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

Occurrence of faecal endoparasites in reindeer (Rangifer tarandus) in two grazing areas in northern Norway

Background

Semi-domesticated reindeer represent an important livestock industry and livelihood for a proportion of the human population in northern Fennoscandia. Reindeer husbandry is considered an extensive animal husbandry, where the animals are kept mostly on natural pastures, although sometimes kept in fenced areas for shorter periods. These reindeer may harbour a variety of parasites that may affect animal health and production. The relatively limited close contact between herds and owners gives limited opportunities for diagnosis and treatment of diseases in general. Furthermore, the effects of subclinical parasitism in livestock are commonly expressed as a reduction in productivity rather than clinical disease and mortality. Thus, specific knowledge of endoparasites and parasitic infections in these herds is scarce. This study investigated the occurrence of various endoparasites in reindeer by analysis of a total of 114 faecal samples from winter-slaughtered reindeer from two different grazing areas in Troms and Finnmark, Norway.

Results

Using a McMaster method, a Baermann technique, and a direct immunofluorescent antibody test, the following parasites were identified in the faecal samples with the occurrence data given as percentages: Strongylid eggs (62%), Nematodirinae spp. eggs (24%), Capillaria sp. eggs (42%) and Moniezia spp. eggs (17%), Dictyocaulus spp. larvae (14%) protostrongylid larvae (40%), Eimera spp. oocysts (23%), and Giardia duodenalis cysts (5%). Cryptosporidium oocysts were not detected. Parasite eggs, oocysts, and cysts were quantified.

Molecular analysis revealed G. duodenalis sub-assemblage AI, a potentially zoonotic genotype not previously reported in reindeer from this region. Morphological analyses of Eimeria oocysts identified two species, Eimeria mayeri and Eimeria rangiferis, and molecular analyses of the cytochrome C oxidase I (coi) gene and 18 s rRNA (18SSU) gene of Eimeria confirmed the presence of Eimeria species that are specific to reindeer.

Conclusions

A high prevalence, but low burden, of endoparasites was detected in samples from these semi-domesticated reindeer. The samples were collected during winter, when adult gastrointestinal parasites usually produce only low numbers of transmission stages. Therefore, together with the low number of samples, detailed and definitive conclusions regarding parasite status of semi-domesticated reindeer are avoided. Nevertheless, these data provide a snapshot overview of parasite occurrence in a semi-domesticated animal group vulnerable to the various environmental changes to which they are exposed.

Gastrointestinal parasites in reindeer (Rangifer tarandus tarandus): A review focusing on Fennoscandia

Reindeer (Rangifer tarandus tarandus) are known to host a wide variety of parasites, including those in the gastrointestinal system. Here, we review the current knowledge of the main gastrointestinal parasites of reindeer focusing on northern Fennoscandia, which comprises parts of Finland, Sweden, Norway and Russia. We explore both the historical baseline data for diversity and distribution and recent advancements in our understanding of parasite faunas in reindeer across this region. It is evident that the balance between reindeer and their gastrointestinal parasites, along with the potential for emergent disease in the changing world warrants careful monitoring and further studies.

First report of equine Setaria digitata (von Linstow 1906) infestation in Malaysia

The occurrence of Setaria digitata in a horse is reported for the first time in Malaysia. An 8-year-old Thoroughbred cross mare was referred to the University Veterinary Clinic with the primary complaint of corneal opacity and excessive eye discharge. After initial treatment with Terramycin eye ointment, corneal opacity cleared partially to reveal a moving thread-like cylindrical worm in the anterior chamber of the eye. The parasite was successfully removed surgically, and examination under the light microscope revealed that the isolated worm (length = 45 mm) was a 5th stage larva of S. digitata based on morphological criteria. Confirmation of the species of the worm was through molecular methods. The 12S rRNA gene was PCR-amplified, and the purified amplicon was directly sequenced. Phylogenetic analyses revealed that the isolated roundworm showed 100% sequence similarity with that of S. digitata in NCBI GenBank database (Accession no.: KY284626.1). This report is the first confirmed case of equine ocular setariasis by S. digitata in Malaysia. The current study provides evidence that S. digitata is an etiological agent of ocular infection and its presence in Malaysia.

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.

Screening of mosquitoes for filarioid helminths in urban areas in south western Poland-common patterns in European Setaria tundra xenomonitoring studies

In recent years, numerous studies screening mosquitoes for filarioid helminths (xenomonitoring) have been performed in Europe. The entomological monitoring of filarial nematode infections in mosquitoes by molecular xenomonitoring might serve as the measure of the rate at which humans and animals expose mosquitoes to microfilariae and the rate at which animals and humans are exposed to the bites of the infected mosquitoes. We hypothesized that combining the data obtained from molecular xenomonitoring and phenological studies of mosquitoes in the urban environment would provide insights into the transmission risk of filarial diseases. In our search for Dirofilaria spp.-infected mosquitoes, we have found Setaria tundra-infected ones instead, as in many other European studies. We have observed that cross-reactivity in PCR assays for Dirofilaria repens, Dirofilaria immitis, and S. tundra COI gene detection was the rule rather than the exception. S. tundra infections were mainly found in Aedes mosquitoes. The differences in the diurnal rhythm of Aedes and Culex mosquitoes did not seem a likely explanation for the lack of S. tundra infections in Culex mosquitoes. The similarity of S. tundra COI gene sequences found in Aedes vexans and Aedes caspius mosquitoes and in roe deer in many European studies, supported by data on Ae. vexans biology, suggested host preference as the most likely cause of the mosquito genus-biased infections. High diversity of the COI gene sequences isolated in the city of Wroclaw in south western Poland and the presence of identical or almost identical sequences in mosquitoes and roe deer across Europe suggests that S. tundra has been established in most of Europe for a very long time.

The annual, temporal and spatial pattern of Setaria tundra outbreaks in Finnish reindeer: a mechanistic transmission model approach

Background

In northern Finland (Lapland), reindeer are reared as semi-domesticated animals. The region has a short summer season of 2–3 months, yet reindeer are infected with the mosquito-borne filarioid parasite Setaria tundra. The infection causes peritonitis and perihepatitis, which cause significant economic losses due to reduced body weight of infected animals. The objective of this study was to: (i) describe the spatial and temporal pattern of outbreaks in three different areas across Finnish Lapland; and (ii) construct a temperature-driven mechanistic transmission model to quantify the potential role of temperature on intensity of S. tundra transmission in reindeer.

Methods

We developed a temperature-driven transmission model able to predict the number of S. tundra potentially transmitted from an infectious reindeer. We applied the model to the years 2004–2015, and compared the predictions to the proportion of reindeer whose livers were condemned due to S. tundra infection at the time of slaughter.

Results

The mean proportion of liver condemnation increased in reindeer slaughtered in late autumn/winter compared to earlier dates. The outbreaks were geographically clustered each year but there were no fixed foci where outbreaks occurred. Larger outbreaks were recorded in the southern regions of reindeer-herding areas compared to the central or northern parts of Lapland. Our model showed that temperatures never allowed for transmission of more than a single generation of S. tundra each season. In southern (Kuusamo) and central (Sodankylä) Lapland, our model predicted an increasing trend from 1979 to 2015 for both the duration of the effective transmission period of S. tundra (P < 0.001) and for the potential number of L3 S. tundra larvae being transmitted from an infectious reindeer (P < 0.001).

Conclusions

The effective transmission period for S. tundra in reindeer is very short in Lapland, but it increased over the period studied. Only one generation of S. tundra can be transmitted in one season among reindeer in Lapland. Increasing temperatures may facilitate a range expansion and increasing duration of effective transmission period for S. tundra.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3159-z) contains supplementary material, which is available to authorized users.

A lymphatic dwelling filarioid nematode, Rumenfilaria andersoni (Filarioidea; Splendidofilariinae), is an emerging parasite in Finnish cervids

BACKGROUND

Recent studies revealed expansion of filarioid nematodes into northern Finland. In addition to Setaria tundra, an abundant filarioid, Rumenfilaria andersoni, was found inhabiting the lymphatic vessels of reindeer. Our study explores the dynamics of the rapid geographic expansion of R. andersoni, defining prevalence and density of microfilariae among 4 new cervid host species in Finland while developing a context for host-parasite ecology in Fennoscandia and more broadly in the Arctic and boreal regions.

METHODS

Blood samples were evaluated for presence of microfilariae from 1576 semi-domesticated reindeer, 8 captive reindeer, and free-ranging cervids including 105 wild forest reindeer, 862 moose, 114 white tailed deer and 73 roe deer in 2003-2006 (-2010). Additionally, the prepatent period and the efficacy of ivermectin treatment were investigated.

RESULTS

Rumenfilaria andersoni was found to be a common and abundant parasite in reindeer (0-90%) and wild forest reindeer (41-100%). Also moose (0-12%), white-tailed deer (15-22%) and roe deer (3%) were revealed as definitive hosts. Ivermectin was not effective against adult parasites. The prepatent period was estimated to be about five months.

CONCLUSIONS

Rumenfilaria andersoni was identified in 3 endemic cervid species and the introduced white-tailed deer, all constituting previously unrecognized host species in the Palearctic. Among moose, the prevalence and intensity were substantially lower than levels observed among subspecies of reindeer. White-tailed deer had a relatively high prevalence and density of R. andersoni microfilariae (rmf), whereas our limited data for roe deer indicated that the nematode may not have been abundant. Density and prevalence of rmf in moose and white tailed deer suggests the nematode may be adapted to these species, and that these cervids may be among the primary hosts of R. andersoni and reservoirs for transmission in Finland. Our current data suggest that R. andersoni became established in Finland recently, coincidental with introduction of white-tailed deer from North America in 1935; subsequent invasion and emergence in the past 70-80 years appears driven by climate-related factors. An alternative hypothesis for a temporally deeper occurrence for R. andersoni in Fennoscandia, representing post-Pleistocene range expansion with moose tracking deglaciation, is not firmly supported.

The relative plasma availabilities of ivermectin in reindeer (Rangifer tarandus tarandus) following subcutaneous and two different oral formulation applications

Background

Overwintering (breeding) reindeer (Rangifer tarandus tarandus) are commonly treated with ivermectin against parasitic infestations once yearly in autumn-winter roundups. The only preparations registered to reindeer are those for subcutaneous injection. However, also oral extra-label ivermectin administration is used. Twenty-six, 8-month-old reindeer calves were randomly allocated into three groups. Group 1 (n = 9) received oral ivermectin mixture (Ivomec® vet mixt. 0.8 mg/ml, oral ovine liquid drench formulation), Group 2 (n = 9) oral ivermectin paste (Ivomec® vet 18.7 mg/g equine paste), and Group 3 (n = 8) subcutaneous injection of ivermectin (Ivomec® 10 mg/ml vet inj.), each group at a dose of 200 μg/kg body weight. Blood samples were collected at treatment and at days 1, 2, 3, 6, 9 and 16 post treatment. Plasma concentrations of ivermectin were determined by high-pressure liquid chromatography (HPLC) with fluorescence detection.

Results

The peak plasma concentration (C_max) was reached by 2 days after each treatment. The C_max and Area Under Curve (AUC) differed significantly between the groups: C_max was 30.2 ± 3.9, 14.9 ± 5.7 and 63.1 ± 13.1 ng/ml, and AUC_∞ was 2881 ± 462, 1299 ± 342 and 6718 ± 1620 ng*h/ml for groups 1, 2 and 3, respectively (mean ± standard deviation).

Conclusions

The differences in plasma concentrations of ivermectin are concomitant with earlier observed differences in antiparasitic efficacy, which discounts the use of the equine paste in reindeer in favour of the oral ovine liquid drench formulation, or preferably, the reindeer-registered subcutaneous injection formulation.

Infestation by Hypoderma tarandi in reindeer calves from northern Finland--prevalence and risk factors

Serum samples from 953 reindeer (Rangifer t. tarandus) calves-of-the-year from 21 reindeer herding co-operatives in Finland in slaughter season 2006/2007 were assayed for antibodies against Hypodermin C by an ELISA detecting IgG. Data on presence of Hypoderma tarandi larvae on 12,327 reindeer hides from 17 of the 21 herding co-operatives in slaughter season 2005/2006 were included for support. ELISA showed a seroprevalence of 60.9%, with no significant difference between females and males, and increase with latitude (southernmost and northernmost co-operatives examined, Pudasjärvi and Kaldoaivi, 11.8 and 100% of seropositives, respectively). The proportion of larva positive hides (range 0.5-60% per co-operative) was low compared to the proportion of seropositives. Also the proportion of larva positive hides increased with latitude. Our findings indicated that high latitude combined with open landscape, presence of low vegetation and high reindeer density provided more favorable conditions for sustaining of high degree of warble fly infestation, and furthermore, that any possible effect of ivermectin treatment on infestation rate was ruled out by the higher effect by the above factors.

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 degrees 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.