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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR SYSTEMATICS AND COMPARATIVE POPULATION GENETICS OF PARASITIC ORGANISMS THAT THREATEN FOOD SAFETY AND SECURITY
2007 Annual Report


1a.Objectives (from AD-416)
Objective 1: Employing single-gene and genomic approaches, improve diagnosis of protists and nematodes that parasitize major food animals and that facilitate establishment, internalization, and survival of bacterial pathogens in produce.

Subobjective A: better characterize the molecular epidemiology of parasitic coccidia and trichinella.

Subobjective B: better characterize those bacterophagous eukaryotic microbes that may convey and help establish in produce pathogenic bacteria.

Objective 2: Develop a molecular phylogeny of coccidia in fish in order to better define their potential risk to food safety and security, and in order to better understand the relationship between Eimeriidae (including the agents of avian coccidiosis) and the Sarcocystidae (including the agent of human toxoplasmosis).

Objective 3: Better define the historical and ongoing interactions among wildlife and livestock reservoirs of Toxoplasma gondii through comparative population genetic analysis.


1b.Approach (from AD-416)
Several genes will be sequenced from parasites obtained from a wide array of animals, both domesticated and wild. These will be compared to each other, and to sequences obtained from human beings, in order to define the diversity and epidemiology of these parasite species. Homologues will be characterized for genes whose global variation has already begun to be studied in T. gondii, including the Intergenic Spacer sequence between rRNA genes, beta tubulin introns, and others. Characterization of microsatellite alleles will be considered as a second approach which, although requiring a greater investment of time and resources, should provide greater population genetic resolution than is possible with current loci.


3.Progress Report
Significant progress was made on each Project objective during FY2007. To promote objective 1, methods employing molecular diagnostics for veterinary parasites were validated These included publications on microsatellite alleles in Sarcocystis neurona and two genetic markers that allow definitive identification of larval lungworms in deer. Additional work in this arena led to new discoveries (in manuscripts under review) that provide diagnosis for new species of Sarcocystis in other animal hosts.

To advance our understanding of the diversity and relationships of coccidian fish (objective 2), we built upon a collaboration established in FY2006, and applied a series of genetic analyses to numerous species and isolates of fish parasites. This progress will be presented in September at the International Society of Fish Parasitology and will serve as the basis for a series of forthcoming publications.

To better define the historical and ongoing interactions among wildlife and livestock reservoirs of Toxoplasma gondii (objective 3), we participated in unique collaborative research (ms under review) exploring the hemispheric distribution of parasite alleles defined by sequenced introns. This work has been accepted, pending modest revisions, in the Proceedings of the National Academy of Sciences.

Finally, major strides were made in achieving progress on testing the hypothesis central to objective 4. The methodological progress will be presented at the upcoming XII International Conference on Trichinellosis, and a significant manuscript is now in preparation.


4.Accomplishments
An Interagency Whitepaper on the Systematics of Invasive Species was completed, providing an overview of the challenges posed by invasive species to public health, security, and the economy, and illustrating the needs for accurate and timely detection and identification of the organisms most capable of threatening food safety and security. As defined in the 2006-2010 Food Safety (NP 108) Action Plan, this accomplishment develops diagnostic tools for detecting pathogenic microorganisms under Sections 1.2.1 Detection, exploits sequence and annotation information, genomics and proteomics to elucidate the phylogenetic relationships and relative risk among parasites of critical food safety concern under Sections 1.2.5 (Omics), and Agency Performance Measure 3.1.2: Develop and transfer to Federal agencies and the private sector systems that rapidly and accurately detect, identify, and differentiate the most critical and economically important food-borne microbial pathogens. Implementation of a molecular diagnostic method for identifying larval lungworms. Non invasive methods for diagnosing lungworms remain a problem for the livestock industry. This work helped to diagnose lungworm infections without harming the deer, sheep, or goat in question. This proof of principle was important, because previously available diagnostic methods required arduous recovery of adult worms from post-mortem dissections. Methods developed in our lab permit non-invasive surveys of the parasite burden in natural populations, by definitively identifying those parasites excreted by wild animals or livestock. This approach, and future modifications of it, will assist veterinarians, epidemiologists, wildlife biologists, and population biologists understand how parasitic diseases are distributed, and whether (and where) they may be emerging. As defined in the 2006-2010 Food Safety (NP 108) Action Plan, this accomplishment develops diagnostic tools for detecting pathogenic microorganisms under Sections 1.2.1 Detection, exploits sequence and annotation information, genomics and proteomics to elucidate the phylogenetic relationships and relative risk among parasites of critical food safety concern under Sections 1.2.5 (Omics), and Agency Performance Measure 3.1.2: Develop and transfer to Federal agencies and the private sector systems that rapidly and accurately detect, identify, and differentiate the most critical and economically important food-borne microbial pathogens.

Development of molecular markers to understand the diversity of Sarcocystis neurona. This work addressed the problem of understanding how to differentiate among closely related parasites resembling the agent of Equine Protozoal Myeloencephalitis. The key innovation was discovering variable genetic markers whose distribution could be surveyed among various natural isolates. Whereas traditional methods could not identify these parasites except when experimentally inoculated into laboratory animals, the new method greatly assists in diagnosing the infection using DNA extracted from the primary isolate. These markers can be used by veterinarians, epidemiologists, and pathologists to more easily and precisely identify the causative agent of such parasite infections. As defined in the 2006-2010 Food Safety (NP 108) Action Plan, this accomplishment develops diagnostic tools for detecting pathogenic microorganisms under Sections 1.2.1 Detection, exploits sequence and annotation information, genomics and proteomics to elucidate the phylogenetic relationships and relative risk among parasites of critical food safety concern under Sections 1.2.5 (Omics), and Agency Performance Measure 3.1.2: Develop and transfer to Federal agencies and the private sector systems that rapidly and accurately detect, identify, and differentiate the most critical and economically important food-borne microbial pathogens.


5.Significant Activities that Support Special Target Populations
The work on toxoplasmosis is especially important to the health of pregnant women, fetal and newborn health, and the health of persons afflicted by HIV-AIDS.


6.Technology Transfer

Number of web sites managed1
Number of non-peer reviewed presentations and proceedings2
Number of newspaper articles and other presentations for non-science audiences2

Review Publications
Asmundsson, I.M., Rosenthal, B.M. 2006. Isolation and characterization of microsatellite markers from Sarcocystis neurona, a causitive agent of equine protozoal myeloencephalitis. Molecular Ecology Notes. 6:8-10.

Last Modified: 10/25/2014
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