College of Veterinary Medicine and Agriculture

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    Epidemiology of Cattle ond Sheep Fasciolosis in Selected Abattoirs of Ethiopia and Estimation of the Associataed Economic Losses Due to Lvier Condemnation and Coprological Study in and around Debreberhan and Evaluation of the Immune Response of Sheep Against Primary Experiential Infection with Fasciola Hepatica Metacercariae
    (2021-06) Abebayehu, Tadesse; Prof. Hagos Ashenafi), Dr. Dinka Ayana)
    Fasciolosis is an economically important disease of ruminants which affects mainly sheep and cattle worldwide and causes important economic losses in the animal husbandry. These losses are attributable to mortality, morbidity and condemnation of livers at slaughter. In Ethiopian highlands, sheep and cattle production has remained as an important sector of the country’s agricultural economy. However, their potential has been exploited far less than expected due to several constraints including shortage of forage, poor livestock management and diseases. In Ethiopia, fasciolosis is widespread encompassing the major productive highland plateaus except very limited areas in arid escarpments. The study of liver flukes in live animals depends on the detection of faecal eggs and the use of faecal egg counts. However, these detect only patent infections and their interpretation is constrained by the paucity of information about how they relate to parasite burdens and pathology. Moreover, abattoir-based studies have been used as a component of the study of the liver fluke and to describe various aspects of liver fluke infection. Controlling fasciolosis by vaccination rather than chemotherapy would be a cheaper, more efficient and reliable long term solution for the prevention of infection and eradication of its transmission. Regardless of several attempts, vaccines against Fasciola hepatica were not yet produced to the point of commercialization. A variety of irradiation-attenuated parasite species have been used experimentally to induce protection in various host species. These studies have demonstrated that development of vaccine is potentially feasible. The present study entitled "Epidemiology of cattle and sheep fasciolosis in selected abattoirs of Ethiopia and estimation of the associated economic losses due to liver condemnation and coprological study in and around Debreberhan and evaluation of the immune response of sheep against primary experimental infection with Fasciola hepatica metacercariae" was undertaken in five abattoirs (Debreberhan, Addis Ababa, Bahrdar, HELMIX, ELFORA) while the experimental study was conducted at Aklilu Lemma Institute of Pathobiology. The objectives of the study were to assess the abattoir and coprological prevalence fasciolosis in sheep and cattle and assessment of the associated economic losses in three municipal and two export abattoirs as well as the vaccine trail on immune response of sheep to primary infection with attenuating irradiating dose of Fasciola hepatica metacercariae. The present findings on ruminants at five abattoirs had shown higher prevalence of fasciolosis (46.6% ± 0.059). However, this was much lower that observed in Debreberhan abattoir for sheep (84%) and cattle (77.8%). Overall fasciola infections were only diagnosed in 605 (53.8%) animals coprologically. The highest prevalence was for sheep (60.1%) and followed by cattle (49.2%). The overall herd level infection prevalence, as estimated from the egg-shedding index, was 50.9±29.3. In Debreberhan abattoir, F. hepatica was a dominant (87.9%) species identified followed by F. gigantica (6.3 %). However, this prevalence was much higher than that observed in five of the abattoirs altogether for F. hepatica (70.9%) and F. igantica (21.5%). The overall prevalence of fasciolosis observed in ruminants slaughtered in export abattoirs was 34.6% (877/2530) whereas it was significantly higher in ruminants slaughtered at municipal abattoirs 65.2% (1653/2530) as the whole. The mean annual financial loss recorded altogether in export and municipal abattoirs was 7, 049, 638 ETB / 335, 697.1 USD. The immune response to the infection was proved by the production of specific IgG1 antibodies to irradiated F. hepatica. The parasite viability was severely affected by doses of γ- irradiation of 120 Gy or 240 Gy. In the aforementioned doses relatively low numbers of mature flukes of about 60 (17.1%) and 38 (10.8%) were recovered than the control group, respectively. The sensitized lambs also showed less hepatic damage compared with the controls as indicated by lower liver lesions and lower levels of the serum enzyme glutamate dehydrogenase and γ- glutamyl transferase. The IgG1 antibody titers measured by ELISA vary with the dose of γ- irradiation. Sheep vaccinated with 240 Gy produced the highest antibody titre compared to the non sensitized positive controls. In conclusion, the present study plainly disclosed the high prevalence of fasciolosis both at herd and individual animal level and at abattoir survey. The eggs shedding index seemed to be useful approach in current epidemiological survey than the individual animal coprologic examination. The present findings on ruminants at abattoirs had shown higher prevalence of fasciolosis with significant annual financial loss. Vaccination of sheep with γ-irradiated metacercarae invariably yielded the specific immune response to different treatment groups. Irradiation of F. hepatica had resulted in reduced hepatic damage during migration of juveniles and a strong local immune response, represented by infiltration lymphocytes, eosinophils and macrophages and antifasciola IgG1 titers