Effects of genetic and environmental factors on chronic lower airway disease in horses

Background : Environment and genetics influence the manifestation of recurrent airway obstruction (RAO), but the associations of specific factors with mild, moderate, and severe clinical signs are unknown.
Hypothesis : We hypothesized that sire, feed, bedding, time outdoors, sex, and age are associated with clinical manifestations of mild, moderate, and severe lower airway disease.
Animals : Direct offspring of 2 RAO-affected Warmblood stallions (F1S1, n = 172; F1S2, n = 135); maternal half-siblings of F1S1 (mHSS1, n = 66); and an age-matched, randomly chosen control group (CG, n = 33).
Methods : A standardized questionnaire was used to assess potential risk factors and to establish a horse owner assessed respiratory signs index (HOARSI 1–4, from healthy to severe) according to clinical signs of lower airway disease.
Results : More F1S1 and F1S2 horses showed moderate to severe clinical signs (HOARSI 3 and HOARSI 4 combined, 29.6 and 27.3%, respectively) compared with CG and mHSS1 horses (9.1 and 6.2%, respectively; contingency table overall test, P < .001). Sire, hay feeding, and age (in decreasing order of strength) were associated with more severe clinical signs (higher HOARSI), more frequent coughing, and nasal discharge.
Conclusions and Clinical Relevance : There is a genetic predisposition and lesser but also marked effects of hay feeding and age on the manifestation of moderate to severe clinical signs, most markedly on coughing frequency. In contrast, mild clinical signs were not associated with sire or hay feeding in our populations.     

The myocardial thickness in budgerigars (Melopsittacus undulatus) and Australian king parrots (Alisterus s. scapularis)

Due to lack of reference values an objective assessment of myocardial dilatation and hypertrophy in cage and aviary birds so far is not possible. Therefore the thickness of the myocardium of the left and the right ventricle of the heart of 14 budgerigars (Melopsittacus undulatus) and 5 Alisterus parrots (Alisterus s. scapularis) of both sexes was examined according to a standard protocol to establish morphometric data and first reference values. In order to compare the results of birds of different sizes all data were set in relation to the size of the bird's body (length of the sternum). Results of different zones were compared by means of statistical methods within one species. Besides that a comparison between the two species was performed. Only minor significant differences could be noticed.     

The Variability and Repeatability of Indices Derived from the Single-breath Diagram for CO2 in Horses with Chronic Obstructive Pulmonary Disease and the Effect of Lobelin Hydrochloride on These Indices

Several indices of ventilatory heterogeneity can be identified from the volumetric capnogram and its graphic presentation, the single-breath diagram for CO₂ (SBD-CO₂). Physiologically based indices of pulmonary function (VTE, VCO₂, F _ACO₂, VD_Bohr, VD_Bohr%, VD/VTE, A ₁/A ₂) were calculated for healthy horses (group I, n = 5) and for horses with subclinical (group II, n = 7) or clinically manifest chronic obstructive pulmonary disease (COPD) (group III, n = 8) during tidal breathing and after medication with lobelin hydrochloride (Lobelin). We investigated the variability and repeatability of the lung function indices in healthy horses and in those with COPD both during tidal breathing and after administration of Lobelin, a centrally acting respiratory stimulant. In particular, we were interested in whether the discriminating ability of SBD-CO₂-derived lung function indices would be increased between different patient groups after administration of Lobelin compared to those for the resting values. Of the indices studied, VTE, F _ACO₂, VD_Bohr% and A ₁/A ₂ appeared to be those with good to excellent repeatability in discriminating healthy horses from those with COPD. Stimulating respiration with Lobelin gave no advantage in the repeatability of the lung function indices or in differentiating between horses with different degrees of COPD.     

Antigenic and genetic variations in European and North American equine influenza virus strains (H3N8) isolated from 2006 to 2007

Equine influenza virus (EIV) surveillance is important in the management of equine influenza. It provides data on circulating and newly emerging strains for vaccine strain selection. To this end, antigenic characterisation by haemaggluttination inhibition (HI) assay and phylogenetic analysis was carried out on 28 EIV strains isolated in North America and Europe during 2006 and 2007. In the UK, 20 viruses were isolated from 28 nasopharyngeal swabs that tested positive by enzyme-linked immunosorbent assay. All except two of the UK viruses were characterised as members of the Florida sublineage with similarity to A/eq/Newmarket/5/03 (clade 2). One isolate, A/eq/Cheshire/1/06, was characterised as an American lineage strain similar to viruses isolated up to 10 years earlier. A second isolate, A/eq/Lincolnshire/1/07 was characterised as a member of the Florida sublineage (clade 1) with similarity to A/eq/Wisconsin/03. Furthermore, A/eq/Lincolnshire/1/06 was a member of the Florida sublineage (clade 2) by haemagglutinin (HA) gene sequence, but appeared to be a member of the Eurasian lineage by the non-structural gene (NS) sequence suggesting that reassortment had occurred. A/eq/Switzerland/P112/07 was characterised as a member of the Eurasian lineage, the first time since 2005 that isolation of a virus from this lineage has been reported. Seven viruses from North America were classified as members of the Florida sublineage (clade 1), similar to A/eq/Wisconsin/03. In conclusion, a variety of antigenically distinct EIVs continue to circulate worldwide. Florida sublineage clade 1 viruses appear to predominate in North America, clade 2 viruses in Europe.     

Hereditary diseases in the horse: II. Polygenetic or multifactorial diseases

Many of the important diseases of sport and pleasure horses are thought to have a genetic component. The majority of these diseases, however, are multifactorial and are influenced not only by genetics, but also by environmental factors. In this review some of the most important multifactorial diseases are described and the current evidence for a genetic background is discussed.     

Antibodies to Aqx toxin of Actinobacillus equuli in horses and foals

Actinobacillus equuli is found in the normal oral flora of horses, but has been associated with several diseases, and particularly with the usually fatal septicaemia in neonatal foals which is thought to be associated with a failure of the passive transfer of immunoglobulins via the colostrum. The Aqx protein of A equuli, belonging to the RTX family of pore-forming toxins, is also cytotoxic to horse lymphocytes. The presence of antibodies to Aqx was investigated in sera from individual horses from different regions; the sera from adult horses and foals 24 hours after birth reacted with Aqx, and sera from foals sampled shortly after an intake of colostrum also reacted with Aqx, but sera from foals taken before an intake of colostrum did not react with Aqx.     

Treatment of clinically diagnosed equine sarcoid with a mistletoe extract (Viscum album austriacus)

Background: Equine sarcoids (ES) are common, difficult to treat, and have high recurrence rates. Viscum album extracts (VAE) are used in human cancer treatment. Hypothesis: That therapy with VAE (Iscador P) is effective in the treatment of ES. Animals: Fifty‐three horses (444 ES); 42 were treated with VAE or placebo as monotherapy; 11 were treated with VAE or placebo after selective excision of ES. Methods: Prospective, randomised, blinded, clinical trial. Horses were randomly assigned to treatment (VAE; n = 32) or control group (Placebo; n = 21). One milliliter of VAE (Iscador P) in increasing concentrations from 0.1 to 20 mg/mL or physiological NaCl solution was given SC 3 times a week over 105 days. Number, localization, and type of the ES were documented over 12 months. A subset of 163 clinically diagnosed equine sarcoid (CDES) lesions (95 VAE, 68 Placebo) was evaluated in detail, considering clinical findings and tumor volume. Results: No undesired adverse effects were observed except for mild edema at the injection site in 5 of 32 horses (16%). Complete or partial regression was observed in 13 horses of the VAE group (41%) and in 3 of the control horses (14%; P < .05). After VAE treatment, 48 of 95 CDES (67%) showed an improvement compared with 17 of 68 CDES in the control group (40%; P < .01). Twenty‐seven CDES had disappeared completely in the VAE group (38%) compared with 9 CDES in the control group (13% NS). Conclusions and Clinical Importance: VAE (Iscador P) represents a safe and effective treatment for CDES.