An in vitro test to demonstrate the inhibitory effect of homologous immune serum on the infectivity of Cowdria ruminantium

Homologous immune sheep serum inhibits the infectivity of mice for the Kumm stock of Cowdria ruminantium in an in vitro test. The presence of complement and an optimal ratio between the reagents are of cardinal importance. With the exception of the Ball 3 stock, there is no cross-inhibition between the immune sera of sheep infected with several other heterologous stocks and the Kumm stock. The role played by the humoral component of the immune response in naturally acquired heartwater is unknown, but probably small compared to the cellular component.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

The natural resistance of cattle to artificial infection with Cowdria ruminantium: the role played by conglutinin

The conglutinin titres of year-old Bonsmara-cross cattle infected with Cowdria ruminantium were inversely proportional to the severity of the reactions elicited by the infection. There was no correlation, however, between conglutinin levels of 8-month-old calves of the same breed, sex and origin and their susceptibility to heartwater. The role possibly played by conglutinin in the non-specific resistance of cattle to heartwater and in the epidemiology of the disease is discussed.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Increased pathogenicity of an Ehrlichia-like agent after passage through Amblyomma hebraeum : a preliminary report

After being passaged through 3 generations of Amblyomma hebraeum, an Ehrlichia-like agent isolated from an adult Hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater. Cross-immunity between this agent and several stocks of Cowdria ruminantium and high levels of antibody elicited by the agent against 2 stocks of C. ruminantium in the indirect fluorescent antibody test, confirmed its close relationship to Cowdria.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

The influence of dithiosemicarbazone on the immunity of sheep to heartwater

Four out of 9 sheep, immune to heartwater and subsequently treated with gloxazone, showed a febrile reaction when they were challenged 6 months later, but the same number of untreated controls also developed this reaction. In a second group of treated immune animals challenged after 9 months, 8 out of 8 showed a febrile reaction, whereas only 3 out of 8 controls reacted. Furthermore, the blood of one of the 4 sheep that reacted to challenge at 6 months was infective to a susceptible sheep inoculated with it, whereas that of 4 out of the 8 challenged at 9 months was infective.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Pathogenesis of heartwater. I. Cowdria ruminantium in the lymph nodes of domestic ruminants

The intracellular replication of Cowdria ruminantium (Cowdry, 1926) is described in reticulum cells of lymph nodes several days prior to the appearance of rickettsial colonies in vascular endothelial cells. This is suggestive of a developmental cycle of the parasite in the lymph nodes. The subinoculation of suspensions of these glands resulted in transmission of the disease.The journals have been scanned in colour with a HP 5590 scanner; 600 dpi. Adobe Acrobat v.11 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.

Colostrum-derived antibodies to Cowdria ruminantium in the serum of calves and lambs

Antibodies to Cowdria ruminantium were detected in the serum of calves born from artificially immunized heifers, by means of the indirect fluorescent antibody test, only for as long as 4 weeks after birth. Lambs born from artificially immunized ewes, however, were still serologically positive at 8-12 weeks of age. Much higher antibody titres were recorded in the sera of ewes and their lambs than in that of heifers and their calves.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.am201

A method for determining the Cowdria ruminantium infection rate of Amblyomma hebraeum: effects in mice injected with tick homogenates

Amblyomma hebraeum ticks, collected in the field and individually homogenized, were injected into mice. Thirteen out of 240 ticks were shown to be infected with the heartwater agent. Antibodies against Cowdria ruminantium were detected in the sera of the mice by means of the indirect fluorescent antibody test. Giemsa stained smears, prepared from the haemocytes of the ticks, revealed morphologically different forms of the heartwater agent. A strain of C. ruminantium, designated the Welgevonden strain, was isolated in mice from one of the infected ticks and passaged in mice for 8 generations. When inoculated intravenously, it was highly infective to mice, sheep and cattle. The murinotropism of the Welgevonden strain is compared with that of other strains previously described.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Electron microscopy of Cowdria ruminantium infected reticulo-endothelial cells of the mammalian host

An electron microscopic study of structures suspected to represent a possible developmental cycle of Cowdria ruminantium in reticulo-endothelial cells of mice and ruminants is reported. After infection dense bodies increase in size and undergo division to form fragmented dense bodies. These in turn apparently sub-divide and become organized to give rise to mature "organisms". In none of these structures do limiting membranes separate the parasitic inclusions from the host cell cytoplasm. Present observations suggest that growth of the organism in reticulo-endothelial cells differs from that of chlamydial and rickettsial agents and somewhat resembles the replication of some viruses. Developmental stages observed after infection of ruminants with the Ball 3 strain of the heartwater agent are indistinguishable from those seen with the mouse adapted strain. These observations support the hypothesis that C. ruminantium released from reticulo-endothelial cells subsequently penetrates endothelial cells where further multiplication by binary fission occurs.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acroabt XI was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

The pathology of heartwater. II. A study of the lung lesions in sheep and goats infected with the Ball₃ strain of Cowdria ruminantium

Lung lesions in sheep and goats infected with the Ball₃ strain of Cowdria ruminantium corresponded with those reported in mice infected with the Welgevonden strain of Cowdria ruminantium. Ultrastructural changes in the alveolar endothelial and epithelial cells are described and the pathogenesis of the lung oedema is briefly discussed.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Susceptibility to heartwater of calves born to non-immune cows

The resistance to artificical infection with Cowdria ruminantium of calves born to cows fully susceptible to heartwater is no different from that of calves bred in heartwater endemic areas where the tick challenge is negligible to considerable. The sub-inoculation into mice of blood collected 14-26 days after infection proved the presence of the heartwater agent in the blood of 8 out of 10 calves with no other clinical signs than mild to moderate fever. The combined use of a mouse model and the indirect fluorescent antibody test revealed considerable variation in the degrees to which calves become infected and react to artifical infection.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201