Effect of antibiotics on motion characteristics of cooled stallion spermatozoa.

The control of bacteria in semen of stallions has been most effective with the use of seminal extenders containing suitable concentrations of antibiotics. However, the detrimental effect of antibiotics on sperm motility may be greater in stored, cooled semen due to the prolonged exposure to the antibiotic. Therefore, a study was conducted to determine the effect of various antibiotics on sperm motion characteristics following short term exposure and during cooled storage of semen. Reagent grade amikacin sulfate, ticarcillin disodium, gentamicin sulfate and polymixin B sulfate were added to a nonfat, dried, skim milk - glucose seminal extender at concentrations of 1000 or 2000 mug or IU/ml. Aliquots of raw semen were diluted with extender-antibiotic combinations to a concentration of 25 x 10(6) spermatozoa/ml. An aliquot was also diluted with extender without antibiotic. Aliquots were incubated at 23 degrees C for 1 h. In addition, portions of the aliquots were cooled from 23 to 5 degrees C and stored for 48 h. During 1 h of incubation of extended semen at 23 degrees C, there was a significant (P<0.05) reduction in the percentage of progressively motile spermatozoa for samples containing gentamicin sulfate. After 24 h of storage at 5 degrees C, 2000 mug/ml of gentamicin and levels equal to and greater than 1000 IU/ml of polymixin B in seminal extender resulted in significant (P<0.05) reductions in the percentages of motile and progressively motile spermatozoa. After 48 h of cooled storage, a level of 1000 mug/ml of gentamicin sulfate. resulted in significant (P<0.05) reductions in the percentages of motile and progressively motile spermatozoa. Levels equal to or greater than 1000 IU/ml of polymixin B sulfate also resulted in a significant (P<0.05) reduction in mean curvilinear velocity. Levels up to 2000 mug/ml of amikacin sulfate and ticarcillin disodium had no significant effect on sperm motion characteristics during short-term incubation at 23 degrees C or storage for 24 h at 5 degrees C. Overall, the addition of antibiotics to extender did not significantly (P>0.05) improve motion characteristics of spermatozoa over control samples. However, levels of gentamicin sulfate greater than 1000 mug/ml and of polymixin B sulfate equal to or greater than 1000 IU/ml should be avoided in seminal extenders used for cooled semen.

Occurrence of infectious upper respiratory tract disease and response to vaccination in horses on six sentinel premises in northern Colorado.

REASONS FOR PERFORMING STUDY: Horses vaccinated against common agents of infectious upper respiratory disease (IURD) may not have detectable serum antibody and may not be protected from clinical disease. OBJECTIVES: The objectives of this study were to 1) investigate the serological response of horses to vaccination against influenza virus (H3N8 and H7N7) and equine herpesviruses (EHV) in a field setting and 2) evaluate associations among vaccination status, serum antibody concentrations, and occurrences of IURD in monitored horses. METHODS: In this study, horses on 6 Colorado premises were vaccinated parenterally against influenza virus and EHV, and serological response evaluated. Horses were monitored, and biological samples collected from individuals with clinical IURD and control horses. RESULTS: Of 173 horses, 61 (35.3%), 21 (12.1%) and 4 (2.3%) seroconverted in response to vaccination against EHV, influenza virus H7N7 and influenza virus H3N8, respectively. CONCLUSIONS: Outbreaks of IURD in study horses were associated with influenza virus H3N8 and Streptococcus equi infection, and serological response to vaccination with conventional products was poor. POTENTIAL RELEVANCE: These results confirm that horses may not respond with detectable serological responses to conventional vaccination against common respiratory viruses and, therefore, suggest that alternate methods of protecting horses against common respiratory viruses should be sought.

Survey of the large animal diplomates of the American College of Veterinary Internal Medicine regarding percutaneous lung biopsy in the horse.

A survey designed to obtain information on the indications, contraindications, complications, and methodology of percutaneous lung biopsy in the horse was sent to large animal diplomates of the American College of Veterinary Internal Medicine. Sixty-five of 190 diplomates returned the survey (response rate: 34%) and 59 of these 65 respondents (91%) indicated that they worked with horses. Forty-four diplomates had performed a percutaneous lung biopsy in 1 or more horses (i.e. 75% of those diplomates working with horses and 68% of total respondents). Clinical and radiologic diagnoses that prompted diplomates to perform percutaneous lung biopsy in the horse included a pulmonary miliary pattern (93%), suspicion of pulmonary infiltrative disease (91%), suspicion of pulmonary neoplasia (91%), suspicion of chronic obstructive pulmonary disease (COPD) (20%), and suspicion of exercise-induced pulmonary hemorrhage (EIPH) (7%). Only one of the respondents reported the use of percutaneous lung biopsy in the diagnostic workup if pneumonia was suspected, but 11% of respondents reported that suspicion of pulmonary abscessation would prompt them to perform a percutaneous lung biopsy. In contrast, a variable percentage of respondents felt there were contraindications to performance of this technique, which included neonatal septicemia (68%), pulmonary abscessation (65%), pleuropneumonia (55%) and pneumonia (42%), EIPH (41%), and COPD (26%). No respondent indicated that suspicion of neoplasia was a contraindication to percutaneous biopsy. Most common complications observed by respondents were epistaxis (68% of respondents), putative pulmonary hemorrhage (52%), tachypnea (39%), and respiratory distress (32%). Ten of 44 respondents (23%) had not seen any complications with percutaneous lung biopsy. Forty-two of 44 respondents (96%) warned owners about possible complications before performing percutaneous lung biopsy. All respondents to this question reported that they would perform percutaneous lung biopsies in horses in the future, but 4 of 41 would use the procedure only as a last resort.

Use of gonadotropin-releasing hormone, estrogen, or a combination to increase releasable pituitary luteinizing hormone in early transitional mares.

A lack of pituitary LH stores has been implicated as the cause of seasonal anestrus and failure to ovulate during the spring transition period in mares. In this experiment, 40 mares were used to study the effects of GnRH, estrogen, and an estrogen-GnRH combination on increasing releasable pituitary LH. Mares were stratified based on their ability to secrete LH in response to a 950-micrograms challenge of GnRH (n = 10 per group) and then assigned to one of four treatment groups: 1) controls, given no treatment; 2) 1 mg of estradiol-17 beta in oil i.m. daily for 8 d; 3) 200 micrograms of GnRH analogue des-Gly10, [D-ala6]-LHRH ethylamide in saline i.m. twice daily for 8 d; or 4) estradiol for 4 d then estradiol plus GnRH for four subsequent days. Blood was collected on d 1, 3, 5, and 7 of treatment, and serum was assayed for LH. On d 10 after initiation of treatment, mares were again challenged with GnRH (950 micrograms), and blood was collected for 4 h. Concentrations of serum LH did not vary significantly in control, estradiol-treated, or estradiol plus GnRH-treated mares among treatment days. In contrast, administration of GnRH alone increased (P < .05) concentrations of LH on d 5 and 7. Response to GnRH challenge, as measured by area under the LH curve (AUC) and peak LH, was greater (P < .05) for mares administered GnRH (7,307.1, 67.6 ng/mL, respectively) and GnRH plus estradiol (5,691.4, 60.3 ng/mL) than for mares given estradiol alone (1,519.4, 22.1 ng/mL) or no treatment (1,213.8, 19.4 ng/mL.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of various doses of a gonadotropin-releasing hormone analogue on induction of ovulation in anestrous mares.

One hundred anestrous mares (early February) were injected s.c. with implants containing 0, .9, 1.8, 3.6, or 5.4 mg of a GnRH analogue (goserelin acetate) in an attempt to induce ovarian cyclicity. Follicular activity and concentrations of progesterone and LH were determined every 3 d, or daily during estrus. In treated mares that ovulated, the interval to the second ovulation of the season was compared to that for an additional group receiving 16 h/d of light beginning December 16 (positive controls). Of the mares that did not ovulate in 30 d, eight from each dose group were challenged on d 33 or 34 with an i.v. bolus of 950 micrograms of GnRH. Blood collected at -2, -1, and 0 h before GnRH and at 15, 30, 45, 60, and 90 min and 2, 3, and 4 h after injection was assayed for serum LH. More mares (P < .05) ovulated when given 3.6- (n = 7) or 5.4-mg (n = 6) implants than when given .9-mg implants (n = 0) or placebo (n = 0). Mares with initial follicles < or = 15 mm in diameter were less (P < .05) likely to ovulate (10 of 88) than were those with follicles 16 to 20 mm in diameter (5 of 12). Area under the curve (AUC) for LH was greater for mares receiving larger doses of GnRH. The AUC and peak LH were similar between ovulating and nonovulating mares. Luteinizing hormone peaked in all mares on approximately d 12. There was no difference (P > .05) in either peak LH or AUC among treatment groups in response to the GnRH challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Management factors affecting the risk for vesicular stomatitis in livestock operations in the western United States.

OBJECTIVE: To identify management factors affecting the risk of animals developing vesicular stomatitis (VS). DESIGN: Case-control study. ANIMALS: Horses, cattle, and sheep with suspected vesicular stomatitis on 395 premises in Colorado, New Mexico, Utah, and Arizona. PROCEDURE: Data were collected during the VS outbreak of 1997. Diagnosticians interviewed livestock owners and completed a supplemental questionnaire. Cases were defined as those premises that had a completed questionnaire and had > or = 1 animal positive for VS. Control premises were all premises investigated that had a completed questionnaire and on which the animals had been tested but VS was not detected. RESULTS: Animals that had access to a shelter or barn had a reduced risk of developing VS (OR, 0.6; 95% confidence interval [CI], 0.35 to 0.99). This effect was more pronounced for equine premises (OR, 0.5; 95% CI, 0.3 to 0.9). Conversely, during an adjusted analysis on equine premises, risk of developing disease was increased slightly where animals had access to pasture (OR, 2.01; 95% CI, 1.1 to 3.7). On all premises where owners reported insect populations were greater than normal, odds of developing disease were significantly increased (OR, 2.5; 95% CI, 1.47 to 4.47). Premises with animals housed < 0.25 miles from running water were more than twice as likely to have clinical signs of VS (OR, 2.6; 95% CI, 1.32 to 5.0). CONCLUSIONS AND CLINICAL RELEVANCE: These results support reports of others that suggest biting insects are a vector in VS virus transmission. Management practices to reduce exposure to biting insects might reduce the risk of VS.

Public veterinary medicine: public health. Serologic evaluation of vesicular stomatitis virus exposure in horses and cattle in 1996.

OBJECTIVE: To determine potential risk factors for vesicular stomatitis (VS) in Colorado livestock in 1995 and evaluate VS virus (VSV) exposure of Colorado livestock in 1996. DESIGN: Retrospective case-control study of VS risk factors and seroprevalence evaluation. SAMPLE POPULATION: Premises included 52 that had VS-positive animals and 33 that did not have VS-positive animals during the 1995 epidemic, and 8 in the vicinity of premises that had VS-positive animals during the 1995 epidemic. PROCEDURE: Layout and management data for premises were collected during site visits in 1996. Signalment and management data were collected for animals from which samples were obtained, and samples were tested by serologic examination and virus isolation. The VSV seroprevalence rate was estimated for Colorado, using serum obtained for equine infectious anemia testing and from the Market Cattle Identification program in Colorado. RESULTS: At least 1 animal was seropositive for VSV on 35 of 52 (67%) premises, and 71 of 228 (31%) animals tested were seropositive for VSV. Seroprevalence was 63 of 170 (37%) for horses and 8 of 54 (15%) for cattle. Seroprevalence of VSV in animals from non-study premises in Colorado in 1996 was estimated to be 1.1% in cattle and 0.8% in horses. CLINICAL IMPLICATIONS: Overall VSV seroprevalence in Colorado livestock was less than seroprevalence in epidemic areas, and seroprevalence rates in epidemic areas were greater for horses than cattle. Results may indicate that some animals had subclinical VSV infection during epidemics and that animals may be exposed to VSV between epidemics.

Oral vesicular lesions in horses without evidence of vesicular stomatitis virus infection.

OBJECTIVE: To report clinical and serologic findings in horses with oral vesicular lesions that were consistent with vesicular stomatitis (VS) but apparently were not associated with VS virus (VSV) infection. DESIGN: Serial case study. ANIMALS: 8 horses. PROCEDURE: Horses were quarantined after appearance of oral lesions typical of VS. Severity of clinical signs was scored every 2 to 5 days for 3 months. Serum samples were tested for antibodies by use of competitive ELISA (cELISA), capture ELISA for IgM, serum neutralization, and complement fixation (CF). Virus isolation was attempted from swab specimens of active lesions. RESULTS: 2 horses with oral vesicular lesions on day 1 had antibodies (cELISA and CF) against VSV; however, results of CF were negative by day 19. Five of the 6 remaining horses were seronegative but developed oral lesions by day 23. Virus isolation was unsuccessful for all horses. CONCLUSIONS AND CLINICAL RELEVANCE: Horses were quarantined for 75 days in compliance with state and federal regulations. However, evidence suggests that oral lesions were apparently not associated with VSV infection. The occurrence in livestock of a vesicular disease that is not caused by VSV could confound efforts to improve control of VS in the United States and could impact foreign trade. Vesicular stomatitis is of substantial economic and regulatory concern.

Monitoring and detection of acute viral respiratory tract disease in horses.

OBJECTIVE: To develop a system to monitor and detect acute infections of the upper respiratory tract (i.e., nares, nasopharynx, and pharynx) in horses and to assess the association among specific viral infections, risk factors, and clinical signs of disease. DESIGN: Prospective study. ANIMALS: 151 horses with clinical signs of acute infectious upper respiratory tract disease (IURD) from 56 premises in Colorado. PROCEDURE: Health management data, blood samples, and nasal or nasopharyngeal swab samples were obtained for 151 horses with clinical signs of acute IURD. Of these horses, 112 had an additional blood sample obtained during convalescence and were considered to have complete sample sets. Samples were tested for evidence of respiratory tract infection by use of ELISA, virus isolation, and serologic testing of paired serum samples. RESULTS: Viral infections were identified in 65 horses with complete sample sets; influenza virus infection was identified in 43 horses, equine herpesvirus (EHV) infection in 18, and mixed influenza virus and EHV infections in 4. On 14 premises, samples were obtained from more than 1 affected horse. Viral infections were identified in horses on 11 of 14 premises. Equine herpesviruses were isolated from 10 horses. A relationship was not found between vaccination history and identification of EHV or influenza virus infections. An infection with EHV was less likely to be identified in horses with initial (acute) antibody titers > 1:16 to EHV. CLINICAL IMPLICATIONS: Influenza virus (specifically, A/equine/2) was the most common virus associated with acute IURD. Use of multiple diagnostic tests and obtaining samples from more than 1 horse in an outbreak may improve detection of viral infections.

Vesicular stomatitis and other vesicular, erosive, and ulcerative diseases of horses.

Physical trauma, dietary factors, certain toxins, immune mediated disorders, and vesicular stomatitis virus (VSV) infection are known causes of stomatitis in horses. There is evidence that some outbreaks of equine stomatitis are caused by as yet unidentified infectious agents. It remains to be determined whether stomatitis is an emerging equine infectious disease, or if the increase in reported cases is simply the result of greater public awareness as a consequence of widespread outbreaks of VSV in the southwestern United States in recent years. Focused laboratory and epidemiological studies are necessary to more adequately define non-VS related infectious and noninfectious causes of equine stomatitis.