The Potential Distribution of Pythium insidiosum in the Chincoteague National Wildlife Refuge, Virginia.

Manuel Jara,Gustavo Machado,Kevin Holcomb,Erica M Goss,Xuechun Wang

doi:10.3389/fvets.2021.640339

Abstract

Pythium insidiosum is a widespread pathogen that causes pythiosis in mammals. Recent increase in cases reported in North America indicates a need to better understand the distribution and persistence of the pathogen in the environment. In this study, we reconstructed the distribution of P. insidiosum in the Chincoteague National Wildlife Refuge, located on Assateague Island, Virginia, and based on 136 environmental water samples collected between June and September of 2019. The Refuge hosts two grazing areas for horses, also known as the Chincoteague Ponies. In the past 3 years, 12 horses have succumbed to infection by P. insidiosum. Using an ecological niche model framework, we estimated and mapped suitable areas for P. insidiosum throughout the Refuge. We found P. insidiosum throughout much of the study area. Our results showed significant monthly variation in the predicted suitability, where the most influential environmental predictors were land-surface water and temperature. We found that June, July, and August were the months with the highest suitability for P. insidiosum across the Refuge, while December through March were less favorable months. Likewise, significant differences in suitability were observed between the two grazing areas. The suitability map provided here could also be used to make management decisions, such as monitoring horses for lesions during high risk months.

Highlights

Pythium insidiosum is the only etiologic agent of pythiosis that affects mainly mammals in tropical and subtropical countries [1, 2]
The modeling framework used in this study included, (i) data collection, considering the definition of sampling sites for water sample collection, isolation, and identification of P. insidiosum (Figure 1A), (ii) extraction of the most suitable environmental variables used in the ecological niche model (ENM) (Figure 1B), (iii) Ecological Niche Model (ENM) model calibration and evaluation (Figure 1C), followed by the (iv) comparison in the suitable areas predicted by the annual and monthly ENMs in the northern and southern grazing paddocks (Figure 1D)
This study reconstructed the potential distribution of P. insidiosum in the Chincoteague National Wildlife Refuge, Assateague Island Unit located in the state of Virginia, United States

Summary

Introduction

Pythium insidiosum is the only etiologic agent of pythiosis that affects mainly mammals in tropical and subtropical countries [1, 2]. P. insidiosum is an oomycete, a eukaryotic lineage in the stramenopiles, and its closest relatives are plant pathogens [3]. Pythiosis is characterized by chronic lesions on the cutaneous and subcutaneous, intestinal, and bone tissues, as well as invasion of blood vessels in infected animals and rarely humans [4, 5], which lead to death or render the affected individual lame if left untreated [2, 4]. Pythiosis infection is acquired by animals and plants through the direct contact of wounds with water that contains motile P. insidiosum spores (zoospores) [6,7,8,9,10]. Previous studies of other oomycetes have demonstrated that zoospores may be

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