Kenya

Semi-longitudinal study of trypanosomiasis and its vectors in donkeys (equus africanus asinus, fitzinger) in the Lamu archipelago

Phoebe Mukiria
Raymond Mdachi
J. Thuita
James Mutuku
Kennedy Wanjala
J. Omolo
Mulugeta Getachew
Andrew F. Trawford
Johnson Ouma
Grace Murilla
Presentation date

Kenya is home to some 600,000 donkeys that are found virtually in all ecological zones where they provide transport and draught power. In the Lamu archipelago where there is no motorised transport, donkeys are virtually the only available means of transport helping to transport farm produce, building materials and for getting from one place to the next. This study was conducted in April (dry season) and November 2009 (wet season) in four villages in Pate Island to investigate the prevalence and species of trypanosomes infecting donkeys and to identify the fly vectors playing a role in the transmission of trypanosomosis. Blood samples were collected from 288 and 319 donkeys and examined by buffy coat technique (BCT) and Giemsa stained blood smears. Trypanosomes were encountered in 3.1 and 7.5% of the examined donkeys in the dry and wet season respectively and there was no difference in the prevalence between villages during both seasons (p=0.159 and 0.709) but there was a significant difference (p=0.006) between seasons. Three species of trypanosomes detected were, in order of predominance were Trypanosoma congolense Broden (68.7%), Trypanosoma vivax Ziemann (21.8%) and Trypanosoma brucei Plimmer and Bradford (6.2%). Another 6.2% were mixed infections. There difference in mean PCVs between trypanosome infected and non-infected donkeys dry and wet seasons ranging significant to highly significant (p<0.05 and p<0.001) respectively. Trypanosome infection had a significant effect on mean body condition score of the donkeys during both seasons (p<0.05 and p<0.001). Prevalence of trypanosome infection was found to be independent of sex and age. However, mean PCV was significantly associated with age, sex and body condition scores. The entomological surveys revealed the presence of Glossina pallidipes Austen and other biting flies namely Stomoxys spp Linnaeus, Tabanus spp. Linnaeus, and Haematopota spp Linnaeus. Though the use of BCT for detection of trypanosomes in the field is almost universal, it has limited application especially in chronic infections and the field samples are in the process of being analysed using PCR to give a more accurate picture of the prevalence and as it relates to health and productivity of donkeys.

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Not published as conference proceedings

Non Tsetse transmitted animal trypanosomosis (NTTAT) in working donkeys

Mulugeta Getachew
Presentation date

Although donkeys are considered to be more resistant to trypanosomes, they are often seen causing severe clinical disease, particularly anaemia, lethargy and boor body condition, in immuno-compromised animals due to stress from overwork, poor management practices and low quality diets. Studies made by The Donkey Sanctuary in Kenya showed a high prevalence of both tsetse and none tsetse transmitted trypanosomes. T. congolense and T. brucei sp are the most highly prevalent tsetse transmitted trypanosomes while T. vivax is the second most prevalent, next to T. congolense. Infection prevalence of T. vivax as high as 30% were diagnosed in Kenya and Ethiopia using parasitological techniques. These prevalences could have been higher had they been diagnosed using molecular techniques, as it was shown by the study made in Gambia, in which they found an infection prevalence of 87% using PCR.

Dourine is mostly diagnosed in horses from the highland regions in Ethiopia. Recent serological study made in Ethiopia, however, revealed not only in donkeys but across all agro-ecological zones. However, as the CFT does not differentiate between the infection of Dourine and Surra, it is difficult to know the true epidemiology of these diseases among equids where they both exist. Although Surra is reported in donkeys from different countries, it is not reported in donkeys in Ethiopia. However, Surra is endemic in camels in the arid and semi-arid regions of Ethiopia. The recent migration of camels to the mid-lowland areas during the dry season in search of feed might spread the disease among equids in the area.

A recent study made in Gambia by Glasgow University, funded by The Donkey Sanctuary, showed a fatal neurological syndrome among donkeys and horses caused by trypanosomosis. The aetiological agent of this emerging neurological syndrome has been established based on the presence of trypanosomes in the brain of affected animals. However, given the genetic homology between T. evansi, T. brucei brucei and T. equiperdum, it was not possible to confirm which one of these is causing this devastating condition. To solve this mystery and identify the species of trypanosome involved, study on further molecular characterization of cerebral trypanosomosis is underway in Gambia, a project funded by The Donkey Sanctuary.

The infection of trypanosomes in donkeys raises certain questions that need to be addressed. Given the high infection prevalence in the donkey population and associated diseases:

  • Are they really carriers/resistant to trypanosomosis?
  • The welfare implication of trypanosomosis in donkeys.
  • What would be the role of donkeys in the epidemiology of trypanosomosis?
  • The impact of exclusion of donkeys in the control of animal trypanosomosis?
Keywords
Not published as conference proceedings

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

Status
Applicant(s)
Researcher(s)
Research award
Start date
End date
Country
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.

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

Status
Start date
End date
Country
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.

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