A habitat-based model for the spread of hantavirus between reservoir and spillover species.

New habitat-based models for spread of hantavirus are developed which account for interspecies interaction. Existing habitat-based models do not consider interspecies pathogen transmission, a primary route for emergence of new infectious diseases and reservoirs in wildlife and man. The modeling of interspecies transmission has the potential to provide more accurate predictions of disease persistence and emergence dynamics. The new models are motivated by our recent work on hantavirus in rodent communities in Paraguay. Our Paraguayan data illustrate the spatial and temporal overlaps among rodent species, one of which is the reservoir species for Jabora virus and others which are spillover species. Disease transmission occurs when their habitats overlap. Two mathematical models, a system of ordinary differential equations (ODE) and a continuous-time Markov chain (CTMC) model, are developed for spread of hantavirus between a reservoir and a spillover species. Analysis of a special case of the ODE model provides an explicit expression for the basic reproduction number, R(0), such that if R(0)<1, then the pathogen does not persist in either population but if R(0)>1, pathogen outbreaks or persistence may occur. Numerical simulations of the CTMC model display sporadic disease incidence, a new behavior of our habitat-based model, not present in other models, but which is a prominent feature of the seroprevalence data from Paraguay. Environmental changes that result in greater habitat overlap result in more encounters among various species that may lead to pathogen outbreaks and pathogen establishment in a new host.

Family resemblance for anthropometric and blood pressure measurements in Black Caribs and Creoles from St. Vincent Island.

This paper examines family resemblance for five anthropometric measurements (height, weight, triceps skinfold, upper arm circumference relaxed [UACR] and flexed [UACF] and for systolic and diastolic blood pressure in a group of adult Caribbean islanders of primarily African ancestry. Six hypotheses about family resemblance are tested by using path analysis and likelihood ratios. Significant intergenerational transmission is found only for height and UACR. For weight, UACF, and diastolic blood pressure, non-transmissible sibling resemblance is the primary component of family resemblance, although significant marital resemblance exists for diastolic blood pressure. Triceps skinfold and systolic blood pressure show no evidence of any family resemblance. Although results for highly heritable traits such as height are comparable to reports from other populations, measurements with a large contribution from common family environment or residual environmental effects, such as triceps skinfold or blood pressure, have much lower family resemblance in this population than in other populations. We hypothesize that this difference is due to the fact that adult children and their parents do not share a common household in this culture and to the presence of major nonfamilial environmental factors contributing to obesity and hypertension in this population.

Association between stress and blood pressure variation in a Caribbean population.

Based on the work of Selye (The Stress of Life, New York: McGraw-Hill, 1976) it is hypothesized that stress can produce physiological abnormalities, i.e., elevated blood pressure, and that social variables can be used as indicators or risk factors for disease. It is theorized that deviations from acceptable social patterns or traditional life-styles can produce stressful conditions that are associated with disease and that these situations can be demonstrated by examination of certain social characteristics. This association is examined among the Black Caribs of St. Vincent, West Indies. The social variables included in this analysis are marital status (single, married, widowed, or separated), frequency of church attendance (frequently, sometimes, seldom, or never), years of education, and number of children (for women only). The findings show that single individuals have higher pressures than married subjects and that males who never attend church have higher pressures than men who frequently attend church; a relationship was not demonstrated for females. Among males, as the years of education increased, blood pressure also increased, but for females, increased education was associated with lower pressures. Family size was not associated with systolic or diastolic pressure. The analysis of these selected social variables suggests that these variables influence male systolic and diastolic pressures, but only female diastolic pressure.

Relationship between African admixture and blood pressure variation in the Caribbean.

The genetic contribution to blood pressure variance is examined by studying a selected group of genes. Of 368 individuals, 48.1% received one-half or more of their genes from an African ancestor and of this group 18.1 and 17.0% exhibit systolic and diastolic hypertension, respectively. A chi-square test was used to examine the dependence of blood pressure on percentage African ancestry. The chi-square values were not significant for systolic or diastolic pressures. It is likely that other factors are strongly related to African admixture and these factors are the true modifiers of blood pressure.