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Mites
Published in Jerome Goddard, Public Health Entomology, 2022
Larval stage mites in the family Trombiculidae, sometimes called chiggers (Figure 18.1a), harvest mites, or red bugs, are medically important pests around the world, primarily because they cause dermatitis and may transmit the agent of scrub typhus. Adult chiggers are oval shaped (approximately 1 mm long) with a bright red, velvety appearance, but it is only the larval stage that attacks vertebrate hosts. Chigger larvae are very tiny (0.2 mm long), round mites with numerous setae (Figure 18.2). The mites may be red, yellow, or orange in color and have a single dorsal plate (scutum) bearing two sensillae and four to six setae. Identification to the species level is extremely difficult and expert technical help is required (see Chapter 8).
Hemorrhagic Fever with Renal Syndrome: A Historical Perspective and Review of Recent Advances
Published in James H. S. Gear, CRC Handbook of Viral and Rickettsial Hemorrhagic Fevers, 2019
If ectoparasites are involved in transmission, larvae of trombiculid mites (chiggers) may be the best candidates.40,175 A survey of ectoparasites, conducted in 1951 to 1952 in rodents trapped in three endemic areas (Chip’o-ri, Yunchun, and Kumhwa) in Korea, indicated that the chigger index (mean number of trombiculid mites per A. agrarius) correlated with the number of cases of Korean hemorrhagic fever and the biphasic pattern of disease occurrence.175 As in scrub typhus, a “place” disease which is transmitted by infectious feces of the human louse, Traub and Wisseman187 speculate that feces from hantavirus-infected chiggers may be aerosolized, thus serving as the source for both enzootic and human infections. The recent isolation of a Hantaan-like virus, designated strain 82-Tsl, from chiggers in the People’s Republic of China supports this hypothesis and indicates that further studies are needed.
Parasitoses
Published in Giuseppe Micali, Francesco Lacarrubba, Dermatoscopy in Clinical Practice, 2018
Maria Rita Nasca, Giuseppe Micali
Videodermatoscopy is a useful tool for the diagnosis of ectoparasitic disorders.5–6 In trombiculiasis it can easily reveal at ×30 magnification the characteristic reddish mite strongly attached to the patient’s skin that may otherwise go overlooked (Figure 8.2a). Moreover, at ×150 magnification, details useful to recognize trombiculid mites in their larval stage and make a correct definitive diagnosis are easily appreciable (Figure 8.2b). They appear as 0.2–0.4 mm roundish and elongated orange mites with three pairs of long legs, two paired eyes, and a feeding apparatus with visible hooked chelicerae and segmented palps.4 Such traits, common to larvae of several trombiculid mites, may be inadequate for a stringent taxonomic assignment but yet enable unequivocal identification of chigger mites in the medical setting.
Detection of co-infection with Orientia tsutsugamushand and hemorrhagic fever with renal syndrome by next-generation sequencing
Published in International Journal of Neuroscience, 2023
Qianhui Xu, Wenyi Zhang, Qian Wang, Xuejun Fu, Jing Han, Ying Huang
Orientia tsutsugamushi (O. tsutsugamushi) is an obligate intracellular bacterium belonging to the subspecies of Proteobacteria, family Rickettsiaceae, and is responsible for scrub typhus. O. tsutsugamushi is transmitted to humans through the bites of larval trombiculid mites. The bacterium is still a major cause of undifferentiated fever in Asia. The prognosis varies among patients, ranging from asymptomatic infection to death. Co-infection with O. tsutsugamushi and other pathogens such as dengue virus [1] Leptospira [1,2] has been reported in Southeast Asia. To our knowledge, the present patient, who is an original resident of Zijin County, Heyuan, Guangdong, is the first case of co-infection with O. tsutsugamushi and Hantaan virus. Serological testing and next-generation sequencing confirmed co-infection in the patient. Lack of knowledge of co-infection may jeopardize the health of affected patients. Our study serves as a reminder of potential co-infection and provides clues for its detection.
Acute transverse myelitis following scrub typhus: A case report and review of the literature
Published in The Journal of Spinal Cord Medicine, 2020
Hyun-Seung Ryu, Bong Ju Moon, Jae-Young Park, Sang-Deok Kim, Seung-Kwon Seo, Jung-Kil Lee
Scrub typhus is an acute febrile illness and mite-borne bacterial infection caused by Orientia tsutsugamushi, an obligate gram-negative intracellular bacterium.1 The bacterium is transmitted by the bite of the trombiculid mite (chigger), which leaves the tell-tale pathognomonic eschar.1 Scrub typhus is known to occur throughout Asia, but recent evidence suggests that its range may be larger, with case reports in Asia-Pacific, including Korea.2 Patients with scrub typhus usually develop various complications, such as myocarditis, arrhythmia, and interstitial pneumonia.2 Neurological manifestations in scrub typhus are infrequent, but recently central nervous system (CNS) manifestations in the form of meningitis or meningoencephalitis have been reported.3,4 However, to our knowledge, scrub typhus invasion of the spinal cord is very rare.5 Hence, we present a case of acute transverse myelitis following scrub typhus with a review of the literature.
Scrub typhus and antibiotic-resistant Orientia tsutsugamushi
Published in Expert Review of Anti-infective Therapy, 2021
Chin-Te Lu, Lih-Shinn Wang, Po-Ren Hsueh
Scrub typhus is one of the most underdiagnosed and under-reported febrile illnesses requiring hospitalization, mainly in Asia, in an area referred to as the ‘Tsutsugamushi Triangle.’ Scrub typhus exhibits pronounced seasonality, with high transmission peaks before and after the rainy season in regions of Southeast Asia, and a regular year-round transmission common in other tropical and subtropical regions. Seasonal changes in the prevalence of scrub typhus have been observed in China, Taiwan, South Korea, and Japan. Scrub typhus in humans is caused by the bite of larval trombiculid mites. Adults pass O. tsutsugamushi to their offspring through transovarial transmission. Larva mites are the only pasasite stage, whereas all other active stages are free-living. Endothelial infections involve several organs, including the skin, heart, lungs, kidneys, pancreas, and brain, with additional infection of macrophages in the liver and spleen. The clinical features include sudden-onset fever with chills, headache, backache, myalgia, profuse sweating, vomiting, and enlarged lymph nodes. An eschar develops at the site of the chigger bite, generally where skin surfaces meet, such as in the axilla, groin, inguinal areas and other body parts, including the legs. Laboratory-based methods for the diagnosis of scrub typhus include serological assays, such as the Weil–Felix test, IFA, and ELISA; isolation and culturing of bacteria in cells; and PCR. Various antibiotics, including chloramphenicol, tetracycline, doxycycline, macrolides, quinolones, and rifampicin, have been used to treat scrub typhus. However, the existence and importance of antibiotic-resistant scrub typhus remain unclear.