Setaria tundra outbreak in reindeer in Finland

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Setaria tundra, yleistyvä porojen loinen : taudinpurkaus Suomen poroissa 2003–2006

Recent Finnish studies have revealed an array of filarioid nematodes and associated diseases that appear to be emerging in northern ungulates. All filarioid species produce microfilariae that are present in the host blood, and known vectors are haematophagous arthropods. Infections attributable to a species of the genus Setaria appear to have emerged in Scandinavian reindeer in 1973. The infections were associated with an outbreak of peritonitis. In the same year, tens of thousands of reindeer died in the northern part of the reindeer herding area of Finland. Severe peritonitis and large numbers of Setaria sp. worms were common findings. However, the prevalence of Setaria sp. in Scandinavian reindeer subsequently diminished. In Finland, the latest outbreak of peritonitis in reindeer started in 2003 in the southern and middle parts of the reindeer herding area. The proportion of reindeer viscera condemned due to parasitic lesions identified during meat inspections increased dramatically. These increases caused substantial economic losses and increased the workload associated with meat processing. The focus of the outbreak moved northward by approximately 100 km/yr, and by 2005 only the reindeer in Upper Lapland were free of lesions. During the same period, the peritonitis outbreak was apparently fading away in the southern area. The causative, agent based on morphological and molecular data, was identified as Setaria tundra. Reindeer calves with heavy infections of S. tundra expressed decreased thriftiness, poor body condition, and an undeveloped winter coat. Meat/post mortem inspection of diseased reindeer carcasses revealed ascites fluid, green fibrin deposits, adhesions, and live and dead S. tundra nematodes. Histopathology indicated granulomatous peritonitis with lymphoplasmacytic and eosinophilic infiltration. No specific bacterial growth was found. No significant impact on pH values of meat or on the organoleptic evaluation of meat was found. There was a significant positive correlation between worm counts and the degree of peritonitis, and a negative correlation between the degree of peritonitis and the back-fat layer. Based on the evidence in both ante and post mortem inspections and histological examinations, present studies and historical data indicate that S. tundra can act as a significant pathogen in reindeer. The prevalence and density of Setaria microfilariae (smf)in blood circulation were higher in reindeer calves than in adults; the overall prevalence was 42%. In order to monitor the dynamics of S. tundra in nature, wild cervids also were sampled. The overall smf prevalences for moose, wild forest reindeer and roe deer were 1.4-1.8%, 23% and 44%, respectively. The focus of microfilaremia in reindeer moved north while simultaneously declining in the south as the observed peritonitis outbreak decreased. Experimentally, in reindeer calves infected in their first summer of life the peak microfilaremia was recorded in their second summer. Captive reindeer were smf positive throughout the year, but smf disappeared from the blood after 2 years. The prepatent period of S. tundra was estimated to be about 4 months, with a life span of at least 14 months. Moose are apparently not a suitable reservoir host for the S. tundra haplotype occurring in reindeer. The previous report of a peritonitis outbreak in moose associated with Setaria sp. nematodes in Finnish Lapland in 1989 was caused by another S. tundra haplotype. It may well be that among other factors, the high percentage of wild forest reindeer with signs of peritonitis caused by S. tundra may also have contributed to a substantial population decline for this herd in Kainuu (1700 to 1000 in 2001-2005). Although S. tundra is at present maintained primarily in the reindeer population, roe deer seem to be a suitable host and asymptomatic carrier. Mosquitoes, particularly Aedes spp. and to a lesser extent Anopheles spp., play an important role in the transmission of S. tundra in reindeer herding areas in Finland. The prevalence of S. tundra larvae in naturally infected Finnish mosquitoes varied from 0.5-2.5%. The rate of development in mosquitoes is temperature-dependent. The life cycle of Setaria tundra; Adult nematodes inhabit the peritoneal cavity of reindeer and produce microfilariae in to the host’s blood circulation, especially on summer months. The life span of the adult S. tundra female is at least 14 months.Microfilariae get with the blood meal into the intermediate mosquito (Culicidae) host. Microfilariae penetrate the gut of the mosquito and develop through two moults into infective third-stage larvae. The development is temperature dependent and takes about two weeks at 21°C (mean). When the mosquito is feeding again, the third-stage larvae break out and penetrate the skin of the host through mosquito’s puncture wound. Then they develop to the adult stage through two moults in the host and find their way to the abdominal cavity. The prepatent time is approximately 4 months. Ivermectin has good efficacy against adult S. tundra nematodes and circulating smf, and therefore there is an obligation to treat heavily infected reindeer calves with ivermectin by injection for animal welfare reasons. At the population level, massive antiparasitic treatment with ivermectin can reduce the number of carriers among reindeer population. The fact that this could not prevent the emergence of the S. tundra outbreak in new areas in the North indicates that the transmission dynamics of S. tundra are efficient. The 1973 outbreak of S. tundra in Sweden was associated with unusually warm weather and abnormally high numbers of mosquitoes and gnats. The summers of 1972 and 1973 in Finland were also very warm, as were those in 2002 and 2003. Warm summers apparently promote transmission and the genesis of disease outbreaks by favouring the development of S. tundra in its mosquito vectors, by improving the rate of mosquito development and reducing their mortality from frost, and finally, by forcing reindeer to stay in herds on mosquito-rich wetlands. Mosquito-borne diseases are among those most sensitive to weather and obviously will be influenced by climate change. Thus, I predict that global climate change will promote the further emergence of filarioid nematodes and diseases caused by them in the subarctic ecosystem. Moreover, I believe that future outbreaks can be predicted based on the mean temperatures of two consecutive summers. This study indicated that S. tundra probably has an important impact on boreal ecosystems. It also revealed the absence of baseline knowledge concerning temporal parasitic biodiversity in cervids at high latitudes. Therefore, it is important to gain knowledge about these parasites, their ecology, transmission dynamics, and their impact on human and animal health. The putative relationship between climate change and a vector-borne disease identified in this thesis indicates the potential and obvious threats to the individual and population health of arctic ungulates.Setaria tundra, yleistyvä porojen loinen; taudinpurkaus Suomen poroissa 2003–2006 Tiivistelmä Hyönteisvälitteinen sukkulamato, Setaria tundra aiheutti laajan ja nopeasti levinneen joukkosairastumisen poroilla vuosina 2003–05. Loinen kuuluu Filarioidea –heimoon, joka on maailmanlaajuisesti merkittävä, kymmenien miljoonien ihmisten ja eläinten terveyteen vaikuttava loisryhmä. Väitöskirjatutkimus käsittelee S. tundra –loisen aiheuttamia vaikutuksia poron ja hirvieläinten terveyteen yksilö- ja populaatiotasolla, viimeisimmän ja aikaisemmin Skandinaviassa tapahtuneiden epidemioiden pohjalta, loisen rakenteellista ja geneettistä tunnistamista ja tartunnan diagnosointia. Väitöskirja selvittää loisen elinkierron pohjoisessa luonnossa ja epidemian syntyyn myötävaikuttaneita tekijöitä, loisen isäntäeläimet, mahdolliset kantajat luonnonvaraisissa hirvieläimissä sekä välittäjähyönteiset. Myös mahdollisiin loisen vastustamiskeinoihin porotaloudessa esitetään ratkaisumalleja. Tutkimus osoittaa loisen yleistymisen ja kohonneen kesälämpötilan välisen yhteyden, joiden havaintojen perusteella pohditaan ilmaston muutoksen mahdollisia vaikutuksia hirvieläinpopulaatioihin, niistä riippuvaisiin alkuperäiselinkeinoihin ja elintarviketuotantoon pohjoisissa ekosysteemeissä. Filarioidea -sukkulamatoheimo Filarioidea – heimon loiset ovat yleismaailmallisia loisia joilla on suuri vaikutus ihmisten ja eläinten terveyteen, varsinkin maapallon lämpimillä vyöhykkeillä. Viimevuosien sekä nauta- että poroteurastamoissa tehdyt havainnot viittaavat hyönteisvälitteisten sukkulamatojen (Filarioidea) ja niiden aiheuttamien muutosten yleistymiseen myös Suomessa. Filarioidea-sukkulamadot asuvat isäntäeläimen kudoksissa tai ruumiinonteloissa ja tuottavat toukkia (mikrofilaria) isäntäeläimen ihoon tai verenkiertoon. Loisten väli-isäntinä ja aktiivisina vektoreina toimivat verta imevät niveljalkaiset. Setaria -suku Setaria (Onchocercidae) – suvun loiset ovat sorkka ja kavioeläinten loisia. Sukuun kuulu 43 lajia jotka asuvat normaalisti isäntäeläimen vatsaontelossa ja tuottavat mikrofilarioita verenkiertoon. Tunnetut vektorit ovat verta imeviä hyönteisiä. Setraia tundra –loisen historia Suomessa Ensimmäiset kirjatut havainnot Setaria – loisista poroilla tehtiin Skandinaviassa 1970-luvun alussa. Loisten massaesiintyminen yhdistettiin Ruotsissa ja Norjassa 1973 esiintyneeseen porojen vatsakaIvontulehdusepidemiaan. Samana vuonna Suomessa kuoli kymmeniä tuhansia poroja jolloin yleisinä ruumiinavauslöydöksinä oli voimakas vatsakalvon tulehdus ja suuri määrä Setaria – loisia vatsaontelossa. Tämän jälkeen Setaria – loiseen yhdistetyt muutokset sekä havainnot loisesta laskivat Suomen poroilla lähes huomaamattomiksi satunnaislöydöksiksi aina 30 vuoden ajaksi. Vatsakalvontulehdusepidemia Vuonna 2003 syksyllä poroteurastuskauden alussa kiiri hälyttäviä raportteja eteläisen- ja keskisen poronhoitoalueen poroteurastamoista poron vasoilla yleisesti esiintyvästä voimakkaasta vatsakalvontulehduksesta ja loisten massaesiintymisestä vatsaontelossa. Vasojen elinten ja vatsakalvojen hylkäämiset lihantarkastuksessa loismuutosten takia kasvoivat voimakkaasti, epidemia oli syntynyt. Epidemia aiheutti tuntuvia taloudellisia tappioita ja lisääntynyttä työtaakkaa poroteurastamoilla. Epidemian keskus siirtyi noin 100km:n vuosivauhtia pohjoista kohti, niin että vuonna 2005 vain Ylä-Lapin porot olivat vapaita loismuutoksista. Samaan aikaan epidemia laantui sen syntysijoilla, poronhoitoalueen eteläisissä osissa. Taudin aiheuttajaksi osoittautui loisen sekä rakenteellisten että geneettisten ominaisuuksien perusteella Setaria tundra. S. tundra –tartunnan oireet ja löydökset Vasojen olemus, joilla oli voimakas S. tundra – tartunta, ilmensi alentunutta kuntoa ja niiden talvikarva oli huonosti kehittynyt. Yleiset lihantarkastuslöydökset olivat lisääntynyt oljen tai veren värinen, vihertäviä partikkeleita sisältävä neste vatsaontelossa, vihertävää tai kellertävää saostumaa herakalvoilla ja sidekudoskiinnikkeitä vatsakalvon ja eri elinten välillä sekä eläviä 3 – 8 cm:n mittaisia valkeita sukkulamatoja sekä joskus kuolleita eri hajoamisvaiheissa olevia loisia. Histopatologiset tutkimukset vahvistivat muutokset loisten aiheuttamiksi; lympfoplasmosyyttinen ja eosinofiilinen tulehdussolureaktio ja –kertymä. Vaikka tulehdusreaktio näytti usein hyvin märkämäiseltä, ei mitään spesifistä bakteerikasvustoa havaittu. Vatsakalvon tulehdus ei myöskään aiheuttanut merkittäviä muutoksia lihan pH – arvoihin tai aistinvaraiseen laatuun. Mitä suurempi oli loisten lukumäärä vatsaontelossa, sen vakavampiasteinen oli myös tulehdusreaktio. Tulehdusreaktion voimistuminen vastaavasti pienensi poron kunnon mittarina käytettyä selän rasvakerroksen paksuutta. Aikuisilla poroilla esiintyi myös yleisesti S. tundra – tartuntaa, mutta vatsakalvon tulehdusta esiintyi erittäin harvoin. Kokonaisuudessaan tehdyt tutkimukset vahvistivat sen käsityksen, että S. tundra - infektio on vahingollinen poron vasojen terveydelle. Mikrofilariat verenkierrossa Kuten vatsakalvon tulehduskin, oli myös S. tundra – loisen mikrofilarioiden yleisyys ja tiheys poron vasojen verenkierrossa merkittävästi suurempi kuin aikuisten porojen. Myös mikrofilarioiden esiintyvyyden vaihtelu kuvasti epidemian liikettä pohjoiseen, etelässä infektoituneiden porojen määrä pieneni samalla kun teurastamoilla havaittujen tulehdusreaktioiden määrä laski. Mikrofilariat ilmestyivät luonnollisesti infektoituneiden poronvasojen verenkiertoon marras-jolukuulla. Mikrofilariamäärät olivat suurimmillaan seuraavana kesänä jolloin suurimmat tiheydet olivat lähes 4000 kpl/ml verta. Tämän jälkeen mikrofilariat hävisivät verenkierrosta vuoden kuluessa. Loisen aikuistumiseen porossa kuluu noin 4 kuukautta ja elinikä on ainakin 14 kuukautta. Setaria tundra luonnonvaraisissa hirvieläimissä Loisen isäntien ja luonnon reservoaarien selvittämiseksi kerättiin verinäytteitä myös luonnonvaraisista hirvieläimistä. Kun poron koko populaation S. tundra – infektioprosentti oli 42% oli se metsäpeuralla 23%, hirvellä 1.4-1.8% ja metsäkauriilla 44%. Tutkimuksen perusteella metsäpeura sekä metsäkauris voivat toimia loisen luonnollisina oireettomina kantajina ja levittäjinä. Metsäpeuralla havaittu samanaikainen korkea vatsakalvontulehduksen esiintyminen herättää myös kysymyksiä mahdollisesta yhteydestä Kainuun metsäpeurapopulaation lähes samanaikaiseen jyrkkään vähenemiseen. Hirven osuus porojen epidemian tämänkertaisessa synnyssä ei ole todennäköinen. Vuoden 1989 S. tundra – massaesiintymä hirvellä oli loisen eri haplotyypin aiheuttama. Hyönteisvektorit Hyttynen, etenkin Aedes –suku on S. tundra –loisen tärkein väli-isäntä ja vektori Suomessa. Epidemian aikana 0,5-2,5% luonnonvaraisista hyttysistä olivat loisen kantajia. Hyttysen veriaterian mukana saaman mikrofilarian kehitys infektiokykyiseksi toukaksi kestää noin kaksi viikkoa. Kehityksen nopeuteen vaikuttaa ympäristön lämpötila niin että lämpö jouduttaa kehitystä. Ruotsissa 1973 S. tundra –loisen massaesiintymä yhdistettiin epätavallisen lämpimään ja kesään ja huomattavaan hyttysten runsauteen. Kesät 2002 ja 2003 olivat myös Suomessa erittäin lämpimiä. Tutkimustemme mukaan lämpimät kesät suosivat loisen elämänkiertoa ja mahdollisia taudinpurkauksia. Lämpö suosii itse hyttysen elinkiertoa ja vähentää pakkasten aiheuttamaa kuolleisuutta ja kiihdyttää loisen kehittymistä hyttysessä. Lisäksi lämmin sää saa porot tokkaantumaan hyttysrikkaille soille ja kosteikoille joissa loisen leviämismahdollisuudet ovat ihanteelliset. Setaria tundra –loisen elämänkierto Aikuiset loiset asuvat isäntäeläimen vatsaontelossa ja tuottavat mikrofilarioita sen verenkiertoon, erityisesti kesäkuukausina. Naaraspuolisen loisen elinikä on vähintään 14 kuukautta. Mikrofilariat kulkeutuvat veriaterian mukana väli-isäntänä toimivaan hyttyseen. Ne tunkeutuvat hyttysen suoliston seinämän läpi ja kehittyvät kahden nahanluonnin kautta infektiokykyisiksi kolmannen asteen toukiksi. Kehitysnopeus on lämpötilariippuvaista ja kestää 21 °C lämpötilassa noin kaksi viikkoa. Kun hyönteinen aterioi tämän jälkeen, toukat murtautuvat ulos ja tunkeutuvat uuteen isäntäeläimeen hyttysen pistohaavasta. Loinen kehittyy kahden nahanluonnin kautta sukukypsäksi noin neljässä kuukaudessa. Vastustaminen Valtaosa (n 80%) siitosporoistamme lääkitään vuosittain ivermektiini-loislääkkeellä. Ivermektiini-injektio osoittautui tehokkaaksi aikuisia poron vatsaontelossa olevia S. tundra –loisia ja verenkierrossa kiertäviä mikrofilarioita vastaan. Tämä antaa mahdollisuuden ja velvollisuuden hoitaa voimakkaasta infektiosta kärsiviä vasoja. Populaatiotasolla on mahdollista vähentää infektion kantajia siitosporoista ja näin ennaltaehkäistä taudinaiheuttajan siirtymistä vasoihin. Se, että laajasta ja intensiivisestä porojen loislääkityksestä huolimatta, epidemia levisi vääjäämättä pohjoiseen, osoittaa loisen erittäin tehokasta leviämiskykyä, jälkeläistuotantoa ja hyttysvektorin suurta tehokkuutta. Ilmasto ja sää Ilmasto- ja säätekijät vaikuttavat merkittävästi hyttysten levittämien sairauksien esiintyvyyteen ja leviämiseen. Siksi loisten esiintymiselle voi ilmastonmuutoksella olla arvaamattomat seuraukset Pohjolassa. Tutkimustulostemme mukaan S. tundra -loisen yleistyminen voidaan ennakoida kahden edeltävän kesän lämpötilan mukaan; 14 °C ylittävä kesän keskilämpötila on hälyttävä. On ilmeistä että ilmastonmuutos edesauttaa S. tundra- ja sen sukulaisloisten ja niiden mahdollisesti uusissa isäntäeläimissään aiheuttamien muutosten tai vahingollisten vaikutusten leviämistä subarktisiin ekosysteemeihin. Niillä voi olla ennalta arvaamattomia vaikutuksia eläinpopulaatioihin ja sitä kautta alueen elintarviketuotantoon, niistä riippuvaisiin yhteisöihin sekä ihmisten terveyteen. Tutkimus osoitti sen aukon, joka liittyy näiden, aikaisemmin lähinnä trooppisten alueiden ongelmina pidettyjen, hyönteisvälitteisten loisten tutkimukseen Pohjolassa. Jatkotutkimukset, jotka kohdistua hyönteisvälitteisten loisten ekologiaan, dynamiikkaan, tartuntateihin ja niiden seurantaan nisäkäspopulaatiossa ja vaikutuksiin sekä ihmisten että eläinten terveyteen, ovat välttämättömiä

Range expansion and reproduction of the ectoparasitic deer ked (Lipoptena cervi) in its novel host, the Arctic reindeer (Rangifer tarandus tarandus), in Finland

The deer ked (Lipoptena cervi) is a harmful ectoparasite that emerged in the reindeer herding area of Finland in 2006. To understand the current range and the intensity of infestations on its novel reindeer host, we studied deer ked pupae collected from reindeer and moose bedding sites and conducted a questionnaire survey among the managers of 18 reindeer herding cooperatives in the southern part of the reindeer herding area. Our study confirmed that the deer ked can survive and successfully reproduce on reindeer through winter and that flying deer keds had been observed in reindeer wintering areas during several autumns in twelve cooperatives. The pupae originating from reindeer were smaller and showed lower hatching rates than the pupae from moose. The present results indicate that the range of the deer ked infestations on reindeer in Finland expanded during the recent 5 years, now reaching 14 cooperatives and bordering an area south of approximately 66 degrees N 25 degrees E in the west and 65 degrees N 29 degrees E east.Peer reviewe

Wintertime pharmacokinetics of intravenously and orally administered meloxicam in semi-domesticated reindeer (Rangifer tarandus tarandus)

Objective To investigate the pharmacokinetics of orally and intravenously (IV) administered meloxicam in semi domesticated reindeer (Rangifer tarandus tarandus). Study design A crossover design with an 11 day washout period. Animals A total of eight young male reindeer, aged 1.5-2.5 years and weighing 74.3 +/- 6.3 kg, mean +/- standard deviation. Methods The reindeer were administered meloxicam (0.5 mg kg(-1) IV or orally). Blood samples were repeatedly collected from the jugular vein for up to 72 hours post administration. Plasma samples were analysed for meloxicam concentrations with ultraperformance liquid chromatography combined with triple quadrupole mass spectrometry. Noncompartmental analysis for determination of pharmacokinetic variables was performed. Results The pharmacokinetic values, median (range), were determined. Elimination half-life (t(1/2)) with the IV route (n = 4) was 15.2 (13.2-16.8) hours, the volume of distribution at steady state was 133 (113-151) mL kg(-1) and clearance was 3.98 (2.63-5.29) mL hour(-1) kg(-1). After oral administration (n = 7), the peak plasma concentration (C-max) was detected at 6 hours, t(1/2) was 19.3 (16.7-20.5) hours, C(max )1.82 (1.17-2.78) mu g mL(-1) and bioavailability (n = 3) 49 (46-73)%. No evident adverse effects were detected after either administration route. Conclusions and clinical relevance A single dose of meloxicam (0.5 mg kg(-1) IV or orally) has the potential to maintain the therapeutic concentration determined in other species for up to 3 days in reindeer plasma.Peer reviewe

Is transport distance correlated with animal welfare and carcass quality of reindeer (Rangifer tarandus tarandus)?

Background: Slaughter reindeer are exposed to stress caused by gathering, handling, loading and unloading, and by conditions in vehicles during transport. These stress factors can lead to compromised welfare and trauma such as bruises or fractures, aspiration of rumen content, and abnormal odour in carcasses, and causing condemnations in meat inspection and lower meat quality. We investigated the statistical association of slaughter transport distance with these indices using meat inspection data from years 2004-2016, including inspection of 669,738 reindeer originating from Finnish reindeer herding areas. Results: Increased stress and decreased welfare of reindeer, as indicated by higher incidence of carcass condemnation due to bruises or fractures, aspiration of rumen content, or abnormal odour, were positively associated with systems involving shorter transport distances to abattoirs. Significant differences in incidence of condemnations were also detected between abattoirs and reindeer herding cooperatives. Conclusions: This study indicates that in particular the short-distance transports of reindeer merit more attention. While the results suggest that factors associated with long distance transport, such as driver education, truck design, veterinary supervision, and specialist equipment, may be favourable to reducing pre-slaughter stress in reindeer when compared with short distance transport systems, which occur in a variety of vehicle types and may be done by untrained handlers. Further work is required to elucidate the causal factors to the current results.Peer reviewe

STATUS AND REVIEW OF THE VECTOR-BORNE NEMATODE SETARIA TUNDRA IN FINNISH CERVIDS

The filarioid nematode Setaria tundra caused an outbreak of peritonitis in Finnish semi-domesticated reindeer in 2003-2006. Our research group studied the invasion and reservoirs of S. tundra in Finnish cervid populations and this paper provides an overview of that research. The outbreak had detrimental effects on reindeer health and may, in part, explain the observed decline of the population of wild forest reindeer (Rangifer tarandus fennicus). Both range expansion by roe deer, and high summer temperatures that increased vector populations of mosquitoes and gnats and influenced habitat use by reindeer were implicated in the outbreak. We suggest that vector borne parasites will increase in the Arctic owing to the effect of global climate change and have consequences for all cervid populations

Vectors and transmission dynamics for Setaria tundra (Filarioidea;

Background: Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003–05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland Results: Development of S. tundra to the infective stage occurs in mosquitoes, (genera Aedes and Anopheles). We consider Aedes spp. the most important vectors. The prevalence of S. tundra naturally infected mosquitoes from Finland varied from 0.5 to 2.5%. The rate of development in mosquitoes was temperature-dependent. Infective larvae were present approximately 14 days after a blood meal in mosquitoes maintained at room temperature (mean 21 C), but did not develop in mosquitoes maintained outside for 22 days at a mean temperature of 14.1 C. The third-stage (infective) larvae were elongated (mean length 1411 m (SD 207), and width 28 m (SD 2)). The anterior end was blunt, and bore two liplike structures, the posterior end slight tapering with a prominent terminal papilla. Infective larvae were distributed anteriorly in the insect's body, the highest abundance being 70 larvae in one mosquito. A questionnaire survey revealed that the peak activity of Culicidae in the reindeer herding areas of Finland was from the middle of June to the end of July and that warm summer weather was associated with reindeer flocking behaviour on mosquito-rich wetlands. Conclusion: In the present work, S. tundra vectors and larval development were identified and described for the first time. Aedes spp. mosquitoes likely serve as the most important and competent vectors for S. tundra in Finland. Warm summers apparently promote transmission and genesis of disease outbreaks by favouring the development of S. tundra in its mosquito vectors, by improving the development and longevity of mosquitoes, and finally by forcing the reindeer to flock on mosquito rich wetlands. Thus we predict that global climate change has the potential to promote the further emergence of Filarioid nematodes and the disease caused by them in subarctic regions

Vectors and transmission dynamics for Setaria tundra (Filarioidea; Onchocercidae), a parasite of reindeer in Finland

Background: Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003–05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland Results: Development of S. tundra to the infective stage occurs in mosquitoes, (genera Aedes and Anopheles). We consider Aedes spp. the most important vectors. The prevalence of S. tundra naturally infected mosquitoes from Finland varied from 0.5 to 2.5%. The rate of development in mosquitoes was temperature-dependent. Infective larvae were present approximately 14 days after a blood meal in mosquitoes maintained at room temperature (mean 21 C), but did not develop in mosquitoes maintained outside for 22 days at a mean temperature of 14.1 C. The third-stage (infective) larvae were elongated (mean length 1411 m (SD 207), and width 28 m (SD 2)). The anterior end was blunt, and bore two liplike structures, the posterior end slight tapering with a prominent terminal papilla. Infective larvae were distributed anteriorly in the insect's body, the highest abundance being 70 larvae in one mosquito. A questionnaire survey revealed that the peak activity of Culicidae in the reindeer herding areas of Finland was from the middle of June to the end of July and that warm summer weather was associated with reindeer flocking behaviour on mosquito-rich wetlands. Conclusion: In the present work, S. tundra vectors and larval development were identified and described for the first time. Aedes spp. mosquitoes likely serve as the most important and competent vectors for S. tundra in Finland. Warm summers apparently promote transmission and genesis of disease outbreaks by favouring the development of S. tundra in its mosquito vectors, by improving the development and longevity of mosquitoes, and finally by forcing the reindeer to flock on mosquito rich wetlands. Thus we predict that global climate change has the potential to promote the further emergence of Filarioid nematodes and the disease caused by them in subarctic regions

Gastrointestinal parasites in reindeer (Rangifer tarandus tarandus) calves from Fennoscandia : An epidemiological study

Reindeer (Rangifer tarandus tarandus) host numerous parasites. Although there is a general knowledge about parasite diversity in reindeer, detailed baseline information about parasitic infections is limited. Detailed knowledge of parasite prevalence and diversity provide a pathway for more targeted parasite control, an increasing need expected in the future. The main aim of our cross-sectional study was to estimate the prevalence of gastrointestinal parasites in semidomesticated reindeer calves. The 480 reindeer calves included in our study were aged 6–7 months, originated from 9 reindeer herding cooperatives in Finland and 1 in Norway, and were slaughtered during September–November 2015 in 10 reindeer slaughterhouses. All the reindeer calves passed meat inspection, and the detected parasitic infections were subclinical. As the reindeer included in this study were young animals intended for slaughter, they had never been administrated any antiparasitic treatment. Assessments of gastrointestinal parasitism among these reindeer calves were based on fecal examination and morphological identification of coccidian oocysts or helminth eggs. Individual fecal samples collected from the rectum of each of the reindeer were examined using a modified McMaster method. Most (78.3%) of the reindeer calves had eggs or oocysts of at least one parasite species in their feces, and more than half (53.5%) had a mixed infection. Strongylid eggs were detected in 75.6%, Eimeria sp. oocysts in 50.6%, Moniezia sp. eggs in 28.1%, Nematodirus sp. eggs in 22.1%, Capillaria sp. eggs in 9.4%, and Trichuris sp. eggs in 0.6% of the samples. The prevalence of gastrointestinal parasites was similar or higher relative to previous estimates from the region; the proportion of reindeer calves shedding strongylid eggs and the proportion of reindeer calves shedding Moniezia sp. eggs had increased. Prevalence varied by geographical region, which may reflect different herding practices or environmental parameters. Higher reindeer density was a risk factor for testing positive for Eimeria sp. oocysts, and the odds of testing positive for Nematodirus sp. eggs were higher if a peroral route was used for antiparasitic treatment in the reindeer herding cooperative. The mean proportion of reindeer estimated to receive antiparasitic treatment in Finland was 86% in 2004–2005 and 91% in 2014–2015. During the historical time frames of current management practices, this routine annual antiparasitic treatment of breeding reindeer has not decreased the prevalence of gastrointestinal parasites in reindeer calves, which can be seen as sentinels or indicators of the infection pressure.Peer reviewe