Studies on tick pyaemia with special reverence to tramsmission and immunity

PART I. The relationship between tick infestation and the incidence of tick pyaemia in two tick -infested districts is discussed. The evidence obtained tends to confirm the opinion that tick -bite is a causal factor in the production of this disease.PART II.1. The results of experiments with infected ticks showed that the tick is unlikely to act as a true vector of the causal staphylococcus in tick pyaemia. In ticks infected by feeding on an animal suffering from a staphylococcal septicaemia, the infection did not survive the moulting period.2. Haemolytic staphylococci were found to be of common occurrence in the natural orifices of ewes and on the skins of lambs.3. The staphylococci from the above sites were shown to have the same characteristics as the staphylococci from tick pyaemia cases.4. A staphylococcal septicaemia was produced in one lamb by feeding ticks on skin contaminated with staphylococcal culture. The possible influence of tick -borne fever on the development of tick pyaemia is discussed.5 . An examination of the manner in which the staphylococcal infection becomes generalised is made. An investigation of the properties of tick salivary gland secretion is recorded.6 . A preliminary study of the pathology of tickbite is made.PART III. Staphylococcal toxoid administered either to the lamb or to the ewe before lambing was shown to be of no value in the prevention of tick pyaema on Scottish hill sheep farms

The social significance of Joseph Charles Price and his times (1854-1893)

Thesis (M.A.)--Boston University, 1939. This item was digitized by the Internet Archive

Effects of Irritant Chemicals on Aedes aegypti Resting Behavior: Is There a Simple Shift to Untreated “Safe Sites”?

Aedes aegypti, the primary vector mosquito of dengue virus, typically lives near or inside human dwellings, and feeds preferentially on humans. The control of this mosquito vector remains the most important dengue prevention method. The use of chemicals at levels toxic to mosquitoes is currently the only confirmed effective adult vector control strategy with interventions usually applied following epidemic onset. However, research indicates that sub-lethal chemical approaches to prevent human-vector contact at the house level exist: contact irritancy and spatial repellency. The optimum efficacy of an intervention based on contact irritant actions of chemicals will, however, require full knowledge of variables that will influence vector resting behavior and thereby chemical uptake from treated sources. Here we characterize the resting patterns of female Ae. aegypti on two material types at various dark:light surface area coverage ratios and contrast configurations under chemical-free and treated conditions using a laboratory behavioral assay. Change in resting behavior between baseline and treatment conditions was quantified to determine potential negative effects of untreated surfaces (“safe sites”) when irritant responses are elicited. We show that treatment of preferred resting sites with known irritant compounds do not stimulate mosquitoes to move to safe sites after making contact with treated surfaces

Variant -and individual dependent nature of persistent Anaplasma phagocytophilum infection

<p>Abstract</p> <p>Background</p> <p><it>Anaplasma phagocytophilum </it>is the causative agent of tick-borne fever in ruminants and human granulocytotropic anaplasmosis (HGA). The bacterium is able to survive for several months in immune-competent sheep by modifying important cellular and humoral defence mechanisms. Little is known about how different strains of <it>A. phagocytophilum </it>propagate in their natural hosts during persistent infection.</p> <p>Methods</p> <p>Two groups of five lambs were infected with each of two <it>16S </it>rRNA gene variants of <it>A. phagocytophilum</it>, i.e. <it>16S </it>variant 1 which is identical to GenBank no <ext-link ext-link-id="M73220" ext-link-type="gen">M73220</ext-link> and <it>16S </it>variant 2 which is identical to GenBank no <ext-link ext-link-id="AF336220" ext-link-type="gen">AF336220</ext-link>, respectively. The lambs were infected intravenously and followed by blood sampling for six months. <it>A. phagocytophilum </it>infection in the peripheral blood was detected by absolute quantitative real-time PCR.</p> <p>Results</p> <p>Both <it>16S </it>rRNA gene variants of <it>A. phagocytophilum </it>established persistent infection for at least six months and showed cyclic bacteraemias, but variant 1 introduced more frequent periods of bacteraemia and higher number of organisms than <it>16S </it>rRNA gene variant 2 in the peripheral blood.</p> <p>Conclusion</p> <p>Organisms were available from blood more or less constantly during the persistent infection and there were individual differences in cyclic activity of <it>A. phagocytophilum </it>in the infected animals. Two <it>16S </it>rRNA gene variants of <it>A. phagocytophilum </it>show differences in cyclic activity during persistent infection in lambs.</p