Outdoor Habitats Research Articles

Report of a new species of sand fly, Phlebotomus (Anaphlebotomus) ajithii n. sp. (Diptera: Psychodidae), from Western Ghats, India

BackgroundWestern Ghats is a biodiversity treasure trove with reports of indigenous leishmaniasis cases. Hence, systematic sand fly surveillance was carried out among the tribal population. The present study reports a novel sand fly species, Phlebotomus (Anaphlebotomus) ajithii n. sp. (Diptera: Psychodidae), discovered in the Western Ghats of India.MethodsA comprehensive sand fly survey was conducted across the Kollam, Thrissur, Idukki, Kasaragod and Malappuram districts of Kerala, India. The survey spanned both indoor and outdoor habitats using standard collection methods over a 3-year, 3-month period. DNA barcoding of samples was performed targeting mitochondrial cytochrome c oxidase subunit I (COI) gene, and the sequence generated was subjected to phylogenetic analysis.ResultsPhlebotomus (Anaphlebotomus) ajithii, a new sand fly species, is recorded and described in this communication. The morphological relationship of the new species to other members of the subgenus Anaphlebotomus is discussed. Mitochondrial COI barcode followed by phylogenetic analysis confirmed that specimens of Ph. ajithii belong to the same taxonomic group, while a genetic distance of 11.7% from congeners established it as a distinct species.ConclusionsThe Western Ghats, known for its rich biodiversity, has lacked systematic entomological surveys focusing on sand flies. This study aims to fill this gap and reports and describes a new species of sand fly.Graphical abstract

Molecular Identification of Host Blood Meal from Phlebotomine Sandflies (Diptera: Psychodidae) from Kerala, India.

Female phlebotomine sandflies serve as vectors for the transmission of Leishmania parasites, perpetuating an enzootic cycle by disseminating between sylvatic and domestic animals. Humans form a part of this cycle because the sandflies search for a blood source required for egg development. The present study aimed to identify the feeding preferences of different sandfly fauna from six districts of Kerala, India, using molecular tools. An entomological survey was conducted during 2021-2023 in Kollam, Kottayam, Thiruvananthapuram, Thrissur, Malappuram, and Palakkad. Both indoor and outdoor habitats were targeted from sandfly collection using different standard tools and methods. Sandflies were identified using standard taxonomic keys, and DNA was extracted from blood meal collected from sandflies. A total of 7366 sandfly specimens were collected during the study period, which belonged to three different genera and 19 species. Blood source was successfully identified from 119 sandflies revealing that the Sergentomyia genus preferably fed on small reptiles and amphibians, whereas Phlebotomus genus was found to mainly feed on mammalian and avian blood. Sergentomyia zeylanica was an exception, as it primarily fed on mammalian blood sources. Interestingly, humans were the second feeding source for Phlebotomus species, which are the proven vectors. Comprehending the feeding patterns of sandflies is crucial, not just for public health but also for obtaining insights into the ecological dynamics between vectors and hosts, ultimately enabling more efficient strategies for disease control and prevention.

Morphological and molecular description of a new species of sandfly, Sergentomyia (Neophlebotomus) ashwanii sp. nov. (Diptera: Psychodidae) from Western Ghats, India

Objective: To report a new species of sandfly, Sergentomyia (Neophlebotomus) ashwanii sp. nov. (Diptera: Psychodidae) from Western Ghats, India. Methods: A systematic sandfly survey was conducted in the Thrissur and Kollam districts of Kerala, India using mechanical aspirators, light and sticky traps, both indoor and outdoor habitats, for a period of one year. Deoxyribonucleic acid barcoding of samples was performed targeting mitochondrial cytochrome oxidase I (COI) gene and sequence generated was subjected to phylogenetic analysis. Results: Sergentomyia (Neophlebotomus) ashwanii, a new sandfly species is recorded and described in this communication. A single row of 10-12 pointed teeth in the cibarium with 4-6 small denticles or fore-teeth are the key characteristics that is distinctive from other members of the subgenus Neophlebotomus. Mitochondrial COI barcode followed by phylogenetic analysis of the nucleotide sequence confirms that specimens of the species belong to the same taxonomic group while the genetic distance (14.2%) with the congeners established it to be a different species. Conclusions: The Western Ghats' being an important biodiversity hotspot and has dearth of systematic entomological surveys on sandflies. The current study tried to fill the void and also report a new sandfly species.

Risks posed by invasive species to the provision of ecosystem services in Europe

Invasive species significantly impact biodiversity and ecosystem services, yet understanding these effects at large spatial scales remains a challenge. Our study addresses this gap by assessing the current and potential future risks posed by 94 invasive species to seven key ecosystem services in Europe. We demonstrate widespread potential impacts, particularly on outdoor recreation, habitat maintenance, crop provisioning, and soil and nitrogen retention. Exposure to invasive species was higher in areas with lower provision of ecosystem services, particularly for regulating and cultural services. Exposure was also high in areas where ecosystem contributions to crop provision and nitrogen retention were at their highest. Notably, regions vital for ecosystem services currently have low invasion suitability, but face an average 77% increase in potential invasion area. Here we show that, while high-value ecosystem service areas at the highest risk represent a small fraction of Europe (0-13%), they are disproportionally important for service conservation. Our study underscores the importance of monitoring and protecting these hotspots to align management strategies with international biodiversity targets, considering both invasion vulnerability and ecosystem service sustainability.

Overnight monitoring reveals the behavioral rhythms of a geriatric male elephant: an animal-centered case study of rest and stereotypy

IntroductionMonitoring overnight behavior is important in assessing the overall wellbeing of ex-situ elephant populations, with recumbent rest and stereotypy as key indicators of welfare. However, there have been few studies that address the overnight behavior of singly housed male elephants with a history of stereotypy. We conducted an opportunistic case study of the overnight behavior (i.e., rest and stereotypy) of a singly housed geriatric male Asian elephant at the Oklahoma City Zoo to identify his overnight behavioral rhythms in response to physiological (musth) and environmental changes (habitat access, automatic timed feeders) and guide management strategies.MethodsInfrared cameras were utilized to conduct continuous focal-animal sampling of the elephant’s behavior between 20:00 and 08:00 in indoor and outdoor habitats. Sampling occurred from January 2023 to October 2023, with a total of 179 overnight observations.ResultsThe elephant exhibited recumbent rest for 175.66 ± 6.80 (mean ± SE) minutes per night and was engaged in stereotypy for 175.88 ± 9.68 minutes per night. While there was no significant relationship between stereotypy and the sexual state of musth, musth was associated with reduced durations of recumbent rest. Access to both indoor and outdoor habitats was significantly related to decreased stereotypy compared to indoor-only treatments. Recumbent rest occurred most frequently between 02:00 and 05:00, and stereotypic behavior was most common between 06:00 and 08:00. Contrary to our expectations, automatic feeders did not significantly reduce stereotypy.DiscussionThe results of this study provide insight into the behavioral patterns of a geriatric male Asian elephant, demonstrating the importance of implementing an animal-centered approach to enhance animal wellbeing. As the zoo-housed Asian elephant population grows and continues to age, this case study emphasizes the importance of developing comprehensive welfare strategies for the elephants in our care.

Formicidae Faunal Succession on Buried Rabbit Carcass: Implications for Forensic Entomology

Background: Buried carrion can help in forensic investigation cases in determining the post-burial-interval (PBI), movement of the body or hiding of the crime. The current study aims to determine the succession of ant species on rabbit carcass buried in an outdoor habitat of the King Saud University, Western Riyadh, Saudi Arabia. Methods: In the present study, twelve rabbits were buried at 20 cm and twelve at 40 cm in two different periods. After 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 days, one cadaver from each depth was unearthed. Results: We have found 8 species of Formicidae, 4 types at a depth of 20 cm and two types only at a depth of 40 cm in the first period, while two types were found at a depth of 20 cm and one type only at 40 cm in the second period of the experiment. In the first period of the experiment, Cataglyphis holgerseni (Formicinae) and Cardiocondyla sp. (Myrmicinae) were the most prevalent species at depths of 20 cm and 40 cm, respectively; however, in the exposed carcasses, Messor ebeninus (Myrmicinae) predominated in both study periods. While no specie dominated the buried bodies in the second phase, as the numbers were very few in the second period on buried carcasses. In this study, many Formicidae species that correlate to different stages of corpse decomposition that were previously unknown from buried bodies in Saudi Arabia were recorded. Therefore, it is important and may have consequences in medicolegal issues.

UV irradiance effects on komodo dragon (Varanus komodoensis) vitamin D3, egg production, and behavior: A case study.

Modifications to UV irradiance for indoor housed herpetofauna can affect behavior and physiology. Low ultraviolet B (UVB) irradiance can result in vitamin D3 deficiency resulting in calcium metabolism disorders including metabolic bone disease and immune suppression. High UVB can result in skin and eye issues, which can be severe enough to cause shock and death. Using tools available for the assessment of UV light, including Ferguson zones and the UV working tool designed by the British and Irish Association of Zoos and Aquaria, we redesigned lighting in our indoor komodo dragon (Varanus komodoensis) habitat to better suit the UV requirements of this species, while studying changes in behavior and physiology. We measured serum vitamin 25-hydroxy D3 values in one male and one female komodo dragon before and after they were housed in indoor and outdoor habitats. We also measured behavior changes in our male komodo as he moved from an outdoor habitat, to an indoor habitat with changing UV irradiance. Our female komodo showed a 98% increase in vitamin D3 values after being moved outdoors, and laid her first clutch of eggs. Our male dragon's vitamin D3 remained consistent 200 days after moving inside. He did show increased activity when higher UV irradiance was available. Importantly, we found the UV lamps we used stopped producing desired UV irradiance within 3.5 months of regular use. We suggest all animal care facilities develop UV monitoring programs to research output and longevity of UVB lamps used in indoor herpetofauna habitats.

Changes in Environment and Management Practices Improve Foot Health in Zoo-Housed Flamingos.

Foot lesions are a highly prevalent phenomenon among zoo-housed flamingos, with up to 99.8% of birds affected. These lesions are a recognized welfare concern, increasing the likelihood of bacterial infections, and even septicemia. Although several risk factors have been linked to foot lesions in flamingos (including age, climate, and substrate), there have been few studies looking at changes in foot lesions over time. This study tracked changes in foot lesions for an individual flock of Chilean Flamingos (97 birds) at Dublin Zoo, Ireland, over an 18-month period in response to a mandatory indoor housing order imposed by the Irish Government as a seasonal precautionary measure to prevent the spread of avian influenza. Using a pre-defined scoring system for four common types of foot lesions (hyperkeratosis, fissures, nodular lesions, and papillomatous growths), we show that providing unrestricted access to outdoor habitats and natural substrates (both terrestrial and aquatic) can improve the health and wellbeing of zoo-housed flamingos. This longitudinal study highlights the importance of regular foot health monitoring in flamingos, and the importance of natural aquatic substrates when managing flamingos. As many zoo-housed birds have been spending more time indoors on artificial substrates over recent years due to avian influenza housing orders, it is critical that we assess the impact of such changes in management and habitat access on bird health and welfare.

Habitat mosaic as a driver of the resilience of native species: The case of the assemblage of small mammals from the city of Franceville, Gabon

AbstractRodents (Rodentia) are the most abundant and diverse order of mammals, present in all habitats, including urban areas. The traffic linked to globalisation has favoured their involvement in biological invasions that have an impact on local biodiversity, the economy and human health. In Franceville, Gabon, little is known about the rodent community. We therefore studied the composition and distribution of rodents along a gradient highlighting the heterogeneity of the city's landscape. The three habitat types studied showed no difference in small mammal abundance, while the diversity index was higher in the vegetated habitat (SDI = 0.73) compared to the outdoor (SDI = 0.71) and indoor (SDI = 0.45) habitats. Our work shows the importance of vegetal remnants in the city for the maintenance of native species. It also highlights the impact of introduced species on small mammal assemblages and the need for management to reduce the factors of their proliferation.

How Sanctuary Chimpanzees (Pan troglodytes) Use Space after Being Introduced to a Large Outdoor Habitat.

Wild chimpanzees live in large, mixed-sex groups that display a fission-fusion social organization. To provide a social environment more like that of wild chimpanzees, Chimp Haven integrated smaller groups of 3-4 individuals into one large group of 18 individuals. This large group was introduced to a 20,234.28 m2 forested habitat and associated indoor areas. This space was designed to allow the individual chimpanzees to choose their proximity to social companions and provide the group with a more natural environment in which they could express more species-typical behavior. The study took place over a 7-month period that began two weeks prior to the first groups being integrated and ended 4 months after the chimpanzees were released into the habitat. We collected data on the chimpanzees' arboreal, terrestrial, indoor, and outdoor spatial use. The chimpanzees' proximity to their nearest neighbor was also recorded, noting whether they were touching or within arm's reach. Data were collected during daytime and nighttime hours and were utilized to make management decisions about potential group formations. We examined the data using generalized linear mixed models (GLMMs) with individual subjects as a random factor and months as a repeated measure for location and proximity results. There were significant differences in the use of arboreal and outside space over the 7-month time frame, with females more likely to use the arboreal space than males. The chimpanzees were more likely to utilize the habitat over time and increased their proximity to group mates. The results of this study indicate that the chimpanzees responded positively to living in large groups in a spacious naturalistic environment.

Mapping Sonic Futurities

Mapping Sonic Futurities (MSF) combines sound art, listening practices, and ecological research to trace the present and future histories of ecological habitats. The project involves twenty-four-hour “sound vigils” in outdoor spaces and habitats with tenuous futures. During these retreats, the keeper of the vigil commits to being in one location for an entire day and night. For each of the twenty-four hours, they dedicate time to acts of ecologically engaged listening and sounding. This involves making field recordings of the space, performing music that responds to nearby sounds, and/or sitting in meditation with a focus on modes of listening outlined in a series of guided prompts.

Thereuonema tuberculata (Wood, 1862) (Chilopoda, Scutigeromorpha, Scutigeridae) from forested habitats in North America

Thereuonema tuberculata (Wood, 1862) is an anthropophilic centipede originating from Asia. Introduced populations were recently reported from inside buildings in the United Kingdom and the USA; however, this centipede has not been reported from outdoor habitats where it is an introduced species. We report established populations of T. tuberculata in two forested and lakeside habitats in Nebraska, USA, which indicates this species has a widely dispersed, established population in the continental USA.

Temperature-dependent population dynamics for Aedes aegypti in outdoor, indoor, and enclosed habitats: a mathematical model for five North American cities.

A model for the Aedes aegypti lifecycle is developed that takes into account temperature-dependent maturation and death rates for several life stages, wet and dry egg oviposition with flooding, as well as three classes of larval habitat with different temperature profiles: outdoor (subject to external temperature fluctuations, human-inhabited), indoor (temperature moderated, human-inhabited, interior), and enclosed (temperature moderated, human free, exterior). An equilibrium analysis shows that the temperature range of outdoor viable equilibrium populations aligns closely with reported risk levels. Temperature patterns for El Paso, Texas; New York, New York; New Orleans, Louisiana; Orlando, Florida; and Miami, Florida, are considered. In four of these locations (all but New York), enclosed habitats can support mosquito populations even if all outdoor and indoor habitats are removed. In two locations (El Paso and New York) the model shows that in spite of the disappearance of adult mosquitoes during colder temperatures, populations reach seasonal steady state due to the survival of eggs. The results have implications for both vector and disease control.

Bionomics of the unexplored sand flies fauna of District Mohmand, Khyber Pakhtunkhwa, Pakistan: assessing risk factors associated with cutaneous leishmaniasis.

Sand flies are of considerable public health importance in Pakistan because these insects are vectors of leishmaniasis. The current study explores the bionomics of sand flies, their spatial distribution pattern and cutaneous leishmaniasis-associated risk factors in District Mohmand, Khyber Pakhtunkhwa, Pakistan. Sand flies were collected from indoor and outdoor habitats in 69 villages of five tehsils in Mohmand during July-October 2019. Risk factor data were recorded for 829 households in 94 villages. In total, 2065 sand flies were captured. Phlebotomus (Paraphlebotbmus) sergenti was the most abundant species. Relative density for P. sergenti and Phlebotomus papatasi was highest in Prang Ghar and lowest in Safi. Sand flies abundance peaked in August and September, corresponding to maximum relative humidity, temperature and rainfall. Relative density for P. sergenti and P. papatasi was highest in combined dwellings (indoor) and cattle corrals (outdoor). Phlebotomus sergenti and P. papatasi were abundant at an elevation of 283-1140 m on agricultural land and rangelands. Both species were recorded abundantly on Carbontites, Mesozoic and Indus suture Melange rock formations. Presence of domestic animals, ownership of pet dogs, presence of muddy dunes in the village, knowledge of sandflies and use of mosquitoes spray remained significant risk factors. The study reports sand fly bionomics in District Mohmand. Risk identified for cutaneous leishmaniasis are significant in strategising control methods for Health authorities can allocate localized control means to high-risk areas using these findings.

A rapid entomological reconnaissance during the first Zika outbreak in Thiruvananthapuram city, Kerala, India

There was an outbreak of Zika virus in Thiruvananthapuram city of Kerala state, India in July 2021. In order to ascertain the prevalence and breeding pattern of the potential vectors, a study was conducted from 22 July 2021 to 27 July 2021. Breeding habitat surveys were conducted in seven localities in the city from where Zika cases were reported. House to house searches were conducted from mosquito breeding in 35-40 houses in each locality. Fourth instar larvae were identified using larval keys and later confirmed their identities after emergence. Lower instar larvae were reared in the laboratory and were identified after emergence using adult keys. Larval indices were calculated using WHO methods. Of the 280 houses surveyed mosquito breeding was encountered in 38 houses. Three Aedes species viz., Ae. aegypti, Ae. albopictus and Ae. vittatus were detected. Ae. agypti and Ae. albopictus were breeding in 30.5% and 43.9% of the outdoor habitats and 56.0% and 16.0% of the indoor habitats respectively. The overall Container Index for (CI), Breteau Index (BI) and House Index (HI) for both species together were 56.07, 23.07 and 14.61 respectively. Two established urban Zika vectors viz., Ae. aegypti and Ae. albopictus were prevalent in the city with very high container indices. For the first time in the world, indoor flower vases used for money plant has been observed as an important breeding habitat of Aedes mosquitoes. Rapid elimination of the breeding habitats with community support is recommended to reduce the larval indices.

Characterization of sand fly breeding sites in district Malakand, Khyber Pakhtunkhwa, Pakistan, and evaluation of risk factors for cutaneous leishmaniasis in the region.

Present study was carried to determine the sand fly species composition, breeding sites ecology, seasonal abundance, and spatial distribution in district Malakand, Khyber Pakhtunkhwa, Pakistan. In addition, risk factors associated with cutaneous leishmaniasis (CL) were also evaluated. Survey of indoor and outdoor habitats was carried out using sticky traps in 31 villages of Dargai and Batkhela tehsils of Malakand. Soil from habitats of adult and immature sand flies was analysed. Questionnaire-based household survey was also performed in these villages to assess risk factors associated with CL. Soil samples from selected CL positive households were analysed for its contents. Additionally, clinicoepidemiological data from local health centres was examined for the year 2019. Total of 3,140 sand flies belonging to 18 species were collected. Phlebotomus sergenti was the most abundant species (38.16%). Its abundance had a strong positive correlation with mean monthly relative humidity and negative correlation with average temperature. Phlebotomus sergenti and Phlebotomus papatasi were abundant at an elevation ranging from 320 to 1,120m above sea level and in agricultural lands near human settlements. Flight height preference apparatus collected maximum sand flies at 30cm (1ft) above the ground and all species associated negatively with height. Soil analysis from habitats of adult and immature flies showed that highest mean number of adults and immatures were recorded from silt loam which carried highest concentrations of K2 O, Mg, Ca, and Zn. Number of immature sand flies correlated moderately (r=.7, p<.05) with K2 O soil concentrations. There was significant similarity between organic matter contents in soil samples from positive breeding sites and CL households (Wilcoxon rank-sum test, p=.1976). In multivariate analysis model for CL risk factors, age (26-35 and >35years), knowledge of leishmaniasis, living in a middle and upper class, preachers visit to villages, and assumption that Afghan refugees are more prone to CL were significant. CL patient's archived data from health centres showed that majority of patients had lesions on face and hands. Patient's influx was highest in February and March.

Insect faunal succession on buried goat carcass in Aligarh Region of Uttar Pradesh, India, with implications in forensic entomology

BackgroundStudies on the insect fauna of animal corpses, used as a vertebrate model, may help forensic investigation cases to estimate the post-mortem-interval (PMI), cause of death, and crime-scene location. Likewise, entomofauna of buried corpses can assist in determining the post-burial-interval (PBI), movement of the body or hiding of the crime. The bodies buried under the soil decompose at a slower rate than the body exposed. Also, there are fewer insects that can go underground to locate the corpse. Such types of studies on the insect fauna of buried carrion can help in forensic investigation cases. The current study aims to determine the succession of a goat carcass buried shallowly in an outdoor habitat of the Aligarh Region, North India.ResultsIn the present study, we examined a goat carcass buried at a depth of nine inches to determine the type of insects capable of colonizing buried animal carcass in the study area of Aligarh, Uttar Pradesh, India. We have found five species of Diptera, three species of Coleoptera, one Hemipteran species, and one Hymenopteran species. Adult Dipterans found during different samplings were Megaselia scalaris (Loew 1866), Chrysomya megacephala (Fabricius 1794), and Calliphora vicina (Robineau-Desvoidy, 1830). Dipterans’ immature stages were found to be of Synthesiomyia nudiseta (van der Wulp, 1883) and Hydrotaea capensis (Wiedemann, 1830) Megaselia scalaris. Adults of Saprinus quadriguttatus (Fabricius, 1798), Saprinus splendens (Paykull, 1811), and Onthophagous quadridentatus (Fabricius, 1798) of order Coleoptera. Adult Cydnus species (Fabricius, 1803) of Hemiptera and Dorylus species (Fabricius, 1793) of Hymenoptera have also been recorded. During the sampling, the authors reported the stages of carcass disintegration and the insects associated with it.ConclusionsFlies, beetles, and ants have been recorded in association with the buried goat carcass, which may add to the knowledge of colonization of buried bodies in India and around the globe. S. nudiseta, H. capensis, and M. scalaris, which are found on the goat carrion in the current study, have also been reported on human corpses in the past. Furthermore, M. scalaris found consistently on two sampling dates beneath the ground on the goat carcass and was also seen running on the grave’s surface. In addition, authors have reported several species belonging to different order and families, corresponding to various stages of decomposition of corpse which were earlier not known from buried corpses from India. So, it is crucial and may have implications in medicolegal cases.

Infestation and distribution of chigger mites on Brown rat (Rattus norvegicus) in Yunnan Province, Southwest China.

Chigger mites is a group of arthropods and some of them are vectors of scrub typhus. As a common synanthropic rodent species, the Brown rat (Rattus norvegicus) often harbors lots of ectoparasites including chigger mites. According to some "data mining" strategies, the present study took the advantage of the abundant original data from a long-term field ecological investigation between 2001 and 2015 to make a detailed analysis of chigger mites on R. norvegicus in Yunnan Province, Southwest of China. From 18 of 33 investigated counties, only 1414 chigger mites were collected from 1113 Brown rats with relatively low infestations. The 1414 individual chigger mites were identified as comprising 61 species, 11 genera and 2 subfamilies of the family Trombiculidae with a high species diversity (S=61, H'=3.13). Of 61 mite species, there were four main species, Walchia ewingi, Ascoschoengastia indica, W. koi and A. rattinorvegici, which accounted for 44.41% of the total mites. All the chigger mites were of aggregated distribution among different individuals of R. norvegicus. The Brown rats in the outdoor habitats harbored much more individuals and species of chigger mites with a higher mean abundance (MA=1.46) and mean intensity (MI=12.53) than in the indoor habitats (P<0.05). The overall infestation of the rats was significantly higher in the mountainous landscapes than in the flatland landscapes (P<0.001). The species similarity (Css) of the mites on the male and female rats reached 64.44% with sex biased infestations. The male rats harbored more species and individuals of the mites than the female rats. The adult rats harbored more species and individuals of the mites than the juvenile rats. The species abundance distribution of the mites was successfully fitted by Preston's lognormal model with ŝ(R)=15e-[0.31(R-1)]2 (α=0.31, R2=0.95). On the basis of fitting the theoretical curve by Preston's model, the total mite species on R. norvegicus was estimated to be 86 species, and 25 rare mite species were missed in the sampling field investigation. The curve tendency of the species-plot relationship indicates that R. norvegicus have a great potential to harbor many species of chigger mites, and more species of the mites would be collected if more rats are sampled.

Distribution and host selection of the chigger mite vector of scrub typhus, Leptotrombidium deliense, in southwest China

ABSTRACT Leptotrombidium deliense (Walch) is believed to be the most important vector of scrub typhus in China. From 2001–2019, a long-term investigation was made in 82 counties of southwestern China, covering five provincial divisions: Yunnan, Guizhou, Sichuan, Tibet and Chongqing. The results showed that L. deliense was not the most dominant chigger species in southwestern China. A total of 8,385 L. deliense were collected from 13 counties, which accounted for only 5.42% of all the identified chiggers (299 species with 154,665 individuals). Leptotrombidium deliense was mainly distributed in the low latitude (21–22°N: 48.16%), low elevation (<1000 m: 81.75%), flat landscape (70.14%) and outdoor habitat (90.66%). Although 73.98% of L. deliense were collected from the Asian house rat (Rattus tanezumi), the mite had low host specificity, being collected from 22 species of rodents and other small mammals across different species, genera, families and orders. Leptotrombidium deliense was of an aggregated distribution among its animal hosts.

Distribution and Host Selection of Tropical Rat Mite, Ornithonyssus bacoti, in Yunnan Province of Southwest China.

Simple SummaryThe tropical rat mite (Ornithonyssus bacoti) is a transmission vector of rickettsia pox and a potential vector of hemorrhagic fever with renal syndrome (HFRS). This article reports the distribution and host selection of O. bacoti in Yunnan Province of Southwest China. The original data came from the investigations in 39 counties of Yunnan. The prevalence (PM), mean abundance (MA) and mean intensity (MI) were calculated to reflect the infestations of the dominant rat hosts with O. bacoti mites. The patchiness index and Taylor’s power law were used to measure the spatial distribution of the mites. A total of 4121 O. bacoti mites were identified from 15 species of small mammal hosts in 27 of the 39 investigated counties, and 99.20% of them (4088/4121) were found on rodents. The majority of total O. bacoti mites was found in the flatland landscape (91.28%) and indoor habitat (73.48%). Moreover, 51.78% and 40.09% of O. bacoti mites were identified from Rattus tanezumi and R. norvegicus, the two synanthropic rat species. The mites had some host-specificity, with a preference to two dominant hosts (R. tanezumi and R. norvegicus), and they were of aggregated distribution on R. tanezumi.(1) Background: As a species of gamasid mite, the tropical rat mite (Ornithonyssus bacoti) is a common ectoparasite on rodents and some other small mammals. Besides stinging humans to cause dermatitis, O. bacoti can be a vector of rickettsia pox and a potential vector of hemorrhagic fever with renal syndrome (HFRS). (2) Objective: The present study was conducted to understand the host selection of O. bacoti on different animal hosts and the distribution in different environmental gradients in Yunnan Province of Southwest China. (3) Methods: The original data came from the investigations in 39 counties of Yunnan, between 1990 and 2015. The animal hosts, rodents and some other small mammals were mainly trapped with mouse traps. The O. bacoti mites on the body surface of animal hosts were collected and identified in a conventional way. The constituent ratio (Cr), prevalence (PM), mean abundance (MA) and mean intensity (MI) were used to reflect infestations of animal hosts with O. bacoti mites. The patchiness index and Taylor’s power law were used to measure the spatial distribution pattern of O. bacoti mites on their hosts. (4) Results: A total of 4121 tropical rat mites (O. bacoti) were identified from 15 species and 14,739 individuals of hosts, and 99.20% of them were found on rodents. More than half of O. bacoti mites (51.78%) were identified from the Asian house rat (Rattus tanezumi), and 40.09% of the mites from the Norway rat (R. norvegicus) (p < 0.05). The infestations of R. tanezumi (PM = 7.61%, MA = 0.40 and MI = 5.31) and R. norvegicus (PM = 10.98, MA = 1.14 and MI = 10.39) with O. bacoti mites were significantly higher than those of other host species (p < 0.05). The infestations of two dominant rat hosts (R. tanezumi and R. norvegicus) with O. bacoti mites varied in different environmental gradients (latitudes, longitudes, altitudes, landscapes and habitats) and on different sexes and ages of the hosts. The prevalence of juvenile R. norvegicus rats with O. bacoti mites (PM = 12.90%) was significantly higher than that of adult rats (PM = 9.62%) (p < 0.05). The prevalence (PM = 38.46%) and mean abundance (MA = 2.28 mites/host) of R. tanezumi rats with O. bacoti mites in the high latitude were higher than those in the low latitudes (p < 0.05). The majority of the total collected 4121 O. bacoti mites was found in the flatland landscape (91.28%) and indoor habitat (73.48%) (p < 0.05). The PM (10.66%) and MA (0.49 mites/host) of R. tanezumi rats with O. bacoti mites were significantly higher in the indoor habitat than in the outdoor habitat (p < 0.05). The tropical rat mites showed an aggregated distribution pattern on their first dominant host, R. tanezumi. Conclusion: The tropical rat mite (O. bacoti) is a widely distributed species of gamasid mite in Yunnan Province, Southwest China, and its dominant hosts are two synanthropic species of rats, R. tanezumi and R. norvegicus. It is mainly distributed in the flatland landscape and indoor habitat. It has some host-specificity, with a preference to rodents, especially R. tanezumi and R. norvegicus. The O. bacoti mites are of aggregated distribution on R. tanezumi rats.