| Livestock Research for Rural Development 28 (9) 2016 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
The study was carried out to determine the prevalence, the association of selected risk factors and direct related economic loss of small ruminant fasciolosis from animals slaughtered in an export abattoir. Anti-mortem and post mortem examination of liver were made from 768 animals (384 sheep and 384 goats). Livers were examined both visually and clinically.
The overall prevalence of fasciolosis was 8.1% that accounted for 11.9% for sheep and 4.2% for goats. Both species of Fasciola were observed with a higher rate of Fasciola hepatica. Species, body condition and age of the animal are the animal factors associated with fasciolosis. Altitude for the origin of animals and month of the study were also environmental related factors. Adult sheep with a thin body from highlands of Ethiopia were highly infected by fasciolosis. The severity of infection and damage to the liver for infected animals is slight: however, it results total condemnation of the liver. Based on the current study, the economic loss of the abattoir due to total condemnation of livers due to fasciolosis is $ 9720. Thus, fasciolosis still remained as major parasitic disease that incurred great economic loss of the country.
Keywords: economic loss, faciola, factors, prevalence
In Ethiopia, small ruminants have been used either for local meat consumption as well as source of foreign currency by exporting animal and animal products. However, the resource associated with the small ruminants production are not fully exploited due to several factors including occurrence of recurrent drought, infrastructures problem, rampant animal diseases, poor nutrition, poor husbandry practices, shortage of trained man power and lack of policies for disease control and prevention (International Livestock Research Institute 2009). Disease due to parasitic infections has a great impact on worldwide economy by impeding the productivity of the animal especially in developing countries. Among several parasitic infections, fasciolosis associated to both due to Fasciola hepatica and Fasciola gigantica is known to have significant economic impact. In Europe, Americas and Oceania, only Fasciola hepatica is of concern, but the distributions of both species overlap in many areas of Africa and Asia (Henok and Mekonnen 2011). The annual worldwide loss due to fasciolosis is estimated to be above $3.2 billion. In 2007, fasciolosis was recognized as an emerging human disease where by 2.4 million people had infection and 180 million people at risk of infection (WHO, 2007). In Ethiopia, Faciola hepatica and Faciola gigantica infections has been reported from areas 1800m above sea level and 1200m below sea level, respectively. The species distribution difference across altitudes has been attributed to variations in the climatic and ecological conditions such as rainfall, altitude, and temperature and livestock management system (Gatenby 1991). In between these altitude limits, both species coexists where ecology is conducive for both snail hosts, and mixed infections prevail (Khaled 2010). Different prevailing situation and problems due to fasciolosis were mentioned in previous studies; however, there is paucity of well-documented information on the occurrence of fasciolosis in small ruminants. In addition, there is a gap for many potential area of the country. Therefore, the objectives of this study were to determine the prevalence and association of selected risk factors of small ruminant fasciolosis and to estimate the magnitude of economic loss due to condemnation of liver.
The study was conducted at privately owned export abattoir namely Hashim Nur’s Ethiopian Livestock and Meat Export abattoir (HELMEX) located in Bishoftu, East Shoa zone, Oromia State, central Ethiopia from November 2013 to April 2014.The abattoir has been engaged in export of mutton, lamb and goat meat to Middle East countries.
Samples were collected based on simple random sampling technique. The size of the sample was calculated based on the formula of Thrustfield (1995) with 95% confidence interval, 5% absolute precision and expected prevalence of 21.3% which was reported by Yemisrach et al (2012) from the same abattoir. Accordingly,
n= 1.962Pexp (1-Pexp)/d2
Where,
Pexp = expected prevalence;
d= absolute precision;
n =sample size.
Based on calculation, the sample size was 258 (for each species). However, for precision, the sample size was increased to 384 for each species.
Small ruminants have been brought from seven areas of Ethiopia to abattoir for the purpose of slaughtering. Study animals were selected on multistage strategic sampling. First animals were grouped based on their species. Then, animals were grouped based on their area (origin of animal) followed by age of the animal. Selection of animals from each age group was done proportional to the number of animals brought to slaughter house during study period. Finally from animals’ grouped based on their age, each study animal was selected randomly. Thus, based from each area 56 adult and 54 young animals was selected based on multistage sampling. The areas where animals were brought for slaughter (that considered as origin of animal’s here after) were Afar, Arsi, Awash, Bale, Borena, Harar and Wolayita and based on their altitude they were grouped either to highland or lowland areas. The geographical characteristics of the study areas are shown in table (1). According to Gatenby (1991) and Steele (1996), animals were also grouped in to young and adult based on their age (young ≤1.25 years and adult >1.25 years). Body condition scoring was made based on a method described by Thompson and Meyer (1994).
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Table 1. Altitudinal classification of study areas |
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Altitude (meters |
Mean annual |
Classification |
Origin of
|
|
≥1500 |
≤20 |
Highland |
Arsi, Bale, Harar and Wolayita |
|
<1500 |
>20 |
lowland |
Awash, Borena and Afar |
|
Source: Mesfin (1972). |
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Anti-mortem examination was made for all study animals based on the protocol used by the slaughter house. Animals were thoroughly examined during slaughtering, skinning and evisceration for any pathological conditions. Then the livers were put in the plastic bag and had given identification serial numbers that coincides with the identification number given in anti-mortem inspection. Postmortem examination of the liver was done based on routine procedures indicated by Urquhart et al (1996) which include visual inspection, palpation and multiple incision following the bile duct.
Size, shape and color were the morphological features used during identification of Fasciola species. The fully matured Fasciola hepatica in the bile ducts had leaf shape, gray brown color and around 3.5 cm length and 1cm width. In addition, the anterior end was conical and marked off by distinct shoulder from the body. The fully matured Fasciola gigantica was larger than Fasciola hepatica and reached up to 7.5 cm length and had leaf shape. The conical anterior end was very short and the shoulders characteristics were barely perceptible. Then, based on Urquhart et al (1996), infections were classified into Fasciola hepatica, Fasciola gigantica, mixed or juvenile infection.
Retrospective data were collected from data records to determine the annual slaughtering rate of the abattoir. To determine the cost of a liver, a survey was done for the price of liver from butchers, consumers and slaughter houses and the average cost was calculated.
The generated data was recorded in the Microsoft excel 2010 program then exported to SPSS version 20 for analysis. Descriptive statistics was used to determine the level of liver condemnation rates. Pearson’s Chi-square (χ2) was used to determine the statistical association between infection rates. Species, age, body condition, altitude and month were the risk factors considered during data analysis. A statistically significant association between variables was considered to exist if the calculated p-value was<0.05 with 95% confidence level
The economic loss was assessed for condemned livers. Analysis was done based on annual slaughter capacity of the abattoir, rejection rates of livers due to fasciolosis and average market prices of liver in local or international market. Accordingly, the formula set by Ogunrinde (1980) was used.
EL=∑Srx*Coy * Roz
Where,
EL=Estimated Annual Economic Loss due to organ condemnation
Srx=Annual sheep/goats slaughter rate of the abattoir
Coy=Average cost of liver
Roz=Average rejection rate of liver due to fasciolosis
Out of 768 total examined livers, 62(8.1%) livers had had liver fluke parasites. Thus, based on liver examination, the overall prevalence faciolasis of small ruminants was 8.1%. The prevalence of fasciolosis was significantly higher in sheep 46/384(11.9%) than in goats 16/384(4.2%) (p=0.000). From 62 positive livers during examination, 48.4% had Fasciola hepatica, 38.7% had Fasciola gigantica, 9.7% had mixed infection and 3.2% had juvenile infection. The association of selected risk factors with fasciola infection is shown in Table 2. Altitude, body condition score, month and age of the animal were strongly associated with fasciolosis.
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Table 2. Factors associated with small ruminant fasciolosis at HELMEX abattoir |
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|
Variables |
No. Examined |
No. Infected |
Percentage |
χ2 |
p |
|
Months |
|||||
|
December |
255 |
26 |
10.2 |
13.22 |
0.004 |
|
January |
223 |
10 |
4.5 |
||
|
February |
160 |
8 |
5.0 |
||
|
March |
130 |
18 |
13.8 |
||
|
Age |
|||||
|
Young |
376 |
18 |
4.8 |
10.72 |
0.001 |
|
Adult |
392 |
44 |
11.2 |
||
|
Altitude |
|||||
|
Highland |
414 |
43 |
10.4 |
17.34 |
0.000 |
|
Lowland |
354 |
19 |
5.4 |
||
|
Body condition |
|||||
|
Thin |
103 |
29 |
28.2 |
64.65 |
0.000 |
|
Average |
363 |
18 |
5.0 |
||
|
Fat |
302 |
15 |
5.0 |
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Depending on the severity of liver lesions and intensity of fluke infection (worm load), the affected liver was grouped into three categories as described by Ogunrinade and Ogunrinade (1980). Thus, from 62 affected livers, 25(40.3%) livers were slightly damaged, 20(32.3%) were moderately damaged and 17(27.4%) were severely damaged. Based on the principle of this abattoir, livers having any level of fluke infection will be totally condemned.
The direct economic loss due to condemnation of liver as the result of faciolosis was done for study animals and annual slaughter rate. The total loss due to condemnation of liver from studied animals was calculated based on the formula indicated in material and method. The number of studied animal was 768 small ruminants and 8.1% of livers were rejected due to fasciolosis. Thus, the loss was calculated based on the product of number of slaughtered animals (768 heads), average cost of liver ($ 0.75) × rejection rate due to fasciolosis (8.1%) that is (768 heads*$0.75* 0.081= $46.66).
It is known that the prevalence of fasciolosis in small ruminants is significantly different across months of the year as seen in the current study. However, according to Ogunrinade and Ogunrinade (1980), annual economic loss can be based on the annual slaughtering rate of the abattoir and rejection rates of the liver. Thus, from data records the annual slaughter rate of the abattoir was 200,000 small ruminants, the average rejection rate of liver due to fasciolosis based on the current study was 8.1% and the average cost of the liver was $0.75. Thus, the direct economic loss was the product of slaughter rate of the abattoir (200,000 heads), average cost of liver ($ 0.75) × rejection rate due to fasciolosis (8.1%) that is (200000*$0.75* 0.081= $9720).
The overall prevalence of fasciolosis was 8.1% and it was 11.9% and 4.2% for sheep and goat, respectively. Previous studies from different parts of Ethiopia showed higher prevalence of ovine fasciolosis such as 35% in Woliso (Rahmeto 1992), 73% in western Shoa (Yadeta 1994), 30% in Ziway (Adem 1994), 53.3% in Eastern Gojam (Wassie 1995), 32.7% in Assela (Dinka 1996), 21.3% in Bishoftu (Melkam 2008) and 16.9% in Bahir Dar (Ayalew and Endalkachew 2013). This wide gap may be due to the season of the study, difference in ecology of the study area, management system of animals, sample size differences, actions that were taken due to previous reports, the shift of most of marshy or waterlogged areas for crop production and improvement in veterinary service. No previous work is done and data are not available on the prevalence of goat fasciolosis in Ethiopia.
Significant variation (p<0.05) was observed on the occurrence of fasciolosis across the species of small ruminants and higher prevalence was observed in sheep than goats. This difference is similar to most previous studies in different countries which is likely to be associated with the feeding behavior. Marshy areas are favorable for reproduction and growth of snail which is an intermediate host for Fasciola. Marshy areas are sweaty for grazing rather than browsing. Usually goats do not graze as indicated by Dinka (1996), goats are natural browsers and they tend to graze in very rare cases that decreases the probability of picking the metacercaria along with the grass (Dinka 1996). Difference in prevalence as well as severityof the disease syndrome are evident in various geographical regions depending on the local climatic conditions, availability of permanent water (marshy area) and system of management (Urquhart et al 1996).
Variation (p<0.05) also observed between altitudes. Higher prevalence was observed in highlands when compared to lowlands. This variation may be due to the local climatic factors, the density of animal population, ecological niches (temperature, moisture, humidity, soil and marshy area) favoring the development of intermediate hosts and the transmission of the disease (Urquhart et al 1996). Schillhorn Van Veen (1981) believed that dried field condition accounted for fewer occurrences of fasciolosis in lowland areas; however, flood plain from highlands to lowlands in the grazing circuits of the animal also increases the risk of acquisition of an infection. Thus, the existence of relatively many low-lying marshy and water lodged plains in highland areas available may be associated to the higher prevalence of fasciolosis in sheep during this study. The lowest prevalence of the disease in lowlands may be explained in terms of a function of a limited animal water contact which resulted from unavailability of enough pasture land and water (Dinka 1996).
Statistical analysis has also indicated a significant variation in prevalence of Fasciolosis among months. The highest was recorded in March followed by December, February and January respectively. Lower occurrence in January and February probably may be due to an absence of active snail population due to dry conditions. The rise of infection during December and March appears to have been acquired from snails which were infected during the end of the previous heavy rainy season and short rainy season, respectively.
Variations also observed between young and adult animals (p<0.05). It was higher in adults than young animals. This may attributed to the feeding behavior and the chronicity of disease. Henock and Mekonnen (2011) reported that young animals are not usually allowed to go far with adult animals for grazing or feeding that decreases the exposure of animals to infective metacercaria.
The prevalence of fasciolosis was highest for animals having poor body condition. This could be due to stress associated with poor nutrition. Well-fed animals can with stand the harmful effects of gastrointestinal parasites, can remain reasonably productive and may require less anthelmintic treatments when compared with under nourished animals (Bitew et al 2011).
The highest infection was due to Fasciola hepatica. This may be due to the presence of suitable environmental conditions (moisture and temperature) for the Lamynea truncatula. However, the mixed infections revealed that there might be the intermingling movement of the highland animals after infected by the commonly suspected Fasciola hepatica to lowland areas and also vice versa. However, flood might drain the suitable snail for Fasciola hepatica infected by the miracidia to the lowland areas (Gatenby 1991, Suolsby 1992). Fasciola hepatica is the most important species found in Ethiopian livestock, distributed in over three quarters of the nation. Infection with Fasciola hepatica occurs in all areas of Ethiopia except in the arid north east and east of the country (Abera 2007). According to Yilma (1998) Fasciola hepatica and Fasciola gigantica are found in highlands (>1800meters above sea level) and lowlands (<1200meters above sea level) elevations, respectively.
Economic importance of ovine and caprine fasciolosis has been the concern of several workers in Ethiopia. Faciolosis has been resulted economic loss due to decline in production and reproduction, death, loss of carcass weight, predisposition to other diseases, condemnation of liver and treatment cost. However, it is difficult to evaluate the actual economic loss incurred based on the above reasons because of occurrence of poly parasitism in the natural case. Ovine fasciolosis in Ethiopia with relatively higher prevalence corresponds to an enormous condemnation of liver. In the present study the direct economic loss due to rejection of liver was estimated to be $9720 per annum from international market. The economic loss in the abattoir was relatively high when compared with the findings of the previous workers.
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Received 1 November 2015; Accepted 21 July 2016; Published 1 September 2016