Background

Fascioliasis is regarded as one of the most important parasitic diseases in the world as meat consumption is on the increase worldwide to cover for protein demands (Odigie and Odigie, 2003). It is also known as distomatosis and liver rot (Aliyu et al., 2014), it is an helminth disease caused by plant-borne trematode of the family, Fasciolidae, commonly known as liver flukes and the definite host range include many herbivorous mammals and humans (Mas-Coma et al., 2005). The parasite lives parts of its life in intermediate host mainly snails of the genus Lymnaea which is found in and around wet areas, such as water holes, irrigation canals, dams and streams within grazing areas. Farm animals are likely to pick up the parasite if they drink from these sources (Okewole et al., 2000). There are various species of the parasites such as: Fasciola nyanzae, Fasciola tragelaphi, and Fasciola jacksoni (Saleha, 1991) but the economically important ones are Fasciola hepatica and Fasciola gigantica (Garcia et al., 2007).

The disease is responsible for considerable economic losses in the cattle industry, mainly through mortality, liver condemnation, reduced production of meat, milk and wool. It also leads to an additional cost of control in terms of medication costs, veterinary fees, and labour costs aimed at reducing parasitism (Dargie, 1987; Hillyer and Apt, 1997; Oladele-Bukola and Odetokun, 2014). It can also lead to chronic low-grade anaemia and emaciated carcasses at slaughter (Aliyu et al., 2014). Fasciola hepatica infects more than 300 million cattle and 250 million sheep worldwide and together with Fasciola gigantica, causes significant economic losses to global agriculture; estimated at more than US$3 billion annually through lost productivity, such as a reduction of milk and meat yields (Mas-Coma, 1997).

Apart from its veterinary importance, Fasciola spp. are also capable of causing disease in humans (Ai et al., 2010) and is a significant public health threat due to emerging food-borne zoonosis in developing countries like Pakistan (Qureshi et al., 2005). Savioli et al. (1999) reported that fascioliasis was earlier limited to populations within well-defined watershed boundaries however; recent environmental changes and modification in human behaviour have increased the risk in other new populations as humans are incidental hosts and most often acquire infection by eating watercress grown in sheep-raising areas. Infection may be transmitted by other freshwater plants, including water lettuce, mint, alfalfa, and parsley.

Humans can also acquire infection by drinking contaminated water containing viable metacercaria (Chan and Lam, 1987). Prior to 1992, the total number of reported human cases of fascioliasis was estimated to be less than 3000 and more recent figures suggest that between 2.4 and 17 million people are currently infected, with a further 91.1 million living at risk of infection (Keiser and Utzinger, 2005). The incidence of animal and human infection rises during rainy season due to an increased number of snails and longer survival of metacercaria (Arjona et al., 1995).

The value of the losses resulting from this disease runs into millions of naira (Ogunrinade and Ogunrinade, 1980). However, the estimation of economic losses due to fascioliasis at national and regional level is limited by lack of accurate estimation of prevalence of the disease (Adedokun et al., 2008). Apart from direct economic losses associated with the disease, other non-quantifiable losses are also experienced. For instance, liver is generally regarded as a delicacy in Nigeria, usually in high demand and this makes condemnation during post-mortem inspection a problem as butchers and meat traders hide their meats from inspectors or even refuse inspection. Other losses can also be through death of unknown number of animals (including the under-aged) due to acute fascioliasis (Oladele-Bukola and Odetokun, 2014). This research is intended to determine the prevalence of fascioliasis among slaughtered cattle in abattoirs in Akure metropolis.

1 Results

The results showed that of the 905 cattle sampled, 471 (52.04%) were males while 434 (47.96%) were females. The prevalence of infection was observed to be significantly higher among the female cattle (8.53%) than the male cattle (5.73%) (Table 1). The results further revealed that 70.31% (n = 45) of the cattle that were infected with the disease showed light worm burden, that is the total worm recovered from the liver is ≤ 20, 26.56% (n = 17) of the infected cattle showed medium worm burden, worm load 21-50 and 3.13% (n = 2) of the infected cattle showed heavy worm burden, worm load ≥ 50 (Table 2). The worm burden was higher in cattle slaughtered in public abattoir (76.56%) than those slaughtered in private abattoir (23.44%). Evaluation of the intensity of the disease among gender of the cattle revealed that the worm burden was higher in the female cattle (n = 37) than the male cattle (n = 27) (Table 3). Species identification of the parasite revealed that F. gigantica was the most prevalent Fasciola spp in the study area with a prevalence rate of 82.81% while F. hepatica was the least prevalent (1.56%). Meanwhile, mixed or co-infection of the two parasites was noted among 8 cattle (Table 4).

2 Discussions

From the results of this study, it can be deduced that prevalence of fascioliasis is low in the study area with a total prevalence of 7.07% recorded among the slaughtered cattle during the study period. The study of disease in two different abattoirs also revealed that prevalence of fascioliasis is higher in private abattoir (8.48%) than the public abattoir (6.76%). The reason might be as a result of thorough inspection carried out by veterinary health officers in public abattoir, which compels the butchers to always go for healthy cattle to avoid the livers of their cattle being seized. The high prevalence observed in private abattoir suggests that there is less or no inspection carried out in private abattoir, hence the owners can afford to kill any kind of cattle, not minding the health status of the cattle and the health implication to the consumers. The low prevalence (7.07%) observed in this area is similar to the reports of Ozung et al. (2011) in Ikom abattoirs (7.35%) and Omoleye et al. (2012) in some abattoirs in Ondo State (6.6% and 8.3%). A sharp contrast was also observed in the reports of Fabiyi and Adeleye (1982) at Jos abattoirs (71.1%) while Schillhorn et al. (1980) recorded a prevalence of 65.4% at Soba near Zaria. This suggests that prevalence of fascioliasis in northern Nigeria is higher than that of southern Nigeria. Low prevalence observed in this study area could be attributed to factors such as better management of cattle which is as a result of gradual increase of the public awareness on the need to control the disease (Oladele-Bukola and Odetokun, 2014). This also implies that healthier animals are now transported to the southern Nigeria markets. Furthermore, mode of transportation of cattle from north to south has also been improved from the nomadic transportation to modern transportation such as lorries and trailers, the modern transportation restricts the cattle from grazing around rivers and streams to feeding on shepherds choice of pasture (Usip et al., 2014). This greatly reduces their exposure to metacercariae of Fasciola spp.

Postmorterm examination of infected livers showed that F. gigantica is the predominant species causing fascioliasis in the study area. This finding is similar to the reports of other authors such as Ekwunife and Eneanya (2006), Ozung et al. (2011), Afam (2012) and Usip et al. (2014). The authors also found F. gigantica as the predominant species in their various study areas. The predominance of F. gigantica in the study area and other part of Nigeria as reported by other authors (Ekwunife and Eneanya, 2006; Ozung et al., 2011; Afam, 2012) may be due to abundance of Lymnaea natalensis which is reported to be the intermediate host of F. gigantica in Nigeria (Ukoli and Asamu, 1979) while low prevalence of F. hepatica may be associated with inexistence of favourable ecological biotopes for Lymnaea truncatula; an intermediate host for the species (Shiferaw et al., 2011). Observation of the infected livers showed that the intensity/worm burden was generally low among the infected livers as 71.86% of the infected livers have (1-20 worms).

This study further revealed that, there is no significant difference in the prevalence of infection between the male and female cattle (P > 0.05). This might be because male and female cattle graze together and are both expose to equal risk of infection (Usip et al., 2014). This report agrees with the report of Opara (2005) who observed that the prevalence of fascioliasis between male (48.45%) and female cattle (46.02%) in Uyo abattoir were not significantly different (P > 0.05). The result of prevalence of infection between genders was also supported by the reports of Usip et al. (2014) and Rahmato (1992) in his studies, concluded that sex has no impact on the infection rate of cattle to fascioliasis and both male and female are equally susceptible and exposed to the disease.

3 Materials and Methods

3.1 Study area

The study was conducted in Akure, Ondo State, Nigeria. Akure is characterized with hot and humid climate which is influenced by rain-bearing southwest monsoon winds from the ocean and dry North-West winds from the Sahara Desert. The rainy season lasts from April to October, with rainfall of about 1524mm per year. Temperatures vary from 28⁰ C to 31⁰ C with mean annual relative humidity of about 80%. Animals slaughtered in the public and private abattoirs of the study area were considered for the study. The breeds of cattle present in these abattoirs were Kuri breed, White Fulani, Adamawa Gudali and N’dama breed.

3.2 Ethical consideration and sample collection

Prior to this research, ethical approval was obtained from the management of Ondo State Veterinary Office and Akure abattoirs. The butchers gave consent before the slaughtered animals (cattle) were inspected for Fasciola infection. The abattoirs were visited five (5) times every week for a period of six months from April to September, 2015. The cattle were slaughtered between the hours of 6.30 am and 9.00 am. Before the animals were killed, the sexes of the cattle were noted. The faeces and livers of the cattle were thoroughly examined for eggs and adult of Fasciola species respectively. The livers were examined by making length wise incisions of the ventral side of the liver in such a way that the bile duct is cut open. Fasciola species were easily identified based on morphological characters such as shape and size adopting the method of Urquhart et al. (1996). Based on these characters, they were classified as F. hepatica (relatively small sized) and F. gigantica (relatively large sized and more leaf like).

3.3 Laboratory diagnosis

Faecal samples collected from the rectums of 165 cattle from private abattoir and 740 from public abattoir were transported to the laboratory in tightly closed universal bottles. In the laboratory, 2g of faecal samples were mixed thoroughly (using a stirring device) with 20ml of normal saline into a container and the faecal suspension was filtered through 80-mesh sieve into another container. The filtered material was poured into a test tube and it was allowed to sediment for five (5) minutes. The supernatant was discarded leaving the sediment at the bottom of the test tube; a small quantity of the sediment was scooped with the scapular and placed on a sterile slide. One drop of iodine stain was added to the slide (to make the eggs more visible) and it was viewed under binocular microscope using X 40 magnification. The eggs were identified into various species of Fasciola using Chessbrough, 1987; Arora and Arora, 2010 identification guides.

The intensity of the fluke infection (fluke burden) was also carried out and the infected liver were classified according to the total number of worms recovered per liver into light (1-20), medium (21-50) and heavy (>50) (Ekwunife and Eneanya, 2006). Data obtained were analysed using Chi-square (χ²) at 5% level of significance using statistical package for social sciences (SPSS) version 20.0.

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