Hard Ticks of Camel in Southern Zone of Tigray , Northern Ethiopia

This cross-sectional study was carried out in Raya Azebo district with the objective of determining the prevalence and species diversity of hard ticks encountered in camels. During the study period, a total of 384 camels were examined and 96.6% of them were found infested with ticks. A total of 15,723 ticks were collected from half body regions of infected camels during the study period. The average tick burden from half body region of camels was 42.4 ± 19.63. In this study four genera and ten species of hard ticks were identified. The genera identified were Amblyomma (11.11%), Boophilus (1.8%), Hyalomma (23.32%) and Rhipicephalus (61.77%). The tick species identified during the study period were Amblyomma variegatum, Boophilus decolaratus, Amblyomma cohaerence, Rhipicephalus evertsi evertsi, Rhipicephalus pulchelis, Amblyomma gemma, Amblyomma lepidum, Hyalomma rufipes, Hyalomma dromedarii and Hyalomma truncatum at a prevalence of 22.9, 16.7, 23.2, 41.5, 92.7, 7.8, 3.4, 47.4, 42.7 and 8.9%, respectively. Further study and appropriate control measures are recommended to improve the health and productivity of camel.


INTRODUCTION
The camel plays an important role in the culture and agriculture of many countries.It is an important working animal of the arid and semi-arid ecosystem because of its unique adaptive physiological characteristics (Rabana et al., 2011).However, camel production is conversely affectted by the occurrence of various diseases, inadequate veterinary services and feed shortage (Bekele, 2010).Of all, various internal and external parasitic diseases have been reported to be the major problems affecting the health, productivity and performance of camels.Ticks are one of the most important parasites among the factors affecting the health, productivity and performance camels (Anwar and Khan, 1998;Parsani et al., 2008;Bekele, 2010); by transmitting various diseases causing agents, and causing blood loss, irritation, inflammation, hypersensitivity and damage to hide and udder (Wall and Shearer, 2001;Walker et al., 2003).In Ethiopia, ticks are common in all agro-ecological zones of the country (Pegram et al., 1981).The most important tick species reported to infest camel in Ethiopia include Hyalomma species, Amblyomma species, Boophilus species and Rhiciphalus species (Richard, 1979;Melaku and Fisseha, 2001;Lawal et al., 2007;Parsani et al., 2008;Dinka et al., 2010).
Knowing the prevalence and geographical distribution of tick species is important for the control of tick and tick born diseases.Studies conducted in Ethiopia are limited to the Eastern part of the country (Zelalem, 1994;Abebe, 2001;Melaku and Fisseha, 2001;Woldemeskel, 2001;Dinka et al., 2010) and there is limited information in other part of the country.Therefore, this study was conducted to estimate the prevalence and species diversity of ticks in camels in Raya-Azebo district, northern part of Ethiopia.

Study area
The study was conducted in Raya Azebo district, Southern Zone of Tigray Region.Raya Azebo is located at latitude of 12° to 180° North and longitude of 38° to 39°.The average elevation of the district is 1470 to 2370 m above sea level.The mean annual rain fall is 610.5 (351 to 870) mm.The mean minimum and maximum annual temperature for the area are 15 and 30°C, respectively (RAWAO, 2010).

Study type, study animals and sample size determination
A cross-sectional study was undertaken to estimate the prevalence and to identify the species composition of tick in camel.The sample size was determined following the formula described by Thrusfield (1995).By considering the expected prevalence of 50 and 5% absolute precision with 95% confidence level, the sample size was calculated as follows: Where, n = required sample size, Pexp = expected prevalence (50%), d= desired absolute precision (5%), 1.96 = Z-value for the 95% confidence interval.Based on this formula the minimum sample size for the present study was 384 camels.The study camels were selected by simple random sampling method.

Sample collection and identification of tick
First, general physical examination was conducted on each camel.All data regarding the age, sex, body condition and other related information of the animals were recorded appropriately.The age and body condition of camels were determined based on their dentition and hump structure as described previously (Schwartz and Dioli, 1992;CACIA, 1995).After proper restraining, all visible adult ticks were collected from half-body regions of camels (on right side of the study animal) by hand and using good quality steel forceps.The collected adult ticks were kept in a properly labeled plastic containers containing 70% ethanol for further identification.
The collected ticks were identified to their species level at Raya Azebo veterinary clinic and parasitology laboratory of college of Veterinary Medicine in Mekelle University, using stereomicroscope.Sampling and identification of ticks were carried out according to the standard technique recommended by Hoogstraal (1956), Okello-Onen et al. (1999) and Walker et al. (2003).

Data analysis
The data was entered into Microsoft excel spread sheet and coded appropriately.For data analysis, SPSS version 17 was used.In this data analysis, descriptive statistics was used to determine the prevalence of tick infestation in camels.The chi-square test was used to determine the existence of any association between tick distribution and the risk factors like age, body condition score and sex.In all cases, 95% confidence intervals and p < 0.05 were set for significance.
Except for A. variegatum the age of animal had no effect (p > 0.05) on the prevalence of tick species.B. decolaratus, A. cohaerence, A. gemma, H. dromedarii and R. pulchelis infestation had showed statistically significant variation (p < 0.05) between male and female camels.In addition, the body condition of camel had no effect (p > 0.05) on the prevalence of tick species except for H. truncatum (Table 3).

DISCUSSION
The present study assesses the prevalence and species of hard tick infestation encountered on camel in northern This was in accordance with the previous investigators who reported high tick load per camel (Zeleke and Bekele, 2004;Bekele, 2010;Nazifi et al., 2011).These results showed that tick infestations in camel are highly prevalent.R. pulchelis was the most abundant tick species found on 92.7% of the examined camels and constituted 53.7% of the total ticks collected.Zelalem (1994), Abebe (2001), Zeleke and Bekele (2004) and Dinka et al. (2010) (Walker et al., 2003).H. rufipes was the second ranked tick species on camel with a prevalence of 47.4% and constituted 11.2% of the total ticks collected.This result was lower than the finding of Lawal et al. (2007) who reported a prevalence of 22.9% in Nigeria.H. rufipes is widely distributed in the most arid parts of tropical Africa, receiving 250 to 650 mm annual rainfall (Hoogstraal, 1956).In addition, Rhipicephalus evertsi evertsi was also identified at a prevalence of 41.5%.R. evertsi evertsi constituted 8.1% of the total ticks collected.This tick species shows no apparent preference for particular altitude, rainfall zones and seasons (Pegram et al., 1981).
The prevalence of H. dromedarii in this study was 42.7% and constituted 12.8% of the total ticks collected.This result was in agreement with the result of Lawal et al. (2007) who reported a prevalence of 46.9% but higher  (Hoogstraal, 1956;Walker et al., 2003).
In this study, the prevalence of Amblyomma variegatum was 22.9% and constituted 2.4% of the total ticks collected.Zeleke and Bekele (2004) reported A. variegatum from camel at a prevalence of 1.8%.This tick species was also reported by Banaja and Ghandour (1994) and Lawal et al. (2007) in camel from Saudi Arabia and Nigeria, respectivly.Amblyomma gemma was also found at a prevalence of 22.9% in this study.This result was higher than the finding of Zeleke and Bekele (2004) and Dinka et al. (2010) who reported a prevalence of 4.0 and 15.10% in camels, respectively.Additionally, Amblyomma cohaerence and Boophilus decolaratus were encountered on 23.2 and 16.7% of the examined camels, respectively.A. variegatum, A. gemma, A. cohaerence and B. decolaratus were identified from different domestic animals and from different parts of Ethiopia.These tick species are common and widely distributed on livestock in Africa within a wide variety of climates (Morel, 1980;Pegram and Higgins, 1992;Okello-Onen et al., 1999;Walker et al., 2003).Even though their proportions were very low, Hyalomma truncatum and A. lepidum were also detected at a prevalence of 8.9 and 3.4%, respectively.Both H. truncatum and A. lepidum are adapted to dry habitats and occur in arid and semi-arid areas (Walker et al., 2003).
In general, this and other studies showed that ticks are still among the most commonly found ectoparasites of camels worldwide.Further studies should be undertaken in order to understand the distribution pattern of ticks, to estimate the impact of tick infestation on camel production, and to design effective control and prevention strategies.

Table 1 .
The prevalence of tick species of camels in Raya Azebo district.

Table 2 .
The proportion of tick species in Raya Azebo district.

Table 3 .
The distribution of tick species among/between the different sexes, ages and body condition score of camels.