Global Distribution and Clinical Features of Pythiosis in Humans and Animals

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.

Secretome Profiling by Proteogenomic Analysis Shows Species-Specific, Temperature-Dependent, and Putative Virulence Proteins of Pythium insidiosum

“…Ureases of P. insidiosum and Cryptococcus neoformans share a high degree of sequence similarity (71%) and identity (57%) [ 45 ]. P. insidiosum might adopt the pathogenic properties of urease from those pathogens as a part of its ability to infect the gastrointestinal tract, arteries, skin, eye, and multiple organs (in disseminated infection) [ 4 ] ( Figure 5 ). The urease (Ure1) of P. insidiosum has been detected inside (previous report [ 45 ]) and outside (this study) the cell, implying that the enzyme could function both intracellularly and extracellularly.…”

“…Pythium insidiosum infects humans and animals worldwide and causes pythiosis, a devastating disease [ 1 , 2 , 3 , 4 ]. It is a member of the so-called oomycetes, a unique group of filamentous microorganisms that are not fungi but belong to the Phylum Oomycota of the Stramenopiles ( ; accessed on 14 May 2022) [ 1 , 2 ].…”

“…Definitive diagnosis of pythiosis can be made by using various techniques (i.e., microbiological methods, serological tests, immunohistology, molecular detection, and proteomic analysis), many of which are not widely available [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Conventional antimicrobial drugs usually fail in treating pythiosis [ 3 , 4 , 23 , 24 ]. An affected organ (i.e., leg, arm, and eye) is typically removed to prevent disease progression and recurrence.…”

“…An affected organ (i.e., leg, arm, and eye) is typically removed to prevent disease progression and recurrence. Many patients die from aggressive and uncontrollable pythiosis [ 4 , 24 ].…”

Pythium insidiosum Keratitis: Past, Present, and Future

“…The patient was subsequently diagnosed with sickle cell trait [ 3 ]. Since then, 168 ocular pythiosis cases have been reported in the literature until 2021 [ 5 ]. PI keratitis has been sparsely reported due to varied reasons such as lack of knowledge about the microscopic and colony morphology of the organisms among the microbiologists, falsely labeling it as an unidentified fungus, absence of growth in the culture, lack of high clinical suspicion among the clinicians, delayed diagnosis, and its clinical resemblance to fungus [ 6 ].…”