Anaplasma ovis in Idaho sheep.

Blood samples from 16 anaplasmosis complement-fixation (CF) positive sheep from a flock near Cambridge, Idaho, were inoculated into 3 intact sheep and 3 splenectomized calves. The 3 sheep became CF positive, and 2 developed parasitemia. None of the 3 calves had signs of anaplasmosis, but all became ill when they were subsequently challenge exposed with blood from known carriers of Anaplasma marginale. After a 75-day observation period, blood from the recipient intact sheep was subinoculated into 3 splenectomized sheep. These splenectomized sheep developed clinical anaplasmosis and became CF positive. In only 1 sheep was there a positive rapid card agglutination test. Therefore, the rapid card agglutination test was not considered to be diagnostic for anaplasmosis carrier status in sheep. Electron microscopic studies were performed on infected sheep erythrocytes to determine the morphologic structure of the organism involved. The causative organism was determined to be Anaplasma ovis.

Efficacy of a new oxytetracycline formulation against clinical anaplasmosis.

A study was conducted to determine whether 1 intramuscular injection of an experimental long-acting oxytetracycline formulation was effective in treatment of induced acute anaplasmosis in cattle and to compare this with the drug response resulting from repeated treatments with an existing, approved oxytetracycline product. The new formulation was supplied in solutions of 200 mg of oxytetracycline/ml and was administered 1 time at the rate of 20 mg/kg of body weight. The experimental formulation was compared with a product providing 50 mg of oxytetracycline/ml which was administered on 2 consecutive days at the dose rate of 10 mg/kg for each treatment. The response to treatment observed in the study animals indicates that 1 injection of the experimental formulation was equivalent to 2 daily injections of the 50 mg/ml product in treating animals with acute bovine anaplasmosis compared with infected nonmedicated control animals. The need for new chemotherapeutic compounds such as this formulation for use in the treatment and control of anaplasmosis is discussed.

Evaluation of free-roaming mule deer as carriers of anaplasmosis in an area of Idaho where bovine anaplasmosis is enzootic.

Samples of blood from 87 Rocky Mountain mule deer (Odocoileus hemionus hemionus) were inoculated into 3 susceptible splenectomized calves to determine the anaplasmosis carrier status of the deer. The deer were trapped along the Idaho-Utah state boundary, near Stone, Id. Acute anaplasmosis was induced in 2 of the 3 inoculated calves, and blood from the 3 calves caused anaplasmosis when inoculated into adult non-splenectomized cattle. Serum rapid card agglutination testing revealed 13 (14.9%) positive reactions among the 87 mule deer. When these seropositive samples were evaluated with the complement-fixation test, positive reactions were not found and only 3 (3.5%) serums gave suspect reactions. A serologic survey for anaplasmosis in 1,852 cattle that cohabit spring and summer rangeland areas with mule deer revealed 14.5% reactors by the serum rapid card agglutination test. The study area consisted of an ecosystem that supports cattle, free-roaming mule deer, and Dermacentor andersoni, and thus contained the elements necessary to effect interspecies transmission of Anaplasma marginale. The significance of wildlife reservoirs and their bearing on anaplasmosis control and eradication programs needs further investigation.

Effect of oral inoculation of Escherichia coli on colostral antibody production in cattle.

Oral inoculation of approximately 1.2 x 10(9) viable Escherichia coli to pregnant cows resulted in increased blood serum and colostral whey titers to the "O" antigen. The antibody titers were more pronounced in colostral whey and were correlated with the inoculum strain of Escherichia coli. There was no correlation between antibody titers of the colostrum ingested and the resulting serum antibody titers of the calves. The incidence of diarrhea in calves did not correlate with the antibody titer in the colostrum. The occurrence of diarrhea was significantly greater in calves that did not ingest colostrum until they were 12 hours old, compared with calves that had free access to their dams and suckled within an hour of birth.

Antibacterial host defense: in vitro interaction of bacteria, serum factors, and leukocytes from precolostral dairy calves and their dams.

The bactericidal capacity of serum and peripheral blood leukocytes from newborn dairy calves (before receiving colostrum) and their dams for a strain of Escherichia coli and Staphylococcus aureus has been investigated. Comparative studies were conducted, using either unheated (freshly collected) and heated serums alone or in combination with cells from adult and newborn animals. Neither serum from newborn calves was able to kill either microorganism. Both microorganisms were sensitive to bactericidal activity of antibody and complement in unheated serum from adult cattle. On heating, serum from adult cattle lost bactericidal properties of the antibody-complement system. A cellular deficiency in phagocyte function in cells of newborn dairy calves was not evident, since they were as able to kill E coli and S aureus as cells from adult cattle, when incubated in the presence of the same opsonic source. Bactericidial activity was not evident when cells from newborn calves were incubated with heated autologous calf serum and S aureus or E coli. Unheated, autologous calf serum combined with cells from newborn calves exerted bactericidal capacity against S aureus but not E coli. The bactericidal capacity against S aureus of cells from newborn calves incubated with unheated serum from newborn calves did not differ from heated serum from adult cattle. However, there was a difference with E coli. The reasons for this phenomenon have not been determined, but may relate to natural, specific immunity of the neonate. Immunoglobulin and antibody concentrations in serums from calves and dams were determined. Most of the dams had bacterial agglutination titers to both microorganisms; the calves had either undetectable or low levels of antibody.

Survey of anaplasmosis in elk of the Clearwater National Forest (Idaho).

Samples of blood from 27 free-roaming elk (Cervus canadensis canadensis) from the Clearwater National Forest in north central Idaho were tested by the rapid card agglutination test and complement-fixation test for the presence of antibodies against Anaplasma marginale. The serum card test and complement-fixation test gave incomplete and false-positive reactions; the plasma card test did not give any reactions. Anaplasma bodies or other blood parasites were not observed in stained smears of elk blood. Blood from 11 elk, including 2 that were serum card test-positive, did not produce clinical, hematologic, or serologic evidence of infection in 3 anaplasmosis-susceptible bovine calves.

Isolation of a subgroup two adenovirus from calf with weak calf syndrome.

A viral agent, designated Id-1, was isolated from the buffy coat of a calf suffering from weak calf syndrome. The virus replicated on bovine salivary gland cells and caused cytopathic effect within four days after infection-Cytopathic effect was characterized by rounding and clumping of cells. Stained preparations of infected monolayers revealed multiple intranuclear inclusions. The agent was found to be resistant to chloroform, ether, trypsin, sodium desoxycholate, oxytetracycline and a pH range of three to nine. The virus was sensitive to 5-iodo-2'-deoxyuridine and to a temperature of 70 degrees C. Cross neutralization tests with Id-1 antiserum and bovine adenovirus type 7 (strain Fujuroi) antiserum resulted in complete neutralilation of both viruses with four or less antibody units of homologous or heterologous antiserum.

Effect of five daily intravenous treatments with oxytetracycline hydrochloride on the carrier status of bovine anaplasmosis.

Intravenous administration of oxytetracycline hydrochloride at the rate of 22 mg/kg daily for 5 days was effective in rendering parasite-free 11 adult cattle that were naturally infected Anaplasma marginale carriers. The treatment did not cause any noticeable distress or side effect. Through 12 posttreatment months, the efficacy of the treatment procedure was evaluated by serologic tests and subinoculation of blood into susceptible splenectomized calves. Results of the rapid card agglutination test were positive for 5 cattle at 2 months after treatment, but negative for all cattle at 4 through 12 months. Complement-fixation titers were variable and transient in posttreatment serologic studies. After subinoculation of blood into splenectomized calves (at 4 and 12 months after chemotherapy), serologic, hematologic, or clinical evidence of infection with A marginale was not seen during a 60-day observation period.