ASSESSMENT OF FASCIOLA GIGANTICA INFECTION IN THE LIVER OF CATTLE SLAUGHTERED IN IKPOBA/OKHA AREA COUNCIL, EDO STATE, NIGERIA

his study investigated the prevalence and intensity of Fasciola gigantica infection in the liver of cattle slaughtered in three abattoirs located in Ikpoba/Okha Local Government Area of Edo State, Nigeria. It also estimated the economic implications of the condemned liver. A total of 17,325 cattle were examined in the three abattoirs over a period of 252 days (approximately 69 cattle/day) spanning over the wet and dry seasons; 1,683 cattle were infected with an overall prevalence of 9.71%. In Abattoir A, 11774 cattle were examined with 1069 (9.08%) prevalence. In Abattoirs B and C, 4352 and 1199 cattle, respectively, were examined and 563 (12.94%) and 51 (4.25%) were respectively infected. From the three abattoirs, 155 (0.89%) livers were considered unfit for human consumption due to F. gigantica infection. For the wet season, 1062 (10.89%) cattle livers were infected while 621 (8.20%) were infected during the dry season. The mean intensity of infection during the wet season was 37.80 and 30.42 during the dry season. The financial loss due to infected liver condemnation was at N803,160 (1,947.050USD) showing that liver condemnation arising from F. gigantica infection is a major cause of financial loss to cattle farmers and dealers. There is, therefore, need for adequate veterinary inspections for early detection and treatment of the disease. There should be more meat inspection, especially in private/individual abattoirs.


INTRODUCTION
Fasciola gigantica (the giant liver fluke) is an important plant-borne trematode found mainly in sheep and cattle. The parasite resides in the bile ducts and gall bladder of mammals, especially ruminants and occasionally man (Biu et al., 2006;Otubanjo, 2013). Fasciola gigantica is mainly found in tropical areas (Soliman et al., 2008). Animals become infected while grazing, and they consume the metacercariae of the Fasciola parasite along with aquatic vegetation (Nyindo and Lukambagire, 2015). Fasciola gigantica causes tropical fascioliasis and it is regarded as one of the most important single platyhelminth infections of ruminants in Asia and Africa. The prevalence of fascioliasis in many parts of Africa has been determined mainly at slaughter (Phiri et al., 2005b). Infection of the parasite depends largely on the aquatic snail intermediate host (Lymnaea natalensis) ecology.
Over the years, investigations have been carried out on F. gigantica infection in the world including Nigeria and this has led to improvement in the control measures and decrease in production losses. In Nsukka urban abattoir, Ngwu et al. (2004) reported 10% prevalence of F. gigantica infection in the liver of slaughtered cattle. Ekwunife and Eneanya (2006) investigated the infection prevalence of F. gigantica in cattle slaughtered in three abattoirs at Onitsha area of Anambra State, Nigeria and reported a prevalence of 0.51%. The respective prevalence recorded from the abattoirs was: Nkwor-Ogidi, 7.0%; Oye Olisa, 7.7%; and Onitsha main market, 13.4%. Among the infected livers, 46.4% showed medium worm burden, while 38% and 17.7% respectively, showed heavy and light worm burdens.
The highest number of flukes was 88 and the lowest was 3 per infected liver. In Edo State, Odigie and Odigie (2013) carried out a histochemical techniques-based study on fascioliosis in cattle slaughtered in abattoirs located in three local government areas. A total of 540 cattle were examined with a prevalence of 11.5%. The infected liver showed increase in size with thick capsule, haemorrhagic patches and necrotic foci. Adult and young flukes were recovered from the bile ducts of 62 livers of the examined cattle. Liver cirrhosis was observed in only three cattle liver. The authors noted that differences in feed and water quality in the abattoirs possibly influenced the prevalence of Fasciola disease. A retrospective and prospective study of the predisposing factors and economic implication of fascioliasis in trade cattle slaughtered at abattoir in north-central Nigeria was conducted by Yatswako et al. (2017) showed that the highest prevalence (58.4%) was observed during the late rainy season (August to October), followed by the early rainy season (47.2%) and least was in late dry season (20.1%). Other studies on F. gigantica infection in Although a lot of investigations have been done on Fasciola infection in the liver of slaughtered cattle at abattoirs, there is need for continuous monitoring of the infection in cattle slaughtered and consumed by the populace, especially with respect to the economic implications of liver condemnation. The occurrence of F. gigantica in the liver of a cow leads to its condemnation especially if the liver is heavily infected, which makes it unhealthy for consumption.
The aim of this study is to investigate the prevalence and infection intensity of F. gigantica in cattle slaughtered at some selected abattoirs in Ikpoba/Okha Local Government Area of Edo State, Nigeria, as well as estimates the economic loss arising from condemnation of infected liver of the slaughtered cattle.

MATERIALS AND METHODS
The study was conducted in three abattoirs designated as 'A' (6º21´13´´N and 5º38´33´´E), 'B' (6º21´18´´N and 5º38´39´´E) and 'C' (6º21´17´´N and 5º38´41´´E) at Ikpoba Hill, Ikpoba/Okha LGA, Edo State, Nigeria ( Fig. 1) for 252 days covering both the wet (April to October) and dry season (November to March). The livers of cattle slaughtered in these abattoirs were examined for F. gigantica infection. A premortem examination (checking for skin swellings, if the cattle looked emaciated or has dislocated arm/leg) was carried out on the cattle before slaughtering to determine if the cattle were in good health, if otherwise, if the cattle were treated.
Post mortem examination was carried out after slaughter for Fasciola infection, abcess, tubercolosis and hepatitis. To determine Fasciola parasite infection, the liver was slit open vertically and examined. Parasites were isolated from the infected liver with the aid of forceps, counted and stored in well labeled bottles containing 0.72% saline solution. They were thereafter taken to the laboratory and processed for parasitological procedures (Aisien, 2018). The parasites were flattened between two microscope slides and fixed with 5% formal-saline for about 30 minutes. They were then recovered and preserved with the same fixative. The preserved parasites were washed in several changes of tap water for four hours. They were stained with a weak solution of acetocamine and then dehydrated in increasing alcohol series (50:70:90:100%). The dehydrated specimens were cleared first in 50/50 alcohol/xylene mixture (v/v) before clearing in absolute xylene. Permanent mount was made in Canada balsam.
Prevalence and mean intensity of parasitic infection were calculated. The Chi-square goodness of fit test was performed to test for significant difference between variables. Economic loss was estimated according to the protocol of Mwabonimana et al. (2009) (Table 1). These differences was however not significant (P>0.05). In Abattoir A, 11774 cattle liver were examined and 1069 (9.08%) were infected; in Abattoirs B and C, 4352 and 1199 liver were respectively examined; 563 (12.94%) and 51 (4.25%) were respectively infected ( Table 2). The differences recorded were not statistically significant (P>0.05). The average cattle liver examined daily in the abattoirs were: Abattoir A, 47; B, 17 and C, 5 livers/day.  infected and considered unfit for human consumption (Table 3). There was a high significant difference (P<0.001) between the number of cattle slaughtered in the three abattoirs. High significant difference was also recorded between the healthy liver and the livers considered unfit for consumption in these abattoirs. The highest prevalence (95.75%) of healthy liver was recorded in Abattoir C followed by Abattoir A (90.92%) and B (87.06%). Abattoir B had the highest prevalence (1.24%) of unfit liver for consumption followed by Abattoir A (0.80%) while the least (0.58%) was recorded in Abattoir C.  The monthly economic loss due to liver condemnation arising from F. gigantica infection in slaughtered cattle in the three abattoirs during the study period is presented in Table 5. A total of N803,160 (1,947.05USD) was lost to F. gigantica infection in the three abattoirs. The percentage economic loss for the study period was 0.92%. The highest financial loss of N479,320 (1,161.99USD) was recorded in Abattoir A. This was followed by Abattoir B, N286,120 (693.62USD) and Abattoir C, N37,720 (91.44USD).

DISCUSSION
The cattle slaughtered in the abattoirs investigated were trade cattle brought in from neighbouring countries (Chad and Niger) and from northern Nigeria (Sokoto, Kano and Zaria). Basically, two types of cattle were slaughtered in these abattoirs: the "groundnut" and the "bush" cattle. The "groundnut cattle" are so-called because they are fed with groundnut; they are always reared and fed in ranches hence they are not exposed to parasitic infection from external source unlike the "bush cattle" which are reared in the bush and feed on vegetation. The bush cattle wander about in search of food and water. This nomadic wandering predisposes them to larval stages of parasites, especially the metacercariae of F. gigantica, which they consume along with grass while grazing.
Fasciola gigantica infection was recorded throughout the period of survey. The overall prevalence of F. gigantica recorded in this study was high when compared to other reports. Oladele-Bukola and Odetokun (2014) reported a prevalence of 2.31% (with annual infection rate of 1.57% to 5.68% and a mean intensity of 3.7 parasites/infected host) during the retrospective and perspective analyses of bovine fasciolosis at Ibadan municipal abattoir. Afolabi and Olususi (2016)  The prevalence in this study is low when compared with the account of Odigie and Odigie (2013) who reported a higher overall prevalence (11.5%) of bovine fascioliasis in Edo State. This difference could be due to the histochemical techniques employed by these authors which probably detected more infection than the liver examination used in the present study. The report of higher fascioliasis prevalence by Odigie and Odigie (2013) is not an isolated case. Similarly, Okoh et al. (2016) reported higher prevalence of infection (34.3%) from Lokoja, Kogi State. Liba et al. (2018) also reported a higher prevalence (13.67%) of fasciolosis in cattle slaughtered in municipal abattoir in Maiduguri, Borno State. The higher prevalence recorded in these studies are due to the methods used in examination. A combination of bile and coprological examinations in addition to post-mortem examination of liver were employed and these combinations give a better audit of actual parasitic infections.
Although there were differences in the prevalence and mean intensity recorded among the three abattoirs in this study, these differences were however not significant (P>0.005). Abattoir A had the highest prevalence of healthy liver and the lowest prevalence liver unfit liver for consumption. These are indicative of adequate livestock management (uncontaminated feed and availability of clean water) in the various places where these cattle were kept.
A higher overall wet season prevalence (10.89%) and intensity (37.80 parasites/infected host) of F. gigantica infection was recorded in the liver of cattle slaughtered in the abattoirs compared to dry season (8.20%; intensity, 30.42). This could be ascribed to the fact that more bush cattle were slaughtered during the wet season (personal communication). These are nomadic cattle that are exposed to parasitic infection especially when they graze in wet marshy areas where the cercariae-shedding snail intermediate host (Lymnaea spp.) of the parasite is abundant. When the cercariae are shed by the snail, they encyst on aquatic vegetation (metacercariae) which the cattle consume along with grass while grazing (Ukoli, 1984;Otubanjo, 2013). These findings are similar to the reports of Pfukenyi and Mukaratirwa (2004) in Zimbabwe who recorded a significantly higher F. gigantica infection in cattle in catchment areas of high rainfall than those from relatively low rainfall. In the same vein, Kuchai et al. (2011) reported higher prevalence of F. gigantica infection in cattle during the wet season in India. In Nigeria, Adedokun et al. (2008) similarly reported higher prevalence of F. gigantica in cattle during the wet season (52.3%) than the dry season (21.8%). A higher seasonal prevalence was also observed in Calabar by Abraham and Jude (2014); the authors reported 32.4% prevalence in cattle during the wet season and 19.9% during the dry season.
In contrast, Oladele-Bukola and Odetokun (2014) reported a slightly higher prevalence of fascioliasis during the dry season (2.58%) than in the wet season (2.07%) at Ibadan. Ejeh et al. (2015) also reported a similar trend of higher prevalence of F. gigantica in cattle during the dry season during a retrospective study at Makurdi.
The financial loss in the various abattoirs due to liver condemnation alone is substantial. A total of 803,160.00 naira (1,947.05 USD) was lost accruing from 155 livers (713kg) condemned during the study period. Huge financial losses due to fascioliasis have also been reported by Oladele-Bukola and Odetokun (2014), Ejeh et al. (2015) and Yatswako and Alhaji (2017) respectively, from Ibadan, Makurdi and Niger State, which makes it urgent for cattle farmers to set better cattle management protocols that does not predispose cattle to the level of infection and financial loss to both herders and dealers in cattle.