Comparison of the bacterial and fungal flora in the pharynx of normal horses and horses affected with pharyngitis

A total of 43 horses were used for the study of the pharyngeal bacterial flora. The median value of the number of bacteria in the group of 19 normal horses was 3.8 × 10⁴ cfu/g of secretions. This value was 6.4 × 10⁴cfu/g in horses with grade I pharyngitis, 1.3 × 10⁵ cfu/g in horses with grade II pharyngitis and 3.5 × 10⁶ cfu/g in horses affected with grades III and IV pharyngitis. Corynebacterium spp, coagulase-negative staphylococci, Nocardia spp, Moraxella spp and Enterobacter spp were the most frequently encountered bacteria in the normal animals as well as in horses affected with pharyngitis of grades I or II. Moraxella spp were isolated in 87.5% of the horses with pharyngitis of grades III and IV, followed by Streptococcus zooepidemicus, Pseudomonas aeruginosa, coagulase-negative staphylococci and Enterobacter spp. No fastidious bacteria, nor strict anaerobes were isolated from any of the 43 horses. None of the microorganisms were found in 100% of the animals and the majority of the isolates were opportunistic bacteria. These results demonstrate that the isolation of Moraxella spp and S. zooepidemicus in large numbers is frequent in horses with lymphoid follicular hyperplasia grades III and IV. Fungi were isolated in small numbers from two or three horses in each group.     

Cytology of the lower respiratory tract in horses: An updated review

The diagnosis of respiratory diseases in horses can be difficult due to the nonspecific nature of the clinical signs, which overlap between the different diseases. Cytological examination of the respiratory secretions is a helpful diagnostic tool that, when combined with clinical features and other diagnostic techniques, has the potential to improve diagnostic accuracy significantly. This review article should help readers to become familiar with the cytology of the normal respiratory tract and with the cytopathological abnormalities associated with common respiratory disorders in horses.     

Immunofluorescent evaluation of the lower respiratory tract of healthy horses and of horses with chronic bronchiolitis

Pulmonary parenchymal tissues from 6 healthy horses and from 9 horses with chronic bronchiolitis were evaluated by use of an indirect immunofluorescent technique. In horses of both groups, the diffuse interstitial immunofluorescence was most intense for immunoglobulin (Ig)G, moderate for IgA, and minimal for IgM. Intensity of fluorescence was increased markedly in diseased lungs exposed to anti-IgA and anti-IgG. Around small bronchi and large bronchioles of healthy horses, IgA-containing cells generally were more numerous than were IgG-Fc fragment (Fc)-containing cells; in small bronchioles, however, IgA-containing cells and IgG (Fc)-containing cells were identified with approximately equal frequency. Immunoglobulin-containing cell types usually were located in the lamina propria and submucosa of airways, with occasional Ig-containing cells seen interepithelially and intraluminally; IgG (T)- and IgM-containing plasma cells were observed infrequently in the same regions. The number of Ig-containing cells became fewer as the diameter of the airway decreased; therefore, at the level of the terminal bronchiole, Ig-containing cells only were observed occasionally. This pattern of Ig-containing cell distribution was similar in horses with chronic bronchiolitis; however, horses with chronic bronchiolitis had more IgA-containing cells forming perivascular and peribronchiolar cuffs than did healthy horses. The number of IgG (Fc)-containing lymphocytes and non-Ig-stainable lymphocytes also were higher in horses with chronic bronchiolitis than in healthy horses, but the number did not approach the magnitude of that observed for IgA-containing cells. One horse had deposits of complement C3 and IgG (Fc) within alveolar septa.     

Retrospective study of the relationships between age, inflammation and the isolation of bacteria from the lower respiratory tract of thoroughbred horses

A total of 1235 tracheal aspirates taken from 724 thoroughbreds in race training, aged from two to 10 years, were examined cytologically and bacteriologically. An inflammation scoring system on a scale of 0 to 9 was devised to allow the severity of lower airway disease to be assessed from the cytological results. The inflammation scores were closely related to the isolation of bacteria (P<0.001), and the most common bacterial isolates were Streptococcus zooepidemicus, Streptococcus pneumoniae and Pasteurella/Actinobacillus-like species. Lower airway disease was less common in older horses (P = 0.031), and the groups at highest risk were the two- and four-year-olds. Lower airway inflammation was more common in the four-year-olds at National Hunt yards than in the four-year-olds at flat racing yards (P = 0.040, odds ratio = 3.80).     

Aerobic and anaerobic bacterial isolates from horses with pneumonia or pleuropneumonia and antimicrobial susceptibility patterns of the aerobes

Frequency of aerobic and anaerobic isolates in 327 aspirates and in 123 pleural fluid samples from 327 horses with pneumonia or pleuropneumonia and antimicrobial susceptibility patterns of the aerobes were reported. Of the 327 horses, 75% survived, 20% were euthanatized, and 5% died. Tracheobronchial aspirates or pleural fluid specimens from 25 of the horses did not yield growth. Of the remaining 302 horses, 221 had only aerobic organisms isolated, whereas only anaerobes were isolated from 6 of the 302 horses. The remaining 75 horses had mixed aerobic and anaerobic bacterial infections. The survival rates for horses with aerobic only isolates was twice that of horses with anaerobic isolates. The aerobic bacteria most frequently isolated were beta-Streptococcus spp, Pasteurella spp, Escherichia coli, and Enterobacter spp. The anaerobic species most frequently isolated were Bacteroides spp and Clostridium spp.     

Isolation of mycoplasma species from the lower respiratory tract of healthy cattle and cattle with respiratory disease in Belgium

Between 1997 and 2000, a total of 150 healthy cattle and 238 animals with respiratory disease were examined for six Mycoplasma species. Attempts were made to detect Mycoplasma canis, Mycoplasma dispar and Ureaplasma diversum in calves with recurrent disease, and all three of these species were identified in calves with recurrent disease and in healthy lungs. In healthy calves, 84 per cent of bronchoalveolar lavage fluids were mycoplasma free; when cultures were positive, Mycoplasma bovirhinis was the only species isolated. Mycoplasmas were isolated from 78 per cent of animals suffering recurrent respiratory disease and from 65 per cent of acute respiratory cases. Mycoplasma bovis was isolated from bronchoalveolar lavages from 35 per cent of calves suffering recurrent respiratory disease, and from 50 per cent of acute cases, and from 20 per cent of pneumonic cases examined postmortem. M bovis was associated with other Mycoplasma species in 44 per cent of cases. M dispar was also isolated from 45.5 per cent of calves suffering recurrent respiratory disease, often in association with M bovis. M canis was identified for the first time in diseased Belgian cattle. Other mycoplasmas, including Mycoplasma arginini, Mycoplasma alkalescens and U diversum, were isolated less frequently. Associations between mycoplasmas and other pathogens were often observed. Among lungs infected with Pasteurella and/or Mannheimia species, more than 50 per cent were mixed infections with M bovis.     

The effects of age, environmental temperature and relative humidity on the bacterial flora of the upper respiratory tract in calves

The effects of age, environmental temperature and relative humidity on the bacterial flora of the nose and trachea of calves were investigated by sequential sampling of three groups each of eight Friesian-Holstein male calves kept in three different environmental conditions. All calves were vaccinated with a live attenuated vaccine against infectious bovine rhinotracheitis (IBR) when they were 12 weeks old. Nasal and tracheal swabs were collected at 14-day intervals for bacteriological examinations. The upper respiratory tract of calves started to be colonized by various species of bacteria within the first day of life. Although they were born at different periods of the year, the calves in all three groups had similar bacterial loads in their noses and tracheas when they were 1 day old (P greater than 0.05). The total bacterial colony forming units (BCFU) were highly variable from calf to calf and from one time of sampling to another. Despite these variations, there were age-related increases in the total BCFU in nasal and tracheal swabs in all experiments. These increases were influenced by environmental temperature. Vaccination of the calves with a live IBR vaccine appeared to enhance the bacterial colonization of the upper respiratory tract.     

Changes in the bacterial flora of the upper and lower respiratory tracts and bronchoalveolar lavage differential cell counts in feedlot calves treated for respiratory diseases.

Serial nasopharyngeal swab and bronchoalveolar lavage cultures were used to estimate changes in the bacterial flora of the respiratory tracts of calves during the first month after arrival in the feedlot. Bronchoalveolar lavage (BAL) differential cell counts served to evaluate pulmonary inflammatory changes during this period. Two groups of calves were studied, one consisting of clinically normal controls (n = 60), the other, of cases (n = 59) which received treatment for respiratory disease (penicillin +/- trimethoprimsulfadoxine). A variety of organisms, including Pasteurella multocida, Pasteurella haemolytica, Haemophilus somnus, Mycoplasma bovis and Mycoplasma bovirhinis, were present in the upper and lower airways of both groups during the postarrival period. With the exception of M. bovis, an overall decline in the prevalence of these organisms was observed during the course of the study. In cases, there was a marked decrease in the number of Pasteurella spp. and H. somnus isolates immediately following treatment. For the Pasteurella spp., however, this effect was shortlived as they often appeared to recolonize the respiratory tract within eight days of terminating antimicrobial therapy. Treatment did not appear to affect the frequency of isolating M. bovis. Its prevalence, in both groups of calves, increased to levels approaching 100% during the course of the study. All Pasteurella spp. isolates were tested for susceptibility to several commonly used antimicrobials. Resistance was only evident among P. haemolytica isolated from cases and in every instance this was to a combination of penicillin, ampicillin and tetracycline. Significantly more isolates were resistant after treatment than before. There were BAL differential cell count abnormalities indicative of inflammation in both cases and controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization studies on mycoplasmas isolated from bovine mastitis and the bovine respiratory tract.

Mycoplasmas isolated from bovine mastitis in California were classified into five distinct species. These included Mycoplasma bovis, M. bovigenitalium, M. alkalescens, M. canadenfe, and an unidentified strain, ST-6. Strains frequently recovered from the nose of young calves proved to be M. arginini, M. bovirhinis was recovered from the respiratory tract but was not a common finding.     

Inflammation and increased numbers of bacteria in the lower respiratory tract of horses within 6 to 12 hours of confinement with the head elevated

SUMMARY: Confinement of horses with their heads elevated for periods up to 24 hours was used to evaluate the extent and the effects of bacterial contamination of the equine lower respiratory tract. Significant (P < 0.05) increases in bacterial numbers (up to 10⁹ colony forming units/mL in transtracheal aspirate derived samples) occurred within 6 or 12 hours in most horses. Pasteurella/Actinobacillus spp and Streptococcus spp were most commonly isolated. Lowering of the head for 30 minutes every 6 hours to facilitate postural drainage did not prevent multiplication of organisms to levels equivalent to those achieved by horses where the head was elevated for 24 hours. When horses were released from confinement and heads were no longer maintained in an elevated position, clearance of accumulated secretions and bacteria occurred within 8 to 12 hours. Thus, confinement with the head elevated resulted in significant bacterial contamination and multiplication within the lower respiratory tract during a period often encountered in routine management procedures, such as transportation. The clearance of accumulated secretions occurred over a prolonged period after release from such confinement.     

Assessment of pain associated with bovine respiratory disease and its mitigation with flunixin meglumine in cattle with induced bacterial pneumonia

Pleuritic chest pain from bacterial pneumonia is often reported in human medicine. However, studies investigating pain associated with bovine respiratory disease (BRD) are lacking. The objectives of this study were to assess if bacterial pneumonia elicits a pain response in calves with experimentally induced BRD and to determine the analgesic effects of transdermally administered flunixin. A total of 26 calves, 6–7 mo of age, with no history of BRD were enrolled into one of three treatment groups: 1) experimentally induced BRD + transdermal flunixin at 3.3 mg/kg twice, 24 h apart (BRD + FTD); 2) experimentally induced BRD + placebo (BRD + PLBO); and 3) sham induction + placebo (CNTL + PLBO). Calves induced with BRD were inoculated with Mannheimia haemolytica via bronchoalveolar lavage. Outcomes were collected from −48 to 192 h post-treatment and included serum cortisol, infrared thermography, mechanical nociceptive threshold, substance P, kinematic gait analysis, visual analog scale (VAS), clinical illness score, computerized lung score, average activity and rumination level, prostaglandin E₂ metabolite, plasma serum amyloid A, and rectal temperature. Outcomes were evaluated using either a generalized logistic mixed model for categorical variables or a generalized linear mixed model for continuous variables. Right front force differed by treatment (P = 0.01). The BRD + PLBO had lower mean force applied to the right front limb (85.5 kg) compared with BRD + FTD (96.5 kg; P < 0.01). Average VAS differed by a treatment by time interaction (P = 0.01). The VAS scores differed for BRD + PLBO at −48 (3.49 mm) compared with 168 and 192 h (13.49 and 13.64 mm, respectively) (P < 0.01). Activity for BRD + PLBO was higher at −48 h (27 min/h) compared with 48, 72, 120, and 168 h (≤ 22.24 min/h; P < 0.01). Activity differed by a treatment by time interaction (P = 0.01). Activity for BRD + FTD was higher at −48 and 0 h (28.2 and 28.2 min/h, respectively) compared to 48, 72, 96, and 168 h (≤23.7 min/h; P < 0.01). Results show a combination of reduced activity levels, decreased force on the right front limb, and increased VAS pain scores all support that bacterial pneumonia in cattle is painful. Differences in right front force indicate that flunixin transdermal may attenuate certain pain biomarkers in cattle with BRD. These findings suggest that BRD is painful and analgesic drugs may improve the humane aspects of care for cattle with BRD.     

Removal of hair surrounding the teat and associated bacterial counts on teat skin surface, in milk, and intramammary infections

The effectiveness of monthly removal of hair surrounding teats on the reduction of teat skin surface bacteria, and the incidence of intramammary infection (IMI), was studied for 10 months in a dairy farm. A split udder design was used where hair was removed on one side, left or right, with the other side serving as a control. Controls and treatment sides were randomly applied in a systematic fashion to 218 cows. Standard milking time pre- and post-milking hygiene practices were applied to all udders during the trial. Collection of teat skin swab solutions preceded aseptic collection of milk samples, performed at monthly intervals, immediately prior to milking. Teat skin bacterial counts did not differ between control and treated teats. Incidences of IMI were similar for treatment when compared with control mammary quarters, as measured by total or by pathogen type. In a second study, the effect of hair removal on the bacterial content of milk was determined using 40 cows. Treatments and allocations were as described. Udder half milk, milk from both mammary quarters of each udder half, was combined and diverted into separate buckets. Buckets were thoroughly cleaned and sanitized between milkings. A portion of bucket milk was collected 24 h after removal of udder hair. The total milk bacterial counts, and counts of psychrotrophs and thermoduric organisms were not reduced by udder hair removal. Results do not suggest that removal of udder hair leads to an improvement in milk quality as determined by milk bacterial content in the herd studied.     

Perinatal development of lymphoid tissue and its associated epithelium in the ovine pharyngeal tonsil: a morphological study

The perinatal development of lymphoid tissue and its associated epithelium in the pharyngeal tonsil of sheep was investigated by light and electron microscopy. The lymphoid cells first appeared in the subepithelium in a scattered form at about 92 days gestation. These cells proliferated rapidly during the last trimester of gestation, and had formed many dense aggregates at the time of parturition. At birth, the epithelium overlying the aggregates was extensively infiltrated with lymphocytes and showed early transformation of follicle-associated epithelium. The lymphoid tissue and its associated epithelium did not, however, fully develop until after birth, when well-differentiated follicle-associated epithelium and lymphoid follicles with vigorous lymphopoiesis were present. In 1-2 week old lambs, these structures were ultrastructurally similar to those seen in adult sheep although their size was smaller. The results of this study suggest that the lymphoid tissue of the ovine pharyngeal tonsil and its associated epithelium are morphologically ready to cope with antigens in the extra-uterine environment at birth, but that their full development and maturation are dependent postnatal antigen stimulation.     

Cell biological and molecular characteristics of pseudorabies virus infections in cell cultures and in pigs with emphasis on the respiratory tract

In the present review, several cell biological and molecular aspects of virus-cell and virus-host (pig) interactions are reviewed for pseudorabies (Aujeszky's disease) virus. Concerning the virus-cell interactions, the complex cascade of events in the virus replication cycle is given together with the different mechanisms of cell-to-cell spread. The pathogenesis of pseudorabies virus infections in pigs is concentrated on the sequence of events in the respiratory tract. Finally, a short overview is given on the control of the disease and eradication of the virus by the combination of marker vaccines and discriminating ELISA.     

The incidence and distribution of peripheral caries in the cheek teeth of horses and its association with diastemata and gingival recession

Although considered relatively common in horses, there is little information on the prevalence, distribution and aetiology of peripheral caries of the equine cheek teeth (CT). The objective of this study was to investigate a possible association between this lesion and diastemata or 'gaps' between the CT which facilitate the entrapment of food material. Video recordings of oroscopic examinations of all dental cases at an equine hospital over a 3-year period were reviewed, and the location of all diastemata, peripheral caries, trapped food, and of gingival recession were recorded. A total of 108 cases met study inclusion criteria and 298 diastemata and 445 CT with peripheral caries were noted. Diastemata were found predominantly in the mandibular arcades (80%) and 75% of animals had at least one diastema. Peripheral caries was uniformly distributed between the maxillary and mandibular CT, being most prevalent on the most caudal three teeth (87%). Overall, diastemata were not associated with peripheral caries at either a tooth or individual patient level. However, a highly significant association was found between the presence of trapped food within diastemata and gingival recession.