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Abstract

Objective—To develop a method for experimental induction of equine rhinitis A virus (ERAV) infection in equids and to determine the clinical characteristics of such infection.

Animals—8 ponies (age, 8 to 12 months) seronegative for antibodies against ERAV.

Procedures—Nebulization was used to administer ERAV (strain ERAV/ON/05; n = 4 ponies) or cell culture medium (control ponies; 4) into airways of ponies; 4 previously ERAV-inoculated ponies were reinoculated 1 year later. Physical examinations and pulmonary function testing were performed at various times for 21 days after ERAV or mock inoculation. Various types of samples were obtained for virus isolation, blood samples were obtained for serologic testing, and clinical scores were determined for various variables.

Results—ERAV-inoculated ponies developed respiratory tract disease characterized by pyrexia, nasal discharge, adventitious lung sounds, and enlarged mandibular lymph nodes. Additionally, these animals had purulent mucus in lower airways up to the last evaluation time 21 days after inoculation (detected endoscopically). The virus was isolated from various samples obtained from lower and upper airways of ERAV-inoculated ponies up to 7 days after exposure; this time corresponded with an increase in serum titers of neutralizing antibodies against ERAV. None of the ponies developed clinical signs of disease after reinoculation 1 year later.

Conclusions and Clinical Relevance—Results of this study indicated ERAV induced respiratory tract disease in seronegative ponies. However, ponies with neutralizing antibodies against ERAV did not develop clinical signs of disease when reinoculated with the virus. Therefore, immunization of ponies against ERAV could prevent respiratory tract disease attributable to that virus in such animals.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize the impact of Mannheimia haemolytica infection on feed intake and weight gain in feedlot heifers and to evaluate the clinical efficacy of isoflupredone acetate administered in combination with oxytetracycline.

Animals—96 weanling heifers in a research feedlot facility.

Procedures—Bronchopneumonia was induced by intrabronchial infusion of M haemolytica. Control heifers underwent a sham procedure. Infected heifers were treated with oxytetracycline alone or in combination with isoflupredone acetate (OXY-ISO) or with nothing. Clinical variables were recorded daily for 7 days following disease induction, and feedlot performance indices were measured over a 12-week period.

Results—Infection caused a reduction in dry-matter intake and average daily gain (ADG) in heifers that received no treatment. Oxytetracycline treatment alone did not prevent reductions in feed intake and ADG during the first week after infection was induced, whereas OXY-ISO treatment did prevent these reductions. Treatment with OXY-ISO also resulted in faster clinical improvement. No significant differences were evident between the oxytetracycline and OXY-ISO groups with respect to dry-matter intake or ADG throughout the study period.

Conclusions and Clinical Relevance—Isoflupredone acetate appeared to be a useful clinical adjunct to treatment with oxytetracycline in cattle with acute M haemolytica bronchopneumonia.

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate a 5-hydroxytryptamine type-2 receptor antagonist, metrenperone (MET), in alleviating respiratory distress associated with experimentally induced Pasteurella haemolytica pneumonia in feedlot calves.

Design

Double-blind controlled clinical trial.

Animals

30 healthy 6- to 8-month-old Hereford-type calves (250 to 450 kg).

Procedure

Initial measurements were made of rectal temperature (RT), arterial blood gas (ABG) tensions, and pulmonary mechanics. Calves were then infected with P haemolytica in logarithmic phase of growth by intratracheal inoculation. 18 hours later, determination of RT and ABG tensions, and pulmonary function testing were repeated and calves were selected for inclusion in the study on the basis of having 2 of the following: respiratory rate > 50 breaths/mm, RT > 40 C, or Pao2 > 20 mm of Hg below the baseline value. MET (0.1 mg/kg of body weight, IM) or an equivalent vehicle dose was then administered. RT, ABG, and pulmonary mechanics measurements were repeated at 0.5, 1, 2, 3, 4, 6, 12, and 24 hours after treatment. Calves were then euthanatized, and gross necropsy scoring and histologic examination were performed on the lungs.

Results

Infection with P haemolytica caused significant increases in RT and respiratory rate, and reduction in Pao2 , Paco2 , and tidal volume 18 hours after inoculation. MET-treated calves had significantly reduced rectal temperature between 1 and 12 hours, compared with vehicle-treated calves. In addition, MET-treated calves had reduced respiratory rate with concomitantly increased tidal volume between 0.5 and 2 hours after treatment, compared with vehicle-treated calves. Necropsy revealed acute lobar bronchopneumonia in all 30 calves, but there was no difference in necropsy score between treatment groups.

Conclusions and Clinical Relevance

MET may have an antipyretic effect on calves with pneumonia caused by P haemolytica. Its influence on pulmonary mechanics was minimal however, and it did not induce lung lesions in the short term. (Am J Vet Res 1996;57:1034–1039)

Free access
in American Journal of Veterinary Research

Summary

A retrospective, epidemiologic study was performed to quantify the mixing of calves from various sources at auction markets, and to determine whether mixing at the markets and the risk of fatal fibrinous pneumonia (ffp) at the feedlot were associated. In this study, 32,646 spring-born steer calves that entered a single large feedlot during the fall seasons between 1985 and 1988 were traced back to their originating auction market, and sales tickets were used to measure the number of farm sources that contributed to each truckload of calves. Individual cow/calf producers contributed a median of only 2 calves/truckload arriving at the feedlot in this study. An average truckload of 60 steers comprised calves from as many as 20 to 30 farms. The degree of mixing varied little over time and could not, therefore, be used to explain the large variations in ffp risk during different months and different years of the study. However, variation in the degree of mixing of calves from various sources at the markets evidently was responsible for differences in ffp risk among truckloads assembled by different buyers. When truckloads were grouped by buyer, ffp risk and mean number of calves per source were negatively correlated in 1986 (r = -0.67, P = 0.099), and in 1987 (r = –0.90, P = 0.002). These variables also were negatively correlated in 1988 (r = –0.56), although the correlation was not significant.

The positive linear relationship between mixing of calves in truckloads supplied by different buyers and subsequent ffp risk suggested that veterinarians and feedlot owners should more aggressively observe and treat calves from truckloads that were highly mixed. However, the finding that mixing was constant over time, while ffp risk varied significantly within and between years, indicated other important factors also were responsible for the variation in disease prevalence.

Free access
in Journal of the American Veterinary Medical Association

Summary

A retrospective, epidemiologic field study was performed to determine whether calves that were transported greater distances from the auction market to the feedlot were at significantly higher risk of developing fatal fibrinous pneumonia (shipping fever). The study involved all 45,243 spring-born steer calves that were purchased from auction markets and moved into a large commercial feedlot between September 1 and December 31 over a 4-year period (1985–1988). For all 4 years of the study, the distance calves were transported from the market to the feedlot and their shrinkage or subsequent death loss from fibrinous pneumonia were not correlated. The risk of fatal fibrinous pneumonia for calves arriving from nearby markets was just as high as that for calves transported much greater distances. The results suggested that calves can be purchased from more distant markets without having to discount their price for higher expected death losses. Differences between short and long hauls explained/little, if any, of the variation among truckloads of calves in the risk of fatal fibrinous pneumonia.

Free access
in Journal of the American Veterinary Medical Association