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United States Department of Agriculture

Agricultural Research Service

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2010 Annual Report

1a. Objectives (from AD-416)
Objective 1: Define higher-level genealogical relationships among strongylate nematodes through analyses of morphological and molecular data as a basis for identification of species and populations of trichostrongyloids and metastrongyloids. Objective 2: Define faunal diversity, exploring history, geography (biogeography), host associations (coevolution) and population genetics (phylogeography) for parasitic nematodes and other helminths in ungulates across North America, Eurasia and globally. Objective 3: Build specimen collections and informatics resources of the U.S. National Parasite Collection.

1b. Approach (from AD-416)
Generality of Phylogenetic Approaches: Comparative phylogenetics is inherently long-term, hierarchical and complex and resides at the core of all approaches outlined in this project (9). Research is largely empirical and hypothesis driven, involving articulation, integration and analyses of comparative morphological and molecular databases. The revolution of phylogenetic systematics has transformed systematic parasitiology and its linkage to animal health, medicine and biodiversity research. Development of phylogenetically informative databases is cumulative, typically involving extensive and detailed description and revision as a first-level process to provide a comparable array of structural, meristic and other characters, and phylogenetically informative sequences from nuclear and mitochondrial loci, across both higher-level and species-level taxa. Hierarchical approaches- e.g., sequential top-down research programs, have proven to be particularly effective beginning with resolution of relationships for higher taxa that form the foundations for eventual elucidation of species-level phylogeny. Robust phylogenies for parasitic groups (the focus of Objective 1) provide the basis for analyses of cospeciation, historical biogeography and phylogeography (the focus of Objective 2) applied to elucidating patterns of host-parasite association, geographic distribution and disease. Phylogenetic studies will address crown clades of nematodes among Strongylida represented by the superfamilies Metastrongyloidea, and Trichostrongyloidea. Investigations will emphasize resolution of relationships at levels extending from putative monophyletic taxa within each major taxon to the level of species and populations as outlined in detail in subsequent sections. Systematic analyses will follow established methodology as exemplified in recent studies. Represented is an integrated program linking research (Objectives 1 & 2) and the U.S. National Parasite Collection (Objective 3). Integration is defined by the following model: (Obj. 1) Specimens with definitive identifications based on morphology from field-based research, including vouchers and type materials, are linked to frozen tissue collections and DNA products as a basis for comprehensive taxonomic revision, description (diagnostic characters), and phylogenetic analyses of specific parasite groups; (Obj. 2) Results of phylogenetic analyses are used as a foundation for historical explorations of biogeography and coevolution and definition of faunal structure over time; and (Obj. 3) Primary specimens, host information, and spatial and temporal data are archived and databased in the USNPC, with results of analyses, diagnostic capacity, images, etc., being integrated in synoptic summaries for parasite and host associations. These archives further summarize the results of phylogenetic, phylogeographic and historical studies.

3. Progress Report
Research activities focused on biodiversity of complex parasite systems and the abiotic and biotic factors influencing geographic and host distribution; conceptual work focused on invasive species and invasion biology under accelerating climate change. Systematics studies involved the medium stomach worms and protostrongylid lungworms and muscleworms in ruminants using integrated methods combining comparative morphology and molecular analyses. Results were disseminated to user communities through publications in journals, and invited lectures in academia. Collections activities for the U.S. National Parasite Collection (USNPC) focused on continuing acquisition of specimens and loans in the national and international community. Series of photomicrographs were provided to researchers in lieu of international loans of irreplaceable type specimens. Over 400 lots of specimens (396 type and voucher slides; and several hundred vials) were rehabilitated or repaired. The USNPC continues as one of the largest specimens-based collection in the world, and as an active and vital cornerstone for parasitological research globally and nationally. Other activities included: training and mentoring graduate students at the University New Mexico and the University of Calgary, Canada.

4. Accomplishments
1. Functional and numerical responses by complex host-parasite systems driven by directional climate warming and ecological perturbation. Explosive emergence of disease attributable to vector-borne nematodes in ungulates occurs as a direct response to extreme events for temperature and humidity. Field-based studies provide the first empirical data indicative of perturbations in geographic distribution or transmission dynamics of helminth pathogens in ungulate hosts under a regime of accelerated climate change. General predictive models emerge for exploring climate-related phenomena, limiting abiotic factors, patterns of development, transmission dynamics and distribution for parasites and hosts. These studies clearly demonstrate the potential to cause disease in free-ranging and domestic ungulates by an array of nematode pathogens that remain poorly known in North America. Such disease and mortality represents a substantial threat to food security.

2. Mosaic structure for nematode faunas in ungulates demonstrated by evolutionary studies. Nematode pathogens in ruminants represent a mosaic fauna of multiple origins (endemic versus introduced). Phylogenetic and historical biogeographic analyses lead to predictions for how parasites will respond in a regime of climate change. Haemonchine and Cooperiine nematodes evolved in African ungulates, have been introduced to North America and are currently constrained in their distributions by temperature and humidity. Shifting isotherms (warming temperatures) and increased precipitation associated with global climate change are predicted to promote rapid northward expansion with new geographic and host distributions for populations of these livestock parasites. Emerging diseases can result from a new ecological context for these and other host-parasite assemblages as a consequence of climate change, exacerbated by developing and broadened resistance to most classes of anthelmintics among these nematodes. Our research responds to the urgency to document and understand the health, agricultural, societal and economic impact of pathogens and emerging infectious diseases in a regime of climate change and ecological perturbation.

Review Publications
Hoberg, E.P., Abrams, A., Pilitt, P.A. 2009. Robustostrongylus aferensis gen. nov. et. sp. nov. (Nematoda: Trichostrongyloidea) in KOB (KOBUS KOB)and hartebeest (Alcelaphus buselaphus jacksoni) from sub-sahara Africa, with further ruminations on the ostertagiinae. Journal of Parasitology. 95:702-717.

Hoberg, E.P., Abrams, A., Pilitt, P.A. 2009. Synlophe structure for species of Longistrongylus (Nematode Trichostrongyloidea), abomasal parasites among ungulates from sub-Saharan Africa, with comparisons to the global ostertagiine fauna. Journal of Parasitology. 95:1468-1478.

Kutz, S., Dobson, A., Hoberg, E.P. 2009. Parasites on the Move Across the Climate Changed Arctic. Science. 236:1187-1188.

Gasbarre, L.C., Smith, L.L., Hoberg, E.P., Pilitt, P.A. 2009. Further characterization of a cattle nematode population with demonstrated resistance to current anthelmintics. Veterinary Parasitology. 166:275-280.

Hoberg, E.P., Abrams, A., Pilitt, P.A. 2010. A new species of trichostrongyloid in African buffalo (Syncerus caffer) (Artiodactyla: Bovinae) from Uganda. Journal of Parasitology. 96:129-136.

Hoberg, E.P., Kumsa, B., Pilitt, P.A., Abrams, A. 2010. Synlophe Structure in Pseudomarshallagia elongata (Nematoda: Trichostrongyloidea), abomasal parasites among Ethiopian ungulates, with consideration of other morphological attributes and differentiation within the Osteragiinae. Journal of Parasitology. 96:401-411.

Laaksonen, S., Pusenius, J., Kumpula, J., Venalainen, A., Kortet, R., Oksanen, A., Hoberg, E.P. 2010. Climate change promotes the emergence of serious disease outbreaks for Filarioid nematodes. EcoHealth. 7:7-13.

Last Modified: 2/23/2016
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