Comparison of mosquito control programs in seven urban sites in Africa, the Middle East, and the Americas

Mosquito control programs at seven urban sites in Kenya, Egypt, Israel, Costa Rica, and Trinidad are described and compared. Site-specific urban and disease characteristics, organizational diagrams, and strengths, weaknesses, obstacles and threats (SWOT) analysis tools are used to provide a descriptive assessment of each mosquito control program, and provide a comparison of the factors affecting mosquito abatement. The information for SWOT analysis is collected from surveys, focus-group discussions, and personal communication. SWOT analysis identified various issues affecting the efficiency and sustainability of mosquito control operations. The main outcome of our work was the description and comparison of mosquito control operations within the context of each study site's biological, social, political, management, and economic conditions. The issues identified in this study ranged from lack of inter-sector collaboration to operational issues of mosquito control efforts. A lack of sustainable funding for mosquito control was a common problem for most sites. Many unique problems were also identified, which included lack of mosquito surveillance, lack of law enforcement, and negative consequences of human behavior. Identifying common virtues and shortcomings of mosquito control operations is useful in identifying "best practices" for mosquito control operations, thus leading to better control of mosquito biting and mosquito-borne disease transmission.

Sistemas de proteccion social para el adulto mayor en America Latina y el Caribe / Social protection systems for older adults in Latin America and the Caribbean

Only one half (50.1 percent) of all older adults in Latin America currently receive benefits under some form of social protection system for the elderly, either through social assistance or social security programs, or have access to a savings plan for old age in the form of individual capitalization accounts (ICA) based on mandatory or voluntary contributions. The other half enjoys no social protection at all; its consumer and health needs are covered through accrued assets, voluntary family transfers, or charitable deeds. Social security pension plan reforms and the creation of social-security-based savings plans for old age in the form of ICA have failed to yield the expected results in terms of coverage and benefits. Over-all, reforms have led to the dismantling of social-security-based social protection systems for the elderly without creating alternative mechanisms for social protection. This document describes the various social protection systems and savings plans for old age that are in place in countries of the Region and looks at current challenges in terms of correcting "government failures" and applying policies that will redress "market failures", so that the working population can count on having enough resources to satisfy its consumer and health needs after retirement (AU)

Social networks in the guppy (Poecilia reticulata)

Social network theory is used to elicit details of the social structure of a population of free-ranging guppies, Poecilia reticulata. They were found to have a complex and highly structured social network, which exhibited characteristics consistent with the 'small world' phenomenon. Stable partner associations between individuals were observed, a finding that fulfils the basic prerequisite for the evolution of reciprocal altruism. The findings are discussed in relation to the ecology and evolution of the wild population, highlighting the potential application of network theory to social associations in animals.

Connectivity of marine populations: open or closed?

Most marine populations are thought to be well connected via long-distance dispersal of larval stages. Eulerian and Lagrangian flow models, coupled with linear mortality estimates, were used to examine this assumption. The findings show that when simple advection models are used, larval exchange rates may be overestimated; such simplistic models fail to account for a decrease of up to nine orders of magnitude in larval concentrations resulting from diffusion and mortality. The alternative process of larval retention near local populations is shown to exist and may be of great importance in the maintenance of marine population structure and management of coastal marine resources.(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)

Preliminary observations on the changing roles of malaria vectors in southern Belize

A survey for larval and adult anopheles mosquitoes was conducted in Toledo District of southern Belize during August-September 1992. We surveyed for larvae in 145 habitats and conducted paired indoor-outdoor collections of adult mosquitoes landing on humans at 6 houses. In 1940-41, Kumm and Ram reported Anopheles darlingi females to be the most common Anophales mosquitoes inside houses and reported no specimens of Anophales vestitpennis in southern Belize. In our 1992 survey we found no An. darlingi mosquitoes either as adults or larvae. More An. vestitipennis females were captured indoors than outdoors, whereas most Anopheles albimanus and anophales apicimacula females were captured outdoors. All 3 species were represente occasionally in 145 collections of larvae from diverse habitats. Anophales vestitipennis now appears to be potentially important vector of malaria during the wet season in Toledo District (AU)

An epidemiological study of the Jamaican elderly

Populations across the world are ageing in terms of years of life after 60 and the section of the population referred to as the elderly is growing at a rapid rate. Among the countries of the developing world, the Caribbean including Jamaica has the oldest elderly population. The experience of the developed world is that elderly related issues are many and diverse. This study examines the history of public health contributions to the successful ageing of the Jamaican population. The study also examines the demographic, health and nutritional features of the elderly population. Social, economic and health related issues are defined and used to make recommendations for future policy and programmes. The Jamaican elderly population now comprises over ten percent of the total population. The elderly however are for the most part both mentally competent and physically independent. The elderly continue to live in family units and the family is the main source of support both emotional and financial. The study identified the older female especially those over 80 as being more likely to be alone and "at risk". Overall the elderly were healthy and the major chronic diseases identified were hypertension and diabetes and women were affected more than men. In addition obesity was identified as the main nutritional problem (AU)

Family planning in St. Vincent, West Indies: a population history perspective

St. Vincent's population history, first as a slave society, then, after Emancipation, as a migration-oriented society, has strongly influenced cultural attitudes towards sexuality and fertility. In contemporary St. Vincent, sexual activity and procreative ability are highly valued and linked to social status for both men and women. This paper assesses historical and contemporary factors influencing population dynamics in St. Vincent, West Indies, and Vincentians' reactions to programs developed to curb population growth. The efforts of private and government programs to introduce family planning and change pronatalists attitudes are evaluated for their cultural appropriateness. Shifting migration patterns and modernization are also affecting gender roles, the social and economic value of children, and the acceptability of contraception to contribute to recent fertility declines (AU)

Migrants and their therapists: a trans-context approach

In this article, I examine how changes in technology, social organization, and economic opportunity are fundamentally altering the encounter between therapists and migrant clients. Approaches are required that take into account the recursive nature of the newly emerging two-home, trans-context lifestyle. I outline a second-order position and lines of questioning that may help migrants and therapists to situate problems in historical-geographical context, examine structural constraints on choice, and co-develop options for the future. To illustrate and enlarge upon hypotheses about the life experience of migrants, I analyze a particular Caribbean-Canadian immigrant story. (AU)

Epidemiology and population dynamics of Ascaris lumbricoides and trichuris trichiura infection in the same community

The gastrointestinal helminth infection status of an age-stratified sample from a single Caribbean community was assessed using anthelmintic expulsion techniques. The same sample was re-assessed in a similar manner after a 17 month period of re-infection. The age-prevalence profile of Ascaris lumbricoides was convex while that of Trichuris trichiura was asymptotic. The age-intensity profiles of both species were convex. These differing patterns are attributed to differences in the absolute worm burdens of the 2 species. The frequency distributions of infection intensity were similar for both species, and largely independent of host age. The basic reproductive rate of A. lumbricoides (R. = 1-1.8) was similar to that recorded elsewhere and much lower than that of T. trichiura (R. = 4-6), implying that the latter is intrinsically more resistant to control. Individual hosts were predisposed to high (or low) intensity infection with either species, although predisposition to both species simultaneously was not conclusively demonstrated. Futher studies are required to determine the cause of these observations.(AU)

Population dynamics and chemotherapeutic control of Trichuris trichiura infection of children in Jamaica and St. Lucia

Population dynamical parameters of Trichuris trichiura infections in children were estimated from longitudinal intensity and prevalence data from a population (n=23) in a children's home in Jamaica. The theoretical predictions of a deterministic model incorporating these parameters were approximated to observe horizontal-age prevalence data from a naturally infected population (n=203) of children in a St. Lucian village, and a rough estimate of the basic reproductive rate (Ro=8-10) of T. trichiura obtained. The findings suggest that T. trichiura populations are intrinsically more difficult to control by traditional mass-treatment chemotherapy (eradication requires >91 percent of the population to be treated every 6 months for >5 years) than are populations of Ascaris, but may be more susceptible to selective chemotherapy programmes which aim to treat only the most heavily infected individuals (AU)

Pertussis: herd immunity and vaccination coverage in St Lucia

In a single complete epidemic in St Lucia, an island too small to support constant clinical pertussis, the pertussis case rates in small communities (villages and small towns) with differing levels of vaccination coverage of young children were compared. The association between greater vaccination coverage and greater herd immunity was clear, despite the imperfect protection given to individuals. An analysis in terms of population dynamics is evidence against the theory that endemic subclinical pertussis maintains transmission in a highly vaccinated population. We suggest that with a homogeneous vaccination coverage of 80 percent of 2-year-old children pertussis might be eradicated from the island, and that is a practical experiment. (Summary)

Control implications of the population dynamics of trichuriasis

The present study uses our data from St. Lucia and Jamaica to quantify, for the first time, the population dynamics of paediatric trichuriasis and to examine the implications for the design of control programmes. Trichuris population growth in individual hosts is regulated by density-dependent constraints as indicated by the inverse power law (Z = 0.95) relationship between fecundity and worm burden. The distribution of worms/host is highly aggregated and is well described by a negative binomial model of exponent K = 0.27. The probability that a female worm is mated is a function of this aggregation and has some critical ("breakpoint") minimum mean worm burden for population persistence. In highly aggregated population (K < 0.5) this breakpoint approaches zero and has little practical relevance for control. The Basic Reproductive Rate (Ro) - the mean number of reproductive females produced by a female worm during her lifetime - has a value of 1 for population stability, extinction and < 1 for expansion. The Ro is estimated from equilibrium values of horizontal age prevalence and intensity. Trichuris attains an equilibrium mean intensity (100.6 host-1) and mean prevalence (80 - 90 percent) in 18-month old children, implying that Ro = 4 - 6. These variable values approximate to those reported for Ascaris populations but indicate a greate severity of aggregation and a higher intrinsic transmission rate. Theoretical studies on Ascaris indicate that chemotherapy would have a greater effect on incidence than prevalence, in agreement with empirical evidence for Trichuris. These findings suggest that trichuriasis is more resistant to control than ascariasis, and that chemotherapy would be required on a continual and long term basis and would have greater impact if focussed on heavily infected individuals (AU)

Population regulation in an island community

The biodemographic of a small Bahamian island are explored historically through the analysis of religious documents, censuses, vital statistics records, and computerized anthropological survey data on 84 percent of the current residents. In contrast to the Caribbean area in general, population size of Bimini, Bahamas has stabilized since 1963. While completed fertility (women over 40) is relatively high, various biosocial factors are contributing to population regulation on Bimini including falling natality rates, increasing availability and usage of contraceptives, comparatively late onset of menstruation and delayed marriage, extensive emigration, pronounced childhood mortality, and other aspects of the island's rapidly changing demographic structure. The present evidence suggests that the current trend of population stabilization and regulation is likely to continue for some time in the future (AU)

Population dynamics of the sickle cell trait in the Black Caribs of British Honduras, Central America

The Black Caribs of British Honduras are an essentially biologically identifiable African population transplanted to the New World. In this population a frequency (.241) of the sickle-cell trait (HbA HbA) was observed. It has been demonstrated that the sickle-cell gene HbS is maintained in this population at equilibrium values due to the greater fertility of the heterozygous (HbA HbS) mothers (fertility ratio 1.45). The most likely explanation is that normal homozygous mothers (HbA HbA) have more pregnancy interuptions. The sex ratio of the offsprings of HbA HbA mothers is low, while that of HbA HbS mothers is normal. It is suggested that because the Black Caribs are exposed to falciparum malaria of medium endemicity, the placenta of infected non-immune mothers might be predisposed to some mechanical injury causing intra-uterine death of fetus. The mothers who are heterozygous for the sickle-cell gene seem to be relatively protected from this type of interaction. (Summary)