Assessing the underwater survival of two tick species, Amblyomma americanum and Amblyomma maculatum

Developmental stage and level of submersion in water impact the viability of lone star and winter tick eggs

Female ticks deposit large egg clusters that range in size from hundreds to thousands. These egg clusters are restricted to a deposition site as they are stationary, usually under leaf litter and other debris. In some habitats, these sites can be exposed to periodic flooding. When the clusters of tick eggs are disturbed, they may float to the surface or remain underneath organic debris entirely submerged underwater. Here, we examined the viability of egg clusters from winter ticks, Dermacentor albipictus, and lone star ticks, Amblyomma americanum, when partially or fully submerged in water and in relation to the developmental stages of the eggs under lab conditions. In general, egg clusters that were older and partially submerged had a higher viability than fully submerged, younger eggs. Of the two species, A. americanum was more resistant to water exposure. These studies highlight that egg clusters for certain tick species can remain viable when exposed to water for at least two weeks. These results also suggest that distribution by flooding of egg clusters could occur for some species and water submersion will differentially impact tick egg survival based on the specific developmental stage of exposure and species.

Ixodes ricinus ticks survive flooding

Climate-change induced weather extremes like floods are increasing in frequency and intensity, with potential consequences for disease vector ecology. We report on a flooding event during the winter of 2023/2024 in Hanover city, Germany. Our observations demonstrate that I. ricinus, the most important vector of tick-borne diseases in Europe, can survive prolonged periods under water and quickly resume host-seeking activity once conditions normalize. Despite being submerged for a total of 25 days, nymphal and adult ticks were observed questing four weeks of the water receding, with densities comparable to pre-flood levels. These findings underscore the resilience of I. ricinus and highlight the potential of ticks to pose infection risks even after extreme weather events.

Efficacy of a topical combination of esafoxolaner, eprinomectin and praziquantel against Amblyomma maculatum infestations in cats

Amblyomma maculatum, the Gulf Coast tick, infests a wide range of vertebrate species including livestock, dogs, cats, and humans. It is a species of significant veterinary and public health importance, especially as a vector of diseases, for instance American canine hepatozoonosis or tidewater spotted fever. An experimental study was conducted to evaluate the efficacy of NexGard® Combo, a topical endectoparasiticide product for cats combining eprinomectin, praziquantel and esafoxolaner, against induced infestations of A. maculatum in cats. This Good Clinical Practice (GCP) study used a randomized, negative controlled, masked design. Ten cats were allocated to an untreated group and ten to a treated group, dosed once on Day 0 at the minimum label dose. On Days -2, 7, 14, 21, 28, 35, and 42, cats were infested with ~50 unfed adult A. maculatum. On Days 3, 10, 17, 24, 31, 38, and 45, i.e., 72 h after treatment and subsequent infestations, ticks were removed, counted and the numbers of live attached tick in each group were used for efficacy calculations. At each time-point, all untreated cats were adequately infested, demonstrating a vigorous tick population and an adequate study model. The curative efficacy after a single application against existing tick infestation, 72 h after treatment, was 98.7%. The preventive efficacy, 72 h after weekly infestations, over the following five weeks ranged from 93.8% to 99.4%.

Survival of off-host Dermacentor albipictus (Acari: Ixodidae) adult females and larvae underwater

Dermacentor albipictus (Packard, 1869) [Acari: Ixodidae], the winter tick, significantly affects the health and productivity of North American moose (Alces alces (Linnaeus, 1758) [Artiodactyla: Cervidae]). Survival of off-host stages of Ixodid ticks depends on microclimate driven in part by extrinsic factors resulting from weather, such as temperature, humidity, drought, and floods. The impact of some of these abiotic factors is unclear for D. albipictus. The effect of water submergence on biological parameters of engorged, adult, females and unfed larvae was assessed in the laboratory. Survival of adult females after submergence for three days was 88% with significant effects on their ability to oviposit. After five weeks, 63% of larvae (one-month-old) survived submergence in water whereas survival of larvae (three-months-old) was reduced to 23% after seven days. The off-host stages of D. albipictus have variable tolerance to periods of submergence that may influence the number of larvae available on the landscape for recruitment to moose in autumn.

Responses of ticks to immersion in hot bathing water: Effect of surface type, water temperature, and soap on tick motor control

Preventing bites from undetected ticks through bathing practices would benefit public health, but the effects of these practices have been researched minimally. We immersed nymphal and adult hard ticks of species common in the eastern United States in tap water, using temperatures and durations that are realistic for human hot bathing. The effect of (a) different skin-equivalent surfaces (silicone and pig skin), and (b) water temperature was tested on Amblyomma americanum, Dermacentor variabilis and Ixodes scapularis nymphs. Overall, the type of surface had a much larger effect on the nymphs’ tendency to stay in contact with the surface than water temperature did. Most nymphs that separated from the surface did so within the first 10 s of immersion, with the majority losing contact due to the formation of an air bubble between their ventral side and the test surface. In addition, adult Ixodes scapularis were tested for the effect of immersion time, temperature, and soap on tick responsiveness. Some individual adults moved abnormally or stopped moving as a result of longer or hotter immersion, but soap had little effect on responsiveness. Taken together, our results suggest that the surface plays a role in ticks’ tendency to stay in contact; the use of different bath additives warrants further research. While water temperature did not have a significant short-term effect on tick separation, ticks that have not attached by their mouth parts may be rendered unresponsive and eventually lose contact with a person’s skin in a hot bath. It should be noted that our research did not consider potential temperature effects on the pathogens themselves, as previous research suggests that some tickborne pathogens may become less hazardous even if the tick harboring them survives hot-water exposures and later bites the bather after remaining undetected.

Reptile vector-borne diseases of zoonotic concern

Reptile vector-borne diseases (RVBDs) of zoonotic concern are caused by bacteria, protozoa and viruses transmitted by arthropod vectors, which belong to the subclass Acarina (mites and ticks) and the order Diptera (mosquitoes, sand flies and tsetse flies). The phyletic age of reptiles since their origin in the late Carboniferous, has favored vectors and pathogens to co-evolve through millions of years, bridging to the present host-vector-pathogen interactions. The origin of vector-borne diseases is dated to the early cretaceous with Trypanosomatidae species in extinct sand flies, ancestral of modern protozoan hemoparasites of zoonotic concern (e.g., Leishmania and Trypanosoma) associated to reptiles. Bacterial RVBDs are represented by microorganisms also affecting mammals of the genera Aeromonas, Anaplasma, Borrelia, Coxiella, Ehrlichia and Rickettsia, most of them having reptilian clades. Finally, reptiles may play an important role as reservoirs of arborivuses, given the low host specificity of anthropophilic mosquitoes and sand flies. In this review, vector-borne pathogens of zoonotic concern from reptiles are discussed, as well as the interactions between reptiles, arthropod vectors and the zoonotic pathogens they may transmit.

Possible Effects of Climate Change on Ixodid Ticks and the Pathogens They Transmit: Predictions and Observations

The global climate has been changing over the last century due to greenhouse gas emissions and will continue to change over this century, accelerating without effective global efforts to reduce emissions. Ticks and tick-borne diseases (TTBDs) are inherently climate-sensitive due to the sensitivity of tick lifecycles to climate. Key direct climate and weather sensitivities include survival of individual ticks, and the duration of development and host-seeking activity of ticks. These sensitivities mean that in some regions a warming climate may increase tick survival, shorten life-cycles and lengthen the duration of tick activity seasons. Indirect effects of climate change on host communities may, with changes in tick abundance, facilitate enhanced transmission of tick-borne pathogens. High temperatures, and extreme weather events (heat, cold, and flooding) are anticipated with climate change, and these may reduce tick survival and pathogen transmission in some locations. Studies of the possible effects of climate change on TTBDs to date generally project poleward range expansion of geographical ranges (with possible contraction of ranges away from the increasingly hot tropics), upslope elevational range spread in mountainous regions, and increased abundance of ticks in many current endemic regions. However, relatively few studies, using long-term (multi-decade) observations, provide evidence of recent range changes of tick populations that could be attributed to recent climate change. Further integrated 'One Health' observational and modeling studies are needed to detect changes in TTBD occurrence, attribute them to climate change, and to develop predictive models of public- and animal-health needs to plan for TTBD emergence.

Tick-crocodilian interactions: a review, with the first record of tick (Acari: Ixodidae) infestation in the saltwater crocodile (Crocodylus porosus), and a concise host-parasite index

Interactions between ticks and crocodilians (crocodiles, alligators, caiman, and gharials) are poorly studied but may have significant bearing on the ecology and health of these reptiles. The first record of tick infestation of the saltwater crocodile (Crocodylus porosus) is reported along with the first case of infestation by Amblyomma cordiferum on Cuvier's dwarf caiman (Paleosuchus palpebrosus). A review is also provided of tick-crocodilian interactions with a concise host-parasite index.