Genetic variation and population structure in the endangered Houston toad in contrast to its common sympatric relative, the coastal plain toad

Title from PDF of title page (University of Missouri--Columbia, viewed on October 25, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Raymond D. Semlitsch and Dr. Michael R. J. Forstner.Vita.Ph. D. University of Missouri--Columbia 2010.I determined the number of populations, the levels of genetic diversity within and among populations, and migration/movement rates at the landscape and fine scales in the endangered Houston toad, Bufo houstonensis (Anura: Bufonidae) using mitochondrial sequence data and microsatellite loci. Genetic clustering analyses indicate nine populations across the range. The most divergent population was in Austin County, Texas. Genetic diversity was high across the range and within populations. I also examined population genetic structure and diversity in a common, sympatric congener, the coastal plain toad (Bufo nebulifer). Bufo houstonensis and B. nebulifer have comparable levels of genetic diversity, but B. nebulifer appears to migrate less frequently or over less distance than its endangered congener. Finally, I investigated the baseline levels of genetic admixture, or hybridization, in B. houstonensis. Admixture between B. houstonensis and two sympatric species (B. nebulifer and Bufo woodhousii) was detected. With continued habitat alteration and rising temperatures, both habitat isolation and offset breeding season have already partially broken down as isolating mechanisms and may deteriorate further; consequently, opportunities for hybridization events will increase. Conservation recommendations for B. houstonensis include supplementation programs to increase the number of individuals, preservation of all three habitat types (breeding/nursery, occupied, and dispersal), special attention towards the Austin County population, and involvement of the general public in conservation.Includes bibliographical reference

Case Reports1. A Late Presentation of Loeys-Dietz Syndrome: Beware of TGFβ Receptor Mutations in Benign Joint Hypermobility

Background: Thoracic aortic aneurysms (TAA) and dissections are not uncommon causes of sudden death in young adults. Loeys-Dietz syndrome (LDS) is a rare, recently described, autosomal dominant, connective tissue disease characterized by aggressive arterial aneurysms, resulting from mutations in the transforming growth factor beta (TGFβ) receptor genes TGFBR1 and TGFBR2. Mean age at death is 26.1 years, most often due to aortic dissection. We report an unusually late presentation of LDS, diagnosed following elective surgery in a female with a long history of joint hypermobility. Methods: A 51-year-old Caucasian lady complained of chest pain and headache following a dural leak from spinal anaesthesia for an elective ankle arthroscopy. CT scan and echocardiography demonstrated a dilated aortic root and significant aortic regurgitation. MRA demonstrated aortic tortuosity, an infrarenal aortic aneurysm and aneurysms in the left renal and right internal mammary arteries. She underwent aortic root repair and aortic valve replacement. She had a background of long-standing joint pains secondary to hypermobility, easy bruising, unusual fracture susceptibility and mild bronchiectasis. She had one healthy child age 32, after which she suffered a uterine prolapse. Examination revealed mild Marfanoid features. Uvula, skin and ophthalmological examination was normal. Results: Fibrillin-1 testing for Marfan syndrome (MFS) was negative. Detection of a c.1270G > C (p.Gly424Arg) TGFBR2 mutation confirmed the diagnosis of LDS. Losartan was started for vascular protection. Conclusions: LDS is a severe inherited vasculopathy that usually presents in childhood. It is characterized by aortic root dilatation and ascending aneurysms. There is a higher risk of aortic dissection compared with MFS. Clinical features overlap with MFS and Ehlers Danlos syndrome Type IV, but differentiating dysmorphogenic features include ocular hypertelorism, bifid uvula and cleft palate. Echocardiography and MRA or CT scanning from head to pelvis is recommended to establish the extent of vascular involvement. Management involves early surgical intervention, including early valve-sparing aortic root replacement, genetic counselling and close monitoring in pregnancy. Despite being caused by loss of function mutations in either TGFβ receptor, paradoxical activation of TGFβ signalling is seen, suggesting that TGFβ antagonism may confer disease modifying effects similar to those observed in MFS. TGFβ antagonism can be achieved with angiotensin antagonists, such as Losartan, which is able to delay aortic aneurysm development in preclinical models and in patients with MFS. Our case emphasizes the importance of timely recognition of vasculopathy syndromes in patients with hypermobility and the need for early surgical intervention. It also highlights their heterogeneity and the potential for late presentation. Disclosures: The authors have declared no conflicts of interes

Prevalence of human-active and variant 1 strains of the tick-borne pathogen Anaplasma phagocytophilum in hosts and forests of eastern North America

Anaplasmosis is an emerging infectious disease caused by infection with the bacterium Anaplasma phagocytophilum. In the eastern United States, A. phagocytophilum is transmitted to hosts through the bite of the blacklegged tick, Ixodes scapularis. We determined the realized reservoir competence of 14 species of common vertebrate hosts for ticks by establishing the probability that each species transmits two important strains of A. phagocytophilum (A. phagocytophilum human-active, which causes human cases, and A. phagocytophilum variant 1, which does not) to feeding larval ticks. We also sampled questing nymphal ticks from ∼ 150 sites in a single county over 2 years and sampled over 6 years at one location. White-footed mice (Peromyscus leucopus) and Eastern chipmunks (Tamias striatus) were the most competent reservoirs for infection with the A. phagocytophilum human-active strain. Across the county, prevalence in ticks for both strains together was 8.3%; ticks were more than two times as likely to be infected with A. phagocytophilum human-active as A. phagocytophilum variant 1

Co-infection of blacklegged ticks with Babesia microti and Borrelia burgdorferi is higher than expected and acquired from small mammal hosts

Humans in the northeastern and midwestern United States are at increasing risk of acquiring tickborne diseases--not only Lyme disease, but also two emerging diseases, human granulocytic anaplasmosis and human babesiosis. Co-infection with two or more of these pathogens can increase the severity of health impacts. The risk of co-infection is intensified by the ecology of these three diseases because all three pathogens (Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti) are transmitted by the same vector, blacklegged ticks (Ixodes scapularis), and are carried by many of the same reservoir hosts. The risk of exposure to multiple pathogens from a single tick bite and the sources of co-infected ticks are not well understood. In this study, we quantify the risk of co-infection by measuring infection prevalence in 4,368 questing nymphs throughout an endemic region for all three diseases (Dutchess County, NY) to determine if co-infections occur at frequencies other than predicted by independent assortment of pathogens. Further, we identify sources of co-infection by quantifying rates of co-infection on 3,275 larval ticks fed on known hosts. We find significant deviations of levels of co-infection in questing nymphs, most notably 83% more co-infection with Babesia microti and Borrelia burgdorferi than predicted by chance alone. Further, this pattern of increased co-infection was observed in larval ticks that fed on small mammal hosts, but not on meso-mammal, sciurid, or avian hosts. Co-infections involving A. phagocytophilum were less common, and fewer co-infections of A. phagocytophilum and B. microti than predicted by chance were observed in both questing nymphs and larvae fed on small mammals. Medical practitioners should be aware of the elevated risk of B. microti/B. burgdorferi co-infection

Reservoir competence of vertebrate hosts for Anaplasma phagocytophilum

Fourteen vertebrate species (10 mammals and 4 birds) were assessed for their ability to transmit Anaplasma phagocytophilum, the bacterium that causes human granulocytic anaplasmosis, to uninfected feeding ixodid ticks. Small mammals were most likely to infect ticks but all species assessed were capable of transmitting the bacterium, in contrast to previous findings

Predictions of infection prevalence in host-collected ticks fed on sciurids using a permutation analysis assuming independent assortment of all three pathogens, and deviations of observed data from those predictions.

<p>Bolded <i>p-</i>values are significant at α = 0.05.</p

Log (base 2) of the observed: expected ratio of questing <i>Ixodes scapularis</i> nymphs.

<p>Log (base 2) of observed: expected ratio of each infection status of questing <i>Ixodes scapularis</i> ticks sampled at 161 sites across Dutchess County, NY, USA. The magnitude and direction of the log ratios illustrates the extent to which the observed levels of co-infection differed from expected levels of co-infection due to random assortment of pathogens. Pathogens sampled include <i>Anaplasma phagocytophilum</i> (Ap), <i>Babesia microti</i> (Bm), and <i>Borrelia burgdorferi</i> (Bb). Expected infection frequencies are based on 100,000 random permutations of infection frequencies for each pathogen.</p

Co-infection prevalence of Anaplasma phagocytophilum, Babesia microti, and Borrelia burgdorferi in wildlife host species groups.

<p>Mean co-infection prevalence for Anaplasma phagocytophilum (Ap), Babesia microti (Bm), and Borrelia burgdorferi (Bb) of host-collected Ixodes scapularis ticks fed on (A) small mammal, (B) meso-mammal, (C) sciurid, and (D) bird host species. Each category represents the mean prevalence of each specific co-infection type as opposed to overall prevalence. Error bars show standard error. Note that no co-infections were observed in D. carolinensis.</p