Airborne Dispersal Research Articles

Stochastic microbial dispersal drives local extinction and global diversity.

Airborne dispersal of microorganisms is a ubiquitous migration mechanism, allowing otherwise independent microbial habitats to interact via biomass exchange. Here, we study the ecological implications of such advective transport using a simple spatial model for bacteria-phage interactions: the population dynamics at each habitat are described by classical Lotka-Volterra equations; however, species populations are taken as integer, that is, a discrete, positive extinction threshold exists. Spatially, species can spread from habitat to habitat by stochastic airborne dispersal. In any given habitat, the spatial biomass exchange causes incessant population density oscillations, which, as a consequence, occasionally drive species to extinction. The balance between local extinction events and dispersal-induced migration allows species to persist globally, even though diversity would be depleted by competitive exclusion, locally. The disruptive effect of biomass dispersal thus acts to increase microbial diversity, allowing system-scale coexistence of multiple species that would not coexist locally.

Fungi: friends or foes-an outreach science initiative for the collection of airborne fungal spores by high school students.

Fungi mostly reproduce through spores that are adapted for airborne dispersal; hence, fungal spores (and fungi) are found virtually everywhere. Fungi can be "friends or foes." Our friends include fungi used in the food and biotech industries, fungi that contribute to the cycling of carbon and nutrients, and those involved in the decontamination of polluted soils and/or water, to mention just a few examples. Many species, however, are foes-they are detrimental to plants, animals, and/or humans. Annually, >1.5 million people die due to invasive fungal infections. With the aim of enhancing microbiology literacy and the understanding of microbial concepts, we set up a project for the collection of airborne spores (the principal agent through which human airways are exposed to fungi). Students from five high schools in the Oeiras municipality partnered with us as citizen scientists; they carried out sampling by collecting fungal spores on adhesive stickers. The fungal spores collected by the students were subsequently processed in the schools and our research laboratory. Results obtained by the students themselves revealed a large variety of fungal species capable of growing in a rich medium at 30°C. In the research laboratory, using selective isolation conditions, 40 thermotolerant fungi were isolated, 32 of which were taxonomically identified as aspergilla, mostly from within the Aspergillus fumigatus taxa, yet exhibiting high genetic heterogeneity. The protocols and results were presented to the students, who were made aware of the local dispersal of airborne fungal spores, including some from potentially pathogenic fungi. Through carrying out scientific activities, the students developed both the interest and the self-confidence needed to implement future environmental investigations.

Needles in haystacks: monitoring the potential escape of bioaerosolised antibacterial resistance genes from wastewater treatment plants with air and phyllosphere sampling.

Wastewater treatment plants are well-known point sources of emissions of antibacterial resistance genes (ARGs) into the environment. Although most work to date has focused on ARG dispersal via effluent, aerial dispersal in bioaerosols is a poorly understood, but likely important vector for ARG dispersal. Recent evidence suggests that ARG profiles of the conifer needle phyllosphere could be used to measure bioaerosol dispersal from anthropogenic sources. Here, we assessed airborne dispersal of ARGs from wastewater treatment plants in Wales, UK and Quebec, Canada, using conifer needles as passive bioaerosol monitors. ARG profiles of wastewater were compared to those of conifer phyllosphere using high-throughput qPCR. ARG richness was significantly lower in conifer phyllosphere samples than wastewater samples, though no differences were observed across the dispersal gradients. Mean copy number of ARGs followed a similar trend. ARG profiles showed limited, but consistent patterns with increasing distance from wastewater treatment plants, but these did not align with those of wastewater samples. For example, proportional abundance of aminoglycosides decreased over the dispersal gradient in Wales, whereas mobile genetic elements showed the inverse relationship. In summary, while distinct ARG profiles exist along dispersal gradients, links to those of wastewater were not apparent.

Impact of airborne algicidal bacteria on marine phytoplankton blooms.

Ocean microbes are involved in global processes such as nutrient and carbon cycling. Recent studies indicated diverse modes of algal-bacterial interactions, including mutualism and pathogenicity, which have a substantial impact on ecology and oceanic carbon sequestration, and hence, on climate. However, the airborne dispersal and pathogenicity of bacteria in the marine ecosystem remained elusive. Here, we isolated an airborne algicidal bacterium, Roseovarius nubinhibens, emitted to the atmosphere as primary marine aerosol (referred also as sea spray aerosols) and collected above a coccolithophore bloom in the North Atlantic Ocean. The aerosolized bacteria retained infective properties and induced lysis of Gephyrocapsa huxleyi cultures.This suggests that the transport of marine bacteria through the atmosphere can effectively spread infection agents over vast oceanic regions, highlighting its significance in regulating the cell fate in algal blooms.

Passage of spores of the dung moss Tayloria callophylla (Splachnaceae) through an avian digestive tract—a novel mode of dispersal?

The dispersal of reproductive material plays a key role in the ecology of plants. Dung mosses (Splachnaceae), have evolved to utilise insects to disperse spores to habitat sites consisting of dung or dead animals—a marked departure from the wind based spore dispersal seen in other mosses. However, adapting to insect dispersal likely precludes long distance airborne dispersal, and limits dispersal events to the movements of the spore bearing insect. However, there are several disjunct populations of these mosses, incompatible with insect dispersal, raising questions over the manner of their origin. Hypotheses put forward include the dispersal of the mosses to these sites by birds. Here, the possibility that insectivorous birds could internally transport spores is explored by feeding insects bearing spores to captive myna birds. We tested if the spores of the New Zealand dung moss, Tayloria callophylla, can survive gut passage. Ultimately 9 of 10 dung samples produced viable moss colonies after a period of 30 days, demonstrating the survival of the spores through an avian digestive tract. Our results provide evidence for a unique model of dispersal in dung mosses, where a spore bearing insect is eaten by a bird that eats insects transports the spores in its gut over a much greater distance than otherwise likely with the insect alone.

Tree Effects on Coffee Leaf Rust at Field and Landscape Scales.

Although integrating trees into agricultural systems (i.e., agroforestry systems) provides many valuable ecosystem services, the trees can also interact with plant diseases. We demonstrate that a detailed understanding of how plant diseases interact with trees in agroforestry systems is necessary to identify key tree canopy characteristics, leaf traits, spatial arrangements, and management options that can help control plant diseases at different spatial scales. We focus our analysis on how trees affect coffee leaf rust, a major disease affecting one of the world's most significant crop commodities. We show that trees can both promote and discourage the development of coffee leaf rust at the plot scale via microclimate modifications in the understory. Based on our understanding of the role of tree characteristics in shaping the microclimate, we identify several canopy characteristics and leaf traits that can help manage coffee leaf rust at the plot scale: namely, thin canopies with high openness, short base height, horizontal branching, and small, dentate leaves. In contrast, at the edge of coffee farms, having large trees with high canopy volume and small, thick, waxy leaves is more useful to reduce throughflow wind speeds and intercept the airborne dispersal of urediniospores, an important consideration to control disease at the landscape scale. Seasonal pruning can help shape trees into the desired form, and trees can be spatially arranged to optimize desired effects. This case study demonstrates the added value of combining process-based epidemiology studies with functional trait ecology to improve disease management in agroforestry systems.

Environmental monitoring for invasive fungal pathogens of ʽŌhiʽa (Metrosideros polymorpha) on the Island of Hawaiʽi

The invasive rust Austropuccina psidii was detected in the Hawaiian Islands in 2005 and has become widely established throughout the archipelago in both native and introduced species of Myrtaceae. Initial predictions about the impacts of the fungus on native ʽōhiʽa lehua (Metrosideros polymorpha), a keystone native tree, have not materialized, but there is ongoing concern that introductions of new genotypes of the fungus could lead to widespread mortality with catastrophic effects on native ecosystems. By contrast, two recently emergent Ascomycete pathogens, Ceratocystis lukuohia (Ceratocystis wilt of ‘ōhi‘a) and C. huliohia (Ceratocystis canker of ‘ōhi‘a), collectively known to cause Rapid ʽŌhiʽa Death (ROD), are causing significant mortality in native forests on Hawaiʻi and Kauaʻi Islands, but pathways of spread are still incompletely understood. We used a network of passive environmental samplers for collecting windblown urediniospores of Austropuccina to evaluate the effectiveness of environmental monitoring to detect seasonal and landscape-scale differences in airborne propagules of this rust on Hawai`i Island. The samplers were also used to determine if windborn ambrosia beetle frass or spores of Ceratocystis can spread long distances. We found frequent detections and regional and seasonal differences in numbers of samplers that were positive for urediniospores of Austropuccinia, but little evidence of long-distance airborne dispersal of the ROD-causing fungi. The simple, inexpensive platform for sampling airborne fungal spores that we used may have value as a monitoring tool for detecting spread of airborne fungal pathogens, evaluating habitats for suitability for restoration efforts, and for detecting new pathogen introductions, particularly new Austropuccinia genotypes both in Hawaiʻi and other parts of the world.

Short Communication: Invasive mollusks Melanoides tuberculata, and Achatina fulica in Southeast Sulawesi, Indonesia

Abstract. Purnama MF, Salwiyah. 2022. Short Communication: Invasive mollusks Melanoides tuberculata, and Achatina fulica in Southeast Sulawesi, Indonesia. Biodiversitas 23: 4770-4774. Southeast Sulawesi Province has natural/artificial inland waters for various usages. For example, freshwater has supported various activities such as agriculture, plantations, inland fisheries, and ecotourism. This study reports the presence of invasive mollusk in freshwater (Melanoides tuberculata) and terrestrial (Achatina fulica) habitats. This study is the first report regarding the spatial distribution of the three invasive mollusk species in the inland waters of Southeast Sulawesi, Indonesia. All administrative areas (17 districts/cities) in Southeast Sulawesi province were invaded by A. fulica and 16 districts/cities by M. tuberculata. These invasive mollusks species are a severe threat to the preservation of native species and human health because they are an intermediate host for several types of parasites, such as the trematode group. The spreading and rapid development of these invasive mollusks is caused by their reproductive ability and resistance to poor environmental quality and airborne dispersal factors by birds, water flow, and commercial activities. This invasive species can directly cause huge economic losses as they become a pest in agricultural activities, plantations, and freshwater fisheries (aquaculture). They also can transmit pathogens and displacement of native species. Therefore, it is recommended to have a preventive effort to tackle the expansion of IAS in Southeast Sulawesi.

Contrasted propensity for waterborne and airborne dispersal between two closely related semi‐aquatic spider species

Abstract Dispersal abilities are important to support metapopulation functioning and species distributions, yet it is rarely accounted for in conservation. Here, we compared the propensity for dispersal between the two fishing spiders present in Europe: the widespread habitat‐generalist Dolomedes fimbriatus and the scarcer red‐listed Dolomedes plantarius. We experimentally tested for airborne and waterborne dispersal using first instar juveniles sampled in nursery webs, and older juveniles. We estimated the propensity for short and long‐distance dispersal of airborne and waterborne behaviours, and we tested the difference between species with generalised linear mixed models. Airborne (ballooning) and waterborne (sailing) behaviours were more frequent for D. fimbriatus than for D. plantarius, indicating a higher propensity of the former for long‐distance dispersal. The frequency of rappelling behaviour, and thus the propensity for short‐distance dispersal, did not differ between species. However, we found contrasting results for short‐distance dispersal on the water, with rowing being more frequent and running less frequent for D. plantarius than for D. fimbriatus. The different propensity for dispersal between the two species might be partly explained by the ecology of D. plantarius, which is known to be more habitat‐specialist and more dependent to water bodies than D. fimbriatus. The limited propensity for dispersal of the red‐listed D. plantarius is another argument for conserving an interconnected network of wetlands in Fennoscandia. Indeed, increased isolation of populations would be detrimental for species maintenance.

Humidity Reduces Rapid and Distant Airborne Dispersal of Viable Viral Particles in Classroom Settings.

The transmission of airborne pathogens is considered to be the main route through which a number of known and emerging respiratory diseases infect their hosts. While physical distancing and mask wearing may help mitigate short-range transmission, the extent of long-range transmission in closed spaces where a pathogen remains suspended in the air remains unknown. We have developed a method to detect viable virus particles by using an aerosolized bacteriophage Phi6 in combination with its host Pseudomonas phaseolicola, which when seeded on agar plates acts as a virus detector that can be placed at a range of distances away from an aerosol-generating source. By applying this method, we consistently detected viable phage particles at distances of up to 18 feet away from the source within 15 min of exposure in a classroom equipped with a state of the art HVAC system and determined that increasing the relative humidity beyond 40% significantly reduces dispersal. Our method, which can be further modified for use with other virus/host combinations, quantifies airborne transmission in the built environment and can thus be used to set safety standards for room capacity and to ascertain the efficacy of interventions in closed spaces of specified sizes and intended uses.

Bacterial Colonisation: From Airborne Dispersal to Integration Within the Soil Community.

The deposition of airborne microorganisms into new ecosystems is the first stage of colonisation. However, how and under what circumstances deposited microorganisms might successfully colonise a new environment is still unclear. Using the Arctic snowpack as a model system, we investigated the colonisation potential of snow-derived bacteria deposited onto Arctic soils during and after snowmelt using laboratory-based microcosm experiments to mimic realistic environmental conditions. We tested different melting rate scenarios to evaluate the influence of increased precipitation as well as the influence of soil pH on the composition of bacterial communities and on the colonisation potential. We observed several candidate colonisations in all experiments; with a higher number of potentially successful colonisations in acidoneutral soils, at the average snowmelt rate measured in the Arctic. While the higher melt rate increased the total number of potentially invading bacteria, it did not promote colonisation (snow ASVs identified in the soil across multiple sampling days and still present on the last day). Instead, most potential colonists were not identified by the end of the experiments. On the other hand, soil pH appeared as a determinant factor impacting invasion and subsequent colonisation. In acidic and alkaline soils, bacterial persistence with time was lower than in acidoneutral soils, as was the number of potentially successful colonisations. This study demonstrated the occurrence of potentially successful colonisations of soil by invading bacteria. It suggests that local soil properties might have a greater influence on the colonisation outcome than increased precipitation or ecosystem disturbance.

Active Microbial Airborne Dispersal and Biomorphs as Confounding Factors for Life Detection in the Cell-Degrading Brines of the Polyextreme Dallol Geothermal Field.

ABSTRACTDetermining the precise limits of life in polyextreme environments is challenging. Studies along gradients of polyextreme conditions in the Dallol proto-volcano area (Danakil salt desert, Ethiopia) showed the occurrence of archaea-dominated communities (up to 99%) in several hypersaline systems but strongly suggested that life did not thrive in the hyperacidic (pH ∼0), hypersaline (∼35% [wt/vol],) and sometimes hot (up to 108°C) ponds of the Dallol dome. However, it was recently claimed that archaea flourish in these brines based on the detection of one Nanohaloarchaeotas 16S rRNA gene and fluorescent in situ hybridization (FISH) experiments with archaea-specific probes. Here, we characterized the diversity of microorganisms in aerosols over Dallol, and we show that, in addition to typical bacteria from soil/dust, they transport halophilic archaea likely originating from neighboring hypersaline ecosystems. We also show that cells and DNA from cultures and natural local halophilic communities are rapidly destroyed upon contact with Dallol brine. Furthermore, we confirm the widespread occurrence of mineral particles, including silica-based biomorphs, in Dallol brines. FISH experiments using appropriate controls show that DNA fluorescent probes and dyes unspecifically bind to mineral precipitates in Dallol brines; cellular morphologies were unambiguously observed only in nearby hypersaline ecosystems. Our results show that airborne cell dispersal and unspecific binding of fluorescent probes are confounding factors likely affecting previous inferences of archaea thriving in Dallol. They highlight the need for controls and the consideration of alternative abiotic explanations before safely drawing conclusions about the presence of life in polyextreme terrestrial or extraterrestrial systems.

Study Invasive Mollusks Melanoides tuberculata and Achatina fulica in District Labuhan Batu Selatan

District Labuhanbatu selatan has natural/artificial inland waters for various usages. For example, freshwater has supported various activities such as agriculture, plantations, inland fisheries, and ecotourism. This study reports the presence of invasive mollusk in freshwater (Melanoides tuberculata) and terrestrial (Achatina fulica) habitats. This study is the first report regarding the spatial distribution of the three invasive mollusk species in the inland waters of District Labuhanbatu selatan. These invasive mollusks species are a severe threat to the preservation of native species and human health because they are an intermediate host for several types of parasites, such as the trematode group. The spreading and rapid development of these invasive mollusks is caused by their reproductive ability and resistance to poor environmental quality and airborne dispersal factors by birds, water flow, and commercial activities. This invasive species can directly cause huge economic losses as they become a pest inagricultural activities, plantations, and freshwater fisheries (aquaculture). They also can transmit pathogens and displacement of native species. Therefore, it is recommended to have a preventive effort to tackle the expansion of in District Labuhanbatu selatan.

Quantifying Airborne Dispersal Route of Corynespora cassiicola in Greenhouses.

Target leaf spot (TLS), caused by Corynespora cassiicola, is an emerging and high-incidence disease that has spread rapidly on the global scale. Aerospores released by infected plants play a significant role in the epidemiology of cucumber TLS disease; however, no data exist concerning the infectiousness and particle size of C. cassiicola aerospores, and the experimental evidence for the aerospores transmission was lacking. In the present study, highly effective approaches to collect and quantify aerospores were developed for exposure chamber and greenhouse studies. Quantifiable levels of C. cassiicola aerospores were detected in 27 air samples from nine naturally infested greenhouses, ranging from 198 to 5,969 spores/m3. The C. cassiicola strains isolated from air samples were infective to healthy cucumber plants. Exposure chambers were constructed to study the characteristics of C. cassiicola aerospores released by artificially infested cucumber plants. The particle size of C. cassiicola ranged predominately from 2.1 to 4.7 μm, accounting for 71.97% of the total amount. In addition, the transmission dynamics of C. cassiicola aerospores from donor cucumber plants to recipient cucumber plants were confirmed in exposure chambers and greenhouses. The concentration of C. cassiicola aerospores was positively associated with cucumber TLS disease severity. This study suggested that aerospore dispersal is an important route for the epidemiology of plant fungal disease, and these data will contribute to the development of new strategies for the effective alleviation and control of plant diseases.

Agricultural fertilization with poultry manure results in persistent environmental contamination with the pathogen Clostridioides difficile.

During a field experiment applying broiler manure for fertilization of agricultural land, we detected viable Clostridioides (also known as Clostridium) difficile in broiler faeces, manure, dust and fertilized soil. A large diversity of toxigenic C. difficile isolates was recovered, including PCR ribotypes common from human disease. Genomic relatedness of C. difficile isolates from dust and from soil, recovered more than 2 years after fertilization, traced their origins to the specific chicken farm that had delivered the manure. We present evidence of long-term contamination of agricultural soil with manure-derived C. difficile and demonstrate the potential for airborne dispersal of C. difficile through dust emissions during manure application. Clostridioides genome sequences virtually identical to those from manure had been recovered from chicken meat and from human infections in previous studies, suggesting broiler-associated C. difficile are capable of zoonotic transmission.

Population dynamics of Hypothenemus hampei (Ferrari) according to the phenology of Coffea arabica L. in equatorial conditions of North Sumatra

In the Toba Highlands of North Sumatra (Indonesia), coffee production (Coffea arabica L. var. Sigarar Utang) is an important outcome for smallholders; however, the attack of the coffee berry borer (CBB) Hypothenemus hampei, is an obstacle for the development of coffee cultivation in this area. This pest causes great economic losses produced by the development of its offspring inside the coffee berries, making it difficult to control. This concerning situation has led us to consider the development of a CBB control strategy, but beforehand, it was necessary to acquire key information on the phenology of the coffee tree and its implication on the bioecology of the pest. Thus, two study designs were set up, one comprising six plots with two different age classes and the other corresponding to a single plot dedicated only to the study of short distance dispersal of CBB. Part of this study focused on the phenology of the coffee trees and showed that berry production mainly takes place in the upper parts of the trees and significantly decreases with tree age. Due to the equatorial climate, berries were practically always present. Berries were produced following two major flowering periods and some minor ones distributed over the year, and harvested at regular intervals. Berry distribution on the branches varied over time. Dynamics of infestations by CBB showed that ripe berries were more infested than unripe berries because they had been exposed longer to CBB attacks, that older trees were more exposed than younger trees and that infestation was evenly distributed along branches. In addition, internode pedestrian dispersal of CBBs was shown to occur, but considerably less frequently than airborne dispersal. In conclusion, it appears that in the agro-climatic context of the Toba region, the virtual year-round presence of berries - which fosters CBB infestations and CBB short-distance dispersal - is a constraint that must be taken into consideration for designing future pest management measures. To this end, it will be necessary in particular to evaluate the potential of trapping mainly used in tropical areas and to put into practice the sanitation harvesting applied in other countries.

Modeling the dispersal of wind-borne pests: Sensitivity of infestation forecasts to uncertainty in parameterization of long-distance airborne dispersal

Modeling dispersal of wind-borne pests can be a valuable tool in a broader context of areawide integrated pest management. In such models both biotic and abiotic factors play important roles. Many aspects of the life cycle and dispersal of the focal species are typically well studied and represented with robust measures. However, some important assessments may be either lacking or based on difficult to obtain measurements. For example, investigations of population processes occurring at broad spatial scales pose logistical difficulties, and consequently the corresponding estimates may be biased. This is true in the case of long-distance airborne dispersal, in which aloft characteristics of dispersal are particularly difficult to estimate. In this study we assessed the sensitivity of regional infestation forecasts of sorghum by sugarcane aphids [Melanaphis sacchari (Zehntner)] to uncertainty in parameterization of measures meant to represent important aspects of long-distance airborne dispersal in the southern-to-central Great Plains of North America. We focused on dispersal duration, take-off height, and maximum dispersal height as three critical parameters that control wind-borne long-distance dispersal of aphids. The 63 investigated combinations of values of these parameters had largely equivalent region-wide impact on timing of first forecasted infestation (equivalence margin of 7 days) and the impact on the probability of forecasted infestation was equivalent (equivalence margin of 0.1). The spatial variability in estimates depended on local specificity of the modeled landscape, and it was larger in areas where infestations were less frequent, primarily in eastern Kansas, Oklahoma, and northern Texas.

Long-distance airborne dispersal of SARS-CoV-2 in COVID-19 wards

Evidence suggests that SARS-CoV-2, as well as other coronaviruses, can be dispersed and potentially transmitted by aerosols directly or via ventilation systems. We therefore investigated ventilation openings in one COVID-19 ward and central ducts that expel indoor air from three COVID-19 wards at Uppsala University Hospital, Sweden, during April and May 2020. Swab samples were taken from individual ceiling ventilation openings and surfaces in central ducts. Samples were subsequently subjected to rRT-PCR targeting the N and E genes of SARS-CoV-2. Central ventilation HEPA filters, located several stories above the wards, were removed and portions analyzed in the same manner. In two subsequent samplings, SARS-CoV-2 N and E genes were detected in seven and four out of 19 room vents, respectively. Central ventilation HEPA exhaust filters from the ward were found positive for both genes in three samples. Corresponding filters from two other, adjacent COVID-19 wards were also found positive. Infective ability of the samples was assessed by inoculation of susceptible cell cultures but could not be determined in these experiments. Detection of SARS-CoV-2 in central ventilation systems, distant from patient areas, indicate that virus can be transported long distances and that droplet transmission alone cannot reasonably explain this, especially considering the relatively low air change rates in these wards. Airborne transmission of SARS-CoV-2 must be taken into consideration for preventive measures.

Environmental cues for dispersal in a filamentous fungus in simulated islands

Airborne dispersal is a key part of the life history of many saprotrophic fungi. Theory suggests a transition from growth and resource capture to airborne dispersal at some point as the resource availability in a patch declines, but in the absence of an experimental model system this theory has not been empirically tested. For saprobes, resources are arrayed in an ever‐shifting archipelago of islands with the quality of each island being defined by patch size and resource density. We tracked how Phacidium lacerum, a saprotrophic fungus, allocated resources to dispersal in small and large islands of varying resource density through production of fruiting bodies. We found that Phacidium altered the timing and rate of dispersal allocation in response to both patch size and resource density. On small resource islands, Phacidium drastically increased dispersal allocation after reaching the edge of the patch; if resource density was sufficient, on larger resource islands, Phacidium began allocation to dispersal prior to reaching the edge of the island, suggesting an additional absolute total resource level cue. These results are consistent with a two‐cue model for the switch to allocation to airborne dispersal: 1) absolute resource level controlled by the fungus, 2) the fungus’ perception of patch size. This can be thought of as a mix between a full resource allocation switch (bang–bang) if the fungus perceives the patch is fully occupied with a smaller magnitude early shift (bet‐hedging) if absolute resource level crosses a threshold.

Variation in Morphology and Airborne Dispersal of the Urticating Apparatus of Ochrogaster lunifer (Lepidoptera: Notodontidae), an Australian Processionary Caterpillar, and Implications for Livestock and Humans.

True setae borne on the abdominal tergites of Ochrogaster lunifer Herrich-Schӓffer caterpillars are the agents of an irritating contact dermatitis, osteomyelitis, ophthalmia, and severe allergic reactions in humans, and are the cause of Equine Amnionitis and Fetal Loss in Australia. The setae are detached and readily dislodge from the integument whereby they disperse throughout the environment. To better understand the true setae of O. lunifer as agents of medical and veterinary concern, we studied their characteristics and distance dispersed. Whereas members of the European Thaumetopoeinae have been widely studied, their southern-hemisphere counterparts such as O. lunifer are not well known despite their harmfulness and known medical and veterinary importance. The caterpillar’s investment in true setae increased with age and size, and two distinct size classes co-occurred in setae fields. A previously undescribed morphological type of true seta was found on the first abdominal segment. All true setae were calculated to travel long distances in the air even under light breeze conditions. Our results show there is a high risk of exposure to airborne urticating setae within 100 m of elevated caterpillar activity, and a likely risk of exposure for some kilometers in the direction of the prevailing breeze. This information should be used to inform management strategies in areas where urticating processionary caterpillars are active, and especially during periods of an outbreak.