Name: Michael Dark
Title: Assistant professor
College: Veterinary Medicine
Department: Infectious Diseases and Pathology
Curriculum vitae: PDF
Research Interests: Comparative genomics, pathogenic organisms, veterinary pathology
Hobbies: SCUBA diving, flying planes; travel
Dr. Dark came to U.F. and EPI late in 2008 and brings with him a strong background and depth of knowledge in veterinary pathology, having completed a veterinary pathology residency in conjunction with his Ph.D. At EPI, he will contribute to examining the genetic basis for similarities and differences in pathogenic organisms infecting wildlife, livestock and people. He uses comparative genomics, high-throughput sequencing and bioinformatics to analyze different strains of Anaplasma marginale and A. phagocytophilum in order to pinpoint specific genes that contribute to or control the organism’s pathogenicity. His main background is in researching the genomics of Anaplasma strains, a bacterium that is transmitted to mammals via infected ticks. In Florida, Anaplasma infections affect cattle production by causing animals to become anemic, leading to lower milk production or poor health.
Whereas many A. marginale strains are transmissible by tick vectors, the strain endemic to Florida that was initially isolated — known as the Florida strain — appears to be transmitted by a different vector or mechanism. Dr. Dark’s past work investigated genetic causes of this difference, using other strains of the organism that are transmitted by ticks. “The comparative genomic approach is very useful anytime you have a specific phenotypic difference you are looking at, but don’t have a good genetic reason for it,” he said. He has also investigated an A. marginale strain in southern Idaho that is transmissible by only one tick species, and his future research will include sequencing this strain and comparing it to others, to narrow down genes necessary to transmission.
Dr. Dark seeks to use comparative genomics to better understand the full complement of genetic mechanisms A. marginale uses to infect, to avoid a hosts’ immune detection and to persist. He also wants to better understand how the organism affects the health of its host. Most studies on the economic impact of Anaplasma were done in the 1960s and 70s, and so it is very difficult to assess the bacterium’s current economic impact is, especially since it does not tend to cause death in cattle herds where it is well established. Some strains of A. phagocytophilum are known to infect people via infected ticks, and he plans to investigate why some strains seem to be more virulent than others, which cause minimal disease in animal models.
He also plans to research mycobacterium, also known as paraTB, that causes Johne’s disease in animals. This illness produces intestinal inflammation, severe diarrhea and poor health, leading to poor productivity in livestock. It is fatal in many cases. It tends to be a fairly long-lasting problem in herds, Dr. Dark said, because once it gets in a herd, it tends to persist over long time periods, as the younger animals acquire it from older animals. Speculation that the disease process is similar to Chrohn’s disease in humans sparked Dr. Dark’s curiosity to compare the two. “What I’m interested in doing is looking at paraTB strains from humans and from animals, and examine the whole genome to see how closely related they are,” Dr. Dark said. “Because mycobacteria in general, not just paraTB don’t change very much. They tend to have very low rates of variability because they are very slow growing organism.”
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