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Dental disease in donkeys: frequency and association with colic and body condition

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Methodology

Four part project including surveys, case control study, and retrospective analysis of database.

Aims
  1. To describe and estimate the prevalence of abnormal dentition in the donkeys housed at The Donkey Sanctuary.
  2. To identify and quantify risk factors for colic, in particular impaction colic, in donkeys at The Donkey Sanctuary and on foster in the UK.
  3. To describe and quantify the association between dental disease and impaction colic in donkeys.
  4. To describe and quantify the association between dental disease and body condition score in donkeys in the UK.
Results
  1. Dental examination records from Jan 2003 to Mar 2005 found 43.6% of donkeys had dental disease, of these 12% had more than one abnormality. Disease included missing teeth (34.1%), step mouth (4.7%), shear mouth (4.3%), wave mouth (1.5%), diastema (1.3%), undershot jaw (1%), overshot jaw (0.3%). There was a positive correlation between age and dental disease. Results of the 2006 prospective study found a much higher incidence rate of dental disease,92.1% of the sample had at least one dental abnormality/disease.
  2. Results obtained from retrospective database analysis from Jan 2000 to Mar 2005 found incidence rates for colic and impaction colic were 5.9 and 3.2 episodes per 100 donkeys per year respectively. Peaks were seen in late autumn and troughs in spring/summer. 51% of impaction colics resulted in death or euthanasia. Dental disease, musculoskeletal problems, previous history of colic and farm location were all identified as risk factors. Donkeys that were older, on extra feeds or underweight were also at an increased risk of suffering colic. Donkeys in foster homes between Sept 2004 and Aug 2005 had a lower incidence rate at 1.4 cases per 100 donkeys per year. Of these animals those fed 2 concentrate meals per day, or those bedded on rubber were more at risk of colic. Results from the prospective study Jan to Dec 2006 multivariable analysis which was performed in response to questions raised in the first part of the study found that a number of donkey and management variables were associated with the risk of impaction colic. The greater the number of carers responsible for the donkey, the greater the increase in risk with donkeys with 1 or 2 carers at the lowest risk. Donkeys that were fed extra rations as concentrate feed were at a 5 fold increased risk of impaction. In addition animals with no access to pasture were at increased risk (odds ratio 3.4) compared to those with 24 hour access. Donkeys bedded on paper were at increased risk of colic, however this has wide confidence intervals due to the small number of cases and controls that were bedded on paper. These animals were in the hospital and at 2 other farms. Animals that were vaccinated in the previous 2 weeks were also at increased risk of colic. Animals that had weight loss in the previous 4 weeks were at increased risk of colic although few animals had this health problem. Other variables relating to body condition did not remain in the multivariable model. A number of dental pathologies remained in the multivariable model; these included missing cheek teeth, ulcers, diastema and worn teeth which all increased the risk of colic. The presence of hooks was still associated with decreased risk of colic. After allowing for the above variables age was no longer significant (P=0.9) and forcing age into the model did not changed the effect of the other variables. Forcing of month (or season) into the final model showed that this was not significant, demonstrating that this model explains some of the seasonality. The farm level variation was zero after the inclusion of fixed effects suggesting that these fixed effects explained differences in farm.
  3. There was a significant increase in the frequency of dental disease in donkeys that died from colic (80/94) than in those that recovered from colic (34/53) between Jan 2003 and March 2005. Results of the 2006 prospective study also confirmed an association between dental disease and colic, 92.1% of the sample had at least one dental abnormality/disease. Number of missing teeth and diastemata are positively correlated with impaction colic. There pathologies were also associated with ageing, whereas hooks and sharp edges were found in younger animals and not associated with increased risk of impaction colic.
  4. Initial results from the retrospective analysis found donkeys with dental disease had a marginally significant (p=0.05) lower body condition score of 4/10 compared to 4.7/10 in those without dental disease. These results were supported by the prospective study which also found lighter/lower condition animals more at risk of impaction colic.
Conclusions

The incidence of colic in donkeys appears similar to that reported in horses. Age, weight, dental disease and supplementary feeding are known to be risk factors in other equines.

Pain recognition in donkeys

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End date
Methodology
  1. Retrospective review using database.
  2. Video surveillance and behaviour coding. 3) Prospective questionnaires.
Aims
  1. To determine the prevalence of main pathologies in euthanized Donkey Sanctuary donkeys.
  2. Devise approaches for evaluating pain from behaviour.
  3. Devise pathology scales.
  4. Evaluate associations between ante mortem behaviour and post mortem pathology in UK Donkey Sanctuary donkeys.
  5. Donkeys slaughtered at an abattoir in Mexico.
Results
  1. Figures on prevalence of 6 main pathologies donkeys PTS UK between 2001 and 2008: dental disorders (80%), vascular disease other than aneurysm (61%), arthritis (55%), foot disorder (45%), gastric ulceration (42%), gastrointestinal impaction (19%).
  2. Disease/pain cases spent 10% more time lowered head carriage, 15% less time with ears in combinations (ie ears more static), end stage cases spent 31% more time recumbent and 40% less time eating, list of behaviours and associated pathologies.
  3. Number of pain related behaviours found to be related and grouped together.
  4. Positive association between ante and post mortem findings (approx 70% agreement) and presence of pain (approx 80% agreement) in donkeys euthanized in UK. 73.5% of donkeys were receiving treatment at the time of euthanasia, including 65% on non-steroidal anti-inflammatories (NSAIDs). General agitation, tachycardia and discomfort; locomotion and stance related behaviours significantly increased the odds of a veterinarian stating that donkey is in pain. General depression and abnormal membranes; general agitation, tachycardia and discomfort; evasive and protective behaviours and locomotion and stance related behaviours significantly increase the odds of a donkey being assessed as having an overall higher degree of pain.
  5. Of donkeys slaughtered in Mexico there was approximately 80% agreement between pain presence ante and post mortem. 6) Figures on prevalence of 6 main pathologies in donkeys presented for slaughter Mexico: alimentary and adnexa lesions (85%) including dental disorders (32%), integument lesions (70%), respiratory disease (48%), musculoskeletal problems (29%), mucoid fat degeneration (29%).
Conclusions

Clear associations between ante/post mortem findings in 70% of cases means potentially 30% of donkeys are being misdiagnosed, this figure highlights the need to progress on current diagnostic tools and differentials. Agreement on presence of pain ante and post mortem was found in approx 80% of UK and Mexican cases, leaving approx 20% with potentially undiagnosed pain. It is possible that type of lesion and the individual clinician may affect this relationship. Lesions found in donkeys presented for slaughter in Mexico are possibly related to malnutrition, pain and stress. The results offer an oversight of the living conditions of the Mexican donkeys and their owners. The presence of anthracosis in donkeys (47.8%) may serve as example.

50 significant underlying relationships between specific behaviour(s) and pain related lesion(s) have been characterised, and an indication of the strength or ability of the pain related lesions to elicit one or all the behaviours of the related behaviour cluster given. The highlighted key behaviours/signs will aid the veterinarians in:

  • Improving differential diagnosis;
  • improving the ability to recognise pain in donkeys and the underlying features. Consequently, enabling a better treatment selection, including suitable analgesia for donkeys;
  • and finally provides a list of behaviours/signs to assist monitoring of treatment enabling an informed assessment of a donkey’s prognosis.

A seroepidemiological study of African horse sickness in Limuru and Lari districts, Kenya

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Methodology

Prospective questionnaire, clinical examination.

Aims
  1. To estimate the prevalence of AHS antibodies in the donkey population of Kiambu West District, Kenya.
  2. To identify the risk factors for AHS in this population.
  3. To determine the level of knowledge on AHS in donkeys among donkey owners in Kiambu West District, Kenya.
Results
  1. The sero-prevalence of AHS in donkeys sampled after the heavy rains was estimated at 35.2% (70/199) for the two divisions, while that for the dry season was estimated at 26.7% (55/199). The prevalence of AHS in donkeys during the two periods was 31% (125/398). There was a statistically significant difference in the two prevalences (Z=2.89). The prevalence of AHS in the donkeys that were re-sampled in Kambaa, decreased from 60% (18/30) in May/June to 20% (6/30) in August/September. This difference (Z=4.47) indicates that donkeys are not long term carriers of AHSV or fewer vectors during the dry season. There was a poor level of agreement between ELISA test results and clinical presentation of the illness as only 3 cases were presented with clinical signs of a swollen head and congested conjunctival mucosa. These 3 cases had detectable antibodies to the virus, the poor agreement was with the other 67 cases positive on ELISA test but with absence of clinical signs. Further studies need to be carried out to determine the duration that AHSV antibodies remain present in donkeys.
  2. Division and sub-location were controlled in the mixed models logistic regression analysis of the risk factors. In the univariate analysis, age of the donkeys, presence of a water stream, source of the donkey, donkey use, vaccination status and housing were the statistically significant variables and were thus included in the multivariate analysis. Age of the donkey (p-value 0.02) and presence of a water stream (p-value 0.03) were significant risk factors and might have contributed to the high prevalence of AHS among donkeys in Kambaa and Rwamburi sublocations. This meant that older donkeys (9-12yrs) and those grazing near water streams were two times more likely to be exposed to AHSV. A water stream likely favoured increased vector(s) population, and transmission of the AHSV.
  3. A small proportion, 21.9% of questionnaire respondents knew of AHS. 8.2% were familiar with the clinical signs of swollen head and congested conjunctival mucosa and 9.5% reported severe body weakness as a sign of the disease. The low level of awareness of AHS among household members may be attributed to lack of previous dissemination of information on the disease. Many respondents reported donkeys with AHS clinical signs as having been poisoned, bitten by snakes or suffering from sudden pneumonia – in hindsight these donkeys may have been AHS cases. Low public awareness of the disease may be resulting in under-reporting.
Conclusions
  1. African Horse Sickness is endemic in donkeys in all six of the study sub-locations of Lari and Limuru divisions.
  2. The prevalence of AHS in donkeys demonstrates a seasonal variability; which was 35.2% in the rainy season and 27.6% in the dry season.
  3. Clinical signs may be used as a diagnostic indicator for the presence of AHS in donkeys. However, sub-clinical cases may be appropriately diagnosed using ELISA.
  4. AHS presents a clinical form of disease in donkeys that has a seasonal manifestation.
  5. Age (9-12) and presence of water streams near grazing areas are significant risk factors.
  6. Vaccination against AHS was not practiced in this region; hence seropositivity was not confused in terms of interpretation of data.

Insecticide resistance in lice at The Donkey Sanctuary: strategies to mitigate its effects

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Methodology

Prospective questionnaire and sample collection, and in vitro laboratory assay and analyses.

Aims
  1. To identify the presence of insecticide resistance in donkey lice.
  2. To identify risk factors for pediculosis.
  3. To develop a useful tool for diagnosing and estimating louse burden.
  4. Developing targeted selective treatment.
  5. Develop novel methods for controlling lice in donkeys.
Results

A strong seasonal pattern of louse infestation was observed, with the highest number of donkeys infested in winter (Oct-Mar); with more than 80% of the animals were infested in the winter months. A significant age variation in lice infestation was also observed; young and old donkeys of age less than 4 years and greater than 30 yrs, respectively, were found infested with more lice than middle aged animals. The axilla and supraorbital fossa were identified as being the sites most commonly populated by live lice in both housed and outdoor donkeys (P<0.05). In addition, the presence of lice eggs in the first 2cm of the coat is a good indicator of an active infestation. Donkeys’ hair length was positively correlated with the presence of lice (P<0.05) but not with the number of lice each donkey carried (P=0.1). Excoriation consistent with hair fibre shortening was indicative of pediculosis and the amount of this type of lesion was positively correlated with louse burdens. However, more severe dermal rub lesions, such as alopecia, showed no association. Clipping in the winter was found to have no significant effect (P=0.15) on louse abundance examined after 2 or more weeks clipping; however, in the summer months clipping had a detrimental effect on louse populations. The efficacy study revealed a high level of tolerance to permethrin ((SwitchTM, VetPlus Ltd, 4% (w/v) and cypermethrin (DeosectTM, Pfizer Ltd., 0.1% (w/v) consistent with resistance development. In vitro contact assays showed that 4% permethrin and cypermethrin resulted in less than 30% louse mortality after 24 h exposure. On the other hand, tea tree and lavender essential oils were identified as clinically and statistically significant (P<0.05) methods of louse control used at 5% concentration as a topical grooming spray.

Conclusions

The study showed high lice infestation in donkeys, season and age of the animals being the main risk factors for having high infestation. A convex quadratic relationship between donkey age and probability of carrying lice was found, with the elderly and young were at higher risk. Detection of lice can be aided by targeting animals most at risk of infestation. In addition, excoriation consistent with light coat abrasion is an indicator of louse presence. However, overreliance on donkey characteristics and appearance is likely to lead to misdiagnosis of pediculosis. For accurate detection, examination of the coat should be thorough and include the most commonly infested louse predilection sites namely the axilla and supraorbital fossa. Although more animals are found infested in winter months, a year round management protocol may be advisable, as summer clipping appears to have a detrimental effect on louse populations.

The insecticide efficacy trial showed that the population of donkey lice at the Donkey Sanctuary developed a high level of tolerance to the pyrethroid insecticides previously used for their control. Such a high level of tolerance may account for the treatment failures reported at the Sanctuary in recent years and highlighted the need for alternative louse control strategies. The preliminary study made to address this indicated that tea tree and lavender essential oils provide a clinically useful level of B. ocellatus control and with further research and refinement they could form the basis of future louse control regimes in donkeys.

Keywords

Essential oils in the management of the donkey louse, bovicola ocellatus

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Methodology

In vivo field trial. Suspensions of 5% (v/v) tea tree or lavender oil or an excipient only control were groomed into the coats of winter-housed donkeys (n = 198) on 2 occasions, 2 weeks apart. Louse counts were conducted before each application and 2 weeks later.

Objectives

To assess the effects of incorporating the essential oils of tea tree and lavender into a grooming programme for populations of donkeys with natural infestations of Bovicola ocellatus in the UK and Ireland when louse populations were at their winter seasonal peak.

Results

After 2 applications, the groups groomed with lavender or tea tree oil suspensions had a significant reduction in louse intensity, with a mean decline in louse abundance of 78% (95% confidence interval 76–80%). Louse numbers in the groups groomed with excipient only either did not change or increased significantly. Donkey hair length had no effect on the decline in louse numbers.

Conclusions

These results demonstrate that the inclusion of essential oil suspensions during grooming can be used to manage louse populations successfully.

Keywords

Reference intervals for biochemical and haematological parameters in mature domestic donkeys (equus asinus) in the UK

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Research award
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Methodology

Blood samples were collected over a period of 3 years and 4 months from clinically healthy donkeys being prepared for rehoming from The Donkey Sanctuary. Complete blood counts and biochemical profiles were carried out within 24 hours of sampling.

Aims

To revise previously established haematology and serum biochemistry values in adult domestic donkeys in the UK.

Results

Blood samples from 138 donkeys were examined, ranging in age from 4-24 years. Data from 18 haematological and 20 biochemical analytes were analysed using non-parametric statistical testing. Reference interval transferability was calculated showing 15/18 haematological and 14/19 biochemical RIs were transferable between previous donkey RIs and these RIs. Of particular clinical note when comparing the new donkey RI with that reported previously is a narrowing of the RI for triglycerides with the upper limit of the range being 2.8 mmol/l as compared with the previous 4.3 mmol/l. It is very important that veterinarians note this difference as this upper limit of triglycerides is commonly used to determine the risk of a donkey becoming hyperlipaemic.

Conclusions

This study establishes reviewed reference intervals for haematological and biochemical parameters for donkeys. The reference intervals in this study are appropriate for use in non-working, mature donkeys kept in temperate climates and are now used by the diagnostic laboratories of The Donkey Sanctuary UK to aid clinical decision making in their resident animals. These reviewed reference intervals also underpin comments appended to results of blood samples from privately owned donkeys submitted by veterinarians to the diagnostic laboratory of The Donkey Sanctuary. These reference intervals may not be relevant to other donkey populations such as working donkeys in tropical regions. Their extrapolation to animals of extremes of age or in specific physiological states should be undertaken with caution. The lack of transferability noted between study parameters in donkeys and horses highlights the importance of using species-specific reference intervals for clinical assessment of veterinary cases.

Keywords

Gastric ulcers in donkeys: prevalence and effect of diet

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Methodology

Retrospective data analysis from PM records. Variables examined included location and size of ulceration, body condition score and feeding regime.

Aims
  1. To determine the prevalence of gastric ulceration in a population of elderly donkeys at PM.
  2. To determine the site of gastric ulcers and to evaluate the extent of ulceration.
  3. To determine if forage and concentrate feeds are risk factors.
Results

Gastric ulcers recorded in 41% of 426 donkeys necropsied. Of which 89% of these donkeys had ulceration of the margo plicatus (squamous area), and 10% of had ulceration of the glandular area. 49% of ulcers were medium size (>2cm squared but <10cm squared), 28% small and 23% extensive. Donkeys on cereal based supplementary feed had 55% prevalence rate, donkeys on fibre based supplementary feed had 33% prevalence rate, donkeys on forage only had 34% prevalence rate. Chi-square test found association between cereal based diet and presence of ulcers.

Conclusions

Gastric ulceration common at necropsy. This is the first evidence of this nature in this equid species. Maybe surprising as donkeys in the UK are thought of as relatively sedentary with a low stress lifestyle and free access to forage - not typical risk factors for gastric ulceration. Supplementary feeding of fibre based products does not increase risk of ulceration compared to forage only diet.

Epidemiology and control of donkey trypanosomiasis and their vectors in the Lamu Islands

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Methodology

2 study periods (dry and wet season), PRA, tsetse fly survey, tick survey, buffy coat technique (BCT), Giemsa staining, faecal egg count (FEC), drug sensitivity testing, social survey.

Aims
  1. To conduct participatory rural appraisal (PRA) of donkey farmers and community health workers with a view to assess their knowledge of donkey health and husbandry issues and therefore determine possible community intervention points.
  2. To determine the association between host, temporal, spatial and management factors and prevalence of trypanosomiasis and babesiosis in the donkey population of the Lamu archipelago.
  3. To characterise the isolated trypanosomes through phenotypic, molecular and drug sensitivity determinations.
  4. To determine the seasonal distribution and vectorial capacity of tsetse (and non-tsetse) vectors of trypanosomiasis in the archipelago.
Results

1) Amongst the greatest constraints of donkey keeping were diseases including trypanosomiasis. As far as trypanosomiasis is concerned, findings indicate that the inhabitants of the Island were knowledgeable about the link between trypanosomiasis and tsetse. Apart from tsetse, the other vectors that affected donkeys included ticks, mites and biting flies. However, the distinction between tsetse flies and various biting flies was difficult for the respondents to make. The presence of wounds in donkeys and indications from key informants about overloading, over beating and poor watering practices as constraints may be a pointer to the need for increased sensitization of keepers for improved donkey management practices and increased productivity. The management of donkey health problems was perceived as a role to be played by the Donkey Sanctuary personnel. Community ownership of donkey management in terms of diseases and deworming was low. The majority of FEC results (McMasters) were negative, 84 and 72.3% in the dry and wet seasons respectively. Scarcity of feed and pasture for donkeys was also singled out as a constraint. 2) Trypanosomes were encountered in 3.1 and 7.5% of donkeys examined in dry and wet season respectively, the association between prevalence and season was significant at p<0.05. There was no significant difference in prevalence rates between villages. Infection rates were higher in donkeys in poor body condition ranging from 12 to 46% percent of poor donkeys in the dry and wet season respectively as opposed to 1.9 and 6.1% of those in good body condition. During both seasons mean PCVs of infected, young, female and donkeys in poor condition were lower than that of uninfected, adult, male and good condition donkeys. Anaemia (PCV <25%) was present in 88 and 71% of infected donkeys compared to 34.1 and 37.7% of uninfected donkeys in the dry and wet seasons respectively. Full results of PCR analysis are not available but preliminary indications are that there may be a number of sub-patent infections accounting for the anaemia. 3) Three species of trypanosomes were detected via BCT and Giemsa staining: Trypanosoma congolese Broden (68.7% of cases), Trypanosoma vivax Zieman (21.8%), Trypanosoma brucei Plimmer and Bradford (6.2%) and 6.2% of donkeys had mixed infections. BCT technique has limitations in cases of chronic infection and PCR analysis for a more accurate identification of prevalence is still pending, initial results indicate further species of Trypanosomes may be present and confirm suspicions of false negative results using smears. Drug sensitivity evaluation was hampered by difficulties with in vitro cultivation and was ceased. Ticks were identified in 51 and 43% of donkeys in dry and wet seasons respectively, although mean number of ticks were very few at 4.2 and 2.6 for dry and wet seasons. Dry season donkeys were found to be free from tick-borne disease, however Babesia was identified in 6 donkeys sampled in the wet season. Prevalence of ticks varied between villages in the wet season (p=0.0002), results showed that donkeys regularly driven through seawater would have fewer ticks. 4) The entomological surveys revealed the presence of Glossina pallidipes Austen species of tsetse fly and other biting flies Stomoxys spp. Linnaeus, Tabanus spp. Linnaeus and Haematopota spp. Linnaeus were also caught. Tsetse fly dissection did not reveal any trypanosomes, however PCR sample results may be a truer measure of trypanosome challenge as dissection may underestimate true infection rates.

Conclusions

This study confirmed the importance of trypanosomiasis in donkey health and productivity and negates the common notion that donkeys are disease-resistant. Veterinary and extension workers should give donkeys equal attention as other domestic livestock, considering the important role they play in domestic economies. Trypanosomiasis is a major cause of anaemia and unthriftiness in donkeys, results associate anaemia as a reliable sign of either overt or subpatent trypanosomiasis and donkeys with pale mucous membranes should be considered for treatment for trypanosomiasis. The distribution and numbers of tsetse do not justify vector control interventions. Donkeys originating from the mainland should be treated prior to shipment due to high prevalence rates, limited sensitivity testing of isolates identified no reason to review the dosage of samorin currently in use (0.5mg/kg). Tick numbers were low but simple control strategies such as bathing in salt water appear to be effective so should still be emphasized.

Risk factors for the development of hyperlipaemia in a population of donkeys

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Methodology

Retrospective case-control study using database records.

Aims

To describe and determine the prevalence of hyperlipaemia in a population of donkeys and to determine risk factors for the development of the disease.

Results

A total of 449 clinical cases of hyperlipemia were reported over a 4 year period, with an associated mortality rate of 48.5%. Concurrent disease was present in 72% of donkeys and was the greatest risk factor (OR = 76.98); others included cardboard bedding (OR = 3.86), movement (OR = 3.94), weight loss (OR = 6.4), dental disease (OR = 1.73), and concentrate feeding (OR = 1.87).

Conclusions

This study shows that this population of donkeys in the UK often develops hyperlipemia, particularly in response to stress or primary illness, and provides useful insights in to health and management risk factors that may be addressed to decrease the risk of hyperlipaemia both in the study population and in other similar donkey populations.

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