Bovine babesiosis: vaccination against tick-borne challenge exposure with culture-derived Babesia bovis immunogens.
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Biomedical subjects
M Ristic
Publications and source records attributed to M Ristic.
In vitro cultivation of Anaplasma marginale: growth pattern and morphologic appearance.
Anaplasma marginale propagated in vitro showed an increasing rate of replication in a sequence of three experiments. The changes in the percentage of parasitized erythrocytes and identification of the organism in culture were monitored by the Giemsa-staining and the direct fluorescent antibody techniques. The ultrastructure of the organism in culture also was determined. The percentage of parasitized erythrocytes increased more than three times in the first experiment during a period of 8 days, and about ten times in the second experiment during a period of 14 days. After 8 days of observation of the primary culture in the third experiment, the trend of growth was more rapid than in the first and second experiment. The viability of the organism was verified by inoculation of susceptible calves, using 13- and 33-day cultures of the first and the second experiments, respectively. The primary cultures were subcultured twice by dilution with normal bovine erythrocytes.
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In vitro cultivation of Anaplasma marginale: invasion of and development in noninfected erythrocytes.
Ovine erythrocytes infected with attenuated Anaplasma marginale organisms were cultured in a suspension of normal ovine erythrocytes and normal bovine erythrocytes for 42 days. In each system, the organism showed an initial period of rapid growth followed by a gradual decrease in the percentage of parasitized erythrocytes accompanied by cyclic peaks. The percentage of infection of ovine erythrocytes were not different when normal ovine or bovine erythrocytes were added to the cultures. In vitro transmission of the organism from infected ovine cells to normal bovine cells was demonstrated by use of a two-step direct fluorescent antibody method, which allowed for specific identification of the two cell types and the organism.
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Prophylactic and therapeutic use of tetracycline during an epizootic of ehrlichiosis among military dogs.
An epizootic of canine ehrlichiosis at the Military Working Dog Center, Pakchong, Thailand, was arrested by prophylactic and therapeutic use of tetracycline and by control of ticks. Oral treatment with tetracycline (66 mg/kg of body weight daily for 14 days) effected remission of signs of disease in 60 of 62 clinically affected dogs and resulted in disappearance of serum antibody in 119 (60%) of 198 seropositive dogs treated during the 2-year study period. Transmission of Ehrlichia canis was interrupted by control of ticks and by daily oral administration of tetracycline at a dosage of 6.6 mg/kg of body weight. When the control program was initiated, 100 (57%) of 174 dogs were seropositive, with one-third of these manifesting clinical signs of ehrlichiosis. The proportion of seropositive reactions progressively decreased to 11% after control was established, and the impact of the disease on health and performance of the dogs was greatly reduced. Eight dogs died before institution of control. Two additional dogs died within the first 2 months after control was established. There was no mortality thereafter.
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Retrospective study of an Ehrlichia canis epizootic around Phoenix, Arizona.
Antibodies to Ehrlichia canis were detected by indirect immunofluorescence in sera from 40 of 339 dogs (12%) examined from around Phoenix, Az, during 1975. The prevalence was higher in purebred and crossbred German Shepherd Dogs (21%), as compared with 8% in the remaining breeds. The difference in antibody prevalence between sexes was not significant. Dogs 12 weeks to 13 years old were seropositive. The causative agent was isolated by inoculation of whole blood from a seropositive dog into a susceptible German Shepherd Dog.
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Pathobiology of Borrelia theileri in the tropical cattle tick, Boophilus microplus.
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Platelet migration inhibtion as an indicator of immunologically mediated target cell injury in canine ehrlichiosis.
A platelet migration inhibition test was devised to determine the presence of antiplatelet activity in serum collected from experimentally produced and natural cases of canine ehrlichiosis. The maximum platelet migration inhibition effect was observed during the acute phase of the disease and before the appearance of specific humoral antibody, measured by the indirect fluorescent-antibody test. Platelet migration inhibition may be one of the earliest events leading to pancytopenia. In most cases, sera positive for humoral antibodies also were positive for platelet migration inhibition, although no direct correlation was evident between the serological titer and the degree of platelet migration inhibition. Inoculation of dogs with uninfected canine blood did not induce the production of inhibition factor or antibody activity, which precluded a histocompatibility response to the cellular elements in the inoculum. Scanning electron microscopy indicated that the platelet inhibition factor interfered with platelet migration by inhibiting pseudopod formation. Affected platelets became rounded and showed evidence of clumping and leakage.
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Growth of Babesia bovis in bovine erythrocyte cultures.
Babesia bovis was cultured in a suspension of bovine erythrocytes incubated at 37 degrees C in Medium 199 with 50% bovine serum. The cells in culture were kept in suspension by slow stirring in spinner flasks and the medium was replaced at 24-hour intervals. Persistent multiplication of the parasite in a short series of subcultures suggests the feasibility of this approach for continuous culture.
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Immune response of ponies to experimental infection with Ehrlichia equi.
Four ponies experimentally infected with Ehrlichia equi developed substantial cell-mediated immune responses, as measured by the leukocyte migration-inhibition test. Serum anti-E equi antibodies up to 1:1,280 were demonstrated by the indirect fluorescent antibody test. Cell-mediated immune responses returned to a base-line value by day 200 after primary inoculation, but serum antibody titers persisted for at least 300 days after inoculation. Two additional susceptible ponies, which were inoculated with convalescent blood or organ homogenates from ponies recovered from acute equine ehrlichiosis, treated with tetracycline, and subsequently challenge exposed with E equi-infective blood, did not develop clinical disease. This study suggested that ponies are resistant to reinfection with E equi following clinical ehrlichiosis.
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Effect of canine immune serum on the growth of Ehrlichia canis within nonimmune canine macrophages.
The effect of canine immune serum (CIS) on the growth of Ehrlichia canis was studied in macrophage cultures derived from peripheral blood monocytes of normal dogs. Ehrlichiae treated with canine normal serum and then introduced into normal macrophage cultures maintained in canine normal serum multiplied within the macrophages and destroyed them. Immune serum, collected from E canis carrier dogs, suppressed ehrlichial growth in normal macrophages. An inverse relationship existed between the amount of CIS to which ehrlichiae were exposed and the growth of the organism in normal macrophages. The anti-E canis activity was most prevalent in the 7-S fraction of immune serum. Fresh CIS had a greater suppressive effect on the growth of E canis than did heat-inactivated CIS. Antibody cytophilic for canine monocyte-derived macrophages was not detected in CIS.
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Effect of canine immune macrophages and canine immune serum on the growth of Ehrlichia canis.
The effect of canine immune macrophages and canine immune serum (CIS) on the growth of Ehrlichia canis was studied in vitro. Treatment of E canis organisms with CIS before they were inoculated into immune macrophage cultures, coupled with pre- and postinoculation maintenance of cultures in CIS, suppressed macrophage infection rates to 1% or less. Immune macrophages collected from E canis-carrier dogs and maintained in canine normal serum were more resistant to the intracellular growth of E canis than were normal macrophages maintained in the same serum. Ehrlichiae introduced into normal macrophage cultures maintained in canine normal serum multiplied within the macrophages and destroyed them. Maximal immunity to intracellular growth of E canis, maximal destruction of this organism, or both, required the interaction of E canis with both humoral and cellular factors in proper sequence.
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Efficacy of attenuated Anaplasma marginale vaccine under laboratory and field conditions in Colombia.
Four-month-old Holstein-Friesian calves were inoculated with 3 different doses (1, 2, and 3 ml) of attenuated Anaplasma marginale vaccine. Vaccinated calves showed mild anaplasma parasitemia, slight decrease in packed cell volume, low serologic conversion, and no clinical illness. An artificial challenge exposure of vaccinated and unvaccinated calves with virulent Colombian A marginale showed that the vaccine provided protection against clinical signs of the disease, including parasitemia and anemia. The volume of the vaccinal dose did not alter the degree of protection provided. A 2nd group of 8- to 9-month-old Holstein-Friesian calves was then inoculated with 3 ml of anaplasma vaccine and premunized with both Babesia bigemina and Babesia argentina while being housed in an area free of these diseases. Calves were moved to an enzootic region heavily infested with various arthropods, including ticks, for natural field challenge exposure. Control calves, which were not given anaplasma vaccine, suffered clinical illness manifested by severe anemia and an average weight loss of 50.6 kg due to anaplasma field challenge exposure. In contrast, vaccinated calves did not show anemia and their weight loss was 3.9 kg.
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Fluorescein diacetate staining of Anaplasma marginale as a possible measure of viability.
Fluorescein diacetate viability-staining technique was applied to Anaplasma marginale. Marginal bodies took up the stain and became fluorescent. When infected red blood cells were incubated at 55 C, the number of fluorescent Anaplasma decreased at a rate similar to the known loss of viability.
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Bovine babesiosis: severity and reproducibility of Babesia bovis infections induced by Boophilus microplus under laboratory conditions.
A total of 61 intact Holstein-Friesian calves were exposed to Babesia bovis (= B argentina) by the injection of infected blood or the application of infected Boophilus microplus larvae. Tick-induced infections were uniformly severe, even when induced by relatively small numbers of infected ticks. In contrast, calves infected with carrier blood experienced mild, subclinical reactions despite detectable parasitaemia. The greater severity of tick-induced reactions appeared to be due to the large number of infective doses injected by each infected tick rather than greater virulence of tick versus blood-origin babesiae. The severity of tick-induced babesiosis was related to the age of the experimental calves, with more severe reactions and high mortality occurring among older animals. The mean daily temperature rise increased with age and was highest in 15 animals dying of babesiosis. No relationship could be found between peripheral blood parasitaemia, packed cell volume reduction and mortality in tick-induced infections. One thousand larvae from infected colonies induced babesiosis in all of 29 animals exposed. Although larval transmission of B bovis is difficult to quantitate, there would seem to be no objection to using a controlled tick-borne challenge in the laboratory for assessment of susceptibility.
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Methods of immunoprophylaxis against bovine anaplasmosis with emphasis on use of the attenuated Anaplasma marginale vaccine.
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Comparison of intestinal (Illinois strain) and cell culture-adapted (M-HP strain) viral populations of transmissible gastroenteritis of swine.
Intestinal and cell culture-adapted viral populations of transmissible gastroenteritis (TGE) of swine were compared by means of sucrose gradient centrifugation, immunnofluorescence, electron microscopy, immune electron microscopy, statistical analysis of the number of plaque-forming units, and ultraviolet sensitivity. Results indicated that the size range and general coronavirus morphologic characteristics were shared by both viral populations. Marked morphologic variations existed among particles from both populations. Unlike the cell culture-adapted virus, the Illinois virus of intestinal origin was infractions representing 2 bands of infectivity which were isolated by the sucrose gradient centrifugation method. The intestinal and cell culture-adapted TGE viruses were similar in antigenicity and in sensitivity to ultraviolet irradiation. There was no indication of a 2nd virus in addition to the coronavirus described as the cause of TGE.
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The mechanism of protective immunity in bovine anaplasmosis.
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Anaplasma↗
The brown dog tick Rhipicephalus sanguineus and the dog as experimental hosts of Ehrlichia canis.
Adult Rhipicephalus sanguineus ticks efficiently transmitted Ehrlichia canis to susceptible dogs for 155 days after detachment as engorged nymphs from a dog in the acute phase of ehrlichiosis. Adult ticks that had similarly engorged on a dog in the chronic phase of ehrlichiosis failed to transmit E canis to susceptible dogs. Infected but unfed adult ticks may be of greater importance than the chronically infected carrier dog as a natural reservoir of E canis.
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