Respiratory- other Flashcards
Estimation of the basic reproduction number for Streptococcus equi spp. equi outbreaks by meta-analysis of strangles outbreak reports
• The conservative estimate of R₀ is 2.2 (95% CI: 1.9–2.5).
• Including outbreaks with a 100% attack rate (AR) yields a higher estimate of 2.7 (95% CI: 2.1–3.3).
• S. equi R₀ is lower than equine influenza (R₀ = 2–10), which can transmit via aerosols and over greater distances.
• The R₀ for outbreaks in individual housing was 2.0 (95% CI: 1.3–2.6), compared to higher estimates for group housing- reduced contact opportunities
• Herd immunity threshold for S. equi is approximately 62% (based on R₀ = 2.7).
• Achieving this threshold requires vaccines with >68% efficacy, which is feasible given current vaccine developments.
Outbreak-specific variations in R₀ are influenced by:
• Herd size and composition (juvenile vs. mixed-age).
• Housing conditions (group vs. individual stalls).
• Potential reduction in bacterial virulence during prolonged persistence in carriers.
• Smaller herds are more susceptible to stochastic effects, leading to greater variability in outbreak size.
Clinical and Epidemiological Implications
• The relatively low R₀ suggests that modest improvements in biosecurity could significantly reduce transmission risk.
• Examples include isolation of infected animals, improved hygiene, and screening of new arrivals.
Potential for residual contamination by Streptococcus equi subspp equi of endoscopes and twitches used in diagnosis of carriers of strangles
• The study evaluates the efficacy of various disinfection methods for eliminating S. equi contamination from endoscopes and twitches.
• It addresses the risks of residual contamination and its potential to cause false-positive S. equi diagnoses or disease transmission.
3/4 disinfection methods effectively eliminated live S. equi bacteria:
• Automated Endoscope Reprocessor (AER) and manual cleaning with ortho-phthalaldehyde were the most effective.
• Ethanol-based disinfection (group A) failed in one sample, highlighting the risk of incomplete bacterial removal when using basic protocols.
Residual DNA Detection:
• No method completely eliminated S. equi DNA, as indicated by qPCR positivity in:
- 6/6 samples for ethanol-based cleaning.
- 1/6 samples for the AER method.
• Residual DNA could lead to false-positive qPCR results, complicating carrier identification.
Field Study Results:
• Endoscopes used on naturally infected horses were culture-negative after disinfection but one sample remained qPCR-positive, emphasizing the challenge of eradicating bacterial DNA under field conditions.
Disinfection of Twitches:
• All disinfection methods eliminated viable S. equi from plastic twitch handles.
• Sodium hypochlorite was the only disinfectant that completely removed S. equi DNA, making it a reliable option for minimizing cross-contamination during procedures.
Experimental vs. Field Conditions:
• Experimental contamination used high bacterial loads, likely higher than clinical scenarios.
• Field study methods were slightly less rigorous but achieved similar results, suggesting the experimental challenge represented a worst-case scenario.
• Disinfection protocols should combine manual cleaning and chemical disinfection to ensure removal of viable S. equi.
• Sodium hypochlorite is effective for DNA removal but poses environmental and safety concerns, requiring cautious use.
• Ortho-phthalaldehyde offers a viable alternative with broad-spectrum disinfection capability.
Horses vaccinated with live attenuated intranasal strangles vaccine seroconvert to SEQ2190 and SeM
The study examines seroconversion in horses vaccinated with Pinnacle® IN, a live attenuated intranasal vaccine for Streptococcus equi (strangles), using the dual antigen iELISA targeting SEQ2190 (Antigen A) and SeM (Antigen C).
Discusses implications of vaccination on serology test interpretation and utility.
High Rate of Seroconversion:
• Vaccinated horses were 14 times more likely to return a seropositive or suspect iELISA result compared to non-vaccinated horses.
At 5 weeks post-vaccination (S2):
• 76% of vaccinated horses seroconverted to Antigen C.
• 48% seroconverted to both Antigen A and C.
• If using a lower cut-off value (OD450 ≥ 0.3), 100% of vaccinated horses were either seropositive or suspect.
Antigen-Specific Seroconversion Patterns:
• Antigen C seroconversion was expected due to its immunodominance in the SeM-2 strain used in the vaccine.
• Seroconversion to Antigen A, although less common, occurred in almost half of the vaccinated horses, suggesting some cross-reactivity.
Comparison with Non-Vaccinated Horses:
• Non-vaccinated horses had minimal seroconversion at S2 (4% for Antigen C).
• A small number of non-vaccinated horses were seropositive at S1 and S2, likely due to prior exposure, but guttural pouch sampling was not performed to confirm carrier status.
Influence of Age:
• Older horses (median age 15 years) were more likely to remain seropositive at 10 weeks (S3) compared to younger horses (median age 2 years).
• Younger horses often returned to seronegative status after the initial series, indicating potential age-related differences in humoral immunity.
Comparison with Other Vaccines:
• Results differ from cell-free extract and recombinant vaccines, which do not extensively interfere with the dual iELISA.
• Pinnacle® IN appears to cause more extensive seroconversion, particularly to Antigen C.
Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers
• This study evaluates the reliability of serological testing (targeting antigens A and C) for detecting guttural pouch carriers of Streptococcus equi (S. equi), the causative agent of strangles.
• Highlights the significant limitations of serological tests in identifying chronic carriers of S. equi, emphasizing the need for microbiological sampling.
• There was no significant association between serological status and guttural pouch carriage of S. equi using either serological cut off.
• Of 287 included horses, 9 (3.1%) were found to be guttural pouch carriers.
• Only one of the nine carriers (11%) was seropositive using a cut-off of OD ≥ 0.5, and only three of nine (33%) using a cut-off of OD ≥ 0.3
• Of the 35 seropositive horses, one (2.9%) was found to have evidence of S. equi in a guttural pouch lavage and 34 (97.1%) did not.
Low Sensitivity of Serological Testing:
• The sensitivity of the antigen A/C ELISA was 11% at the higher threshold (OD ≥ 0.5) and 33% at the lower threshold (OD ≥ 0.3).
• Only 1 of 9 confirmed guttural pouch carriers was seropositive at the higher threshold, increasing to 3 carriers at the lower threshold.
• This low sensitivity indicates a high rate of false negatives, making serological testing unreliable for identifying carriers.
High Specificity and NPV:
• Specificity ranged from 77% (OD ≥ 0.3) to 88% (OD ≥ 0.5), meaning most non-carriers were correctly identified as seronegative.
• Negative predictive value (NPV) was 97%, reflecting the test’s reliability in ruling out carriers in populations with low prevalence.
Inconsistent Serological Responses in Carriers:
• Chronic guttural pouch carriage did not consistently stimulate a sustained antibody response.
• Seropositivity was not maintained in some cases of long-term carriage, suggesting immune tolerance, antigen shielding, or reduced bacterial antigenicity.
Potential Mechanisms for False Negatives:
• Antigenic shielding in chondroids or immune tolerance may reduce antigen availability for stimulating a sustained antibody response.
• Mutations or deletions in the S. equi genome might also explain the lack of antigenic stimulation in chronic carriers.
Detection of Streptococcus equi subsp. equi in guttural pouch lavage samples using a loop-mediated isothermal nucleic acid amplification microfluidic device
This study evaluates the diagnostic performance of the eqbE loop-mediated isothermal nucleic acid amplification (LAMP) assay and its microfluidic device variant for detecting S. equi in guttural pouch lavage (GPL) samples.
Aims to compare these methods with the triplex real-time quantitative PCR (qPCR) as the gold standard.
Diagnostic Sensitivity and Specificity:
• The benchtop eqbE LAMP assay demonstrated 92% sensitivity and 71% specificity compared to qPCR.
• The eqbE LAMP microfluidic device achieved 100% sensitivity and 62% specificity.
• Both LAMP methods had comparable receiver operating characteristic (ROC) area under the curve (AUC ≈ 0.81), indicating similar diagnostic performance.
Advantages:
• The LAMP microfluidic device had a lower LOD (1 colony-forming unit, CFU) than qPCR (10 CFU for SEQ2190 and 20 CFU for eqbE),
• The LAMP microfluidic device delivered results within 15–40 minutes
• The eqbE target in the triplex qPCR assay was inhibited in some cases, possibly due to primer competition, leading to variable sensitivity depending on the sample’s bacterial load.
Environmental Contamination Risks:
• The risk of contamination causing false positives was deemed minimal due to the closed system design of the LAMP microfluidic device.
Repeated nasopharyngeal lavage predicts freedom from silent carriage of Streptococcus equi after a strangles outbreak
The study evaluates the effectiveness of repeated nasopharyngeal lavage (NPL) sampling in identifying horses free of Streptococcus equi (S. equi) carriage after a strangles outbreak.
Focuses on the diagnostic utility of NPL compared to guttural pouch lavage (GPL) and the potential for NPL to predict carrier-free status in herd management.
Utility of Repeated NPL:
• Horses with at least three NPL samples testing negative for S. equi across four sampling occasions (weeks 18–30) were significantly more likely to be carrier-free at week 45.
• Ten of eleven horses with three negative NPL samples were S. equi-free at week 45, indicating strong predictive potential (P = 0.03).
Limitations of Single GPL Sampling:
• Sole reliance on GPL at week 45 would have missed 29% (4/14) of the carriers identified, as they were only positive on NPL.
• False negatives still occur: 1/24 carriers tested negative in three prior NPL samples but was positive at week 45.
• The study suggests that combining GP and NP lavage to minimise false negatives and improving overall sensitivity.
Efficacy of high-level disinfection of endoscopes contaminated with Streptococcus equi subspecies equi with 2 different disinfectants
• This study evaluates the effectiveness of accelerated hydrogen peroxide (AHP) and ortho-phthalaldehyde (OPA) in high-level disinfection of endoscopes contaminated with Streptococcus equi subsp. equi (S. equi).
• Aims to assess their ability to eliminate viable bacteria and residual DNA to prevent false-positive qPCR results.
• Both AHP and OPA successfully eliminated all viable S. equi bacteria, as confirmed by culture results (100% culture-negative across all tests).
• Despite effective bacterial elimination, residual S. equi DNA was frequently detected by qPCR:
-AHP: 33% qPCR-positive samples.
-OPA: 73% qPCR-positive samples.
-Control (water): 71% qPCR-positive samples.
• AHP demonstrated a significantly lower probability of qPCR positivity compared to OPA and control.
• Considerable variability in qPCR results was observed between testing days, with the highest rate of qPCR-positive samples on Day 5 (>90%).
-Likely contributors include environmental contamination, human error, or inconsistencies in disinfection procedures.
Mechanisms of Action:
• AHP: Works via oxidative damage to nucleic acids, proteins, and lipids. Its lower residual DNA detection suggests superior effectiveness in degrading bacterial DNA compared to OPA.
• OPA: Functions by cross-linking amino acids and increasing membrane permeability but is less effective in DNA degradation under the tested conditions.
• Currently, the disinfectants most currently used are OPA products, which require 12 minutes of contact time with the endoscope.
• Commercial hydrogen peroxide is another broad-spectrum antimicrobial, but most products containing hydrogen peroxide are highly corrosive to endoscopes.
• Accelerated hydrogen peroxide (AHP) is a newly developed product that is a blend of 2% hydrogen peroxide, surfactants, and stabilizers. This AHP product is compatible with flexible endoscopes, and only requires an 8-minute contact time
Influence of penicillin treatment of horses with strangles on seropositivity to Streptococcus equi ssp. equi-specific antibodies
This study investigates the impact of penicillin treatment during acute clinical strangles on the development and persistence of humoral immunity against S. equi antigens.
Highlights significant differences in serological responses among horses treated early, late, or not treated with penicillin during the outbreak.
• Reasons for penicillin treatment in the acute phase included decreased appetite, high or persistent fever, and lethargy, combined with owner pressure regarding horses with prolonged or worsening clinical abnormalities
Reduced Humoral Immunity in Early Treated Horses:
• Horses treated with penicillin within 11 days of fever onset (Group 1) exhibited a significantly faster decline in antibody titers against antigens A and C compared to other groups.
• By 4 months post-infection (T123), only 57% of Group 1 remained seropositive for either antigen, compared to 100% in Group 2 and 93% in Group 3.
Delayed Treatment and Untreated Groups:
• Horses treated after 16 days of fever onset (Group 2) maintained antibody titers comparable to untreated horses (Group 3). This suggests delayed antibiotic administration may allow sufficient immune activation to sustain long-term antibody production.
Seropositivity and Carrier State:
• The proportion of long-term silent carriers (identified by qPCR and culture) did not significantly differ between groups.
• Reinfection through nose-to-nose contact in shared paddocks was likely responsible for seropositivity in some horses during the final sampling.
• clinical scores were not significantly different (P = .12-1.0), but those treated after 16 days of fever had numerically higher clinical scores (Table 2) at sampling T27
Markers of long-term silent carriers of Streptococcus equi ssp. equi in horses
• The study evaluates the ability of clinical markers, inflammatory parameters, and serological assays to identify long-term silent carriers of Streptococcus equi (S. equi) after outbreaks of strangles.
• Highlights challenges in identifying silent carriers due to the absence of consistent clinical signs or systemic inflammation.
• Apart from weanlings at 6 months in outbreak A, there was no significant association between any clinical markers or serology with carrier state (P = .06-1).
• Moreover, 3/12 culture positive carriers were seronegative to S. equi.
• only endoscopic score significantly associated with carriers. Non-carriers had significantly higher clinical scores.
• The sensitivity and specificity values for serology to either antigen A or C in detection of carrier varied between outbreaks and animal groups, with sensitivity ranging from 0 to 86%, specificity 47 to 100%. In turn, likelihood ratios often approached 1, but varied between 0 and infinity
Weanlings 6 months after outbreak:
• endoscopy score was significantly higher in the carriers (chi square 11.3, P = .003).
• Seropositivity to S. equi at 6 months was significantly associated with carriers
• no significant differences by 14 months
• Guttural pouch abnormalities (e.g., empyema or chondroids) were observed in some carriers, but not all.
• A significant overlap in endoscopic scores between carriers and non-carriers suggests that guttural pouch examination alone cannot reliably identify carriers.
Carrier State and Bacterial Persistence:
• Carriers identified by qPCR but not culture likely harbor viable but non-culturable S. equi, which may still pose a transmission risk.
• Some culture-positive carriers tested seronegative, indicating that seropositivity does not necessarily persist in long-term carriers.
A long-term study of sinoscopic treatment of equine paranasal sinus disease: 155 cases (2012–2019)
The study assesses the effectiveness and limitations of sinoscopic treatment for equine paranasal sinus disorders.
Focused on long-term outcomes, intraoperative challenges, reasons for treatment failure, and postoperative complications.
Emphasizes the minimally invasive nature of sinoscopy compared to traditional sinusotomy.
Key Findings
• 96.1% (149/155) of horses showed full long-term improvement after initial or subsequent treatments.
• Sinoscopy proved effective in treating most cases of sinus disease with fewer complications compared to sinusotomy.
Failure to access the rostral maxillary sinus (RMS) and ventral conchal sinus (VCS) was attributed to:
• Osteitis-related thickening and sclerosis of the maxillary septal bulla (MSB).
• Anatomical variations, such as an enlarged infraorbital canal near the nasal concha.
• Recommendations include using narrower endoscopes or alternative portals for improved access in complex cases.
The main reasons for non-responsiveness in 30.3% of cases (47/155) included:
• Intra-sinus sequestrae (19.1% of complications).
• Inspissated exudate in sinuses (12.8%).
• Concurrent nasal disorders, including sequestrae, inspissated exudate, or fungal plaques (14.9%).
• Misdiagnosed dental sinusitis, sinonasal drainage obstruction, or progressive ethmoid hematomas (PEH).
Concurrent Nasal Lesions:
• High prevalence (38%–67%) of middle meatus lesions, such as infected nasal conchal bullae, in cases of sinusitis.
• Highlights the need for careful nasal endoscopy to detect concurrent issues affecting treatment outcomes.
• Only 2.6% (4/155) of cases required surgical fenestration to address drainage obstructions, emphasizing the efficacy of sinoscopic techniques combined with lavage and anti-inflammatory treatment.
Genipin treatment of equine palatal dysfunction: A preliminary study of safety and efficacy
Unblinded, uncontrolled and with subjective outcome= case series
This study evaluates the safety and feasibility of using genipin, a collagen cross-linker, for treating palatal dysfunction (PD) in racehorses.
Demonstrates that genipin implantation is a quick, minimally invasive procedure with minimal time off exercise, offering a potential first-line surgical option for cases unresponsive to conservative management.
The procedure was well-tolerated, with minimal adverse reactions:
• One horse had delayed return to exercise due to pyrexia and moderate palatal edema, resolving with treatment.
• Mild palatal reactions (e.g., focal swelling, edema, or superficial ulcers) occurred in six horses but resolved without major intervention.
• No complications were reported in the seven horses undergoing repeat implantation.
Efficacy in Reducing Palatal Dysfunction:
• Trainer-reported improvement in 76% of horses, comparable to other surgical interventions for PD.
• 42% of horses showed clinical resolution of PD signs and improved racing performance, while others exhibited subjective improvements in respiratory function or training response.
Improved Outcomes with Modified Implantation Technique:
• Adverse reactions were more common in the first cohort, where larger volumes of genipin (1 ml/site) were used.
• Modifications (0.5 ml/site in six implantation locations) resulted in better distribution and reduced adverse effects, suggesting operator experience and technique optimization play a crucial role.
Comparison with Other Treatments:
• Genipin implantation showed similar or superior outcomes compared to traditional procedures like laryngeal tie-forward or laser palatoplasty.
• Advantages include minimal invasiveness, rapid recovery, and no need for major surgery or foreign material placement.
Conventional imaging is useful for assessment of equine pharyngeal squamous cell carcinoma but underestimates bone involvement
The case series evaluates the utility of radiography, ultrasonography (US), and computed tomography (CT) in diagnosing pharyngeal squamous cell carcinoma (SCC) in horses.
Focuses on the effectiveness of these imaging modalities in identifying tumor extent, lymphadenopathy, and bone involvement.
Utility of Conventional Imaging:
• Radiography and ultrasonography -Both methods allow for identification of retropharyngeal and mandibular lymphadenopathy, aiding in the detection of possible metastases.
Limitations of Radiography:
• Radiography consistently underestimated the extent of bone lysis compared to CT, primarily due to tissue superimposition.
• Bone lysis associated with SCC was identified only via CT, underscoring the limitations of radiographs in assessing osseous involvement.
Advantages of CT:
• CT provided detailed visualization of aggressive bone lysis, new bone formation, and tumor spread to adjacent structures.
• It revealed bone metastases in two cases, which were undetected on radiographs
Role of Ultrasonography:
• US was effective in visualizing soft tissue masses, lymphadenopathy, and guided fine-needle aspiration biopsies.
• While bone lysis was less apparent on US compared to CT, it successfully confirmed metastatic lymphadenopathy in 5/6 cases.
Challenges in Endoscopic Examination:
• Endoscopy was inconclusive in some cases due to nasal passage obstruction or displacement of the soft palate, highlighting the importance of alternative imaging methods.
Metastatic Patterns:
• SCC metastasis to retropharyngeal lymph nodes was common, with bone metastases identified in the hyoid apparatus in one horse.
Equine sinusitis aetiology is linked to sinus microbiome by amplicon sequencing
This study explored the microbiota of equine sinusitis through next-generation sequencing (NGS), identifying distinct microbial profiles linked to primary sinusitis (PS), dental-related sinusitis (DRS), and other secondary causes (OS).
Demonstrates the advantages of molecular sequencing over traditional culture methods in understanding sinus microbiomes and guiding treatment.Distinct Microbial Profiles by Aetiology:
• DRS: Associated with higher microbial diversity, bioburden, and obligate anaerobes, including Fusobacterium, Odoribacter, Bacteroides, and Mycoplasma.
-Often linked to periodontal disease.
• PS: Characterized by low microbial diversity and dominance of a single species, most commonly Streptococcus equi.
• OS: Exhibited high genetic variation and lower bioburden, reflecting diverse causes (e.g., cysts, tumors).
Fungal Components:
• Fungi were detected in only 6% of cases, exclusively within DRS.
• Common fungal genera included Scedosporium, Fusarium, and Aspergillus, often in horses with prior antimicrobial use.
• Results suggest a greater fungal component in DRS compared to other types of sinusitis- consider antifungals?
Radiographic tracheal lumen to vertebral ratios in the normal American Miniature Horse
This study provides baseline reference data for tracheal lumen to vertebral body ratios in clinically normal American Miniature Horses.
Explores the prevalence of subclinical tracheal collapse (STC) in this population, highlighting its importance for early diagnosis and management.
Radiographic Measurements and Ratios:
• The tracheal lumen to vertebral body height (TL-VBH) and tracheal lumen to vertebral body length (TL-VBL) ratios were established as baseline references for normal American Miniature Horses.
Prevalence of Subclinical Tracheal Collapse (STC):
• 14.7% (5/34) of the horses exhibited STC, a higher prevalence than previously reported (6%).
• STC was characterized by 25–50% tracheal narrowing (grades 1–2) and did not progress to severe narrowing (grades 3–4).
Age-Related Predisposition:
• Subclinical cases were older, with an average age of 20 years compared to 7 years in the normal group, suggesting that geriatric horses are at higher risk of developing tracheal narrowing.
Dynamic and Morphological Findings:
• Radiography and fluoroscopy identified consistent patterns of tracheal narrowing, particularly at the thoracic inlet, similar to trends observed in other equine breeds and species.
• Normal respiratory fluctuations in tracheal diameter did not exceed 28%, indicating the static nature of tracheal narrowing in subclinical cases.
Histopathological Insights:
• Rare to mild loss of chondrocytes was noted histologically, without cartilage degradation or fragmentation, distinguishing subclinical cases from severe tracheal collapse seen in other species.
Computed tomography characteristics of equine paranasal sinus cysts
This study investigates the computed tomography (CT) features of paranasal sinus cysts in horses and their differentiation from other sinus diseases.
Findings focus on the unique imaging characteristics of sinus cysts and their implications for diagnosis and treatment planning.
Cyst Wall Characteristics:
• The presence of a hyperattenuating cystic wall was observed in 7 of 8 horses with sinus cysts.
• Mineralization of the cyst wall ranged from diffuse to focal and linear patterns, providing a distinct marker for diagnosis.
• Histopathology revealed the cyst walls contained a combination of ossification, hemorrhage, and fibrosis, contributing to their CT appearance.
Contrast Enhancement:
• Variable contrast enhancement of the cystic wall was observed in 3 of 7 cases that received intravenous contrast.
• This variability may be due to differences in the timing of imaging post-contrast administration or structural heterogeneity of the cyst walls.
Contents of the Cyst:
• The contents of the cyst were predominantly fluid or soft tissue with no significant difference in attenuation values compared to other sinus diseases.
• Presence of internal gas was observed in two cases, attributed to either previous surgical trephination or unknown causes.
Bone Changes:
• Cortical bone loss and cancellous bone destruction were frequent findings in both the sinus cyst group and other sinus disease groups, suggesting active bone remodeling.
• Histopathology demonstrated osteoclastic activity and inflammation, contributing to bone loss and remodelling in cystic cases.
Comparison with Other Sinus Diseases:
• Some features, such as hyperattenuating margins, were also found in other diseases like ethmoid hematomas and neoplasia, but internal mineralization patterns helped differentiate these conditions.
• Chronic primary sinusitis lacked definitive features for differentiation from sinus cysts in some cases.
Dental Associations:
• Cases of sinus cysts with dental abnormalities, such as compound odontomas and periapical infections, were identified, indicating potential odontogenic origins in some cysts.
Evaluation of the effect of laser salpingopharyngostomy on the guttural pouch environment in horses
This study evaluates how laser salpingopharyngostomy (LSP) alters the guttural pouch environment in healthy horses.
Highlights potential implications for using LSP as an adjunct treatment for guttural pouch diseases, including tympany, chondroids, chronic empyema, and mycosis.
• The guttural pouch environment was altered by the laser salpingopharyngostomy.
• Baseline recorded values within the guttural pouch were highly constant within each horse but varied between horses ? disease susceptibility.
• Post laser salpingopharyngostomy there was considerable variation within the guttural pouch between horse and during the period of sampling.
• CO2 levels post laser salpingopharyngostomy were significantly more variable than free- appeared to be linked directly to the horse’s respiratory pattern with peaks and troughs recorded
• There was a statistically significant (P < .05) increase in variance in O2 levels during sampling after the laser salpingopharyngostomy in 4 out of 6 individual horses when comparing day 0 to day 7. Comparisons of day 7 variance to day 14 variance for O2 indicated that there was a significant decline at day 14 for one horse (P < .001).
• There was no change in humidity or temperature during the study
• at 3 months, 5/6 had completely healed. The one non-healing remained similar at 12 months
• The GPs themselves were unremarkable
Immunohistochemical analysis of laryngeal muscle of horses clinically affected with recurrent laryngeal neuropathy
The study investigates the changes in muscle fiber type, size, and regenerative markers in the left cricoarytenoideus dorsalis (L-CAD) muscle of Thoroughbred horses clinically affected by recurrent laryngeal neuropathy (RLN).
Focuses on the pathological and compensatory processes occurring in the L-CAD muscle and their implications for RLN progression and treatment.
Key Findings
• Clinically affected horses showed significant atrophy in overall muscle fiber diameter, particularly in type IIA and IIX fibers.
• Expression of embryonic myosin heavy chain (MyHC) in affected horses indicates active regeneration and fiber renewal, suggesting that denervation stimulates regenerative processes.
Fiber-Type Grouping:
• Affected horses exhibited prominent fiber-type grouping, indicative of partial denervation followed by reinnervation.
• Fiber-type grouping reflects chronic or intermittent nerve damage, with surviving nerve terminals innervating adjacent denervated fibers.
Shift in Fiber Composition:
• Loss of IIX fibers, the fastest fibers in equine L-CAD, was observed in affected horses, replaced by embryonic fibers.
• While loss of IIX fibers is tolerated in subclinical cases, the reduction in fatigue-resistant type I fibers and type IIA fibers in clinically affected horses likely contributes to the inability to maintain arytenoid abduction during exercise.
Compensatory Hypertrophy:
• Some remaining muscle fibers showed hypertrophy, suggesting an adaptive response to maintain partial function. However, this was insufficient to counteract the overall loss of muscle bulk.
Potential for Regenerative Therapy:
• The presence of embryonic myosin suggests that reinnervation strategies, such as nerve grafts or stimulation therapies, may be viable before fibrosis becomes extensive.
Clinical Implications
• Pathogenesis of RLN: The loss of type IIX fibers and reduction in fatigue-resistant fibers are key pathological changes distinguishing clinically affected horses from subclinical cases.
• Functional impairment in RLN is likely due to the combined effects of fiber atrophy, loss of fast fibers, and reduced endurance capacity.
Upper airway endoscopy in exercising horses: Findings in 164 barrel racing horses with respiratory clinical signs and/or poor performance
High Prevalence of UAOs:
• Approximately 88% of the evaluated barrel racers had one or more UAOs during exercise.
• The most common UAOs were:
-Palatal instability (PI) and intermittent dorsal displacement of the soft palate (iDDSP): 62%.
-Nasopharyngeal collapse (NPC): 41%.
-Arytenoid abnormalities, including recurrent laryngeal neuropathy (RLN): 30%.
-Vocal fold collapse (VFC): 24%.
• 56% presented with two or more concurrent UAOs, indicating multifactorial airway dysfunction.
• Co-occurrences were observed between laryngeal and pharyngeal obstructions, suggesting interdependence between anatomical regions.
Exercise Intensity and UAO Timing:
• UAOs were more prevalent during low-speed/low-intensity exercise (55%) compared to high-speed/high-intensity phases (22%).
• iDDSP was notably more frequent at lower intensities, possibly due to anticipatory stress, muscle tension, or head-neck positioning.
Unique Observations in Barrel Racers:
• Barrel racing horses displayed distinct patterns of UAO compared to other equine sports.
• Active glottic closure during high-speed barrel turns was identified, suggesting adaptive mechanisms for thoracic stabilization during explosive movements.
External transcutaneous ultrasound technique in the equine cricoarytenoideus dorsalis muscle: Assessment of muscle size and echogenicity with resting endoscopy
This study validates the use of transcutaneous ultrasonography for assessing the cricoarytenoideus dorsalis (CAD) muscle as a diagnostic tool for recurrent laryngeal neuropathy (RLN) in horses.
Demonstrates that transcutaneous ultrasound is a reliable, non-invasive method that correlates well with resting endoscopic grades and physical measurements.
Key Findings
• Thickness and cross-sectional area of the left CAD (LCAD) were significantly reduced in horses with grades 3 and 4 RLN.
• Increased echogenicity of LCAD was observed in RLN-affected horses, indicating muscle atrophy.
• LCAD:RCAD Ratios:
-Ratios of thickness and cross-sectional area were significantly lower in horses with advanced RLN (grades 3.II, 3.III, and 4) compared to controls.
-Findings suggest that compensatory hypertrophy of the right CAD (RCAD) occurs to maintain partial laryngeal function in RLN.
•There was a strong correlation (R = 0.6) between physical measurements taken during laryngoplasty and ultrasound assessments, supporting the accuracy of the ultrasound technique.
• Increased echogenicity, quantified by grey-scale analysis, corresponded to RLN severity.
Advantages Over Transoesophageal Ultrasonography (TEU):
• Transcutaneous ultrasonography is less invasive, more accessible, and quicker than TEU, making it a practical choice for field diagnostics.
Nasopharyngeal bacterial and fungal microbiota in normal horses and horses with nasopharyngeal cicatrix syndrome
The study explores the differences in the nasopharyngeal bacterial and fungal microbiota between healthy horses and those affected by nasopharyngeal cicatrix syndrome (NCS).
Emphasizes the role of environmental and microbial factors in the etiology of NCS, with specific interest in fungal genera like Bipolaris.
Microbiota Composition in Healthy Horses:
• The nasopharyngeal microbiota of healthy horses was dominated by Staphylococcus, Streptococcus, Moraxella, and Corynebacteria.
• Fungal components included Aspergillus, Wallemia, Rhodotorula, Saitozyma, and Cladosporium.
Microbial Differences in NCS-Affected Horses:
• Bacterial microbiota differences:
-Decrease in Staphylococcus abundance in NCS-affected horses, likely a consequence of underlying disease processes.
-No significant overgrowth of other bacterial genera in affected horses, suggesting a limited role for bacterial dysbiosis.
• Fungal microbiota differences:
-Increased abundance of Bipolaris and Microascus in NCS-affected horses. Bipolaris is of particular interest due to its known pathogenicity in the nasal sinuses and potential as a causative agent in NCS.
Environmental Associations:
• Farms housing NCS-affected horses had significantly higher fungal genera like Bipolaris and Alternaria compared to unaffected farms.
• These findings highlight the potential role of environmental exposure in NCS development.
Role of Pythium insidiosum:
• Contrary to anecdotal beliefs, Pythium insidiosum was not detected in any horses, ruling it out as a likely etiological agent of NCS.
Race performance following epiglottic entrapment surgery in Thoroughbred yearlings
• The study evaluates the long-term race performance of Thoroughbred (TB) yearlings surgically treated for epiglottic entrapment.
• Assesses whether surgical treatment impacts racing performance compared to untreated maternal half-siblings and identifies factors influencing the likelihood of racing post-surgery.
No Significant Impact on Performance:
• Surgically treated yearlings exhibited similar racing performance metrics (career longevity, total races, earnings) compared to untreated maternal half-siblings.
• Supports the hypothesis that surgical correction of epiglottic entrapment does not adversely affect racing outcomes when other upper airway abnormalities are absent.
Influence of Concurrent Abnormalities:
• Horses with concurrent abnormal right arytenoid movement were significantly less likely to race post-surgery (OR 15.40).
Gender Representation:
• Females were overrepresented in the treated cohort (71.2%), consistent with some prior studies in mature horses but not others.
Sub-Epiglottic Cysts and Ulceration:
• Sub-epiglottic cysts were identified in 13.1% of yearlings and may predispose horses to epiglottic entrapment.
• Ulceration of entrapping tissue was less common in yearlings (54.1%) than in adult TBs, likely due to reduced dynamic airway stress in younger horses.
Epiglottic Hypoplasia:
• Found in 42.9% of treated yearlings but was not a significant predictor of racing performance post-treatment in multivariable models.
Culture-independent and dependent evaluation of the equine paranasal sinus microbiota in health and disease
The study characterizes the microbiota of the equine paranasal sinuses in healthy horses and horses with sinusitis using both culture-dependent and culture-independent methods.
Explores the bacterial and fungal organisms present and their potential roles in health and disease.
• The sinus microbiota in healthy horses primarily consists of aerobic bacteria and fungi.
• Culture-independent analysis revealed significantly greater microbial diversity compared to culture-dependent methods.
• Key bacterial phyla identified included Proteobacteria, Firmicutes, and Actinobacteria, while fungi such as Aspergillus and Malassezia were prominent.
Differences Between Health and Disease:
• Healthy sinuses lack substantial anaerobic bacterial populations, contrasting with sinusitis cases dominated by anaerobic species.
• Horses with sinusitis often displayed polymicrobial infections, with common pathogens including Streptococcus equi subsp. zooepidemicus and Fusobacterium spp.
• These findings suggest that the presence of anaerobes may indicate a shift from a commensal to a pathogenic microbiota.
Empirical Antimicrobial Therapy:
• Many horses with sinusitis receive antibiotics without prior culture and sensitivity testing, which may be less effective against polymicrobial and anaerobic infections.
• Reported antimicrobial susceptibility patterns indicate high sensitivity of anaerobic bacteria to chloramphenicol, metronidazole, and penicillin.
Unique Microbial Profiles:
• Individual horses demonstrated unique sinus microbiota compositions, likely influenced by factors such as environment, diet, and housing.
• Principal coordinate analysis highlighted the variability in microbial populations across horses.
Efficient primary surgical treatment of equine infectious sinusitis reduces postoperative aftercare and increases outcome results: a retrospective study of 130 cases
This study evaluates the outcomes of surgical treatments for primary and dental-related equine sinusitis.
Compares sinoscopic (minimally invasive) and sinusotomy (invasive) approaches while highlighting the importance of diagnostics, postoperative care, and long-term management.
High Success Rates:
• Single surgical treatment resolved clinical signs in 82.3% of cases.
• After second or third treatments, 98.5% of horses achieved long-term resolution of sinusitis symptoms.
Surgical Approaches:
• Sinoscopy was the preferred method due to lower complication rates and shorter recovery times compared to sinusotomy.
• Horses undergoing sinusotomy often had more severe or complex pathologies, necessitating a more invasive approach.
The study emphasizes a simplified postoperative care protocol:
• Daily flushing with sterile saline via a needle rather than leaving a Foley catheter in place, which reduced infection risks and stress.
• Minimal reexamination requirements compared to previous techniques, improving efficiency.
Role of Advanced Imaging:
• Computed tomography (CT) improved diagnostic accuracy and guided treatment decisions, particularly in cases where radiographs were inconclusive.
• CT imaging identified subtle pathologies such as sinonasal stenosis, dystrophic mineralization, and complex dental lesions.
Dental Pathology as a Major Cause:
• Dental issues accounted for 66.2% of cases, with apical infections, fractures, and periodontal disease being the most common etiologies.
• Advances in dental diagnostics and minimally invasive techniques have improved the management of secondary dental sinusitis.
Complications and Management:
• Short-term complications (e.g., surgical site infection, periostitis) were rare, occurring in 6.2% of cases.
• Effective hemostasis methods and the avoidance of unnecessary equipment (e.g., Foley catheters) minimized postoperative infections.
Training the equine respiratory muscles: Inspiratory muscle strength
This study investigates the effects of conventional exercise training and high-load inspiratory muscle training (IMT) on inspiratory muscle strength (IMSi) in racehorses.
Demonstrates significant improvements in IMSi with high-load IMT, offering insights into optimizing respiratory function and performance in equine athletes.
Effect of Conventional Training:
• Significant increases in IMSi were observed following 12 weeks of conventional exercise training, aligning with similar findings in human athletes.
• This suggests that regular training improves respiratory muscle function, particularly in horses conditioned for race fitness.
Impact of High-Load IMT:
• High-load IMT resulted in a further significant increase in IMSi, work, power, and inspiratory volume compared to conventional training alone.
• The improvements were not replicated in the low-load control group, confirming the specific training effect of high-load IMT on respiratory muscles.
Low-Load IMT as a Control:
• The low-load IMT group served as a sham control and showed no significant changes in IMSi or associated parameters, validating the efficacy of the high-load protocol.
Safety and Behavioural Observations:
• The application of IMT was well-tolerated by the majority of horses, with only two horses exhibiting avoidance behaviors severe enough to prevent training.
• Behavioral responses were infrequent during IMT sessions, indicating good overall compliance and feasibility for routine application.
Training the equine respiratory muscles: Ultrasonographic measurement of muscle size
This study investigates changes in respiratory and locomotor muscle sizes in Thoroughbred racehorses undergoing conventional race training and inspiratory muscle training (IMT).
Utilizes ultrasonography to measure muscle size changes and explores their implications for athletic performance and respiratory function.
Conventional Training Effects:
• Significant increases in the diaphragm size were observed after 12 weeks of conventional training
• Continued race fitness training led to reductions in diaphragm thickness, possibly due to a shift from strength-based adaptations to endurance adaptations.
Impact of High-Load IMT:
• High-load IMT either maintained or increased diaphragm thickness compared to low-load IMT or no IMT, aligning with findings in human athletes.
• This suggests hypertrophy in diaphragm fibers, potentially enhancing respiratory muscle strength and endurance.
Asymmetry in Diaphragm Measurements:
• The left diaphragm was consistently thicker than the right across all time points, which may result from anatomical or functional differences (e.g., adjacent organ pressure or locomotor-induced thoracic asymmetry).
Upper Airway Muscle Responses:
• Upper airway muscles (e.g., thyrohyoideus and cricothyroideus) increased in size during continued race fitness training, suggesting hypertrophy in response to strenuous exercise.
• IMT did not significantly alter upper airway muscle size, indicating that whole-body exercise may be more effective for developing these muscles.
Accessory and Locomotor Muscles:
• Changes in accessory respiratory muscles were variable and may reflect their secondary roles in respiration and mastication.
• Conventional training reduced asymmetry in locomotor muscles (e.g., gluteus medius), promoting balanced development.
Airway Surgery Influence:
• Horses without previous airway surgery exhibited greater gluteal muscle growth, suggesting possible links between upper airway function and locomotor muscle conditioning.
Athletic Performance Correlations:
• Preliminary analyses indicated a potential association between diaphragm thickness and race performance, though this did not reach significance in multivariable analyses.
• This finding warrants further exploration in larger populations.
Inspiratory muscle training for the treatment of dynamic upper airway collapse in racehorses: A preliminary investigation
This preliminary study explores the feasibility and potential benefits of inspiratory muscle training (IMT) in managing dynamic upper airway collapse (UAC) in racehorses.
UAC is a significant issue in equine sports, leading to poor performance and welfare concerns.
IMT aims to strengthen upper airway muscles to improve airway stability during exercise.
• IMT was well-tolerated by all horses included in the study, with no adverse effects reported.
• The protocol was successfully implemented in client-owned horses, demonstrating its practicality in a real-world setting.
Improvement in Upper Airway Function:
• Post-IMT assessments showed a reduction in the severity of dynamic airway obstructions in many cases:
• Decrease in vocal fold collapse (VFC) grades in 6 out of 9 horses.
• Palatal instability (PI) and intermittent dorsal displacement of the soft palate (iDDSP) grades improved in 7 out of 10 and 5 out of 7 horses, respectively.
• Medial deviation of the aryepiglottic folds (MDAF) grades decreased in 7 out of 9 horses.
• However, improvements were not universal, and some horses showed minimal or no changes.
Potential Mechanisms of Action:
• IMT likely activates and strengthens upper airway and respiratory muscles, contributing to improved airway stability.
• This aligns with human studies where IMT has shown benefits for vocal cord dysfunction and palatal abnormalities.
Role of Conventional Training:
• Conventional race training alone may improve upper airway muscle function, complicating the assessment of IMT’s independent effects.
• Some improvement in airway function could be attributed to ongoing exercise training.
A bitless bridle does not limit or prevent dynamic laryngeal collapse
The study evaluates whether Dr. Cook’s™ Bitless Bridle reduces the severity of dynamic laryngeal collapse (DLC) compared to a conventional snaffle bit bridle in Norwegian Swedish Coldblooded Trotters.
DLC is a common form of upper respiratory tract obstruction associated with poll flexion during exercise, negatively impacting performance.
• No significant differences in the severity of DLC were observed between the bitless and snaffle bit bridles during poll flexion.
• Changes in head and neck position, driven by rein tension, were identified as key factors in inducing DLC in susceptible horses.
• Poll flexion alters the relative positions of the larynx and hyoid apparatus, contributing to airway collapse.
• Inspiratory pressures during free head carriage were more negative with the snaffle bit bridle compared to the bitless bridle.
• During poll flexion, when DLC occurred, inspiratory pressures were similar between the two bridles, reinforcing the finding that the bit does not significantly affect DLC pathogenesis.
• Hypotheses suggesting that snaffle bits influence airway mechanics via their effects on the tongue and hyoid apparatus were not supported.
• Neither nasopharyngeal collapse nor dorsal displacement of the soft palate was observed in any horses, regardless of bridle type or rein tension.
Outcome analysis of 95 harness racehorses with confirmed dorsal displacement of the soft palate treated with laryngeal tie-forward surgery
This study evaluates the outcomes of harness racehorses undergoing laryngeal tie-forward (LTF) surgery for intermittent dorsal displacement of the soft palate (iDDSP).
Analyzes postoperative performance metrics, recurrence rates, and potential complications.
Key Findings
• Horses demonstrated significant declines in performance indices (PI) and racing speed before surgery.
• Postoperatively, 66.7% of horses improved their PI, and 65.7% showed faster racing speeds, supporting the efficacy of LTF in restoring athletic performance.
• iDDSP recurred in 21% of horses within 2 years, indicating a need for follow-up care and potentially additional interventions.
• Short-term complications occurred in 10.5% of cases, with mild seroma being the most common.
Complex Upper Respiratory Tract (URT) Disorders:
• 43% of horses had coexisting URT abnormalities at diagnosis, and 36.7% of those with postoperative URT issues were found to have multiple disorders.
• These findings suggest the dynamic and multifactorial nature of airway obstructions.
Variation in Individual Responses:
• iDDSP affected individual horses differently; 25% did not show a preoperative decline in PI, and 49% did not experience slower racing speeds before surgery.
• Some horses displaced intermittently and could self-correct during exercise, possibly mitigating performance impairments.
Tongue ties do not widen the upper airways in racehorses
This study evaluates the effects of tongue ties on upper airway dimensions and their potential role in managing dorsal displacement of the soft palate (DDSP) in Thoroughbred and Standardbred racehorses.
Findings challenge the long-standing assumption that tongue ties improve upper airway function during exercise.
Key Findings
• Contrary to expectations, tongue ties reduced the pharyngeal diameter during exercise in 93% of horses studied.
• This reduction is inconsistent with the theory that tongue ties prevent tongue retraction and subsequent narrowing of the pharynx.
• Tongue ties had minimal effects on laryngeal dimensions:
-No significant changes were observed in maximum laryngeal width or area.
-Small increases were noted in the relative aperture angle and width at two-thirds of the height, but these changes were not clinically significant.
• DDSP occurred more frequently with a tongue tie (4 cases) than without (1 case) in this small study population.
• Horses familiar with tongue ties did not show improved airway function compared to those naïve to their use.
• Previous exposure to tongue ties also did not influence pharyngeal diameter during exercise.
The impact of grade of laryngeal function immediately prior to laryngoplasty and ipsilateral ventriculocordectomy on postoperative performance: 623 Thoroughbred racehorses (1998-2013)
Investigates whether the preoperative laryngeal function grade influences postoperative outcomes in Thoroughbred racehorses undergoing laryngoplasty and ipsilateral ventriculocordectomy (LPVC).
Focuses on likelihood of postoperative racing, time to first race, racing career longevity, and earnings per start.
Preoperative Grade Influences Likelihood of Racing:
• Horses with grade III.2/III.3 laryngeal function were significantly more likely to race postoperatively compared to grade IV horses.
• Grade III.1 horses showed no significant difference in likelihood of racing compared to grade IV horses, potentially due to the smaller sample size in the grade III.1 group.
Time to First Race Post-Surgery:
• Grade III.2/III.3 horses returned to racing sooner than grade IV horses.
• The extended recovery period for grade IV horses might reflect greater severity of preoperative dysfunction or differences in training readiness.
Career Longevity and Earnings:
• Grade IV horses had greater career longevity (more postoperative races) than grade III.2/III.3 horses.
• No significant differences in postoperative earnings per start were observed between the laryngeal function grades, suggesting equivalent financial returns across grades for horses that did race.
Role of Preoperative Racing Experience:
• Horses with prior racing experience had higher postoperative earnings compared to horses that did not race before surgery.
• This might indicate that experienced horses were already better performers or had greater investment in their careers.
Postoperative Laryngeal Function:
• No evidence was found to support the theory that residual arytenoid movement (grade III) negatively impacts surgical outcomes compared to complete paralysis (grade IV).
• Arytenoid collapse during exercise, observed in grade III.3, underscores the progressive nature of recurrent laryngeal neuropathy (RLN).
Clinical Implications
• Performing LPVC on horses with grade III laryngeal function (especially III.2/III.3) appears justified, as these horses showed better postoperative outcomes compared to grade IV horses.
• Early intervention before complete arytenoid paralysis might optimize outcomes.
Clinical findings and outcome predictors for multinodular pulmonary fibrosis in horses: 46 cases (2009-2019)
This study focuses on equine multinodular pulmonary fibrosis (EMPF), an interstitial lung disease linked with equine herpesvirus-5 (EHV-5).
It evaluates clinical, diagnostic, and prognostic factors in EMPF to improve diagnostic accuracy and treatment outcomes.
- Weight loss and fever were frequent findings in EMPF but were not consistently present in all cases.
- Lymphopenia and systemic inflammation (e.g., increased fibrinogen and serum amyloid A levels) were consistent features, highlighting their utility in distinguishing EMPF from asthma.
- Histological and imaging findings revealed hallmark features of EMPF, including interstitial fibrosis and alveolar inflammation.
Role of Bronchoalveolar Lavage Fluid (BALF): - BALF analysis showed significant findings, including macrophage atypia and reduced lymphocyte-to-neutrophil ratios, which are not typical in asthma.
- Lower lymphocyte-to-neutrophil ratios were associated with poorer outcomes, making this a potential prognostic marker.
- BALF cytology highlighted differences between EMPF and asthma, such as epithelial necrosis and macrophage phagocytic activity/ atypia, which warrant further evaluation.
Poor Prognosis and Survival Rates: - EMPF was associated with high mortality, with only 24% of horses surviving beyond three months.
- Lower respiratory rates and higher blood lymphocyte counts were linked with better outcomes but were not statistically significant after multiple comparisons.
- Corticosteroids improved short-term survival but had no impact on long-term prognosis.
Role of EHV-5: - EHV-5 was frequently detected in BALF and lung tissues, but viral presence alone was not predictive of outcomes.
- The role of viral load and latency in EMPF progression remains unclear.
Therapeutic Challenges: - Antiviral treatments were inconsistently effective, possibly due to the challenges of addressing latent viral reservoirs.
- Corticosteroid therapy appeared beneficial for managing inflammation and improving short-term outcomes but could not alter disease progression.
Clinical Implications
Importance of Comprehensive Diagnostics:
* EMPF diagnosis requires a combination of clinical signs, BALF analysis, and imaging. Histopathology is definitive but not always feasible.
* Cytological markers like macrophage atypia and epithelial necrosis in BALF should prompt consideration of EMPF in differential diagnoses.
Differentiating EMPF from Asthma:
* EMPF often mimics asthma in its clinical presentation, but systemic inflammation, macrophage atypia, and neutrophilia in BALF can help distinguish it.
* Acute phase proteins like serum amyloid A could be valuable as first-line tests for distinguishing EMPF from other respiratory conditions.
Viremia and nasal shedding for the diagnosis of equine herpesvirus-1 infection in domesticated horses
Sensitivity of Nasal Shedding and Viremia Detection:
* 60 experimental and 20 observational studies met inclusion criteria.
* In experimental studies the sensitivity of qPCR matched or exceeded that seen for virus isolation from either nasal secretions or blood.
* Detection of nasal shedding typically occurred within 2 days after EHV-1 inoculation with a detection period of 3 to 7 days.
* Viremia lasted 2 to 7 days and was usually detected ≥1 days after positive identification of EHV-1 in nasal secretions.
* Nasal shedding and viremia decreased over time and remained detectable in some horses for several weeks after inoculation
Viremia Detection
Comparative Sensitivity of qPCR vs Virus Isolation:
* qPCR matched or exceeded virus isolation sensitivity in all experimental studies.
qPCR had:
* 100% sensitivity in detecting nasal shedding in several studies where virus isolation failed.
* Longer duration detection for nasal shedding (up to 21 days) compared to virus isolation (up to 9 days).
* Longer duration detection of viremia (up to 30 days) compared to virus isolation (up to 14 days).
Temporal Dynamics of Detection:
* Nasal shedding was typically detectable within 2 days post-infection, persisting for 3–7 days in most cases.
* Viremia onset followed nasal shedding and lasted for 2–7 days but could remain detectable for several weeks in some cases.
Diagnostic Methods:
* Quantitative PCR (qPCR) was more sensitive than traditional virus isolation methods for both nasal shedding and viremia.
* Virus isolation showed variable sensitivity, particularly in experimental studies using different EHV-1 strains and inoculation methods.
Factors Influencing Detection:
* Sampling frequency and timing were critical for accurate detection of EHV-1, particularly for short-lived viremia and nasal shedding.
* Variability in diagnostic outcomes was observed depending on strain virulence, infection dose, and route of inoculation.
Clinical Implications
Diagnostic Recommendations:
* Nasal swabs are preferred for detecting EHV-1, especially in clinical settings where sampling can occur early in the disease course.
* Blood samples should complement nasal swabs to enhance detection sensitivity, particularly in cases of EHM or systemic infection.
Pharmacologic interventions for the treatment of equine herpesvirus-1 in domesticated horses: A systematic review
Limited Efficacy of Pharmacological Agents:
* Most pharmacological interventions showed minimal or no significant benefits in reducing clinical signs, viremia, or nasal shedding.
* Valacyclovir and small interfering RNAs (siRNAs) were among the better-studied agents but had limited success in clinical or virological outcomes.
Variability in Outcomes Across Studies:
* Variability in drug efficacy was influenced by factors like dosing schedules, timing relative to infection, and study designs.
* Neurological signs (equine herpesvirus myeloencephalopathy, EHM) and abortion rates were rarely mitigated by the treatments studied.
Challenges with Study Quality:
* Moderate to high risk of bias was identified in most studies due to small sample sizes, inconsistent reporting, and lack of blinding.
* Many studies lacked standardization in methodologies, including viral challenge models and outcome measures.
Specific Findings by Drug Class:
* Antivirals (e.g., Valacyclovir): Reduced viremia levels in some studies but showed no consistent effect on clinical signs or nasal shedding.
* siRNAs: Showed potential for reducing specific neurological outcomes in isolated studies but lacked reproducibility across trials.
* Parapoxvirus ovis-based Immunomodulators: Minimal impact on clinical or virological outcomes.
* Other Agents (e.g., Interferons, Herbal Products, Heparin): Failed to demonstrate significant benefits in reducing EHV-1-related clinical signs or infection rates.
- Valacyclovir and related antivirals may offer some benefits in reducing viremia, particularly when administered prophylactically or early post-infection.
-Their high cost and limited efficacy necessitate careful consideration of their use in clinical practice. - Future trials must standardize protocols, include larger sample sizes, and employ blinded, randomized designs to enhance reliability.
- Long-term studies are needed to evaluate the potential of therapies in preventing latent infection and reactivation.
