Natural Ehrlichia ruminantium infection in two captive Arabian tahrs (Arabitragus jayakari) in Oman.

This study was investigated the cause of death of two captive adult Arabian tahrs (Arabitragus jayakari) died within 2-3 days after onset of fever and neurologic signs in a private farm in northern Batinah Region of Oman. Blood counting revealed leukocytosis attributed to neutrophilia and serum chemistry showed hypoproteinemia, increased creatine kinase and BUN. Upon autopsy, the animals exhibited mild ascites and hydrothorax, prominent hydropericardium, with large pale-yellow clear fluid coagulum, prominent epicardial petechiation, as well as severe pulmonary edema associated with frothy fluid in airways. Brain edema with congestion of meningeal and parenchymal vessels was prominent. Histopathology revealed severe congestion and edema of both lung and brain as well as cardiac myopathy. Ehrlichia ruminantium colonies (the causative organism of cowdriosis; OIE-listed disease) were demonstrated in the capillary endothelium of fresh brain squash and lung macrophages. This is the first report of natural E. ruminantium infection in Arabian tahr, the highly endangered species, based on typical clinical signs of acute cowdriosis and demonstration of E. ruminantium colonies in the brain capillary endothelial cells.

Innate immune transcriptomic evaluation of PBMC isolated from sheep after infection with E. ruminantium Welgevonden strain.

Heartwater is a tick-borne non-infectious fatal disease of wild and domestic ruminants caused by the bacterium Ehrlichia ruminantium, transmitted by Amblyomma ticks. Although there is evidence that interferon-gamma (IFN-γ) controls E. ruminantium growth and that cellular immune responses could be protective, an effective recombinant vaccine for this disease is lacking. An overall analysis of which immune pathways are up- or down-regulated in sheep peripheral blood mononuclear cells is expected to lead to a better understanding of the global immune response of sheep to E. ruminantium infection. Therefore, a systems biology oriented approach following the infection with E. ruminantium was investigated from peripheral blood mononuclear cells to aid recombinant vaccine development. In this study, heartwater naïve sheep were infected and challenged by allowing E. ruminantium infected ticks to feed on them. After primary infection, all the animals were treated with antibiotic during the resulting febrile response. Blood was collected daily for E. ruminantium detection by qPCR (pCS20 assay). The pCS20 assay only detected the pathogen in the blood one day prior to and during the febrile stage of infection confirming infection of the sheep. IFN-γ real-time PCR indicated that this cytokine was expressed at specific time points: post infection, during the febrile stage of the disease and after challenge. These were used as a guide to select samples for transcriptome sequencing. This paper focuses on transcripts that are associated with innate activating pathways that were identified to be up- and down-regulated after primary infection and the subsequent challenge. These included the CD14 monocyte marker, toll-like receptor (TLR), nod-like receptor, chemokine, cytosolic and cytokine-cytokine interaction receptor pathways. In particular, TLR4, TLR9 and CD14 were activated together with DNA detection pathways, suggesting that vaccine formulations may be improved if CpG motifs and lipopolysaccharides are included. This data indicates that innate immune activation, perhaps by using adjuvants, should be an important component for consideration during future heartwater recombinant vaccine development.

Emerging tick-borne disease in African vipers caused by a Cowdria-like organism.

Heartwater is a tick-borne infectious disease caused by the rickettsial organism Cowdria ruminantium, currently Ehrlichia ruminantium. It poses an imminent threat to the Western Hemisphere, where it could cause mortality in cattle and other ruminant livestock in excess of 70%. It has been reported in the Caribbean; and its vector, Amblyomma sparsum, has been found on imported African spurred tortoises (Geochelone sulcata) and leopard tortoises (Geochelone pardalis) in southern Florida in the United States, leading to an importation ban on these reptiles. Symptoms have not been previously reported in reptiles. Here, we report peracute and acute deaths in African vipers imported from Africa through Florida. Signs included vomiting mucoid fluid, diarrhea, emaciation, convulsions, and death. Postmortem showed few gross lesions. The most consistent peracute and acute lesions were the pulmonary lesions and pericarditis with considerable bloody fluid in the pericardial sac (hydropericardium). These lesions strongly resembled the lesions of heartwater and a coccobacillus of less than 1-micron diameter was isolated in viper cell culture. The outbreak was brought to a halt by tick control and treatment of all exposed snakes with tetracycline. This isolation, tetracycline sensitivity, clinical signs, preliminary results with polymerase chain reaction of pCS20 ORF, and the viper preference of the disease may indicate a Cowdria-related attenuated species that has adapted to infect reptiles or an emerging new form of this group of microbes.

Possible death of a buffalo calf (Syncercus caffer) due to suspected heartwater (Ehrlichia ruminantium).

Rickettsial organisms resembling Ehrlichia ruminantium (the causative organism of heartwater) were demonstrated in brain smears and formalin-fixed brain sections derived from a buffalo calf that died on a private game reserve in northern KwaZulu-Natal. The possibility that the tick-free environment of a quarantine boma may have affected the calf's immunity, is discussed. These findings suggest that monitoring heartwater in wild ruminants and making brain smears as a routine during post mortem evaluations of wild ruminants, should be encouraged.

Electron microscopy of Cowdria-infected macrophages suggests that in the absence of binary fission a mosaic of organisms develops from an amorphous electron dense matrix.

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.

In vitro isolation and cultivation of Cowdria ruminantium under serum-free culture conditions.

Three stocks of Cowdria ruminantium, the causative agent of heartwater in domestic ruminants, were propagated in bovine endothelial cells in a serum-free culture medium. The Vosloo, Welgevonden and Senegal stocks were propagated for a period of more than 203, 134, and 43 days, respectively. Two of the C ruminantium stocks (Vosloo and Senegal) were also successfully initiated under serum-free culture conditions. The serum-free medium consisted of a modified HL-1 medium. The Senegal stock was successfully propagated in Dulbecco's modified Eagle's medium nutrient mixture Ham F-12 containing 10 per cent fetal bovine serum.

Experimental Trypanosoma congolense infection on naturally occurring ticks in N'dama and Gobra zebu cattle.

The effects of experimental Trypanosoma congolense infection in Gambian N'dama and Gobra zebu cattle on number of naturally-occurring adult ticks attaching were studied. An indirect fluorescent antibody test was performed to detect serological prevalence of Cowdria ruminantium antibody. The intravenously imposed trypanosome infection did not result in significant (P > 0.05) differences in Amblyomma variegatum and Hyalomma spp. infestations between control and infected N'dama cattle. Control N'damas carried significantly (P < 0.001) lower numbers of A. variegatum and Hyalomma spp. than the control zebus. Serological frequency of C. ruminantium antibody was similar in both control or infected N'dama and in control or infected zebu cattle. No deaths occurred among N'dama cattle, while all six trypanosome infected zebus progressively died within nine weeks post-infection but trypanosomosis was excluded as the primary cause of death. Examined Giemsa-stained blood smears were negative for the presence of tick-borne micro-organisms. Four positive cases of cowdriosis were identified during post-mortem examination. It was concluded that N'damas, even when submitted to trypanosome infection, react consistently better than Gobra zebus to tick attachment. These results emphasize the benefits of rearing disease resistant cattle breeds, such as N'dama, in areas where risks of trypanosomosis and cowdriosis coexist.

Histologic and immunochemical study of the pathogenesis of heartwater (Cowdria ruminantium infection) in goats and mice.

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.

The pathology of heartwater. III. A review.

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.

Diagnosis of heartwater at post-mortem in ruminants and the confirmation of Cowdria ruminantium in mice.

Criteria that are required to confirm heartwater in ruminants and mice are discussed. In ruminants it entails the macroscopical and microscopical lesions as well as the identification of Cowdria ruminantium in brain smears or histological sections. Macroscopical lesions in the majority of animals that die of the disease include effusion of body cavities, hydropericardium, oedema of the lungs, brain, mediastinum, and its associated lymph nodes, and splenomegaly. The effect of specific chemotherapy on the morphology of heartwater organisms in vivo is outlined. A severe nephrosis in heartwater-infected Angora goats, treated after the first day of the febrile reaction, is described.

Susceptibility of white-tailed deer to experimental heartwater infections.

Nine white-tailed deer (Odocoileus virginianus) were experimentally infected with Cowdria ruminantium, the causal agent of heartwater. All deer developed clinical signs; one was killed, one was treated, and seven died within 2 wk postinoculation. Diagnosis of heartwater was based on clinical signs, postmortem lesions and by microscopic observation of C. ruminantium in endothelial cells of brain capillaries of dead animals. Cowdria ruminantium was passaged by collecting blood from deer at the height of the febrile response and intravenous inoculation of susceptible deer and goats. Tetracycline was effective in the treatment of heartwater in a deer.

The pathology of heartwater. I. A study of mice infected with the Welgevonden strain of Cowdria ruminantium.

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.

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.

Heartwater in Angora goats. II. A pathological study of artificially infected, treated and untreated goats.

Pathological lesions in untreated Angora goats infected with the Ball3 strain of Cowdria ruminantium corresponded with those previously reported. A severe nephrosis was the most prominent pathological lesion in the animals treated after the 1st day of the febrile reaction. Renal ischaemia appears to be central to the pathogenesis of the kidney lesions.

Clinico-pathological study of heartwater in goats.

The clinico-pathological features of heartwater were studied in goats experimentally infected with a Nigerian isolate of Cowdria ruminantium. Significant drop in haemoglobin values and marked leukopaenia caused by lymphopaenia and neutropaenia and a fall in total serum protein were observed during the course of the disease. A significant increase in the alpha-globulins and an apparent fall in the gamma-globulins also occurred. Marked depletion of lymphocytes in the follicles of spleen and lymph nodes was observed in histological sections. A dramatic rise in blood levels of glucose, pyruvate and lactate, and a drop in blood pH occurred terminally and appeared to contribute to the fatal outcome of the disease.

[Newer veterinary neuropathological conditions in South Africa (author's transl)]. / Nuwere veterinêre neuropatologiese toestande in Suid-Afrika.

A brief review is given of some of the more recent findings on lesions of diseases affecting the central nervous system of animals. These include local diseases caused by poisonous plants; Helichrysum argyrosphaerum, Solanum kwebense, Matricaria nigellaefolia; infectious diseases e.g. heartwater, cerebral babesiosis and cranial abscesses in goats caused by Corynebacterium pyogenes. Reference is also made to some conditions, originally described in overseas countries and which subsequently have been diagnosed in South Africa. Original findings on lesions seen in mycotoxicoses caused by Fusarium moniliforme and Aspergillus clavatus are included.