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.     

Freshwater liming

Operational liming of surface waters is part of Sweden and Norway's strategy to counteract freshwater acidification caused by air pollutants. Smaller scale liming efforts are performed as research or experimental programs in other countries. Yearly, approx. 300,000 tons of fine-grained limestone (CaCO₃) is spread in lakes and streams and on wetlands to raise the pH in surface water at a cost of approximately 40–50 million $US. The chemical target is set by the biological goals and objectives. A total of over 11,000 lakes and streams are treated on a continuing basis. Dose calculations consider pH, inorganic monomeric Al, dissolved organic matter and the necessary buffering. Lake liming, limedosers at streams and terrestrial liming are used. A mix of different liming techniques is often preferred to get an optimal result. The vast majority of changes are desirable and expected Undesirable effects may appear and damaged wetlands are probably the most serious ones. Cost-benefit analysis show that liming may be profitable for the society. Recovery of the systems can take up to 10–20 years. Liming will in the long run restore the ecosystems but will not make them identical to what may be the original ones. In some cases, complementary measures, e.g. facilitation of recolonization, are necessary to enhance recovery. Reduced emissions of acidifying pollutants according to signed protocols will decrease the need for liming, but still liming is needed for several decades in large regions to preserve biodiversity.     

Decrease in Acid Deposition - Recovery in Norwegian Waters

Concentrations of sulphate in precipitation in southern Norway have decreased by 50–60% from 1980–1999. This has caused a decrease in sulphate concentrations in lakes of 30–40% from 1986–1999. Nitrogen in precipitation has decreased slightly over the last 10-years. In lakewater there has also been a significant but slight decrease. Concentrations of non-marine base cations in precipitation have decreased by 40% from 1980–1999. In lakewater, non-marine base cation concentrations have been at about the same level the last 10 years. This indicates that acid deposition has decreased sufficiently such that the pool of exchangeable base cations in the soil is now being replenished. The acidification situation in lakes in Norway has thus shown a clear improvement over the last 8–10 years. pH, alkalinity and ANC (acid neutralising capacity) have all increased. Concentrations of inorganic (toxic) aluminium species have decreased. The trends in H⁺ and Alⁿ⁺ do not follow the relation expected if Alⁿ⁺ concentrations were governed solely by a single solid phase of Al(OH)₃.     

Prolonged persistence of fecally excreted ivermectin from reindeer in a sub-arctic environment

In December 2001 and 2002, feces from reindeer calves treated with ivermectin were distributed on plots established on two types of forested reindeer pasture in northern Finland. The ungrazed plots were on an enclosure that had been fenced to prevent reindeer access for the last 6 years. The grazed plots were on an area that had been heavily stocked by reindeer during the last 5 years. After enclosures had been established, reindeer and large wildlife were prevented from entering by a fence. Topsoil samples (feces, vegetation, and soil) were collected monthly during the summers of the following 2 years, over a period of from 25 to 95 weeks after deposition. The samples were analyzed for ivermectin using HPLC. Although ivermectin degradation rapidly took place during the first spring, considerable residual ivermectin could be measured throughout the sampling time, showing that ivermectin in feces on pasture may not be photodegraded as rapidly as previously believed. The results support the need for further environmental evaluation studies on the use of ivermectin to control reindeer parasites.     

Direct high-resolution genotyping of Toxoplasma gondii in arctic foxes (Vulpes lagopus) in the remote arctic Svalbard archipelago reveals widespread clonal Type II lineage

Characterization of Toxoplasma gondii genotypes in hosts living in remote, isolated regions is important for elucidating the population structure and transmission mode of this parasite. Herein, we report the results of direct genotyping of T. gondii in brain tissue of arctic foxes (Vulpes lagopus) from the remote, virtually cat-free, high arctic islands of Svalbard. DNA extracts from brains of 167 seropositive arctic foxes (including four cases of fatal toxoplasmosis) and 11 seronegative arctic foxes were genotyped at 10 loci (SAG1, SAG2, SAG3, BTUB, GRA6, L358, c22-8, c29-2, PK1, and Apico) using the polymerase chain reaction-restriction fragment length polymorphism method. Of the 167 samples from seropositive foxes (including toxoplasmosis cases), 31 were genotyped at all 10 loci and 24 were genotyped at four to nine loci. To ensure confidence in T. gondii strain genotyping, samples for which less than four loci were genotyped were not considered positive. None of the 11 samples from seronegative foxes was positive for the 10 markers. Of the 55 samples that genotyped positively, 46 were of the Type II strain, 7 were of the Type III strain, and 2 were of atypical T. gondii strains. Five representative samples of the three genotypes were sequenced at loci SAG2, SAG3, GRA6, PK1, and UPRT-1. The DNA sequences confirmed the genotyping results. This study shows that the archetype Type II T. gondii strain, which is most widely distributed in North America and Europe, also predominates in arctic foxes on the Svalbard archipelago. This suggests that the T. gondii at this location originate from continental Europe and that transmission may be mediated by migrating birds. This study highlights the significance of long-distance transport of T. gondii and demonstrates that high-resolution genotyping protocols are useful for direct genetic studies of T. gondii when isolation of live parasites is infeasible.     

Incidence of hybridization between Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in Ireland

The substantial growth of the farmed salmon industry in Europe since the 1970s has highlighted concerns regarding the genetic impact of escaped farmed salmon on wild salmonid stocks. High incidences of salmon × trout hybrids have been recorded in rivers situated near intensive salmon farming in Norway and Scotland, which may be indicative of a breakdown in reproductive isolation between salmon, Salmo salar L., and brown trout, Salmo trutta L. In the present study, salmonid fry and 0+ parr were collected from rivers in western Ireland. Allozyme and minisatellite DNA analysis were carried out on fry to determine the frequency of F1 hybrids from 10 rivers located within 38 km of salmon farms and three rivers at least 80 km from salmon farms. A total of 49 hybrids were recorded from 4135 salmonid fry (frequency = 1.2%). Mitochondrial DNA analysis showed that all hybrids arose from Atlantic salmon female × brown trout male crosses. Hybrid parr were recorded from one of the low-risk rivers (1.0%), but were present in seven out of the 10 catchments located within 38 km of salmon farms, with frequencies ranging from 0.7% to 3.1%. The results of the present survey, which represents the first extensive record of the levels of salmon-trout hybridization in Ireland, are discussed in relation to the continued growth of salmon farming in this country.     

Seawater tolerance in Atlantic salmon, Salmo salar L., brown trout, Salmo trutta L., and S. salar?×?S. trutta hybrids smolt

High levels of hybridization between Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) have been reported in the Gyrodactylus salaris infected Rivers Vefsna and Driva in Norway. The survival and behaviour during the sea phase of such hybrids is unknown. The reported work documents ionoregulatory status after 24 h seawater challenge tests (24hSW) and gill Na⁺/K⁺-ATPase (NKA) activity of migrating wild smolts of Atlantic salmon, brown trout and hybrids at two sampling dates during the 2006 smolt run in River Driva. Salmon, trout and hybrids contributed to 27, 52 and 21% of the catches, respectively. The large contribution of hybrids suggests both a high hybridization rate and a high survival rate from fry to smolt. Both salmon and hybrids had a well-developed seawater tolerance at the time of downstream migration, revealed by small ionoregulatory effects and no or low mortality rates during the 24hSW tests. The trout were not fully adapted to seawater, and high mortality rates were observed (71 and 92%) during the 24hSW tests. The NKA activity was not significantly different between salmon and hybrids. Most of the hybrids were physiologically capable of direct entry to full strength seawater. The incomplete seawater tolerance in trout compared to salmon corresponds well with differences in life-history patterns between these two species. The life history strategy of the hybrids during the sea phase is not known, and further investigations on the marine behaviour and survival is needed to evaluate the role of hybrids in the risk of spreading G. salaris to nearby river systems.     

Effects of Oscillatoria agardhii-toxins on blood pressure and isolated organ preparations

Toxic extracts of the blue-green alga Oscillatoria agardhii were tested for their effect on various isolated laboratory animal preparations. The Oscillatoria-toxins did not show hemagglutinative or hemolytical properties. An immediate rise in blood pressure was seen after intravenous injection in rats. As regards isolated organs, effects were most marked on the liver. Addition of toxic extract to isolated liver perfusion fluid led to physiological, biochemical and pathological changes indicating severe damage to the organ. Negative chronotropic and inotropic effects were found on the isolated heart. The toxins did not influence isolated smooth muscle or nerve striated muscle preparations.     

Swimming performance of brown trout and grayling show species‐specific responses to changes in temperature

Fishways have historically been constructed to restore and preserve the ecological connectivity for fish in fragmented rivers. However, the fishways are often selective on species due to different size and swimming capacity. As the proportion of dammed rivers is still increasing, there is a growing need for more information on wild fish and their migration potential. In this study, we compared the swimming capacity of wild caught brown trout (Salmo trutta) and European grayling (Thymallus thymallus) until the fish were exhausted in a critical swimming speed (U_crit) test, under three different naturally occurring stream temperatures in Norway: 1.7, 5.5 and 10°C. The results indicated that trout swim better at the warmer temperatures than at colder temperatures. The grayling showed consistent swimming patterns with little variation across all tested temperatures. The results therefore signify the need to have operational fishways already early in the spring when the grayling migration starts and highlight the need for more studies on fish migration abilities across a wider range of species and seasons.     

The use of morphometric characters to discriminate specimens of laboratory-reared and wild populations of Gyrodactylus salaris and G. thymalli (Monogenea)

Gyrodactylus thymalli Zitnan, 1960 and G. salaris Malmberg, 1957 have an indistinguishable ribosomal internal transcribed spacer (ITS) DNA sequence, but exhibit surprisingly high levels of intra- and interspecific sequence variation of the mitochondrial cytochrome oxidase I (CO1) gene. To test whether different populations of these reportedly very similar species could be discriminated using morphometric methods, we examined the morphometry of four different populations representing different mitochondrial clades. Twenty five point-to-point measurements, including five new characters of the attachment hooks, were recorded from three Norwegian laboratory populations (G. salaris from the Rivers Lierelva and Rauma, and G. thymalli from the River Rena), and from one wild population of G. thymalli from the River Test, UK. The Norwegian populations were kept under identical environmental conditions to control for the influence of temperature on the haptoral attachment hooks. Data were subsequently subjected to univariate and linear stepwise discriminant analyses. The model generated by the linear stepwise discriminant analysis used 18 of the 25 original variables, the first two roots accounting for 96.6% of the total variation between specimens. The hamulus shaft length accounts for 66.7% of the overall correct classification efficiency. Based on morphometry, all specimens were assigned to the correct species. Apart from three specimens of G. salaris from the River Lierelva population which were misclassified as belonging to the G. salaris Rauma population, all specimens were assigned to the correct population. Thus, populations of Gyrodactylus identified by mtDNA can also be discriminated using morphometric landmark distances.