Survey of <i>Francisella tularensis</i> in Wild Animals in Japan in Areas Where Tularemia is Endemic

Abstract

SUMMARY: Samples taken from 428 wild animals and 126 ticks, collected from a tularemia-endemic area in Japan between 2005 and 2013, were analyzed for the presence of Francisella tularensis. F. tularensis was isolated from a Japanese hare carcass whereas the samples from live animals and ticks were negative for F. tularensis by real-time PCR. Our results suggest that F. tularensis is still present in Japan although its prevalence is considerably low even in areas where tularemia is endemic.Francisella tularensis is the etiological agent of the zoonotic disease tularemia. It has a very wide host range including mammals, birds, amphibians, fish, and invertebrates (1), and is able to remain infectious in water and mud for months (2). Tularemia is endemic in many regions of the Northern hemisphere, and in Europe, it has reemerged in several countries including Germany (3), Kosovo (4), and Turkey (5). In these countries, certain rodent species and lagomorphs are of paramount importance for maintaining enzootic foci (6) and a high rodent population is thought to trigger the outbreaks in humans (4). In Japan, tularemia is endemic in Tohoku district, the northeastern area of the largest-island, Honshu, and approximately 1,400 cases of human tularemia have been reported since 1924 (7). F. tularensis has been isolated from human patients, Japanese hares, a Japanese shrew-mole, and ticks (8). Four of the 5 patients diagnosed with tularemia in 2008 acquired the infection from Japanese hares (9). Although several other animal species have also been implicated as the source of infection (7), the epizootic transmission cycle of F. tularensis is yet to be understood. Our previous studies showed that wild animals that tested positive for antibodies to F. tularensis were exclusively found within an area in Japan where tularemia is endemic (10,11). In order to better understand how this zoonotic pathogen is maintained in nature, identification of wild animals harboring infectious bacteria is necessary. In this study, we attempted to determine the prevalence of F. tularensis in wild animals and ticks, through the detection of F. tularensis-specific nucleic acid, in an area of Japan where tularemia is endemic.Samples were collected in Nikaho city (Akita prefecture), Namie town (Fukushima prefecture), and Yokohama town (Aomori prefecture) (Fig. 1). The former 2 are located in the major areas where tularemia has been endemic historically (7), and the latter lies within a 1.5-km radius from the point where an F. tularensis infected Japanese hare was found in May 2008 (12). In Akita, 50 Japanese hares (Lepus brachyurus) were shot by volunteer hunters during the hunting season in 2006, 2008, and 2009 (Table 1). The livers and/or spleens of hares were sampled and subsequently sent to the National Institute of Infectious Diseases (NIID) under refrigeration. A Japanese hare incidentally found dead by a volunteer hunter was also sent to the NIID in accordance with the safe transport guidelines stipulated by the institute. A total of 181 sp...

Detection of Francisella tularensis and analysis of bacterial growth in ticks in Japan

“…The phylogenetic analysis demonstrated that the F. tularensis strains detected in ticks in this study were closely related to strains distributed throughout Eurasia (Wang et al 2011). Although F. tularensis DNA had not been detected in ticks in Japan since 1991 (Fujita et al 2008), surveys of F. tularensis among wild mammals in Japan have been reported (Hotta et al 2012(Hotta et al , 2015Sharma et al 2014). These reports suggest that F. tularensis is still present in Japan.…”

Virulence of Francisella tularensis Subspecies holarctica Biovar japonica and Phenotypic Change during Serial Passages on Artificial Media

“…F. tularensis NVF1 was isolated in our laboratory from a Japanese hare carcass found in Akita prefecture in 2009 [24]. KU-1, isolated in Aomori prefecture in 2008 [25], was kindly provided by Hisaaki Sato (Kitasato University, Aomori, Japan).…”

“…In 2008 and 2009, F. tularensis subsp. holarctica biovar japonica, NVF1 [24] and KU-1 [25], were isolated from carcasses of Japanese hares and stored in a deep freezer. Thereafter, F. tularensis has not been isolated in Japan.…”