Infectious diseases caused by viruses transmitted by ticks are increasing every year.
In Japan, the number of cases reached a record high last year, and the first case of human-to-human infection was also confirmed.
"Ticks are becoming more common in our daily lives,"
experts warn. What the heck is going on?
Here's what you need to know about the relationship between ticks and diseases before you go for cherry blossom viewing or hiking in spring.
table of contents
Japan's first “human-to-human infection”
Tick-borne infectious disease “SFTS” highest number ever
<Thorough explanation by the five department heads>
What are the symptoms?
What is the mortality rate?
Why are ticks approaching?
What should I be careful about?
“Mountains and ticks”
Open table of contents
table of contents
table of contents
Japan's first “human-to-human infection”
Tick-borne infectious disease “SFTS” highest number ever
<Thorough explanation by the five department heads>
What are the symptoms?
What is the mortality rate?
Why are ticks approaching?
What should I be careful about?
“Mountains and ticks”
Japan's first “human-to-human infection”
19th of this month. The National Institute of Infectious Diseases has announced the first case in Japan of human-to-human transmission of the tick-borne infectious disease SFTS (severe fever thrombocytopenia syndrome).
According to the National Institute of Infectious Diseases, in April 2023, a male doctor in his 20s who examined a patient in his 90s infected with SFTS developed a fever 11 days after the first contact, and was subsequently diagnosed with SFTS.
Genetic testing of the virus showed that it was the same virus as the patient in his 90s, and the infection was diagnosed as human-to-human. Human-to-human transmission of SFTS has been reported in China and South Korea, but this is the first time it has been confirmed in Japan.
Medical workers took infection control measures while the patient in his 90s was hospitalized, but the doctor did not wear gloves during the examination before the patient was diagnosed, and when the patient died and was treated later. Although he was wearing a mask and gloves, he was not wearing goggles. Doctors say his symptoms have already improved.
Ticks approaching life
``I think human-to-human infection is a very rare case, but ticks themselves are becoming a part of our daily lives,'' says a researcher at the
National Institute for Environmental Studies who is familiar with risk countermeasures against invasive species. I am Koichi Goka, Director of the Ecological Risk Assessment and Countermeasures Laboratory.
Director Goka said that at this point, it is not clear as there is insufficient information about the process by which this human-to-human infection occurred, but stated as follows:
Director Goka
: ``I was surprised to hear that it spread from person to person.'' Until now, there have been multiple cases of human-to-human infection reported overseas where the infection was believed to have occurred through contact with the blood or body fluids of patients. However, SFTS is generally caused by a tick bite, so I think it is a special case."
Tick-borne infectious disease “SFTS” highest number ever
While human-to-human transmission is "uncommon," Goka points out that the risk of tick-borne infections is increasing.
The number of patients with SFTS in Japan is increasing every year.
According to the National Institute of Infectious Diseases, there were 48 patients who developed SFTS in 2013, when they began collecting statistics. The number remained almost flat for three years from 2014, but reached 90 in 2017, and exceeded 100 in 2019.
In 2020, when the new coronavirus infection spread, the number decreased to 78 people, but the number has continued to rise since then. In 2023, the number will reach a record high of 133, which is about three times the number since 2013, when statistics began to be collected.
The number of patients reached an all-time high. What kind of disease is it? What's behind it?
We asked Chief Goka for more details.
<Thorough explanation by the five department heads>
(The following is the story of Gokamuro)
What are the symptoms?
Approximately 1 to 2 weeks after being bitten by a tick, a person develops a fever, and in many cases, a person may have a loss of appetite, feel nauseated, or develop symptoms such as diarrhea or abdominal pain.
Other symptoms include headaches and muscle pain, and in severe cases, consciousness disturbance and neurological symptoms may also occur. Additionally, the disease can cause bleeding symptoms such as subcutaneous bleeding and melena.
What is the mortality rate?
So far, mortality rates of around 11% to 27% have been reported.
The possibility of death is particularly high for people over 50 who have low physical strength or immunity, or who have pre-existing conditions.
There is currently no specific treatment for this disease, and it is a highly dangerous infection.
How do you get infected?
Pathogens (viruses, etc.) that cause tick-borne infections are thought to be parasitic in the bodies of wild animals, and they also infect ticks that suck their blood.
Tick-borne diseases are diseases that can be transmitted to humans by being bitten by ticks that carry pathogens. A typical example of this disease is "SFTS (Severe Fever Thrombocytopenia Syndrome)", which I have already mentioned.
Also, ``Japanese Spotted Fever'' and ``Lyme Disease'' are other diseases that have been around for a long time. Both are scary diseases that can lead to death if they become severe.
Is it spreading worldwide?
The SFTS virus was first reported in China, where there was an outbreak in 2009. Analyzing the lineage of the virus, it appears that it originated in southern China around 1700 and has continued to evolve and spread from there.
It is estimated that it first entered Japan in the 1800s, and cases have also been reported from Southeast Asia and other countries in recent years. There is a possibility that the virus will continue to spread through the movement of ticks, infected animals, or humans.
As with the new coronavirus, infectious viruses have the potential to spread anywhere in this era of global economy, and I think we must consider that the spread of infectious diseases is ``all within expectations.''
First of all, what is a tick?
Tick is a highly diverse animal with nearly 50,000 species that have been discovered, and ticks are the most representative of the ticks that feed on the blood of animals, with about 800 species worldwide. More than 50 species are known from Japan.
Their only food source is animal blood, and as they grow, they repeatedly molt their skin from juveniles to nymphs to adults, parasitizing animals and sucking blood.
When they are young, they mainly parasitize small mammals such as rodents, when they become nymphs, they parasitize medium-sized mammals such as rabbits, foxes, and raccoon dogs, and when they grow into adults, they parasitize large mammals such as deer, boars, and bears.
How do ticks move?
Ticks are cold-blooded animals, so they endure the cold and overwinter in places sheltered from the rain and wind, such as behind fallen leaves, and when they are warm enough to move around, they gather behind leaves of trees or grass and wait for animals to pass by.
A tick behind a raccoon's ear
Ticks do not have eyes, but they can smell changes in carbon dioxide concentration using organs attached to their feet. When they think an animal is coming, they head in that direction and use the static electricity on their bodies to latch on to the animal.
Where do ticks come from?
Ticks' main habitat is where prey animals pass through. Ticks are more likely to appear in areas that are known as animal trails, such as grassy areas and forest roads.
There are also research results that show a correlation, such as the higher the frequency of deer appearance, the greater the number of ticks caught.
Recently, I've been seeing things in familiar places such as grassy fields along rice fields, riverbeds, and bamboo thickets.
Why are ticks approaching?
Originally, their habitat was in the mountains, where wild animals such as deer and wild boars live. In the past, wild animals were wary and did not approach areas where humans lived, so ticks did not occur nearby. but…
Nowadays, the line between wild animals and human society is blurring, and wild animals are increasingly appearing in urban areas, causing problems. Last year, the number of bear sightings and damage was at a record high in various areas.
Behind these changes are changes in the social structure due to depopulation and aging, resulting in the abandonment and decline of Satoyama, the zoning area that separates human society from the animal world.
What should I do about it?
In addition to simply exterminating ticks, we need to reconsider the changes in the way humans and animals interact.
I believe that unless we once again ensure zoning and appropriate distance between humans and animals, we will not be able to find a fundamental solution to countering tick-borne infectious diseases.
It is important to proceed with individual measures based on this premise.
What should I be careful about?
Basically, it is your responsibility to protect yourself, and the most important thing is to avoid being bitten by ticks.
First of all, it is best to avoid getting too close to areas where ticks are likely to be found, such as grassy areas. Not only in the mountains, but also in urban areas, you need to be careful about grass and bamboo bushes that are knee-high.
However, I think there will be more opportunities to enjoy outdoor leisure activities in the coming seasons. In such cases, it is necessary to cover your body to avoid exposing too much skin to prevent ticks from landing on your body.
However, when the weather gets hot, covering your entire body increases the risk of heatstroke. In such cases, it is a good idea to use an insect repellent spray, especially one containing 15% or more of the ingredient DEET.
(Up to this point, the story of the Goka room manager)
“Mountains and ticks”
The Ministry of Health, Labor and Welfare also urges people to be careful about ticks.
Ministry of Health, Labor and Welfare awareness poster
The Ministry of Health, Labor and Welfare's website states that ticks are particularly active from spring to autumn, so if you go into grass or bushes, you should wear long sleeves and pants, and wear shoes that completely cover your legs to minimize exposed skin. I am calling on you to do so.
If you get stung, don't force it out!
Also, if you find a tick biting you, do not try to pull it out forcibly, and seek treatment at a medical institution.If you notice a tick bite after being bitten, please pay close attention to any changes in your physical condition for a few weeks. If you notice symptoms such as fever, we recommend that you seek medical attention at a medical institution.