Combining forces--the use of Landsat TM satellite imagery, soil parameter information, and multiplex PCR to detect Coccidioides immitis growth sites in Kern County, California.

Antje Lauer,Kirt W Emery,Laura Rosío Castañón Olivares,Natasha Shroff,Luis Jaime Medina,Kayla Casimiro,Joe Daryl Hugo Baal,Jorge Talamantes,Vishnu Chaturvedi

doi:10.1371/journal.pone.0111921

Abstract

Coccidioidomycosis is a fungal disease acquired through the inhalation of spores of Coccidioides spp., which afflicts primarily humans and other mammals. It is endemic to areas in the southwestern United States, including the San Joaquin Valley portion of Kern County, California, our region of interest (ROI). Recently, incidence of coccidioidomycosis, also known as valley fever, has increased significantly, and several factors including climate change have been suggested as possible drivers for this observation. Up to date details about the ecological niche of C. immitis have escaped full characterization. In our project, we chose a three-step approach to investigate this niche: 1) We examined Landsat-5-Thematic-Mapper multispectral images of our ROI by using training pixels at a 750 m×750 m section of Sharktooth Hill, a site confirmed to be a C. immitis growth site, to implement a Maximum Likelihood Classification scheme to map out the locations that could be suitable to support the growth of the pathogen; 2) We used the websoilsurvey database of the US Department of Agriculture to obtain soil parameter data; and 3) We investigated soil samples from 23 sites around Bakersfield, California using a multiplex Polymerase Chain Reaction (PCR) based method to detect the pathogen. Our results indicated that a combination of satellite imagery, soil type information, and multiplex PCR are powerful tools to predict and identify growth sites of C. immitis. This approach can be used as a basis for systematic sampling and investigation of soils to detect Coccidioides spp.

Highlights

Valley fever research has predominantly focused on the medical and epidemiological aspects of Coccidioides immitis and Coccidioides posadasii, the fungi that cause coccidioidomycosis ([1,2], and references therein)
We investigated if a combination of remote sensing and soil parameter information can predict locations which might be suitable to support the growth of C. immitis, followed by a molecular biological approach to detect the fungus in these soils with a culture independent polymerase chain reaction (PCR) based method [32,47]
Sites which were similar in vegetation to site STH, a confirmed growth site of C. immitis, were indicated in yellow, whereas sites that are characterized by different vegetation types appeared in various shades of green and red

Summary

Introduction

Valley fever research has predominantly focused on the medical and epidemiological aspects of Coccidioides immitis and Coccidioides posadasii, the fungi that cause coccidioidomycosis ([1,2], and references therein). Coccidioides spp. are endemic in the southern part of the San Joaquin Valley in California, southern California, the southern part of Arizona, New Mexico and Texas, most of northern Mexico, and some areas in Guatemala, Honduras, Venezuela, northeastern Brazil, Argentina, and Paraguay [5,6]. It is evident that C. posadasii is able to flourish in desert regions of the Americas (besides California), in contrast to its close relative C. immitis which seems to be restricted to areas in California.

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Conclusion