Habitat connectivity and host relatedness influence virus spread across an urbanising landscape in a fragmentation-sensitive carnivore

Spatially heterogeneous landscape factors such as urbanisation can have substantial effects on the severity and spread of wildlife diseases. However, research linking patterns of pathogen transmission to landscape features remains rare. Using a combination of phylogeographic and machine learning approaches, we tested the influence of landscape and host factors on feline immunodeficiency virus (FIV_Lru) genetic variation and spread among bobcats (Lynx rufus) sampled from coastal southern California. We found evidence for increased rates of FIV_Lru lineage spread through areas of higher vegetation density. Furthermore, single-nucleotide polymorphism (SNP) variation among FIV_Lru sequences was associated with host genetic distances and geographic location, with FIV_Lru genetic discontinuities precisely correlating with known urban barriers to host dispersal. An effect of forest land cover on FIV_Lru SNP variation was likely attributable to host population structure and differences in forest land cover between different populations. Taken together, these results suggest that the spread of FIV_Lru is constrained by large-scale urban barriers to host movement. Although urbanisation at fine spatial scales did not appear to directly influence virus transmission or spread, we found evidence that viruses transmit and spread more quickly through areas containing higher proportions of natural habitat. These multiple lines of evidence demonstrate how urbanisation can change patterns of contact-dependent pathogen transmission and provide insights into how continued urban development may influence the incidence and management of wildlife disease.

A landscape-scale framework to identify refugia from multiple stressors

From a conservation perspective, quantifying potential refugial capacity has been predominantly focused on climate refugia, which is critical for maintaining the persistence of species and ecosystems. However, protection from other stressors, such as human-induced changes in fire and hydrology, that cause habitat loss, degradation, and fragmentation is also necessary to ensure that conservation efforts focused on climate are not undermined by other threats. Thus, conceptual and methodological advances for quantifying potential refugia from multiple anthropogenic stressors are important to support conservation efforts. We devised a new conceptual approach, the domains of refugia, for assessing refugial capacity that identifies areas where exposure to multiple stressors is low. In our framework, patterns of environmental variability (e.g., increased frequency of warm summers), thresholds of resilience, and extent and intensity of stressors are used to identify areas of potential refugia from a suite of ongoing anthropogenic stressors (e.g., changes in fire regime). To demonstrate its utility, we applied the framework to a Southern California landscape. Sites with high refugial capacity (super-refugia sites) had on average 30% fewer extremely warm summers, 20% fewer fire events, 10% less exposure to altered river channels and riparian areas, and 50% fewer recreational trails than the surrounding landscape. Our results suggest that super-refugia sites (∼8200 km² ) for some natural communities are underrepresented in the existing protected area network, a finding that can inform efforts to expand protected areas. Our case study highlights how considering exposure to multiple stressors can inform planning and practice to conserve biodiversity in a changing world.

Does the virus cross the road? Viral phylogeographic patterns among bobcat populations reflect a history of urban development

Urban development has major impacts on connectivity among wildlife populations and is thus likely an important factor shaping pathogen transmission in wildlife. However, most investigations of wildlife diseases in urban areas focus on prevalence and infection risk rather than potential effects of urbanization on transmission itself. Feline immunodeficiency virus (FIV) is a directly transmitted retrovirus that infects many felid species and can be used as a model for studying pathogen transmission at landscape scales. We investigated phylogenetic relationships among FIV isolates sampled from five bobcat (Lynx rufus) populations in coastal southern California that appear isolated due to major highways and dense urban development. Divergence dates among FIV phylogenetic lineages in several cases reflected historical urban growth and construction of major highways. We found strong FIV phylogeographic structure among three host populations north-west of Los Angeles, largely coincident with host genetic structure. In contrast, relatively little FIV phylogeographic structure existed among two genetically distinct host populations south-east of Los Angeles. Rates of FIV transfer among host populations did not vary significantly, with the lack of phylogenetic structure south-east of Los Angeles unlikely to reflect frequent contemporary transmission among populations. Our results indicate that major barriers to host gene flow can also act as barriers to pathogen spread, suggesting potentially reduced susceptibility of fragmented populations to novel directly transmitted pathogens. Infrequent exchange of FIV among host populations suggests that populations would best be managed as distinct units in the event of a severe disease outbreak. Phylogeographic inference of pathogen transmission is useful for estimating the ability of geographic barriers to constrain disease spread and can provide insights into contemporary and historical drivers of host population connectivity.

Urbanization reduces genetic connectivity in bobcats (Lynx rufus) at both intra- and interpopulation spatial scales

Urbanization is a major factor driving habitat fragmentation and connectivity loss in wildlife. However, the impacts of urbanization on connectivity can vary among species and even populations due to differences in local landscape characteristics, and our ability to detect these relationships may depend on the spatial scale at which they are measured. Bobcats (Lynx rufus) are relatively sensitive to urbanization and the status of bobcat populations is an important indicator of connectivity in urban coastal southern California. We genotyped 271 bobcats at 13,520 SNP loci to conduct a replicated landscape resistance analysis in five genetically distinct populations. We tested urban and natural factors potentially influencing individual connectivity in each population separately, as well as study-wide. Overall, landscape genomic effects were most frequently detected at the study-wide spatial scale, with urban land cover (measured as impervious surface) having negative effects and topographic roughness having positive effects on gene flow. The negative effect of urban land cover on connectivity was also evident when populations were analyzed separately despite varying substantially in spatial area and the proportion of urban development, confirming a pervasive impact of urbanization largely independent of spatial scale. The effect of urban development was strongest in one population where stream habitat had been lost to development, suggesting that riparian corridors may help mitigate reduced connectivity in urbanizing areas. Our results demonstrate the importance of replicating landscape genetic analyses across populations and considering how landscape genetic effects may vary with spatial scale and local landscape structure.

Histiocytic sarcoma with central nervous system involvement in dogs: 19 cases (2006-2012)

Background

Reports of histiocytic sarcoma (HS) involving the central nervous system (CNS) are sparse and consist mainly of case reports describing 1–3 animals.

Objective

The objective of this study was to report the signalments, clinical signs, clinicopathologic and diagnostic imaging findings, treatment, and outcome of a series of dogs with HS and CNS involvement.

Animals

Nineteen dogs with HS examined at veterinary referral hospitals.

Methods

Retrospective case series. Medical records were reviewed and cases with a histopathological diagnosis of CNS HS were included in the study. Diagnostic imaging studies of the CNS were evaluated and histopathologic samples were reviewed to confirm the diagnosis.

Results

Retrievers and Pembroke Welsh Corgis were overrepresented in this cohort of dogs. Tumors involved the brain in 14 dogs and the spinal cord in 5. In 4 dogs, HS was part of a disseminated, multiorgan process whereas it appeared confined to the CNS in 15 dogs. Diagnostic imaging had variable appearances although extraaxial masses predominated in the brain. There was meningeal enhancement in all dogs that was often profound and remote from the primary mass lesion. Pleocytosis was present in all dogs with CSF evaluation. Median survival was 3 days.

Conclusions and Clinical Importance

Breed predispositions appear to vary from reports of HS in other organ systems. Some unique imaging and clinicopathologic characteristics, particularly brain herniation, profound meningeal enhancement, and pleocytosis in combination with 1 or more mass lesions, might help to differentiate this neoplasm from others involving the CNS, although this requires further study.

Impact of insulin lispro on HbA1c values in insulin pump users

AIM

To compare the therapeutic efficacy of the short-acting insulin analogue insulin lispro (Humalog) with that of buffered regular human insulin (Velosulin) in patients on insulin pump therapy.

PATIENTS AND METHODS

Sixty-two (45 women and 17 men) young patients with type 1 diabetes using insulin pump therapy were compared while using buffered regular human insulin for a mean +/- s.e.m. of 20.1+/-1.2 months or insulin lispro for a mean +/- s.e.m. of 19.7+/-0.5 months. The initial mean +/- s.e.m. age and duration of diabetes were 29.1+/-0.9 and 17.7+/-0.9 years, respectively. The mean HbA1c values, basal insulin dosages, premeal insulin dosages and number of low blood sugars were recorded during treatment with both insulins.

RESULTS

Mean +/- s.e.m. HbA1c values were significantly lower (p < 0.001; paired Wilcoxon t-test) during insulin lispro treatment (7.4+/-0.1%) as compared to treatment with buffered regular human insulin (7.9+/-0.1%). Total units of insulin (mean +/- s.e.m.)/kg/day was significantly (p = 0.03) lower (0.61+/-0.02) during the insulin lispro treatment period as compared to the buffered regular human insulin treated period (0.65+/-0.03). Total mean +/- s.e.m. (U/kg/day) of basal insulin administered per day was higher when patients received insulin lispro treatment (0.44+/-0.02 vs. 0.42+/-0.01 for buffered regular human insulin treated period; p = 0.002). The premeal insulin boluses (mean +/- s.e.m.) for the two treatment groups were significantly different with less insulin required for the insulin lispro treatment period for all three meals (p < 0.001, t-test). The number of mild/moderate and severe hypoglycaemic episodes were similar in the two groups.

CONCLUSION

We conclude that use of insulin lispro in pump therapy significantly lowers HbA1c values in comparison to therapy with buffered regular human insulin insulin without increasing hypoglycaemic episodes.

Long-term efficacy of humalog in subjects with Type 1 diabetes mellitus

AIMS

To evaluate the long-term effectiveness of Humalog insulin in lowering post meal glucose excursions.

METHODS

Twenty young subjects with Type 1 diabetes mellitus (DM) who had received insulin-lispro (Humalog) for a least 1 year (mean +/- SD 1.8+/-1.6 years) were studied on two occasions, 3-14 days apart. They consumed a similar breakfast consisting of 450-600 kCal having fasted overnight. The same amount of human soluble Humulin Regular or Humalog insulin was given 10 min before the meal in a randomized, double-blind fashion.

RESULTS

Postprandial glucose excursions at 30, 60, and 120 min were significantly lower (P<0.001, ANCOVA) when subjects received Humalog as compared to human soluble insulin. Serum-free insulin levels were significantly higher (P<0.001, ANOVA) at 30 and 60 min when subjects received Humalog as compared with human soluble insulin. Humalog antibody levels after up to 5.4 years of receiving Humalog insulin were not elevated beyond the values at 1 year.

CONCLUSIONS

We conclude that Humalog insulin is effective in lowering postprandial glucose excursions even after up to 5.4 years of treatment.

Pre-meal insulin analogue insulin lispro vs Humulin R insulin treatment in young subjects with type 1 diabetes

The present prospective one-year randomized study was conducted to compare soluble human insulin, with a new rapid-acting human insulin analogue, lispro, with respect to postprandial glucose excursions, frequency of hypoglycaemic episodes, glucose control, and long-term safety in 39 subjects (20 females, 19 males) with Type 1 diabetes. The duration of diabetes, gender distribution, and age were similar in the two groups. The total number of hypoglycaemic episodes was significantly less (p < 0.04, Wilcoxon rank sum test) in subjects receiving insulin lispro compared with regular human insulin over the 12-month period. The 2-h postprandial glucose excursion at 1 year was also significantly less (p < 0.05, ANOVA) in the group treated with insulin lispro. The reductions in the total number of hypoglycaemic episodes and in the postprandial glucose excursion with use of insulin lispro may be beneficial for the long-term management of subjects with Type 1 diabetes. However, the greatest benefit identified by the subjects receiving insulin lispro was the greater convenience of the rapid-acting analogue.

Release of arachidonic acid metabolites by human monocytes or lymphocytes: effect of treatment with interferon on stimulation by phorbol ester or calcium ionophore

The simultaneous production of prostaglandins, leukotrienes, and hydroxyeicosatetraenoic acids was studied in human peripheral blood monocytes obtained by counter-current centrifugal elutriation. Monocytes prelabeled for 4 hr with [3H]arachidonic acid (AA) released label into the surrounding medium in response to treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) or calcium ionophore (A23187). High-performance liquid chromatography of monocyte supernatants demonstrated that labeled compounds included those which eluted with authentic standards for thromboxane B2, 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT), 6-keto-prostaglandin F alpha, prostaglandin E2, and 15-hydroxyeicosatetraenoic acid (HETE). 5-HETE and leukotriene B4 (LtB4) were detected only in response to ionophore treatment. Highly purified lymphocytes did not convert AA to autocoids, despite the release of free arachidonate in response to either stimulus. Pretreatment of monocytes with recombinant human interferon (IFN)-gamma or IFN-alpha for 18 hr resulted in enhanced release of labeled arachidonic acid and increased conversion to autocoids after TPA or ionophore stimulation. Absolute amounts of prostaglandin E2 produced in response to TPA or ionophore treatment were increased as well. These results demonstrate the autocoid profile released by stimulated human monocytes and illustrate the effects of IFN treatment on the production of lipoxygenase metabolites of arachidonic acid as well as cyclooxygenase products.