Prevalence of camel trypanosomosis and associated risk factors in Arero district, Borena Zone, Southern Ethiopia

Author(s): Aden Giro and Kula Jilo* A cross-sectional study was conducted to determine the prevalence of camel trypanosomosis and assesses its associated risk factors in Arero district, Borena Zone, Oromia region, southern Ethiopia from November 2015 to March 2016. Blood samples were collected from randomly selected 385 camels. Giemsa-stained blood smears and Buffy coat technique were used for the detec ... Abstract View Full Article View

Currently, due to population growth, increased frequencies of drought recurrence, shrinkage and deterioration of the rangeland by bush encroachment (grazing land for their cattle) together with increasing aridity are the major governing factor for the expansion of camel production. Thus camels have been indispensable alternative to cope up with the escalating rangeland ecological challenges [7]. In spite of these facts, its development is hampered by different constraints. The most important constraints to camel productions are a diseases, poor veterinary service and lack of attention from government [8]. In Borana area the major health problems besides camel trypanosomosis reported in camel are camel pox, pneumonia, contagious skin necrosis and parasitism [9].
Parasitism is one of the major problems in camel production that affect the productivity of livestock [10][11][12]. Of these parasitic diseases, camel trypanosomosis is the main disease prevalent in most areas where camels are found [13]. In Borena, the disease is well known to the breeders by the local name "Dhukana" and is given the fi rst priority in its order of importance among camel diseases [14].
Camel trypanosomosis is an infectious disease caused by the hemofl agellate protozoan parasite caused by Trypanosoma evansi. It was discovered by Griffi th Evans, in 1880 from infected camels and horses in India. The local Indians had a local name for the disease called Surra, meaning emaciated [15]. T. evansi is spread mechanically by Haematophagus fl ies such as horsefl ies (Tabanus) and stable fl ies (Stomoxys) which are endemic in Africa, Asia and South America. Although in America the vampire bat also acts as a vector as well as reservoir hosts [16].
An essential factor in mechanical transmission of trypanosome is interrupted feeding; the fl ies move quickly from one host to the other to transmit the parasite within a short period before the parasite dies. Trypanosomes do not survive for more than 10-15minutes in the proboscis of the fl y. The tsetse fl y (Glossina spp.), like other blood sucking fl ies, can act as a mechanical vector for T. evansi in the areas where they co-exist. However, since camels are usually kept in nontsetse endemic areas, the role of the tsetse fl y in transmission of surra is insignifi cant [17].
Surra has numerous negative impacts on productivity. It causes anorexia that leads to weakness, emaciation, drop in milk yield and decrease in meat yield, poor traction power, increased abortion and death. This disease is major causes of economic losses in camel rearing areas, causing morbidity of up to 30.0% and mortality of around 30% [13]. Trypanosomosis has a wide host spectrum, the main host species varies with the geographical region. In Africa, camels are the most important host, whilst in Central and South America the horse is principally affected. The disease is most severe in horse, donkey, mules, camels, dogs and cats [18].
In Ethiopia, the prevalence of camel trypanosomosis and its vectors have not yet been fully documented in most parts of the country. A study conducted in southern Ethiopia indicates that trypanosomosis is one of the leading health problems [19] and a prevalence of 21% has been reported in eastern Ethiopia [20]. However, there is no documented information about the prevalence of camel trypanosomosis and associated risk factors in the study area. The prevalence of the disease and associated risk factors is crucial to establish effective control strategy.
Therefore the objectives of the present study were:  To determine the prevalence of camel trypanosomosis in the study area  To identify the associated risk factors with disease occurrence in the study areas.  [22]. Arero district was characterized by arid and semi-arid lowlands with some mid-altitude areas. Pastoral and agropastoral population whose livelihood is mainly dependent on range livestock production predominantly occupies the semiarid lowlands. The area rain pattern is bimodal type with the main rainy season (ganna) extending from mid-March to May and the small rainy season (hagayya) from mid-September to mid-November. The other two seasons are the cool dry season (adolessa) extending from June to August and the major dry season (bona) extending from December to February [23]. The climate of Arero is generally tropical climate, with little rainfall throughout the year with the annual rainfall was estimated at 400-700mm. The temperature of area is an average of 18°C and reaching as high as 25°C [22].

Study population
The study population consisted of camels of all age groups and both sex residing in Arero district that were managed under pastoral production systems. All study animals were randomly selected from the population at temporary livestock camps ("Fora"). A total of 5 pastoral Associations (PAs), mainly Citation: Giro  Oroto, Bobella, Silala, Didole and Tille were included in the study. The PAs were identifi ed on the basis of accessibility to villages by vehicle or proximity to road and camel population and then selected randomly.

Study design
A cross-sectional study design was carried out between November 2015 to March 2016 to determine the prevalence of camel trypanasomosis and assess associated risk factors in the study area. Community Animal Health Workers were used as channel to reach camel owner and camel population in the PAs. Herds were visited and samples were collected early in the morning before camels were released to the fi eld. The collected samples were immediately kept in ice box and transported immediately to the Yabello Regional Veterinary parasitology laboratory (Y.R.V.L) for examination. Camels were selected for blood sample by using simple random sampling method.
Also questionnaire was prepared and displayed for randomly selected animal owner from fi ve peasant associations to assess the knowledge, attitudes and practices of camel owners concerning camel trypanosomosis.

Sample size determination
The number of animals to sample was calculated according to Thrusfi eld [24], considering a minimum expected prevalence of 50%, an accepted error of 5% and a confi dence level of 95%, since there was no previous survey conducted in the study area.  [25].

I. Giemsa stained thin blood smear
The blood smears were achieved directly after blood collection from heparinized vacutainer tube taking the blood by heparinized capillary tube into clean slides after labeling of the slide. Thin smear was made as per method described by [25].
The air-dried smears were fi xed in absolute methanol for 3minutes to avoid all possible deteriorations. The fi xed blood smears were immersed in upright position in Giemsa stain solution for 30minutes. The stain was then poured off; the slide washed thoroughly in distilled water and allowed to drip-dry in an upright position before microscopic examination. After air drying, the slides were examined under oil immersion objective lens (100x) for detection and identifi cation of trypanosome species based on their morphological characteristics depending on their size, the shape of the posterior end, the size and position of kinetoplast and absence or presence of fl agellum according to Murray, et al., [25].

II. Microheamatocrit centrifugation techniques (Buff y coat technique)
The blood was taken from heparinized vacutainer tube into heparinized capillary tube. Then, the tube was sealed and heparinized capillary tube containing blood was centrifuged for 5minutes at 12,000 revolutions per minute. Then the capillary tube was taken from centrifuge. Trypanosomes were usually found in or just above Buffy coat layer. Therefore, capillary tube was cut using a diamond tipped pen 1mm below the Buffy coat to include the upper most layers of the red blood cells and 3mm above to include the plasma. Contents of the capillary tube was then poured onto a clean slide, and mixed and covered with a 22×22mm cover slip. The preparation was then examined using a bright fi eld microscope with the condenser top out and the diaphragm closed under 40×objective and 10×eyepieces. The species were identifi ed based on the characteristic of the morphology of trypanosomes according to Paris, et al., [26].
Questionnaire survey: To study herd prevalence of camel trypanosomosis data collected should contain all rainy season of the year in the study area, since occurrence of disease is epidemiologically linked with rainy season. However, our study period only come across short rainy season of the area called 'Hagayya' extending from mid-September to mid-November. To fi ll this gap of data accessibility a year back designed semi-structured questionnaire were prepared for 50 camel owners and asked to obtain information on the herd size, seasonal occurrence of the disease in the herds and associated risk factors. Camel diseases of importance, trypanosomosis situation and trypanosomosis control measures were also asked.

Data collection and analysis
Questionnaire data were collected from camel herders at the wells and dwelling area of pastoral association and temporary livestock camps ("Fora"). The data collected during sampling and laboratory results were entered in Microsoft Excel spread sheet. Descriptive statistic was used to estimate the prevalence for camel trypanosomosis in the study area. Risk factors such Citation: Giro
There was signifi cant difference in prevalence of parasite with age (P<0.05) of camels observed. Highest trypanosome infection was recorded in age group of more than 4 years (18.12%) followed by 6.98% and 4.67% in 3-4years and less than 3years of age group respectively ( Table 2).
There was no statistically signifi cant variation (P>0.05) in trypanosomosis prevalence among the fi ve PAs of Arero district (Table 3). In this study, T. evansi infection was found in all the fi ve examined PAs of the district. The prevalence was found to be different among camels from different PAs, The highest prevalence 16(15.24%) of the disease was recorded in Oroto followed by Bobella 10(12.05%), silala 7(9.46%) and Tille 5(7.14%). The lowest prevalence 3(5.66%) was at Didole village (Table 3).  1-20 (Table 5).

Questionnaires survey results
Primary purpose of camel production in study area was mentioned by respondent for Milk production (76.0%) which are the major constraint to camel production in the area.

Discussion
The overall prevalence of camel trypanosomosis in the study area was found to be 10 [36], who reported the prevalence of 3.3% and 4% from parasitological and serological examinations, respectively.   However, the present fi nding was lower than the previous study of Abera, et al., [37] and Bogale, et al., [18], who reported

17.9% and 18.22% prevalence at Sawena district and Delo Mena
District of Bale Zone, Oromia Region, Southwest Ethiopia, respectively. The prevalence in the current study was also lower than the fi ndings by previous workers who reported a prevalence of 21% in eastern Ethiopia [20], 20% in Dire Dawa, southeastern Ethiopia [37], 28% in Kenya [38], 29% in Niger [39] and 33% in Sudan [40]. The possible explanation for the lower prevalence rate detected in this study might be related to distribution, challenge and density of parasite vector is low.
The current study was also conducted during the short rainy season where the distribution of biting fl ies is very low in this season as their reproduction is high during major rainy season.
In general this variation in prevalence of camel trypanosomosis might be due to difference in agro-ecology of the study areas, management system, production system, population density, different sensitivity of different test methods used and new techniques such as PCR. In addition, seasons of the year when the studies were conducted which have a direct effect on the distribution of biting fl ies responsible for the mechanical transmission of T. evansi also cause variation in prevalence [32].
In this study, a signifi cantly (P<0.05) higher prevalence of camel trypanosomosis was noted in adult camels (18.12%), followed by young ones (6.98%) and calf less than 3 years old (4.67%). This result agrees with a previous report from Jijiga, Somali Region, Ethiopian, who reported that in adult camels above 4 years old had a signifi cantly higher prevalence of infection as compared to the young ones below 4years old [34]. The current result is in line with that of Abera, et al., [41], in bale zone in which higher infection rate was recorded in camel above 4 years. Similar suggestion was also given in the study in Saudi Arabia who reported that the younger were less susceptible to infection than adults [42].
The higher prevalence in old camels might be due to their long distance movement in search of water and pasture as a result they were more exposed to biting fl ies and many stress impose them more susceptible to the infection. This idea in line with Bogale, et al., [18], who reported the higher prevalence in old camels might be due to; heavy stress through their use for transportation of goods from one place to another and poor management.
This result in close agreement with the report of Atarhouch, et al., [43], who showed that the infection rate of camel trypanosomes is increased with age up to maximum in the 7-10years old age. However, this result is reverse to the observations of Lemecha, et al., [44], who reported a higher prevalence in young compared to adults by using standard parasitological techniques. The present study was contradicted with that of Pathak and Khanna [45], who reported that all camels were equally susceptible to trypanosome infection regardless of breed and age.
The present study shows that calves were less infected than the other age group. The possible reason why calves were less infected than other age groups might be due to; Owners keep them in the residence area and they do not go to distant areas in searching of water and pasture where the fl y burden is high. Young animals are also bitten less frequently than older ones due to the greater defensive behavior they exhibit making it hard for biting fl ies to feed readily on the former [46]. A previous report from Fantale district southeast Showa zone, Ethiopia is also in agreement with the current fi nding that young calves below one year of age were less infected than other age groups or in some case free of T. evansi infection [32].
One study have demonstrated a greater sensitivity to infection in calves and once infected, poor capacity to control subsequent parasitaemia leading to their rapid mortality hence removing them from the pool of positive animals used in the calculation of prevalence rates [47,48]. This phenomenon might also explain the low prevalence observed in this age category.
In the present study, there was no statistically signifi cant difference observed between sex and the disease (P>0.05). This might be due to all camels were equally susceptible to trypanosome infection regardless of breed and sex [45].
However, the highest prevalence of the disease was recorded in male (11.69%) than female (10.39%). This might be due to the fact that male camel were used for work all the time and travel from one place to another place to provide transportation service more than female camels, so that they have a higher probability of acquiring an infection. Frequent travel could also compromise their immune response to infection due to the stress of fatigue.
The present study is in agreement with the fi nding of Abera, et al., [41], who recorded higher infection rate in male (20.3%) than female (17.3%). Similarly, Bogale, et al., [18], in Delo Mena District, Bale zone also reported on sex related differences in prevalence of camel trypanosomes, that a higher infection was found in males (20.25%) as compared to females (17.72%). However, other studies in Asia have reported sex related differences in prevalence in camels [30], where females (15.68%) were observed to be more susceptible to the disease than males (11.76%) counterparts. The current study was also contradicted with report from the same continent, Pakistan who reported a higher infection was found in females (15.79%) as compared to males (9.84%). This record might be due to stress during pregnancy and lactation, which could decrease resistance in female camel and render them more susceptible to infection [29].
In the present study, there was no statistically signifi cant difference observed between the prevalence of camel trypanosomes infection among the PAs of district (P>0.05).
The prevalence was found to be different among different sites of district; the highest prevalence of the disease was observed in Oroto 16(15.24%), followed by Bobella 10(12.05%) and Silala 7(9.46%) whereas the lowest was recorded in Tille 5(7.14%) and Didole 3(5.66%) during the study period. This might be due to the difference in management system, vector density,  [49], stated that late comers into camel business, such as Borana and Guji have less experience with dromedaries and acquired less adequate traditional knowledge and difference in camel herding strategies that has already been demonstrated to infl uence some production parameters may also result in variations in disease occurrence.
Milk production was mentioned by respondent to be the primary purpose of camel production in the area followed by draft purpose, as wealth indicator and meat production. Magarsa, B. [27], also reported Pastoral communities of Borena lowland produce camels primarily for milk production followed by transport, cash income by sale and meat production. Similarly, Mehari, et al., [50], have described the potentials camel production in Eastern Ethiopia including provision of food, transportation and draught power.
It was evident from this study that all of the herders are aware of camel trypanosomosis which they call 'Dhukkana' in their vernacular. They described the disease accurately and ranked it as a disease of fi rst priority in camels. This shows the camel trypanosomosis is very important disease in the area from the past to nowadays and continues to pose a signifi cant impact on the livelihood of pastoral communities. All of the herder deeply explain the possible further transmission factors of the disease. All of the interviewed herders knew the role of insects (biting fl ies) as mechanical transmitters of trypanosomes which are abundant during rainy seasons. In addition, the informants were able to link increased cases of infection to a build-up of the biting fl y population. It is known that biting fl ies play an important role in the transmission mechanisms of camel trypanosomosis [51,52].
The herders mentioned that camel contract the disease when travel to other place for long distance and get mixed with camels from neighboring herds by the biting fl ies. Van den Bossche and Vale [53], support this idea who reported that management factor and movement patterns of animals may lead to increased risk of developing infection. The herders added that congregation of camel herds around water and in pasture into close proximity facilitated effi cient transmission of the disease by the biting fl y. This idea is supported by Luckins, [54], who reported that local epidemics of infection occur where conditions exist for the spread of infection with T. evansi, such as when many animals are stabled together or closes herded and particularly when the biting fl y population is abundant during the wet season. During this study, all herders were able to mention two or more of the typical clinical signs and symptoms of camel trypanosomosis. The herders recognized camel trypanosomosis through signs of emaciation (80%), abortion (42%), milk reduction (26%), innapetance (24%), urine odour (10%), weakness (8%) and dullness (6.0%). Bogale, et al., [18], who reported that camel trypanosomosis causes anorexia, weakness and emaciation that lead to low milk and meat yield, poor traction power, increased abortion and death, gave similar suggestion. In another study by Catley, et al., [55], report loss of tail hair; was also mentioned by herders (78%) as a sign of camel trypanosomosis.
With regard to their routes of movement, they mentioned that the majority of migrations of owners and their animals are seasonally to southern ward and northern ward of the district. They move to Southern ward of district during dry seasons ("Bonna and Adolessa") and Northern ward during wet seasons ("Haggaya and Ganna"). The reasons for that might be lack of browsing, water and biting insects in certain season and area according to the owners of camels. This movement put their animal on extra risk of contracting the disease from another district. This idea is in line with report of Magarsa, B. [27], Seasonal herd mobility was observed particularly during the dry season for foraging and watering purposes, and to some extent during wet season to avoid disease occurrences. Trypanosomosis was frequently diagnosis in herds that has been moved to other locations. Macpherson, et al., [56], also reported the transhumance by seasonal movement of livestock has profound effect on the epidemiology and spread of this disease in Africa.
With regard to the temporal occurrence of the disease, majority of the respondents (80%) mentioned that the disease mainly occur in major rainy season ("Ganna") this idea in line with report by Gruvels and Beil [57,58], who reported seasonal incidence of disease and Outbreak in chad usually occur during rainy season. The herder added that they relate between seasonal outbreaks of infection and increase in number of insect fl ies responsible for disease transmission during the rainy season. This in line to Surveys in various tropical areas have shown a defi nite correlation between seasonal outbreaks of T. evansi infection and increase in number of fl ies responsible for disease transmission during the rainy season [13]. A small number of the herders reported occurrence of disease during dry season ("Bona") of the area. According to this pastoralists, occurrence of the disease during the dry season was due to camels are usually in a low plane of nutrition and trek for long distances in search of water and pasture. This is likely to stress the animals and subsequently trigger clinical signs of trypanosomes in animals. Evans, et al., [50], have also reported a high prevalence of camel trypanosomosis occurring in the dry season in semi-arid rangelands in Kenya.
Majority (86%) of respondent mentioned they buy drug from market and administer by themselves. (12.0%) of respondents mentioned that not having access to drugs in the study area to control the occurrence of the disease in their herds.

Conclusion and recommendation
The present study results seem to indicate that T. evansi infection was prevalent in the study area. The disease causes a signifi cant impact on the camel production in the study area by affecting health and productivity of camels. In Ethiopia, camel husbandry is the main source of living for millions of pastoralists in the arid and semi-arid zones of Ethiopia.
Camel owners of the study area were familiar with the disease, associated clinical signs, season of occurrence and effect on production due to disease. The most important concern to camel production is widespread diseases, poor veterinary service and lack of availability of drug. In line with the above conclusion, the following recommendations are forwarded: