infectious disease

Over 38% of the world equine population (114 million) is made up of donkeys and more than 97% are found in developing countries and are specifically kept for work. Despite their significant contribution to the national economy, the attention given to study the infectious diseases of working donkeys is minimal. To address this The Donkey Sanctuary has been conducting studies in collaboration with Addis Ababa and Nairobi Universities, Central Veterinary Research Laboratory (CVRL) in Dubai and the Trypanosomosis Research Centre (TRC) in Kenya. These studies have shown a high prevalence of some important infectious diseases.

Helminthosis

Helminth infection profiles of working donkeys living in semi-arid or tropical conditions are often very different from those of equids in temperate climates. They are often diagnosed with a high worm burden or faecal egg count irrespective of their age. The high level of age-independent infection may show that donkeys either do not develop protective immunity or that they might have become immuno-compromised, consequent upon the stress of their work intensity and/or undernourishment and general poor husbandry.

Trypanosomosis

Although there is a general belief that donkeys are more resistant, trypanosomosis has been shown to cause severe clinical disease in working donkeys. Epidemiological studies in Ethiopia and Kenya have shown that the prevalence of trypanosomosis was as high as 65%, often with mixed infections of two or more species. In both countries T. congolense was the predominant species followed by T. brucei and T. vivax; often associated with anaemia and poor body condition. Trypanosomosis is claimed by local farmers as the major health constraint of donkeys in both countries. Recent serological studies by The Donkey Sanctuary in collaboration with the CVRL showed a sero-prevalence of 1.1% (n=662) T. equiperdum in Ethiopia.

Piroplasmosis

Equine piroplasmosis is one of the most significant tick-borne diseases of donkeys in Ethiopia and Kenya. Recent studies in Ethiopia in collaboration with CVRL showed sero-prevalence of 53.3% to 58% T. equi and 13.2%-13.3% B. caballi (n=15-395) Most of the cases were associated with anaemia. Similar studies in Kenya reported only T. equi with a sero-prevalence of 81.2% (n=314).

Viral and bacterial diseases

A recent study in Ethiopia in collaboration with CVRL showed a sero-prevalence of 8.5% (n=165) AHS, 84.6% (n=104) EHV-4, 20.2% (n=104) EHV-1, 0.5% (n=662) glanders and 0.2% (n=657) EIA. Similar study made in Kenya also showed a sero-prevalence of 35.2% (n=398) AHS. Donkeys showing typical clinical signs of AHS were noted in Kenya and Ethiopia. Although no epidemiological studies are available, cases of tetanus, strangles, rabies, anthrax and dermatophilosis are common occurrences in donkeys. These studies highlight how important infectious diseases in donkeys are and the need to consider them in overall epidemiological studies and for sound control and prevention strategies.

The number of abandoned or otherwise neglected donkeys has significantly increased in Ireland in the recent past. The real or perceived capacity of the donkey to act as a reservoir of equine infectious disease, and thus pose an increased risk of disease transmission to horses and ponies, may be a factor in this increased abandonment and neglect. The authors here report on a field study exploring the infectious disease transmission threat the donkey poses to the general equine industry in Ireland through an examination of biosecurity standards and the views of horse and donkey exhibitors at nine mixed equestrian events in 2014. Quantitative information was gathered via the organising committee (if any) and through an examination of facilities and procedures. Qualitative information was gathered using a semi-structured questionnaire to ascertain the view of exhibitors regarding the keeping of donkeys and any infectious disease transmission risks posed.

Results

At eight of nine events visited there were no entrance controls, no veterinary examinations, no enforcement of legislation regarding equine identification and equine premises registration and no isolation facilities on site for equids. Contact between donkeys and other equids was largely uncontrolled. Exhibitors had travelled from abroad to one event. Exhibitors generally opined that they did not perceive the donkey to represent any additional infectious disease transmission threat above that posed by other equids; there was however a general sense that donkeys were less well regarded for other reasons including nuisance and uselessness.

Conclusions

When biosecurity controls are not in place (or enforced) to actually check passports, verify identification and equine premises registration, mixed equestrian events may unwittingly act as the mechanism of spread of endemic and potentially more seriously exotic equine infectious disease. Donkeys were not generally considered by equine exhibitors at mixed events in Ireland to represent a heightened reservoir of disease or to pose an increased risk of transmission of contagious disease suggesting that other factors should be considered more important when studying the incidence of abandonment and neglect.