Parasitized or non-parasitized, why? A study of factors influencing tick burden in roe deer neonates.

Ixodes ricinus , the most common species of tick in Europe, is known to transmit major pathogens to animals and humans such as Babesia spp. or Borrelia spp.. Its abundance and distribution have been steadily increasing in Europe during recent decades, due to global environmental changes. Indeed, as ticks spend most of their life in the environment, their activity and life cycle are highly dependent on environmental conditions, and therefore on climate or habitat changes. Simultaneously, wild ungulates have expanded their range and increased dramatically in abundance worldwide, in particular roe deer ( Capreolus capreolus ), have allowed tick populations to grow and spread. Currently, tick infestation on newborn wild ungulates is poorly documented. However, newborn ungulates are considered more sensitive to tick bites and pathogen transmission because of their immature immune system. Thus, improving knowledge about the factors influencing tick infestation on newborns is essential to better understand their health risks. This study was conducted at Trois-Fontaines forest, Champagne-Ardenne, France (1992-2018). Based on a long-term monitoring of roe deer fawns, we used a novel Bayesian model of the infestation of fawns to identify which biotic or abiotic factors are likely to modify the level of infestation by ticks of 965 fawns over time. We show that tick burden increased faster during the first days of life of the fawns and became constant when fawns were 5 days old and more, which could be explained by the depletion of questing ticks or the turnover of ticks feeding on fawns. Moreover, the humidity, which favors tick activity, was weakly positively related to the tick burden. Our results demonstrate that tick infestation was highly variable among years, particularly between 2000 and 2009. We hypothesize that this results from a modification of habitat caused by hurricane Lothar.

Integrated Tick Management in Guilford, CT: Fipronil-Based Rodent-Targeted Bait Box Deployment Configuration and Peromyscus leucopus (Rodentia: Cricetidae) Abundance Drive Reduction in Tick Burdens

Integrated tick management (ITM) is a comprehensive strategy used to reduce presence of ticks and their associated pathogens. Such strategies typically employ a combination of host and non-host targeted treatments which often include fipronil-based, rodent-targeted bait boxes. Bait boxes target small-bodied rodents, specifically white-footed mice (Peromyscus leucopus Rafinesque) that not only play a crucial role in the blacklegged tick (Ixodes scapularis Say (Ixodida: Ixodidae)) life cycle, but also in the transmission of numerous pathogens, primarily Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner (Spirochaetales: Spirochaetaceae), the causal agent of Lyme disease. This study aimed to determine the effect of bait box deployment configuration on tick burden reduction while also further exploring bait consumption and P. leucopus abundances as measures of bait box usage and effectiveness. Boxes were deployed on nine properties within each of six neighborhoods (n = 54) in two different configurations: grid and perimeter. Multiple factors were analyzed as potential predictors for reduction in tick burdens using a backward stepwise selection procedure. Results confirmed the perimeter configuration was a more effective deployment strategy. In addition, overall P. leucopus abundance was a significant predictor of tick burden reduction while bait consumption was not. These findings not only further support the recommended perimeter deployment configuration but provide insight into effective utilization in areas of high P. leucopus abundance. The identification of this significant relationship, in addition to configuration, can be utilized by vector control professionals and homeowners to make informed decisions on bait box placement to make sustained impacts on the I. scapularis vector and associated pathogens within an ITM framework.

Winter Tick Burdens for Moose Are Positively Associated With Warmer Summers and Higher Predation Rates

Climate change is expected to modify host-parasite interactions which is concerning because parasites are involved in most food-web links, and parasites have important influences on the structure, productivity and stability of communities and ecosystems. However, the impact of climate change on host–parasite interactions and any cascading effects on other ecosystem processes has received relatively little empirical attention. We assessed host-parasite dynamics for moose (Alces alces) and winter ticks (Dermacentor albipictus) in Isle Royale National Park over a 19-year period. Specifically, we monitored annual tick burdens for moose (estimated from hair loss) and assessed how it covaried with several aspects of seasonal climate, and non-climatic factors, such as moose density, predation on hosts by wolves (Canis lupus) and wolf abundance. Summer temperatures explained half the interannual variance in tick burden with tick burden being greater following hotter summers, presumably because warmer temperatures accelerate the development of tick eggs and increase egg survival. That finding is consistent with the general expectation that warmer temperatures may promote higher parasite burdens. However, summer temperatures are warming less rapidly than other seasons across most regions of North America. Therefore, tick burdens seem to be primarily associated with an aspect of climate that is currently exhibiting a lower rate of change. Tick burdens were also positively correlated with predation rate, which could be due to moose exhibiting risk-sensitive habitat selection (in years when predation risk is high) in such a manner as to increases the encounter rate with questing tick larvae in autumn. However, that positive correlation could also arise if high parasite burdens make moose more vulnerable to predators or because of some other density-dependent process (given that predation rate and moose density are highly correlated). Overall, these results provide valuable insights about interrelationships among climate, parasites, host/prey, and predators.

Molecular detection of dugbe orthonairovirus in cattle and their infesting ticks (Amblyomma and Rhipicephalus (Boophilus)) in Nigeria

Dugbe orthonairovirus (DUGV), a tick-borne zoonotic arbovirus, was first isolated in 1964 in Nigeria. For over four decades, no active surveillance was conducted to monitor the spread and genetic variation of DUGV. This study detected and genetically characterized DUGV circulating in cattle and their infesting ticks (Amblyomma and Rhipicephalus (Boophilus)) in Kwara State, North-Central Nigeria. Blood and or ticks were collected from 1051 cattle at 31 sampling sites (abattoirs and farms) across 10 local government areas of the State. DUGV detection was carried out by RT-qPCR, and positive samples sequenced and phylogenetically analysed. A total of 11824 ticks, mostly A. variegatum (36.0%) and R. (B.) microplus (63.9%), were obtained with mean tick burden of 12 ticks/cattle. Thirty-four (32 A. variegatum and two R. (B.) microplus) of 4644 examined ticks were DUGV-positive, whereas all of the cattle sera tested negative for DUGV genome. Whole genome sequence (S, M and L segments) and phylogenetic analyses indicate that the positive samples shared up to 99.88% nucleotide identity with and clustered around the Nigerian DUGV prototype strain IbAr 1792. Hence, DUGV with high similarity to the previously characterised strain has been detected in Nigeria. To our knowledge, this is the first report of DUGV in North-Central Nigeria and the most recent information after its last surveillance in 1974.

Effect of Anti-acaricide Treatment on Tick Species Present and Performance of Growing Beef Heifers

The Edwards Plateau region of Texas is largely used for grazing cattle and small ruminants. Tick parasitism in range livestock can occur year-round with direct production losses manifested as body weight or condition. The objective was to assess two acaricide treatments on the active tick burden on livestock within two forage growing seasons (winter through summer). At the Sonora AgriLife Station, 22 Bos taurus crossbred heifers (248 ± 47 kg) were maintained on 97 hectares of rangeland. Tick burden was assessed by individual animal inspection every two wk from 18-Dec-2019 to 11-May-2020 (Season 1) and from 8-Jun-2020 to 3-Aug-2020 (Season 2). Acaricide treatment was applied each date to heifers chosen randomly to serve in the non-treated control (control: 11 heifers) or acaricide-treated (treatment: 11 heifers) groups. Season 1 acaricide treatment was a pour-on synthetic pyrethroid (11 dates) and Season 2 was a diluted synthetic pyrethroid whole-body spray (5 dates). Tick species observed included Amblyomma americanum and Dermacentor albipictus. Tick burden (total counts) and body condition score differences were determined by analysis of variance procedures. For tick burden, there were significant differences (P < 0.0012) between treatment (0.528 ± 0.06) and control (0.819 ± 0.06) heifers in Season 1 (0.673 ± 10.44), and no differences (P > 0.11) between treatment (0.642 ± 0.07) and control (0.799 ± 0.07) heifers in Season 2 (0.721 ± 2.64). For body condition score, there were no differences (P > 0.72) between treatment (5.61 ± 0.04) and control (5.59 ± 0.04) heifers in Season 1 nor Season 2 (5.51 ± 0.005 and 5.80 ± 0.47, respectively). Season 1 acaricide treatment was effective in controlling tick burden (efficacy = 3–4 wk) as compared to Season 2 (efficacy = 1–2 wk). Tick burdens observed under the conditions of this study had no effect on body condition.

Repeatable differences in exploratory behaviour predict tick infestation probability in wild great tits

Ecological factors and individual-specific traits affect parasite infestation in wild animals. Ixodid ticks are important ectoparasites of various vertebrate hosts, which include passerine bird species such as the great tit (Parus major). We studied various key ecological variables (breeding density, human disturbance) and phenotypic traits (exploratory behaviour, body condition) proposed to predict tick infestation probability and burden in great tits. Our study spanned 3 years and 12 nest box plots located in southern Germany. Breeding, adult great tits were assessed for exploration behaviour, body condition, and tick burden. Plots were open to human recreation; human disturbance was quantified in each plot as a recreation pressure index from biweekly nest box inspections. Infested individuals were repeatable in tick burden across years. These repeatable among-individual differences in tick burden were not attributable to exploration behaviour. However, faster explorers did have a higher infestation probability. Furthermore, body condition was negatively correlated to tick burden. Recreation pressure was correlated to increased infestation probability, although this relationship was just above the threshold of statistical significance. Our study implies that avian infestation probability and tick burden are each determined by distinct phenotypic traits and ecological factors. Our findings highlight the importance of animal behaviour and human disturbance in understanding variation in tick burden among avian hosts. Significance statement Various abiotic and biotic factors, including personality type, influence tick parasitism in birds, but exactly how all these factors interplay remains unclear. We studied a wild population of great tits over a 3-year period and assessed birds for their exploration behaviour and tick infestation. We found that more explorative great tits were more likely to be infested with ticks. By contrast, faster explorers did not have higher tick burdens. Tick burden was nevertheless moderately repeatable among individuals. Our results imply that animal personality influences the probability of parasite infestation, and that infestation likelihood versus intensity are determined by distinct mechanisms. Our work highlights the importance of animal behaviour to understand parasite infestation in wild populations.

A field study on the relationship between tick burden and deltamethrin resistance in Rhipicephalus microplus isolates of Indian household cattle

A total of 2809 ixodid ticks were collected by screening 4560 household cattle from six different agro-climatic zones of Tamil Nadu, a southern state of India. Among the ixodid ticks, Rhipicephalus microplus tick isolates were subjected to Adult Immersion Test (AIT) and Larval Packet Test (LPT) using deltamethrin. The mean % of ixodid tick infested cattle population was 63.2%±10.9. Positive correlation was found between the tick burden on household cattle and Resistance Factor (R=0.66). Further, 44% variance in the tick burden on cattle is explained by LPT based resistance factor suggesting deltamethrin resistance level is one of the contributing factors to the tick load on cattle. Analysis of DNA sequence of sodium channel gene domain II-S4-5 linker region of all deltamethrin resistant R. microplus tick isolates, confirmed the absence of point mutation at the 190th nucleotide which suggests the possible mutation in other regions of sodium channel gene of R. microplus tick isolates of south India and/or alternate resistance mechanisms.

Prevalence of Winter Ticks (Dermacentor albipictus) in Hunter-Harvested Wild Elk (Cervus canadensis) from Pennsylvania, USA (2017–2018)

Winter ticks (Dermacentor albipictus) are an aggressive one-host tick that infest a wide-diversity of ungulates. Infestations can result in anemia, alopecia, emaciation, and death. Most notably, the winter tick has caused negative impacts to moose (Alces alces) populations in the northeast United States and Canada. Winter ticks have been identified on other cervid species, including deer (Odocoileus virginianus) and elk (Cervus canadensis), which generally results in low tick burdens and mild or no disease. Recently, however, a wild yearling bull elk in Pennsylvania was found dead as a result of severe winter tick infestation. To obtain baseline data on winter ticks in wild elk in Pennsylvania, we collected 1453 ticks from 190 hunter-harvested wild elk between 2017–2018. Of the 204 harvested elk, 94.3% (190/204) had ticks collected for this study and none of the sampled elk had evidence of winter-tick associated disease. The average tick burden was 7.7 ticks/elk and average winter tick load on all elk was 0.5. Results of this study indicate that winter ticks do infest wild elk in Pennsylvania. However, during the fall months, the tick burden is low and rarely associated with lesions. These data herein serve as a baseline to monitor winter tick populations over time.