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Bacterial pneumonia is a common cause of morbidity and mortality in foals of all ages.
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The most likely causal agents of bacterial pneumonia vary with the age of the foal, and knowledge of likely agents and their antimicrobial-resistance profiles is important for treatment selection.
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Macrolide antibiotics remain the treatment of choice for Rhodococcus equi infections, but resistance is emerging and effective alternatives are exiguous.
Update on Bacterial Pneumonia in the Foal and Weanling
Section snippets
Key points
Neonates
Neonatal foals may acquire pneumonia as a primary condition, but are more likely to develop bacterial pneumonia secondary to sepsis, the major cause of morbidity and mortality in the neonatal foal. Infection may occur in utero because of ascending infection of the fetal membranes or aspiration of contaminated fetal fluids. It also can occur at the time of parturition or during the postnatal period, whereby the respiratory tract, gastrointestinal tract, and umbilicus are all possible portals of
Physical Examination
The clinical evaluation of all animals should include thorough auscultation of the thorax. A rebreathing examination can be performed in animals not in respiratory distress to accentuate any abnormalities. It is important to note, however, that foals with significant pulmonary disease may have unremarkable thoracic auscultation.
Hematology and Biochemistry
Determining the white blood cell concentration with its differential cell count, plasma fibrinogen, and plasma chemistry with globulin determination can be helpful in
Pharmacologic treatment options
Antibiotics are the mainstay of therapy for bacterial pneumonia in foals of all ages. When treating neonates with presumed sepsis, broad-spectrum antimicrobial coverage should be initiated pending blood culture results, preferably with bactericidal drugs. Empirical therapy should be selected on the basis of patient signalment, cytologic characteristics of the organism, and knowledge of common local isolates. Common antimicrobials and suggested doses for foals are listed in Table 1. A common
Nonpharmacologic treatment options
Supplemental oxygen is indicated in any neonate with a level of Pao2 less than 60 mm Hg or a level of SaO2 less than 90%. Supplemental oxygen is most commonly performed with intranasal oxygen insufflation. It is difficult to predict the resulting fraction of inspired oxygen as it varies with cannula placement and patency as well as tidal and minute volume. Most foals necessitate between 2 and 15 L/min to maintain a level of Pao2 within an appropriate range. Complications include nasal mucosal
Treatment resistance/complications
Antimicrobial susceptibility patterns for the various bacteria reported to cause systemic sepsis and therefore pneumonia in the neonatal foal are location-specific and time period–specific and are reported elsewhere. It is worth noting that overall antimicrobial sensitivity is low and gram-positive organisms have unpredictable sensitivity patterns.1, 4, 5 Between the years of 1982 and 2007, there was no significant development of bacterial resistance to commonly used antimicrobials in one
Prevention
Prevention of neonatal pneumonia relies on management practices such as appropriate vaccination of pregnant mares, verification of transfer of passive immunity, and minimizing the risk of inhalation of pathogenic bacteria. As the foal matures, appropriate deworming and vaccination will decrease the risk of parasitic and viral pneumonias impacting the development of bacterial pneumonia. Currently, there are no effective, licensed vaccines for use in foals for bacterial pneumonia, although there
Evaluation of outcome
Survival rates of foals with sepsis have increased from 25% reported in the early 1980s70 to 70% currently.2, 3 Multiple factors have been associated with survival of septic foals in retrospective studies, but pneumonia as a specific feature of sepsis has not been shown to affect survival. Thoroughbred foals surviving sepsis do not differ from their siblings with regard to percentage of starters, percentage of winners, or number of starts, but they do have significantly fewer wins and total
Summary
Bacterial pneumonia remains an important cause of morbidity and mortality in foals of all ages. Early recognition and institution of appropriate treatment should result in a good prognosis for survival and athletic function.
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Cited by (21)
Antimicrobial Selection for the Equine Practitioner
2021, Veterinary Clinics of North America - Equine PracticeCitation Excerpt :Continued oral therapy: Trimethoprim-sulfonamide (TMS) may be appropriate for continued oral therapy for infections caused by susceptible organisms. Pneumonia in neonatal foals frequently occurs in association with septicemia; therefore, the predominant bacterial isolates and antimicrobials recommended for use are the same as those listed for septicemia in the preceding section.38,41,42 Polymicrobial infection is common, as it is in older foals and weanlings, in which the most frequent bacterial isolate is S zooepidemicus, followed closely by gram-negative nonenteric bacteria (A equuli, Actinobacillus spp, and Pasteurella spp).
Causes and Pathology of Equine Pneumonia and Pleuritis in Southern Brazil
2020, Journal of Comparative PathologyCitation Excerpt :Foals are frequently affected by bacterial pneumonia with neonatal foals prone to develop pneumonia as a consequence of sepsis. On the other hand, foals aged 1–6 months can develop primary pneumonia, which is often caused by Streptococcus equi subsp. zooepidemicus or Rhodococcus equi (Cohen, 2014; Reuss and Cohen, 2015). Young foals may also develop bronchointerstitial pneumonia caused by equine influenza virus (Patterson-Kane et al., 2008).
Differences in pig respiratory tract and peripheral blood immune responses to Actinobacillus pleuropneumoniae
2020, Veterinary MicrobiologyCitation Excerpt :Cytokines can play an important role in lung pathological damage as a consequence of infection. It is of great significance to fully understand the dynamic changes of cytokines in the course of bacterial pneumonia, a common disease with high incidence and of serious damage to humans (Lynch and Zhanel, 2009) and animals (Reuss and Cohen, 2015; Dione et al., 2018). The characteristics of the host immune response after APP infection are not fully understood, and more studies on inflammatory cytokines have been reported in recent years in order to understand the mechanism of the disease.
Cytological Findings in Bronchoalveolar Lavage Fluid of Foals With Pneumonia Caused by Rhodococcus equi and Other Bacteria
2019, Journal of Equine Veterinary ScienceCitation Excerpt :Selection criteria included evidence of pulmonary disease on physical examination (abnormal thoracic auscultation) and thoracic ultrasonography; BAL performed at their respective breeding farm, no requirement for hospitalization due to the respiratory disease; and results of cytology, bacterial culture, and polymerase chain reaction (PCR) of the BALF sampled. Thoracic auscultation was considered abnormal when crackles, wheezes, rubs, or abnormally increased bronchovesicular sounds were reported [17]. Thoracic ultrasonography, considered more sensitive than radiography in field conditions [18], was considered abnormal when ring-down artifact, consolidation areas, or abscessation were present [17].
Clinical Approach to Commonly Encountered Problems
2018, Equine Internal Medicine: Fourth Edition
The authors have nothing to disclose.