Role of Rhizomys pruinosus as a natural animal host of Penicillium marneffei in Guangdong, China

Abstract

Penicillium marneffei, a dimorphic fungus that can cause penicilliosis marneffei, is endemic in Southeast Asia. The only known hosts of P. marneffei are humans and bamboo rats. The aim of our study was to explore the distribution of P. marneffei in bamboo rats, their associated environment and non-rat-associated environments. Totally, 270 samples were collected in Guangdong province of China in 2012; the prevalence of P. marneffei was much higher in samples collected from surrounding areas of burrows (8.2%) than in the samples obtained from non-rat-associated sites (2%) or artificial farms of bamboo rats (0%). There was no difference in P. marneffei isolated rate from different areas of Guangdong province. The infection is prevalent in all rats, and this fungus could be frequently seen in the rats' lungs. This study confirms that bamboo rat is the ecological niche of P. marneffei and hypothesizes that bamboo rats become infected by inhaling aerosolized conidia originating from environmental sources, rather than by the fecal-oral route or transplacental crossing. According to the result of no detection of P. marneffei in the artificial farm, the activity of bamboo rats might be more relevant to the distribution and dissemination of P. marneffei in natural environment.

Fig 1

The bamboo rat (R. pruinosus) we captured and surrounding environmental samples. (A) Rat's cave and stool of the rat; (B) bamboo root in the burrow; (C) the soil and debris of food; (D) petiole; (E) bamboo leaves; (F) bamboo rat.

Fig 2

The isolation of P. marneffei recovered from different samples. Black arrows point to the suspected colonies. (A-C) Growth of P. marneffei recovered from soil, bamboo root and stool of bamboo rats at 25°C. (D-K) The growth of P. marneffei recovered from different organs of bamboo rats at 25°C and 37°C.

Fig 3

The organs of bamboo rat we captured. (A) Lung; (B) liver; (C) spleen; (D) intestine; (E) uterus; (F) embryo.

Fig 4

Map of Guangdong Province of China, showing population of penicilliosis marneffei patients and the locations of Chaozhou, Qingyuan, Zhaoqing, Meizhou and Shaoguan city where samples were collected (red circle represents districts for collecting environmental samples, yellow circle represents district of artificial farm of bamboo rats).