Powassan (POW) virus, the cause of human encephalitis in the northeastern U.S. and Canada, is transmitted by tick bite. Since the geographic and host distribution patterns of Ixodes dammini Spielman, et al, 1979 and POW virus overlap, the potential of this tick species to transmit POW virus was explored. Transmission experiments were conducted with hamsters and rabbits which fed immature and adult ticks, respectively, from a POW-free colony. Oral infection rates in larvae and nymphs fed on POW-infected hamsters were 10% and 40%, respectively; in females fed on POW-infected rabbits, 57%. Transstadial transmission rates for nymphs exposed to POW virus as larvae, adults exposed as larvae, and adults exposed as nymphs, were 9.5%, 10% and 54%, respectively. Evidence of transovarial transmission was acquired when 2 clean hamsters feeding F$ sb2$ larvae and nymphs originally exposed to virus in the F$ sb1$ nymphal stage seroconverted to POW virus with hemagglutination inhibition titers of 80 and 5120, respectively, on week 4 post-tick-drop-off. The transovarial transmission rate was 16.6%. All developmental stages were able to transmit POW virus orally to clean hosts regardless of when the ticks were originally exposed to virus. / These results indicate that I. dammini is a competent vector of POW virus under experimental conditions. Field studies are necessary to determine if the same holds true under natural conditions.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2007. / Vita. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Wisconsin--Madison, 1944. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [42-45]).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1976. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 81-83).

Würzburg, Univ., Diss., 2002.

Thesis (M. Med. Sc.)--University of Hong Kong, 2006.

Since the field-defining patient HM, consistent links have been made between a region of the brain called the hippocampus and memories that can be consciously declared - so called declarative memories. Declarative memories fall into two categories (1) episodic memories, memories that are highly detailed and re-experiential, and (2) semantic memories, fact-based memories for personal and public information but that have no sense of re-experiencing. It is believed that the intrinsic anatomy of the hippocampus supports episodic memory but not semantic memory. The hippocampus consists of five regions (cornu Ammonis, CA, 1-3, dentate gyrus, subiculum) with each purported to have a specific role in episodic memory acquisition and retrieval. However, controversy surrounds the temporal extent to which episodic memories rely on the hippocampus for retrieval: current consensus suggests the hippocampus supports these memories for five-10 years post-acquisition, but some suggest that it is required for retrieval across the lifetime. Voltage-gated potassium channel-complex antibody-mediated limbic encephalitis (VGKC-complex LE) is a recently described autoimmune disease that causes chronic hippocampal atrophy and mild amnesia on standardized neuropsychological assessment. Two subfields of the hippocampus - CA1 and CA3 - contain the antigenic targets of the disease but it is unknown if specific atrophy of these subfields underlies the hippocampal damage in humans. Here, the human hippocampal subfield volumes of VGKC-complex LE patients (n = 19, mean age: 64.0±2.55; range: 24-71) were investigated using ultra-high spatial resolution MRI at 7.0-Tesla. Assessment also included standardized neuropsychology to examine the impact of the pathology on hippocampal-dependent and -independent memory performance, as well as attention, language, executive function, and perception Declarative memory assessment measured semantic and episodic memory performance across the lifespan. Manual segmentation detected lesions to just CA3, with no volume loss noted elsewhere in the hippocampus or brain. Patients were impaired on hippocampal-dependent memory domains but not the hippocampal-independent and non-memory domains. Notably, episodic memory assessment revealed episodic amnesia across the lifetime except for their earliest memories. This counters the received convention that the hippocampus has a temporally limited role in episodic retrieval. Conversely, the performance of the VGKC-complex LE patients for semantic memory, including a new test developed herein, was comparable to controls across the lifespan. It was then shown that CA3 volume predicted episodic memory performance across the lifetime. Together, the results suggest that VGKC-complex LE provides a novel model of human hippocampal subfield pathology, with which to explore the roles of hippocampal subfields in episodic memory acquisition and retrieval.

Foi realizado um estudo epidemiológico da epidemia de encefalite por arbovírus na região do Vale do Ribeira, São Paulo, Brasil, durante o período de março de 1975 a julho de 1978. A epidemia, iniciada em 1975, atingiu o pico em 1976. A partir de 1978 a moléstia se manteve em níveis baixos sob presumível endemicidade. A letalidade nos anos epidêmicos de 1976 e 1977 variou em sentido inverso ao da morbidade, que apresentou picos nas épocas de maior temperatura e pluviosidade. Ao que parece, a epidemia teria se deslocado em onda em direção leste-oeste e leste-sudoeste tendo atingido a região litorânea vizinha. A cadeia montanhosa situada ao norte e noroeste teria atuado como barreira à propagação da moléstia. Considerou-se a hipótese que o agente etiológico, arbovírus Rocio, só recentemente deva ter começado a infectar a população humana, tendo sido veiculado ao homem a partir de reservatórios silvestres, aves e pequenos mamíferos, por culicídeos silvestres. Discutiram-se também prováveis formas de transmissão domiciliar da arbovirose ocorrida em número bem menor de casos. Verificou-se que os grupos populacionais que apresentaram as formas mais graves da doença foram os das idades extremas e os de piores condições de vida. Considerou-se que a perspectiva epidemiológica desta arbovirose é que ela persista na região, uma vez que existem condições ótimas para o desenvolvimento dO agente etiológico, de reservatórios e de vetores biológicos, além do contínuo afluxo de população suscetível, constituída por migrantes ou por turistas. / An epidemiological study of the encephalitis epidemic by arbovirus was carried out in Ribeira River Valley, State of São Paulo, Brazil, from March 1975 to July 1978. The epidemic began in 1975 and reached its peak in 1976. From 1978 onwards the disease maintained low levels in a presurnable endemicity. The lethality of the disease in the epidemic years of 1976 and 1977 varied in the opposite direction of its morbility, which presented peaks when the temperature and pluvial levels were higher. It seems that the epidemic swept from east to west and from east to southwest in a wave towards the neighbouring coastland region. The mountain chain situated towards the north and northwest acted as a barrier to the spreading of the disease. The hypothesis that the etiological agent, arbovirus Rocio, must have infected the human population recently, having been veiculated to man from forest reservoirs, birds and small mammals, by wild mosquitoes, was considered. Probable forms of domiciliar transmission of the arbovirosis which ocurred in a significantly smaller number of cases were also discussed. It was verified that the population groups which presented the worst forms of the disease were those at extreme ages and those under worst living conditions. It was considered that the epidemiological perspective of the arbovirosis is that it ought to persist in the area, as it presents excellent conditions for the development of the etiological agent, reservoirs and biological vectors, besides continuously receiving susceptible people, migrants or tourists.