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The occurrence of clinical mastitis in two large California dairy herds over a 3-yr period is described. Herds had been participating for 15 or 22 yr in mastitis control programs against Streptococcus agalactiae and Staphylococcus aureus, had low bulk tank SCC, and had maintained good standards of hygiene and husbandry, but clinical mastitis remained a serious problem. A total of 1654 clinical mastitis cases were detected; the annual incidence in each herd was 49%. Coliform bacteria and environmental streptococci were etiological agents in 60% of the total clinical mastitis cases; coliforms produced 1.6 times more clinical mastitis than environmental streptococci. A higher susceptibility to clinical mastitis, primarily from coliform bacteria and environmental streptococci, was found in the first months of lactation. Clinical mastitis incidence peaked for cows in lactations 4 and 5 and was lowest during the first lactation. Highest incidence of clinical mastitis due to coliform bacteria and environmental streptococci at each dairy occurred during the rainy season (late fall and winter).

Summary The effect of combined administration of flunixin meglumine (FM) and nordihydroguaiaretic acid (NDGA) on milk prostaglandin F2a (PGF2a) and leukotriene B4 (LTB4) concentrations, and inflammatory indicators of bovine mastitis was examined. Mastitis was induced in six Holstein cows by the inoculation of Klebsiella pneumoniae via the teat canal. Four cows were intravenously treated with FM (1.1 mg/kg) and NDGA (10 mg/kg) 1 hour prior to bacterial inoculation and again at post inoculation hour (PIH) 11. Two control cows were intravenously treated with equivalent volume doses of sterile isotonic saline solution at the same post inoculation time points. Combined use of FM and NDGA was effective in reducing elevations in milk PGF2a levels and slightly effective in reducing elevations in milk LTB4 levels in the mastitic cows. Elevations in milk bovine serum albumin (BSA) levels were partially reduced during the early post inoculation time period in the FM and NDGA treated cows as compared to the saline treated control cows. Milk somatic cell counts from inoculated quarters were not significantly altered by FM and NDGA treatment. Elevations in rectal temperature were not reduced by FM and NDGA treatment, but clinical signs of quarter inflammation (warmth and swelling) were reduced by FM and NDGA treatment.

In studies to assess the possible involvement of an arthropod vector in the transmission of epizootic bovine abortion (EBA), a disease of range cattle in California, the argasid tick Ornithodoros coriaceus Koch was selected for blood-feeding susceptible heifers. Twelve test heifers, each between the 3rd and 5th months of gestation, were exposed to the feeding of from 100 to 626 O. coriaceus captured from EBA-enzootic areas. Of these, 5 aborted 93 to 117 days after tick exposure, and each fetus possessed pathologic lesions judged to be identical to those of EBA fetuses aborted after naturally acquired exposure. It is suggested that the premature calving experienced by 4 test heifers is also associated with exposure to tick feeding and, possibly, to EBA as well. The 5 control heifers calved normally at term. These results are interpreted as evidence that O. coriaceus exposed test heifers to the etiologic agent or substance of EBA. We view these results as the first good evidence that the EBA agent, whatever it may eventually prove to be, is arthropod-borne in nature. The bionomies of O. coriaceus are, as discussed, consistent with the tick's involvement as a vector of EBA in California.

Recognition of Mycoplasma-induced mastitis is on the increase. Although Mycoplasma bovis is identified as the causative agent in more than 50 per cent of the mastitis cases, seven other Mycoplasma species have also been isolated. The mycoplasmas are commonly found in the microflora of the respiratory and urogenital tracts of normal cattle, where precipitating factors can initiate their role as pathogens. Most udder infections are spread from cow to cow by physical contact and are precipitated through deficiencies in procedures in milking, equipment maintenance, sanitation, and udder infusion. Generally, the reaction in the udder is severe and persistent, and recovered animals remain shedders and potential carriers. Extensive therapy with antibiotics has not proven effective in altering the course of the disease. Control procedures in epizootics of mycoplasmal mastitis are based either on elimination of the infected animals by culling or through the co-existence on the dairy of known carrier animals segregated and milked separately from the uninfected animals. Adequate sanitation, proper udder infusion, and good milking principles are requisites to preventing mycoplasmal infections.

In recent years, milk and milk products have been implicated as a major contributor to dietary iodine. The possible sources of iodine in milk are supplemental iodine in dairy feeds, iodophor-containing sanitizers used at the dairy farm and/or the processing plant, iodophor-containing teat dips used to control the spread of mastitis among dairy cows, and iodine-containing medications used by veterinarians. A five-year program to determine the California raw milk iodine concentration and identify the sources of adventitious iodine has resulted in the California dairy industry deciding late in 1980 to reduce iodine supplementation of dairy feeds. This resulted in a decrease in milk iodine concentration in samples received in 1981 to 256 ± 234 μg/kg compared to 1980, when the concentration was 474 ± 304 μg/kg. The industry has set up a program to monitor the raw milk iodine concentration at the producer level, thus ensuring that the concentration will continue to decline.

The development of the fetal lesions of epizootic bovine abortion (EBA) was studied in a series of experiments and field cases of the disease. Thirty-six experimentally infected fetuses were recovered at periods of 29 to 126 days after their dams had been infected by allowing the vector tick Ornithodorus coriaceus to feed on them. The sequential development of the fetal lesions was studied and the lesions compared with those in both naturally occurring and experimentally induced infections of the dams which either aborted or carried to term. The early changes observed in the fetuses consisted of transformation and proliferation of lymphocytes and mononuclear phagocytes. These changes were marked by 50 days after tick exposure of the dams, but fetal lesions specific enough to permit making the diagnosis of the disease did not develop until 100 days after dams were exposed by tick feeding. In the fetuses which were either aborted or carried to term after prolonged infection, acute necrotizing lesions were superimposed on the chronic proliferative fetuses. Acute necrotizing foci developed in several organs, but most commonly in lymph nodes and spleen. These foci frequently formed pyogranulomas. Acute vasculitis developed at the same time as the acute focal-necrotizing lesions. These lesions were similar to immune-mediated lesions that result from the deposition of toxic complexes in the tissues. Immunofluorescent examination demonstrated that immunoglobulins (Ig)G and IgM were present in the vascular lesions.

Escherichia coli, Enterobacter aerogenes, and Klebsiella pneumoniae were responsible for 63, 10, and 11 percent, respectively, of 158 coliform organisms recovered from mastitis cases in 8 California herds. The severity and nature of the coliform mastitis problem were found to vary greatly among herds but were characteristic for each of 4 herds studied in detail.

A spirochete-like organism was found in the plasma of bovine fetuses affected with epizootic bovine abortion (EBA). The spirochete-like organism was frequently found in abattoir-collected fetuses as an inapparent infection, and EBA was found in cattle on foothill rangeland where the vector tick Ornithodorus coriaceus could repeatedly reintroduce the infectious agent into pregnant cattle (superinfection). Epizootic bovine abortion resembled a naturally acquired superinfection in circumstances where the agent was frequently present in the environment under conditions favoring transmission. Therefore, to determine whether fetal lesions could be experimentally induced in utero, spirochete-like organisms collected from clinically normal fetuses at an abattoir were inoculated IV and subcutaneously into 2 pregnant heifers 5 times over a 4-month period to mimic repeated tick transmission in the field. Macroscopic and microscopic examinations of tissues from 2 cesarean-collected fetuses and from 3 calves born at term with the naturally acquired spirochete infection indicated that the calves had evidence of an infection that caused morphologic changes compatible with immunologic stimulation and mild reticuloendothelial hyperplasia. Compared with findings in the calves, lesions in the superinfected fetuses were more severe, and the lesion distribution in various organs was more extensive. The spirochete-like organism appeared to be a mild pathogen because of its persistence in the host. Clinical disease from the infection may only develop with repeated superinfections. Therefore, a relationship between this microorganism and EBA is probable.

The California mastitis test (CMT) and bacteriologic culture were performed on samples of bulk-tank milk and cow-composite milk (n = 23,138 cows) from 50 California dairies, 19 of the 50 with known mastitis problems. Thirty-eight (76.0%) bulk-tank milk samples and 12,334 (53.3%) cows were positive by results of the CMT. Potential mastitis agents were isolated from 5,085 (22%) cows. Staphylococcus aureus was isolated from all 50 herds, Streptococcus agalactiae was isolated from 47 herds, and Mycoplasma sp was isolated from 24 herds. For cow-composite milk samples, the prevalences were 9.3% for Str agalactiae, 9.1% for S aureus, 0.9% for Mycoplasma sp, 1.2% for coliform bacteria, 0.9% for other streptococci, 0.8% for coagulase-negative staphylococci, and 1.3% for other organisms. The relative sensitivity and the relative specificity of the CMT performed on cow-composite milk samples were 83.4% and 55.2%, respectively, and the predictive value of positive CMT results was 34.2%.

Congenital spirochetosis was encountered as a newly recognized infection of cattle. The spirochete was seen in blood of fetuses with lesions of epizootic bovine abortion. A spirochete with morphologic features similar to those found in the fetuses was detected in Ornithodoros coriaceus ticks. Ticks collected from rangelands were allowed to feed on cows that then produced epizootic bovine abortion-affected fetuses, and the fetuses had spirochetosis. Inapparent spirochetosis also was found in fetuses in clinically normal cattle sent to slaughter. Only a few lesions were seen in abattoir-collected fetuses. Fetal spirochetosis was common in the bovine population studied, and it appeared that infection may be limited only by the availability of the tick vector.

Samples of bulk tank milk and cow-composite milk from 23,138 dairy cows from 50 California dairies were examined by use of microbiologic procedures. The number of colonies of mastitis pathogens isolated per milliliter of bulk tank milk (used as a predictor of the percentage of infected cows in the herd) was evaluated, using simple regression analysis and Spearman's rank correlation. Correlations between the pathogens and the percentage of cows in each herd shedding the pathogens were found for Streptococcus agalactiae (r = 0.71) and mycoplasma (r = 0.59), but were considerably lower for other pathogens. When greater than or equal to 4,000 colonies of Streptococcus agalactiae were found per milliliter of bulk tank milk, at least 7% of the cows in the herd was shedding this organism. However, a pattern was not found between the number of mycoplasma colonies per milliliter of bulk tank milk and the percentage of infected cows in the herd.

Serum IgG1 ELISA titers recognizing gram-negative core antigens (Escherichia coli [J5]) were studied at a large dairy in central California. Population mean log10 titer was 2.7357 (equivalent to 1:544) with a SE of 0.03843. Titers increased with increased lactation number (unstandardized regression coefficient = 0.06733). Changes in lactation number accounted for only 6.77% of titer variation. Titers less than 1:240 were associated with 5.33 times the risk of clinical coliform mastitis. Also, older cattle were at greater risk to develop clinical coliform mastitis. These factors apparently affect incidence in a nonlinear fashion, with greatly increased risk associated with titers less than 1:240 and with fourth or greater lactations.

Ornithodoros coriaceus Koch ticks were fed on 37 pregnant cows. The fetuses were obtained from the cows at 23 to 126 days after maternal tick exposure. Characteristic lesions of epizootic bovine abortion were observed only in those fetuses recovered 100 days more or after maternal tick exposure. Fetuses collected between 50 and 100 days showed mild-to-moderate lymphoid and mononuclear cell hyperplasia. Reaction in fetuses studied less than 50 days after maternal tick exposure were mild. Lesions could not be seen in 2 of the youngest fetuses. Increases in serum immunoglobulin concentrations were present only in those fetuses examined 80 days or more after their dams had been exposed to ticks. The specificity of the immunoglobulins could not be determined. Sera from 12 fetuses tested failed to fix complement in tests for group-specific chlamydial antibodies. A wide variety of microbiological cultivation attempts were made to recover the causative agent of epizootic bovine abortion from these fetuses; however, no agent was recovered regularly, and chlamydial organisms were not recovered from any. The significance of 2 recovered agents, apparently viral, is still to be determined. Fetal tissues, both frozen and fresh, collected from fetuses of dams exposed to a feeding of ticks were capable of reproducing the disease after inoculation into pregnant cows or directly into fetuses.

During the period extending from Dec 1, 1975, to Dec 22, 1976, 3 distinct peaks in the concentration of infective nematode larvae on pasture forage were detected by use of helminth-free tracer calves. Two of these peaks, 1 occurring in the spring and 1 in the fall, consisted mainly of Ostertagia ostertagi and Cooperia sp. It is concluded that these 2 peaks can be anticipated annually and constitute unsafe periods of grazing. The 3rd peak was comprised largely of Haemonchus placei and Cooperia sp. It is concluded that this peak occurred as the result of unusual rainfall and reduced evaporation in August. Arrested developed (24% to 30%) of O ostertagi larvae occurred only during the spring peak. This finding indicates that on irrigated pastures in California, type I ostertagiasis can be expected to occur as the result of infection during the spring and/or fall peaks, whereas type II ostertagiasis can be expected to occur in the fall as a result of infection obtained during the spring peak. Arrestment in development of Cooperia sp occurred during spring (14%) and fall (23%) peaks. Haemonchus placei larvae increased their propensity for arrestment in development from zero to 82% during the months following the peak level of infection in summer. Other nematodes encountered were Trichostrongylus axei and Nematodirus helvetianus.

Mastitis was induced by infusion of 3,000-7,000 colony-forming units of Klebsiella pneumoniae into the left rear quarter of four primiparous Holstein-Freisians. Greater than 100 organisms were recovered from a quarter milk sample within 2 hr and in 87.5% of the hourly cultures taken after 8 hr. Bacteria, California Mastitis Tests, somatic cell counts and N-acetyl-beta-D-glucosaminidase levels differed significantly from that of control quarters in infused cows after hr 6, 8, 9 and 9 respectively. High correlations were obtained between somatic cell count and N-acetyl-beta-D-glucosaminidase (r = .97) and N-acetyl-beta-D-glucosaminidase and natural log bacterial count (r. = .88). N-acetyl-beta-D-glucosaminidase was related to natural log bacterial counts of samples taken 1, 2, 3, and 4 hr prior to the test (rN-acetyl-beta-D-glucosaminidase and natural log bacterial count (r = .91, .92, .93, and .95).

Culicoides gnats were monitored from April through November, 1981, on the Tejon Ranch, Kern County. Levels of gnat breeding were determined by quantitative sampling of substrate from intermittent and permanent water sources. Adult populations were measured by light trap collections taken around pens holding sentinel beef cattle, dairy calves, sheep, goats and deer. Adult gnats were collected in the environs of the study area, and blood samples were obtained from sentinel animals for laboratory diagnosis and isolation of bluetongue virus (BTV). C. variipennis was 1st observed in various water sources in April, with a continuous increase in density through October. Adult populations reflected this trend in density through October. Both immature and adult gnat populations rapidly decreased in November. BTV serotypes 11, 17 and 13 were isolated from C. variipennis from August through October. BTV serotypes 11 and 17 were initially isolated from nearly all sentinel sheep, goats and dairy calves from late July through September, whereas isolates of 11 and 17 were made from only 2 beef cows and 2 deer in August and September. Sheep were the only sentinel animals that showed clinical signs of BT disease.

By inoculating Klebsiella pneumoniae into the teat canals of mammary glands, coliform mastitis was induced experimentally in 6 lactating cows. Release of eicosanoids, histamine, and serotonin in plasma and milk was studied in response to 2 doses of K pneumoniae. A low dose (mean, 5,000 organisms/ml) was inoculated into cows 1 through 4, and a high dose (mean, 200,000 organisms/ml) was inoculated into cows 5 and 6. Milk and blood samples were collected before inoculation (0 hours), and hourly, from 3 to 24 hours after inoculation. Concentrations of prostaglandin F2 alpha (PGF2 alpha), prostaglandin E (PGE), thromboxane B2 (TxB2), histamine, and serotonin were measured in plasma and milk obtained from control (NaCl solution-inoculated) and infected quarters. Fluorometric analysis of milk from infected quarters revealed significantly increased histamine and serotonin concentrations regardless of the dose of K pneumoniae. The mean (+/- SEM) peak concentrations of histamine were significantly (P less than 0.01) increased from the preinoculation value of 44 (+/- 12) ng/ml to 312 (+/- 104) ng/ml in milk from infected quarters and 72 (+/- 24) ng/ml in milk from control quarters. The mean peak concentration of serotonin increased significantly from the preinoculation concentration of 436 (+/- 37) ng/ml to 1,754 (+/- 662) ng/ml and 4,867 (+/- 1,248) ng/ml in milk from control (P less than 0.02) and infected (P less than 0.001) quarters, respectively. However, serotonin concentration in milk from infected quarters was approximately 2.8 times greater than that in milk from control quarters. Concentrations of PGF2 alpha, PGE, and TxB2 in milk and plasma were evaluated by radioimmunoassay.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum immunoglobulins of the IgG isotype recognizing common gram-negative cell core epitopes were serially measured, using a direct ELISA, on samples obtained from 20 neonatal Holstein calves. An R-mutant Escherichia coli (strain J5) was used as a plate antigen in this assay. Total serum IgG concentration was measured using radial immunodiffusion. Half-lives of core antigen-specific IgG (7.56 days) and total serum IgG (22.66 days) were dramatically different (P less than 0.0005). This may be an indication of cross-reactive consumption of core antigen-specific immunoglobulins.

A total of 116 cows from 4 dairy herds in California were used to determine the sensitivity and specificity of extracellular antigen of Nocardia astero des for possible detection of bovine mastitis caused by N asteroides and N caviae. Three different positive criteria were used. These criteria gave different sensitivity and specificity to the skin test. The highest sensitivity of 80% and highest specificity of 96.04% were obtained by combining 2 criteria. The study found no cross-reaction between N asteroides antigen and Mycobacterium fortuitum or N asteroides and tuberculin skin tests. There was cross-reaction between N asteroides antigen and N caviae infection.