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Recent evidence demonstrates genomic and morphological continuity in the Arctic ancestral lineage of dogs. Here, we use the Siberian Husky to investigate the genomic legacy of the northeast Eurasian Arctic lineage and model the deep population history using genome-wide single nucleotide polymorphisms. Utilizing ancient dog-calibrated molecular clocks, we found that at least two distinct lineages of Arctic dogs existed in ancient Eurasia at the end of the Pleistocene. This pushes back the origin of sled dogs in the northeast Siberian Arctic with humans likely intentionally selecting dogs to perform different functions and keeping breeding populations that overlap in time and space relatively reproductively isolated. In modern Siberian Huskies, we found significant population structure based on how they are used by humans, recent European breed introgression in about half of the dogs that participate in races, moderate levels of inbreeding, and fewer potentially harmful variants in populations under strong selection for form and function (show, sled show, and racing populations of Siberian Huskies). As the struggle to preserve unique evolutionary lineages while maintaining genetic health intensifies across pedigreed dogs, understanding the genomic history to guide policies and best practices for breed management is crucial to sustain these ancient lineages and their unique evolutionary identity.

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BACKGROUND: Greenland sled dogs (GSD) are a unique, genetically isolated population of dogs living under exceptional environmental conditions. Metabolism, and thereby thyroid hormones are affected by multiple factors. Among other activity, energy balance and environmental conditions are important. A breed-specific reference interval (RI) can be useful for diagnostics of potential thyroid-related pathologies. The aim of this study was to establish RIs of the thyroid hormones thyroxin (T4), free thyroxin (fT4), and thyroid stimulating hormone (TSH) in GSD. In addition to evaluate the effect of sex, age, season, management, and body condition score (BCS) in GSD. Physical exams and cephalic venous blood sampling were performed in the period of 2018-2019 from 265 GSD managed either privately or by the Danish navy. Serum biochemical analyses, including C-reactive protein, were performed and RIs were determined for TSH, T4 and fT4 in only healthy dogs. The RIs were determined using American Society for Veterinary Clinical Pathology guidelines and the effect of varying factors were evaluated by linear regression and further tested by Mann-Whitney test. RESULTS: 144 GSD were included in the reference group resulting in RIs: T4: 6.44-48.65 nmol/L; fT4: 3.91-18.51 pmol/L; and TSH: 0.04-0.55 ng/mL. Female GSD had significantly higher concentrations of T4 (P = 0.039) and fT4 (P = 0.015) compared to males; a positive correlation between TSH and aging was found; T4 concentrations were significantly higher (P = 0.003) during summer; and TSH concentrations were lower in GSD managed by the navy (P < 0.0001). BCS was higher (P < 0.0001) in Sirius GSD compared to civilian GSD, and BCS was positively correlated with T4 and negatively correlated with TSH. CONCLUSIONS: Reference intervals for T4, fT4 and TSH in GSD were established. The RI for T4 and fT4 was lower compared to other breeds. In addition, sex, age, season, management and BCS demonstrated variable effects on thyroid hormones. Our results can be used as a foundation for improving management and further research of GSD.

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Tryptophan (Trp), an indispensable amino acid for dogs, is the precursor of serotonin, a neurotransmitter with a variety of effects throughout the body, including the ability to modulate cardiac and pulmonary activity. This study aimed to investigate the effects of a 12-week incremental exercise regimen and supplemental dietary Trp on heart rate (HR) and respiratory rate (RR) in client-owned sled dogs. Sixteen Siberian huskies were randomly allocated to either treatment or control diet groups. Both groups were fed a control diet (Trp to large neutral amino acid ratio of 0.047:1); however, treatment dogs received a Trp supplement to achieve a Trp to large neutral amino acid ratio of 0.075:1. Every three weeks, external telemetry equipment was used to non-invasively measure and record HR and RR at a resting, working, and post-exercise state in a controlled exercise challenge. A mixed model was used to test differences between diet, activity parameter, and week. Dietary Trp supplementation had no effect on HR or RR. Independent of diet, resting, working, post-exercise HR, and time to recover post-exercise HR decreased from week -1 to week 11 (p < 0.05). Resting HR had the greatest reduction from week -1 to week 11 (21%, p < 0.05). Working RR did not change with exercise (p > 0.10), but rRR and postRR decreased from week -1 to week 11 (p < 0.05). These data suggest that the exercise regimen the dogs were subjected to may have positively impacted the dogs' capacity to sustain aerobic exercise, whereas Trp supplementation had no effect on HR or RR.

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Exercise improves the health of dogs; however, the extreme exertion experienced by sled dogs may lead to variable metabolic and fecal characteristics. Nutritional interventions, such as dietary tryptophan (Trp), may reduce the prevalence of these exercise-induced disturbances. Sporting diets tend to have high crude protein concentrations in contrast to adult maintenance diets and this results in less Trp relative to other amino acids (AA). Therefore, sporting dogs represent an ideal cohort to assess the effects of supplemental Trp. The objective was to evaluate the effects of supplemental dietary Trp and an incremental training regimen on AA and serotonin status, fecal scores and metabolites, and body composition in client-owned Siberian huskies. Sixteen dogs (nine females and seven males) were used, with a mean age of 4.8 ± 2.5 yr and body weight (BW) of 24.3 ± 4.3 kg. Dogs were blocked for sex, age, and BW and randomly allocated into two groups with eight fed a dry extruded control diet (Ctl) and eight fed Ctl supplemented with Trp to reach a Trp:large-neutral AA (LNAA) ratio of 0.075:1 (treatment, Trt). The exercise regimen was designed to increase in distance each week, but weather played a role in setting the daily distance. Each week BW was recorded and food allotments were adjusted to maintain initial BW. Pre and post-exercise blood samples were taken every 3 wk, dogs then received a meal followed by 1, 2, and 4 h post meal blood collections (serum AA, serotonin). Stool collection and scoring occurred each week and body composition was measured on weeks -1 and 11. Serotonin, AA, fecal metabolite, and body composition data were analyzed using PROC MIXED of SAS with dog as a random effect and week and Trt as fixed effects. Stool score data were analyzed using PROC FREQ to compare stool score and Trt, and PROC CORR was used to analyze associations between fecal score, temperature, humidity, and run distance. Dogs on Trt had greater fasted Trp compared with baseline, greater post-meal Trp and serotonin compared with baseline, greater post-meal Trp compared with fasted, and greater post-meal Trp and serotonin compared with Ctl (P < 0.05). Fecal data indicated that Trp improved stool scores (P < 0.05) yet had no effect on fecal metabolites. An overall increase in lean and decrease in fat mass was found (P < 0.05), but Trt had no effect on body composition. Optimization of the dietary Trp:LNAA ratio may help to improve GI health without compromising performance in actively training sled dogs.

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Inhibitory control is a term used to envelop a collection of processes that allow an organism to refrain from engaging in an inappropriate prepotent or responsive behavior. Studies have examined the propensity of inhibitory control by nonhuman animals, from the cognitively complex processes involved in self-control to potentially less cognitively taxing processes such as motoric self-regulation. Focusing on canines, research has suggested that the domestication process as well as experiences during ontogeny contribute to inhibitory control. Diet may also play an important role in an individual's ability to self-regulate. This study examined this possibility by investigating motoric self-regulation in sled dogs, using three well-established tasks (i.e., A-not-B Bucket, Cylinder, and A-not-B Barrier tasks), performed after consumption of one of three dietary treatments with different glycemic index values. We also compared the performance of sled dogs during these tasks with results previously obtained from pet dogs. Overall, the results show many similarities in the performance of sled dogs and pet dogs on the motoric self-regulation tasks, with the notable exception that sled dogs may have a stronger spatial perseveration during the A-not-B Bucket task. Previous research findings reporting a lack of correlation among these tasks are also supported. Finally, during the early postprandial phase (period after consumption), dietary treatments with different glycemic index values did not influence self-regulatory performance for sled dogs.

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Exposure to long-range transported industrial chemicals, climate change and diseases is posing a risk to the overall health and populations of Arctic wildlife. Since local communities are relying on the same marine food web as marine mammals in the Arctic, it requires a One Health approach to understand the holistic ecosystem health including that of humans. Here we collect and identify gaps in the current knowledge of health in the Arctic and present the veterinary perspective of One Health and ecosystem dynamics. The review shows that exposure to persistent organic pollutants (POPs) is having multiple organ-system effects across taxa, including impacts on neuroendocrine disruption, immune suppression and decreased bone density among others. Furthermore, the warming Arctic climate is suspected to influence abiotic and biotic long-range transport and exposure pathways of contaminants to the Arctic resulting in increases in POP exposure of both wildlife and human populations. Exposure to vector-borne diseases and zoonoses may increase as well through range expansion and introduction of invasive species. It will be important in the future to investigate the effects of these multiple stressors on wildlife and local people to better predict the individual-level health risks. It is within this framework that One Health approaches offer promising opportunities to survey and pinpoint environmental changes that have effects on wildlife and human health.

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Gastritis and gastric ulcers are an important cause of morbidity and mortality in canine athletes. Although the majority of scientific work on this condition has been performed in ultraendurance racing sled dogs, this condition has been identified in other canine athletes, including sled dogs competing in shorter events and dogs performing off-leash explosive detection duties. The cause of the syndrome is unknown, but current hypotheses propose a link between exercise-induced hyperthermia and loss of gastric mucosal barrier function as an early event in the pathogenesis. Treatment is focused on prevention of clinical disease using acid secretion inhibitors, such as omeprazole, which has excellent efficacy in controlled clinical studies.

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OBJECTIVE: The objective of this study was to assess the effects of both short-term anaerobic exercise and long-term aerobic exercise on leptin, adiponectin and irisin concentrations in both sprint and endurance canine athletes. DESIGN: Prospective field trial repeated measures. The 25 racing Greyhounds were run over 400 m, with blood samples collected prior to exercise and at 10 min and 120 min after exercise. The 16 sled dogs were run an average of 3.5-5 h/day on 5 out of 8 days of stage stop racing competition, with assessment on days 0, 2 and 8. RESULTS: Baseline leptin concentrations were found to be lower than previously recorded values of domestic dogs, possibly because of a lower body fat content in athletes, with concentrations in sled dogs being slightly higher than those in Greyhounds. Baseline adiponectin concentrations in both groups of dogs, on average, were lower than most previously recorded values in domestic dogs; although unexpected, these findings may be attributed to differences in body fat content of the study population. CONCLUSION: Endurance exercise in sled dogs resulted in a persistent decrease in leptin that appears to be independent of race-associated weight loss, with no appreciable changes in adiponectin or irisin concentrations. The anaerobic exercise of Greyhounds produced no detectable changes in leptin and adiponectin concentrations; however, a significant rise in irisin 10 min post-exercise may be a compensatory mechanism for restoration of ATP homeostasis in skeletal muscle.

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The achievements of sled dogs in competitions depend both on their training and on their health. Vector-borne infections may lead to anemia, affect joints or heart muscles or even cause death. Canine babesiosis is an emerging, quickly spreading tick-borne disease in Central Europe. Over a 13-year period (2000-2012) the occurrence of babesiosis cases was analyzed in one sled dog kennel situated in Kury, a village near Tluszcz (N 52°24'56.78″, E 21°30'37.55″) in Central Poland. Twenty cases/episodes of babesiosis were noted among the 10-12 dogs living in the kennel. In 2000-2004, no cases of babesiosis were noted; the first two cases were noted in April 2005. Since that time, only one dog remained uninfected; 6 dogs were infected once, 3 dogs demonstrated symptoms of babesiosis twice, one dog was infected three times and one dog had it five times. Babesiosis appeared in Spring and Autumn, despite the application of anti-tick treatment. No fatal cases were recorded, but in one case a splenectomy was performed due to splenomegaly and spleen rupture. Additionally, the abundance of the main Babesia canis vector, the Dermacentor reticulatus tick, was estimated and monitored during a 4-year period (2008-2012) close to the dog kennel. The abundance of questing ticks was high in 2008 and 2009, but dropped by 10-fold between 2010 and 2012, when the abandoned meadow was cut and used as horse pasture by the local farmer. The regular occurrence, typical seasonal pattern and identification of B. canis DNA in questing tick from this locality confirmed the establishment of a new hyper enzootic region for canine babesiosis. The effectiveness and schedule of applied preventive measures were discussed.

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The achievements of sled dogs in competitions depend both on their training and on their health. Vector-borne infections may lead to anaemia, affect joints or heart muscle or even cause death. Between December 2009 and October 2010, one hundred and twenty six individual blood samples were collected from 26 sled dog kennels situated in different regions of Poland. The majority of samples were taken during the racing season (winter 2009/10). The prevalences of 3 vector-borne infections- including 2 'old pathogens' Anaplasma phagocytophilum and Babesia canis, and 'new pathogen' Hepatozoon canis-were estimated in sled dogs using PCR and nested PCR. Additionally, 25 serum samples originating from a subset of 3 kennels situated in a tick-borne encephalitis (TBE) endemic area (Mazowiecki region), were tested for antibodies against the tick-borne encephalitis virus (TBEV). Because of the recently reported occurrence of Dirofilaria repens in Central Poland and that of fatal cases of unknown aetiology in two of the kennels, blood samples collected from dogs at these kennels in 2010 and in February-May 2013 and from two unaffected kennels were checked for evidence of presence of this parasite. Babesia canis DNA was detected in 11 sled dogs (4 with clinical babesiosis, 7 asymptomatic; 8.7%) inhabiting mainly endemic regions of Poland (9/11 cases). Three serum samples originating from one location tested positive for TBEV antibodies (total seroprevalence: 3/25=12%, local seroprevalence: 3/12=25%). The risk of TBEV infection was associated with previous B. canis infections. Dirofilaria repens DNA was detected in 15 dogs (44%). Prevalence was especially high in two sled dog kennels situated near Grodzisk Mazowiecki (50-57%). No blood samples tested positive for A. phagocytophilum or H. canis DNA. The present study has established that the prevalence of vector-borne pathogens in working sled dogs is significant in the endemic regions and has justified the important role of surveillance of reservoir hosts in the epidemiology of TBE. Our results emphasize the need for regular monitoring for the presence of D. repens.

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Sled dogs are known to develop numerous serum biochemical changes due to endurance exercise. Previous studies have suggested that mild hyponatraemia and hypokalaemia can develop during endurance racing. The aim of the present study was to determine if serum biochemical alterations are similar to previous reports, and if electrolyte alterations are still present with present feeding practices utilised by mushers. Serum chemistries were obtained from 26 Alaskan Huskies belonging to 3 different teams, before and after a 1600 km race. Meals and snacks were analysed via calculation to determine daily macronutrient and electrolyte intake. Numerous biochemical alterations were observed including significant differences in serum total protein, albumin, globulin, aspartate aminotransferase, creatine kinase, TAG, NEFA and urea nitrogen (P < 0·05). Serum electrolyte status revealed a mild, yet significant decrease in serum sodium (P = 0·002); and serum potassium was not significantly different (P = 0·566). Further examination of the sodium intake across the three teams revealed two teams with an average daily intake of approximately 8·5 g/dog/d (700 mg/4184 kJ) and the other team consuming 11·1 g/dog/d (1200 mg/4184 kJ). Regression analysis shows a significant modest positive correlation between serum sodium decrease and sodium intake per metabolic body weight of the dogs, as well as a modest positive correlation between sodium intake and serum potassium implicating the renin-angiotensin aldosterone system as a major factor involved in sodium and potassium homoeostasis. These findings suggest that consumption of approximately 0·9 g/kg(0·75) (1·2 g/4184 kJ) of sodium per d may prevent exercise-induced decreases in sodium and potassium.

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Both dopamine receptor D4 (DRD4) exon 3 and tyrosine hydroxylase (TH) intron 4 repeat polymorphisms have been linked to activity and impulsivity in German Shepherd dogs (GSDs). However, the results in GSDs may not be generalisable to other breeds, as allelic frequencies vary markedly among breeds. We selected the Siberian Husky for further study, because it is highly divergent from most dog breeds, including the GSD. The study sample consisted of 145 racing Siberian Huskies from Europe and North America. We found that this breed possesses seven DRD4 length variants, two to five more variants than found in other breeds. Among them was the longest known allele, previously described only in wolves. Short alleles of the DRD4 and TH repeat polymorphisms were associated with higher levels of activity, impulsivity and inattention. Siberian Huskies possessing at least one short allele of the DRD4 polymorphism displayed greater activity in a behavioural test battery than did those with two long alleles. However, the behavioural test was brief and may not have registered variation in behaviour across time and situations. Owners also completed the Dog-Attention Deficit Hyperactivity Disorder Rating Scale (Dog-ADHD RS), a more general measure of activity and attention. Siberian Huskies from Europe with two short alleles of the TH polymorphism received higher ratings of inattention on the Dog-ADHD RS than did those with the long allele. Investigation of the joint effect of DRD4 and TH showed that dogs possessing long alleles at both sites were scored as less active-impulsive than were others. Our results are aligned with previous studies showing that DRD4 and TH polymorphisms are associated with activity-impulsivity related traits in dogs. However, the prevalence of variants of these genes differs across breeds, and the functional role of specific variants is unclear.

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Before adopting modern corn-and-grain-based western processed diets, circumpolar people had a high fat and protein subsistence diet and exhibited a low incidence of obesity, diabetes and cardiovascular disease. Some health benefits are attributable to a subsistence diet that is rich in omega-3 fatty acids and antioxidants. Pollution, both global and local, is a threat to wild foods, as it introduces contaminants into the food system. Northern indigenous people and their sled dogs are exposed to a variety of contaminants, including mercury, that accumulate in the fish and game that they consume. The sled dogs in Alaskan villages are maintained on the same subsistence foods as their human counterparts, primarily salmon, and therefore they can be used as a food systems model for researching the impact of changes in dietary components. In this study, the antioxidant status and mercury levels were measured for village sled dogs along the Yukon River. A reference kennel, maintained on a nutritionally balanced commercial diet, was also measured for comparison. Total antioxidant status was inversely correlated with the external stressor mercury.