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Title: Unravelling the causes of respiratory disease in the working horses of Ethiopia
Author: Laing, G. A.
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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Worldwide, respiratory disease is an important contributor to loss in equine industries, limiting performance and disrupting work schedules. In Ethiopia, respiratory disease is a frequent finding in horses presenting to veterinary clinics; coughing and nasal discharge has been identified as a priority concern for users of working horses. Despite the interdependency between human and equid health in low income settings, and the fact that 80% of all global equids reside in developing nations, there is little existing literature for this group. This thesis aims to build understanding of disease epidemiology and begin to unravel the causes of respiratory disease in the working horses of Ethiopia, contributing new research to help inform disease reduction strategies in the future, for the benefit of equine health and human wellbeing. An initial participatory appraisal (February-March 2013) involved focus group discussions with 170 equid users. It explored local experience of respiratory disease, documenting the variety of signs (n=21) and syndromes (n=44) people recognised in their animals. The most common signs represented were coughing, altered respiration, bilateral mucopurulent or serous nasal discharge and epistaxis. Thematic analysis of participants’ ideas on aetiology of disease, and what action could be taken to treat or prevent, revealed concepts of communicable diseases and disease caused by, and responding to, management changes or environmental conditions. Subsequently, a cross-sectional survey (August-December 2013) of 350 horses across 19 sites was conducted to determine the prevalence of both respiratory signs and exposure to major respiratory pathogens. The majority of horses examined were carthorses, with over a third reporting recent coughing and around ten per cent with an active nasal discharge. Antibodies towards Streptococcus equi subspecies equi, the causative agent of strangles, were the most prevalent, with 8% of animals showing prior exposure. Prevalence of antibodies to alpha-herpesviruses, picornaviruses, arteritis virus was uncommon and antibodies to influenza were not detected. Finally 108 horses with respiratory disease (coughing, nasal discharge or dyspnoea) were fully examined using endoscopy, alongside 93 unmatched and randomly selected control horses (September –December 2014). Horses presenting with respiratory signs often had evidence of lower airway disease with significantly increased tracheal mucus and neutrophilia compared to control horses. S equi, equine herpesvirus 4 and equine picornaviruses in the lower respiratory tract were detected occasionally, but showed little association with clinical signs. Equine influenza virus, arteritis virus or Mycoplasma spp were not detected. However, gamma-herepsviruses (EHV-2/-5) were found often but not significantly associated with cases. Streptococcus equi subspecies zooepidemicus was significantly associated with case horses. Whether this is as a primary pathogen or secondary coloniser could not be established in this study. Young and old horses were found to be at higher risk for disease, as were horses performing strenuous work, drinking from stagnant water sources, and those housed on a cobbled floor. Findings suggest that respiratory disease in this population is multifactorial but that endemic S equi is likely a significant contributor and S zooepidemicus also appears to play a role.
Supervisor: Pinchbeck, G. ; Christley, R. ; Radford, A. ; Newton, R. ; Stringer, A. ; Aklilu, N. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral