Field evaluation of an exoantigen-containing Babesia vaccine in Venezuela.

Bovine babesiosis is endemic in Venezuela, causing significant losses in highly susceptible imported cattle. Current immunoprophylactic methods include the less desirable use of live parasites. Inactivated vaccines derived from exoantigen-containing supernatant fluids of in vitro Babesia bovis and B. bigemina cultures have been developed and constitute a major improvement in vaccine safety, stability and ease of handling. Vaccination trials conducted under field conditions provide the final evaluation of a culture-derived B. bovis-B. bigemina vaccine. During a 5-year period, approximately 8,000 cattle were vaccinated and 16 clinical trials carried out in 7 states of Venezuela. Clinical, serologic and parasitologic data were collected monthly from 10% of the animals over a 2-year period. Data were also collected from a similar number of nonvaccinated control cattle. Analysis of results from these trials demonstrated a reduction in the incidence of clinical disease among vaccinated animals and complete protection against mortality caused by babesiosis. Vaccine efficacy was measured calculating the incidence rates of disease and mortality among vaccinated and nonvaccinated cattle. Use of this inactivated vaccine offers the best combination of safety, potency and efficacy for the effective immunoprophylactic control of bovine babesiosis.

Field evaluation of an exoantigen-containing Babesia vaccine in Venezuela

Bovine babesiosis is endemic in Venezuela, causing significant losses in highly susceptible imported cattle. Current immunoprphylatic methods include the less desirable use of live parasites. Inactivated vaccines derived from exoantigen-containing supernatant fluids of in vitro Babesia bovis and B. bigemina cultures have been developed and constitute a major improvement in vaccine safety, stability and ease of handling. Vaccination trials conducted under field conditions provide the final evaluation of a culture-derived B. bovis-B. bigemina vaccine. During a 5-year period, approximately 8,000 cattle were vaccinated and 16 clinical trials carried out in. 7 states of Venezuela Clinical, serologic and parasitologic data were collected monthly from 10% of the animals over a 2-year period. Data were also collected from a similar number of nonvaccinated control cattle. Analysis of results from these trials demonstrated a reduction in the incidence of clinical disease among vaccinated animals and complete protection against mortality among vaccinated and nonvaccinated cattle. Use of this inactivated vaccine offers the best combination od safety, potency and efficacy for thew immunoprophylatic control of bovine babesiosis

Efficacy of purified Anaplasma marginale initial bodies as a vaccine against anaplasmosis.

Anaplasma marginale initial bodies of the Florida strain were purified from infected erythrocytes using a combination of ultrasonic disruption, nonionic detergent and differential centrifugation. Immunochemical analysis revealed at least 12 A. marginale proteins in the molecular mass (m) range 81-15 kDa with a prominent band at 38 kDa. Several of these proteins remained insoluble in the presence of nonionic detergent. Preparations of purified Anaplasma initial bodies contained negligible erythrocytic contamination, as confirmed by the minimal induction of isoantibodies against bovine blood group antigens and the absence of delayed-type hypersensitivity to erythrocytic antigens in immunized animals. A total of 33 crossbred and purebred Holstein cattle were vaccinated with either 1.5, 1.0, or 0.1 mg protein of intact initial bodies, or with 1.0 mg of solubilized Anaplasma protein. The immunogens were supplemented with 3.0 mg Quil-A saponin adjuvant and administered in 2 subcutaneous injections given at a 4-week interval. A similar number of nonvaccinated cattle served as controls. Three months after vaccination, all cattle were challenged by inoculation of 10(9) virulent A. marginale of either the homologous (Florida) or heterologous (Venezuelan) strains. Vaccinated cattle showed solid protection after homologous and heterologous challenge, characterized by parasite clearance and minimal hematocrit reductions. Initial data from four field vaccine trials revealed a reduced incidence of clinical anaplasmosis among immunized animals. Use of immunogens consisting of purified A. marginale initial bodies offers a potential immunoprophylactic approach to control of bovine anaplasmosis.

Use of the dot enzyme-linked immunosorbent assay with isolated Anaplasma marginale initial bodies for serodiagnosis of anaplasmosis in cattle.

Isolated Anaplasma marginale initial bodies were successfully used in a dot ELISA for rapid detection of antibodies to Anaplasma organisms. The enzyme immunoassay used only 25 ng of antigen dotted onto nitrocellulose disks. Antigen-antibody complexes were detected by use of alkaline phosphatase-conjugated protein A, and reactions were read visually after addition of a precipitable, chromogenic substrate. The test allowed the processing of multiple sera, either for screening or for titer determination, in less than 3 hours and was found to be as sensitive as the indirect fluorescent antibody test. The overall performance of the dot ELISA, using isolated A marginale initial bodies, for 580 bovine serum samples was as follows: sensitivity, 93%; specificity, 96%; and predictive value, 95%. Cross-reactivity was not observed with sera positive to Babesia bovis and B bigemina, Trypanosoma vivax, or common bacteria or viruses infecting cattle. The antigen dotted onto nitrocellulose disks was stable when stored at -20, 4, or 25 C. Compared with the indirect fluorescent antibody test, the dot ELISA allowed easier, faster, and more objective interpretation of results. Its simplicity and low cost combined with high sensitivity and specificity indicate that this assay could effectively replace serologic assays currently used for diagnosis of anaplasmosis in cattle.