Sauli Laaksonen

Climate Change Promotes the Emergence of Serious Disease Outbreaks of Filarioid Nematodes

Filarioid parasites represent major health hazards with important medical, veterinary, and economic implications, and considerable potential to affect the everyday lives of tens of millions of people globally (World Health Organization, 2007). Scenarios for climate change vary latitudinally and regionally and involve direct and indirect linkages for increasing temperature and the dissemination, amplification, and invasiveness of vector-borne parasites. High latitude regions are especially influenced by global climate change and thus may be prone to altered associations and dynamics for complex host-pathogen assemblages and emergence of disease with cascading effects on ecosystem structure. Although the potential for substantial ecological perturbation has been identified, few empirical observations have emanated from systems across the Holarctic. Coincidental with decades of warming, and anomalies of high temperature and humidity in the sub-Arctic region of Fennoscandia, the mosquito-borne filarioid nematode Setaria tundra is now associated with emerging epidemic disease resulting in substantial morbidity and mortality for reindeer and moose. We describe a host-parasite system that involves reindeer, arthropods, and nematodes, which may contribute as a factor to ongoing declines documented for this ungulate species across northern ecosystems. We demonstrate that mean summer temperatures exceeding 14°C drive the emergence of disease due to S. tundra. An association between climate and emergence of filarioid parasites is a challenge to ecosystem services with direct effects on public health, sustainability of free-ranging and domestic ungulates, and ultimately food security for subsistence cultures at high latitudes.

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.

Taenia arctos n. sp. (Cestoda: Cyclophyllidea: Taeniidae) from its definitive (brown bear Ursus arctos Linnaeus) and intermediate (moose/elk Alces spp.) hosts

Taenia arctos n. sp. (Cestoda: Cyclophyllidea: Taeniidae) is described from the brown bear Ursus arctos Linnaeus (definitive host) and moose/elk Alces spp. (intermediate hosts) from Finland (type-locality) and Alaska, USA. The independent status of the new species and the conspecificity of its adults and metacestodes have been recently confirmed by the mtDNA sequence data of Lavikainen et al. (2011; Parasitology International, 60, 289–295). Special reference is given to morphological differences between the new species and T. krabbei Moniez, 1879 (definitive hosts primarily canines for the latter), both of which use the moose/elk (Alces spp.) as intermediate hosts (the latter also uses Rangifer and perhaps other northern ruminants), and between the new species and T. ursina Linstow, 1893, both of which use the brown bear U. arctos as a definitive host. New morphological data are also provided for adults and cysticerci of T. krabbei. The analysis includes potentially useful morphometric features that have not been previously applied to Taenia spp.

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.

A new type F Wolbachia from Splendidofilariinae (Onchocercidae) supports the recent emergence of this supergroup.

Wolbachia are vertically transmitted endosymbiotic bacteria of arthropods and onchocercid nematodes. It is commonly accepted that they co-evolved with their filarial hosts, and have secondarily been lost in some species. However, most of the data on the Wolbachia/Onchocercidae relationship have been derived from studies on two subfamilies, the Dirofilariinae and the Onchocercinae, which harbour parasites of humans and domestic animals. Within the last few years, analyses of more diverse material have suggested that some groups of Onchocercidae do not have Wolbachia, such as recently studied Splendidofilariinae from birds. This study takes advantage of the analysis of additional Splendidofilariinae, Rumenfilaria andersoni from a Finnish reindeer and Madathamugadia hiepei from a South African gecko, using PCR, immunohistochemical staining and whole-mount fluorescent analysis to detect Wolbachia and describe its strains. A DNA barcoding approach and phylogenetic analyses were used to investigate the symbiosis between Wolbachia and the Onchocercidae. A new supergroup F Wolbachia was demonstrated in M. hiepei, representing the first filarial nematode harbouring Wolbachia described in a non-mammalian host. In the adult, Wolbachia infects the female germline but not the hypodermis, and intestinal cells are also infected. The phylogenetic analyses confirmed a recent emergence of supergroup F. They also suggested several events of horizontal transmission between nematodes and arthropods in this supergroup, and the existence of different metabolic interactions between the filarial nematodes and their symbionts.

Molecular identification of Taenia spp. in wolves (Canis lupus), brown bears (Ursus arctos) and cervids from North Europe and Alaska

Taenia tapeworms of Finnish and Swedish wolves (Canis lupus) and Finnish brown bears (Ursus arctos), and muscle cysticerci of Svalbard reindeer (Rangifer tarandus platyrhynchus), Alaskan Grants caribou (Rangifer tarandus granti) and Alaskan moose (Alces americanus) were identified on the basis of the nucleotide sequence of a 396 bp region of the mitochondrial cytochrome c oxidase subunit 1 gene. Two species were found from wolves: Taenia hydatigena and Taenia krabbei. The cysticerci of reindeer, caribou and one moose also represented T. krabbei. Most of the cysticercal specimens from Alaskan moose, however, belonged to an unknown T. krabbei-like species, which had been reported previously from Eurasian elks (Alces alces) from Finland. Strobilate stages from two bears belonged to this species as well. The present results suggest that this novel Taenia sp. has a Holarctic distribution and uses Alces spp. as intermediate and ursids as final hosts.

Mitochondrial DNA data reveal cryptic species within Taenia krabbei.

Cysticerci of Taenia sp. from two elks (Alces alces) in Finland were characterized using morphological criteria and sequences of two mitochondrial DNA regions. The host species, size, structure and location of the cysticerci indicated that they might belong to Taenia krabbei, a circumpolar species occurring in a sylvatic life cycle in wild canids and cervids. Based on the number, length and shape of the rostellar hooks, the specimens could not be unambiguously defined as belonging to T. krabbei, T. cervi, T. ovis or T. solium. In the phylogenetic analysis, based on mitochondrial nucleotide sequence data, Taenia sp. was placed as a sister species of T. solium, distant from T. krabbei isolates previously characterized from Svalbard. This indicates that the Finnish and the Svalbard isolates, resembling T. krabbei, cannot represent a single species. The results suggest that careful morphological and genetic analyses of further isolates from intermediate and definitive hosts are required to define the taxonomic status of these two cryptic species.

Filarioid nematodes in cattle, sheep and horses in Finland

BackgroundIn autumn 2006, Finnish meat inspection data revealed lesions in tendons, muscles and ligaments of bovine hind legs leading to partial condemnation of carcasses. In gross pathological examination at Finnish Food Safety Authority Evira, Oulu (now Fish and Wildlife Health) Research Unit, Onchocerca sp. (Filarioidea; Onchocercidae) nematodes were detected in lesions. Due to this, a pilot study was made in order to find out what filarioid nematodes do occur in cattle, horses and sheep in Finland.MethodsVentral skin biopsies from 209 dairy cattle and 42 horses, as well as blood samples from 209 cattle, 146 horses and 193 sheep, were collected from different parts of Finland and examined for microfilariae. Visceral organs and other tissues from 33 cattle with parasitic lesions were studied histopathologically.ResultsOnchocerca sp. microfilariae (mf), 240 μm long, range 225–260 μm, 5.4 μm thick, were found in 37% of the skin biopsies of cattle. All blood samples from cattle, horses and sheep and skin biopsies from horses were negative for mf. Ventral skin microfilaria prevalence in cattle was higher in southern Finland than in the North (p = 0.001). Animal age and sampling time was not associated with mf prevalence. The infection was evenly distributed among young and older animals. Macroscopic lesions on tissues included greenish-grey discolouration and often oedema. In most of the lesions, small pale nodules were seen on the fasciae. Histopathologic examination of the samples revealed mild to intense infiltration with eosinophilic granulocytes and multifocal nodular lymphoplasmacytic aggregations were seen. In some samples, there were granulomatotic lesions with central necrotic tissue and cell detritus, surrounded by eosinophilic granulocytes, lympho-, plasma- and histiocytes and some multinucleated giant cells. Around living nematodes no or only weak inflammatory changes were observed.ConclusionOnchocerca sp. infection in cattle was found to be common in Finland, but the amount of pathological changes leading to condemnation of infected parts is low compared to the mf prevalence. Pronounced pathological changes are distinct but rare and mild changes are difficult to distinguish. No other filarioid nematodes were observed from the animals and it appears that horses and sheep may be free from filarioid nematodes in Finland.

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.

Efficacy of different treatment regimes against setariosis (Setaria tundra, Nematoda: Filarioidea) and associated peritonitis in reindeer

BackgroundWhen a severe peritonitis outbreak in semi-domesticated reindeer was noticed in 2003 in Finland, the concerned industry urged immediate preventive actions in order to avoid detrimental effects of S. tundra and further economical losses. A research programme was swiftly initiated to study S. tundra and its impact on the health and wellbeing of reindeer.MethodsThe ultimate aim of this study was to test the efficacy of different treatment regimes against S. tundra and associated peritonitis in reindeer. The timing of the trials was planned to be compatible with the annual rhythm of the reindeer management; (1) the treatment of calves in midsummer, during routine calf ear marking, with ivermectin injection prophylaxis and deltamethrin pour-on solution as a repellent against insect vectors, (2) the treatment of infected calves in early autumn with ivermectin injection, and (3) ivermectin treatment of breeding reindeer in winter. The results were assessed using the post mortem inspection data and S. tundra detection. Finally, to evaluate on the population level the influence of the annual (late autumn-winter) ivermectin treatment of breeding reindeer on the transmission dynamics of S. tundra, a questionnaire survey was conducted.ResultsIn autumn, ivermectin treatment was efficient against peritonitis and in midsummer had a slight negative impact on the degree of peritonitis and positive on the fat layer, but deltamethrin had none. Ivermectin was efficient against adult S. tundra and its smf. All the reindeer herding cooperatives answered the questionnaire and it appeared that antiparasitic treatment of reindeer population was intense during the study period, when 64–90% of the animals were treated. In the southern part of the Finnish reindeer husbandry area, oral administration of ivermectin was commonly used.ConclusionAutumn, and to a lesser degree summer, treatment of reindeer calves with injectable ivermectin resulted in decreased severity of peritonitis and perihepatitis in reindeer calves due to setariosis. In the case of necessity for animal welfare reasons, treatment during early autumn round ups should be considered. On the population level, massive and routinely applied antiparasitic treatments can improve the health of breeding reindeer and decrease the mortality and the number of carriers but during the outbreak could not prevent its movement and expansion to the North.