Progress 09/01/09 to 08/31/13
Target Audience: The target audience reached in the final reporting period includes (i) researchers and students in the animal health (veterinary) community and (ii) poultry breeders. Efforts to reach this audience included the following: - Use of project data and insights in lectures for veterinary students in the Paul G. Allan School for Global Animal Health (WSU College of Veterinary Medicine). - Development of collaborative relationships with poultry breeders and geneticists to explore breeding as a viable control strategy for management of the northern fowl mite. Changes/Problems: This project experienced delays and deviations from the initial research schedule. Reviewers of a submitted manuscript identified that additional samples were required to conclusively determine that NFM populations were highly structured (unique) among poultry flocks. This required that additional time be dedicated to obtaining mites samples, extracting DNA and conducting PCR analyses. This project yielded the unexpected outcome of extremely structured (genetically different) mite populations that did not provide any insight into the routes of mite migration. As a result, the research goals were adjusted to determine how mites could become genetically distinct and to evaluate methods for preventing mite infestations. This lead to experiments described above that revealed the unusual reproductive biology of the mite (oedipal mating). In addition, effort was directed toward testing the use of mite-resistance poultry breeds to prevent spread of mites in poultry flocks. These changes yielded important insight into the genetics of this ectoparasite that affect persistence and problems with chemical control. In addition, we were able to evaluate a non-chemical strategy for mitigating mite spread, which was a central goal of the original project. What opportunities for training and professional development has the project provided? This project provided training activities and professional development to a graduate student (M.S.), a postdoctoral researcher and two undergraduate students. The graduate student was responsible for extraction of DNA and conducting PCR analyses of mite populations. The M.S. student learned these techniques from the PIs and subsequently trained undergraduate students in the laboratory. The project contributed to the professional development of a postdoctoral researcher that conducted experiments with mites and host transfer between wild birds (sparrows) and chickens. The postdoc gained important knowledge about bird-ectoparasite interactions and disease ecology that she required for career development as an avian ecologist. Finally, two undergraduate students completed research projects concerning animal-ectoparasite interaction, which was relevant to their respective professional. One student subsequently entered Veterinary School. The second student has entered a program in public health. How have the results been disseminated to communities of interest? The data from this project have been reported to the poultry industry by outreach talks at the University of California, Riverside (co-PI Mullens) and Washington State University (PI Owen). What do you plan to do during the next reporting period to accomplish the goals?
What was accomplished under these goals?
Goal 1: Test if northern fowl mites (NFM) are introduced into poultry flocks by wild birds. An important change in knowledge was accomplished under this goal. Prior to this project, it was totally unknown where infestations by this costly ectoparasite originated. Our work demonstrated that wild birds share and exchange mites with poultry flocks. This underscores the importance of biosecurity and exclusion of wildlife from poultry facilities. In addition, we were able to determine that mites established in poultry facilities do not get eradicated, despite the use of pesticides and cleaning of facilities. We observed that mites in production facilities were genetically identical over a 5-year time span, indicating that the NFMswere not eliminated and replaced over that period. Our genetic data indicate that mites remain in facilities to infest new flocks. This further supports the importance of mite prevention, because the ectoparasite is extremely difficult to eradicate once it has established. Goal 2: Determine the routes of migration of NFM between poultry flocks. An important change in knowledge was accomplished under this goal. We discovered a remarkably high level of genetic differentiation among NFM populations. Mite populations separated by several miles were as genetically dissimilar (unique) as populations hundreds of miles apart. These data indicated that NFMs do not migrate frequently among poultry operations. As a result, it is not possible to determine routes of migration between poultry flocks as we originally intended. Instead, we investigated how NFM may spread and genetically diverge at a small scale. We determined that unmated female NFM are able to produce male offspring (sons) that they can mate to produce females. This phenomenon ("oedipal mating") allows NFM to persist and spread at very low population sizes. In other words, this parasite is tolerant of population "bottlenecks" and inbreeding, which promote genetic differences among mite populations. This information is relevant to poultry producers, because it further implicates wild birds as the source of NFM rather than other poultry operations. Goal 3: Characterize how migration rates and environmental conditions influence the spread of pesticide resistance in NFM populations. As discussed under goal #2 (above), it was not possible to determine migration rates of mites among poultry populations. Mite populations appeared highly inbred, permanent and associated with local wild birds. These insights have contributed to a change in knowledge regarding mite control. This parasite becomes entrenched in a poultry operation and develops resistance to pesticides, despite low genetic variation. As such, it appears the reproductive biology of the mite (high tolerance for inbreeding and oedipal mating) make the ectoparasite adaptable to chemical control. For producers this is an important warning. Future research is necessary to determine how quickly newly-introduced NFM may acquire resistance to pesticides.
McCulloch, J.B. and Owen, J.P. (2012) Arrhenotoky and Oedipal Mating in the Northern Fowl Mite.Parasites & Vectors 5: 281. doi:10.1186/1756-3305-5-281
Progress 09/01/11 to 08/31/12
OUTPUTS: The outputs for the 2011-2012 year include ACTIVITIES and PRODUCTS. Based on discussions with collaborators (Busch and Mullens), it was decided that additional field samples of northern fowl mites (NFMs) were needed to add to the database for analysis of genetic variation of NFMs. Specifically, mite samples were needed from multiple hosts within a flock of host birds. Samples were collected and are in the process of DNA extraction and analysis. Collaborative partnerships were developed with colleagues in the field of poultry immunogenetics. These partners include Dr. Marcia Miller (City of Hope Cancer Research Center), Dr. Chris Ashwell (Poultry Science Department; North Carolina State University) and Dr. W. Elwood Briles (Department of Biological Sciences; Northern Illinois University). The objective of these collaborations is to test how variation of genes important to chicken immune function can contribute to natural host resistance to the NFM. Special lines of chickens have been obtained from the Briles and Ashwell labs to test for NFM resistance. PARTICIPANTS: Individuals:<br> Jeb P. Owen (PI; Washington State University): Lead investigator for the project. Owen has coordinated collaborators for sample collection and has been responsible for oversight of immunogenetics experiments.<br> Jeremiah W. Busch (co-PI; Washington State University): Busch has coordinated PCR processing of NFM samples and population genetics analyses.<br> Bradley A. Mullens (formal collaborator; University of California, Riverside): Mullens has continued mite collection from field sites in southern California. These mite samples are being added to the NFM population genetics dataset.<p> Collaborators (non-formal):<br> Marcia Miller (City of Hope Cancer Research Institute): Miller has participated in poultry line selection for testing of NFM resistance in layer hens.<br> Chris Ashwell (Poultry Science Department; North Carolina State University): Ashwell has provided fertilized eggs from inbred poultry lines to the Owen lab for hatching and use in NFM resistance experiments.<br> W. Elwood Briles (Department of Biological Sciences; Northern Illinois University): Briles has provided fertilized eggs from inbred poultry lines to the Owen lab for hatching and use in NFM resistance experiments. TARGET AUDIENCES: Scientists, veterinary personnel, poultry industry PROJECT MODIFICATIONS: Additional mite samples were required to improve the quality of the dataset used to analyze NFM genetic variation. This necessitated additional time to complete the project and a request for a no-cost extension that was granted.
The outcomes/impacts for the 2011-2012 year include new fundamental and applied knowledge. A new collaborative project with colleagues in immunogenetics (Miller, Ashwell, Briles) has generated preliminary data that demonstrate important links between poultry immunological genes and resistance to NFM. Specifically, the B2 haplotype of genes in the major histocompatibility complex (MHC), which is commonly represented in commercial lines of layer chickens, appears to be highly susceptible to NFM infestations. In addition, we have preliminary data that indicate a regulatory region of the MHC will affect chicken resistance to both NFM and the highly virulent Marek's disease virus. These preliminary data indicate that MHC variation is very important to diverse host-parasite interaction (fundamental knowledge). In addition, these data reveal how particular genes in the MHC may be used to enhance broad parasite resistance in commercial poultry (applied knowledge).
- McCulloch, JB and Owen, JP (2012) Arrhenotoky and oedipal mating in the northern fowl mite (Ornithonyssus sylviarum) (Acari: Gamasida: Macronyssidae). Parasites & Vectors 5:281. doi:10.1186/1756-3305-5-281
Progress 09/01/10 to 08/31/11
OUTPUTS: The outputs for the last year include activities and products. We continued to collect northern fowl mite (NFM) samples from wild birds to enlarge our database of the genetic variation represented among populations of this parasite at different spatial scales, and across host types. This effort was facilitated, in part, by a new collaborative relationship with Dr. Robert Cooper in the Warnell School of Forestry and Natural Resources at the University of Georgia. Dr. Cooper, an avian ecologist, has agreed to provide us with NFM samples from songbird nests recovered in his field studies. Our current collaborator at the University of Georgia, Dr. Nancy Hinkle, established this new collaboration. We have continued to characterize the genetics of NFM from wild songbirds. In addition, we conducted an experimental host-transfer of NFM from chickens onto House sparrows (Passer domesticus), to test our hypothesis that wild birds serve as a reservoir for this poultry parasite. The host-transfer experiment involved work by a postdoctoral researcher, Dr. Marisa King. Finally, John McCulloch graduated with a M.S. degree in Entomology, after completing his thesis research project on NFM genetics and population dynamics. PARTICIPANTS: INDIVIDUALS (PI) Dr. Jeb P. Owen (WSU, Department of Entomology) Coordinated collections of NFM from collaborators. Designed host-transfer experiment. Mentored M.S. student (McCulloch) Mentored postdoctoral researcher (King) (PI) Dr. Jeremiah Busch (WSU, School of Biological Sciences) Coordinated data collection and analysis for NFM population genetics. (Postdoctoral Researcher) Dr. Marisa King Executed host-transfer experiment and developed enzyme-linked immunosorbent assay for House sparrow antibody responses to NFM infestation. (M.S. Student) John McCulloch Completed thesis research on NFM breeding biology and population genetics. PARTNER ORGANIZATIONS University of Georgia University of California, Riverside COLLABORATORS Dr. Robert Cooper, Warnell School of Forestry and Natural Resources (University of Georgia) Dr. Hubert Schwabl, School of Biological Sciences (Washington State University) TRAINING Dr. Marisa King (Postdoctoral Researcher) John McCulloch (M.S. Student, Entomology) TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
The outcomes/impacts within the last year involve a change in knowledge. We have determined that wild birds do serve as reservoirs for NFM, but that host switching is very rare. The experimental host transfer of NFM to House sparrows demonstrated that NFM are not able to easily change host species, which supports the genetic data that indicate host switching is infrequent. However, the work of John McCulloch (M.S. student) conclusively demonstrated that NFM are able to establish infestations via a single, unmated female. This is accomplished, because of the haplo-diploid genetics of sex determination for the mite. This recent research has helped produce a new hypothesis for how NFM has become widespread among diverse hosts. Though the probability that any given mite can successfully change host species is low, the extremely large population sizes of the mites, combined with the capability of a single, unmated female to initiate an infestation, creates a "force of infection" that overcomes host barriers. The "force of infection" concept has been applied to modeling dynamics of infectious disease, but to our knowledge this is the first system where the concept applies to an ectoparasite. This project has also provided conclusive evidence that NFM infestations of commercial flocks can persist in poultry facilities up to 5 years. Although researchers have speculated that NFMs are not eradicated from poultry operations, our genetic data provide direct evidence that is true. These insights point to important and viable control strategies for this parasite. First, NFMs can immigrate from wild hosts, but the immigration is rare. Thus, preventing wild bird contact with poultry can effectively limit NFM introduction into clean flocks. Second, once flocks/facilities are infested, the mites can persist for long periods. Thus, it is essential for producers (and researchers) to develop strategies for eliminating NFMs from infested operations.
- King, M.O., Owen, J.P., Schawbl, H. (2011) Injecting the mite into ecological immunology: measuring the antibody response of House Sparrows (Passer domesticus) challenged with hematophagous mites. The Auk. 128 (2): 340-345.
Progress 09/01/09 to 08/31/10
OUTPUTS: Data from this ongoing project were presented in an invited talk at the annual USDA-NIFA project director's meeting (Washington, D.C.) and in a poster presentation at the national meeting for the Entomological Society of America (San Diego). PARTICIPANTS: Co-PI: Dr. Jeremiah W. Busch (Washington State University) - facilitated the PCR and analysis of population genetics data. Collaborators: Dr. Bradley A. Mullens (University of California) - provided mite samples from Southern California. Dr. Nancy Hinkle (University of Georgia)- provided mite samples from Georgia. Training: John B. McCulloch (M.S. student, graduated fall 2010) - conducted DNA extraction, PCR and analysis of genetic data. TARGET AUDIENCES: Poultry producers - The data from this project are expected to inform producers on how best to prevent infestations by northern fowl mite. Population geneticists - The data from this project are expected to provide novel insights into the frequency of host switching by parasites and the applicability of genetic data to analyze that phenomenon. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
The data obtained to date have provided two novel insights regarding northern fowl mite (NFM) as a pest: (1) The NFM is transmitted from wild bird populations into domestic poultry flocks and (2) the mite is capable of persisting in a poultry house over a period of at least 5 years. These data reveal that wild birds are a reservoir for this ectoparasitic pest. As such, strict bio-security and exclusion of wild birds from poultry operations may effectively limit the spread of NFM. Despite chemical control and flock turn-over, it appears that the NFM persists over long periods in poultry houses. For operations that have NFM infestations, measures will have to be developed to eliminate mites from infrastructures.
- McCulloch, J.B., Owen, J.P., Hinkle, N., Mullens, B.A., Busch, J.W. (2010) SPATIAL GENETIC STRUCTURE AND DISPERSAL WITHIN AND BETWEEN HOST SPECIES IN THE NORTHERN FOWL MITE (ORNITHONYSSUS SYLVIARUM). Molecular Ecology (in preparation)