Evaluation of a new long-acting oxytetracycline formulation against anaplasmosis in colombian cattle.

A long-acting injectable (Terramycin/LA) forulated to contain 200 mg/ml of oxytetracycline was tested and compared to a commercially available oxytetracycline injectable (Emicina) containing 50 mg/ml in the treatments of experimentally induced Anaplasma marginale infection in Colombian cattle. Group 1, consisting of 10 infected calves, served as non-treated controls. Ten infected calves (Group 2) were treated with two doses of Emicina, each at 10 mg/kg, intramuscularly (IM), and another ten infected calves (Group 3) were treated once IM, with 20 mg/kg of Terramycin/LA. All treatments were given during the acute phase of infection after A. marginale parasitemia was demonstrated and when the packed cell volume (PCV) had decreased to 60-64% of normal value. Two treatments with Emicina and one with Terramycin/LA were both effective in moderating the course of A. marginale infection and in preventing serious clinical signs of disease under laboratory conditions.

Immunization against anaplasmosis and babesiosis. Part III. Evaluation of immunization under field conditions in the Cauca River Valley.

Bovine anaplasmosis and babesiosis constitute serious constraints to efficient cattle production in Colombia. Nine commercial ranches located in the Cauca River Valley were used to evaluate the applicability, safety and economics of the newly developed immunization technology to control these diseases under actual field conditions using the minimum infective doses techniques. A total of 432 calves, 6--8 months old, of different breeds were used in this experiment. Calves born and raised in nonendemic areas of Valle, vaccinated against anaplasmosis and babesiosis and then moved to the endemic zone had developed a high degree of resistance. None of them died or required treatment after field challenge. In comparison, non-vaccinated controls suffered severe clinical anaplasmosis and babesiosis. Eighteen percent dies and 85% required chemotherapy to survive. Calves born and raised in the endemic zones of Valle and vaccinated did not suffer clinical disease nor require treatment after field challenge. However, non-vaccinated controls had 2% mortality and 60% of them required treatment to survive under the same field conditions. The weight gains favored vaccinated animals. The results of this study indicate significant reductions in deaths and production losses of cattle and the economic benefits to the livestock producers in controlling tick-borne diseases by vaccination.

Comparisons of the complement-fixation, indirect fluorescent antibody, and card agglutination tests for the diagnosis of bovine anaplasmosis.

Results of complement-fixation (CF), indirect fluorescent antibody (IFA), and card agglutination (CT) tests were statistically compared, using 380 serum samples obtained from 140 cattle which were disease-free or naturally or experimentally infected with Anaplasma marginale of Colombian origin. The IFA test was significantly the most sensitive for detection of amimals infected with anaplasmosis (97%); the CT test and the CF test were less so (84% and 79%, respectively). However, the most efficient test for identifying noninfected animals was the CF test (100%), and the CT and the IFA tests were less efficient (98% and 90%). A linear regression analysis performed on the average IFA and CF titers of 10 calves artificially infected with A marginale during a 20-week period showed significant regression coefficients for both tests. The regression line for the CF titers decreased below the sensitivity threshold at 14 weeks after calves were inoculated, whereas the regression line for the IFA titers continued above the sensitivity threshold 20 weeks after inoculation. The CT test also detected antibodies until the end of the observation period.

Methods to improve the health of cattle in the tropics: conclusions and economic appraisal.

The results of the immune responses of immunised and chemoprophylactically treated calves to tick-borne (Boophilus microplus) challenge indicate that the system of immunisation was effective in protecting cattle against Anaplasma marginale, Babesia argentina (bovis), and B. bigemina. However, chemoprophylaxis was effective only against Babesia spp. but not against A. marginale. Both methods showed a substantial advantage over no control system when using native cattle breeds in a zone endemic for bovine anaplasmosis and babesiosis. Based on the net economic gain per calf starting the experiment, sizeable differences were noted at 308 days between the calves in the immunised group, chemoprophylaxis group, tick and gastrointestinal parasite control group and the experiment control group.

Methods to improve the health of cattle in the tropics: immunisation and chemoprophylaxis against haemoparasitic infections.

A study of methods to improve the health of native cattle in tropical areas of Colombia showed an advantage using immunisation techniques against haemoparasitic infections in comparison with other control methods. The control of anaplasmosis and babesiosis by immunisation of cattle with fully virulent Anaplasma marginale, Babesia argentina and B. bigemina is feasible in tropical cattle when the postimmunisation reaction is controlled by appropriate drug therapy. Chemoprophylaxis was found less effective in controlling haemoparasitic diseases; however, treated was found less effective in controlling haemoparasitic diseases; however, treated cattle surviving the acute stage of infection showed weight gains not significantly different from those of the immunised calves. Both methods were found to be advantageous with calves born and raised in an endemic area of anaplasmosis and babesiosis. Tick and gastrointestinal parasitic control without haemoparasitic control in calves had an advantage over no control system at all. These methods though were inferior to the immunisation and chemoprophylactic techniques.

Antigenic variation of Babesia bigemina.

The purpose of the study was to determine whether antigenic differences occurred in four stabilates of Babesia bigemina derived from a single purified isolate and propagated as acute and chronic, blood-borne and tick-borne infections in Colombian cattle. Antigens were characterised by means of the complement fixation (CF), gel diffusion (GD), agar gel electrophoresis (AGE) and the indirect haemagglutination tests (IHA). Differences were detected. Acute blood and chronic blood antigens were similar, as were acute tick and chronic tick antigens, when compared by IHA and GD. Similarities were observed between acute blood anc acute tick and between chronic blood and chronic tick when these antigens were compared by AGE and CF.

Comparisons of the complement-fixation and indirect fluorescent antibody reactions in the detection of bovine babesiasis.

Complement-fixation (CF) and indirect fluorescent antibody (IFA) antigens were prepared from Babesia bigemina isolates obtained in Texas. These serologic procedures were evaluated on 130 serum samples sequentially collected from 5 B bigemina-infected mature cattle, beginning on the day of exposure and continuing for 175 day thereafter. Both tests were effective in detecting specific antibodies for the first 84 days of infection, with 57 of 60 (95%) serums tested being positive on the CF test and 57 of 57 (100%) tests being positive to the IFA test. During the interval from 98 to 175 days, 24 of 60 (40%) of the serums tested were positive with the CF test, and 53 of 56 (95%) were positive with the IFA test. During the first 84 days, a similar linear regression occurred in both CF and IFA serum titers, but after 98 days the IFA regression flattened out, whereas the CF titers decreased below the sensitivity threshold in 60% of the serums tested.

Immunization against anaplasmosis and babesiosis: Part I. Evaluation of immunization using minimum infective doses under laboratory conditions.

A method of immunization against anaplasmosis and babesiosis using minimum infective doses was developed under laboratory conditions. Stabilates of Anaplasma marginale stored at -60 degrees C were found infective when diluted 10-fold to 10(-3). Stabilates of Babesia argentina and Babesia bigemina stored under the same conditions were infective when diluted 10-fold to 10(-1). Intact calves inoculated with the above dilutions of stabilates developed moderate parasitemias and recovered from infection without treatment. There was an immune response to vaccination with the formation of specific antibodies to A. marginale, B. bigemina and B. argentina as measured by the complement fixation (CF) test. All calves were found resistant to artificial challenge with lethal doses of the respective parasites.

Comparison of indirect fluorescent antibody (IFA) with complement fixation (CF) tests for diagnosis of Babesia spp infections in Colombian cattle.

A total of 372 serum samples were collected from Colombian cattle before and during the course of natural Babesia spp. infection on the North Coast of Colombia. The serum samples were used to compare indirect fluorescent antibody (IFA) with complement fixation (CF) tests for diagnosis of babesiosis. The IFA technique detected Babesia argentina antibodies an average of 4.0 weeks earlier than the CF test and Babesia bigemina an average of 2.5 weeks earlier. Both IFA and CF were capable of differentiating B. argentina and B. bigemina infections, however in some cases cross reactions were observed. In general IFA titers were at relatively high levels of 1:640 to 1:5120 in comparison with CF titers of trace to 1:80. In cases of mortality due to babesiosis, both IFA and CF serologic techniques were very useful in indicating the cause of death. Although both IFA and CF are laboratory tests, the IFA technique had advantages over the CF in simplicity, economy and speed of performance.