Browsing by Author "Michael K. Stoskopf, Committee Co-Chair"

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    Diagnostics and Epidemiology of Infectious Agents in Mountain Gorillas.
    (2010-04-27) Whittier, Christopher Alan; Ronald R. Sederoff, Committee Member; Michael K. Stoskopf, Committee Co-Chair; Michael R. Loomis, Committee Member; Barrett D. Slenning, Committee Co-Chair
    ABSTRACT WHITTIER, CHRISTOPHER ALAN. Diagnostics and Epidemiology of Infectious Agents in Mountain Gorillas. (Under the direction of Michael K. Stoskopf and Barrett D. Slenning) Infectious diseases are one of the major threats to remaining populations of free-ranging great apes. Infections from humans are a particular concern because of increasing contact between apes and human researchers, tourists, and local communities. This study advances our understanding of infectious disease risks to free-ranging mountain gorillas (Gorilla beringei beringei) by developing and utilizing improved noninvasive diagnostics to survey wild gorillas; performing serosurveys of gorillas and locally confiscated primates to identify exposure patterns; and designing a disease transmission model to better evaluate and predict pathogen spread and epidemic outcomes in the mountain gorilla population. The risk from human and any other infections to wild apes is difficult to quantify partly because of limited diagnostic sampling. Sample collection is often restricted by the challenges of sampling free-ranging apes, while sample analysis can be constrained by storage and shipping protocols that often require fresh or frozen samples. This study expands diagnostic capabilities by showing that noninvasively collected gorilla fecal samples can be stored in guanidine isothiocyanate solution at room temperature for 6 months and allow diagnostic detection of rotavirus RNA by polymerase chain reaction (PCR). Additionally it demonstrates that advanced molecular diagnostics using real-time PCR technology can be performed directly in the field thereby bypassing the need for sample preservation and shipping. This study used a portable real-time PCR instrument to detect an 87% prevalence of a Campylobacter spp. in 157 fecal samples, and to further reveal that this gorilla Campylobacter spp. appears to be a novel isolate. Using opportunistically collected blood samples, free-ranging mountain gorillas (N=57) are shown to be exposed to 19 of 37 pathogens assayed including many that are prevalent in local human populations. Evidence of exposure from local human populations is further confirmed by a companion survey of 32 confiscated gorillas and other nonhuman primates that documented cases of seroconversion associated with captivity and in some cases with only human contact, in 2 subspecies of gorillas and three species of other primates. The infectious disease outbreak model developed in this study demonstrated the importance of modeling the mountain gorilla population as a realistic network of interconnected groups. The model shows that, in the absence of humans, the known low gorilla intergroup contact rates severely restrict the spread of infection between gorilla groups. More significantly, the model suggests that even a small group of regular human visitors with limited gorilla contact can facilitate the spread of infections between gorilla groups and thereby increase gorilla population outbreak levels.
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    Effects of Percutaneous Malathion Absorption in Anurans
    (2005-11-09) Willens, Scott; Andrew D. Wallace, Committee Member; Sharon K. Taylor, Committee Member; Craig V. Sullivan, Committee Member; Gregory A. Lewbart, Committee Co-Chair; Michael K. Stoskopf, Committee Co-Chair; Ronald E. Baynes, Committee Member
    The objective of this research was to characterize the percutaneous absorption of the organophosphorous pesticide, malathion, across the skin of bullfrogs (Rana catesbeiana) and marine toads (Bufo marinus) using in vitro models. An established mammalian model for percutaneous absorption, the two-compartment Teflon flow-through diffusion cell assay, was adapted to anuran skin to examine species and anatomical site differences in absorption and partitioning of C¹⁴-radiolabeled malathion. Malathion absorption was greater across the ventral skin compared to dorsal skin in both bullfrogs and marine toads but did not differ significantly between species. The issue of short-term storage and viability of anuran skin for diffusion cells was examined using glycerol preservation and cryopreservation techniques. Bullfrog skin viability was retained for 28 days, while marine toad skin viability significantly decreased after 7-10 days. A novel in vitro model, the harvested perfused anuran limb (HPAPL) preparation, which maintained an intact microvasculature to the skin, was developed. The HPAPL represented an improvement over diffusion cells by retaining the anatomic and physiologic integrity of the skin. Doppler ultrasound was used to determine the perfusion rate for the HPAPL by measuring the physiologic blood flow of the pelvic limb in vivo. In addition to the characterization of the percutaneous absorption of malation in anurans, effects of sublethal doses on brain acetyl cholinesterase activity in bullfrogs and marine toads, were examined using a modified Ellman spectrophotometric technique. Sensitivity to environmental toxins make anurans potentially important animal models for studying the impacts of organophosphorous insecticide contamination of the environment.
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    Evaluation of a Trap-Neuter-Return Management Program for Feral Cat Colonies: Population Dynamics, Home Ranges, and Potentially Zoonotic Diseases.
    (2006-03-01) Nutter, Felicia Beth; Richard B. Ford, Committee Member; Roger A. Powell, Committee Member; Michael K. Stoskopf, Committee Co-Chair; Jay F. Levine, Committee Co-Chair
    Management of feral cats is controversial, and alternatives to lethal control methods are gaining popularity. To evaluate the effectiveness of sterilization programs, nine feral cat colonies were divided into groups of three, managed either by spaying females and castrating males, spaying females and vasectomizing males, or leaving all cats intact. Colonies were followed intensively for four years, and intermittently for three additional years. Most cats were trapped in fewer than ten trap nights each. Breeding females produced a mean of 1.4 litters/year and 3 kittens/litter. Kitten mortality was 75% by 6 months of age. Feral and pet domestic cats had similar baseline health status and prevalences of FIV, FeLV, Cryptosporidium, Giardia, and Toxocara cati, but feral cats had higher prevalences of Bartonalla henselae and Toxoplasma gondii. Castrated male and spayed female cats survived longer than intact male and female cats. Survival times of vasectomized males were equivalent to those of intact males. Control colonies decreased in size and remained stable in composition, while intact colonies increased in size and had high turnover. One neutered colony went extinct and several others had fewer than five cats at the end of the project. Home ranges of both intact and neutered cats were small, usually less than 1 ha. Vasectomized males had larger home ranges than either intact or castrated males, probably because they were searching for intact females. Community-level stakeholder meetings were successful in building consensus among groups, and a basic decision tree for feral cat management was developed. Computer simulation modeling using VORTEX software suggested that harvesting breeding colonies every one or two years at 50% to 100% can keep colonies small, but will not lead to long-term reductions in cat numbers. Models of neutered colonies suggested that 75% to 80% sterilization is necessary to cause population decrease and eventual extinction. The mean estimated time to extinction of 12.8 years fits well with ongoing observations of steady decline in sterilized colonies.