change, and in 15 percent the titre rose. New exposure rates between the original and fist follow-up samples were 96/1,000 survey population per year in the controls, and 68/1,000 for the subjects with titres >1:400. Between the first and second follow-up, 47 percent ofthe seropositive subjects lost titre, 40 percent showed no change, and 13 percent showed a rise in titre. These data demonstrate that although antibody titre may be maintained for a few years at the same level, or show a loss as is usually expected, about 8.3 percent of individuals in Trinidad may be infected/reinfected per year. The infection/reinfection rate is an important factor in the epidemiology of leptospirosis. (AU)

A time-dependent logistic hazard function for modeling variable age of onset in analysis of familial diseases

This paper presents an extension of the regressive logistic model proposed by Bonney [Biometrics 42:611-625, 1986], to address the problems of variable age-of-onset and time-dependent covariates in analysis of familial diseases. The goal is achieved by using failure time data analysis methods, and partitioning the time of follow up in K mutually exclusive intervals. The conditional probability of being affected within the Kth interval (K=1...K) given not affected before represents the hazaard function in this discrete formulation. A logistic model is used to specify a regression relationship between this hazard function and a set of explanatory variables including genotype, phenotype of ancestors and other covariates which can be time independent. The probability that a given person either becomes affected within the Kth interval (ie. interval K includes age of onset of the person) or remains unaffected by the end of the Kth interval (ie. interval K includes age at examination of the person) are derived from the general result of failure time data analysis and used for the likelihood formulation. This proposed approach can be used in any genetic segregation and linkage analysis in which a penetrance function needs to be defined. Application of the method to familial leprosy data leads to results consistent with our previous analysis performed using the unified mixed model [Abel and Demenias, Am J Hum Genet 42:256-266, 1988], ie. the presence of a recessive major gene controlling susceptibility to leprosy. Furthermore, a simulation study shows the capability of the new method to detect major gene effects and to provide accurate parameter estimates in a situation of complete ascertainment. (AU)

Urban air pollution in Latin America and the Caribbean: health perspectives

In the last few years, air pollution has become a major issue in some countries of Latin America and the Caribbean because of urben development and growing industrialization. In addition to industrial processes often concentrated in the cities, vehicle emission and stationary-source fuel combustion are the primary source of air pollution. Although air-quality standards have been established in some Latin American countries, these are frequently exceeded. Adverse health effects of air pollution have been mainly associated with the following pollutants: sulfur dioxide and pariculate matter, photochemical oxidants, nitrogen dioxide and carbon monoxide, and lead. Short-term as well as long-term effects can be expected at levels exceeding WHO guidelines. The Latin American urban areas most affected by anthropogenic pollutant emissions are: the area of Sao Paulo (Brazil), the city of Santiago (Chile) and the metropolitan area of Mexico city. However, situations similar to those prevailing in these cities could well occur in other cities of latin America and the Caribbean. The population exposed to air-pollutant levels exceeding WHO guidelines can be estimated to 81 million or 26.5 percent of the total urban population of Latin America and 19 percent of its total population. These estimates correspond to 30 million children (0-14), 47 million adults (15-59) and 4 million elderly people (60+). To date a very limited number of epicemiological studies have been carried out to determine the potential health effects of air pollutants in Latin America. To obtain a rough estimate, a scenario was hypothesized in which subjects living in cities would be exposed to a given level of air pollutant, using data from the international literature to extrapolate the expected number of events in different strata of the hypothetical population. The estimated health effects are considerable and warrant priorty control intervention. This is true although epidemiological studies are needed to evaluate the health impact of specific pollutant compounds as well as their interactions in Latin American populations exposed to high levels of pollution. (AU)

Assesment of nutritional status: effects of different methods to determine age on the classification of undernutrition [published erratum appears in Bull World Health Organ 1989;67 (6):757]

The evalution of nutritional status using anthropometry has been widely employed in field studies and nutritional surveillance programmes. Two of the primary indicators used, weight-for-age and height-for-age, require accurate age information for proper assessments to be made. Three data sets on nutritional status were evaluted using different methods to determine age: rounding to the most recently attained month, rounding to the nearest whole month, and ages computed from birth dates and visit dates. The impact of these different methods on the classification of nutritional status were found to be dramatic, especially in infants during the first year of life. In some cases, when ages are rounded to the most recently attained month, as few as 43 percent of the children classified as malnourished based on the indicater, height-for-age, and the cut-off point, <-2 Standard Deviations from the refrence median, are identified relative to when ages are computed from birth and visit dates. Beyond the discrepancies in estimating prevalence below specific cut-off points to designate undernutrition, the use of the different methods also affects entire distribution. The problem of using different methods to estimate age, and the impact they have on the classification of undernutrition are of critical public importance, especially when this information is used to identify individuals and groups as well as planning and policy development. (AU)

Geographic distribution of HTLV-I and identification of a new high-risk population

Epidemiologic studies indicate that human T cell lymphotropic virus type I(HTLV-I), the causative agent of most cases of adult T-cell leukemia/lymphoma (ATLL)in Southeast Japan and the Caribbean islands and the probable cause of a progressive neurological disorder often referred to as tropical spastic paraparesis, occurs with unusual geographic clustering. The current large-scale serosurvey was undertaken to improve our understanding of HTLV-I prevalance in different parts of the world. We analyzed 43,445 serum samples collected from various geographic locales worldwide; 76 percent of these sera came from clinically healthy donors. Samples were initially screened by an enzyme-linked immunosorbent assay (ELISA) and 4,353 were further evaluated by means of competition assays. In this study, which did not include sera from endemic areas of Japan, a high prevalence of infection was observed in several countries in the Caribbean basin. A significant age-sex difference was observed between populations in the Caribbean and non-endemic regions of Japan. The reason for the male excess in non-endemic areas of Japan will require further study, while the female excess in the Caribbean basin is compatible with the previously described pattern for other HTLY-I-endemic areas. A newly recognized area of possible endemicity was southern Florida, where evidence of infection with HTLV-I or a related virus was found in a group of native Americans whose sera were collected in 1968. In certain parts of the world, particularly sub-Saharan Africa, important problems in determining specificity of reactivity occurred, probably because of cross-reacting antibodies. No pattern was detected that could explain the cross-reactivity solely on the basis of geographic areas, specific patterns of non-viral parasitic infection, or methods of handling the specimens. It is possible that these cross-reactivities are antibodies to proteins from HTLV-I-related retroviruses yet to be discovered. (AU)

The Caribbean Epidemiology Centre (CAREC)

The Caribbean Epidemiology Centre began operating on 1 January 1975 under the adminstrative management of the Pan American Health Organization (PAHO) at the request of the Caribbean Health Ministers' Conference held in the Bahamas in 1974. This presentation outlines the events leading to formation of the Centre and describes its structure, objectives, and development from January 1975 through 1978 (AU)

A review of cardiovascular diseases in developing countries

This review examines the possible association in undeveloped and developing communities between 'development' and blood pressure, coronary heart disease and rheumatic heart disease. Previous studies have shown that hypertension is rare and coronary heart disease almost unknown in many of the more isolated and less developed communities, whilst rheumatic heart disease is relatively common. Consideration is given to the possibility that development in such communities may lead to a higher incidence of hypertension and coronary heart disease and to a reduction in the amount of rheumatic heart disease. Epidemiological methods for separating environmental and genetic causes are discussed. Some more recent studies in genetically different 'primitive' groups are reviewed, and then methods are discussed for the control of the genetic component, based on the examination of one genetic group living at different levels of development, either at the same time or at different times. The advantages of using migrant studies are outlined and some examples are given. The evidence appears to favour the hypothesis that development is associated with a greater incidence of hypertension and coronary heart disease, but there is little to suggest that the incidence of rheumatic heart disease is decreasing with development (AU)

Fatal parathion poisoning caused by contamination of flour in international commerce

In January 1976, 79 persons in Jamaica were acutely poisoned by the organophosphorous insecticide parathion. Seventeen died. Cases occurred in three episodes at separate locations, but all patients had consumed wheat flour from a single lot consisting of 5264 cotton bags. Parathion in concentrations of <1 to 9900 ppm was identified in flour from six bags in this lot: three had splash marks. The flour had been milled in Wertern Europe from European wheat, carried in trucks to a dockside warehouse, and loaded aboard ship after 2-5 days' storage. In Jamaica, the flour had moved from quayside to outbreak locations along separate routes through two import houses. Site inspections and review of shipping records suggested that the likely point of contamination was the European port, where foodstuffs and insectisides were stored in the same warehouse (AU)

Outbreak of typhoid fever in Trinidad in 1971 traced to a commercial ice cream product

In April 1971, a nationwide outbreak of typhoid fever involving 132 persons occurred in Trinidad; there were no deaths. Eighty per cent of cases occurred in children ages 5-14, and more than 90 percent of ill persons lived or went to school in the main towns or in smaller communities along their connecting roads. The epidemic curve suggested a common source, and a series of food preference questionaires implicated a nationally distributed ice cream product. Further investigation indicated that the product was distributed on only one day, March 23. The mean incubation period was 19 days, and the attack rate for those at risk was slightly greater than 1 percent. Samples of the ice cream product obtained a month after the outbreak were found to contain greater than 1100 Escherichia coli per 100 ml. Inspection of the plant revealed frequent hand contact with the product and an absence of pasteurization facilities. Although rectal swabs and stool cultures obtained after purgation from employees failed to identify the carrier, epidemiologic evidence suggested that an employee in the plant, rather than a contaminated ingredient, was the source of the outbreak. This outbreak emphasizes the need for mandatory pasteurization of milk and ice cream products, especially when strict sanitary procedures cannot be adhered to or enforced (AU)

The status of maternal and child health services for Jamaica with particular reference to the metropolitan parishes of Kingston and St. Andrew

Jamaica is a small developing country with a low gross national domestic product. Nevertheless, it is advocated that resources be allocated to maternal and child Health services because children are the future of the nation; women and children form a considerable portion of the population; many causes of illness in women and children are preventable; and maternal and child health services form a good vehicle for education of the family for healthful living. Maternal mortality data are used as the main indices of maternal health. Maternal mortality rates are falling, but are still higher than in certain countries of Latin America and in the developed countries. Haemorrhage has replaced toxaemia as the main cause of maternal mortality, but toxaemia is still important. Significant contributions to maternal mortality are made by abortion and sepsis. Maternal mortality is less where there is antenatal care. Anaemia in pregnancy is very prevalent as are positive reactions to serological tests of syphilis. Infant mortality rates have fallen progressively. Death rates in the second year of life and in the 1 - 4 year age group have also fallen but are still many times the equivalent rates in the United Kingdom. Data for the first year of the Inter-American Investigation of Childhood Mortality are presented. The true death rates in the under 5 age group are higher than officially reported because of under registration of deaths. Nutritional deficiency as underlying or associated cause contributes to 31.7 percent of all deaths under 5 years of age (excluding neonatal deaths) and is most marked in the postnatal period. Diarrhoeal disease is also an important cause of death. Nutritional deficiency as judged by weight for age is present in over 40 percent of children under five years. Jamaica spends 8 percent of its annual budget on Health, but per capita expenditure is low. There are only 710 doctors with very few obstetricians and paediatricians. 34.5 percent of the births in 1970 were attended by unqualified attendants, and the resources at the main maternity hospital are severely taxed. There are also shortaged of Paediatric beds. Only two-thirds of the established posts for public health nurses are filled. The main problems in maternal and child health are discussed and it is recommended that greater emphasis be given to maternal and child health, that maternal and child health units be established in the Ministry of Health and large Health Departments and that family planning services be integrated with maternal and child health services. Maternal mortality review committees should be established and the statistical services should be improved (Summary)

The use and interpretation of ponderal index and other weight-height ratios in epidemiological studies

Criteria for an index of weight corrected for height are presented and used to investigate, both theoretically and practically, the properties of three weight-height ratios: weight/height, weight height 2 and ponderal index. The data on height, weight and skinfold thickness used in the analysis were collected during the fourth examination of the Framingham study. Based on the criterion that the ratio should be independent of height, the best of the three proposed ratios depends on the value of the intercept and the coefficient of the regression of weight on height for the population under consideration. The most likely best ratio in Western male populations is weight /height2 and it seems probable that in Western female populations it is weight/height: the least likely for both sexes is ponderal index. Evidence is also given to show that all three indices are poor measures of adiposity (Summary)