The Distribution and Host-Association of the Vector Chigger Species Leptotrombidium imphalum in Southwest China.

Leptotrombidium imphalum is a species of chigger mites, and it can serve as a transmitting vector of scrub typhus. Southwest China is an important focus of scrub typhus. Based on the field investigation in southwest China from 2001 to 2022, this article presents the first report on the distribution and infestation of L. imphalum on rodents and other sympatric small mammals in the region. A total of 2161 L. imphalum were identified from 218 small mammal hosts in 21 of 114 survey sites. The 17 host species of L. imphalum crossed 13 genera and 5 families in 3 orders (Rodentia, Eulipotyphla, and Scandentia), indicating the low host specificity of the mite. The Asian house rat (Rattus tanezumi) was the dominant host species in the 21 sites where L. imphalum were collected, and 49.38% of mites were found on R. tanezumi. Different small mammals had different susceptibility to the infestation of L. imphalum. The prevalence (PM = 27.66%), infestation mean abundance (MA = 6 mites/per examined host), and mean intensity (MI = 21.69 mites/per infested host) for L. imphalum on the shrew gymnure (Neotetracus sinensis) were much higher than those on other host species (p < 0.05), indicating N. sinensis had a high susceptibility to the infestation of L. imphalum. The infestation indices for L. imphalum on small mammal hosts varied along different altitude and latitude gradients (p < 0.05), indicating the environmental heterogeneity of the mite infestation. Leptotrombidium imphalum exhibited an aggregated distribution among different individuals of its hosts. Besides the low host specificity of L. imphalum, the prevalence of the mite was positively correlated with the occurrence of scrub typhus, indicating the potential risk of the mite.

Discovery of a novel spotted fever group Rickettsia, "Candidatus Rickettsia kedanie," in unfed larval chigger mites, Leptotrombidium scutellare.

Spotted fever group (SFG) rickettsia, the causative agent of SFG rickettsiosis, is predominantly carried by ticks, whereas Orientia tsutusgamushi, the causative agent of scrub typhus, is primarily transmitted by chigger mites in Japan. In this study, we attempted to isolate intracellular eubacteria from Leptotrombidium scutellare, a major vector of O. tsutsugamushi; moreover, we isolated an SFG rickettsia using a mosquito-derived cell line. Draft genome sequences of this unique isolate, by applying criteria for species delimitation, classified this isolate as a novel strain, proposed as "Rickettsia kedanie." Further genetic analysis identified conserved virulence factors, and the isolate successfully propagated in mammalian cells, suggesting its ability to cause diseases in humans. The presence of SFG rickettsia in unfed larvae implies potential dual-pathogen carriage and reflects a symbiotic relationship similar to that between the mites and O. tsutsugamushi, indicating possibility of its transovarial transmission from female adults. Furthermore, conserved genomic similarity of the novel isolate to known SFG rickettsia suggests potential multiple hosts, including chiggers and ticks. In the natural environment, ticks, chigger mites, and wild animals may carry new isolates, complicating the infection cycle and increasing the transmission risks to humans. This discovery challenges the conventional association of SFG rickettsia with ticks, emphasizing its implications for research and disease control. However, this study was confined to a particular species of chigger mites and geographic area, underscoring the necessity for additional studies to comprehend the ecological dynamics, host interactions, and health implications linked to this newly identified SFG rickettsia.

Parasite infestation patterns differ between ticks and chigger mites on two rodent host species in Taiwan.

Parasites are typically concentrated on a few host individuals, and identifying the mechanisms underlying aggregated distribution can facilitate a more targeted control of parasites. We investigated the infestation patterns of hard ticks and chigger mites on two rodent species, the striped field mouse, Apodemus agrarius, and the lesser ricefield rat, Rattus losea, in Taiwan. We also explored abiotic and biotic factors that were important in explaining variation in the abundance of ticks and chiggers on rodent hosts. Ticks were more aggregated than chiggers on both rodent species. Factors important for the variation in parasitic loads, especially biotic factors, largely differed between ticks and chiggers. Variation partitioning analyses revealed that a larger proportion of variation in chiggers than in ticks can be explained, especially by abiotic factors. If, as proposed, the higher number of parasites in males is due to a larger range area or immunity being suppressed by testosterone, when A. agrarius males host more ticks, they are expected to also host more chiggers, given that chiggers adopt a similar host finding approach to that of ticks. Instead, the similar abundance of chiggers in male and female A. agrarius implies that a large home range or suppressed immunity does not predispose males to inevitably host more parasites. More variations were explained by abiotic than biotic factors, suggesting that controlling practices are more likely to be successful by focusing on factors related to the environment instead of host traits. Our study indicated that the extent of parasitism is rarely determined by a sole factor, but is an outcome of complex interactions among animal physiology, animal behavior, characteristics of parasites, and the environments.

Three cases of scrub typhus with hemorrhage: a case report and literature review.

Scrub typhus (ST) is an acute focal infectious disease that is caused by Orientia tsutsugamushi. The Asia-Pacific region is an area of relatively high incidence. There is a high incidence in China, principally owing to the disease being endemic in the south of the country. The main source of ST infection is rats, which act as reservoirs of infection after being bitten by the chigger mite, and the human population is generally susceptible to the disease. ST can be controlled and treated successfully if antibiotics are administered in a timely manner. However, because it does not have a specific clinical manifestation, it is difficult to distinguish ST from other febrile diseases in clinical practice. Therefore, rapid diagnostic methods are still needed to help clinicians make a timely diagnosis. Here, we share three cases of patients with ST who experienced hemorrhage, but did not have typical skin lesions, such as eschar and ulcer, early in the course of their disease, and review the relevant literature regarding ST. We conclude that clinicians should pay attention to the risk of hemorrhage associated with this disease, and emphasize the importance of making an early diagnosis.

Disease vector occurrence and ecological characteristics of chiggers on the chestnut white-bellied rat Niviventer fulvescens in Southwest China between 2001 and 2019.

Chigger mites are the vector of scrub typhus. This study estimates the infestation status and ecological characteristics of chiggers on the chestnut white-bellied rat Niviventer fulvescens in Southwest China between 2001 and 2019. Chiggers were identified under the microscope, and infestation indices were calculated. The Preston's log-normal model was used to fit the curve of species abundance distribution. A total of 6,557 chiggers were collected in 136 of 342 N. fulvescens rats, showing high overall infestation indices (prevalence=39.8%, mean abundance=19.2, mean intensity=48.2) and high species diversity (S=100, H'=3.0). Leptotrombidium cangjiangense, Neotrombicula japonica, and Ascoschoengastia sifanga were the three dominant chigger species (constituent ratio=42.9%; 2,736/6,384) and exhibited an aggregated distribution among different rat individuals. We identified 100 chigger species, with 3 of them (Leptotrombidium scutellare, Leptotrombidium wenense, and Leptotrombidium deliense) as the main vectors of scrub typhus in China and nine species as potential vectors of this disease. Disease vector occurrence on N. fulvescens may increase the risk of spreading scrub typhus from rats to humans. Chigger infestation on N. fulvescens varied significantly in different environments. The species abundance distribution showed a log-normal distribution pattern. The estimated number of chigger species on N. fulvescens was 126 species.

Infestation of Oriental House Rat (Rattus tanezumi) with Chigger Mites Varies along Environmental Gradients across Five Provincial Regions of Southwest China.

Chigger mites are the exclusive vector of scrub typhus. Based on field investigations of 91 survey sites in 5 provincial regions of Southwest China, this paper reported variations of chigger infestation on the oriental house rat (Rattus tanezumi) along various environmental gradients. A total of 149 chigger species were identified from 2919 R. tanezumi in the 5 provincial regions, and Leptotrombidium deliense (a major vector of scrub typhus in China) was the first dominant chigger species, followed by Ascoschoengastia indica and Walchia ewingi. Rattus tanezumi had a stable overall prevalence (PM = 21.10%), mean abundance (MA = 7.01), and mean intensity (MI = 33.20) of chiggers with the same dominant mites in the whole Southwest China in comparison with a previous report in Yunnan Province, but chigger infestations on R. tanezumi varied along different environmental gradients. Rattus tanezumi in mountainous landscape had a higher infestation load of chiggers with higher species diversity than in flatland landscape. The infestation was higher at lower altitudes and latitudes. A high intensity of vegetation coverage was associated with high infestations. The results reflect the environmental heterogeneity of chiggers on the same host species. Warm climate and high relative humidity are beneficial to chigger infestation on R. tanezumi.

Population and chigger mite infection of rodents in Pudong New Area， Shanghai / 上海预防医学

ObjectiveTo investigate the population and chigger mite infection of rodents in Pudong District， Shanghai， so as to provide the scientific basis for the prevention and control of rodents and chigger transmitted diseases. MethodsThe monitoring work was conducted in four points including Xuanqiao， Hangtou， Laogang and Nanhui New Town with night trapping method from 2020 to 2022. Habitats as farmland， wasteland， rural residential areas， and parks were selected. The rodent species were identified and rodent density was calculated. All chigger mites were collected from the earlaps and auricular fossae of the rodents. The species of chigger mites were identified and the chigger mite index was calculated. ResultsA total of 222 rodents were captured. They belonged to 5 species， 4 genera， 2 families and 2 orders， including 4 species， 3 genera， and 1 family of Rodentia and 1 species of Insectivora. M. musculus was the dominant species， with a composition ratio of 54.05%. Total 80 chigger mites were captured， with a detection rate of 36.03%. The total chigger index was 0.36 and Rattus tanezumi held the highest （6.00）， followed by M. musculus （0.48）. There were 3 species of chigger mites， L.deliense， L.scutellare， and L.gaohuense. L.deliense was the dominant specie， accounting for 55.00%. ConclusionThere is a risk of chigger-borne disease transmission in Pudong New Area with M. musculus as the dominant host and L. deliense as the dominant species.

Research progress on the epidemiology of tsutsugamushi disease of summer type in China / 预防医学

@#Tsutsugamushi disease, also known as scrub typhus, is a zoonosis caused by Orientia tsutsugamushi, with rats as the main sources of infection and chigger mites as the only medium of transmission, and has no effective vaccines. Tsutsugamushi disease can be divided into summer, autumn and winter types according to seasons in China, while the summer type is characterized by strong virulence, typical and severe symptoms, high rates of misdiagnosis and mortality. The summer type of tsutsugamushi disease is distributed in the south of 31°N in China, with the epidemic time from June to August, and the cases are predominantly females, farmers and people at ages of over 40 years. Affected by natural environment, social and economic factors, the epidemic areas and the number of cases of summer type of tsutsugamushi disease are increasing continuously. Based on publications pertaining to the epidemiology of summer type of tsutsugamushi disease in China from 1960 to 2023, this review summarizes the mechanism of transmission, epidemiological characteristics and influencing factors, so as to provide the basis for prevention and control of summer type of tsutsugamushi disease in China.

Eschar of scrub typhus.

We report a case of a 60-year-old farmer presented with chief complaints of fever, myalgia, and headache of one week duration. Head-to-toe examination revealed an area of central necrosis surrounded by erythema (suggestive of eschar) on nape of the neck. A diagnosis of scrub typhus was made and the patient improved following 7-days course of doxicycline. Eschar is pathognomonic finding for clinical diagnosis of scrub typhus. This is to conclude, head-to-toe examination is indispensable for all the patients presenting with fever, myalgia, and headache.

Analysis on infestation and related ecology of chigger mites on large Chinese voles (Eothenomys miletus) in five provincial regions of Southwest China.

Based on a long-term field investigation in the five provincial regions of Southwest China between 2001 and 2019, the present paper studied the infestation and related ecology of chigger mites (chiggers) on the large Chinese vole (Eothenomys miletus), an endemic and dominant rodent species in the regions. A total of 52331 chiggers were collected from 2661 voles, and 52261 mites were identified as 185 species and 13 genera in the family Trombiculidae with very high species diversity. The identified 185 chigger species on E. miletus (a single rodent species) even exceeded those recorded in some countries. The overall infestation prevalence (P m  = 53.96%), mean abundance (MA = 19.64) and mean intensity (MI = 36.39) on E. miletus were much higher than those on some other rodent species in the same regions. Although the species composition showed a moderate similarity (J = 0.63) between male and female hosts (E. miletus), the infestation indices (P m  = 56.25%, MA = 21.67) of chiggers on male hosts were higher than those on the females (P m  = 51.23%, MA = 17.09) (P < 0.05). Two dominant chigger species, Leptotrombidium scutellare (C r  = 19.17%) and L. sinicum (C r  = 11.06%), showed an aggregated distribution pattern among different individuals of their host E. miletus, and a relatively high degree of positive association existed between the two dominant chigger species with PCC = 0.57, DI = 0.60 and OI = 0.62 (x 2  = 857.46, P < 0.001). Leptotrombidium densipunctatum, Walchia koi, Helenicula hsui, L. scutellare and W. ewingi showed a high degree of environmental adaptability to their environments with high niche breadths. The theoretical curve of the species abundance distribution of chigger community on E. miletus was successfully fitted with Preston's lognormal distribution model. Based on the theoretical curve fitting, the expected total number of chigger species on E. miletus was roughly estimated to be 223 species, and 38 chigger species were probably missed in the sampling investigation.

Spillover and spillback risks of ectoparasites by an invasive squirrel Callosciurus erythraeus in Kanto region of Japan.

Invasive organisms can alter host-parasite relationships in a given ecosystem by spreading exotic parasites and/or becoming a new reservoir for native ones. Since these problems affect management programs of the invasive host organisms, it is necessary to monitor them individually. The Pallas's squirrel Callosciurus erythraeus is an invasive arboreal mammal introduced into Japan that threatens to exacerbate ecological and public health problems by spreading native and exotic parasites. However, only limited surveys have been available especially for ectoparasites, using the traditional combing method in which the possibility of oversight is inherent. Here, we evaluated the ectoparasite occurrences in Kanto region of Japan, using the whole-shaving method as an alternative approach. As a result of examining 52 hosts from two invaded districts (Yokohama and Yokosuka), chigger mites (Leptotrombidium spp.) and fleas (Ceratophyllus anisus and Ceratophyllus indages indages) were newly recovered in addition to the previously reported tick (Haemaphysalis flava) and exotic lice (Enderleinellus kumadai and Neophaematoponis callosciuri). The parasite burdens were higher in Yokosuka and in male host individuals, affecting infracommunity richness and composition. Our findings on the variety of native and exotic ectoparasites, at higher abundances in some cases than previously known, may suggest that both the spillover and spillback risks need to be adjusted upwards.

Infestation and distribution of chigger mites on Chevrieri's field mouse (Apodemus chevrieri) in Southwest China.

Based on a long-term field investigation on chigger mites in southwest China from 2001 to 2019, the present study analyzed the infestation and distribution of chigger mites on the Chevrieri's field mouse (Apodemus chevrieri) in the region. A total of 12,516 individuals of chigger mites were collected from 1981 A. chevrieri mice, and 12,281 chiggers were identified as 107 species, 11 genera and 3 subfamilies in 2 families, which revealed a high species diversity of the mites on A. chevrieri mice. Of 1981 A. chevrieri mice, 633 ones were infested with chiggers with a relatively high overall prevalence (P M  = 31.95%), mean abundance (MA = 6.32) and mean intensity (MI = 19.77). Of the 107 chigger species identified from A. chevrieri mice, three ones were the most dominant and they were Leptrombidium scutellare, L. densipunctatum and L. cricethrionis, which showed aggregated distribution among different individuals of the mice. A slightly positive association existed between every two dominant chigger species, which implied that the dominant chigger species tend to co-exist on A. chevrieri. The infestations of A. chevrieri with chiggers varied in different latitudes, altitudes and landscapes and they showed some heterogeneity along different environmental gradients. The logistic regression analysis showed that the risk factors for chigger infestations on A. chevrieri were landscapes, ages and altitudes, which implied that the environmental factors and host ages could influence the infestations of the mice with the mites. A theoretical curve of the species abundance distribution of chigger mites on A. chevrieri was successfully fitted by Preston's lognormal model, suggesting that the species abundance distribution conforms to the lognormal distribution pattern. The expected total species of chigger mites on A. chevrieri was roughly estimated to be 136 species and about 29 rare chigger species were probably missed in the sampling field investigation.

Emerging trends of scrub typhus disease in southern Rajasthan, India: A neglected public health problem.

Scrub typhus is the oldest known vector-borne zoonotic infectious disease in the world which is life-threatening for all age groups as it presents acute febrile illness along with multi-organ involvements and spread with the biting of infectious 'Trombiculid mite' (chigger mite). The pathogen of this disease is an obligatory coccobacillus gram-negative rickettsial bacteria Orientia tsutsugamushi. Scrub typhus disease was previously confined geographically only to the Asia Pacific region (tsutsugamushi triangle), but in recent years it has crossed its limit and has spread in other countries beyond the tsutsugamushi triangle and has become more hazardous for the community. The objective of this study is to explore the scrub typhus disease outbreak trends with existing information in southern Rajasthan state, India. This study concluded that scrub typhus disease is being re-emerged again and again in various Indian geographical regions with new species of vectors. The disease has been raised in tremendous amounts in Rajasthan within the last five years especially in the hilly zone and has led to major public health problems with other zoonotic diseases.

Vector and rodent surveillance for Orientia tsutsugamushi in north India.

BACKGROUND & OBJECTIVES: Scrub typhus or chigger borne typhus, caused by Orientia tsutsugamushi is an emerging vector-borne disease as large numbers of cases have been reported in various tropical countries. It is transmitted to humans through bites of infected chiggers (larval mites). The knowledge about the vector, its distribution, density and habitat are important so as to understand the epidemiology of scrub typhus in a given area. To control rickettsial infections, regular rodent-vector surveillance should be planned in areas where the disease transmission is occurring and it will also help to strengthen the existing entomological data related to the vector of scrub typhus in northern India. METHODS: In the present study, rodent-vector surveillance was planned for one whole year, covering both mite active and non-active seasons (October 2019-December 2020) in selected areas of Chandigarh and Punjab in north India. Rodent tissues and mites were also examined for the presence of O. tsutsugamushi by nested PCR for 56 kDa gene and real-time PCR for 47 kDa outer membrane protein gene. 18S gene PCR was performed for molecular identification of mites. RESULTS: In the surveillance, three types of ectoparasite, viz. mites, fleas and ticks were obtained in rodents. All mites found were of Laelapidae family. None of the pooled rodent tissue samples as well as mite samples were found positive for O. tsutsugamushi by nested PCR for rickettsial DNA. INTERPRETATION & CONCLUSION: In the present study, we did not get any evidence of carriage of O. tsutsugamushi in either mites or rodents collected and sampled in selected regions in Chandigarh and Punjab. We need to strengthen the entomological surveillance over a broader region and increase the frequency of trapping rodents to increase clarity on vector-reservoir dynamics in this geographical region.

Infestation and Related Ecology of Chigger Mites on the Asian House Rat (Rattus tanezumi) in Yunnan Province, Southwest China.

This paper is to illustrate the infestation and related ecological characteristics of chigger mites on the Asian house rat (Rattus tanezumi). A total of 17,221 chigger mites were collected from 2,761 R. tanezumi rats, and then identified as 131 species and 19 genera in 2 families. Leptotrombidium deliense, the most powerful vector of scrub typhus in China, was the first major dominant species on R. tanezumi. All the dominant mite species were of an aggregated distribution among different individuals of R. tanezumi. The species composition and infestations of chiggers on R. tanezumi varied along different geographical regions, habitats and altitudes. The species-abundance distribution of the chigger mite community was successfully fitted and the theoretical curve equation was S (R)=37e-(0.28R)2. The total chigger species on R. tanezumi were estimated to be 199 species or 234 species, and this further suggested that R. tanezumi has a great potential to harbor abundant species of chigger mites. The results of the species-plot relationship indicated that the chigger mite community on R. tanezumi in Yunnan was an uneven community with very high heterogeneity. Wide geographical regions with large host samples are recommended in the investigations of chigger mites.

Monitoring Chigger Mites for Orientia tsutsugamushi in Field Small Mammals in Hwaseong-si, Gyeonggi-do, Korea, 2019-2020.

Incidence of tsutsugamushi disease (scrub typhus) caused by Orientia tsutsugamushi, is steadily increasing. It is a mite-borne disease transmitted by chigger mites. In this study, the chigger mites were collected from field small mammals in Hwaseong-si (city), Gyeonggi-do (province), Korea, 2019 and 2020. The field small mammals captured were 56 Apodemus agrarius (94.9%) and 3 Crocidura lasiura (5.1%). A total of 7,531 chigger mites were collected from the captured small mammals. Using PCR test, 153 chigger mite pools were examined and 17 pools were reported positive for O. tsutsugamushi. The O. tsutsugamushi were identified to 5 strains; Jecheon strain was most prevalent, followed by Boryong strain. The other strains were OI011, Taguchi, and Shimokoshi. Collectively, these results provide essential regional information on mite-borne tsutsugamushi disease in the Hwaseong-si, and further contribute to bring awareness and rapid diagnosis for the tsutsugamushi disease.

Research Advances of Leptotrombidium scutellare in China.

Leptotrombidium scutellare is one of the 6 main vectors of scrub typhus in China. It has been found in more than 15 provinces of China. Especially in Yunnan, it was found to be mainly distributed in some mountainous areas with high altitude, low temperature and low precipitation. Rodents and some other small mammals were the most common hosts of L. scutellare. To date, more than 40 host species of L. scutellare have been recorded with very low host specificity, and the main hosts varied in different geographical regions. L. scutellare had a strong resistance against the cold environment, and the temperature and humidity were 2 important factors affecting its growth and development. Among different individuals of their rodent hosts, L. scutellare mites often showed an aggregated distribution pattern, which reflected the interspecific cooperation of the mites. The chromosome karyotype of L. scutellare was 2n=16 and all the 8 pairs of chromosomes were short rod-shaped with metacentric or sub-metacentric types. The isozyme spectrum supported that L. scutellare, L. deliense and L. rubellum were in the same species group. Based on the natural infection, experimental transmission and epidemiological evidence, L. scutellare has been eventually confirmed as the second major vector of scrub typhus in China, which is second only to L. deliense.

A New Genus and Species of Chiggers (Trombidiformes: Leeuwenhoekiidae) From Peru.

South American chiggers have historically been poorly studied, and this has continued into present times. Of the 33 genera in the family Leeuwenhoekiidae Womersley, only Odontacarus Ewing and Sasacarus Brennan & Jones have been reported in Peru. Here, we describe a new genus, Peruacarus n. gen., and a new species, Peruacarus anthurium n. sp., parasitizing Koford's grass mouse, Akodon kofordi Myers & Patton, in Peru.

A Report of Chigger Mites on the Striped Field Mouse, Apodemus agrarius, in Southwest China.

Based on the field investigations in 91 investigation sites (counties) in southwest China between 2001 and 2019, the present paper reported the chigger mites on A. agrarius mice in southwest China for the first time by using a series of statistical methods. From 715 striped field mice captured in 28 of 91 investigated sites, only 255 chiggers were collected, and they were identified as 14 species, 6 genera in 3 subfamilies under 2 families. Of 715 A. agrarius mice, only 24 of them were infested with chigger mites with low overall prevalence (PM=3.4%), overall mean abundance (MA=0.36 mites/host) and overall mean intensity (MI=10.63 mites/host). The species diversity and infestation of chiggers on A. agrarius were much lower than those previously reported on some other rodents in southwest China. On a certain species of rodent, A. agrarius mouse in southwest China seems to have a very low susceptibility to chigger infestations than in other geographical regions. Of 14 chigger species, there were 3 dominant species, Leptotrombidium sialkotense, L. rupestre and Schoengastiella novoconfuciana, which were of aggregated distribution among different individuals of A. agrarius hosts. L. sialkotense, one of 6 main vectors of scrub typhus in China, was the first dominant on A. agrarius. The species similarity of chigger mites on male and female hosts was low with CSS=0.25, and this reflects the sex-bias of different genders of A. agrarius mice in harboring different chigger species.

New Species of Chiggers (Trombidiformes: Trombiculidae and Leeuwenhoekiidae) From the Conservation Unit Parque Nacional da Serra das Confusões, Brazil.

The Piauí State, Brazil, has never had its chigger fauna recorded. In this study, we examined chiggers collected on marsupials, rodents, and lizards from the conservation unit Parque Nacional da Serra das Confusões (PNSC). Herein we describe four new species, Paraguacarus klompenin. sp., Neoschoengastia ochoain. sp., Quadraseta welbournin. sp., and Susa bauchanin. sp. Furthermore, an additional seven species are reported: Eutrombicula alfreddugesi (Oudemans, 1910), Microtrombicula brachytrichiaBrennan, 1971, Microtrombicula rhipidomysiGoff, Whitaker and Dietz, 1983, Parascoschoengastia aemulata (Brennan and Jones, 1964), Parasecia validaBrennan, 1969, Pseudochoengastia petrolinensis Jacinavicius, Bassini-Silva and Barros-Battesti 2019, and Quadraseta flochi (Brennan and Jones, 1960). This is the first report of chiggers in Piauí State, which includes one of the most biodiverse areas in the Caatinga biome and is of particular importance to conservation. The genera Paraguacarus Goff and Whitaker, 1984 and Susa Audy and Nadcharam, 1960 are reported here for the first time to Brazil.