Dissertation
Anaplasma marginale infection dynamics in an edemic area
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004411
Handle:
https://hdl.handle.net/2376/119165
Abstract
Anaplasma marginale, the cause of bovine anaplasmosis, is a tick-transmitted disease responsible for economic losses to the cattle industry worldwide. The disease is characterized by progressive anemia, reduced production and death. In areas of high transmission, most animals are infected with multiple strains, which through time may lead to more severe outcomes. Multistrain infections may occur either by co-infection when multiple strains infect a host prior to an adaptive immune response or by superinfection, when a second strain establishes infection following an immune response to the initial strain. We address this knowledge gap by tracking the acquisition of A. marginale strains overtime under natural transmission conditions in a cattle herd in southern Ghana. We first determined that 97% of animals in the study herd have multistrain infections and these strains are acquired by co-infection and superinfection. On average, the number of strains acquired via superinfection was 16% lower than the number of strains acquired by co-infection. In A. marginale sequential variation in major surface protein 2 (Msp2), and outer membrane protein allows for immune evasion and superinfection. Msp2 is encoded by up to 10 alleles that are recombined into a single expression site. In experimental infections, strains that differ in at least one genetically distinct msp2 allele can establish superinfection which is accompanying by relative over-expression of the unique allele. The contribution of msp2 allelic variation to superinfection in a natural transmission setting is unknown. In our study herd in southern Ghana, we tracked the msp2 allelic repertoire and its usage at coinfection and superinfection. We identified new msp2 pseudogenes in all animals at superinfection. Of all expressed Msp2 variants at superinfection, an average of 32% were derived from the new pseudogenes in three animals, while none of the new pseudogenes were expressed in two of the animals. Thus, superinfection is associated with the introduction of new pseudogenes, but these new pseudogenes are not over-expressed at superinfection. Overall, these studies are the first major steps in unravelling the complexity of how multistrain infections are established in a natural transmission setting and though time will help in developing more sophisticated intervention strategies.
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Details
- Title
- Anaplasma marginale infection dynamics in an edemic area
- Creators
- Roberta Koku
- Contributors
- Susan M Noh (Advisor)Kelly Brayton (Committee Member)Troy Bankhead (Committee Member)Massaro Ueti (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Veterinary Medicine, College of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 120
- Identifiers
- 99900883238401842
- Language
- English
- Resource Type
- Dissertation