M.S.

Life-history strategies are adaptations in behavior, physiology, and anatomy that influence survival and reproductive success. Variation in life-history strategies is often determined by adaptations to environmental conditions and trade-offs with sexually-selected signals. One of the aspects controlling life-history trade-offs is the endocrine system. Testosterone is a hormone that mediates several key aspects of male reproduction, yet little is known about the causes and consequences of variation in testosterone. Using rufous-collared sparrows (Zonotrichia capensis), a Neotropical songbird with a wide distribution, I explored geographical patterns of variation in testosterone levels and infection by haemosporidians, a type of blood parasite. I found that testosterone did not vary with elevation, nor predict haemosporidian infection, but males in breeding condition were more likely to be infected (Chapter I). High levels of testosterone have been associated with an increased number of sexual contacts and can suppress the immune response, thus it may increase the risk of sexually transmitted infections. By studying the communities of bacteria that reside in the cloaca of birds, I found that they were different depending on testosterone levels, and that high-testosterone males had higher relative abundance of Chlamydiae, a class of intracellular pathogens (Chapter II). During the breeding season there is an increase in physical contacts among individuals, testosterone levels increase in males, and there are additional energetic demands, all of which can increase exposure to bacteria or facilitate infection. I compared the cloacal microbiome of the same individuals between breeding and non-breeding seasons, and found that in males, but not in females, bacterial richness and phylogenetic diversity increased when birds were in reproductive condition. This suggested that the cloacal microbiome in birds is dynamic and responsive to breeding condition and sex of the host (Chapter III). Lastly, I synthesized the most relevant findings and suggested directions for future work (Chapter IV). I conclude that variation in testosterone is not always associated with immune suppression, and that the links among reproductive physiology, behavior, and the microbiome can provide insight into the evolution of life-history strategies. / Ph. D.

Understanding how species respond to anthropogenic changes and why species respond in the way that they do can help focus conservation planning. Hellbenders (Cryptobranchus alleganiensis) are a freshwater species of increasing conservation concern that are suspected to have declined due to loss of forest cover. However, quantitative evidence of land use effects on hellbenders is lacking. I used a multilevel approach to understanding whether hellbenders respond to land use by examining physiological indices, demographics and patterns of species occurrence as endpoints. My study area included two major river drainages in Virginia which mark a largely understudied portion of the species' range. In Chapter I, I described hellbender distribution and tested the hypothesis that hellbenders would be more likely to occur in heavily forested landscapes. Surprisingly, hellbenders occupied a relatively wide land use gradient (range = 50-90% forest in an upstream catchment) and current land use was an unreliable predictor of occurrence. In Chapter II I examined hellbender abundance and demographics at a subset of study sites stratified across a land use gradient. Abundance of sub-adult/adult hellbenders increased as forest cover increased in collective upstream riparian areas, primarily as the result of increased recruitment of new adults to local populations (rather than increased apparent survival of adults). Populations in lesser forested areas were declining and composed largely of relatively old adults, indicating that land use can lead to changes in hellbender distribution given sufficient time. In Chapter III, I examined three indices of physiological condition (body condition, hematocrit and leukocyte profiles) in hellbenders captured across a land use gradient. I found evidence suggesting low reproductive success may explain reduced recruitment in areas of low forest cover and evidence suggesting hellbender endocrinology during the breeding season may vary with land use. In Chapter IV I examine efficacy of artificial shelters as a monitoring tool and demonstrate their potential as tool to further our understanding of mechanisms underlying demographic responses of hellbenders to land use. I synthesize my findings in Chapter V and conclude that loss of forest cover in riparian areas poses a formidable threat to hellbender population viability in Virginia. / Ph. D.

Haemonchus contortus, otherwise known as the “Barber Pole Worm”, “The Wire Worm” or simply as the large stomach worm of sheep, has been the subject of much scientific interest for the past quarter of a century. Considerable work has been done which has established this parasite as a factor of economic importance and its presence as a pathological agent in the abomasum of ruminants is generally well recognized. This worm is one of the largest of the Strongyloid group, measuring sometimes an inch in the females and three-quarters inch in the males, and its general anatomy is fairly well known. The literature does not, however, reveal any work which has been done in connection with the development of the reproductive cells of this species. In the present work a study has been made of spermatogenesis and oogenesis with some attention directed to methods of copulation, the passage of the sperm cells upon entrance into the vulva and the anatomical location in the female where the sperms are collected for the purpose of fertilization of the ova. No histologic section, depicting the entrance of the sperm into the ova, has been observed but the developmental stages immediately following this penetration of the ova are shown in this paper. Even though a considerable amount of material has been examined which has afforded opportunity for studying the entire reproductive organs of both male and female worms, several developmental stages which have been reported as occurring in nematodes, have not been observed in this study. Sufficient evidence, however, is herein presented which indicated very clearly and definitely the normal chromosome number. / Master of Science

We live in an era of global change, where emerging infectious diseases such as Ebola, Zika, bird flu, and white nose syndrome are affecting humans, wildlife, and domesticated species at an increasing rate. To understand and predict the dynamic spread of these infectious agents and other symbionts through host populations and communities, we need dynamic mathematical models that accurately portray host-symbiont transmission. But transmission is an inherently difficult process to measure or study, because it is actually a series of interacting processes influenced by abiotic and biotic factors at multiple scales, and thus empirical tests of the transmission function within epidemiological models are rare. Therefore, in this dissertation, I explore factors at the individual, population, and community-levels that influence host contact rates or symbiont transmission success in a common snail-symbiont system, providing a detailed description of the multi-faceted nature of symbiont transmission. From a review of the ecological literature, I found that most models assume that transmission is a linear function of host population density, whereas most empirical studies describe transmission as a nonlinear function of density. I then quantified the net nonlinear transmission-density relationship in a system where ectosymbiotic oligochaetes are directly transmitted among snail hosts, and I explored the ecological mechanisms underlying the nonlinear transmission-density relationship observed in the field via intraspecific transmission success and contact rate experiments in the laboratory. I found that the field results could be explained by heterogeneity in transmission success among snails with different characteristics and nonlinear contact-density relationships caused by non-instantaneous handling times. After I 'unpacked'population-level transmission dynamics into those individual-level mechanistic processes, I used this same approach to examine higher-level ecological organization by describing the mechanistic underpinnings of interspecific or community-level transmission in the same snail-symbiont system. I found that low interspecific transmission rates in the field were the product of opposing interactions between high population densities, high prevalences of infection, and very low interspecific transmission success caused by strong symbiont preferences for their current host species. Unpacking transmission in this way resulted in one of the most detailed empirical studies of transmission dynamics in a wildlife system, and yielded many surprising new insights in symbiont ecology that would not have been discovered with a purely phenomenological or holistic view of transmission. Though simple, linear, and holistic epidemiological models will always be important tools in disease ecology, 'unpacking'transmission rates and adding heterogeneity and nonlinearity to models, as I have done here, will become increasingly important as we work to maximize model prediction accuracy in this era of increased disease emergence. / Ph. D.

Cats are infected with a variety of internal parasites, some of which are zoonotic. Therefore, being able to effectively detect and determine prevalence of internal parasites in cats is important for both feline and human health. Some parasites are easier to detect than others. Diagnosing Giardia duodenalis and Cryptosporidium spp. can be difficult because cysts and oocysts shed in the feces are small, shed intermittently, and require a trained technician to consistently identify them. As a result, infections with these protozoan parasites can be missed. Fecal immunoassays detect antigens in feces and can have increased sensitivity when compared to traditional microscopic techniques, but still do not detect every infection. The current reference standard is an immunoassay known as the direct immunofluorescent assay, but it requires expensive equipment and a long incubation period. As a result, two prototype lateral flow fecal immunoassays, the Cryptosporidium EZ VUE and Giardia EZ VUE, designed by TECHLAB® Inc were evaluated for the ability to detect G. duodenalis and Cryptosporidium spp. infections in cats because they are cheap, easy to use, easy to store and easy to interpret. In addition, samples were examined using a 33% zinc sulfate (ZnSO4) centrifugal fecal flotation procedure and the MERIFLUOR® Cryptosporidium/Giardia direct immunofluorescent assay (IFA), which served as the reference test. Other internal parasites found on the centrifugal fecal flotation with zinc sulfate were recorded to determine prevalence. Both EZ VUE fecal immunoassays demonstrated potential in diagnosing infections in cats when compared to centrifugal fecal flotation and the reference. Additionally, a variety of other internal parasites were identified. This included several potentially zoonotic species including Spirometra mansonoides, Ancylostoma sp. and Toxocara cati, which was also the most commonly identified species of parasite. Additionally, it was determined that several factors may contribute to higher prevalence of parasites especially in cats with the status of stray or feral. / M. S.

1. Hypoderma lineatum and Hypoderma bovis are prevalent in Burkes Garden and Southwestern Virginia generally. 2. Young cattle, calves and yearlings particularly, are generally more heavily infested than older cattle. 3. Adults appear in Burkes Garden the first warm days in April though they are at their worst in June and July, a normal season. 4. Larvae ordinarily make their first appearance in the subcutaneous tissues of the back about the first of December. The first ones emerge and pupate about the middle of January. 5. At the time control was started H. lineatum exceeded H. bovis in the ratio of 65 to 35 percent. The ratio now is 55 to 45 percent. 6. Salt, wet or dry, is an ineffective dressing for killing Hypoderma larvae in the subcutaneous tissues of the host. 7. Benzol, 90 or 100 percent, injected into larval cysts effects a high percentage of kill. 8. Hand extraction at intervals of 30 days repeated five times is a practical and effective means of control. 9. Hand extraction performed by the average farm worker caused an occasional case of anaphylaxis, .037 percent 10. Cooperative control measures, to be effective, should be supervised closely. 11. Extraction of Hypoderma larvae from the subcutaneous tissues of the host effects gains in weight and milk flow advantageously. 12. Control measures as practiced in Burkes Garden has reduced Hypoderma infestation by approximately 50 percent. / M.S.

Intestinal parasitic infections (IPI's) are considered to be a public health problem of global importance by the World Health Organization. The present epidemiologic survey study investigated the prevalence, risk factors, and consequences of pathogenic IPI's on the growth, nutrition and psychomotor development of 244 Ecuadorian children aged 0.2-14 years. The study was conducted in five rural hamlets located in a tropical rainforest area in northwest Ecuador. The study data were obtained by means of a structured questionnaire, a developmental screening examination, anthropometry, and lab analysis of blood and fecal samples. Data analysis was conducted using appropriate bivariate and multivariate statistical techniques. The study results revealed that 90% of the child subjects were infected with at least one pathogenic IPI species. Fifty-one percent were identified with helminthic infections, 37.6% with protozoal infections, and 21.4% were infected with both. The most common intestinal parasites detected were Ascaris lumbricoides (39.7%), Giardia intestinalis (25.2%), Trichuris trichiura (19.7%), Entamoeba histolytica/dispar (18.5%), Blastocystis hominis (13.3%), and Ancylostoma duodenale (1.7%). The prevalence of growth stunting (40%) and iron-deficiency anemia (26%) also was high. Children infected with Giardia exhibited a risk for stunted growth that was twice that of their non-infected counterparts (51.7% vs. 33.1%; OR=2.16, 95% C.I.= 1.13-4.15; p= 0.01). They also had significantly reduced mean blood hemoglobin levels compared to non-infected children 11.8 + 1.5.g/dL vs. 12.2 + 1.4g/dL; p= 0.023) but the proportion with iron-deficiency anemia was slightly but not significantly increased (29.4% vs. 24.3%). The characteristic most consistently associated with risk for pathogenic protozoal IPI's was a high density of domestic animals living in and around the home. Children who lived in such households had a risk for infection that was 2-5 times greater than others. This suggests that domestic animals were important reservoirs for IPI infection in the child group studied. Contrary to the a priori hypothesis, no gender, ethnic, nor age differences in infection risk were identified except for Trichuris infection, which was reduced in younger children contrary to expectations. Mass or targeted chemotherapy combined with health education and promotion are needed to reduce the cycle of infection and re-infection and the negative impact of these on child growth and iron status. Health education and promotion messages can be incorporated into other types of programs already in place in local schools and by the Ecuadorian Ministries of Public Health, Education, and Social Welfare and other agencies. / Master of Science

The larval stage of the cat flea, Ctenocephalides felis felis (Bouche), was found to exhibit behaviors that were conducive to its security in carpet. Larvae exhibited positive geotactic, and negative phototactic behaviors. This resulted in the larvae spending greater than 80% of their time at the base of the carpet pile. Cat flea larvae also exhibited a positive hydrotaxis, and appeared to exhibit undirected movements when foraging. Larva were observed to respond to disturbances by coiling their body longitudinally. Cat flea hatched and unhatched eggs, and larval exuviae were found to be dispersed in a contagious fashion within carpet. The spatial pattern of the immature stages and remains was influenced by the habits of the pet host within a given room. First-instar larvae do not move far, if at all, from the location of eclosion. The movement of the larval stage is influenced by biotic and abiotic factors in the environment. Areas of high pedestrian or pet traffic are not conducive to successful eclosion from the egg or for successful larval development. Various methods of control exist for controlling an indoor infestation including both non-chemical and chemical tactics. A method for the physical control of immature stages in carpet is vacuuming. A beater-bar vacuum removes about 50% of the eggs but less than 30% of the larvae from a carpet. Chemical control tactics indoors are normally conducted using a compressed-air sprayer. Pressure within the application system is critical for creating spray patterns which can be overlapped to allow even insecticide coverage of the substrate. A compressed-air application system is not capable of delivering pesticides in a manner that will completely penetrate the carpet substrate to reach the base of the carpet. No significant differences in carpet penetration were observed over a range of 20 to 70 psi. Regardless of pressure, more than 93% of the solution applied to carpet was deposited in the upper third (6 mm) of the carpet. Pet owners were surveyed about their knowledge and perceptions of household infestations of the cat flea, and also about financial expenditures and their willingness to pay for a flea-free environment. The importance and the pest status of flea infestations were determined to be based on physical, psychological, and economic impacts on homeowners. Respondents' perceptions of infestations on their pet were associated with infestation levels in the house. The respondents were willing to pay more for flea control in July, the onset of the flea season, than they were at the peak or decline of the season. They were also willing to pay more as their perception of the intensity of the problem on the pet or in the home increased. Household income was not shown to affect a respondent's actual financial expenditures or his willingness to pay for flea control on the pet or in the home. / Ph. D.

Ph. D.