Introduction

Fasciolosis is among important parasitic diseases in tropical and subtropical countries
which limit productivity of ruminants in particular cattle. Fasciola hepatica and F.
gigantica are the two liver flukes commonly reported to cause fasciolosis in ruminants
(Keyyu et al 2005). The presence of Fasciolosis due to F.hepatica and F.gigantica in
Ethiopia has long been known and its prevalence and economic significance have been
reported by several workers (Fufa et al 2009; Tadelle and Worku 2007; Yilma and
Malone 1998; Daniel 1995 and Dagne 1994).

In general the distribution of Fasciolosis is worldwide. However, the distribution of
F.hapatica is limited to temperate areas and high lands of tropical and subtropical regions
(Soulsby 1986). The definitive hosts for F. hepatica are most mammals, among which
sheep and cattle are the most important once. The geographical distribution of trematodes
species is depending on the distribution of suitable species of snails. The genus Lymnea
in general and L. Truncatula in particular are the most common intermediate host for
F. hepatica. This species of snail was reported to have a worldwide distribution
(Urquhart et al 1996). F. gigantica is found in most continents, primarily in tropical
regions (Dalton 1998).

The economic losses due to fasciolosis are caused by mortality, morbidity, and reduced
growth rate, condemnation of liver, increased susceptibility to secondary infections and
the expense of control measures (Malone et al 1998). The annual loss due to endoparasites in Ethiopia is estimated at 700 million Ethiopian birr/annum (Mulugeta et al 1989). According to the study conducted by Tadelle and Worku (2007) and Fufa et al (2009) fasciolosis caused an average loss of 6300USD and 4000USD per annum at Jimma and Soddo municipal abattoirs, respectively. Kithuka et al (2002) reported up to 0.26 million USD annual loss attributable to fasciolosis-associated liver condemnations in cattle slaughtered in Kenya. Apart from its veterinary and economic importance throughout the world, fasciolosis has recently been shown to be a re-emerging and widespread zoonosis affecting a number of human populations (Mas-Coma and Bargues 1997; Esteban et al 2003).

Diagnosis is based primarily on clinical signs and seasonal occurrence in endemic areas
but previous history of fasciolosis on the farm or identification of snail habitats;
postmortem examinations, haematological tests and examination of faeces for fluke eggs are useful. Coprological analysis is still commonly employed to diagnose bovine fasciolosis, despite the fact that eggs cannot be detected until the latent period of infections, when much of liver damage has already occurred (Rokni et al 2003). Even though, it is impossible to detect fasciola in live animals, liver examination at slaughter or Necropsy was found to be the most direct, reliable, and cost effective technique for diagnosis of fasciolosis (Urquhart et al 1996).

Therefore, the objectives of this study were to determine prevalence and most prevalent species of liver flukes in indigenous adult cattle, to compare diagnostic efficiency of faecal and postmortem examination and to assess the economic importance of bovine fasciolosis due to liver condemnation in the abattoir.

Materials and methods

Description of the study area

Study population and study design

Coprological examination

Postmortem examination

Data management and analysis

Results

A total of 500 adult indigenous cattle were slaughtered at kombolcha industrial abattoir
and examined for fasciolosis. Of the total cattle slaughtered and examined (N=500), 28%
(N=140) of them were found to be positive for lesions of fasciolosis. A total of 500 adult
indigenous cattle were examined by taking faecal samples to laboratory in tightly closed
universal bottles and examined for fasciola eggs. From 500 cattle, 62 (12.4%) were
positives for fasciolosis (Table 1).

Figure 1

Table 1. Prevalence of bovine fasciolosis based on faecal sample

From a total of 140 livers found positive for fluke infection during post-mortem meat
inspection of slaughtered animals, 89 livers(63.6%) harbour F. hepatica, 34 livers
(24.3%) harbours F. gigantica, 10 livers (7.14%) harbour mixed infection and 7
livers (5%) infected with unidentified species due to immature flukes(Table 2).

Figure 2

Table 2. The prevalence of Fasciola spp encountered in postmortem examination of slaughtered animals

Taking postmortem examination as a gold standard technique for diagnosing Fasciola
species infection, the sensitivity and specificity of faecal examination was found to be
44 % and 100%, respectively. The agreements of the two tests were done by calculating
kappa and shows k=0.53. A 5-year database (2004-2009) from the abattoir was retrieved
and analysed. Retrospective results showed a total of 22,026 cattle were slaughtered
from August 2005 to Sep. 2009. During that period, 9167 livers were positive for
fasciolosis and condemned. Based on the current price an average annual monetary loss was about 1833 USD. A retrospective abattoir survey revealed that the prevalence of fasciolosis was 41.6% (Table 3).

Figure 3

Table 3. Prevalence of bovine liver fasciolosis between 2004/5- 2009/10

Discussion

The result obtained in this study is an indication that fasciolosis exists in the study area. In the current study the prevalence (12.4%) indicated by faecal examination was relatively higher than 4.9% recorded in Soddo (Fufa et al 2009) and much lower than 80% recorded for Debre Berhan (Dagne 1994) which is the high land of Ethiopia. Similarly, the autopsy study revealed a higher prevalence of bovine fasciolosis (28%) compared to the (14%) and (14.4%) at Soddo (Fufa et al 2009) and Dire Dawa municipality abattoir (Dagne, 1994) and lower prevalence compared to the 46.58% recorded for Jimma municipal abattoir (Tadelle and Worku 2007), respectively. These differences are probably due to the agro-ecological and climatic differences between the localities, although differences in the management systems may also resulted in such variation. The 28% prevalence of fasciolosis found by autopsy, in this study, was comparable with 31.5%, 30.43%, and 33.4% of bovine fasciolosis recorded at Bedele (Wakuma 2009), Awassa (Hailu 1995) and Gonder municipal abattoir (Roman 1987), respectively. One of the most important factors that influence the occurrence of fasciolosis in an area is the availability of a suitable habitat for the vectors (Urquhart et al 1996). The animals brought to the abattoir for slaughter were mostly from midland and highland areas, where there are few suitable environments for the multiplication of the snails. In addition, optimal base temperatures of 10°C and 16°C are necessary for the vectors of F. hepatica and F. gigantica, respectively, and for the development of Fasciola spp. within the snails. Optimal moisture for snail breeding and development of larval stages within the snails is provided when rainfall exceeds transpiration and saturation is attained. Such conditions are also essential for the development of fluke eggs, miracidiae searching for snails and dispersal of cercariae (Urquhart et al 1996). The study was conducted in the same season, and therefore the prevalence of fasciolosis was not statistically significant on a monthly basis. During the month of February the prevalence is high because during this month grazing pastures are scarce and cattle go far away along the banks of streams and ponds. Of the total livers 63.6% of them were found to be positive for bovine fasciolosis infected by Fasciola hepatica where as Fasciola gigantica, mixed infection and unidentified or immature form of fasciola spp. were recorded to be 24.3%; 7.14%; and 5% diagnosed as positive for fasciolosis. Similar study conducted at Bedele and Jimma municipal abattoir reported 64.5%, 60.3%; of liver harbored F.hepatica, 24.8%, 23.85%; of liver harbored F. gigantica; and 10.7%, 11.93% harbour immature or unidentified form of fasciola species were recorded by Wakuma (2009) and Tadelle and Worku (2007), respectively.

Our result was not in agreement with the finding of Fufa et al (2009) with the highest
prevalence of F.gigantica in Soddo municipal abattoir. The prevalence of fasciolosis and the Fasciola spp. found vary with locality. In Ethiopia F. hepatica and F. gigantica infections occur in areas above 1800m.a.s.l. and below 1200m.a.s.l., respectively which has been attributed to variations in the climatic and ecological conditions such as altitude, rainfall, temperature and livestock management system (Yilma and Malone 1998). The high prevalence rate of F. hepatica may be associated with the existence of favourable ecological biotops for L. truncatula.

Relatively small proportion of cattle were found infected with F. gigantica alone or
mixed infection with both species. This might be explained by cattle coming to abattoir
from highlands and flood prone areas and therefore drainage ditches are favorable habitat to natalensis (Urquhart et al 1996).

The lower prevalence of fasciolosis reported using coproscopy indicates that the lower
sensitivity of this procedure in detecting the disease due to the intermittent nature of the
expulsion of the eggs through the faeces. A period of 8–15weeks after infection is needed
for the appearance of Fasciola spp. eggs in the faeces, by which time most pathological
lesions have already occurred (Hillyer 1999; Sanchez-Andrade et al 2002).

Furthermore, detection of Fasciola spp. eggs can be unreliable even during the patent
period because the eggs are expelled intermittently, depending on the evacuation of the
gall bladder (Briskey 1998). Finally, 1833USD monetary loss per annum incurred due to
condemnation of cattle livers infected with Fasciola spp. was in agreement with finding
of Mwabonimana et al (2009) at Arusha abattoir, Tanzania and lower than 4000
and 6300USD per annum losses reported for Soddo municipal abattoir (Fufa et al 2009)
and Jimma municipal abattoir (Tadelle and Worku 2007). However, the losses at Kombolcha industrial abattoir, its economic implications should not be overlooked.

Conclusion

In present study moderate prevalence of bovine fasciolosis was obtained when compared
with prevalence reported by different researchers at different area. The dominant fasciola
revealed was fasciola hepatica at Kombolcha industrial abattoir (ELFORA) that
induces economic losses due to liver condemnation. In general it can be concluded that
fasciolosis is one of major problem for livestock development in the study area by
inflicting direct economic losses and its occurrence is closely linked to the presence of
biotypes suitable to the development of snail intermediate host. So as to reduce these
losses, strategic anthelementics treatment with appropriate fluckicide drug should be
practiced and a combination of control measures include drainage, fencing and
molluscides have to be used to ensure a satisfactory degree of control in the long run.

Acknowledgements

The authors would like to acknowledge all staff members of Veterinary Regional
Laboratory of Kombolcha and to all Kombolcha industrial abattoir workers.