Natural bovine lentiviral type 1 infection in Holstein dairy cattle. I. Clinical, serological, and pathological observations

Clinical, serological, and pathological abnormalities observed in Holstein cows naturally infected with bovine lentivirus 1 bovine immunodeficiency virus (BIV) and other infections were progressive and most commonly associated with weight loss, lymphoid system deficiency, and behavioral changes. Clinical evidence of meningoencephalitis was dullness, stupor, and occasional head or nose pressing postures. The polymerase chain reactions associated the BIV provirus with the lesions in the central nervous system and lymphoid tissues. Multiple concurrent infections developed in retrovirally infected cows undergoing normal stresses associated with parturition and lactation. A major functional correlate of the lymphoreticular alterations was the development of multiple secondary infections which failed to resolve after appropriate antibacterial therapy. The chronic disease syndrome in dairy cows associated with BIV may be useful as a model system for investigation of the pathogenesis of the nervous system lesions and lymphoid organ changes that occur in humans with lentiviral infection.

Natural bovine lentivirus type 1 infection in Holstein dairy cattle. II. Lymphoid tissue lesions

Bovine immunodeficiency virus (BIV) in Holstein cows was associated with morphologic evidence of lymphoid organ deficiency. Cows were subjected to normal management practices including parturition and lactation without adverse environmental stresses. During the clinical disease process there was marked weight loss and wasting with frequent and severe concurrent infections. Lymphoid follicular hyperplasia and dysplasia in lymph nodes, and hypertrophy and hyperplasia in hemal lymph nodes were characteristics of the lymphoid tissues. Atrophy of lymphoid cell compartments with depletion of lymphocytes and a lymphocytic lymphoid folliculitis were components of the lymphoid system pathology. The nodal tissue lesions resembled those observed in feline, simian, and human lentiviral disease. A functional correlation with immune system deficiency was the development of multiple bacterial infections which failed to resolve after appropriate therapy. The BIV-associated disease syndrome in dairy cows may be useful as a model system for investigation of the pathogenesis of the lymphoid organ changes that occur in humans and animals with lentiviral infection.

Natural and experimental bovine immunodeficiency virus infection in cattle

Since 1989, the LSU dairy herd, with its high seroprevalence of BIV, was recognized to have a high incidence of common diseases that reduced the economic viability of the dairy. The herd had a high percentage of cows with encephalitis associated with depression and stupor, alteration of the immune system associated with secondary bacterial infections, and chronic inflammatory lesions of the feet and legs. The occurrence of disease problems was associated with the stresses of parturition and early lactation and/or with unusual environmental stress cofactors.

Encephalitis, lymphoid tissue depletion and secondary diseases associated with bovine immunodeficiency virus in a dairy herd

Encephalitis, lymphoid tissue depletion and secondary infections occurred over a 5-yr-period in Holstein cows infected with bovine immunodeficiency virus (BIV). There were 59 cattle studied, the majority during 1991, when a severe environmental stress occurred, each with one or more primary causes of death, natural or by euthanasia, and most with several secondary diseases. The encephalitis was characterized by meningeal, perivascular and parenchymal infiltration with lymphocytes, occasional plasma cells and macrophages with perivascular edema in some cows. Affected areas included the cerebrum, cerebellum, and spinal cord with no particular distribution pattern recognized. The lymphoid depletion was primarily an absence of follicular development in nodes draining regions with secondary infections such as chronic mastitis and chronic suppurative pododermatitis. Paucity of lymphocytes in thymic-dependent regions of lymph nodes and the spleen suggested a primary depletion of T cells. Secondary infections were often multiple with each cow having several minor conditions, usually considered short-term and treatable. These included mastitis and pododermatitis, with many cows having non-responding abscesses, cellulitis and myositis attributed to injection site infections. A large number of the cattle had parturition difficulties such as dystocia, obturator paralysis, and metritis. Pulmonary, cardiovascular, and intestinal disease were recognized as both primary and secondary disease conditions. There was a high level of infection with bovine leukemia virus with 4 of the 59 cattle having lymphosarcoma. Under practical conditions, the infection with BIV has a different effect on the host than has been observed under experimental conditions. The presence of BIV combined with the stresses associated with parturition and a modern dairy production system were considered causal for the development of untreatable secondary diseases in immunocompromised cattle. The peak incidence in 1991 was attributed to increased environmental stress during renovation of the barn facility. During this time the cattle were kept on open pasture, exposed to an extremely wet winter, and spring weather conditions. The effect of co-infection with bovine leukemia virus, the influence of immunocompromise on the chronicity of mastitis, the relationship with laminitis and pododermatitis, and several questions related to viral transmission, complementarism with bovine leukemia virus, viral reactivation and immunoprophylaxis all remain as viable avenues for future investigations.

Relative susceptibility of beef and dairy calves to infection by bovine leukemia virus via tabanid (Diptera: Tabanidae) feeding

Differences in susceptibility of beef (mixed breeds) and dairy (Holstein) calves to infection by bovine leukemia virus (BLV) were compared. Transmission was accomplished by interrupted feeding of horse flies, Tabanus fuscicostatus Hine, on a donor cow exhibiting persistent lymphocytosis. Flies were transferred individually from the donor cow to each of 11 beef and 10 dairy calves. Transmission of BLV was accomplished with groups of 50 and 250 flies for beef calves and 75 and 250 for dairy calves. These findings indicate that susceptibility of beef and dairy calves to transmission of BLV by tabanids is equivalent and that BLV prevalence differences previously observed among cattle breeds may be caused by management practices.

Single-step technique for staining Anaplasma marginale in bovine blood smears

Three available differential stains, Camco-Quik, Diff-Quik, and Wright-Giesma were compared for detection of intraerythrocytic Anaplasma marginale in bovine blood smears. In samples where < 1% to more than 51% of the RBC were infected, statistical analysis of the data indicated no significant difference in the detection of A marginale with Camco-Quik or Diff-Quik stains. However, a significantly lower percentage of infected RBC were detected when blood smears were stained with the Wright-Giemsa stain, compared with the other 2 methods.

Antimicrobial susceptibilities of staphylococcal species isolated from mammary glands of unbred and primigravid dairy heifers

Staphylococcal isolates from teat canal keratin and mammary secretion samples of unbred and primigravid Jersey heifers were tested in vitro for susceptibility to 12 antimicrobial agents. More than 92% of the 311 isolates were susceptible to all antimicrobial agents tested. Staphylococci other than Staphylococcus aureus demonstrated an overall susceptibility of 98.3% to all antibiotics, and Staphylococcus aureus demonstrated a 97% susceptibility. Across all staphylococcal species, susceptibility of isolates from secretion samples was 98.1%, and susceptibility of isolates from teat canal keratin samples was 93.1%. Differences in susceptibilities were observed among herds.

Efficacy of febantel against abomasal nematodes and lungworms in cattle

The efficacy of febantel at a dosage of 5 mg/kg (45.5% paste formulation) against inhibited early 4th-stage larvae (EL4) of Ostertagia ostertagi, other nematodes of the abomasum, and Dictyocaulus viviparus was investigated in 4- to 6-month-old Holstein calves that grazed on pasture heavily contaminated with parasites from February 24 to April 1, 1986 (36 days). In Louisiana, this is the first month of a 3-month period in which increasing numbers of inhibition-prone O ostertagi larvae are acquired, and infection risk with D viviparus may remain high. Three of 4 calves that died of lungworm infection during the pasture-exposure period were necropsied. Large numbers of abomasal nematodes, including inhibited O ostertagi larvae, and large numbers of D viviparus were recovered. Twenty-five calves were randomly allotted by equal distribution of body weight to 2 groups and treated on April 4: placebo-treated calves (n = 13) and febantel-treated calves (n = 12). Equal numbers of treated and control calves were killed at 6 and 7 days, respectively, after treatment. Mean numbers of O ostertagi in control cattle were: adults, 4,931; developing 4th-stage larvae (DL4), 1,119; and inhibited EL4, 3,410. Ostertagia lyrata, Trichostrongylus axei, Haemonchus sp, and D viviparus were well distributed in nearly all control calves. Percentage reduction of O ostertagi in treated calves, when compared with controls, was: adults, 83.6%; DL4, 57.8%; and inhibited EL4, 34.8%. Percentage reductions of other species were: O lyrata, 92.6%; T axei adults, 99.3% and 4th-stage larvae (L4), 100%; Haemonchus sp adults, 66.7%, and L4, 64%; D viviparus adults 90.6%, and immature forms, 97.1%.(ABSTRACT TRUNCATED AT 250 WORDS)

Screening for neonatal isohemolytic anemia in calves

Anti-erythrocytic immunoglobulins in serum and colostrum of 124 anaplasmosis-vaccinated cows were detected with a saline agglutination test. Positive results were correlated with the occurrence of neonatal isohemolytic anemia (NIA) in calves and were used to predict the occurrence of NIA. The disease was prevented by withholding colostrum from calves with a high potential for NIA.

Comparative evaluation of a commercial microdilution method and a conventional disk diffusion method for determination of antibiograms of gram-positive cocci

A commercial broth microdilution system for testing the antimicrobial susceptibility of gram-positive cocci was compared with the standardized disk agar-diffusion method by testing 254 clinical strains of staphylococci and streptococci using both methods. A total of 2,794 parallel determinations were made with 92.3% complete agreement between the 2 methods; of the discrepancies encountered, 3.0% were minor, 2.5% were major, and 2.1% were very major. The results indicate that the commercial microdilution system may provide a reliable quantitative method for antimicrobial susceptibility testing of clinical isolates from animals.

Antimicrobial susceptibility of coagulase-positive staphylococci isolated from Louisiana dogs

Disk diffusion susceptibility tests were done on 1,178 clinical strains of coagulase-positive staphylococci (CPS) isolated from dogs during a 7-year period. Relative decreases of 7% to 33% were found in the percentages of CPS sensitive to 8 antimicrobics. Relative percentages of CPS sensitive to 9 other antimicrobics were increased or decreased less than 5%. Sensitivity to the beta-lactam antibiotics showed the least relative change. Regression analysis demonstrated that the greatest change in percentage sensitivity of CPS occurred to gentamicin and cephalothin and the least change occurred to penicillin and ampicillin. Recent canine clinical isolates of CPS, specifically identified as Staphylococcus intermedius (n = 109), were uniformly sensitive to novobiocin, amikacin, tobramycin, spectinomycin, and amoxicillin-clavulanic acid. Twenty-two isolates were also sensitive to 17 other antimicrobics. Eighty-seven isolates were resistant to 1 or more antimicrobics tested. Resistance was most common to sulfonamides, penicillin G, ampicillin, tetracycline, and streptomycin. Differences in susceptibility results between S intermedius and unspecified CPS were not statistically significant.

A survey of adverse effects associated with ivermectin use in Louisiana horses

In a survey of 13 Louisiana equine practices, it was determined that 366 of 3,316 horses developed adverse reactions following use of ivermectin, with 3 of the horses having more than 1 reaction. Almost all of the reactions were of minor to moderate concern; however, 1 death was reported. Three hundred and thirty-two (91% of all reactions) were reported as ventral midline pruritus or edema (10% of all doses). Fifteen (0.45%) were transient injection site swelling and/or stiffness. Eleven horses (0.33%) developed limb edema. Eyelid edema was reported in 4 horses (0.12%). Two horses (0.06%) had fever. Rate and depth of respiration was increased in 1 horse (0.03%). One horse (0.03%) became disoriented. Three horses (0.09%) developed signs of colic. One horse (0.03%) died a few minutes after injection, and 1 horse (0.03%) became depressed. The survey covered the period from March to August of 1983.

Fatty acid composition of equine erythrocytes

Fatty acid composition of erythrocytes of healthy horses was determined. Three fatty acids (C16:0, C18:0, and C18:1) were found in approximately equal quantities and comprised 72.17% of the total. Nine other fatty acids were found in small amounts. Saturated fatty acids constituted 67.2% of the total. Marked variation was demonstrated in the occurrence and distribution of fatty acids in the sterol ester, triglyceride, phospholipid, and free fatty acid fractions.

Fatty acid composition of equine plasma

Fatty acid composition of plasma lipids of normal horses was determined. Four fatty acids (C16:0, C18:0, C18:1, and C18:2) comprised 86.73% of the total, with C18:2 comprising 44.04% of the total. Eight other fatty acids were found in small amounts. Unsaturated fatty acids constituted 66% of the total. Marked variation was demonstrated in fatty acid occurrence and distribution in the sterol ester, triglyceride, phospholipid, and free fatty acid fractions.

Comparisons of serotests with calf inoculations for detection of carriers in anaplasmosis- vaccinated cattle

Fifteen months after discontinuing vaccination for anaplasmosis in a herd of 131 cattle, 126 of the animals were reactive to the complement-fixation or card-agglutination tests. Inoculation of splenectomized calves proved that 9 animals were carriers and 117 animals were free of anaplasmosis. Anaplasmosis vaccination induced titers detectable by the standard serotests that persisted for at least 15 months.

Determination of antimicrobial susceptibility of Pseudomonas aeruginosa by disk diffusion and microdilution methods

Disk diffusion susceptibility tests were performed on 180 recent clinical isolates of Pseudomonas aeruginosa. Minimal inhibitory concentration values were determined at the same time by a broth microdilution method. All isolates were sensitive to colistin (< 4 migrogram/ml), but resistant to ampicillin (greater than or equal to 16 microgram/ml), cephalothin (greater than or equal to 64 microgram/ml), and nitrofurantoin (> microgram/ml). More than 90% of the isolates were sensitive to gentamicin (median, less than or equal to 0.25 microgram/ml), tobramycin (median, less than or equal to 0.25 microgram/ml), and amikacin (median, less than or equal to 1.0 microgram/ml) and more than 70% were sensitive to carbenicillin (median, 64 microgram/ml). When the resistant and intermediate categories were combined, over 90% of the isolates were resistant to tetracycline (median 16 microgram/ml), chloramphenicol (median, > 32 microgram/ml), kanamycin (median, 16 microgram/ml), and trimethoprim-sulfonamide combiantion (median, 4 microgram/ml; 76 microgram/ml). Differences between the disk diffusion and microdilution methods in distinguishing resistant isolates of P aeruginosa from sensitive isolates were minor. Complete agreement between the two methods was obtained in 87.0% of the observations.