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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Research Project #431978

Research Project: Immune, Molecular, and Ecological Approaches for Attenuating GI Nematode Infections of Ruminants

Location: Animal Parasitic Diseases Laboratory

Project Number: 8042-32000-105-00-D
Project Type: In-House Appropriated

Start Date: Nov 10, 2016
End Date: Nov 9, 2021

Objective:
Objective 1. Identify and characterize parasitic immune modulators and local immune cell responses associated with GI nematodes of livestock. There is a pressing need for alternative control measures, such as vaccines, to complement/reduce antiparasite drug usage. Parasites evade host immunity by down-regulating or manipulating immune responses in favor of their own survival. Regulatory immune (T and B) cells that are up-regulated during infection may actually control an otherwise hostile environment and, in so doing, limit the host protective response. We propose to characterize parasite-provoked regulatory T/B cells. Further, parasitic immune modulators (PIMs) will be identified and characterized for their ability to induce host regulatory cells. Those PIMs responsible for cross-regulation will be selected as vaccine candidates. Objective 2. Identify proteomic and molecular markers for defining anthelmintic resistance among GI nematodes of livestock. Identifying genetic markers that differentiate the resistant and susceptible parasites will assist in herd management and long-term control. Our approach will be to utilize proteomic analyses and high-throughput transcript sequencing to discern genotypic differences that occur when resistant parasites are placed under drug selection. This will involve comparing drug treated vs. non-drug treated parasites that are resistant to macrocylic lactone class of drugs. This approach will minimize our risk of pursuing coincidentally-associated markers, and provide targets for new therapies. Putative new markers will be confirmed from environmentally-derived samples and will assist in reducing treatments with ineffective drugs. Objective 3. Explore the effects of accelerating climate change and ecological perturbation on managed and wild systems with emphasis on complex host-parasite relationships. Drug resistance cannot be viewed only as a problem of domestic livestock, but must include an evaluation of wild ungulates and the effects that environmental change can have on parasite transmission. With environmental change will come the movement of hosts and therefore exotic parasites into more temperate climates. Comprehensive definitions of parasite faunal diversity serve as the basis for exploring the impact of environmental change on complex systems, and are dependent on accurate baselines for host and parasite distributions. To discern the effects of accelerating climate change, information on parasite diversity will be obtained and summarized based on available georeferenced data from the literature, and on suitable biological collections. Basic studies in taxonomy, systematics and phylogeny of specific nematode groups will enable us to define species diversity in complex faunas among wild and domesticated North American ruminants. Parasite distributions will be mapped using geographic information systems (GIS) and Species Distribution Models (SDM) to assess the effects of global change on how invasion, colonization, and climate change influence the dissemination and persistence of drug resistance genes in the GI nematodes of ruminants.

Approach:
Objective 1. Hypothesis: Parasite infection-elicited host regulatory cells are directly or indirectly induced by the parasitic immune modulators (PIMs). Rationale: Our recent report indicates that B cells and T cells with regulatory phenotypes are expanded in abomasa and the draining lymph nodes (dLN) in cattle raised on pastures. The proposed studies will investigate if single-infection by O. ostertagi, C. oncophora, or H. contortus, and mixed infections thereof induce a similar change in immune cell phenotypes. The ability of PIMs from ES products to enrich host regulatory cells will be investigated. Objective 2: Hypothesis: Drug treatment uniquely alters the genetic and proteomic profiles in resistant worms, enabling the identification of parasite targets associated with the resistance phenotype. Rationale: It is anticipated that the mechanism of resistance to macrocyclic lactones (ML) will be conserved among this broad group of parasites. We intend to focus on C. punctata, given that resistance is well documented and we possess two strains resistant to Ivermectin or Dectomax. Also, once putative markers have been identified, these can be tested against drug resistant forms of Trichostrongylus and Haemonchus, which are also available at our facility. Given the high level of genetic variation in and between nematode populations, resistant and sensitive isolates will also differ genetically in ways unrelated to resistance. To overcome this problem, we will compare proteomic and genomic data from a given, resistant isolate in the presence or absence of ML, hypothesizing that drug treatment will alter proteomic and gene expression profiles. This approach will focus on those genes and gene products regulated by drug treatment and which may differ from those isolates that are not drug resistant. Preliminary data will be generated using Ivermectin and the data will be validated using Dectomax. Objective 3: Hypothesis: Goal: Characterize diversity among species of Haemonchus in North American ruminants. Rationale: Surveys continue to broaden our understanding of parasite diversity, and establish baselines to assess changing patterns of distribution. Several key taxa remain poorly known in North America, and important biogeographic zones have been poorly documented. Borderland areas between managed and natural systems remain a concern given the poor understanding of species diversity for nematodes and their exchange between free-ranging and domestic hosts. Haemonchus nematodes are present in the Nearctic by recent anthropogenic introduction. Thus, radiation in tropical environments suggests this fauna is currently constrained in distribution by patterns of temperature and humidity. Global distributions are attributable to human-related translocation with domestic stock and would be anticipated to respond to accelerating climate warming and environmental change. To better assess change and distributions, we will collect and characterize isolates of Haemonchus and other parasites both morphologically and genetically, then use GIS and SDM’s to model parasite distributions based applications and mapping for ruminant helminth faunas.