Flea Abundance Research Articles

Effects of individual characteristics and seasonality and their interaction on ectoparasite load of Daurian ground squirrels in Inner Mongolia, China

Understanding the drivers of parasite distribution is vital for ecosystem health, disease management, and vector monitoring. While studies note the impact of host sex, size, behavior, and season on parasite load, concurrent assessments of these factors and their interactions are limited. During the spring, summer and autumn seasons from 2021 to 2023, we trapped Daurian ground squirrel (Spermophilus dauricus), a small rodent species that inhabits eastern Asian grasslands in Inner Mongolia and collected their ectoparasites. Using machine learning Lasso regression, we pinpointed factors affecting tick and flea abundance on S. dauricus. We then analyzed these factors and their seasonal interactions with a mixed negative binomial generalized linear model. Our study revealed significant but inconsistent seasonal effects on the load of ectoparasites. The tick load was significantly higher in spring and summer compared to autumn, while the flea load was higher in summer and autumn but lacked statistical significance. Furthermore, individual factors that influence the flea and tick load were moderated by seasonal effects, with a male bias in flea parasitism observed in spring. Significant interactions were also found among seasonality, sex, and body weight. The load of male squirrel fleas was positively correlated with body weight, with the highest increase observed in spring. On the contrary, the flea load of female squirrels showed a negative correlation with body weight, significantly decreasing in the autumn with increasing weight. Significant interactions were observed between season and survival status, with hosts exhibiting higher tick load during autumn survival. Our findings underscore the importance of considering seasonal variation in parasitism and the interactions between seasonal dynamics and host biological traits in shaping parasite distributions.

Distribution and abundance of fleas and rodents of plague importance in the erstwhile endemic states and international seaports of India

Rodents are the reservoirs of the plague bacterium Yersinia pestis, which is transmitted through the bites of infected fleas. In this paper, we studied the distribution and abundance of fleas and rodents in the erstwhile endemic states and seaports of India from 2009 to 2019. The analysis showed that the Rattus rattus (Rr) was the major rodent species found in both Western (66.52 %) and Eastern (48.95 %) seaports of India and the other rodent species recorded were Bandicota indica (Bi) (16.68 % & 34.24 %), Bandicota bengalensis (Bb) (8.88 % & 16.02 %) Rattus norvegicus (Rn) (6.83 % & 0.70 %), Murines hurriane (Mh) (1.08 % & 0 %), Mus musculus (Mm) (0 % & 0.09 %), respectively. Only two flea species namely, Xenopsylla cheopis (X.c) and Xenopsylla astia (X.a) were recorded during the study period in Eastern and Western seaports. Among them, X. astia was found to be the dominant species (55.56 %) and followed by X. cheopis (44.44 %). Further, the female population of X. cheopis and X. astia was higher in both Western and Eastern seaports than the male population. Similarly, Rattus rattus (Rr) (82.43 %,) was the major rodent species found in erstwhile endemic states of India, followed by Tetera indica (Ti) (11.99 %,). Only northern endemic states (HP and UK) reported Rattus rattus terkiminasis (R.rt) (0.01 %). Four flea species namely, Xenopsylla cheopis (64.89 %), Xenopsylla astia (34.89 %), Stivalius ahalae (0.18 %), and Nosopsyllus fasciatus (0.02 %) were recorded from endemic states. The presence of rodents and vector fleas warrants sustained plague surveillance in and around seaports and endemic states.

Ecological and faunistic features of fleas in the Transcaucasian mounthill natural plague foci in Azerbaijan

Among all vectors of natural focal infections, fleas are the most active. In this respect, entomological and epizootological monitoring has always been of great importance. This article, based on the material collected from the Transcaucasian foothill natural plague focus, presents the results of a study of flea species diversity, the landscape and geographical area of their distribution. The goal of this work was to determine the diversity of flea species, their distribution and abundance based on the results of epizootological studies conducted in areas with different landscapes in the Transcaucasian foothill natural plague focus of Azerbaijan. The material for the study was obtained during epizootological studies and observations conducted in the spring and autumn seasons of 2020–2023. in the Transcaucasian foothill natural plague focus of Azerbaijan (Bozchol, Mil-Mugan, Eastern and Western Jeyranchel, Gobustan, Absheron, semi-deserts of Kilazi, Sitalchay). Collection, packaging, transportation, and marketing of the material were carried out on the basis of relevant biosafety rules and delivered for further study to the Special Dangerous İnfections Control Center. In total, 61,087 nest tracks were examined, and 7,939 fleas were collected and delivered. The material was processed and identified in the laboratory in accordance with the current regulatory and methodological document on the safety of working with pathogenic biological agents (PBA) of pathogenicity groups I–IV. As a result of sample identification, the species composition of fleas was determined and grouped by geographical areas and landscapes. Research was also carried out (using the PCR method) for the presence of the plague causative agent - Yersinia pestis. According to the results of the study, it was found that, regardless of the biocenotic and climatic characteristics of individual sectors of the Transcaucasian foothill natural plague focus of Azerbaijan, there may be enough carriers of infectious diseases and their growth increases over the years. The frequency of occurrence of the prevailing genera of fleas - Xenopsylla and Nosopsyllus- depends on the natural and climatic conditions of the focus being studied. The analysis for the presence of the plague causative agent among all fleas caught and studied did not give positive results. For the timely detection of epizootics among wild rodents and bloodsuckers, it is important to conduct regular epizootic surveys in enzootic areas for plague.

Host selection and influencing factors of parasitic fleas on the body surface of desert rodents, Inner Mongolia, China

Fleas frequently parasitize rodents and serve as major vectors for many zoonotic diseases. The Alxa Desert in Inner Mongolia, China, is a typical arid region in Asia, which is suitable for the coexistence of a variety of rodents in this environment. Understanding the host selection of fleas among these rodents and the factors influencing this selection is crucial for comprehending rodent-borne diseases and the vector roles of fleas. This study utilized live-trap methods to capture rodents coexisting in the Alxa Desert from April to October 2022. Body surface fleas were collected and analyzed for abundance across different hosts, sexes, and reproductive statuses. The results indicated that: (1) there were significant differences in the species and abundance of parasitic fleas on different rodent species, with Ophthalmopsylla kiritschenkoi and Mesopsylla hebes preferring the Dipus sagitta and Orientallactaga sibirica as their hosts, and Xenopsylla conformis preferring Meriones meridianus as its host. (2) Fleas exhibited sex-preferential host selection, showing a greater preference for male hosts. (3) Among rodents of different reproductive states, most fleas prefer to parasitize individuals in non-reproductive periods. (4) The mean abundance of fleas varied significantly between seasons (P < 0.05), with spring and autumn being the peak periods for flea parasitism. (5) Factors influencing the mean abundance of fleas included host species, sex, reproductive status, and season, with host species having the greatest impact.

On-host flea phenology and flea-borne pathogen surveillance among mammalian wildlife of the pineywoods of East Texas.

Flea-borne diseases are endemic in Texas, U.S.A., with an increasing incidence of flea-borne typhus and cat scratch disease. Knowledge of flea natural history could provide information to protect public health, yet many knowledge gaps remain outside of plague-endemic regions. Our objective was to characterize seasonal activity patterns of fleas on common mammalian wildlife species and test fleas and wildlife for Rickettsia and Bartonella pathogens. We performed one year of monthly trapping for rodents and medium-sized mammals in a national forest with high recreational use and urban encroachment in East Texas. From 90 mammal captures representing seven species, 101 fleas were collected representing Polygenis spp., Ctenocephalides felis, and Orchopeas species. Virginia opossums (Didelphis virginianus) hosted 99% of the collected fleas (100 fleas) and a single flea was on an eastern woodrat (Neotoma floridana). Flea infestation prevalence of opossums was 79% (23/29). Mean flea abundance was 4.39 fleas, with intensity peaking in spring. One cat flea removed from an opossum was positive for Bartonella henselae. Furthermore, we identified tissue or blood of four raccoons (Procyon lotor) and one golden mouse (Ochrotomys nuttalli) positive for Rickettsia amblyommatis. These findings provide an ecological basis for the maintenance of vectors and pathogens from sylvatic settings.

On Microflora of Entomoparasitic Nematodes from Long-Tailed Souslik Fleas in Tuva Mountain Natural Plague Focus

Entomoparasitic nematodes have a specific role to play in the persistence of Yersinia pestis in natural foci, however their natural microbial environment has not been studied.The aim of the study was to search for bacteria associated with nematodes parasitizing fleas-vectors of plague in the Tuva natural focus.Materials and methods. Fleas were collected during the planned epizootiological surveillance in May, 2017 and 2018. During the taxonomic identification of insects, the presence of parasitic nematodes was recorded. In 2017, bacteriological examination of fleas affected by nematodes and those free from them was carried out separately without dissection. The presence and number of bacteria colonies on the agar plates were taken into account. The results were evaluated by conventional methods using the Excel program. The t-criterion, one-factor analysis of variance were employed. In 2018, 84 invaded fleas were dissected. Extracted nematodes were suspended in Hottinger’s broth, followed by cultivation of grown bacteria on Hottinger’s agar. Systematic position of isolated cultures was determined through mass spectrometric analysis (MALDI-TOF) and partial sequencing of 16S rRNA.Results and discussion. In 2017, 30 samples of fleas with helminthes and 276 without helminthes were bacteriologically examined, including 23 samples infested and 145 non-infested specimens of the main vector, Citellophilus tesquorum. Statistical differences in the proportion of samples contaminated by unpretentious bacteria and effect of flea abundance in the sample on the number of colonies grown have not been revealed. In 2018, 26 cultures of bacteria of the genera Serratia, Staphylococcus, Pseudomonas, Acinetobacter, Macrococcus, and Bacillus were isolated from 23 samples of entomoparasitic nematodes. Possible ways of their penetration into flea imagoes are discussed.

Socio-ecological risk factors associated with human flea infestations of rural household in plague-endemic areas of Madagascar.

Plague is a flea-borne fatal disease caused by the bacterium Yersinia pestis, which persists in rural Madagascar. Although fleas parasitizing rats are considered the primary vectors of Y. pestis, the human flea, Pulex irritans, is abundant in human habitations in Madagascar, and has been found naturally infected by the plague bacterium during outbreaks. While P. irritans may therefore play a role in plague transmission if present in plague endemic areas, the factors associated with infestation and human exposure within such regions are little explored. To determine the socio-ecological risk factors associated with P. irritans infestation in rural households in plague-endemic areas of Madagascar, we used a mixed-methods approach, integrating results from P. irritans sampling, a household survey instrument, and an observational checklist. Using previously published vectorial capacity data, the minimal P. irritans index required for interhuman bubonic plague transmission was modeled to determine whether household infestations were enough to pose a plague transmission risk. Socio-ecological risk factors associated with a high P. irritans index were then identified for enrolled households using generalized linear models. Household flea abundance was also modeled using the same set of predictors. A high P. irritans index occurred in approximately one third of households and was primarily associated with having a traditional dirt floor covered with a plant fiber mat. Interventions targeting home improvement and livestock housing management may alleviate flea abundance and plague risk in rural villages experiencing high P. irritans infestation. As plague-control resources are limited in developing countries such as Madagascar, identifying the household parameters and human behaviors favoring flea abundance, such as those identified in this study, are key to developing preventive measures that can be implemented at the community level.

Ecological characterization of fleas on small mammals in natural and disturbed landscapes in the Atlantic Forest ecoregion, Argentina.

To understand the ecoepidemiology of fleas and their interactions with domestic and wild animals, it is necessary to decode the cycles of flea abundance in relation to host species and environmental factors. The province of Misiones, known for its biodiversity and land use changes, provides an excellent study location. We assessed the diversity, prevalence, abundance, and parasitic intensity of fleas collected from 1153 rodents and opossums in various environments in the Upper Paraná Atlantic Forest of Argentina, considering phytogeography and land use. Our findings were consistent with previous studies conducted in humid regions of Argentina and the Atlantic Forest in Brazil. Hosts with high population density exhibited greater flea prevalence and abundance, and widely distributed hosts showed higher flea species richness and diversity. Significant similarities in flea similarity indices among phytogeographic areas, especially in forest. Environments with an anthropogenic gradient exhibited marked dissimilarities, with higher species richness and diversity in less disturbed sites. These parameters may be influenced by the presence of polyxenous Ctenocephalides, Polygenis, and Adoratopsylla fleas co-infesting opossum in urban areas. These findings provide valuable insights into the ecoepidemiology of fleas, their relationships with host species, and the impact of environmental factors in a strategic Atlantic forest ecoregion.

Population dynamics of plague vector fleas in an endemic focus: implications for plague surveillance.

Plague is a zoonotic vector-borne disease caused by the bacterium Yersinia pestis. In Madagascar, it persists in identified foci, where it is a threat to public health generally from September to April. A more complete understanding of how the disease persists could guide control strategies. Fleas are the main vector for transmission between small mammal hosts and humans, and fleas likely play a role in the maintenance of plague. This study characterized the dynamics of flea populations in plague foci alongside the occurrence of human cases. From 2018 to 2020, small mammals were trapped at sites in the central Highlands of Madagascar. A total of 2,762 small mammals were captured and 5,295 fleas were collected. The analysis examines 2 plague vector species in Madagascar (Synopsyllus fonquerniei and Xenopsylla cheopis). Generalized linear models were used to relate flea abundance to abiotic factors, with adjustments for trap location and flea species. We observed significant effects of abiotic factors on the abundance, intensity, and infestation rate by the outdoor-associated flea species, S. fonquerniei, but weak seasonality for the indoor-associated flea species, X. cheopis. A difference in the timing of peak abundance was observed between the 2 flea species during and outside the plague season. While the present study did not identify a clear link between flea population dynamics and plague maintenance, as only one collected X. cheopis was infected, the results presented herein can be used by local health authorities to improve monitoring and control strategies of plague vector fleas in Madagascar.

EVALUATING BAITS WITH LUFENURON AND NITENPYRAM FOR FLEA CONTROL ON PRAIRIE DOGS (CYNOMYS SPP.) TO MITIGATE PLAGUE.

Plague, caused by Yersinia pestis, is a widespread threat to endangered black-footed ferrets (Mustela nigripes) and their primary prey, prairie dogs (Cynomys spp.). Wildlife biologists most commonly manage plague using insecticides to control fleas, the primary vectors of Y. pestis. We tested edible baits containing the insecticides lufenuron and/or nitenpyram in prairie dogs. During a laboratory study, we treated 26 white-tailed prairie dogs (Cynomys leucurus) with lufenuron at 300 mg/kg body mass. All animals remained clinically healthy over the 9 wk monitoring period. Although serum lufenuron concentrations were >130 ppb in two treatment groups at week 1, concentrations declined to ≤60 ppb after 3 wk in non-torpid prairie dogs and after 7 wk in torpid prairie dogs. In a field experiment, we tested baits containing a combination of 75 mg lufenuron and 6 mg nitenpyram, respectively, in black-tailed prairie dogs (Cynomys ludovicianus). We uniformly distributed baits at 125 baits/ha on two plots (treated once) and 250 baits/ha on two plots (each treated twice 4.4 wk apart). Following treatments, flea abundance increased on prairie dogs and remained stable in burrows. Our findings indicate that baits containing lufenuron and nitenpyram, at the reported treatment rates, are ineffective tools for flea control on prairie dogs. Future experiments might evaluate efficacy of higher doses of lufenuron and nitenpyram, and repetitive treatments at differing intervals over time to evaluate potentially therapeutic treatments.

Is there a role for aromatic plants in blue tit (Cyanistes caeruleus) nests? Results from a correlational and an experimental study

The utility of fresh green material in avian nests is still not fully understood. Potential explanations include the effects of plants’ volatile compounds on parasite reduction (nest protection hypothesis) or direct beneficial effects on nestling condition (drug hypothesis). We used correlative data collected during 2020 and 2021 in a Mediterranean population of blue tits (Cyanistes caeruleus) as well as experimental data (aromatic nest content manipulation) to assess the effects of aromatic plant use on nestling physiological condition and survival, nest-dwelling ectoparasitic pressure and its relationship with breeding parameters. We found that aromatic plants were disproportionally used in relation to their abundance in the environment and that their use was positively related to egg mass (but only in 2020). Blowflies and facultative parasitic mites were more frequent in nests with aromatics compared to nests without aromatics, but obligatory parasitic mites were less abundant in nests with aromatics. However, no effects of aromatic plants were observed on nestling haemoglobin levels nor erythrocyte sedimentation rate or other physiological health metrics, but the heterophil to lymphocyte ratio was higher in nests with the highest quantity of aromatics. The artificial addition of mint reduced the flea abundance, but 7-day old nestlings showed significantly lower colour saturation and brightness in the mouth flange. Nestling survival to fledging was not related to aromatic plant use. Therefore, our results partially support a beneficial effect of aromatic plants in blue tit nests because some ectoparasite groups were reduced. Immediate effects on nestling physiology or survival could not be established.Significance statementSome avian species place fresh aromatic plant material in their nests, and several non-mutually exclusive hypotheses have been proposed to explain its potential functions. In this study, we use both correlational and experimental data from a blue tit population to test two hypotheses, namely the ‘nest protection hypothesis’ and the ‘drug hypothesis’. The first one proposes that aromatic plants have direct repellent effects against ectoparasites, while the latter poses that these plant components benefit nestling condition through the stimulation of some components of the immune system. Our results suggest that some ectoparasites, such as fleas and obligatory parasitic mites, were less abundant in nests where aromatic plants were artificially or naturally added, respectively, but no relationships were detected with nestling physiology or survival, which could be partially explained by our small sample size. Our study partially supports a beneficial effect of aromatic plants in avian nests.

Host body mass, not sex, affects ectoparasite loads in yellow-necked mouse Apodemus flavicollis

We investigated the presence and potential causes of sex bias in ectoparasite infestations in the yellow-necked mouse Apodemus flavicollis. We compared the natural tick and flea burdens of male and female mice in a temperate beech forest and assessed whether the observed differences were driven by host sex or body mass. We found that males were more heavily infested by ticks compared to female mice. However, this difference was driven by host body mass, and not sex itself. Host body mass positively correlated with flea loads, but there was no evidence of sex bias in flea abundance. In addition, the abundance of both ticks and fleas infesting yellow-necked mice changed over time, both seasonally (month to month) and annually (year to year). Our results underscore the importance of the sexual size dimorphism and the parasite taxon as the primary factors that influence the occurrence of sex-biased parasitism in small mammals.

Influence of biotic and abiotic factors on flea species population dynamics on Lasiopodomys brandtii.

Brandt's Vole (Lasiopodomys brandtii) is one of the most abundant rodent species in the grasslands of Inner Mongolia, China, and one of the main carriers of Yersinia pestis, the plague bacterium. There have been several instances of plague transmission among L. brandtii, and all of their dominant flea species are known carriers of plague. Little work has been done to understand the regulation of flea abundance on L. brandtii by biotic and abiotic factors. Here, we examine the impacts of host and climate variation on flea abundance on L. brandtii in May, July, and September of 2021 in the East Ujumqin Banner, Xilinhot City, Inner Mongolia Autonomous Region. We arrived at the following conclusions: 1) There were 8 flea species representing 2 families and 5 genera collected from L. brandtii, and Frontopsylla luculenta, Neopsylla pleskei orientalis, and Amphipsylla primaris mitis were most common. 2) Host body weight, host age, season, temperature, and humidity are key factors influencing flea abundance on L. brandtii. 3) Flea species vary in their respective responses to factors.

FLEA CONTROL ON PRAIRIE DOGS (CYNOMYS SPP.) WITH FIPRONIL BAIT PELLETS: POTENTIAL PLAGUE MITIGATION TOOL FOR RAPID FIELD APPLICATION AND WILDLIFE CONSERVATION.

Sylvatic plague is a widespread, primarily flea-vectored disease in western North America. Because plague is highly lethal to endangered black-footed ferrets (Mustela nigripes, BFFs) and the prairie dogs (Cynomys spp., PDs) on which BFFs depend for habitat and prey, minimizing the impacts of plague is a priority at BFF reintroduction sites. We developed a new, flour-based bait pellet containing 0.84 mg of fipronil and weighing ∼1.25 g (FipBits). We measured the degree and duration of flea control on black-tailed PDs (C. ludovicianus) in Montana and on Gunnison's PDs (C. gunnisoni) in Arizona, USA from 2018-2020. FipBits were distributed on treated plots one time at a rate of 125/ha. Fleas were virtually eliminated in Montana from 1 mo posttreatment to 1 yr later and remained substantially depressed 2 yr posttreatment. With the split colony design, we probably underestimated the degree of flea control achieved with FipBits due to crossover edge effects along the arbitrary line dividing the plots. Flea control in Arizona was significant from 1 mo posttreatment to 1 yr later, but flea abundance had recovered by 2 yr posttreatment. Flea control was evaluated from 2020-2021 in South Dakota, USA on four plots treated with three concentrations of fipronil in FipBits (0.68, 0.71, and 0.83 mg/FipBit). Fleas were essentially eliminated for 10 mo on the 0.83-mg plot and were substantially reduced on the two 0.71-mg plots. Fleas were reduced on the 0.68-mg plot, but the degree of control was less than observed on other treated plots. Impacts of plague on PDs and BFFs would probably be greatly reduced by the levels of flea control observed with FipBits. Options for expanded FipBit evaluations are being pursued for what may become a highly practical, affordable, and effective plague mitigation tool.

Assessment of the effect of contemporary climate warming on the small ground squirrel fleas population dynamics in Northwestern region of Caspian Depression

The dominant zonal rodent species in the steppes and semi-deserts of the Caspian Lowland is the small ground squirrel Spermophilus pygmaeus (Pallas, 1778). Flea species, which are its specific ectoparasites, play a significant role in the occurrence of plague epizootics in this area. The impact of global climate warming on the population dynamics of the fleas of the small ground squirrel in the northern deserts on the territory of the Caspian Lowland is discussed in this article. The literature sources and extensive archival materials were used for the analysis. The Ilmen-Pridelta landscape region (southwest of the Astrakhan Region), which is most fully characterized through the necessary quantitative indicators, was chosen as a model territory. The data of the annual spring-summer registration of indices of the flea abundance in wool and at the entrances of the burrows of the small ground squirrel, as well as his abundance rates (number of specimens per 1 ha), average monthly air temperature values reported by meteorological stations in Astrakhan over the past 70 years were statistically processed. The article reveals the mechanism of the influence of contemporary climate warming on the dynamics of the number of fleas of the small ground squirrel in the territory of the Caspian Lowland over the period of 1950-2021.

Influence of nest box design and nesting material on ectoparasite load for four woodland passerines

ABSTRACT Capsule Abundance of haematophagous ectoparasites in woodland passerine nests is influenced by complex interactions between nest box design, bird species, amount of nesting material and nest composition. Aims To analyse ectoparasite abundance relative to nest box design (old wooden nest boxes present for over 2 years versus new wooden nest boxes of the same dimensions vs deep wooden nest boxes designed to reduce predation risk) and bird species (Blue Tit Cyanistes caeruleus, Great Tit Parus major, Pied Flycatcher Ficedula hypoleuca and Eurasian Nuthatch Sitta europaea). The potential influence of amount of nesting material and nest composition was also studied. Methods After fledging, nests were collected from nest boxes. Ectoparasites and nest materials were identified and quantified. Generalized linear modelling was used to examine the influence of nest box design, bird species, amount of nest material and nest composition on ectoparasite loads. Akaike’s Information Criterion was used to select optimal models. Results Abundance of Hen Fleas Ceratophyllus gallinae and parasitic Blowfly Protocalliphora was significantly higher for deep nest boxes than nest boxes of standard dimensions. Old nest boxes had significantly higher loads than new nest boxes, despite thorough cleaning between breeding seasons. Hen Flea abundance was highest in Eurasian Nuthatch nests. Blowfly abundance was highest in Pied Flycatcher nests. Abundances of both fleas and blowfly were positively related to nest mass and amount of animal hair in the nest, and, for parasitic Blowfly, were negatively related to the amount of tree bark. Conclusion Ectoparasite load depends not only on bird species but also nest box design and nesting material. We recommend: (1) nest boxes are regularly replaced to reduce parasite load; (2) deep nest boxes are not used as the large nests constructed not only remove anti-predator benefits of eggs/chicks being harder to reach but are also associated with high haematophagous ectoparasite loads.

Plague mitigation for prairie dog and black-footed ferret conservation: Degree and duration of flea control with 0.005% fipronil grain bait

Sylvatic plague, a primarily flea-borne zoonosis, is a significant threat to prairie dogs (Cynomys spp., PDs) and their specialized predators, endangered black-footed ferrets (Mustela nigripes, BFFs). Host-fed fipronil baits have proven effective in controlling fleas on PDs for the purposes of plague mitigation and BFF conservation. Currently, annual treatments are the norm. We tested the long-term efficacy of fipronil bait treatments with black-tailed PDs (C. ludovicianus, BTPDs) and BFFs in South Dakota, USA. During 2018–2020, we provided BTPDs on 21 sites with grain bait formula, laced with 0.005% fipronil (50 ​mg/kg); 18 non-treated sites functioned as baselines. In 2020–2022, we live-trapped, anesthetized, and combed BTPDs for fleas. Flea control was significant for at least 639–885 days. Flea abundance on the treated sites was < 0.5 fleas/BTPD for ∼750 days. During 2020–2022, we sampled BFFs for fleas on 4 BTPD colonies treated with fipronil grain bait and 8 non-treated colonies. Flea control was significant with BFFs, but flea abundance began to rebound within ∼240 days post-treatment. When feasible, the combination of insecticide treatments, such as fipronil baits, and BFF vaccination against plague provide a “two-pronged” protection approach for these endangered carnivores. If fipronil bait treatments are less effective with predatory BFFs than PDs, as found herein, the “two-pronged” approach might be used to protect BFFs and biennial fipronil bait treatments might be used to protect PDs. If BFF vaccination is not possible, or few BFFs can be vaccinated, annual fipronil bait treatments might be used as a precaution to protect BFFs. Flea densities might be surveyed to determine when/where more frequent treatments seem useful.

A low‐pressure compressed air insecticide applicator to manage plague on prairie dog colonies using all‐terrain vehicles

AbstractVector control is an important tool for plague management in native wildlife such as prairie dogs (Cynomys spp.) and black‐footed ferrets (Mustela nigripes). Given the success of previous prototype high‐pressure air (HPA) dusters, we developed a low‐pressure air (LPA) duster that can be mounted on and powered via all‐terrain vehicle (ATV). We describe the duster prototype and compare performance to commercially available dusters and previous high‐pressure air dusters. In 2021, we infused 0.05% deltamethrin (dust) into black‐tailed prairie dogs burrows (C. ludovicianus) in Larimer County, Colorado. We then captured prairie dogs and compared flea abundance and prevalence on a site dusted with prototype LPA dusters to a non‐dusted site. The mean amount of dust (g) dispensed per burrow was higher using the LPA duster ( = 6.37, 95% CI = 6.24–6.50) from ATVs when compared to HPA prototypes ( = 5.39, 95% CI = 5.27–5.52, P ≤ 0.01) and the commercial dusters used previously ( = 5.29, 95% CI = 5.05–5.50). Low‐pressure air and HPA dusters had shorter operating time than the commercial dusters (1 second per burrow versus = 7.69, 95% CI = 7.42–7.95, P ≤ 0.01). Mean flea abundance and prevalence of flea infestation in 2021 was lower on the site dusted with prototype LPA dusters ( = 0.13 fleas, 95% CI = 0.00–0.31, prevalence = 0.065) than on a non‐dusted site ( = 8.61 fleas, 95% CI = 6.05–11.17, P ≤ 0.01, prevalence = 1.0). The LPA dusters offer several advantages over previous duster designs, including continuously generated low‐pressure compressed air, a durable build, and efficient operation from ATVs. Future work should focus on calibration at higher doses of dust and assessment of larger air tanks and more durable fuse systems. Accurate and efficient equipment along with quality control monitoring are vital to the ongoing success of vector control as a plague management tool.

Potential Effects of Environmental Conditions on Prairie Dog Flea Development and Implications for Sylvatic Plague Epizootics.

Fleas are common ectoparasites of vertebrates worldwide and vectors of many pathogens causing disease, such as sylvatic plague in prairie dog colonies. Development of fleas is regulated by environmental conditions, especially temperature and relative humidity. Development rates are typically slower at low temperatures and faster at high temperatures, which are bounded by lower and upper thresholds where development is reduced. Prairie dogs and their associated fleas (mostly Oropsylla spp) live in burrows that moderate outside environmental conditions, remaining cooler in summer and warmer in winter. We found burrow microclimates were characterized by stable daily temperatures and high relative humidity, with temperatures increasing from spring through summer. We previously showed temperature increases corresponded with increasing off-host flea abundance. To evaluate how changes in temperature could affect future prairie dog flea development and abundance, we used development rates of O. montana (a species related to prairie dog fleas), determined how prairie dog burrow microclimates are affected by ambient weather, and combined these results to develop a predictive model. Our model predicts burrow temperatures and flea development rates will increase during the twenty-first century, potentially leading to higher flea abundance and an increased probability of plague epizootics if Y. pestis is present.

From trees to fleas: masting indirectly affects flea abundance on a rodent host.

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow-necked mice in beech forest after 2 mast and 2 non-mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density-dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance ("dilution," which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump-shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation.