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PubMed1986

Isolate of Anaplasma marginale not transmitted by ticks.

The tick-borne transmissibility of 2 isolates of Anaplasma marginale was compared. Dermacentor variabilis were exposed to A marginale as nymphs by feeding on 1 of 4 splenectomized calves during periods of ascending parasitemia (maximum 49% to 81% parasitized erythrocytes) induced by injection of a stabilate. Tick-borne transmission was attempted, using 26 to 224 adult ticks within 30 to 220 days after molting. Adult D variabilis did not transmit an Illinois isolate of A marginale in 7 tick-borne transmission experiments (P = 0.0047), including 2 experiments in which calves were inoculated IV with homogenates of adult ticks. In contrast, a Virginia isolate of A marginale was readily transmitted by the same tick colony. Thus, previously reported morphologic and immunologic differences among A marginale isolates may extend to tick-borne transmissibility. The Virginia and Illinois A marginale isolates had an inclusion appendage that was not a marker for tick transmissibility.

Anaplasmosis↗
PubMed1985

Transmission of Anaplasma marginale by adult Dermacentor andersoni during feeding on calves.

Laboratory-reared Dermacentor andersoni ticks experimentally infected as nymphs with Anaplasma marginale were allowed to feed as adults from 1 to 9 days on susceptible, splenectomized calves to determine when, during feeding, the hematozoan was transmitted from ticks to cattle. In experiment 1, ticks were allowed to feed on calves for 1, 2, 3, 4, 5, or 6 days and anaplasmosis did not result. The same calves were used for experiment 2, and ticks were allowed to feed for 1, 3, 6, 7, 8, or 9 days and anaplasmosis occurred in all calves on which ticks fed for greater than or equal to 6 days. In 2 trials in experiment 3, ticks were allowed to feed on calves for 1 to 9 days. Anaplasmosis developed only in calves on which ticks fed for 7, 8, or 9 days. The prepatent periods shortened with longer tick feeding, and linear regression analysis of combined prepatent periods of both trials of experiment 3 indicated a significant (P = 0.05) slope with an estimated daily decrease of 7.75 days from day 7 to 9 of feeding. There was no apparent correlation between length of tick feeding and severity of clinical signs in those calves that developed anaplasmosis. Seemingly, A marginale can be transmitted to cattle by adult D andersoni ticks no earlier than the 6th or 7th day of feeding.

Anaplasmosis↗
PubMed1979

The use of a short and a long acting oxytetracycline for the treatment of Anaplasma marginale in splenectomized calves.

Twenty splenectomized Afrikander/Simmentaler cross animals were used. Eight of these were naturally infected with Anaplasma marginale while 12 were infected artificially. When the packed cell volume was reduced to between 24% and 20% during the post splenectomy relapses or primary infections, six animals were treated with a single injection of 20 mg/kg of long acting oxytetracycline (LA) and seven animals were treated on two successive days with 10 mg/kg of short acting oxytetracycline (SA). The remaining seven animals served as untreated controls. Both drugs were effective in controlling A. marginale reactions. No deaths occurred in the group of animals treated with oxytetracycline LA and they showed a longer relapse interval and higher blood levels of oxytetracycline compared to those treated with oxytetracycline SA. A single death occurred in the latter group. Four deaths occurred in the control group which also had the shortest relapse interval.

Anaplasmosis↗
PubMed1977

Resistance to anaplasmosis after elimination of latent Anaplasma marginale infections.

Ten 30-month-old cattle (group 2) were inoculated with Anaplasma marginale 6 months after the latent A marginale infection was eliminated by oral chlortetracycline therapy. In addition, 4 cattle (group 1) with no record of infection and 4 cattle (group 3) of equivalent age previously vaccinated with a killed antigen were similarly inoculated. Moderate to severe clinical signs of acute anaplasmosis occurred in the group 1 (previously uninfected) cattle, whereas only 1 of the chlortetracycline-treated cattle (group 2) and none of the vaccinated cattle (group 3) had clinical evidence of disease.

Anaplasmosis↗
PubMed1978

Serologic and hematologic response of rabbits to Anaplasma marginale-infected bovine erythrocytes.

New Zeland White rabbits inoculated with Anaplasma marginale-infected bovine erythrocytes produced specific humoral antibodies to this parasite. Specific antibody production as measured by the card and complement-fixation (CF) tests was maximal in 7 to 21 days after inoculation; however, none of the rabbits became infected. Geometric mean CF titers of rabbits inoculated with RBC from cattle with acute anaplasmosis were significantly higher (P less than 0.001) than those of rabbits given RBC from normal cattle. Significant difference was not seen between geometric mean CF titers of rabbits given RBC from carrier cattle and those of rabbits given RBC from normal cattle. It is concluded, therefore, that rabbit inoculations cannot effectively be substituted for calf inoculations to determine the anaplasmosis status of carrier cattle.

Agglutination Tests↗
PubMed1978

Bovine abortion associated with Anaplasma marginale.

During the period from June 1974 to June 1975, five bovine fetuses between seven to nine months old were received for necropsy from four different counties of the S. Paulo State, Brazil. All of them were from brucellosis-free herds. Necropsy revealed slight liver enlargement generally accompanied by capsular petechial hemorrhages. Enlargement and congestion of the spleen, epicardial and endocardial petechiae were present in three fetuses and one of them had lungs with some hemorrhagic lobules. Cardiac blood films of all the fetuses stained by the Pappenheim's panoptic method showed Anaplasma marginale in two to 20% of red corpuscles. When stained with acridine orange and immunofluorescent methods blood films of the first fetus specifically showed A. marginale.

Abortion, Spontaneous↗
PubMed1984

Immune responses of calves antigenically stimulated and challenge exposed with Anaplasma marginale during tick infestation or treatment with dexamethasone.

Similar anamnestic antibody responses to a 2nd injection of a Anaplasma marginale vaccinal antigen were observed in calves infested with the tick Dermacentor albipictus and in tick-free calves. When challenge exposure of these calves to virulent A marginale was done, infestation with the tick Boophilus microplus increased anemia (P less than 0.01), but did not suppress antibody production to A marginale or increase parasitemia. None of the vaccinated calves, regardless of infestation, experienced clinical anaplasmosis. Mitogenic responses of lymphocytes from infested animals were unaltered by either infestation. Tick infestations did not cause immune suppression in the calves, whereas use of dexamethasone resulted in a significantly lower antibody response (P less than 0.05) after a 2nd injection of vaccinal antigen. After challenge with virulent A marginale, dexamethasone-treated calves showed more pronounced parasitemia (P less than 0.01) and anemia (P less than 0.01) than did control calves. Anaplasmosis did not prevent the calves from developing resistance to reinfestation, which was accompanied by immediate, but not delayed, hypersensitivity reactions against homologous tick extracts. Dermacentor albipictus did not seem to share common antigenic determinants with B microplus, since extracts from the latter did not elicit immediate hypersensitivity responses in calves sensitive to D albipictus extracts. Calves were somewhat resistant to reinfestation as evidenced by reduced numbers of adult fed ticks, decreased weights of ticks after feeding, and smaller egg masses.

Anaplasmosis↗
PubMed1982

Serologic evidence of Anaplasma marginale infection in Illinois white-tailed deer.

A total of 175 deer and 54 cattle from Crab Orchard National Wildlife Refuge in southern Illinois were tested for antibody to Anaplasma marginale, using the capillary tube agglutination test. A total of 12 (6.9%) deer and 7 (13%) cattle were serologically positive. Serologic prevalence in deer increased from 0 at 6 months of age to 14% at 2 1/2 or more years of age. Cattle less than approximately 1 year of age were not seropositive.

Anaplasmosis↗
PubMed1982

The effect of incubation and prefeeding of infected Rhipicephalus simus nymphae and adults on the transmission of Anaplasma marginale.

Two batches of unfed Rhipicephalus simus nymphae carrying Anaplasma marginale were incubated for 72 h and 96 h respectively at 37 degrees C. Fifty ticks were triturated at a time and the homogenates were used to infect susceptible cattle. Others were prefed on a bovine host for 72 h before tick suspensions were prepared. The same procedure was followed, using a single batch of infected adult ticks. Incubation had no effect on the infectivity of the nymphal homogenates, but prefeeding of nymphae reduced the prepatent period by 8 days in 1 of the 2 attempts. In the case of the adult ticks both incubation and prefeeding reduced prepatent periods by 5 and 8 days respectively.

Anaplasmosis↗
PubMed1981

Transmission of Anaplasma marginale Theiler by Dermacentor andersoni Stiles and Dermacentor variabilis (Say).

Cattle were inoculated with a Virginia isolate of Anaplasma marginale Theiler and served as an infective source for laboratory-reared Dermacentor andersoni Stiles and D variabilis (Say) nymphs. Following a molt and subsequent feeding of adult ticks on susceptible cows, transstadial transmission of A marginale occurred from cattle with parasitemias ranging from undetectable (in a carrier cow) to a peak of 27% (in an acutely ill cow). Homogenates of gut tissue from unfed, incubated, and feeding adult ticks that were infected as nymphs were all infective; however, the prepatent period varied according to treatment of ticks after they had molted to the adult stage. Prepatent periods of infections in calves resulting from injection of homogenated tissue from unfed adult ticks was 29 and 34 days longer than the prepatent periods that developed in calves exposed to homogenated tissue from ticks that were feeding or incubated at 37 C for 3 days. Transovarial transmission did not occur when F1 larvae, hatched from eggs produced by female ticks known to be infective, fed on susceptible cattle.

Anaplasmosis↗
PubMed1981

Clinical chemistry of anaplasmosis: comparative serum protein changes elicited by attenuated and virulent Anaplasma marginale isolates.

In a comparative study of the clinical chemical changes during Anaplasma marginale infection, 16 intact mature cows were infected with either of 2 virulent isolates. Eight others were treated with a live A marginale vaccine (sheep-attenuated) and 7 were maintained as controls. Before and during patency, samples of blood from the cows were analyzed for total WBC, parasitemia, card test titer (CTT), total protein, albumin, and globulin fractions. In the cows inoculated with virulent isolates, albumin was significantly depressed throughout patency, whereas gamma-globulins and WBC were increased after peak parasitemia, as well as during recovery. The CTT was highest immediately after peak parasitemia. A significant increase was not observed in beta-globulin. Seven of the 16 infected cows died, but no consistent patterns of change in serum protein fractions or WBC could be associated with mortality. The 8 cows vaccinated with the attenuated isolate showed a significant mean decrease in albumin throughout patency, but no significant mean increase in alpha- or beta-globulin. A mean increase in gamma-globulin was observed only during the recovery period. The CTT increased gradually throughout patency, peaking during the recovery period. A significant mean increase over control in WBC count was observed only during rising parasitemia.

Anaplasmosis↗
PubMed1978

Serum levels of conglutinin, complement, and immunoconglutinin in cattle infected with Anaplasma marginale.

Sera from 10 splenectomized yearling cattle given massive doses of Anaplasma marginale (peracute cases) were assayed for conglutinin and complement. Sera from 5 nonsplenectomized yearling cattle given smaller doses (acute cases) were assayed for conglutinin, immunoconglutinin, and complement. In the peracute cases, conglutinating activity disappeared within 6 days after the cattle inoculated. In the acute cases, conglutining began to disappear at 3 weeks after inoculation and had disappeared at peak parasitemia at 4 weeks. Conglutinin returned by 7 weeks after inoculation. In the same acute cases, immunoconglutinain appeared at 6 weeks after inoculation and then slowly disappeared. The complement levels in the peracute and acute cases did not change appreciably.

Agglutination Tests↗
PubMed1981

Attempts to transmit Anaplasma marginale with Hippobosca rufipes and Stomoxys calcitrans.

Three attempts to transmit anaplasmosis with field collections of Hippobosca rufipes were unsuccessful, despite the fact that the flies had been fed initially on splenectomized cattle acutely infected with Anaplasma marginale. However, 1 out of the 3 attempts, made concurrently with the others, to transmit this organism with Stomoxys calcitrans was successful. The prepatent period was 27 days.

Anaplasmosis↗
PubMed1981

Freeze-drying of Anaplasma marginale.

Heparinized whole blood, heavily parasitized with Anaplasma marginale, was collected from 3 splenectomized oxen. Buffered lactose peptone (BLP) was added to equal volumes as a stabilizer and the mixture lyophilized in 2 ml aliquots after rapid freezing. The dried material was reconstituted with 2 ml sterile water and inoculated without delay. The product remained infective for at least 6 months when stored in an ordinary household deep-freeze unit.

Animals↗
PubMed1996

[Clinical and hematological changes in calves infected with Anaplasma marginale].

Clinical and hematological changes of six Anaplasma marginale (isolated Zulia) inoculated calves (experimental group) and four healthy calves (control group) were studied during twenty and eighty days before and after infection, respectively. The behavior of the four calves used as control group was stable and no significant changes in the parameters analyzed was observed. The experimental group developed the three typical phases of illness. During the prepatent phase, which lasted a mean of 21.2 +/- 2.56 days, the animals were asymptomatic and no significant changes in the hematological values occurred, but a remarkable transitory decrease in number of lymphocytes from 6.5 x 10(6) to 3.3 x 10(6) cells/ml. The infection during the acute phase produced a highly severe effect in two animals, a severe effect in three animals and a mild effect in one. The effects observed were the following: 1) a fast decrease in haematocrite, ranging from 6 to 10%; 2) values of parasitaemia varied from 15 to 48%; 3) a greater body temperature than the control animals (40.5 vs. 38.5 degrees C); 4) a elevated heart frequency, from 60 to 110 beats/min; 5) an increase in the concentration of neotrophiles from 10 x 10(6) to 13 x 10(6) cells/ml; 6) The number of monocytes also augmented from 3 x 10(6) to 6 x 10(6) cells/ml; and 7) an important decrease of weight gain. The natural course of infection was interrupted with oxytetracycline when the haematocrite of the animal lowered to values less or equal to 10%. Then, the animals showed a rapid recovery with an undetectable parasitaemia and concomitant return to basal line of the rest of the parameters.

Anaplasmosis↗