Global Distribution and Clinical Features of Pythiosis in Humans and Animals.

Hanna Yolanda,Theerapong Krajaejun

doi:10.3390/jof8020182

Abstract

Pythiosis is a difficult-to-treat infectious disease caused by Pythium insidiosum. The condition is unfamiliar among healthcare workers. Manifestation of pythiosis is similar to other fungal infections, leading to misdiagnosis and delayed treatment. The geographical extent of pythiosis at a global scale is unclear. This study aimed to analyze the clinical information recorded in the scientific literature to comprehensively project epidemiological characteristics, clinical features, and future trends of pythiosis. From 1980 to 2021, 4203 cases of pythiosis in humans (n = 771; 18.3%) and animals (primarily horse, dog, and cow; n = 3432; 81.7%), with an average of 103 cases/year, were recruited. Pythiosis case reports significantly increased in the last decade. Pythiosis spanned 23 tropical, subtropical, and temperate countries worldwide. Some patients acquired pythiosis from a trip to an endemic country. Strikingly, 94.3% of human cases were in India and Thailand, while 79.2% of affected animals were in the U.S.A. and Brazil. Clinical features of pythiosis varied. Vascular and ocular pythiosis were only observed in humans, whereas cutaneous/subcutaneous and gastrointestinal infections were predominant in animals. Mortality depended on host species and clinical forms: for example, none in patients with ocular pythiosis, 0.7% in cows with a cutaneous lesion, 26.8% in humans with vascular disease, 86.4% in dogs with gastrointestinal pathology, and 100% in several animals with disseminated infection. In summary, this study reports up-to-date epidemiological and clinical features of pythiosis in humans and animals. It increases awareness of this life-threatening disease, as the illness or outbreak can exist in any country, not limited to the endemic areas.

Highlights

Pythiosis is an under-diagnosed and difficult-to-treat infectious disease [1]
This study comprehensively reports up-to-date epidemiological characteristics, geographic distribution, clinical features, overall mortalities, and future trends of pythiosis
We searched for more pythiosis cases from available local journals/databases

Summary

Introduction

Pythiosis is an under-diagnosed and difficult-to-treat infectious disease [1]. High morbidity and mortality of pythiosis are critical healthcare problems. The disease was known as phycomycosis [2,3,4,5], bursattee [6], espundia [7], horse leeches [2,8], granular dermatitis [9], summer sore [9], and swamp cancer [10,11]. The etiologic agent is the filamentous eukaryotic microorganism called Pythium insidiosum [12], which taxonomically belongs to the Stramenopiles-Alveolata-Rhizaria supergroup [13]. Microscopic characteristics of P. insidiosum include broad hyphae (4–10 μm in diameter), perpendicular branching, coenocyte (in young hyphae), sparse septation (in an aged organism), and rounded hyphal tips [12]. The organism produces biflagellate zoospores (asexual reproductive stage) in a suitable aquatic environment [9,12,14] and requires a water plant for colonization as a part of its life cycle [15]

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