Evaluation of sperm morphology is an important part of stallion breeding soundness evaluation. The objectives of this review are to discuss the pathogenesis of sperm defects and describe some of the sperm abnormalities present in the ejaculate of stallions.
Currently, there are a variety of wound dressings available ranging from passive adherent/nonadherent to interactive and bioactive products that contribute to the healing process. Many of the newer dressings are designed to create a moist wound healing environment which allows the wound fluids and growth factors to remain in contact with wound, thus promoting autolytic debridement and accelerating wound healing. Even with substantial advancements in wound dressings it appears that no single material can produce the optimum microenvironment for all wounds or for all the stages of the wound healing process. The intent of this report is to provide a review of currently available dressings, their physical characteristics and to describe their best use as it relates to the condition of the wound (clean, contaminated or infected) and the phases of wound healing.
The equine sarcoid, a fibroblastic tumor, is the most prevalent equine skin tumor and can affect all equidae. The sarcoid should be regarded as a tumor of fibroblasts. Involvement of the epidermis is a feature of most types but is not an obligatory feature. There are six visually recognizable types that correlate closely with the histology. The occult (superficial) type features alopecia, scaling, and skin thickening. The verrucose type has a prominent warty or verrucous appearance. There are two subtypes of the nodular form. Type A nodules are usually isolated individual or lobulated congregations of spherical subcutaneous masses. Type B nodules have cutaneous involvement that precludes independent movement of the overlying skin. Fibroblastic sarcoids have a fleshy fibrovascular appearance, often closely resembling granulation tissue. Type 1 fibroblastic sarcoids are pedunculated, whereas type 2 have a broad locally invasive base. The malignant sarcoid is an aggressive locally invasive form that extends widely into adjacent skin and subcutis. Mixed forms are common, and it is probably true that the large majority of sarcoid lesions have mixed components of two or more types.
Magnetic resonance imaging has revolutionized the diagnosis of foot-related pain, defining many soft tissue injuries that had previously been poorly recognized and greatly enhancing our understanding of pathological abnormalities of the navicular bone. The concept of multiple injuries contributing to lameness has been recognized. It has become clear that lesions may predate the onset of lameness. A better understanding of pain causing lameness is required.
Osteochondrosis (OC) can be defined as a disturbance of the process of endochondral ossification of the articular-epiphyseal complex. The ensuing irregularities of the ossification front lead to thick cartilage plugs, the deeper parts of which may become necrotic because nutrition by diffusion becomes insufficient. In the final stage osteochondral fragments may detach and become loose or semiloose intraarticular bodies or joint mice. In this stage, the term osteochondritis dissecans is used. Osteochondrosis has a high incidence (on average 25%) in most Warmblood breeds and in the racing breeds. Performance is not always affected, but losses to the equine industry are huge, both directly and indirectly through loss of breeding potential and depreciation of market value of affected animals. Osteochondrosis is a multifactorial disease in which genetic influences (accounting for about 25% of the phenotype), nutritional factors, biomechanical influences, and conformation play a role. The disease is very dynamic during the first months of life when lesions may appear and regress spontaneously, indicating that OC has a dualistic character in which the final clinical outcome is determined by the etiologic factors mentioned above and a repair process incited by the lesions. With increasing age, the remodeling rate of the extracellular matrix of the cartilage decreases and after a certain age no substantial change in the radiographic appearance of lesions is seen anymore. In general, no major change can be expected after 1 year of age. For this reason it is advised not to apply the treatment of choice, which is arthroscopic surgery, before this age. Diagnosis of OC has always been based on clinical and radiographic findings, but more advanced imaging techniques, such as magnetic resonance imaging, and the use of biomarkers may play a more important role in the future. Biomarkers may also be used for prevention to identify animals that are at risk for the development of OC. For these animals, environmental conditions may then be manipulated to maximally reduce the risk of OC. Genetic markers may become a tool too, but the complex character of OC and the relatively big influence of environmental factors make a real breakthrough in this area improbable.
The following article aims at giving an overview on currently available balanced anesthetic regimens for horses. In horses, maintenance of cardiovascular function and thus muscular perfusion during anesthesia is essential. Also, a smooth recovery phase which should be completed within at least 1 hour of termination of drug administration is crucial. All inhalation anesthetics depress cardiovascular function dose dependently. Thus, drugs that decrease the need for inhalation anesthetics (decrease MAC) might improve cardiovascular function during anesthesia. Lidocaine constant rate infusion (CRI), at clinically used dose rates, decreases MAC by about 25%, and no untoward cardiovascular side effects have been reported. In horses anesthetized for several hours, careful dosing is advised. Toxicity due to accumulation, masked during anesthesia, might become apparent during recovery. Ketamine is the only drug used for balanced anesthesia that might positively influence cardiovascular function. But following continuous ketamine administration for longer time periods (>2 hours), rough recoveries can occur. Preliminary results with S-ketamine CRIs showed better results in this respect, but further studies are warranted. Medetomidine CRI does decrease MAC about 30% at recommended dose rates. Cardiovascular function in comparison to lidocaine balance is moderately impaired, but horses show less intraoperative awakening following surgical stimulation. Recovery phase following medetomidine balance is clearly smoother than with any other regimen. In conclusion, lidocaine, ketamine, and medetomidine are mainly used for balanced anesthesia in horses. In cardiovascularly compromised patients, ketamine might be advantageous. If a smooth recovery phase is crucial, medetomidine should be the drug of choice.
CT of the equine head is an established imaging technique. It is used routinely in the academic setting and, as CT scanners have become more affordable, is being used more often in private practice. CT is considered more effective than survey radiography in depicting the complex anatomy of the nasal cavity and calvarium, as it eliminates superimposition of overlying structures such as the bones forming the brain case and nasal cavity. The normal CT appearance of the head and nasal cavity as well as the CT features of common diseases affecting the brain, dental arcades, and sinuses are well described in the literature. The examination requires general anesthesia and hence takes longer than survey radiographs. As with any other imaging modality, it is most effective when is performed to answer specific questions generated by the clinical examination. Though costs of facilities and CT equipment are higher than survey radiography, the benefit derived from the accurate assessment of a given pathological process of the head makes this modality an effective addition to the equine practice. This chapter reviews the technical considerations associated with the procedure. It also provides an anatomical atlas of the area as well as a discussion of common diseases to highlight the advantages and disadvantages of the technique. A complete list of references is also included for the reader who wants to obtain a deeper understanding of the technique and its capabilities.
Tendon and ligament injuries are common in athletic horses and can be difficult to treat successfully. Tendons and ligaments are characterized by sparse fibroblasts embedded in a complex structural hierarchy of collagen-rich extracellular matrix (ECM) organized along lines of tension. This precise organizational scheme imparts the necessary mechanical properties for tendons and ligaments to function under high loads. The etiology of tendon and ligament injuries remains the subject of numerous ongoing research projects; however, acute overloading and accumulated microtrauma are the two predominant theories. Under normal physiologic loading, a balance is maintained between the degeneration of ECM and its repair by the resident fibroblast population. When damage occurs faster than it can be repaired, clinical signs of tendonitis or desmitis develop. The molecular and cellular responses that occur during tendon and ligament healing are important to understand, as they provide key points of control that may be targeted for new therapies.
Vascular disorders play an important role in male infertility. Various modalities of ultrasound examination can be applied to evaluate testicular vasculature and to objectively measure numerous parameters of testicular perfusion. This paper describes techniques of ultrasound examination of testicular vasculature in the stallion, using gray-scale, color, and power Doppler ultrasound. Results of studies on the normal vascular anatomy in the stallion and its variations, the methods of obtaining most optimal measures of testicular perfusion, and the effects of the physiological and pharmacological factors on testicular blood flow are reviewed. There is a growing body of evidence that evaluation of testicular vasculature has a tremendous clinical relevance and should be included in the diagnostic workup of scrotal diseases.
Magnetic resonance (MR) imaging is the gold-standard imaging modality for diagnosing tendon and ligament pathology. MR is capable of detecting lesions that are not visible with other imaging modalities. Pathologic changes in tendons and ligaments are seen on MR as changes in size, shape, and/or signal intensity of the affected structure. All tendons and ligaments have individual characteristics and variations in normal appearance. This chapter describes the normal MR appearance of the tendons and ligaments of the distal limb, as well as discussing the ways in which damage to individual tendons and ligaments affects how they appear on MR images.
Cell-based therapies encompass a growing list of treatment modalities with promising potential for treating tendon and ligament injuries in the horse. To some degree, the availability of these therapies to the equine practitioner has outpaced needed experimental and clinical data necessary to establish efficacy and safety. Client awareness and demands place additional pressure on the equine practitioner to provide education and services including these therapies. Minimally manipulated autologous cell therapies may provide a safer alternative or intermediate to cultured or expanded stem cells until more is learned regarding the in vivo activity of the cells and culture media.
Septic arthritis and osteomyelitis is a serious complication of septicemia in foals. Within a given joint, the disease can involve the synovial membrane, the epiphysis, the physis, the metaphysis, and/or the small cuboidal bones of the tarsus or carpus. Early identification and early institution of an aggressive therapeutic protocol can result in a successful outcome. Concurrent systemic illness, type of septic arthritis, multiple joint involvement, pathogenicity of the organism, presence of osteomyelitis, and expected use of the foal are factors that can help formulate a prognosis.
Testicular degeneration is a common cause of subfertility and infertility in stallions. The disease can broadly be divided into two categories: those cases resulting from a known testicular insult, and idiopathic (senile or age-related) testicular degeneration. This manuscript describes the problem of testicular degeneration in the equine breeding industry and summarizes what is known about the pathophysiology of the disease. Additionally, the clinical signs of testicular degeneration are reviewed so that the clinician can more quickly and accurately arrive at a diagnosis. Differences in the approach to treatment of testicular degeneration arising from a known cause and idiopathic testicular degeneration are discussed as are differences in prognoses. Finally, the practitioner is provided with practical information on how to more effectively manage affected stallions and what, if anything, can be done to improve reproductive performance of these animals both in the field and in a referral setting.
Magnetic resonance (MR) imaging provides a new imaging modality to evaluate the osseous and soft tissue structures in the equine limb. The metacarpal and metatarsal region, specifically the proximal aspect, has proven to be a difficult area to assess with radiography and ultrasonography due to the multiple vascular, soft tissue, and osseous structures in this area. MR evaluation of this region enables diagnosis of lesions within the suspensory ligament, the superficial and deep digital flexor (DDFT) tendons, the accessory ligament of the DDFT, the extensor tendons, as well as inflammatory changes associated with the bones of the metacarpal and metatarsal regions. This chapter provides information regarding MR imaging of this region and examples of pathologic change identified using this imaging modality.
Temporohyoid osteoarthropathy and accompanying fractures of these bones is a common cause of unilateral facial paralysis and/or vestibular disease in adult horses. Approximately 50% of horses recover following medical treatment with antibiotics and antiinflammatory drugs. A ceratohyoidectomy is recommended to prevent additional fractures and recurrence of clinical signs. Exposure keratitis and keratoconjunctivitis sicca are frequent complications to facial nerve paralysis, and partial tarsorrhaphy is helpful in preventing these complications.
Indications for magnetic resonance imaging (MRI) of the fetlock region are discussed. Normal anatomy is described by reference to figures illustrating sagittal, transverse, and dorsal plane scans using T1-weighted spoiled gradient echo, T2* gradient echo, and short tau inversion recovery (STIR) sequences. Examples of the more common abnormalities identified using MRI are provided.
Equine herpesvirus (EHV)-1 and -4 associated respiratory disease in the horse occurs worldwide. Clinically there are no distinguishing characteristics between EHV-1 and EHV-4 infection. Disease is spread between animals by aerosolized virus, direct contact with infected respiratory secretions, or fomites. Diagnosis can be made by virus isolation, PCR of nasopharyngeal secretions or peripheral blood mononuclear cells, or serology. The characteristics of the protective immune response against EHV-1/4 infection have not been well described, but it is likely a combination of humoral and cell-mediated immunity. Current vaccines stimulate primarily a humoral immune response, which may decrease the severity of clinical signs, viremia, and viral shedding, but does not provide protection from infection. Since suckling foals have recently been shown to be an important reservoir in the transmission of EHV-1 and EHV-4, they ought to be the target for immunoprophylaxis to eliminate or significantly reduce EHV infections in the field and prevent the establishment of a latent state. Until more effective vaccine strategies are developed, appropriate herd management is essential to preventing or containing outbreaks of EHV-1/4.
Of the two flexor tendons in horses’ lower limbs, the superficial digital flexor tendon is more commonly injured than the deep digital flexor tendon. Flexor tendon injuries are caused by either overstrain of the tendon or direct trauma. Overstrain injuries have a typical swelling of the tendon that requires ultrasonographic evaluation to confirm the diagnosis. Treatment of these injuries includes anti-inflammatory therapy initially followed by a rehabilitation program. New therapies are emerging for modulating healing of these injuries. Flexor tendon lacerations are usually the result of direct penetrating trauma to the limb. Management of these injuries includes surgical management combined with appropriate coaptation. Involvement of a tendon sheath complicates management with the potential formation of septic tenosynovitis. The prognosis for returning successfully to athletic function in the case of overstrain injuries is fair, but re-injury is common, and for tendon lacerations, it is guarded to poor.
Equine botulism is clinically defined as a gradually progressive myasthenia characterized initially by mild dysphagia, decreased tongue muscle tone and strength, mild mydriasis, and decreased tail tone leading to recumbency. The rate of progression of clinical signs of botulism is toxin dose-dependent. Ingestion of massive amounts of toxin may lead to recumbency and death within 24 hours, whereas very modest doses of toxin may not result in clinical signs until 10 to 15 days following ingestion. Typical field cases show evidence of dysphagia and weakness over 2 to 3 days and become recumbent on day 3 or 4 following initial detection of clinical signs. Definitive diagnosis is often impossible in single cases. Treatment should include botulinum antitoxin, complete stall rest, and supportive therapy with oral fluids and nutrition. Prognosis for recovery is excellent, if the horse is standing when treated with antitoxin. Vaccination with type B botulinum toxoid provides excellent protection.