Associate ProfessorRyo Nakao

Affiliation: Graduate Faculty of Veterinary Medicine (Collaborative School of Veterinary Medicine Medicine Course)

Specialty: Veterinary Parasitology

Research keywords: arthropods, zoonotic diseases, field, microbiota, commensal microorganisms

Alma mater: Hatsushiba Hashimoto High School (Wakayama Prefecture)

Final academic background: Graduate School of Veterinary Medicine, Hokkaido University

HP address:

*This article was originally published in the 4th issue of "Frontiers of Knowledge" and has been re-edited for the web. Updated on December 7, 2022

What are arthropod-borne diseases?

Pathogens are transmitted from animals to humans by blood-sucking arthropods

Various types of arthropods inhabit the world, some of which feed on humans and animals. You may know that malaria, one of the three major infectious diseases in the world, is transmitted by mosquitoes, but many other infectious diseases are transmitted by blood-sucking arthropods. Many arthropod-borne diseases are zoonotic diseases that affect both humans and animals. Almost every year, new infectious diseases transmitted by arthropods are reported around the world, and it is believed that there are many latent pathogens that we do not yet know about.

What kind of research are you doing?

We collect arthropods from domestic and overseas fields and conduct research to clarify the microbial community (microbiota) of each arthropod. By sorting out which arthropods in which regions pathogens of humans and animals are found, it is possible to disseminate information on which regions are at risk of epidemics. Also, by detecting new microorganisms, we can prepare for emerging infectious diseases that may occur in the future.

Field surveys in Japan and overseas (From left: Republic of Zambia, Republic of the Union of Myanmar, Hokkaido)

What research tools do you use?

To clarify the microbial community, we use the genetic sequence of each microorganism as a clue. Using a high-speed sequencer, a state-of-the-art device capable of deciphering a large amount of gene sequences, we obtain the genetic information of microorganisms at once. The vast amount of information obtained will be collated with base sequence databases collected from around the world using supercomputers and other devices to determine the type of microorganism. In addition, in the laboratory, cultured cells of ticks, mosquitoes, etc. are used to isolate microorganisms. By clarifying the genome (entire gene) information of isolated individual microorganisms, we can scientifically predict what characteristics they have.

Symbiotic microbes hold the key to infectious disease research?

Microscopic image of symbiotic bacteria (top) and test of inoculating it to ticks (bottom)

In the process of investigating the microbial community of arthropods, it was found that there are many non-pathogenic microorganisms that do not cause disease in addition to pathogens that cause diseases in humans and animals. Among them, it has been confirmed that there are microorganisms called symbiotic microorganisms, which are indispensable for the life of the host arthropods. Some commensal microbes are known to produce nutritional substances such as vitamins that arthropods cannot synthesize, but their other roles are largely unknown. In addition, it has been reported that symbiotic microorganisms determine whether arthropods can transmit pathogens, and it has become clear that there is a close relationship between symbiotic microorganisms and pathogens. In other words, in order to understand arthropods and pathogens, it may be necessary to correctly understand the role of symbiotic microorganisms. I believe that symbiotic microorganisms that do not cause disease in humans and animals, which have not received much attention so far, may be important for controlling infectious diseases transmitted by arthropods.