The use of zebrafish as a model in biomedical research has exploded in the last 20+ years. With this growth in research, there is an urgent requirement for research on zebrafish health to grow along with it. I primarily focus on minimizing impacts of Mycobacterium species in zebrafish labs. Where control of the obligate parasites like microsporidia (also a major concern in zebrafish) appears tenable through strict biosecurity policies, mycobacteria are facultative pathogens that can survive outside of the host in surface biofilms. Thus, screening of animals and eggs alone may be ineffective for eliminating mycobacteria that may colonize a facility water, food, or personnel (clothing, hands, equipment), and can then grow and spread in the absence of a host animal.
Further complicating matters, are the multiple etiological agents of mycobacteriosis in zebrafish (and fish in general). Some species are more commonly associated with less pathogenic chronic infections such as M. chelonae, M. abscessus, M. peregrinum, M. fortuitum; whereas M. haemophilum and M. marinum appear to be associated with acute infections and devastating outbreaks.
I am investigating methods of better investigating outbreaks, identifying species, disinfection, and treatment. I am also trying to better understand the role of biofilms in transmission and persistence of mycobacteria in zebrafish facilities.
Myxozoans represent a clade of exclusively parasitic cnidarians that primarily exploit fish hosts. The best known species have economic impacts, but most species and their ecological roles is untapped as a subject of research. The number of nominal myxozoan species is expanding, but likely represents a small fraction of the actual biodiversity considering the abundance of fish host species and tissues to be exploited within these. I use DNA sequence analysis together with morphological analyses to characterize myxozoan diversity and improve existing classification schemes based on an evolutionary framework.
Genetics and Molecular Diagnostics Capacity
In the associated research on this page, there is often a call for molecular diagnostics of parasites/pathogens, or for genetic analysis of pathogens and host species. As a result, my research group often develops these techniques, or adapts and improves existing techniques for use in our research.
The scope and applications are broad because techniques that work for one species are often applicable in other species, with some minor modifications. Some of the work we do includes, but is not limited to:
Identification of unknowns
Population genetics of other species
•Units of Conservation
For details on some specific projects see PDF of a PPT from the January 27, 2016 meeting with the NY DEC
The wild turkey (Meleagris gallapavo) is an iconic North American species, an integral part of forest food webs, and an important game bird for sportsmen. Intensive restoration efforts have helped populations recover substantially from mid-century lows, but wild turkeys still face many threats. According to the New York Department of Environmental Conservation (NYSDEC) wild turkey numbers in the state have steadily declined since 2007. While there are many reasons for downward trends in wildlife populations, the discovery of Lymphoproliferative Disease Virus (LPDV) in wild turkeys throughout the eastern United States, including New York, has raised questions about the role this virus may be playing in these recent fluctuations.
We aim to determine the distribution of LPDV in New York based on PCR testing of bone marrow and blood. In addition using a non-lethal blood based detection, evaluate the fate of infected birds.
PDF of PPT from Jan 27,2016 meeting with DEC - Turkey Research
Cottontail Rabbit Parasites
(Grad student: Emily Gavard)
Once abundant in the region, native New England cottontails (NEC, Syvilagus transitionalis) experienced noticeable population decreases as of the mid twentieth century, are a Species of Special Concern in New York. Their decrease has been attributed to both loss of habitat with dense understory and shrub layers and invasion of their range by eastern cottontails (EC, Sylvilagus floridanus) via range expansion and human introduction.
We are investigating the potential role of parasite mediated competition between NEC and EC (in addition to other factors such as habitat and dispersal). Parasites are examined by fecal flotation and rabbits are identified to species using a mitochondrial DNA RFLP assay.
PDF of PPT from Jan 27,2016 meeting with DEC - Cottontail research
Northern pike sex determination
Northern Pike (Esox lucius) is an important predatory fish in the Great Lakes and St. Lawrence River system. Sex determination within fish populations can be influenced by environmental factors; therefore sex ratio represents an important marker of population health. Northern pike males are heterogametic (XY chromosomes) and a 50:50 male to female sex ratio is expected, but in the St. Lawrence River, long-term data have shown ratios exhibit female dominance (25:75).
Despite its value, sex ratio is typically assessed in mature adult fish during the reproductive phase or through internal examination. Gender determination at early stages of development (e.g., egg and larval) presents a challenge because gonads are not identifiable precluding investigation of sex linked biological processes. Histologically, previous studies have been able to identify gender in pike as young as 45 days post hatch. We are investigating sectioning younger fish to determine the limit of histological gender discrimination.
We are also engaged in the development of a molecular diagnostic tool to determine gender at any life stage in Northern Pike. A known gender set of males (N=3) and females (N=5) was sampled to sequence the entire genome. Based on next generation sequencing data, a cDNA library was developed to produce gender specific transcriptomes whereby male linked markers will be identified for development of a molecular assay. If successful, the male specific assay will be used in experimental trials to test environmental factors hypothesized to influence expected sex ratios.
Environmental factors with the potential to affect sex determination include temperature and xenoestrogens. Endocrine modulators such as xenoestrogens, can interact with natural hormone processes and hormone synthesis, altering the natural regulation of the endocrine system. Sex ratios in fish populations can be highly skewed by endocrine disrupting compounds.
Specifically, we will investigate the effect of temperature and xenoestrogen treatments on sex ratio for Northern Pike eggs and larvae. We will incubate batches of fertilized eggs in controlled treatments and compare sex ratio outcomes using the gender determination test. Pike will be raised in each of 3 treatments, increased temperature, xenoestrogen treatment (estradiol), and a control. Understanding the presence and influence of these environmental factors on Northern Pike development will provide insight for future management practices.