Graduation Year

2016

Document Type

Thesis

Degree

M.S.P.H.

Degree Name

MS in Public Health (M.S.P.H.)

Degree Granting Department

Global Health

Major Professor

Robert Novak, Ph.D.

Committee Member

Benjamin Jacob, Ph.D.

Committee Member

Mark Paris, M.D.

Keywords

TB, agriculture, season, community, migration, transmission

Abstract

Nearly 20 studies conducted in the last 40 years indicate that tuberculosis (TB) represents a major health concern among migrant farm worker (MFW) populations, but their role in the transmission of TB within the broader community is poorly understood. To this end an ecological study was undertaken which examined 67 Florida counties between years 2009 through 2013. Its aims were as follows: (1) to describe the demographic, geographic, and temporal distribution of the incidence of active TB, (2) to examine the effect of agriculturally relevant seasonal periods on the incidence of active TB, and (3) to quantify the strength and direction of the association between the incidence of active TB and the quantity of MFWs at the county-level, while adjusting for known ecological risk factors. Secondary data was obtained from a total of eight government resources. Statistical analyses began with univariate and bivariate statistics, and this was followed by choropleth maps, Moran’s I, and hot spot analyses during the geographic analysis. Temporal analyses consisted of graphical methods examining TB incidence on annual, quarterly, monthly, and seasonal bases as well as regression modelling with repeated measures. Multivariate analyses were performed with a series of negative binomial regression models, one for each year of the study time period. The results indicated a lack of any geographic relationship between the clustering of high incidence counties and those with larger MFW populations. Incidence rates in counties with larger MFW populations seemed to follow a cyclic pattern in which increases occurred during the spring and early summer, but this seasonal pattern was neither consistent nor prominent throughout the study time frame. Similarly, multivariate analyses yielded no associations between TB incidence and the quantity of MFWs during the 5-year study period, although relationships were detected between TB incidence and other demographic and socioeconomic variables. Altogether there was insufficient evidence to conclude that MFW populations contribute to TB transmission in the broader communities that they occupy. In the absence of standard, reliable data sources reporting on MFW numbers, future inquiries into this matter would benefit from improved estimation strategies of MFW population sizes. Also, modelling may be enhanced by techniques adapted to spatial autocorrelation, and spatial scales finer than the county-level should be examined.

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