Sequential Plasma Lactate Concentrations as Prognostic Indicators in Adult Equine Emergencies

Background: Sequential lactate concentration ([LAC]) measurements have prognostic value in that hospitalized humans and neonatal foals that have a delayed return to normolactatemia have greater morbidity and case fatality rate.
Hypothesis: Prognosis for survival is decreased in horses with a delayed return to normal [LAC].
Animals: Two hundred and fifty adult horses presented for emergency evaluation excepting horses evaluated because of only ophthalmologic conditions, superficial wounds, and septic synovitis without systemic involvement.
Methods: Prospective observational study. [LAC] was measured at admission and then at 6, 12, 24, 48, and 72 hours after admission. The change in [LAC] over time ([LAC]Δ T ) was calculated from changes in [LAC] between sampling points.
Results: Median [LAC] was significantly ( P < .001) higher at admission in nonsurvivors (4.10 mmol/L [range, 0.60–18.20 mmol/L]) when compared with survivors (1.30 mmol/L [range, 0.30–13.90 mmol/L]) and this difference remained at all subsequent time points. The odds ratio for nonsurvival increased from 1.29 (95% confidence interval 1.17–1.43) at admission to 49.90 (6.47–384) at 72 hours after admission for every 1 mmol/L increase in [LAC]. [LAC]Δ T was initially positive in all horses but became negative and significantly lower in nonsurvivors for the time periods between 24–72 hours (− 0.47, P = .001) and 48–72 hours (− 0.07, P = .032) when compared with survivors (0.00 at both time periods) consistent with lactate accumulation in nonsurvivors.
Conclusions and Clinical Importance: These results indicate that lactate metabolism is impaired in critically ill horses and [LAC]Δ T can be a useful prognostic indicator in horses.     

Equine Piroplasmosis

Equine piroplasmosis (EP) is a tick-borne protozoal disease of horses, mules, donkeys, and zebras that is characterized by acute hemolytic anemia. The etiologic agents are two hemoprotozoan parasites, Theileria equi (Laveran, 1901) and Babesia caballi (Nutall and Strickland, 1910) that are transmitted primarily by ixodid ticks. Equine piroplasmosis is found globally where tick vectors are present and is endemic in tropical, subtropical, and some temperate regions. Horses infected with B. equi remain seropositive for life; horses infected with B. caballi are seropositive for several years to life. Economic losses associated with EP are significant and include the cost of treatment, especially in acutely infected horses; abortions; loss of performance; death; and restrictions in meeting international requirements related to exportation or participation in equestrian sporting events. Equine babesiosis–free countries limit the entrance of Babesia-seropositive horses into their countries. In the United States a few sporadic outbreaks have occurred in recent years but have been limited due to implementation of stringent control methods. The cELISA for both T. equi and B. caballi is currently the recommended test for international horse transport. Different therapies for control and sterilization of the parasites are discussed.     

Equine rhabdomyolysis

A 1.5-year-old Quarter Horse gelding with a history of chronic nasal discharge and leukocytosis presented with signs of increased lethargy and muscular pain. The horse quickly became recumbent and unable to rise and was euthanized due to a poor prognosis. At necropsy, severe bilateral guttural pouch empyema was observed, as well as numerous well-demarcated areas of pallor within the skeletal muscles of all major muscle groups. Polymerase chain reaction testing of the guttural pouch exudate confirmed an infection with Streptococcus equi subsp. equi, and an S. equi-associated immune-mediated rhabdomyolysis was initially considered to be the most likely diagnosis. This report briefly discusses the various etiologies that should be considered in cases of equine myopathy, and it demonstrates the complexity of these poorly understood muscular disorders.     

Equine haemothorax

Haemothorax is an uncommon, although clinically important, condition in horses of all ages and has a wide range of aetiologies. Clinical signs can include tachypnoea, dyspnoea, tachycardia, absence of bronchovesicular sounds, haemoptysis, colic and death. The most common aetiologies are associated with trauma, neoplasia, coagulation disorders, iatrogenic causes and vessel rupture. Diagnosis is made if there is evidence of thoracic fluid on ultrasonography and confirmation of haemorrhage by thoracocentesis. The goals of treatment are to address the primary cause and provide supportive care. Prognosis depends on aetiology, severity of active bleeding and volume of blood loss.     

Equine lymphoma

Lymphoma, although rare, is the most common haematopoietic neoplasm encountered in horses and can occur at any age, with horses 4–10 years more commonly affected. Lymphoma can be classified into multicentric, alimentary, mediastinal, cutaneous and solitary. Clinical signs are typically nonspecific until the disease has progressed to end‐stage at which time clinical signs reflect function of organ(s) involved. Horses with the cutaneous form of lymphoma typically present with multifocal skin lesions and no other clinical signs. Like the nonspecific clinical signs of lymphoma, results of complete blood count (CBC) and serum biochemistries are not often helpful with diagnosis, but lymphoma should be considered if anaemia, hyperfibrinogenaemia, hyperproteinaemia and hypoalbuminaemia are observed without a clear indication of infectious disease. Identification of neoplastic lymphocytes during cytological examination of a body cavity effusion can confirm the presence of lymphoma. Typically, ante mortem confirmation of lymphoma is made through histopathological examination of a biopsy or cytological examination of a fine needle aspirate of a suspected lesion. Observation of compression or destruction of normal tissue architecture by invading neoplastic cells during histological examination is indicative of lymphoma. Additional diagnostics that may improve our knowledge of equine lymphoma include detection of hormone receptors, immunophenotyping, and immunohistochemical analysis for tumour proliferation rates. Prognosis of horses with lymphoma depends on the form of lymphoma and stage at which the horse is presented but death is the common outcome of this disease. Current treatment options are surgical excision, radiation or administration of chemotherapeutic drugs. Treatment of horses with lymphoma can result in palliation and occasional resolution of this disease. Equine oncology is in its infancy, but through further documentation of horses with lymphoma and their response to therapy, a clearer understanding of the disease process and effective treatment of this neoplasm can be developed.