Japanese river typhus

Japanese river typhoid is a zoonosis (a disease transmitted from animals to humans) caused by Orientia tsutsugamushi, an aerobic, Gram-negative, intracellular obligate bacterium (able to reproduce only within a host cell), belonging to the family Rickettsiaceae, genus Orientia, although it has been considered part of the genus Rickettsia, to which the typhoid bacterium also belongs, because of the many similarities. With a high rate of variability in membrane proteins, it has many different strains, the main ones being Karp, Gilliam, Kato, Shimokoshi, Kuroki, and Kawasaki. Once penetrated into the host organism, O. tsutsugamushi affects myelocytes in the vicinity of the inoculation site and subsequently the endothelial cells of the blood vessel. Upon coming into contact with a target cell, it stimulates the endocytosis mechanism of the cell, which engulfs it in a vesicle formed by a fragment of its cell membrane and absorbs it. The bacterium escapes from the vesicle before it is degraded by lysosomes and moves to the vicinity of the nucleus, where it begins to reproduce. When reproduction is finished, it exits the cell, forming a second vesicle in the membrane.

Japanese river typhoid is a zoonosis (a disease transmitted from animals to humans) caused by Orientia tsutsugamushi, an aerobic, Gram-negative, intracellular obligate bacterium (able to reproduce only within a host cell), belonging to the family Rickettsiaceae, genus Orientia, although it has been considered part of the genus Rickettsia, to which the typhoid bacterium also belongs, because of the many similarities. With a high rate of variability in membrane proteins, it has many different strains, the main ones being Karp, Gilliam, Kato, Shimokoshi, Kuroki, and Kawasaki. Once penetrated into the host organism, O. tsutsugamushi affects myelocytes in the vicinity of the inoculation site and subsequently the endothelial cells of the blood vessel. Upon coming into contact with a target cell, it stimulates the endocytosis mechanism of the cell, which engulfs it in a vesicle formed by a fragment of its cell membrane and absorbs it. The bacterium escapes from the vesicle before it is degraded by lysosomes and moves to the vicinity of the nucleus, where it begins to reproduce. When reproduction is finished, it exits the cell, forming a second vesicle in the membrane.

The disease is prevalent mainly in the Asia-Pacific region, between eastern Russia and Korea in the north, northern Australia in the south, and Afghanistan in the west, including several western Pacific islands such as Japan, Taiwan, the Philippines, Papua New Guinea, Indonesia, Sri Lanka, and the Indian subcontinent, although in recent years it has also been detected in Africa, Europe, and South America.

In Asia it represents a major disease in rural regions, with seroprevalence surveys finding evidence of infection in 50 percent of the population. There are an estimated more than one million cases in Asia-Pacific each year and more than one billion people at risk of infection worldwide. It most frequently affects individuals between the ages of 60 and 69, mainly farmers, although cases are also increasing sharply in urban settings.

The incubation period is 6 to 21 days after the mite bite, after which symptoms suddenly appear. The most common are fever, chills, muscle aches, headache and swelling of the lymph nodes, which may be accompanied by coughing during the first week and rash 5 to 8 days after the onset of fever. Mental symptoms may also occur, ranging from states of confusion to coma. In severe cases, organ failure and hemorrhage develop, which can lead to death. The puncture site may have eschar, a blackish scab-like region, which may facilitate diagnosis of the disease.l nervous system.

In regions where the disease is common, the presence of eschar may be considered sufficient, but it is not always present and the symptoms are common to those of many other diseases, so additional tests to medical evaluation may be used to confirm the diagnosis.
The most useful tests are immunofluorescence tests performed on a tissue sample taken from the eruption, ELISA, and DNA analysis using the polymerase chain reaction (PCR) technique. Serological tests performed on blood samples, a cheaper solution but one that requires two tests separated by a period of 1-3 weeks to check for an increase in the number of antibodies, a sign of an ongoing infection, can also be used. For this reason, they are rarely useful in identifying the disease at the onset of symptoms, but may give confirmation later.

Treatment is based on orally administered doxycycline antibiotic therapy until no fever for 48 hours, with a minimum period of 7 days.

No vaccines are available, so you must rely on careful behavioral prophylaxis to reduce the likelihood of being stung by mites. In regions at risk, it is best to avoid areas where brush and vegetation are particularly dense, where you are more likely to encounter larvae. It is also important to use repellents such as DEET (diethyltoluamide) and treat clothing and equipment with 0.5 percent permethrin, carefully following the instructions specified on the products.