Coughing in Horses

Introduction to Coughing in Horses

The lecture is focused on two key topics regarding coughing in horses, covering all ages from older foals to adults (neonates are not included). This topic will be essential for upcoming clinical scenarios.

Learning Objectives

The learning objectives for this lecture series include:

  1. Listing the major differentials for coughing in horses across all ages.

  2. Discussing the pathogenesis, epidemiology, and clinical presentations of various infectious diseases:

    • Equine Herpesvirus (EHV) 1 and 4

    • Equine Influenza

    • Equine Rhinovirus

    • Equine Viral Arteritis

    • Bacterial Pneumonia

    • Strangles

    • Rhodococcus

    • Equine Asthma

  3. Understanding diagnostic, investigative, treatment, and prevention methods for these diseases.

Structure of the Lecture

The lecture content will be divided into:

  • Infectious causes of coughing in adult horses

  • Infectious causes of coughing in older foals and weanlings

  • Non-infectious causes

Understanding Respiratory Disease

When assessing respiratory disease, it is crucial to differentiate between upper respiratory tract (URT) and lower respiratory tract (LRT) diseases, as this classification influences potential differentials.

  • Clinical Signs: Coughing is a sign that can be seen in both URT and LRT infections, but other symptoms such as fever and nasal discharge tend to differ:

    • UrT diseases often show:

    • Fever

    • Nasal discharge (serous, bilateral)

    • Coughing

    • Enlarged submandibular lymph nodes

    • LRT diseases may or may not show fever, may lack nasal discharge, and typically exhibit coughing.

Infectious Causes in Adult Horses

Among the infectious causes for coughing in adult horses, several viruses are noteworthy.

Equine Influenza Virus (EIV)

  • Impact: Major cause of upper respiratory disease in horses globally.

  • Strains: Historically identified strains were H7N7 and H3N8, with the latter being relevant today.

  • Transmission: Primarily spread via aerosols and direct contact.

  • Incubation Period: 1 to 3 days.

  • Clinical Presentation:

    • Symptoms include fever, cough, and nasal discharge.

    • Respiratory epithelial cell destruction leads to loss of mucociliary function, facilitating secondary infections.

  • Vaccination Considerations: Immunity from both natural infection and vaccination is short-lived (2-3 months). Vaccines are developed targeting existing strains but may lag in effectiveness due to antigenic drift.

Equine Herpesvirus (EHV) 1 and 4

  • EHV Overview: Highly endemic, often latent, and can reactivate under stress conditions. This virus is capable of abortion and neonatal disease when the infecting mare is pregnant.

  • Epidemiological Context: Approximately 75% of horses harbor latent infections, which pose risks to naive horses in contact.

  • Clinical Signs: Similar to equine influenza but potentially leading to more severe complications.

Clinical and Diagnostic Approaches

A structured approach is vital in diagnosing these diseases.

  • Diagnostic Testing: Various methods include:

    • Serology (paired samples 10-14 days apart)

    • Nasopharyngeal swabs (for virus isolation or PCR)

    • Observation for clinical signs

    • Endoscopy to observe secretions in the airway.

  • Treatment:

    • Supportive care (isolation, hydration, anti-inflammatories)

    • Monitoring for secondary infections

Bacterial Pathogens
Bacterial Pneumonia and Strangles

  • Bacteria Identified: Streptococcus equi equi (causes strangles), among others.

  • Bacterial infections present primarily with LRT signs, potentially resulting from upper respiratory virus infections or non-infectious conditions that compromise airway defenses.

Non-Infectious Causes of Coughing
Equine Asthma

  • Classification: Mild to moderate equine asthma vs. severe equine asthma.

    • Asthma has various historical terminologies (COPD, heaves, etc.).

  • Common in performance horses, affecting 20-65% of racehorses (varies by study).

  • Diagnosis: Based on bronchoalveolar lavage findings, increased mucus, and inflammatory cell populations, without increased respiratory effort at rest.

  • Treatment:

    • Environmental management to reduce inhaled irritants.

    • Antimicrobial treatment if secondary bacteria are cultured.

    • Corticosteroids or bronchodilators may be indicated depending on inflammation.

Conclusion and Further Learning

The lecture is intended as an expansive introduction to coughing in horses, emphasizing the importance of adequate diagnosis, treatment, and management of both infectious and non-infectious respiratory diseases. Additional information on strangles and treatment protocols will be covered in further sessions. Questions and clarifications can be addressed during breaks.