The 1-host tick Boophilus annulatus was found to transmit anaplasmosis in cattle transstadially. Anaplasma marginale was invariably transmitted when ticks that had been pulled off Anaplasma-infected calves either after 7 days (as fully engorged larvae) or after 14 to 15 days (as fully engorged nymphs) were transferred within 4 days to susceptible calves. Three morphologically different A marginale isolates, 1 round (tailless) and 2 with different types of appendages (tailed) were transmitted by the ticks. These findings might explain the overlap of the geographic distribution of the disease and that of Boophilus spp in some areas of the world.

Transcutaneous oxygen monitoring is commonly used in human beings to assess skin viability. Little attention has been directed toward the use of transcutaneous carbon dioxide (P(CO2.TC)) monitoring for the same purpose. The application of P(CO2.TC) monitoring for evaluating skin viability in dogs was investigated. The changes in P(CO2.TC) and local power reference (LPR) values were measured from 16 skin flaps created along the lateral hemithoraces of 4 dogs. Transcutaneous P(CO2) and LPR values were serially recorded from the base and apex of each flap for 12 hours. A single measurement was obtained from each flap base and apex 24 hours after surgery. Arterial blood gas analyses were obtained to compare central P(CO2) values with peripheral skin P(CO2) values. The flaps were observed for 4 days and then harvested for histologic examination. Full-thickness skin biopsy specimens were obtained 24 hours after surgery and when the flaps were harvested to evaluate the viability of the apex and base of the flaps. A subjective grade was assigned to all skin biopsy specimens during histologic examination. For all measurements, a significant difference was found between the P(CO2.TC) values for apices and bases of the flaps. The mean P(CO2.TC) for all bases was 52.66 mm of Hg +/- 2.24 (SEM), and the mean P(CO2.TC) for all apices was 106.4 mm of Hg +/- 2.44. The regional carbon dioxide index (apex P(CO2.TC)/base P(CO2.TC) was 2.02. A significant difference was not found between the LPR values for bases and apices. The mean LPR for all bases was 253.23 mW +/- 4.06, and the mean LPR for all apices was 243.53 mW +/- 4.49. A significant difference was found between the histologic grades assigned to the collective bases and apices 4 days after creation of the flaps. A difference was not found between the collective bases and apices 24 hours after flap creation. On the basis of our findings, transcutaneous carbon dioxide monitoring is a useful method of evaluating skin viability in dogs.

Development of the rickettsia, Anaplasma marginale, salivary glands of male Dermacentor andersoni exposed as nymphs or adult ticks, was studied indirectly by inoculation of susceptible calves with homogenates and directly by examination, using light microscopy and a DNA probe; some unfed ticks were incubated before tissues were collected. Salivary gland homogenates made from ticks in every treatment group caused anaplasmosis when injected into susceptible calves; prepatent periods decreased as the time that ticks had fed increased. Colonies of A marginale were seen only in salivary glands of ticks exposed as adults and not in those exposed as nymphs; the percentage of salivary gland acini infected in these ticks increased linearly with feeding time. However, the probe detected A marginale DNA in salivary glands of ticks from both groups; the amount of DNA detected increased as feeding time was extended. The amount of A marginale DNA appeared to remain constant in gut tissues, but to increase in salivary glands. Salivary glands of adult-infected male ticks that were incubated, but did not feed a second time, became infected with A marginale, and the pattern of infection of acini varied with incubation temperature. Development of A marginale in salivary glands appears to be coordinated with the tick feeding cycle; highest infection rate was observed in ticks exposed as adults.

An agar gel immunodiffusion (AGID) test was used over a 3-year period to examine 1,871 serum samples from sheep representing 5 Mycobacterium paratuberculosis infected flocks and 4 flocks presumed to be uninfected. Of 1,032 sheep, 31 had positive AGID test results (scoring 1 to 5), and 23 of these 31 were ecropsied. Infection with M paratuberculosis was confirmed by 1 or more of the following findings: observation of typical lesions on histologic examination of sections of ileum or ileocecal lymph nodes, observation of clumps of acid-fast bacteria in mucosal smears of ileum, and isolation of the organism from feces or tissue. False-positive results on AGID testing were not found in sheep from flocks known to have exposure to Cotynebacterium pseudotuberculosis. Diarrhea in infected sheep was observed infrequency; chronic, severe weight loss was the most common sign observed. On histologic examination of tissues from 20 infected sheep, 16 (80%) had diffuse lesions of the ileum and 13 (65%) had acid-fast bacteria in areas of ileal inflammation; 4 had discrete granulomas and peripheral lymphocytic infiltrates in the ileum. Sheep with diffuse lesions tended to have higher mean scores on AGID testing and examination for acid-fast bacteria, compared with those from sheep with more discrete lesions. Bacteriologic culture yielded M paratuberculosis from only 3 sheep with paratuberculosis. On the basis of results of this study, we suggest that the nature of the response to infection with M paratuberculosis may influence the results of diagnostic tests for paratuberculosis, and that AGID testing may be useful to identify M paratuberculosis infection in sheep with chronic weight loss and in flock-screening programs.

The prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavage specimens and the prevalence of mycoplasmal recovery from pharyngeal swab specimens from dogs with (n = 38) or without (n = 26) pulmonary disease were determined. Similar mycoplasmal recovery rates were found for tracheobronchial lavage specimens from dogs > 1 year old with (21%) or without (25%) pulmonary disease. Prevalence of mycoplasmal recovery from tracheobronchial lavages was significantly associated with pulmonary disease among dogs < 1 year old (P = 0.04), and with dogs that had concurrent Bordetella (P = 0.006) and Streptococcus (P = 0.05) isolations. Among dogs with pulmonary disease, mycoplasmas were significantly (P = 0.02) more prevalent in dogs with septic inflammation than in dogs with nonseptic inflammation of the tracheobronchial tree. Ureaplasmas were only isolated from a tracheobronchial lavage specimen of 1 dog with pulmonary disease and from none of the dogs without pulmonary disease. Most dogs with (84%) and all dogs without pulmonary disease had mycoplasmas isolated from the pharynx. Seemingly, mycoplasmas are part of the normal pharyngeal flora of most dogs and normal inhabitants of the lower airway in about a fifth to a fourth of the canine population greater than or equal to 1 year old. Dogs < 1 year old with pulmonary disease and dogs with concurrent Bordetella or tracheobronchial streptococcal isolations may be more susceptible to mycoplasmal colonization of the lower airways. Seemingly, ureaplasmas are rarely associated with pulmonary disease, and are not normal inhabitants of the trachea and bronchi of dogs.

One indication for referral of horses to veterinary hospitals is for diagnosis of the microbiologic cause of pneumonia, particularly when the initial treatment fails. Although endoscopic methods have long been available for microbiologic sample collection, accuracy of these methods under these conditions have not been studied in detail. We compared the bacteria isolated from samples obtained by bronchoalveolar lavage (BAL) with those obtained by protected catheter brush (PCB) from foals with unilateral pneumonia induced by inoculation with Klebsiella pneumoniae. As part of previously described clinical trials, foals were administered antimicrobial therapy IM (n = 15) or vehicle IM (n = 7), and collection of distal airway secretion samples was conducted during the treatment period. Sensitivity and specificity of the sample collection methods were assessed by comparison of the isolates from BAL or PCB samples with isolates from tissue of the inoculated lung lobe, which was the most severely affected lung region. Sensitivity and specificity of BAL for recovery of K pneumoniae (challenge strain) and Streptococcus zooepidemicus (common secondary pathogen) was 90 and 69%, respectively, compared with 76 and 85%, respectively, for the PCB method. Sensitivity was significantly (P = 0.03) higher for BAL (100%) than for PCB (69%) for recovery of K pneumoniae (P = 0.03) from lungs. However, difference in the sensitivity of these methods for recovery of S zooepidemicus was not significant. In conclusion, BAL was a more reliable method for recovery of bacteria from the lungs in chronically infected foals that received antimicrobial treatment.

The mechanism of estrogen-induced myelotoxicosis is unknown, although evidence indicates that estrogen does not directly damage the bone marrow granulocyte-macrophage progenitor cells and that the thymus is a probable mediator of the bone marrow suppression. Estrogen-induced production of a myelopoiesis-inhibitory factor by canine thymic stromal cells in vitro has been observed. Then, presence of a myelopoiesis-inhibitory factor in canine serum was investigated immediately after estrogen administration in vivo. Maximal reduction in colony-forming units-granulocyte/macrophage growth by sera from individual dogs varied. Individual dog sensitivity to estrogen-induced myelotoxicosis is seen clinically, and the cause is unknown. This serum factor could have a role in the eventual bone marrow hypoplasia seen in estrogen-treated dogs and is possibly the same factor produced by cultured thymic stromal cells exposed to estrogen.

Pepsinogen and protein concentrations were determined in blood samples, collected from the left gastroepiploic artery and vein, and in abomasal lymph from 15 steers naturally infected with Ostertagia ostertagi and 4 uninfected steers. In steers with type-1 ostertagiosis, the concentration gradient between the mucosal interstitium and the blood alone could account for higher than normal serum pepsinogen concentrations. High interstitial pepsinogen concentrations may have resulted from increased epithelial permeability or increased pepsinogen production and secretion. However, in steers with type-2 ostertagiosis, the concentration gradient could not entirely account for the high serum pepsinogen concentrations, suggesting that capillary permeability or surface area may have been altered. Lymphatic uptake contributed pepsinogen to the blood in all infected steers.

Accumulation of D-xylose by jejunal mucosa from healthy horses and rabbits was studied in Vitro. When tissue sheets were incubated with 1 mM D-xylose for 60 minutes, mucosa from horses and rabbits accumulated D-xylose against a concentration gradient. There was no accumulation when equine specimens were incubated with 5 mM D-xylose. By comparison, equine jejunum accumulated D-glucose against a concentration gradient when incubated in 5 mM D-xylose glucose. In equine and rabbit jejunum, 13.3 +/- 7.0% and 36 +/- 11.0%, respectively, of accumulated D-xylose was phosphorylated when sheets were incubated in 1 mM D-xylose. Short-circuit current and potential difference were lower in equine jejunum than in rabbit jejunum, possibly because of differences in tissue thickness. None of the transmucosal electrical measurements increased after addition of D-xylose (1 mM and 5 mM) or D-glucose (5 mM). The active transport system for D-xylose has a low affinity for this sugar and becomes saturated at low intraluminal concentrations. Therefore, abnormal D-xylose absorption test results in horses are more likely caused by abnormalities in mucosal surface area and mucosal permeability than by abnormalities of nutrient carbohydrate absorption.

Cardiovascular and at accompany markedly long periods (12 hours) of halothane anesthesia were characterized. Eight spontaneously breathing horses were studied while they were positioned in left lateral recumbency and anesthetized only with halothane in oxygen maintained at a constant end-tidal concentration of 1.06% (equivalent to 1.2 times the minimal alveolar concentration for horses). Results of circulatory and respiratory measurements during the first 5 hours of constant conditions were similar to those previously reported from this laboratory (ie, a time-related significant increase in systemic arterial blood pressure, cardiac output, stroke volume, left ventricular work, PCV, plasma total solids concentration, and little change in respiratory system function). Beyond 5 hours of anesthesia, arterial blood pressure did not further increase, but remained above baseline. Cardiac output continued to increase, because heart rate significantly (P < 0.05) increased. Peak inspiratory gas flow increased significantly (P < 0.05) in later stages of anesthesia. There was a significant decrease in inspiratory time beginning at 4 hours. Although PaO2, and PaCO2, did not significantly change during the 12 hours of study, PVO2 increased significantly P < 0.05) and progressively with time, beginning 6 hours after the beginning of constant conditions. Metabolic acidosis increased with time significantly [P < 0.05] starting at 9 hours), despite supplemental IV administered NaHCO3. Plasma concentrations of eicosanoids: 6-ketoprostaglandin F1 alpha (PGF1 alpha, a stable metabolite of PGI2), PGF2 alpha, PGE, and thromboxane (TxB2, a stable metabolite of TxA2) were measured in 5 of the 8 horses before and during anesthesia. Significant changes from preanesthetic values were not Significant changes from preanesthetic values were not detected. Dynamic thoracic wall and lung compliances decreased with time.