Bryanne M. Hoar

Metabolic approaches to understanding climate change impacts on seasonal host-macroparasite dynamics

Climate change is expected to alter the dynamics of infectious diseases around the globe. Predictive models remain elusive due to the complexity of host-parasite systems and insufficient data describing how environmental conditions affect various system components. Here, we link host-macroparasite models with the Metabolic Theory of Ecology, providing a mechanistic framework that allows integrating multiple nonlinear environmental effects to estimate parasite fitness under novel conditions. The models allow determining the fundamental thermal niche of a parasite, and thus, whether climate change leads to range contraction or may permit a range expansion. Applying the models to seasonal environments, and using an arctic nematode with an endotherm host for illustration, we show that climate warming can split a continuous spring-to-fall transmission season into two separate transmission seasons with altered timings. Although the models are strategic and most suitable to evaluate broad-scale patterns of climate change impacts, close correspondence between model predictions and empirical data indicates model applicability also at the species level. As the application of Metabolic Theory considerably aids the a priori estimation of model parameters, even in data-sparse systems, we suggest that the presented approach could provide a framework for understanding and predicting climatic impacts for many host-parasite systems worldwide.

Parasites in Ungulates of Arctic North America and Greenland: A View of Contemporary Diversity, Ecology, and Impact in a World Under Change

Parasites play an important role in the structure and function of arctic ecosystems, systems that are currently experiencing an unprecedented rate of change due to various anthropogenic perturbations, including climate change. Ungulates such as muskoxen, caribou, moose and Dalls sheep are also important components of northern ecosystems and are a source of food and income, as well as a focus for maintenance of cultural traditions, for northerners. Parasites of ungulates can influence host health, population dynamics and the quality, quantity and safety of meat and other products of animal origin consumed by people. In this article, we provide a contemporary view of the diversity of nematode, cestode, trematode, protozoan and arthropod parasites of ungulates in arctic and subarctic North America and Greenland. We explore the intricate associations among host and parasite assemblages and identify key issues and gaps in knowledge that emerge in a regime of accelerating environmental transition.

Development and availability of the free-living stages of Ostertagia gruehneri, an abomasal parasite of barrenground caribou (Rangifer tarandus groenlandicus), on the Canadian tundra.

Climate change in the Arctic is anticipated to alter the ecology of northern ecosystems, including the transmission dynamics of many parasite species. One parasite of concern is Ostertagia gruehneri, an abomasal nematode of Rangifer ssp. that causes reduced food intake, weight loss, and decreased pregnancy rates in reindeer. We investigated the development, availability, and overwinter survival of the free-living stages of O. gruehneri on the tundra. Fecal plots containing O. gruehneri eggs were established in the Northwest Territories, Canada under natural and artificially warmed conditions and sampled throughout the growing season of 2008 and the spring of 2009. Infective L3 were present 3-4 weeks post-establishment from all trials under both treatments, except for the trial established 4 July 2008 under warmed conditions wherein the first L3 was recovered 7 weeks post-establishment. These plots were exposed to significantly more time above 30°C than the natural plots established on the same date, suggesting a maximum temperature threshold for development. There was high overwinter survival of L2 and L3 across treatments and overwintering L2 appeared to develop to L3 the following spring. The impact of climate change on O. gruehneri is expected to be dynamic throughout the year with extreme maximum temperatures negatively impacting development rates.

Evaluation of the enteric microflora of captive whooping cranes (Grus americana) and sandhill cranes (Grus canadensis).

The enteric flora of captive whooping cranes (Grus americana) and sandhill cranes (Grus canadensis) has not been well described, despite its potential importance in the understanding of both the normal condition of the intestinal physiology of these animals and the altered colonization within disease states in these birds. Nineteen whooping cranes and 23 sandhill cranes housed currently at the Calgary Zoo or its affiliated Devonian Wildlife Conservation Centre (DWCC) in Calgary, Alberta were sampled from October 2004-February 2005 by collecting aerobic and anaerobic cloacal swabs from each bird. There were seven major groupings of bacteria isolated from both species of crane. Gram-positive cocci, coliforms, and gram-negative bacilli were the most prevalent types of bacteria isolated for both crane species, with Escherichia coli, Enterococcus faecalis, and Streptococcus Group D, not Enterococcus the bacterial species isolated most commonly. There was a significant difference in the average number of isolates per individual between the two crane species but no differences between age or gender categories within crane species. Campylobacter sp. were isolated from five whooping cranes. The potential zoonotic pathogen Campylobacter jejuni was isolated from one whooping crane and C. upsaliensis was isolated from a second. Three other isolates were unspeciated members of the Campylobacter genus and likely belong to a species undescribed previously. The evaluation of the enteric cloacal flora of whooping cranes and sandhill cranes illustrates that differences exist between these two closely related crane species, and highlights the potential implications these differences may have for current practices involving captive wildlife. Zoo Biol 0:1-13, 2007. (c) 2007 Wiley-Liss, Inc.

Exploiting parallels between livestock and wildlife: Predicting the impact of climate change on gastrointestinal nematodes in ruminants

Global change, including climate, policy, land use and other associated environmental changes, is likely to have a major impact on parasitic disease in wildlife, altering the spatio-temporal patterns of transmission, with wide-ranging implications for wildlife, domestic animals, humans and ecosystem health. Predicting the potential impact of climate change on parasites infecting wildlife will become increasingly important in the management of species of conservation concern and control of disease at the wildlife-livestock and wildlife-human interface, but is confounded by incomplete knowledge of host-parasite interactions, logistical difficulties, small sample sizes and limited opportunities to manipulate the system. By exploiting parallels between livestock and wildlife, existing theoretical frameworks and research on livestock and their gastrointestinal nematodes can be adapted to wildlife systems. Similarities in the gastrointestinal nematodes and the life-histories of wild and domestic ruminants, coupled with a detailed knowledge of the ecology and life-cycle of the parasites, render the ruminant-GIN host-parasite system particularly amenable to a cross-disciplinary approach.

Obligate larval inhibition of Ostertagia gruehneri in Rangifer tarandus? Causes and consequences in an Arctic system.

Larval inhibition is a common strategy of Trichostrongylidae nematodes that may increase survival of larvae during unfavourable periods and concentrate egg production when conditions are favourable for development and transmission. We investigated the propensity for larval inhibition in a population of Ostertagia gruehneri, the most common gastrointestinal Trichostrongylidae nematode of Rangifer tarandus. Initial experimental infections of 4 reindeer with O. gruehneri sourced from the Bathurst caribou herd in Arctic Canada suggested that the propensity for larval inhibition was 100%. In the summer of 2009 we infected 12 additional reindeer with the F1 and F2 generations of O. gruehneri sourced from the previously infected reindeer to further investigate the propensity of larval inhibition. The reindeer were divided into 2 groups and half were infected before the summer solstice (17 June) and half were infected after the solstice (16 July). Reindeer did not shed eggs until March 2010, i.e. 8 and 9 months post-infection. These results suggest obligate larval inhibition for at least 1 population of O. gruehneri, a phenomenon that has not been conclusively shown for any other trichostrongylid species. Obligate inhibition is likely to be an adaptation to both the Arctic environment and to a migratory host and may influence the ability of O. gruehneri to adapt to climate change.

Biodiversity and springtime patterns of egg production and development for parasites of the Chisana Caribou herd, Yukon Territory, Canada

We investigated the biodiversity and springtime patterns of parasite egg/oocyst and larval production from feces and parasite development in the environment for the Chisana caribou herd in the southwest Yukon Territory, Canada from 29 March to 14 June 2006. Fecal samples from 50 adult cows that were housed in a temporary enclosure within the herd’s natural range at Boundary Lake, Yukon Territory were collected and analyzed during 5 sampling periods. A minimum of 6 parasite genera were recovered: eggs of Trichostrongylidae species (most likely Ostertagia gruehneri and Teladorsagia boreoarcticus ), Marshallagia sp., Anoplocephalidae cestodes, and Skrjabinema sp.; oocysts of Eimeria spp.; and dorsal-spined first-stage protostrongylid larvae, including Parelaphostrongylus andersoni . Prevalence of Trichostrongylidae spp. eggs in fresh fecals was at or near 100% throughout the sampling period, however, the median intensity increased significantly from 8 to 34 eggs per gram (epg) at the peak of calving and then decreased to 12 epg 2 weeks post-calving (P = 2.83e-07). Three plots of feces collected from these animals were established outside of the enclosure on 4 May 2006 and monitored every 10 days to investigate patterns of parasite development under natural conditions. The total number of Trichostrongylidae spp. (eggs + larvae) in fecal plots did not change over time, but as the number of larvae increased, egg counts decreased. The presence of other parasite species in the fecal plots remained constant over time. This study is the first to document the parasite diversity for the Chisana caribou herd and to exam¬ine the development and survival of eggs and larvae in feces throughout the spring and early summer. Abstract in Norwegian / Sammendrag: Parasitters artssammensetning og forlop av eggproduksjon og parasittutvikling om varen hos Chisanavillreinen i Yukon, Canada I en periode fra 29. mars til 14. juni 2006 tok vi prover fra reinmokk og under¬sokte artsammensetning, egg/oocysteproduksjon og parasittutvikling i et omrade sorvest i Yukon, Canada, der Chisana caribou’en holder til. Mokkprover fra 50 voksne simler, holdt i en midlertidig inngjerding i det naturlige beiteomradet ved Bondary Lake, ble samlet og analysert i lopet av fem proveperioder. Parasitter fra minst seks slekter ble funnet: materialet omfattet egg av Trichostrongylidae-arter (mest sannsynlig Ostertagia gruehneri og Teledorsagia boreoarcti¬cus ), Marshallagia -art, Anaplocephalidae-bendelmark og Skrjabinema -art, oocyster av Eimeria -arter, og ryggpiggete forstestadiums Protostrongylidae-larver, bl.a. av Parelaphostrongylus andersoni . I ferske mokkprover var prosentvis tilstedevaerelse av Trichostrongylidae-egg nesten 100 % gjennom proveperioden, men median intensitet (parasittmengde) okte statistisk signifikant fra 8 til 34 egg per gram under kalvingens mest intense periode og avtok til 12 egg per gram to uker etter kalving. Mokk fra forsokssimlene ble den 4. mai plassert i tre felt utenfor omradet der simlene ble holdt inngjerdet, og undersokt hver tiende dag for a folge parasittutviklingen under naturlige betingelser. Det totale antall av egg + larver Trichostrongylidae i feltene forandret seg ikke; larvemengden okte samtidig som eggmengden avtok. Tilstedevaerelsen av andre parasitter i feltene forble ogsa konstant over tid. Var studie er den forste til a dokumentere parasittdiversiteten i Chisanavillreinen og a undersoke utviklingen og overlevelsen av egg og larver gjennom var og tidlig sommer.

Amplification of the Second Internal Transcribed Spacer Ribosomal DNA of Individual Trichostrongylid Nematode Larvae by Nested Polymerase Chain Reaction

The second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) is used as a genetic marker to identify trichostrongylid nematodes. However, it is often difficult to amplify by polymerase chain reaction (PCR) the ITS2 rDNA of a single trichostrongylid nematode larva or egg. A nested PCR (nPCR) assay was, therefore, developed to amplify the ITS2 from individual trichostrongylid nematode larvae. The results show that the ITS2 rDNA of a significantly greater proportion of individual larvae was amplified using nPCR compared with a standard PCR. There was also no need to column-purify the genomic DNA before nPCR, which is more time and cost effective for studies involving large sample sizes. The amplicons produced from the secondary phase of the nPCR were subjected to single-strand conformation polymorphism analyses and DNA sequencing to confirm the species identity of the larvae used in the current study as Ostertagia gruehneri. The nPCR assay was also used to amplify the ITS2 from individual trichostrongylid eggs. The ability to amplify the ITS2 rDNA from large numbers of individual nematode eggs and larvae has important implications for diagnostic testing and for conducting epidemiological studies on these parasites of veterinary importance.

Development and survival of Ostertagia gruehneri under natural and artificially warmed conditions on the Canadian tundra

Abstract: Climate change in the Arctic is occurring at an unprecedented rate and is anticipated to alter the ecology of northern ecosystems, including the patterns, diversity, and transmission of infectious diseases. Ostertagia gruehneri is the most common gastrointestinal nematode in caribou and can cause decreased food intake, weight loss, and reduced pregnancy rates in Rangifer species. Because O. gruehneri has a direct life-cycle that includes a free-living stage, the develop¬ ment and survival rates of this parasite are influenced by climate and climate change. To investigate the response of the free-living stages of O. gruehneri to climate change field experiments were done from May to September 2007-08 at the Tundra Ecosystem Research Station (TERS), Daring Lake, Northwest Territories. Fecal plots containing 0. gruehneri were established on the tundra under natural and artificially warmed conditions. Plots were sampled throughout the summer to determine development and survival rates of O. gruehneri and to compare between the two climate regimes (natural vs. warmed). Effects of both temperature and relative humidity on development and survival were investigated. Results from these field seasons will be used, together with laboratory experiments, to develop and validate a predictive model for the impacts of climate change on the epidemiology of O. gruehneri.