Emergence of infectious malignant thrombocytopenia in Japanese macaques (Macaca fuscata) by SRV-4 after transmission to a novel host
Munehiro Okamoto, Takayuki Miyazawa, Shigeru Morikawa, Fumiko Ono, Shota Nakamura, Eiji Sato, Tomoyuki Yoshida, Rokusuke Yoshikawa, Kouji Sakai, Tetsuya Mizutani, Noriyo Nagata, Jun-ichiro Takano, Sachi Okabayashi, Masataka Hamano, Koji Fujimoto, Takaaki Nakaya, Tetsuya Iida, Toshihiro Horii, Takako Miyabe-Nishiwaki, Akino Watanabe, Akihisa Kaneko, Akatsuki Saito, Atsushi Matsui, Toshiyuki Hayakawa, Juri Suzuki, Hirofumi Akari, Tetsuro Matsuzawa, Hirohisa Hirai
We discovered a lethal hemorrhagic syndrome arising from severe thrombocytopenia in Japanese macaques kept at the Primate Research Institute, Kyoto University. Extensive investigation identified that simian retrovirus type 4 (SRV-4) was the causative agent of the disease. SRV-4 had previously been isolated only from cynomolgus macaques in which it is usually asymptomatic. We consider that the SRV-4 crossed the so-called species barrier between cynomolgus and Japanese macaques, leading to extremely severe acute symptoms in the latter. Infectious agents that cross the species barrier occasionally amplify in virulence, which is not observed in the original hosts. In such cases, the new hosts are usually distantly related to the original hosts. However, Japanese macaques are closely related to cynomolgus macaques, and can even hybridize when given the opportunity. This lethal outbreak of a novel pathogen in Japanese macaques highlights the need to modify our expectations about virulence with regards crossing species barriers.