A cross-sectional survey was carried out at Ethiopian Health and Nutrition Research Institute (EHNRI), Addis Ababa, from November 2010 to March 2011 to assess the occurrence and its economic impact of Coenurus cerebralis in sheep. Of a total 445 sheep heads examined, 21(4.7%) were found to be affected by coenurosisis. The prevalence of Coenurus cerbralis was 2.7% and 5.1% in males and females sheep, respectively, however, their difference was not statistically significant (p>0.05). Postmortem examination had showed that Coenurus cerebralis occurred with a range of 1 to 5 cysts in each animal. One cyst occurred most frequently ( 61.9% ) followed by 3, 4, and 5 cysts. The great majority of the cysts (94.4%) were located in the cerebral hemisphere where as 5.4% of cysts were localized on both sides of the middle cerebellar hemisphere. Out of 21 infected brains, 15 (71.4 %) and 6 (28.6%) were trimmed and rejected, respectively. From the total of 6 rejected (total condemned) brain, all of the 6 (100.0%) brains had deep lesions. Total annual financial loss due to brain/animal condemnation was estimated at 8330 Ethiopian Birr (490 US$). Based on this survey, it is concluded that coenurosis is one of the most important livestock parasitic diseases especially in sheep in Ethiopia which results great economic loss at national level and therefore, appropriate control measure should be taken.
Sheep are raised in different agro-ecological zones of Ethiopia. Their distribution however, is determined by ecological factors and density of human population. Sheep play significant role in the national economy. As a whole livestock and livestock product sales provide 87% of total annual farm cash income, of which 40% consisted of sales from sheep (FAO, 1990). Diseases have a great socio-economic impact on sheep production in Ethiopia, according for mortalities ranging from 30% in the lambs to 20% in adult sheep (MOA, 1985).
Cestodes of the family Taenidae, for which the dog is the final host, infect a wide range of intermediate host species where they cause echinococcos / hydatidosis, cysticercosis or coenurosis (Pal, 2007). Infections with larval stages of some species of Taenia have great veterinary importance due to economic loss from condemnation of infected offal or meat. Among parasitic diseases of sheep, coenurosis causes great economic losses in sheep production.
Coenurosis is a disease caused by invasion of the larval stage of Taenia multiceps in the central nervous system (brain and spinal cord) of sheep, goats, and rarely humans. The adult tape worm, Taenia multiceps, occurs in the small intestine of the dogs and wild canides, where as the larval stages, Coenurus cerbralis, are normally found in the brain or spinal cord of sheep and goats. The larval form may rarely infect man, where it causes neurosis on accidental ingestion of parasite egg in the faeces of dogs (Soulsby, 1982).
In Ethiopia, there is a paucity of information on comprehensive study on this disease in sheep. Therefore, present investigation focuses on the prevalence and economic impact of Coenurus cerebralis infection in sheep.
The study was conducted on experimental sheep flocks purchased for rabies vaccine production at Ethiopian Health and Nutrition Research (EHNRI) which is located in Addis Ababa, Ethiop
A cross sectional study was carried out to determine the prevalence and economic significance of coenurosis in sheep by postmortem examination and a thirteen years case record book was taken as part of the attempt to figure out the complimentary information on the disease.
To determine the sample size, a prevalence rate of 50% was taken into consideration since there was no research work done on prevalence of Coenurus cerbralis in sheep at the study area (EHNRI). The required sample size for the study was determined by the formula given in (Thrusfield, 2005) with 95% confidence interval at 5% desired precision.
Postmortem examination were conducted on all the sampled sheep’s brain using the method described by Soulsby, 1982 and Achenef et al., 1999.
The brain was exposed for examination of gross pathological lesions, record cyst locations and numbers in order to pass judgement on infected brain. The brains condemned during postmortem examination as unfit for vaccine production due to Ccoenurus cerebralis infection were registered to determine economic loss during the study period at the institute.
The retrospective study was made by analyzing records of case books from rejected brain records on postmortem findings of the institute between 1990 and 2002 E.C which was complied by laboratory technicians in the vaccine production department.
Total financial loss was estimated based on coenurosis that results total condemnation of the brain (animal rejection) in EHNRI during the study period and retrospective data of the institute.
Therefore, the total annual direct financial loss due to brain (animal) condemnation was then computed mathematically by adopting the formula of Ogunrinade and Ogunrinade (1980).
EL =Σ Srx * Coy * Roz
EL- estimated annual economic loss due to brain/animal condemnation from
international or domestic market.
Srx – Annual sheep slaughter rate of the institute.
Coy- Average cost of each sheep brain/carcass in the institute.
Roz – Condemnation rates of sheep brain/carcass (from 13 years of record).
Data obtained from postmortem findings and retrospective analysis were entered in MS Excel work sheet and analyzed using SPSS version 16.0 for windows software. Simple descriptive statistics were used to analyze retrospective data, number of cyst and its range. Chi-square test was applied to compare the infection rate with regard to sex groups, whereas Kruskal-wallis test were used to analyze prevalence between months of the study period as well as judgment made on brain based on its lesion. A 95% confidence interval and 5% absolute precision was used to determine whether there was significance difference between measured parameters.
Out of 445 sheep’s brain examined, 21(4.7%) were found to be positive for cerebral coenurosis. Of a total of 372 females and 73 males, 19 (5.1%) and 2 (2.7%) animals were found to be infected with Coenurus cerebralis, however, there was no significant variation on prevalence of the sex groups (Table 1). Range of cyst found was 1-5 cysts per infected animal and from the total of 21 positive cases, 13 (61.9%), 4 (19.0%), 2(9.5), 1(4.8%) and1(4.8%) were found with one, two, three, four and five number of cysts, respectively (Table 2).
Table 1. Prevalence of Coenurus cerebralis within sex groups of sheep.
|Sex groups||Total No of sample||No of Positive (%)||χ2||p-value|
Table 2. Prevalence of Coenurus cerebralis infection between sex and number of cyst.
|Sex group||Total sample||Total No positive (%)||No. of cysts per brain No. (%)|
The overall prevalence of Coenurus cerebralis among the different period of study were recorded as 6 (6.7%), 1(1.3%), 8 (5.1%), 5 (5.6%) and 1 (3.4%) in November, December, January, February and March, respectively (Table 3).
Table 3. Prevalence of Coenurus cerebralis by month in sheep.
|Month||No of examined||Total No positive (%)||No. of Cyst/s per brain (%)||χ2||P-value|
Of a total of 36 cysts recovered, 34 cysts were located in the cerebral hemisphere; specifically 50 % of them were localized on right side of the cerebrum and the rest 50% on the left side. However, only 2 ( 5.6 %) were found in the cerebellum. Among the total 17 cysts in the right
Table 4. Location of Coenurus cerebralis in different parts of brain of sheep
|Brain part||No. of cysts on specific part/
Total no. of cysts recovered
cerebrum, 5 (29.4%), 9 (53.0%), 3 (17.6%) were localized the front, middle and hind parts of cerebrum, respectively. Similarly, among the total of 17 cysts in the left cerebrum, 5 (29.4%), 8 (47.1%), 4 (23.5%) were located in the front, middle and hind parts of cerebrum , respectively. The rest 2 (5.6%) cysts were found in the cerebellar hemisphere at both right and left middle parts of the cerebellum (Table 4).
From the total of 21 infected brains, 15 (71.4 %) and 6 (28.6%) were trimmed and rejected, respectively. Of a total of 15 trimmed cases, 9 (60.0%), 5 (33.3%) and 1 (6.7%) cysts had superficial, medium and deep lesion on the brain, respectively. Surprisingly, from the total of 6 rejected (total condemned) brain, all of them 6 (100.0%), had deep lesions on the brain (Table 5).
Table 5. Judgments based on degree of infected brain lesions.
|Brain lesion||Judgments on brain||Total||χ2||P-value|
|Trimmed (%)||Rejected (%)|
The difference between the two judgments on the brain was varied significantly (p< 0.05). In fact, in the research institute, the trimmed brains were passed for use in vaccine production.
Table 6. Record of sheep slaughtered and infested with Coenurus cerebralis at EHNRI for 13 years.
|S. No.||Year (EC.)||Total no. of sheep
|No. of sheep infested||Infestation (%) with Coenurus cerebralis|
E.C. = Ethiopian calendar ( ) = International year
A retrospective analysis of a total of 10,760 slaughtered sheep at EHNRI for the last 13 years, 693 cases were found to be infested with Coenurus cerebralis. Therefore, the average infection rate for the last 13 years was 6.4% which ranged from 3.41% to 8.91% (Table 6).
Total economic loss due to coenurosis was estimated based on data recorded by the department of vaccine production and retrospective bases of 13 years consecutive records at the institute. Accordingly, the retail mean average price of single sheep/brain in Ethiopian Health and Nutrition Research Institute was 157.00 ETB and recorded retrospective data for the last thirteen years was used to analyze the data. Based on these data, average number of sheep slaughtered per annum and percentage of brain/animal condemnation per annum were 829 and 6.44%, respectively.
Therefore, based on above information, total financial losses due to coenurosis were calculated by using the formula indicated under study design:
EL =Σ Srx * Coy * Roz = 829 *157 *6.4% = 8330 ETB (490 US$)
Coenurosis is endemic in Ethiopia, especially in the highland sheep where 75% of the population is found. The presence of freely roaming dogs on grazing land greatly contributes to the existence of disease. Dogs are routinely fed on offal including sheep heads and are not dewormed and hence, maintaining the cycle of Coenurus cerebralis- Taenia multiceps (Achenef et al., 1999).
According to the findings of this survey , an overall prevalence of coenurosis was recorded 4.7%. This observation is in agreement with a retrospective analysis result (4.5%) at ILRI Debre Berhan Station, Ethiopia and higher than the prevalence in apparently healthy animals (2.7%) as described by Achenef et al.,(1999). But it was very lower than (15.5%) than the results of Gicik et al., (2007) in Turkey which probably may be due to different climatic, geographical and social conditions. Of a total of 372 females and 73 males sheep, 19 (5.1%) and 2 (2.7%) animals were infected with Coenurus cerebralis, respectively , however, no significant variation was observed between sexes groups.
From the total 21 positive cases, 13 (61.9%), 4 (19.0%), 2(9.5), 1 (4.8%) and 1 (4.8%) were found with one, two, three, four and five number of cysts, respectively. This result is in agreement with Achenef et al., (1999), who mentioned that most cases (83%) contain only one cyst.
Even though, monthly prevalence differences of coenurosis was not statistically significant, Coenurus cerbralis prevalence was found to be higher in November (6.7%) and lower in December (1.3%). Nevertheless, it was a bit lower than Gicik et al., 2007 report in Turkey which was 16.6% and 23.3% in their respective months. This difference could be attributed by different climatic and geographical condition.
The cyst may be localized in any part of the brain, more commonly in the cerebral hemisphere (Skerritt and Stallbaumer, 1984). In the present study, majority of the cysts 34 (94.4%) were located in the cerebral hemispheres (50% in the left and 50% in the right sides of cerebrum) and the rest 2 (5.4%) cysts were localized on both sides of the middle cerebellar hemisphere. This result was almost comparable with the results found by Achenef et al., (1999) who recorded 96% in the cerebrum and 4% in cerebellum and also with report of Gicik et al., (2007) where 96.7% were present in cerebrum and 3.3% in cerebellum. The higher percentage of localization of cysts in the cerebral hemisphere could probably be explained by the fact that as a consequence of its higher biomass with respect to other part of brain, particularly the median fissure.
Regarding judgments from the total of 21 infected brains, 15 (71.4 %) and 6 (28.6%) were trimmed and rejected, respectively. From the total of 6 rejected (total condemned) brain, all of them 6 (100.0%), had deep lesions on the brain. The difference between the two judgments on the brain varied significantly (p< 0.05). Ironically, the trimmed brain had been used for vaccine production, however, total brain rejection of the infected sheep had great economic impact on vaccine production in the institute.
According to retrospective data analysis, of a total of 10,760 slaughtered sheep at EHNRI for the last 13 years, 693 cases were found to be infested with Coenurus cerebralis, therefore, the average infection rate for the last 13 years was 6.4% which ranged from 3.4% to 8.9%. There were no enough information regarding to location and number of cysts in the institute record book except record on condemnation of the infested brain of sheep. It is pertinent to mention that coenurosis is one of the neglected diseases in our country in spite of its impact on production as well as on the economy.
The annual estimated financial loss in the present study need to be cautiously interpreted as it would be affected by factors which are dynamic and change over time due to market price of sheep as condemnation of the brain means condemnation of the animal, prevalence of disease and number of animals slaughtered every year which can change the amount of financial loss from year to year. Financial loss analysis due to coenurosis in sheep was done based on number of brain/animal condemned per annum and its retail price in Ethiopian Health and Nutrition Research Institute based on the retrospective data collected from postmortem data record of the institute. Based on the information, estimated financial loss due to coenurosis in sheep during the study period was 8330 Birr (490US$) per annum. Financial loss analysis reported by Ejeta et al., (2008) mentioned that coenurosis in small ruminants is a major cause for condemnation of brain (85.7%) in Ethiopia from apparently healthy slaughtered sheep and goat.
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