Equine Viral Respiratory Pathogen Surveillance at Horse Shows and Sales

Equine respiratory viral infections cause significant worldwide disease and economic loss. Common causes include equine influenza virus (EIV) and equine herpesviruses-1 and -4 (EHV-1 and -4), and risk of exposure to these agents may be highest in young horses commingling at sales and competitive events. A surveillance study was conducted at two horse shows and two Thoroughbred sales to determine whether horses shed EHV-1, EHV-4, or EIV on arrival, or 2-4 days later, and whether shedding was associated with identifiable risk factors. Real-time polymerase chain reaction assays were used to detect EHV-1, EHV-4, and EIV nucleic acid in nasal swabs obtained from 369 horses at the four events. In response to evidence of clinical disease, 82 additional horses were sampled at two farms providing horses for one of the sales. On arrival at the events, shedding of EHV-1 was detected in 3.3%, EHV-4 in 1.1%, and EIV in 0.8% of horses. EHV-1 was detected at low levels, and EHV-1 and EHV-4 detection was not associated with clinical disease. EIV was detected only in horses at a Thoroughbred sale, in association with an outbreak of respiratory disease traced back to regional farms. On arrival at events, horses younger than 2 years had a significantly greater risk of shedding EHV-1 compared with older horses; no other significant risk factors associated with viral shedding were identified. Thus, there is a risk of exposure to EIV, EHV-1, and EHV-4 at equine events, and horses and events should be managed to mitigate this risk.     

Magnetic Resonance Assessment of the Equine Distal Phalanx Facies Flexoria

Abnormalities of the facies flexoria of the distal phalanx (FF) of the horse associated with podotrochlear syndrome have been scarcely described in the literature. The objective of this retrospective study was to determine correlation between modification of the FF and lesions of the podotrochlear apparatus. This study includes 100 horses referred for forelimb lameness that underwent a standardized magnetic resonance (MR) imaging protocol of the affected foot. Of the 100 MR studies, 74 had podotrochlear lesions and 26 free of podotrochlear lesions served as controls. A comparison of the FF compact bone thickness between affected and control feet was performed. Presence and location of a deep digital flexor tendon (DDFT) lesion was noted. Grading systems were used to score: FF osseous resorption, FF bone marrow lesion, FF sclerosis and abnormalities of the navicular bursa and the distal interphalangeal joint. Compact bone thickness of the FF was not increased in case of tendinopathy of the DDFT or other podotrochlear lesions (P = .86). Significant correlation was observed between osseous resorption of the FF at the level of the distal recess of the navicular bursa and synovial proliferation of the navicular bursa (P = .05). Compact bone thickening at the DDFT enthesis is not predictive of podotrochlear syndrome and should rather be considered as an interindividual anatomical variation. Navicular bursitis may play a role in osseous resorption of the FF.     

Factors Influencing Equine Gut Microbiota: Current Knowledge

Gastrointestinal microbiota play a crucial role in nutrient digestion, maintaining animal health and welfare. Various factors may affect microbial balance often leading to disturbances that may result in debilitating conditions such as colic and laminitis. The invention of next-generation sequencing technologies and bioinformatics has provided valuable information on the effects of factors influencing equine gut microbiota. Among those factors are nutrition and management (e.g., diet, supplements, exercise), medical substances (e.g., antimicrobials, anthelmintics, anesthetics), animal-related factors (breed and age), various pathological conditions (colitis, diarrhea, colic, laminitis, equine gastric ulcer syndrome), as well as stress-related factors (transportation and weaning). The aim of this review is to assimilate current knowledge on equine microbiome studies, focusing on the effect of factors influencing equine gastrointestinal microbiota. Decrease in microbial diversity and richness leading to decrease in stability; decrease in Lachnospiraceae and Ruminococcaceae family members, which contribute to gut homeostasis; increase in Lactobacillus and Streptococcus; decrease in lactic acid utilizing bacteria; decrease in butyrate-producing bacteria that have anti-inflammatory properties may all be considered as a negative change in equine gut microbiota. Shifts in Firmicutes and Bacteroidetes have often been observed in the literature in response to certain treatments or when describing healthy and unhealthy animals; however, these shifts are inconsistent. It is time to move forward and use the knowledge now acquired to start manipulating the microbiota of horses.     

Historical Aspects of Equine Embryo Transfer

Early embryo transfer in equids was undertaken simultaneously in the early 1970s in Cambridge, England, and Kyoto, Japan. Both groups achieved limited success when flushing the uterine horn ipsilateral to the side of ovulation but the rates improved markedly when the whole uterus was flushed on realization of the continued movement of the embryo throughout the uterine lumen after day 6. Initial transfers of embryos to recipient mares were carried out surgically, but nonsurgical transfer via the cervix has been used subsequently with increasing success, culminating in pregnancy rates of 75%–90% today. Experimental use of embryo transfer in horses and donkeys demonstrated the unique ability of equids to carry to term a full range of interspecies hybrid conceptuses and extraspecies pregnancies created by embryo transfer. Furthermore, splitting of day 4–8 cell embryos and day 6 compact morulae allowed the creation of genetically identical twin foals. But despite these and other significant advances over the past 45 years, a persisting limitation is the relatively low embryo recovery rates from donor mares treated with exogenous gonadotropins in attempts to induce them to superovulate. This is due to the toughness of the ovarian tunica albuginea which forces ovulation through the ventrally situated ovulation fossa where multiple follicles compete with each other and luteinize before they can ovulate properly.