Received Date: January 17, 2017 Accepted Date: February 09, 2017 Published Date:February 11, 2017
Citation: Eticha E, Lemma D, Abera B, Selemon H (2017) Prevalence and Associated Risk Factors to Lice Infestation in Sheep of Arsi High Land, Oromiya Regional State, Ethiopia. J Vet Sci Technol 8: 425. doi: 10.4172/2157-7579.1000425
Copyright: © 2017 Eticha E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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This study was done from November 2011 to March 2012. A total of 384 sheep from Tiyo District of Arsi Zone, around High land area of Asella were selected for the study. A cross sectional study was conducted to determine the prevalence of lice in sheep and to identify major species of lice in the study area. The densities of lice were determined through counting after parting of the fleece/wool at five (5) points on a length of 10 cm in different regions of the body (neck, shoulder, back, rump and flank) on both sides. The overall prevalence of lice infestation was found 53.9% (n=384). From this Damalina ovis takes the highest prevalence in each variable (sex, age, body condition and month) whereas Linognathus ovillus had lower prevalence in each variable. The prevalence of lice for female and male was 53.26% and 56.4%, respectively. Adult and young infestation rate of lice was 51.52% and 57.5%, respectively. Prevalence of lice infestation in good, medium and poor body condition was 36.8% (64), 62.7% (94) and 81.7% (49), respectively. The prevalence of lice in November was 74.44% (94), in January 32.8% (42) and in February 55.5% (71). There is statistically significant difference in the occurrence of lice infestation between body condition scores and months (p<0.05) but there is no statistically significant difference between age and sex (p>0.05). These result shows that lice infestation has a great effect on the skin quality and on the production of meat and milk. From this result it can be concluded that occurrence of lice depends on body condition and climatic factor. Therefore, owners should practice good management system by keeping the hygiene of animal and by avoid mixing of healthy animals from diseased once with the use effective acarcide control.
Asella; Lice; Prevalence; Sheep
In Ethiopia, small ruminants comprise large proportion of livestock resources, constitute about 30% of the total livestock population of the country and are among important contributors to food production in Ethiopia, providing 35% of meat consumption and 14% of milk consumption . And the country is an ideal case for studying livestock diversity in the context of developing regions. It is route of sheep migration from Asia into Africa, has large population  and diverse traditional sheep breeds spread across diverse ecology, communities, and production system. At the national level, sheep/goat account for about 90% of the live animal/meat and 92% of skin and hide export trade value . At the farm level sheep contribute as much as 22-63% to the net cash income derived from livestock production in the croplivestock production system .
Lice are among the major disease of sheep and cause serious economic loss to farmers through mortality, decreased production and reproduction, down grading and rejection of skins which also affect the tanning industries. According to tanneries report, skin diseases due to external parasites cause 35% sheep skin rejection , among highly prevalent and pathogenic ectoparasites of sheep. Both biting and sucking lice affect small ruminants. The important species of lice found in sheep and goats are the genus Damalina and Linognathus and the important species in sheep being L. ovillus (sucking face louse), L. aficanus, L. spedalis (sucking foot louse) and Bovicola ovis (biting louse). In goats L. stenopsis (sucking blue louse), L. africanus, B. caprae (biting louse), B. alimbata and B. crassiceps are reported .
All species cause irritation of the skin, stimulate scratching, rubbing, and licking leading to restlessness, these have great effect on sheep production and skin quality . Accordingly, the enormous economic losses induced by Lice in sheep necessitate detailed investigation on their incidence in order to organize efforts to at least minimize these losses. This study is therefore aimed for assessing the prevalence of lice and determining the magnitude of lice infestation in relation to associated risk factors.
The present study was conducted from November 2011 to March 2012 in Tiyo district of Arsi Zone, around highland area of Asella, capital town of Arsi zone, which is located at 175 km southeast of Addis Ababa, and the altitude and annual rainfall of the area ranges from 502-4130 meters above sea level and 200-400 mm with mean annual temperature of 22.5°C, respectively. It is one of the highly-populated areas in Ethiopia with estimated human population of 2,521,349 and livestock population of cattle-82,190; sheep-51,292; goat-8, 11,479; poultry- 5, 62,915; equine- 22,055 .
Study design and sampling strategies
A cross sectional study was conducted to determine the prevalence of lice in indigenous sheep in the study areas. With the assumption of possible prevalence rate of the disease 50%, absolute desired precision of 5% and confidence level of 95% was considered for estimation prevalence in the simple random sampling according to Thrusfield,  the total sample size was 384 sheep.
The present study involved sheep kept under extensive (mixedcrop livestock production) production system in selected peasant associations of Tiyo district. A total 384 sheep was randomly selected from 19,453 sheep population in the district. The sampling was made by 3 rounds in different months of the study period.
The animals were randomly selected and clinically examined for presence of the ectoparasites. Prior to clinical examination, the sex, ages, body condition scores of the selected animals were recorded. The different age groups such as young and adult have been selected for the present study and the age group was done as per standard method of Hamito . Body condition score of the animals will be considered as poor, medium, and good by modifying the system described by Johns  for sheep. The clinical examination was performed by multiple fleeces parting in the direction opposite that in which hair or wool normally rests and visual inspection and palpation of the skin for parasites on neck, shoulder, wither, flank and ramps are sites of concern. In each of the mentioned body parts both on the either sides /left and right/ a place 10 cm long is parted for the presence of lice and if found in all or one of the 10 cm long place. Those sheep found infested by parasites was considered positive. The type of parasites was identified on the basis of their morphological structure as described in Wall and Shearer .
Specimen collection and examination
Those detected lice that are unidentified during clinical examination was collected by forceps/hand picking, with hairs from their attachment site, put into a clean separate container(universal bottles), labeled and kept preserved with 70% ethyl alcohol before transportation to Asella regional veterinary laboratory for detailed laboratory examination as described by Urquhart et al. . Then the collected ectoparasites was examined by stereomicroscope and identification was performed according to the identification key given by wall and shearer .
Data management and analysis
The data was subjected for statistical analysis by entry in to Microsoft Excel spread sheet and descriptive statistics like prevalence and analytical statistics such as chi- square (χ2) was conducted by using SPSS 17.0 for determining the significance of association between age groups, sex, body condition scores, and month with lice infestation. For the purpose of this study, 95% confidence level and P<0.05 was used for significance.
Overall prevalence of lice
Out of the total sheep population examined for lice infestation, 53.9% (207) sheep were infested with lice. The major species of lice were D. ovis and L. ovillus species, from this the most prevalent species was D. ovis with an overall prevalence of 86.9% (180) while L. ovillus species was only 1.9% (4) and mixed lice infestation was 11.6% (23). The commonest site of lice attachment was the skin of neck, shoulder, flank and rump.
Prevalence of lice in sheep by different age groups
Out of the total population of sheep examined for lice infestation 60.2% (231) sheep was adult and 39.8% (153) was young. The overall prevalence of lice infestation in adult was 51.52% (119) where as in young it was 57.5% (88) of this the most prevalent lice species were D. ovis with the prevalence of 89.1%(106), where as L. ovillus species have 0 prevalence and mixed lice infestation was 10.9% (13) in adult and in case of young (lamb) D. ovis 84.09% (74), L. ovillus species 4.54%(4) and mixed lice infestation 11.36%(10) (Table 1). In both age groups there is no statistically significant difference (p=0.248)
|L. ovillus||0% (0)||4.54%(4)|
|Mixed lice||10.9% (13)||11.36%(10)|
For Total infestation Chi square (df=1)=1.334, P=0.248
Table 1: Prevalence of lice in sheep by age wise.
Prevalence of lice in sheep by different sex group
Out of the total population of sheep examined for lice infestation 79.7% (306) sheep were female and 20.3% (78) are male. The overall prevalence of lice in female is 53.26% (163) and in male are 56.4% (44). The most prevalent species is D. ovis with the prevalence of 87.12% (142), whereas L. ovillus 1.23% (2) and mixed 11.66% (19) in female sheep. In male sheep the prevalence of D. ovis was 100% (44), L. ovillus 9.1% (4) and mixed infection is 9.1% (4) (Table 2). In both sex groups there is no statistically significant difference (p= 0.619).
|D. ovis||87.12% (142)||100% (44)|
|L. ovillus||1.23% (2)||9.1% (4)|
|Mixed lice||19(11.66%)||9.1% (4)|
|Over all lice||53.26% (163)||56.4% (44)|
For Total infestation Chi square (df=1)=0.247, P=0.619
Table 2: Prevalence of lice in sheep by sex wise.
Prevalence of lice infestation in sheep by different body condition
From the total population of sheep examined for lice infestation 45.3% (174) sheep have good body condition, 39.1% (150) sheep have medium body condition and 15.6% (60) sheep have poor body condition. The overall prevalence lice infestation of good, medium and poor body conditions was 36.8% (64), 62.7% (94) and 81.7% (49), respectively. The most prevalent species was D. ovis with the prevalence of 90.6% (58), L. ovillus 3.13% (2) and mixed lice infestation 6.25% (4) in good body conditioned animal. In medium body condition animal the prevalence of D. ovis was 84.04% (79), L. ovillus 1.064% (1) and mixed lice infestation 14.89% (14). In poor body condition prevalence of D. ovis was 87.76% (43), L. ovillus 2.04% (1) and mixed lice infestation 10.2% (5) (Table 3). There is statistically significant difference in the occurrence of lice infestation between body condition sores (p=0.000).
|L. ovillus||2.04% (1)||1.064% (1)||90.6% (58)|
|D. ovis||43(87.76%)||84.04% (79)||36.8% (64)|
|Mixed lice||10.2% (5)||14.89% (14).||3.13% (2)|
|Overall lice||81.67% (49)||62.7% (94)||6.25% (4)|
For Total infestation Chi square (df=6)=43.778, P=0.000
Table 3: Prevalence of lice in body condition.
Prevalence of lice infestation in sheep by month wise
Out of the total population of sheep examined for lice infestation equal numbers of sheep were taken in each month (i.e., 33.3% (128), in November, 33.3% (128) in January and 33.3% (128) in February). Out of this the overall prevalence of lice in November was 73.44% (94), in January 32.8% (42) and in February 55.5% (71). Out of this prevalence of D. ovis was found 85(90.42%), L. ovillus 0 prevalence and mixed lice infestation 9.6% (9) in November. In January the prevalence of D. ovis was 83.33% (35), L. ovillus 0 prevalence and mixed lice infestation 16.66% (7). In February prevalence of D. ovis was 84.5% (60), L. ovillus 4.22% (3) and 15.5% (11) and mixed lice infestation 9.86% (7) (Table 4). There is statistically significant difference in between the three months (p=0.000).
|D. ovis||90.42% (85)||83.33% (35)||84.5% (60)|
|L. ovillus||0%||0%||4.22% (3)|
|Mixed lice||9.6% (9)||16.66% (7)||15.5% (11)|
|Overall lice||73.44% (94)||32.8% (42)||55.5% (71)|
For Total infestation Chi square (df=2) 42.698, P=0.000
Table 4: Prevalence of lice by month wise.
Prevalence of lice in sheep by severity
Out of the total population of sheep infected with lice 41.06% (85) sheep were severely infected, 101(48.79%) sheep with moderate infection and 10.14% (21) were with slight infestation. The most prevalent species was D. ovis with the prevalence of 97.65% (83), 79.2% (80) and 85.71% (18) in severe, moderate and slight infestation respectively. While for L. ovillus 1% (1) was slight infestation and 14.29% (3) was moderate infestation. In mixed lice infestation 2.35% (2) was for severe infestation and 20.79% (21) for moderate infestation (Table 5).
|D. ovis||97.65% (83)||79.2% (80)||85.71% (18)|
|L. ovillus||0%||3(14.29%)||1% (1)|
|Mixed lice||2.35% (2)||20.79% (21)||0%|
|Overall lice||41.06% (85)||48.79% (101)||10.14% (21)|
Table 5: Prevalence of Lice by Severity.
The high prevalence of lice was 53.9%, recorded in the study, which is suggestive of the importance of the parasite in sheep population of the study area. Poor management and poor level of awareness of sheep owners on the effect of ectoparasites particularly lice infestation are believed to have contributed to wide spread occurrence of the parasites. D. ovisis the most prevalent lice species recorded with a prevalence of 86.9%, from the 207 sheep infected with lice infestation where as L. ovillus species and mixed lice infestation were 1.9% and 11.6% respectively.
The overall prevalence obtained in this study is higher than observations made in North western Amhara Region  which is 30.9% for D. ovis, by Tadesse et al.  22.28% for B. ovis in around Kombolcha and by Sertse  25.7% in Amhara region. But the present findings indicates lower prevalence than prevalence of 63.5% as reported in Amhara National Regional State  and by Yacob etal.  in Southern Ethiopia, Sodo, and in the Zone of this study area, Arsi, which was 75.5%. Such difference in prevalence with the above observations may arise from differences in agro climate, management, health care of animal and the sensitivity of the diagnostic method used to reveal ectoparasites. Similarly, lice infestation was greater in winter and spring similar to the findings of Colwel et al. .
In addition to skin damage, lice infestation also has a significant effect on production and productivity of animals because the presence of lice interferes with nutrition of animal. Due to itching and scratching the animal spend more time by grooming on fixed objects rather than taking feed which result in decreased body Condition. Body condition has also contribution for the occurrence of lice infestation because there is also evidence that immune response may be involved in regulating louse numbers and may underlie differences amongst sheep in susceptibility to lice [19,20]. Impaired immune response may explain the greater susceptibility to lice of animals in poor condition or under stress.
In the present study sex and age are not statistically significant in the occurrence of lice infestation but in male animal the prevalence of lice is slightly higher than female animal and in young the prevalence of lice infestation is higher than in adults this is because the lambs doesn’t mixed with ewes therefore transmission from ewe to lamb doesn’t occur.
The other factor for the occurrence of lice is climatic condition. In this study the occurrence of lice is higher in November than February and January, which shows infestation of lice is high in cooler time. According to Wilkinson et al. ; Niven and Pritchard  lice infestation is very high in spring time in European countries where the temperature is low during that time.
Considering the importance of skin and hides as a main source of foreign currency to the country, the prevailing ecto parasites mainly in different sheep reared in Arsi zone requires attention in order to minimize the spread of infestation and increase income earnings of farmers and small scale holders whose livelihood is dependent on their animals.
Lice infestation is among the major causes of sheep production constraints and quality deteriorations of exported skin in Ethiopia. Lice are easily overlooked because of their small size but they have the capacity to multiply very fast before being discovered. In this study the overall prevalence of lice infestation was very high (86.9%), this can be resulting in high economic losses through decreased production of meat and milk due to interference with nutrition and skin damages. Lice have a significant effect on body condition. Whereas sex and age of the host animals were not determinant factors for the prevalence variation. Therefore, based on the above points the following recommendations are forwarded: The effect of lice on production, productivity and skin quality is not appreciated by farmers. Therefore farmers should have enough awareness and effective extension programs that raise public awareness on effect of lice, reducing the prevalence of Lice mainly relies on treatment of affected animals with appropriate acaricides and improving the management system and detailed study on economic losses associated with lice infestation and investigation of other causes of skin downgrading and rejection should be conducted.
Authors are grateful for the technical and material support of the staffs of Asella regional veterinary laboratory.