Mycoplasma infections in small ruminants.

Mycoplasmas have complex mechanisms of antigenic variation that allow them to evade the immune system. These organisms cause a variety of clinical syndromes that can have a significant economic effect on small ruminant production. The syndromes range from acute septicemia and death to chronic infection resulting in decreased production. Recent research findings have shed light on the means by which these organisms evade the host immune response and cause or contribute to the development of disease in the host. This article provides a review of the pathogenesis, clinical signs, and treatment options for common disease syndromes involving Mycoplasma spp. in small ruminants.

Transposon mutagenesis of Mycoplasma gallisepticum by conjugation with enterococcus faecalis and determination of insertion site by direct genomic sequencing.

Few genetic systems for studying mycoplasmas exist, but transposon Tn916 has been shown to transpose into the genomes of some species and can be used as an insertional mutagen. In the current study, the ability of Enterococcus faecalis to serve as a donor for the conjugative transfer of transposon Tn916 into the genome of the avian pathogen Mycoplasma gallisepticum strain PG31 was examined. Transconjugants were obtained at a frequency of > or =6 x 10(-8) per recipient CFU. To determine the transposon insertion site, an oligonucleotide primer corresponding to the 3' end of Tn916 was designed for the purpose of directly sequencing genomic DNA without PCR amplification. Using the direct sequencing approach, Tn916 was shown to insert into any of numerous sites in the M. gallisepticum genome. This is the first report of conjugal transposition of Tn916 into the M. gallisepticum genome. The ability to determine transposon insertion sites in mycoplasmas by genomic sequencing has not been previously described and allows rapid sequence analysis of transposon-generated mutants.

Probable ceftiofur-induced cutaneous drug reaction in a cow.

A cow with pyelonephritis was treated with ceftiofur (3 mg/kg body weight, IV, q12 h). Hair loss and pruritus were observed after 8 and 12 d of treatment, respectively. Ancillary laboratory tests supported a diagnosis of allergic disease. Clinical signs and laboratory test results normalized after ceftiofur administration was stopped.

Use of xylazine, butorphanol, tiletamine-zolazepam, and isoflurane for induction and maintenance of anesthesia in ratites.

Anesthetic effects of xylazine, butorphanol, tiletamine-zolazepam, and isoflurane in ratites (9 emus, 3 rheas, 6 ostriches) were determined. Anesthetic treatments included 4 regimens: induction and maintenance of anesthesia with isoflurane, preanesthetic tranquilization with xylazine and butorphanol followed by induction and maintenance of anesthesia with isoflurane, induction of anesthesia with tiletamine-zolazepam and maintenance with isoflurane, and preanesthetic tranquilization with xylazine and butorphanol followed by induction of anesthesia with tiletamine-zolazepam and maintenance with isoflurane. None of the birds developed irreversible adverse effects, but 2 developed brady cardia (1 was treated with atropine and responded) and 2 others developed transient apnea. Intravenous administration of tiletamine-zolazepam produced rapid and smooth induction of anesthesia in adult ostriches.

Uterine torsion associated with small intestinal incarceration in a mare at 126 days of gestation.

A mare at 126 days of gestation was examined because of signs of abdominal pain. The cause of abdominal pain could not be determined by physical examination. Lack of response to analgesics and small intestinal distention on palpation per rectum prompted exploratory celiotomy. Small intestine was found to be entrapped by the uterus, which had undergone torsion. The uterus was returned to its correct position, and the small intestine was decompressed. After surgery, the mare was treated with orally administered progestin to prevent abortion. The mare recovered and delivered a live foal at 354 days of gestation. Uterine torsion at such an early stage of gestation is not common in horses.

Pharmacokinetics of caffeine in lactating dairy cows.

Because caffeine is metabolized by the hepatic P-450 cytochrome oxidase system, clearance of caffeine is an excellent quantitative test of hepatic function in human beings. It is currently used in much the same way that creatinine clearance is used to assess renal function. Caffeine clearance was measured in lactating dairy cows initially to determine the suitability of caffeine clearance as an indicator of hepatic function in cattle. Pharmacokinetic variables of caffeine were studied in 6 adult lactating dairy cows after i.v. administration of a single dose of caffeine sodium benzoate (2 mg of caffeine/kg of body weight). Caffeine concentration was analyzed by use of an automated enzyme immunoassay. The lower limit of detection of the assay for caffeine in serum was 0.079 micrograms/ml. Serum caffeine concentration-time curves best fit an open two-compartment pharmacokinetic model. Harmonic mean elimination half-life was 3.8 (range, 2.6 to 6.9) hours, and total clearance was 0.118 (range, 0.090 to 0.197) L/kg/h. Milk caffeine concentration was similar to serum concentration 1.5 to 24 hours after caffeine administration. Adverse effects were not observed in cows given caffeine.

An investigation of the role of Fusarium moniliforme in duodenitis/proximal jejunitis of horses.

Duodenitis/proximal jejunitis syndrome (DPJ) is a small intestinal disease of horses that is associated with depression and copious gastric reflux. Since an infectious cause for DPJ remains unsubstantiated, these studies were designed to investigate the possible role of Fusarium moniliforme toxins in this disease. Fusarium moniliforme was isolated by culturing 2 samples of feed that had been fed to horses with clinical signs of DPJ. These isolates (AU 2/3) were subsequently grown concurrently on autoclaved corn and their toxicity evaluated in a feeding trial utilizing horses. Isolates of F moniliforme known to be low and high producers (RRC 415 and MRC 826, respectively) of fumonisin B1 (FB1) were cultured individually on corn and each fed separately to other groups of horses. Control horses were fed autoclaved corn that was not inoculated with fungus. Production of FB1 by isolates RRC 415, MRC 826 and AU 2/3 were 19, 4360 and 1455 ppm, respectively. Each group contained 2 horses and the test diets were prepared by diluting culture material with sweet feed and clean corn. The test diets consisted of control corn that contained < 1 ppm FB1, RRC 415 diluted to < 1 ppm FB1, MRC 826 diluted to 200 ppm FB1, and AU 2/3 culture material diluted to contain 65 ppm FB1 on days 1-10 and 130 ppm on days 11-27. Horses fed either MRC 826 or AU 2/3 had elevated serum gamma-glutamyltransferase after 7 to 21 d exposure and elevated serum L-iditol dehydrogenase activity after 7 to 19 d exposure to test diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Caffeine clearance in the horse.

The pharmacokinetic properties of intravenously administered caffeine were studied in 10 horses using a commercially available automated enzyme immunoassay. The harmonic mean for the distribution half-life was 5.2 min (range 1.4-18.7). The harmonic mean for the elimination half-life was 10.18 h (range 6.82-20.92). The harmonic mean of the volume of distribution was 0.32 L/kg (range 0.22-0.53). There was no correlation between the dose of caffeine/kg body weight and the elimination half-life (Spearman's coefficient of rank correlation = 0.19).

Immunization and immunotherapy for mastitis.

Immunization and immunotherapy for mastitis are active areas of investigation. The past decade has seen development of effective and economical R-mutant vaccines for gram-negative mastitis. These vaccines doubtless will prove beneficial on well managed dairies that have eradicated contagious mastitis pathogens. Development of vaccines for other mastitis pathogens has been noticeably slower. A commercially available Staphylococcus aureus vaccine appears to reduce the frequency and severity of clinical episodes, but probably has minimal impact on the incidence or prevalence of infection. This product has not been extensively studied. The recent recognition of virulence factors produced in vivo by Staphylococcus aureus may provide a breakthrough in the development and production of Staphylococcus aureus vaccines. Bacterins employing this principle presently are not commercially available, however. In the case of all contagious mastitis pathogens (Streptococcus agalactiae, Staphylococcus aureus, and Mycoplasma spp.), traditional control and eradication efforts (teat dip, dry cow therapy, culling programs) likely will prove preferable to long-term immunization. Ongoing research may provide more efficacious vaccines for these mastitis syndromes. Immunostimulants are an active area of research. Although leukopoietic factors appear promising as immunostimulants, no compound has clearly demonstrated efficacy in either the prevention or treatment of bovine mastitis.