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1.
Serum samples collected on a single occasion from cattle, sheep and goats at sites in all 10 regions of Ghana were tested for antibodies to Ehrlichia (previously Cowdria) ruminantium, the causative agent of heartwater, by polyclonal competitive ELISA (PC-ELISA). The survey revealed the presence of heartwater-exposed ruminants throughout the country, with local seroprevalence up to 100%. Seronegative, and therefore presumably susceptible, animals were also present in all regions, in some areas in numbers high enough to indicate local endemic instability. Overall seroprevalences in cattle, sheep and goats were 61, 51 and 28% respectively, and were generally higher in the northern part of the country and lower in the forest zone. Amongst animals over 1 year old, two thirds of cattle and sheep, and around one third of goats throughout the country had been exposed to E. ruminantium. In the north, seroprevalence in sheep sampled with and without cattle was similar, whereas in the south seroconversion rates in sheep were significantly higher in areas where cattle were present.  相似文献   

2.
Creole goats and cattle in Guadeloupe can be carriers of cowdriosis (heartwater: Cowdria ruminantium) after recovery for a period as long as 11 months in goats and 2 months in cattle. The carrier status was demonstrated by feeding Amblyomma variegatum nymphs on recovered animals and the resulting adult ticks on susceptible goats. Cowdria ruminantium was not detected permanently during the carrier status.  相似文献   

3.
Amblyomma hebraeum male and female ticks, experimentally infected as larvae with the Ball 3 stock of Cowdria ruminantium, were fed on a heartwater susceptible sheep. The initial attachment of the males was required as a pre-requisite for female attachment. Reticulate bodies were the predominant morphologic form of Cowdria observed in gut epithelial cells after 1-3 days of feeding. Single intermediate bodies and no elementary bodies were observed. Organisms were found within a membrane-bound vacuole and each organism had a double-unit membrane. Infrequently colonies contained homogeneous electron-dense inclusions. Groups of Cowdria organisms within a haemocyte suggested a possible dissemination of organisms from the gut to various other tissues by haemocytes.  相似文献   

4.
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.  相似文献   

5.
Gross and microscopical lesions in mice intravenously infected with the Welgevonden strain of Cowdria ruminantium closely resembled the lesions described in cattle, sheep and goats. A high concentration of organisms was present in alveolar endothelial cells. Cytopathic changes in parasitized and non-parasitized endothelial cells and the morphology of the organisms are described and compared with the Ball3 strain of C. ruminantium. Possible mechanisms in the development of the lung oedema are considered and the role of mice as animal model is discussed.  相似文献   

6.
A capillary flocculation test was developed to diagnose heartwater disease of ruminants. Antigen was prepared from the brains of cattle and goats highly infected with Cowdria ruminantium. Sera were obtained from experimentally infected ruminants which either recovered naturally or with the aid of oxytetracycline treatment. Antibodies were first detected one to two weeks after clinical recovery or after treatment, and persisted for periods varying between one and four weeks. Control sera collected from cattle (sheep) and goats in the Netherlands where heartwater does not occur, or from animals serologically positive for Anaplasma marginale or Eperythrozoon ovis infections, did not react to the test.  相似文献   

7.
The development of colonies of Cowdria ruminantium was studied in midgut epithelial cells of adult Amblyomma variegatum that had become infected by feeding as nymphs on cattle with experimentally induced heart-water disease. Colonies were not observed in gut tissues obtained from nymphs during the feeding period, but were present in midgut epithelial cells of ticks obtained at 15 days after they were replete through molting to the adult stage. Colonies were small (1 to 10 micron) initially, but as tick development progressed, their diameter increased to as much as 60 micron. With electron microscopy, colonies were observed to be membrane bound and contained pleomorphic organisms that were reticulated. The organisms seemed to be dividing by binary fission. Many colonies contained a large, electron-dense inclusion that was morphologically similar to hemoglobin deposits found in the cytoplasm of midgut epithelial cells of recently fed ticks. Cowdria ruminantium was often observed adhered to these inclusions.  相似文献   

8.
Nineteen per cent and 32% of serologically positive sheep and goats in heartwater endemic areas of the Republic of South Africa were susceptible to challenge with, respectively, the Ball 3 and Welgevonden stocks of Cowdria ruminantium. There was good correlation between the results of the indirect fluorescent antibody test and immunity, since without exception all the seronegative animals reacted when they were challenged. The fact that only 74% of the seropositive sheep and goats were immune to challenge can probably be ascribed to the poor cross-protection between stocks of C. ruminantium and not to false positive serological reactions.  相似文献   

9.
Antigenic diversity in five stocks of the tick-borne rickettsia Cowdria ruminantium, the causal agent of heartwater disease of ruminants, was studied by cross-immunity trials in goats and sheep. Complete absence of cross-protection was found only between the Kümm and Kwanyanga stocks, and in all other combinations there were various degrees of cross-immunity. Immunological strain differences were more pronounced in goats than in sheep.  相似文献   

10.
The pathology of heartwater. III. A review   总被引：1，自引：0，他引：1  
The pathological changes in cattle, sheep, goats, mice and various game species infected with Cowdria ruminantium are summarized. Macroscopical lesions in most animals include effusion of body cavities, oedema of the lungs and lymph nodes and splenomegaly. Apart from the presence of heartwater organisms in most organs the histopathological lesions are not striking. The ultrastructural lesions in the lungs of sheep and goats infected with the Ba11 3 strain of heartwater, and mice infected with the Welgevonden strain, are discussed. Damage to capillary endothelial cells of the alveoli is limited and the mild cytopathic changes in parasitized cells indicate that the damage caused by the organisms is most probably not responsible for the increased vascular permeability associated with the disease. Pathological changes in domestic ruminants and game animals are briefly compared.  相似文献   

11.
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.  相似文献   

12.
Notwithstanding morphological differences, the ultrastructure of Cowdria ruminatium cultured in vitro concurred to a large extent with that in previous in vivo studies. Two distinct forms of the organism, elementary and reticulate bodies, and a 3rd group of intermediate organisms were identified. Organisms within a particular vacuole were generally a specific form, but in cells containing many colonies different forms were present in the same colony. Most organisms were enveloped by 2 membranes and a few were surrounded by a 'capsule'. C. ruminantium multiplies mainly by binary fission, but it appears that multiplication can also take place by means of budding. The taxonomy of C. ruminantium is briefly discussed.  相似文献   

13.
Heartwater in the Caribbean: isolation of Cowdria ruminantium from Antigua   总被引：5，自引：0，他引：5  
Adult Ambylomma variegatum ticks were collected from 184 cattle, 13 sheep and one goat in Antigua, and ground in phosphate buffered saline. The resultant supernates were cryopreserved in liquid nitrogen. Five supernate pools, each derived from approximately 100 ticks collected from different herds, were thawed and each was inoculated intravenously into a separate experimental goat. One goat exhibited a febrile response with Cowdria ruminantium demonstrable in brain biopsies; after recovery, this animal showed no reaction to a lethal challenge with a Guadeloupe isolate of C ruminantium.  相似文献   

14.
The morphology of Cowdria ruminantium is described and its staining characteristics in the vertebrate host and in vitro are summarized. Morphologically, the organisms are characterized in the cytoplasm of endothelial cells, macrophages and reticulo-endothelial cells. Based on the morphology of the internal structure of the organisms, elementary (electron-dense), intermediate and reticulate bodies are identified. Each organism is surrounded by a double membrane and a "capsule" is evident around a few organisms in vitro. Usually, only organisms of the same form are found within a particular vacuole, although mixed colonies are described in the in vitro studies.  相似文献   

15.
The development of the tick-borne rickettsial pathogen Cowdria ruminantium (S stock) was studied in bovine umbilical endothelial (BUE) cell cultures and in goat choroid plexus, by light- and electron microscopy. Cowdria divided by binary fission within intracytoplasmic vacuoles resulting in large colonies of reticulate bodies. After three to four days in culture, reticulate bodies developed into smaller intermediate bodies characterized by an electron-dense core. Shortly before disruption of the host cells, intermediate bodies condensed further into electron-dense elementary bodies, which were released into the culture medium. Elementary bodies invade other endothelial cells thus initiating a new infectious cycle which lasts between 5 and 6 days. In the infected goat choroid plexus similar reticulate and intermediate bodies were identified within vacuoles of capillary endothelial cells. However, extracellular elementary bodies were not detected. Another stock of Cowdria (W) showed an identical developmental cycle as that of the S stock. The W isolate was also pathogenic for mice, making it possible to test the infectivity of reticulate and elementary bodies in these animals. Reticulate bodies appeared to be less infective than elementary bodies. The developmental cycle of Cowdria resembles the cycle known to occur in Chlamydia. Moreover, Cowdria has other similarities with Chlamydia. It has a Gram-negative envelope, it does not store iodine-stainable carbohydrates and may lack peptidoglycan as does Chlamydia. It is concluded, that Cowdria and Chlamydia are to a certain extent related, confirming a recent report that both organisms have certain antigenic determinants in common. Since Cowdria is also related to Ehrlichia it may well be that Cowdria takes an intermediate position between Chlamydia and Ehrlichia. The phylogenetic relationship between Cowdria and Chlamydia and also with Ehrlichia should be further elucidated by molecular analysis using 16S ribosomal DNA sequences.  相似文献   

16.
Mallory's phloxine-methylene blue stain was used to differentiate colonies of Cowdria ruminantium in midgut epithelial cells of nymphal Amblyomma hebraeum that had been infected as larvae. Gut tissues were collected from nymphs that had fed on a susceptible sheep and were fixed in formol-saline on the day of repletion. Paraffin sections, 3-4 micron thick, were then stained and this rendered colonies and cell nuclei densely blue against a uniformly pink background of tick tissues. Colonies were easily distinguished from nuclei by their specific morphology. This method of parasite visualization may be adapted to field-collected ticks for rapid detection of C. ruminantium or to assays of susceptibility of tick populations to various strains of the organism.  相似文献   

17.
Hybridomas producing monoclonal antibodies (mAb) to Cowdria ruminantium were raised. Four mAbs of the IgG isotype reacted in western blots with a 32-kilodalton Cowdria protein (Cr32), which had previously been shown to be conserved and immunodominant. A fifth mAb of the IgM isotype recognized a 40-kDa Cowdria protein. The latter mAb was negative in an indirect fluorescent antibody test (IFA), whereas the other four were positive. mAb No. 4F10B4 showed the strongest signal in western blots using three different stocks of Cowdria. Immuno-gold labeling of Cowdria organisms in vitro using 4F10B4 showed that Cr32 has surface-exposed antigenic determinants. Using mAb 4F10B4, a competitive ELISA was developed which detected specific Cowdria antibodies in goat, sheep and cattle sera. Antibodies in animal sera competed with binding of mAb 4F10B4 to a crude sonicated Cowdria antigen obtained from infected endothelial cell cultures. The competition ELISA (CELISA) detected antibodies in 55 out of 70 (79%) goats experimentally infected with one of eight different Cowdria stocks. Fourteen out of the 15 sera which were shown negative in the CELISA were also negative in the IFA. Nevertheless, all 15 sera recognized some epitopes of the immunodominant Cowdria-specific 32 kDa protein as judged from their reaction with this protein in western blots. Overall, there was 89% agreement between CELISA and IFA considering all 70 goat sera. Moreover, antibodies were detected in nine out of nine sheep infected with one of three different stocks of Cowdria and in sera from calves experimentally infected by two different strains of heartwater. There were no cross-reactions with Ehrlichia phagocytophila antibodies in goat sera, nor with Anaplasma marginale antibodies in bovine sera. Lack of cross-reactivity and detection of antibodies to eight geographically widely distributed stocks of Cowdria, makes the competition ELISA a promising test for use in heartwater endemic areas.  相似文献   

18.
Eleven adult goats and 32 adult outbred mice were inoculated IV with Cowdria ruminantium-infected blood (Kwanyanga isolate), monitored clinically, then serially euthanatized. Predominant clinical signs of disease in goats were depression, head tremors, seizures, and dyspnea. In mice, dyspnea and depression were the only clinical signs of disease noticed. Tissues were examined histologically and immunohistochemically for C ruminantium colonies or antigen. In goats, C ruminantium was detected only in endothelial cells of the brain, even though gross and microscopic lesions were confined to the thorax. In mice, C ruminantium was detected only in endothelial cells of the heart and lungs.  相似文献   

19.
Electron microscopy of mouse peritoneal macrophages infected with the Kümm stock of Cowdria ruminantium suggests that in the final stage of intracellular growth, a mosaic of organisms develops from an amorphous matrix of varying electron density by a process in which double unit membranes portion off the Cowdria particles. This stage is preceded by inclusions consisting of a network of aggregated electron dense granules and these in turn by homogeneous dense bodies. The study failed to show how these dense bodies develop from internalized Cowdria particles introduced in the infective inoculum. The replication of the heartwater agent in macrophages differs from that in vascular endothelial cells in two important respects. First, at no stage during the course of development in macrophages is binary fission in evidence and second, in the absence of a limiting membrane the inclusions and colonies of organisms throughout the cycle of development in macrophages are in intimate contact with the host cell cytoplasm.  相似文献   

20.
Various aspects of the development and life cycle of Cowdria ruminantium are discussed. C. ruminantium is transmitted transstadially by certain Amblyomma species. Apparently organisms initially develop in the gut epithelial cells of ticks and subsequent stages of C. ruminantium invade and develop in the salivary gland acini cells of the vector. Stages at which transmission to the final host are attained appear to be coordinated with the feeding cycle of the ticks and the vertebrate host is infected via salivary glands of the tick. In the vertebrate host, ticks and cultured endothelial cells, different morphological forms of C. ruminantium (electron-dense and reticulated forms) are found. Organisms enter cells through a process resembling phagocytosis and reticulated forms of the organisms appear to be the main vegetative stage. In the vertebrate host, organisms proliferate in vascular endothelial cells, neutrophils, macrophages and reticulo-endothelial cells.  相似文献   

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