Oz Virus Infection in 6 Animal Species, Including Macaques, Bears, and Companion Animals, Japan

Abstract

Oz virus (OZV) was isolated from an Amblyomma tick in Japan and shown to cause lethal viral myocarditis in humans. However, the natural reservoirs and the distribution of OZV remain unknown. We describe epidemiologic studies conducted by using serum samples collected from mammals throughout Japan. The results showed that 27.5% of wild boars, 56.1% of Sika deer, 19.6% of Japanese macaques, and 51.0% of Asian black bears were positive for virus-neutralizing antibodies against OZV. Approximately 2.8% of dogs and 1.0% of cats also were seropositive. OZV RNA was not detected in any of the examined animal serum samples. Most seropositive animals were distributed in central and western Japan. OZV infects a wide range of animal species, including companion animals and nonhuman primates, and is distributed through central and western Japan, suggesting that further countermeasures are required to prevent this tickborne zoonotic infection.

Keywords: Japan; Oz virus; companion animal; tick-borne infections; vector-borne infections; viruses; wild animal; zoonoses.

Figure 1

Regional divisions of Japan. Serum samples were collected from animals in all 8 regions (Hokkaido, Tohoku, Kanto, Chubu, Kinki, Chugoku, Shikoku, and Kyusyu/Okinawa) during 2007–2023. Oz virus was first isolated from an Amblyomma testudinarium tick obtained in the Ehime Prefecture in the Shikoku region in 2017. A fatal human case of Oz virus infection occurred in 2023 in the Ibaraki Prefecture in the Kanto region.

Figure 2

Geographic distribution of Oz virus–neutralizing antibody-positive individuals of 6 animal species, by prefecture, Japan, 2007–2023. A) Wild boar (Sus scrofa leucomystax). B) Sika deer (Cervus nippon). C) Japanese macaques (Macaca fuscata). D) Asian black bear (Ursus thibetanus). E) Dog (Canis lupus familiaris). F) Cat (Felis silvestris catus).

Figure 3

Comparison of the results of virus-neutralization tests (positive vs. negative) and ELISAs against Oz virus in serum samples from 6 tested animal species, Japan, 2007–2023. A) Wild boar (Sus scrofa leucomystax). B) Sika deer (Cervus nippon). C) Japanese macaques (Macaca fuscata). D) Asian black bear (Ursus thibetanus). E) Dog (Canis lupus familiaris). F) Cat (Felis silvestris catus). Red dashed line indicates optimal cutoff value of ELISA, which was determined by a 2-graph receiver-operating characteristic curve. The ELISA cutoff value was not determined in dogs and cats because of the low numbers of seropositive companion animals. Horizontal lines indicate means and error bars SDs. OD, optical density.