Bovine fasciolsis is an economically important parasitic disease of cattle caused by treamatodes species of the genus Fasciola, which migrate in the hepatic parenchyma and establish and develops in the bile ducts. Fasciolosis caused by fasciola hepatica and Fasciola gigantica, is one of the most prevalent helminth infection of  ruminants in different parts of the world. It causes significant morbidity and mortality (Okewole et al., 2000; WHO, 1995).

The snails of the genus lymnae are mainly involved as an intermediate host in the life cycle of fasciolosis. The epidemiology of fascilosis is dependent on the ecology of the snail intermediate host. lymnae truncatula is the most common intermediate host for fasciola hepatica in different part of the world (Njau et al., 1991) and in Ethiopia (Graber et al., 1975). It is an amphibious or a mud-dwelling snail which prefers moist temperature condition (15 to 22°C) though it appears that variants found in the tropics have adaptation to higher temperature mostly in the lowland areas and can breed and survive at 26°C with sufficient moistures. The most important intermediate hosts of Fasciola gigantica are Leptodactylus natalensis and Leptodactylus auriallaria (Urquhart et al., 1996; Dunn, 1978; Soulsby, 1982). L. natalensis is the recognized intermediate host for F. gigantica (Yilma and Malone, 1998). This snail is strictly an aquatic snail often found in Africa and requires well oxygenated none polluted water bodies and can aestivate during dry periods. Optimal temperature requirement for the completion of parasite developmental stages within the snail is 22 to 26°C. However, in irrigated areas, snail breeding is less circumscribed and well continues all year around, except for period’s extreme temperature levels (Souls, 1982).

F. hepatica is a temperate species and it is found in Southern America, Northern America, Europe and Australia and Africa, but found in the highlands of Ethiopia and Kenya. It is the major cause of liver fluke disease in Ethiopia. Its tropical counterpart, F. gigantica, on the other hand is widely distributed in tropical countries, in Africa and Asia. In Ethiopia, F. gigantica is found at an altitude below 1800 m above sea level while f. hepatica is found at altitude between 1200 to 1560 m above sea level (Yilma and Malone, 1998). Mixed infection by the two species can be encountered at 1200 to 1800 m above sea level (Mulugeta et al., 1989).

The clinical features of fasciolosis can have acute, sub acute and chronic forms. Acute fasciolosis occurs as disease outbreak following a massive, but relatively short-term, intake of metacercariae (Urquhart et al., 1996). The high fluke intake is often the result of certain seasonal and climatic conditions combined with a lack of appropriate fluke control measures. It typically occurs when stocks are forced to graze in heavily contaminated wet areas as a result of over stocking and /or drought. Animals often affected by acute fascilosis especially sheep and goat may display no clinical signs prior to death while some may display abdominal pain, discomfort and may develop jaundice (Souls, 1982; Urquhart et al., 1996). Death usually results from blood loss due to hemorrhage and tissue destruction caused by the migratory juvenile flukes in the live resulting in traumatic hepatitis (Urquhart et al., 1996).

Sub-acute fascilosis is caused by ingestion of a moderate number of metacercariae and is characterized by anemia, jaundice and ill-thrift. The migrating fluke causes extensive tissue damage, hemorrhage and in particular liver damage. The result is severe anemia, liver failure and death in 8 to 10 weeks (Urquhart et al., 1996). Chronic fascilosis is the most common clinical syndrome in sheep and cattle. It occurs when the parasite reaches the bile ducts. The principal effects are bile duct obstruction, destruction of liver tissue, hepatic fibrosis anemia and submandibular edema (Mitchell, 2003). In addition to these, a condition known as “black disease” is a complication, which usually is fatal. Here, a secondary infection due to the bacterium clostridium novyi type B, proliferating in necrotic lesions produced by the young larvae migrating in the liver is responsible for the fatal outcome (Radostits et al., 2007). Chronic fasciolosis provides the right environment in the liver for the germination of the spores of the bacterium. This form of the disease is much more common particularly in man. In humans the presence of the flukes causes a number of non-specific symptoms including malaise, an intermittent fever, mild jaundice, anemia eosinophilia and frequently pain under the right costal margin (Chhabra and Singla, 2009). Furthermore, fasciola species do not appear to be fully adapted to using man as a definitive host, as the flukes may often give rise to entopic infections, particularly in the lungs and sub cutaneous tissues, where they may be found encysted (Slifko et al., 2000).

Pathogenesis of fasciolosis varies according to the parasitic development phases parenchymal and bilary phases. The parenchymal phase occurs during migration of flukes through the liver parenchyma and is associated with liver damage and hemorrhage. The bilary phase coincides with parasite residence in the bile ducts and results from the haematophagic activity of adult flukes and forms the damage to the bile duct mucosa by their cuticullar spines (Urquhart et al., 1996).

 Hypoalbuminanemia and hypoglobulinanemia commonly occur in liver fluke infections in all host species. During the parenchymal stage of the infection, liver damage caused by the migrating flukes compromise liver function, which was reflected in decline in plasma albumin concentrations, attributed partly, to reduce rate of synthesis and partly to an expansion of the plasma volume (Behm and Sangstes, 1999; Urquhart et al., 1996).

Fascilosis is known by different local names in various part of Ethiopia that vary according to the region and language. In Amharic it is called ‘kulkult’, ‘Wadammo’, ‘Yegubet till’. In Oromia region it is known as ‘Dada’o’, ‘Losha’, and ‘Rammo tiruu’. In Tigray language it is termed as ‘Ifil’ (Adem, 1994).

The economic losses caused by bovine fascilosis indicated that the productive efficiency was reduced by 8% in mild infection and over 20% in severe infection. In sub Saharan Africa, data on bovine fascilosis reported up to 60% incidence  rates,  up  to  50%  liver  condemnation rates, up to 5% reduction in weight gain (Ross, 1970; Hyera, 1984), 16% loss in daily milk production (Bahru and Ephrem, 1979) and annual loss of 198kg of body weight per fluke (Ogunrinade et al., 1982).

Diagnosis of fascilosis may consist of tentative and confirmatory procedures. A tentative diagnosis of fascilosis may be established based on prior knowledge of the epidemiology of the disease in a given environ-ment, observation of clinical sign, information on grazing history and seasonal occurrence. Confirmatory diagnosis however, is based on demonstration of fasciola eggs through standard examination of feaces in the laboratory, post mortem examination of infected animals and demonstration of immature and mature flukes in the liver (Souls by, 1982; Urquhart et al., 1996).

Several workers have reported the presence and economic significant of fasciolosis in Ethiopia. The prevalence of the disease is known to be relatively high (Bahru and Ephrem, 1979) causing considerable economic loss in livestock production. However, few attempts have been made to study the epidemiology of this parasitic problem in various section of the country with the specific aim of determining the parasitic burden, especially in relation to months of the year, rain fall, temperature, humidity, altitude and other related factors. This information is very important in planning control programs and also estimating the economic burden to the country as a result of this parasite.

Ada'a Berga is found in suitable geo ecological zone for occurrence of fasciolosis and the area has also several water reservoirs. However, little information is available regarding the coprological and abattoir prevalence of fasciolosis. Therefore, this study was aimed to know the prevalence of bovine fasciolosis in and around Inchini town, to determine the liver pathology and to the generate base line data for future research of bovine fasciolosis on the study area.

Study area

 

The study was conducted from November, 2008 to March, 2009 in and around Inchini town, Ada’a Berga Woreda, West showa Zone, Central Ethiopia. Geographically, the area is located at 64 km North west of Addis Ababa on the road of Mugher cement Enterprise and located at 9° 12’ to 9° 37^’ N latitude and 38° 17’ to 38° 36’ E longitude. According to the publication bureau of planning and economic development for Oromia regional state, West showa office (1998) the maximum and minimum temperature of the woreda is 25 to 10°C, respectively and an annual rain fall ranging from 918 to 1368 mm and an altitude ranges from 1400 to 3270 m above sea level.

Ada’a Berga Woreda has a climatic condition of 21% highland, 54% mid latitude and 75% lowland. Based on the altitude, there are three main agro-climatic regions can be identified, “Daga” (28%), “Winodega” (38%) and “Kola” (34%) areas. The soil types in the area are black (43%), Red (37%) and Brown (mixed) (25%). The rain is bi-modal with short rainy season, february to march and long rainy season from june to september. According to  the  information obtained from the veterinary section of Ada’a Berga Woreda veterinary clinic Report, 2007/2008, the total live stock population of this Woreda was estimated as 119,277 cattle, 42,308 sheep, 51,828 goats and 20,685 equines.

 

 

Study animals

 

A total of 573 cattle found in Inchini town and its surroundings (Deku kitto, Gatira Nabe, Bishan Dimmo, Maru Chobot and Sire Berga) were selected randomly from each kebeles and subjected to qualitative coproscopic examination. In this study both indigenous and cross breeds of animal found under the extensive grazing systems were included. In the abattoir study, adult male and female indigenous animals were provided for slaughter from different localities in the woreda’s and surrounding areas. Prior to slaughtering, animals were identified using their identification numbers and all important information were recorded on prepared format.

 

 

Study design

 

A cross-sectional study was designed to determine prevalence of fasciolosis in the area. Coprolgical examination of live animals and post mortem survey on animal (cattle) slaughtered at Inchini municipal Abattoir were carried out in this study. Moreover, pathological lesion of livers was categorized.

 

 

Coprological examination

 

Fecal samples were directly collected from the rectum of each and were transported to Akilu Lemma Institute of Pathobiology (ALIPB) for detailed coprological examination. Samples that were not processed within 24 h of collection were stored in a refrigerator at 4°C. In the laboratory, coproscopic examinations were performed to detect fasciola eggs using the sedimentation (Hansen and Perry, 1994). Age estimation of animals involved in the study was done based on their dental eruption formula and number of rings on their horns; the age of the animal were determined and classified as young (< 4 years) and adult (> 4 years) (Cringoli et al., 2002). Body condition scoring of animals involved in the study was made according to Nicholson and Sayers (1986). The score ranges from 1 (emaciated) to 5 (very good) by observing the body conformation of the animal. Then scores were classified as poor (for 1, 2 and 3 BCS) and good (for 4 and 5, BCS).

 

 

Abattoir survey

 

Livers of slaughtered animals (196) at Inchini municipal abattoir during study period were carefully inspected for presence of liver flukes first by visual inspection to observe enlarged bile ducts and irregularity of the morphology of the liver, then by palpation and carrying out multiple incisions of all visible bile ducts and their branches to look for adult fasciola lodged there. Sex and breed and result of the slaughtered animals were registered. The recovered liver flukes during the survey in slaughter house were morphologically (on basis of size and shape) identified as F. hepatica and F. gigantica (Souls, 1982) and pathology of affected livers were grouped into three; slightly affected: if none or only one enlarged or duct is seen before cutting and cutting revealed enlarged or calcified bile ducts and/ or flukes; moderately affected: if more than one enlarged bile duct was visible before cutting and severely affected: if atrophy of left lobe and hyperplasia of the right lobe is seen giving the liver triangular shape (Ogunrinade et al., 1982).

 

 

 

Sample size determination

 

A random sampling method was employed in both study type (field and abattoir survey). To determine the sampling unit, the sampling frame consists of a list of 31 PAs of Ada’a Berga Woreda were obtained from the documents of the agricultural office of the Woreda. Then six kebeles from 31 PAs were randomly selected by lottery systems. The samples were taken by simple random selection from each six kebeles. To determine the sample size, a fasciolosis prevalence rate of 50% was taken into consideration since there was no research work on fasciolosis in the area. The desired sample size for the study was calculated using the formula given by Thrusfield (1995) with 95% confidence interval and 5% absolute precision.

 

Where: n= sample size. P exp= Expected Prevalence. d² = Absolute precision

Accordingly, the estimated sample size was 384 animals; however, to increase the precision 573 cattle were included in the study.

 

 

Statistical analysis

 

Data was entered into Ms excel and checked for errors that occurred during data entry. Any error was sorted and corrected. Finally, data analysis was made through STATA 7.0 version. The association of fasciola infection rates on the basis of age, sex and body condition was compared using X² test (chi-square). Infection rates on the basis of age and sex on the prevalence of fasciolosis were also analyzed by the Pearson’s correlation coefficient (Putt et al., 1988). P-Value < 0.05 was considered as statically significant. 

Coprological findings

 

Examination of 573 feacal sample revealed that 291 (50.79%) were found positive for fasciola eggs. There was no significant difference between study kebeles. However, highest prevalence was obeserved at Gattira Nabe (67.05%) kebele followed by Bishan Dimmo (55.56%), Deku kitto (48.74%), Inchini (45.46%), Maru Chobot (43.10%) and the lowest was seen at Sire Berga (37.78%) (Table 1). There was significant difference among study months (p < 0.05). The highest prevalence of fasciolosis was noted in November (90.04%) and December (80.34%), that is during the beginning of the dry season and the least prevalence was recorded in January (17.89%) and February (18.69%) that is during the dry season (Table 2). Present study indicated 50.39 and 51.09% prevalence of fasciolosis in male and female, respectively. No significant difference (p > 0.05) was seen between sexes (Table 3). Analysis of the prevalence rates in different age group showed negative/ inverse correlation that is, as age increases the infection decreases. Similarly, there was also statistically significant difference (P<0.05)  among  cattle  of  different age groups (Table 4).

The result of present study showed a significant difference among body condition score (p < 0.05). Infection rates of fasciolosis in ‘Poor’ body condition group was significantly higher than animals with good body condition group (Table 5). Regarding breeds, prevalence rates of 56.94% in local breeds and 14% in Holstein cross (Friesian × Horoo) breed were registered. Analysis of the result of breed basis shows significant variations (P < 0.05) (Table 6).

 

 

Abattoir survey

 

Out of 196 livers of slaughtered animals examined, 107 livers found infected with adult liver fluke of which highest infection was recorded due to F. hepatica 73 (68.22%), F. gigantica 9 (8.41%) and 25 (23.36%) mixed infection with both F. hepatica and F. gigantica (Figure 1). Analysis of liver lesion intensity of 107 infected livers indicated that 51(48%) were lightly affected, 42 (39%) moderately and 14 (13%) severely infected (Figure 2).

Bovine fasciolosis exists in almost all regions of Ethiopia (Graber, 1975; Bahru and Ephrem, 1979). However, the prevalence rate, epidemiology and Fasciola species involved vary with locality. This is mainly attributed to the variation in the climatic and ecological conditions such as altitude, rainfall, temperature and management systems of livestock. Based on the result of this study, bovine fasciolosis found a significant disease in Ada'a Berga woreda, with an overall prevalence of 50.79%. This is in close agreement with other reports, such as 86% in keffa (Bahru and Ephrem, 1979), 84.4% at Bahir Dar abattoir (Fekadu, 1988), 80% in and around Debre Berhan (Dagne, 1994) and 82.5% in Western Showa (Yadeta, 1994). However, majority of these reports are higher prevalence as compared to current prevalence. This may be due to the expansion of animal health extension and veterinary services that means the opening of animal health post at kebeles/peasant association level and the intervention of nearby private veterinary drug shops (pharmacies). This enables the farmers to have more access for disease control and intervention.

Infection rate of bovine fasiolosis in Gatira Nabe was relatively higher than the other five study sites; this may be attributed to the existence of more favorable environment for both the snail intermediate host and the parasite in Gatira Nabe kebele which has heavy dark- brown clay soil (with slightly acidic PH), which has high capacity of water retention and is mostly marshy area for long periods during the dry season.

The overall abattoir survey prevalence of bovine fasciolosis (45.59%) observed in this study is in harmony with  report  of  Bahru  and Ephrem (1979)  from  Gondar, Yehenew (1985) around Lake Tana, Fekadu (1988) around Bahir Dar and Yohannes (1994) from Bahir Dar abattoir reported prevalence rates of 61, 56, 62.2 and 61.97%, respectively. However, the prevalence report of these workers are relatively higher than the present finding and this variation might be attributed to the differences in the infestation level of the study areas and the previous works were conducted during the wet period of the year when infestation rates of fasciolosis is expected to be high.

Prevalence rate of 50.39 and 51.09% was recorded in male and female animals, respectively. There was no statistically significant difference (P>0.05) between the two sexes, this signifies that sex has no impact on the infection rate and both male and female animals are equally susceptible and exposed to the disease. Similar results that support the present finding were reported by Yehenew (1985), Fekadu (1988), Rahmeto (1992) and Dagne (1994). However, some workers found higher prevalence rate in the male than female; their justification is related to the management system with longer exposure of males out door when females are kept indoor at the beginning of lactation (Balock and Arthur, 1985).

Statistical analysis of infection rates on the basis of age indicated a significant differences (P < 0.05) among different age groups. The decrease in infection rate (prevalence rate) as age increase is the result of acquired immunity which is manifested by humoral response and tissue reaction in bovine liver due to previous challenge (Ogunrinade et al., 1982). Dwinger et al. (1982) also reported the increased resistance (low prevalence) as age increases is most likely related to the higher level of tissue reaction seen in bovine liver, severe fibrosis which impedes the passage of immature flukes, acquired resistance, thickening, stenosis and calcification of bile ducts, assumed unfavorable site for adult parasites and consequently fasten their expulsion. Consistent with current finding, several studies done  by  Fekadu (1988),

Rahmeto (1992) and Dagne (1994) in different parts of Ethiopia stated inverse correlation of prevalence rate and age of cattle.

There was a statistically significant association (p < 0.05) between fasciola prevalence and body condition of the animals in which infection rates in poor body condition animals was significantly higher than that of good body condition. This signifies the importance of fasciolosis in causing weight loss and is the characteristic sign of the disease. Chronic fasciolosis is the commonest form of the disease in cattle and one of the characteristic sign is weight loss (emaciation) (Graber, 1975; Troncy, 1989; Urquhart et al., 1996). This finding concur with study report of Bekele (2010) reported high prevalence in cattle with poor body condition compared to cattle in medium and good body condition.

The species of fasciola involved in causing the disease in the study area was studied on 107 fasciola infected livers during postmortem examination of slaughtered animals. The result of the study indicated F. hepatica (68.22%), F. gigantica (8.41%) and mixed infections (23.36%). The predominant species involved in causing bovine fasciolosis in the study area is F. hepatica and is associated to the existence of favorable ecological condition for the study area such as swamp areas around the lake and marshy areas in the low-lying plain areas and temporary shallow ponds favorable habitat for l. truncatula (intermediate host of F. hepatica) and this allows the existence of F. hepatica in the study area. Borders of lake, Flood-prone areas, and low-lying marshes and drainage ditche areas are favorable habitat for l. natalensis (intermediate host of F. gigantica) (Troncy, 1989).

Mixed inflection by both species of fasciola may occur in the liver of the same animal and this attributed to the existence of ecological conditions conducive for replication of both species of snails and intermingling of cattle from various grazing areas. Similar results which support the present finding were reported by Graber (1975), Fekadu (1988) and Adem (1994). This is attributed mainly to the variation in the climatic and ecological conditions such as altitude, rainfall temperature and livestock management systems (Yilma and Malone, 1998). Additionally Graber (1975) and Dagne (1994) reported that in Ethiopia f.hepatica and F. gigantica infection occur in areas above 1800 m.a.s.l and below 1200 m.a.s.l., respectively which supports the present study. 

The present study concluded that fasciolosis is the most wide spread and prevalent parasitic disease affecting the health and productivity of animal in the study area. Additionally, abattoir study revealed that bovine fasciolosis is prevalent disease in the study area, causing great economic losses as a result of condemnation of affected liver.

Proper attention should be paid for strategic deworming; animals should not be allowed to graze in water reservoir areas. Moreover, further research on the epidemiology of the disease, biology and ecology (meteorological) of intermediate host snails (lymnaea) to overcome difficulties in planning and programming control strategies is highly recommended.

Authors have none to declare.