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.

The immune responses to antigenic variants of Babesia bigemina in the bovine.

Four Babesia bigemina stabilates were used to determine the immune response of cattle to acute and chronic blood- and tick-borne infections. Thirty-two intact calves were divided into 16 groups of two and each calf was inoculated with infective B bigemina erythrocytic stabilates. Twenty-eight days later they were challanged with homologous and heterologous stabilates, and monitored for an additional 20 days. The hosts' apparently reduced response to homologous challenge but marked immune response to heterologous challenge indicated antigenic differences between the isolates and confirmed the conclusions reached by examination of the serological data.

Propagation of Anaplasma marginale in bovine lymph node cell culture.

Anaplasma marginale was propagated in cell cultures derived from bovine lymph node (LN). Treatment of host cells with diethylaminoethyl dextran (DEAE-D) before inoculation and centrifugation of inoculum onto the monolayers resulted in significant numerical increases of A marginale. The direct fluorescent antibody technique (FAT) was used for detection of the organism in culture. The rat was combined with the standard microscopic count procedure to obtain numerical estimates of the organism in cell culture. Infection of LN cells was irregular, with some cells containing many organisms and others containing none. The organisms were dispersed or in inclusions in the cytoplasm of LN cells. Numerical increases of organisms occurred within 6 hours and these were greatest at 12 to 24 hours. After 24 hours, the organisms decreased rapidly, but small numbers of them were observed for at least 7 days. The average generation time in culture was approximately 17.1 hours.

Comparison of three methods of differentiating bovine mycoplasma.

Growth inhibition (GI) by specific antisera, direct fluorescent antibody technique (FAT), and fatty-acid profile analysis by gas-liquid chromatography (GLC) were compared as methods for identifying 13 strains of bovine mycoplasma. By the FAT, there were 8 bilateral and 13 unilateral cross reactions. In the GI study, there were 4 bilateral and 7 unilateral cross reactions. In both FAT and GI studies, there were fluorescence and inhibition, respectively, with 13 homologous antisera. Analysis by GLC revealed the 13 mycoplasmas could be placed into 4 distinct chromatographic groupings. The GLC profiles of 2 organisms were sufficiently unique that they could be used for specific identification.

Evaluation of the enzyme-linked immunosorbent assay for detecting Brucella abortus antibodies.

The specificity of enzyme-linked immunosorbent assays (ELISA) corresponds to conventional methods for detecting brucella antibodies in bovine serum. The ELISA test detected brucella antibodies early in only 12.5% of the cattle sera tested. Also, the sensitivity of ELISA was comparable to complement-fixation and Rivanol methods, but less sensitive than the standard tube agglutination method.

Mechanical transmission of anaplasmosis by tabanids (Diptera: Tabanidae).

The role of tabanids in the mechanical transmission of anaplasmosis was further clarified by determining the number of horse fly bites needed to transmit the disease and the length of time that horse flies remain mechanically infective. Transmission of anaplasmosis from acutely infected calves to susceptible splenectomized calves was accomplished with as few as 10 horse fly bites. These flies were shown to remain mechanically infective for at least 2 hours after they had obtained a partial blood meal from an acutely infected calf. These data emphasize the efficiency of horse flies in the mechanical transmission of anaplasmosis and indicate that relatively short-distance barriers may not be adequate to prevent transmission between infected and noninfected herds.

Anaplasma marginale in tick cell culture.

Anaplasma marginale was propagated in a tick cell line derived from Dermacentor variabilis embryos. The rickettsial organism was identified and monitored in culture by transmission electron microscopy and the indirect immunofluorescence technique, using specific monoclonal antibodies. Inoculation of the embryonic tick cell line with midguts of infected adult ticks (culture 1), nymphal ticks (culture 2) and adult ticks that were infected as nymphs and dissected as adults (culture 3) resulted in 3 continuous cultures of A marginale. Culture 1 had been maintained through 22 passages over a 11-month period; cultures 2 and 3 had been maintained for 18 passages over a 9-month period. Growth of A marginale in the cell line began in the area of the nuclear membrane at approximately 4 days after inoculation or transfer. Thereafter, the organisms were observed in inclusions scattered throughout the cytoplasm of the host cells. Maximal growth of the organism occurred at 7 to 14 days, after which numbers of inclusions rapidly decreased to minimal or undetectable levels. The organism began new cycles of growth with each 1:5 to 1:10 split and transfer of the host cells. Electron microscopy of recently infected cells revealed a morphology of the organism that closely resembled that observed in marginal bodies of infected erythrocytes. After several passages, A marginale organisms had a varied morphology and resembled the organism described in midgut cells of naturally infected ticks.(ABSTRACT TRUNCATED AT 250 WORDS)

Infectivity and antigenicity of Anaplasma marginale from tick cell culture.

The infectivity and immunogenicity of Anaplasma marginale grown in a tick cell culture from embryonic Dermacentor variabilis ticks were assessed in splenectomized and intact calves, respectively. Culture 1 consisted of the cell line inoculated with midguts of adult ticks infected with the Mississippi isolate of A marginale and dissected 5 to 10 days after repletion and detachment from an experimentally infected calf. Cultures 2 and 3 consisted of the cell line inoculated with midguts of ticks infected with the Virginia isolate of the organism. Inoculum for culture 2 was derived from nymphal ticks dissected 5 to 10 days after repletion and detachment from the infected calf; inoculum for culture 3 was midguts from adult ticks that were fed as nymphs, allowed to molt in the laboratory and dissected 21 to 24 days after molting. In trial 1, cultures 1, 2, and 3 were maintained at pH 6.9 and incubated at 28 C; in trial 2, cultures 1 and 3 were maintained at pH 7.4 and incubated at either 28 C or 37 C. Cultures 1, 2, and 3 failed to induce infection when injected IV and SC into 6 calves in 2 separate trials. Pre-challenge sera from these calves reacted with 2 purified Anaplasma antigens in the ELISA, but failed to react in the complement-fixation test. Results of a trial to use cultures 1 and 3 in combination with an oil-in-water adjuvant to immunize intact calves against A marginale were inconclusive. However, pre-challenge sera from immunized calves reacted with the 2 purified Anaplasma initial body antigens in the ELISA but failed to react in the complement-fixation text.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood magnesium values in healthy cattle and in cattle affected with anaplasmosis and eperythrozoonosis.

Magnesium (Mg) concentrations in plasma, serum, and erythrocytes (RBC) of calves subjected to splenectomy (SP), splenectomy-induced eperythrozoonosis (EP), and experimentally induced anaplasmosis (AN) were determined and compared with pre-SP, pre-EP, and pre-AN values. Mean serum and plasma Mg concentrations varied in parallel through most periods of the trial. Both were highest after SP, but neither value was significantly different from the pre-SP concentrations. Mean serum and plasma Mg values varied inversely with mean RBC values after SP and EP. Mean RBC Mg values increased significantly from previous periods during EP and AN and after AN, with the values after AN being significantly higher than those at all other periods. Mean plasma, serum, and RBC Mg concentrations were correlated to both mean percentage of parasitemia (%P) and packed-cell volume (PCV). The RBC Mg values increased significantly after mean %P reached 20 and the PCV began to decrease. There was evidence for a distinct lag variation in increasing RBC Mg concentrations with respect to both mean %P and PCV during AN. A strong correlation was observed between the RBC Mg values and the %P occurring 5 days previously and the PCV occurring 3 days previously.

Salmonellosis in white-tailed deer fawns.

Experimental infection of white-tailed deer fawns with Salmonella meleagridis was accomplished. The fawns suffered clinical illness, similar to spontaneous cases observed in the field. This disease may be an important factor in fawn survival in wild herds based on the frequency with which Salmonellae could be isolated in wild fawns. The clinical disease was acute, characterized by rapid depression and dehydration. Death ensued in three of eight experimental cases. The survivors suffered clinical illness.

Small mammals and white-tailed deer as possible reservoir hosts of Brucella abortus in Texas.

Four hundred sixty-eight wild mammals were collected from four ranches in Texas where Brucella-infected cattle herds are maintained, and examined as possible reservoir hosts for Brucella abortus. Seventy-one serums from five species were tested for Brucella antibodies. Liver and spleen from 453 mammals (14 species) were cultured for B. abortus. Results of the serologic and bacteriologic examination of rodents, opossums (Didelphis virginiana), raccoons (Procyon lotor) and white-tailed deer (Odocoileus virginianus) did not provide evidence of an extrabovine reservoir of B. abortus.