Laura Härkönen

New bedding site examination-based method to analyse deer ked (Lipoptena cervi) infection in cervids

Invasion of the deer ked (Lipoptena cervi), an ectoparasitic fly commonly found in cervids, has been rapid in Finland during the last four decades. As the distribution area of this species has expanded from the south towards the northern latitudes, the associated problems have become more evident. Various animals such as horses, cattle and especially reindeer have been reported to host this parasite. Moreover, in certain areas, the deer ked causes major inconveniences for humans potentially limiting recreational activities in forests. We wanted to study if deer ked parasitism and intensity of the infection in winter time could be detected by using visual examination of the snow on cervid bedding sites and by analysing biotic samples found from the bedding sites. Our results demonstrate that chronic deer ked infection causes reddish-brown snow discolouration (host tissue fluid and deer ked faeces) on the bedding sites to the extent that parasitism can be diagnosed. Hence, we suggest that deer ked infection prevalence and range expansion could be rapidly monitored using our new practical and reliable method. In the future, bedding site analyses will likely be useful in predicting and potentially preventing the negative effects of this ecologically and socio-economically important parasite.

Experiments on the ectoparasitic deer ked that often attacks humans; preferences for body parts, colour and temperature.

The deer ked (Lipoptena cervi) can fail in its host search. Host search fails when an individual deer ked irreversibly accepts a host unsuitable for its reproduction (e.g. a human) and drops its wings. In northern Europe, the main host of the deer ked is the moose (Alces alces). The deer ked is increasingly causing serious problems for humans (for example, causing deer ked dermatitis) and is considered a threat for the recreational use of forests. The adult deer ked flies in early and mid-autumn to search for a host. Our aims were: (i) to study whether there are ways to avoid deer ked attacks by wearing particular clothing, and (ii) to evaluate deer ked host choice. Using human targets, we explored the cues the deer ked uses for host selection. We studied which part of the host body deer keds target and if body colour and temperature affect their choice. In our experiments, deer keds landed more on dark and red clothing than on white clothing. Moreover, deer keds mostly attacked the upper body parts and preferred the back side of the body over the front side. Finally, deer keds preferred the warmest areas of the host.

Geographical variation in host use of a blood-feeding ectoparasitic fly: implications for population invasiveness

Invasive generalist ectoparasites provide a tool to study factors affecting expansion rates. An increase in the number of host species may facilitate geographic range expansion by increasing the number of suitable habitats and by affecting local extinction and colonization rates. A geographic perspective on parasite host specificity and its implications on range expansion are, however, insufficiently understood. We conducted a field study to explore if divergent host specificity could explain the observed variation in expansion rates between Fennoscandian populations of the deer ked (Lipoptena cervi), which is a blood-feeding ectoparasitic fly of cervids. We found that the rapidly expanding eastern population in Finland appears to specialize on moose, whereas the slowly expanding western population in Norway breeds successfully on both moose and roe deer. The eastern population was also found to utilize the wild forest reindeer as an auxiliary host, but this species is apparently of low value for L. cervi in terms of adult maintenance, reproductive output and offspring quality. Abundant numbers of roe deer and white-tailed deer were observed to be apparently uninfected in Finland, suggesting that host use is not a plastic response to host availability, but rather a consequence of population-level evolutionary changes. Locally compatible hosts were found to be the ones sharing a long history with the deer ked in the area. Cervids that sustained adult deer keds also allowed successful reproduction. Thus, host use is probably determined by the ability of the adult to exploit particular host species. We conclude that a wide host range alone does not account for the high expansion rate or wide geographic distribution of the deer ked, although loose ecological requirements would increase habitat availability.

Behavioural variation in Eurasian perch populations with respect to relative catchability

Animal personalities, i.e. consistent individual differences in behaviour, are currently of high interest among behavioural and evolutionary biologists. The topic has received increasing attention also in fisheries science because selective harvesting of certain behavioural types might impose fishing-induced selection on personality. Here, we ice-fished wild Eurasian perch (Perca fluviatilis) from three native populations and investigated whether differences in relative catchability would explain behavioural differences observed in experimental conditions. We inferred relative catchability differences indirectly by fishing each location first with generally inefficient artificial bait and then by more efficient natural bait. The captured, individually tagged fish were tested in groups for their exploration tendency, activity and boldness under authentic predation risk in semi-natural stream channels. Fish that were easily captured first with artificial bait expressed fast exploration and acute activity, whereas the fish captured with natural bait showed less active and explorative behaviour. Differences in relative catchability did not explain variation in boldness or body size. In conclusion, we found that (1) Eurasian perch differing in relative catchability differ in certain behavioural traits, (2) fast explorers are more common among fish that get easily caught compared to fish that are more difficult to catch, (3) relative catchability explains more behavioural variation in a novel environment than in a familiar one and (4) selectivity of recreational angling on fish behaviour may depend on applied angling method and the effort spent on each location.

Threat of An Invasive Parasitic Fly, the Deer Ked (Lipoptena cervi), to the Reindeer (Rangifer Tarandus Tarandus): Experimental Infection and Treatment

Range expansion of ectoparasites can cause parasites to attack new host species. In these cases it is important for the parasite to be able to adapt to the new environment and to reproduce on the host. For the host, it is crucial to hinder successfully the development of long-lasting parasitic relationship. The deer ked (Lipoptena cervi) is a novel ectoparasite for northern cervids. We investigated if the deer ked can use the reindeer (Rangifer tarandus) as a host and, if it can, whether antiparasitic treatment against this parasite would be available. Three groups of reindeer were monitored: two groups of 6 reindeer were infected with 300 flies per each individual; a control group comprised 6 animals. One of the infected groups was treated with subcutaneous ivermectin. At the end of the experiment the infestation rate of the infected animals was low. The reindeer in the non-treated group had both live and dead deer keds and also a single pupa while the ivermectin-treated reindeer had only dead deer keds. As some deer keds survived and reproduced, the deer ked can potentially use the reindeer as a host but antiparasitic treatment may be effective against this parasite.

Molecular detection of Bartonella spp. in deer ked pupae, adult keds and moose blood in Finland

The deer ked (Lipoptena cervi) is a haematophagous ectoparasite of cervids that harbours haemotrophic Bartonella. A prerequisite for the vector competence of the deer ked is the vertical transmission of the pathogen from the mother to its progeny and transstadial transmission from pupa to winged adult. We screened 1154 pupae and 59 pools of winged adult deer keds from different areas in Finland for Bartonella DNA using PCR. Altogether 13 pupa samples and one winged adult deer ked were positive for the presence of Bartonella DNA. The amplified sequences were closely related to either B. schoenbuchensis or B. bovis. The same lineages were identified in eight blood samples collected from free-ranging moose. This is the first demonstration of Bartonella spp. DNA in a winged adult deer ked and, thus, evidence for potential transstadial transmission of Bartonella spp. in the species.

High cold tolerance through four seasons and all free-living stages in an ectoparasite

Off-host stages of temperate parasites must cope with low temperatures. Cold tolerance is often highest in winter, as a result of diapause and cold acclimation, and low during the active summer stages. In some blood-feeding ectoparasites, offspring provisioning determines cold tolerance through all the non-feeding, off-host stages. Large size increases survival in the cold, but so far seasonal variation in within-female offspring size has not been associated with offspring cold tolerance. The deer ked (Lipoptena cervi) reproduces on cervids from autumn to spring. Newborn pupae drop off the host, facing frosts without any acclimation. We examined cold tolerance through 4 seasons and from birth to adulthood by means of short- and long-term frost exposure. We expected females to produce more tolerant offspring in winter than in spring. Large spring pupae survived prolonged frosts better than did small winter pupae. Thus more tolerant offspring were not produced when the temperature outside the host is at its lowest. Unexpectedly, the freezing points were -20 °C or below all year round. We showed that high cold tolerance is possible without acclimation regardless of life stage, which presumably correlates with other survival characteristics, such as the starvation resistance of free-living ectoparasites.

Northward invasion of the parasitic deer ked (Lipoptena cervi), is there geographical variation in pupal size and development duration?

The deer ked (Lipoptena cervi) is a common ectoparasite of cervids. During the last decades the species has rapidly invaded in northern Europe, especially in Finland, towards the north and increased its prevalence on the moose population. Consequently, during this rapid invasion the deer ked has faced more severe climatic conditions. We studied whether pupal size (measured as pupal weight) and pupal development duration of the deer ked varies along historical invasion zones and temperature zones towards north in Finland. Moreover, we explored possible size- and gender-dependent variation in pupal development duration. We divided wild-collected pupae in respect to their origin in two ways: (1) temperature zones (from south-west to colder north-east) and (2) invasion history (from early to late establishment). We reared pupae in the controlled laboratory conditions in identical temperature and light conditions. Pupal size decreased towards north and the smaller pupae developed faster. However, the results do not show differences in pupal size or developmental characteristics between the invasion zones. This supports the idea of rapid developmental plasticity of the deer ked and that not the invasion history but the current temperature regime determines the life history of the deer ked when invading towards a colder environment.

Experimental infection of the deer ked (Lipoptena cervi) has no negative effects on the physiology of the captive reindeer (Rangifer tarandus tarandus)

The deer ked (Lipoptena cervi) is a haematophagous parasitic fly of cervids that spread to Finland in the early 1960s. Presently its northern distribution limit lies at approximately 65°N and it is gradually spreading northwards. In Finland the principal host species has been the moose (Alces alces), but the deer ked is about to establish contact with another potential host, the semi-domesticated reindeer (Rangifer tarandus tarandus) causing possible threats to reindeer health and management. The aim of this study was to investigate if the deer ked would have an influence on the welfare of the reindeer. Eighteen adult reindeer were divided into three experimental groups: the control group and two infected groups with 300 deer keds per reindeer introduced in August-September. One of the infected groups was treated with subcutaneous ivermectin in November. To gather comprehensive data on potential health hazards caused by the deer ked a wide array of physiological variables was measured during and at the end of the experiment in December. The keds caused no clear changes in the complete blood count, plasma clinical chemistry, amino acids, endocrinology, energy stores, enzyme activities or tissue fatty acid profiles of the host. The haematological, clinical chemical and endocrinological values displayed changes that could be related to the seasonal physiological adaptations of the species. In conclusion, at the duration and intensity of infection that were employed, the effects of the deer ked on the measured physiological variables of the reindeer were insignificant.

Unexpected seasonal variation in offspring size and performance in a viviparous ectoparasite.

Offspring size and performance in invertebrates often decrease with maternal age or as a response to seasonal environment. In viviparous ectoparasites maternal provision may wholly determine offspring performance outside the host. The viviparous deer ked (Lipoptena cervi), an ectoparasite of cervids, breeds from autumn to spring. We reared deer ked pupae through the reproductive period to investigate whether offspring size and performance vary according to maternal age and offspring environment. We expected that, in autumn, young females would produce the largest offspring to ensure that early-born pupae would survive a long period of winter diapause, and that offspring size would decrease with maternal age and decreasing diapause length. Diapause was associated with a significant weight loss, which reduced survival through post-diapause development. It was thus surprising that the early-born offspring were the smallest, and that size and survival (eventually) increased towards the spring. The variability among offspring in the length of off-host period seems to be an important component of life-history evolution in this ectoparasite, and should be studied further. Unexpected seasonal variation in the offspring size of this blood-feeding ectoparasite may result from changes in female resources due to weakening host condition as the winter progresses.