Liver fluke:- Fasciolosis is a parasitic disease of Cattle, Buffalos, Sheep, Goats, Horses, Wild ruminants and Human caused by Liver fluke and affecting the animals at any stage of their life. The causative organism, Fasciola, is a trematode belonging to the sub-class deginea which is commonly known as Liver fluke that infect the bilary-ducts.
Fasciola gigantica is responsible for the disease in tropical regions while Fasciola hepatica is the causative agent in temperate regions and high land Ares and the disease has been shown to be the most wide spread and most destructive parasitic disease of farm animals.
Liver fluke is also a zoonosis linked to Fasciola hepatica, which affects man by chance. Humans may get infected with Liver flukes by ingesting aquatic or marshy plants such as water cress contaminated with the metacercaria of the parasite. The World Health Organization (1995) had reported that Liver fluke is an impotent public health problem in many parts of the world and that the estimated number of people affected is 2.4 million.
Losos (1995), identified three (3) partially overlapping clinical syndromes observed in cattle and small ruminates (which depend on the number of flukes invading the animal tissues and susceptibility of the animals) as:- Acute- which occurs due to the presence of Liver fluke in the Liver fluke and is characterized by lethargy and occasionally jaundice, depression or death in some cases. Chronic-fascolosis, which is essentially a wasting disease with the presence of flukes in the bile-duct and characterized by debility and anemia with sub-cutaneous edema on the lower portion of the abdomen, face and thorax. Sub-acute Liver fluke is characterized by anemia caused by the young adult flukes emerging from the Liver fluke into the bile duct.
Cattle in Nigeria have been greatly affected with Liver fluke thereby causing decrease in weight gain, reduce milk yield, unthriftiness, rough hair coat and huge economic loses. The annual loss to the farmer due to livers condemned at meat inspection in Britain was calculated to be ₤ 50 M, while the World Association for the Advancement of Veterinary Parasitology reported that 700 million cattle are exposed to Liver fluke annually and the economic loss is $3,210 x 109 (WAAVP, 2005).
Apart from these economic losses, there is also the problem of the diagnosis or recognition of the causative parasites at the right time.
The currently used method for the diagnosis and confirmation of Fasciola in Yola and Nigeria generally is the traditionally/coprological method, as well as the post-mortem Liver fluke examination.
Research conducted at the Yola modem Abattoir showed that the prevalence rate of Bovine Liver fluke decreased only from 14.7%- 5.13% (Adole, 1999; Damwesh, 2006). This is similar to other reports from Zimbabwe where the prevalence rate also reduced only from 46.3% (Chambers, 1987) - 37.1%
( Pfukenyi and Mukaratirwa, 2004) for the five (5) major abattoirs.
STATEMENT OF THE PROBLEM OF LIVER FLUKE
The direct loss cause by Liver fluke is the condemnation of affected Liver fluke at the meat inspection stage, which normally follows chronic inflammation of the Liver fluke and bile duct.
The traditional diagnosis of Liver fluke infections is by detection of eggs in faeces or flukes in the Liver fluke bile duct postmortem. Detection of eggs in faeces is the routine diagnostic procedure for live animals but the method is cumbersome and laboratory intensive and sensitivity can be as low as 30% in animals shading small number of eggs.
In addition, the method is incapable of detecting early infection because eggs do not appear in faces until at least 70 days post- infection. In contrast, Liver fluke specific antibodies are detectable in the serum of most animals by 14 days post infection.
A number of sensitive and specific serological tests for diagnosing infection have been described in recent years culminating in the commercial availability of ELISA kit for Liver fluke detection. An example is Institute pourquier manufacturing kit for indirect ELISA based on f2 antigen that is capable of detecting antibodies of Fasciola hepatica or Fasciola gigantica in milk and serum from infected cattle. Furthermore, the manufacturer claims that the ELISA can be used to estimate prevalence of infection in dairy herds for testing milk sample.
SIGNIFICANCE/JUSTIFICATION OF THE RESEARCH OF LIVER FLUKE
The problem with the use of faecal analysis for the identification of Liver fluke infection, as already stated, is due to limited accuracy and false negatives caused by low sensitivity which can be due to the fact that during the migration phase, immature worms passing through the parenchyma do not lay eggs. In addition, the method is tedious and time wasting and flukes are detected as late as 10-11 weeks post infection.
With these limitations, the use of ELISA method is therefore justified because it is more sensitive. This was demonstrated in France when 1303 heifers were subjected to faecal examination and specific ELISA’S were performed on sera samples at the same time. Results showed that cattle shedding eggs were specific in only 20% of the herd while specific antibodies from ELISA) gave 93%.
The use of ELISA also allows early diagnosis of Liver fluke, which is necessary for prompt treatment before irreparable damage (or the development of pathological lesions) to the liver, occurs hence serological test are the most dependable diagnostic methods.
The early detection of Fasciola infection was also confirmed by Leclipteux et al.(1998) who reported detection of the presence of infection in animals six (6) days after infection. It was discovered in Ovine experimental Liver fluke that antigenaemia can be detected 1 week after infection where as positive antibody values were obtained from the 2nd week after; Almazon infection and early detection of infection is possible immediately after the first week of infection. The use of blood sample for ELISA also gives a good opportunity to use these sera samples to look for other pathogens.