Serum enzyme and hepatic changes in sheep infested with Fasciola hepatica

Techniques for the diagnosis of Fasciola infections in animals: room for improvement

The common liver fluke, Fasciola hepatica, causes fascioliasis, a significant disease in mammals, including livestock, wildlife and humans, with a major socioeconomic impact worldwide. In spite of its impact, and some advances towards the development of vaccines and new therapeutic agents, limited attention has been paid to the need for practical and reliable methods for the diagnosis of infection or disease. Accurate diagnosis is central to effective control, particularly given an emerging problem with drug resistance in F. hepatica. Traditional coprological techniques have been widely used, but are often unreliable. Although there have been some advances in establishing immunologic techniques, these tools can suffer from a lack of diagnostic specificity and/or sensitivity. Nonetheless, antigen detection tests seem to have considerable potential, but have not yet been adequately evaluated in the field. Moreover, advanced nucleic acid-based methods appear to offer the most promise for the diagnosis of current infection. This chapter (i) provides a brief account of the biology and significance of F. hepatica/fascioliasis, (ii) describes key techniques currently in use, (iii) compares their advantages/disadvantages and (iv) reviews polymerase chain reaction-based methods for specific diagnosis and/or the genetic characterization of Fasciola species.

The health and performance of cows fed large amounts of urea

From 6 weeks before calving to the end of lactation 2 groups of 8 cows were fed a ration incorporating a dairy nut containing 29 g/kg urea or an isocaloric isonitrogenous nut containing fish-meal and groundnut. During the 18 weeks after calving, concentrates were fed to appetite. 305-d yields of milk (7023 and 5796 kg) and lactose (345.7 and 273.4 kg) were significantly lower in the urea-fed cows (P< 0·05). Intakes of dry matter, metabolizable energy and digestible crude protein were similar in both groups until 18 weeks after calving when feeding according to yield commenced, but by 6 weeks after calving the urea-fed cows lost only 5% of their immediate post-calving weight compared with 7% in the controls. There was no evidence of ammonia toxicity in the urea-fed cows. Blood glucose concentrations were similar in both groups, but higher serum urea concentrations in the urea-fed cows suggested that there was poor utilization of ingested N. A model proposed by Royet al.(1977) has been used to calculate the requirements of rumen-degradable protein and undegraded protein (UDP) of the 2 groups from their energy intakes and milk yields. Between 4 and 11 weeks post-calving, dietary requirement for UDP closely matched intake of UDP. It is concluded that UDP intake was a major factor in determining the peak milk yield. Mechanisms by which the degradability of the dietary protein might influence milk yield are discussed.

Effect of the traditional medicinal plants Rhazya stricta, Balanitis aegyptiaca and Haplophylum tuberculatum on paracetamol-induced hepatotoxicity in mice

This work examines the effects of lyophilized extracts of the medicinal plants Rhazya stricta, Balanites aegyptiaca and Haplophylum tuberculatum on liver damage induced by paracetamol in mice. Rapid HPLC finger prints for some of these extracts were made. The hepatoprotective effects of the plant extracts were compared with that of the standard hepatoprotective agent silymarin. The extracts (1 g/kg) and silymarin (0.1 g/kg) were given orally for 5 consecutive days. On the last day of treatment a hepatotoxic oral dose of paracetamol (0.6 g/kg) was given, and 3 h later, the hepatic function of mice was evaluated using pentobarbitone -induced sleeping time, the concentration of reduced glutathione (GSH) in liver, and the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT) and cholesterol concentration in plasma. The livers were weighed and examined for macro- and microscopic changes. Pretreatment with R. stricta or with silymarin protected the livers of treated mice against paracetamol hepatotoxicity as evidenced by a significant improvement of the above liver function tests. B. Aegyptiaca had a relatively modest hepatoprotective activity, while H. tuberculatum was almost ineffective. Oral pretreatment of mice for 5 consecutive days with an extract of R. stricta or silymarin protected about 57% and 92% of the treated mice, respectively, against the lethal effect of paracetamol (1 g/kg). B. aegyptiaca and H. tuberculatum protected only 27% and 16% of the animals, respectively.

The effects of fascioliasis on the activities of some drug-metabolizing enzymes in desert sheep liver

Desert sheep experimentally or naturally infected with Fasciola gigantica were used to study the influence of infection on the activities of some drug-metabolizing enzymes found in the liver. The enzymes investigated were aminopyrine N-demethylase, aniline 4-hydroxylase and UDP-glucuronyltransferase. The experimental infection was confirmed histologically by detection of Fasciola eggs in faeces and by measuring the activities of sorbitol dehydrogenase (SD), glutamate dehydrogenase (GD) and aspartate aminotransferase (AST) in plasma during the course of the disease. Liver specimens from naturally infected sheep were obtained from the slaughter house. The activities of aminopyrine N-demethylase and aniline 4-hydroxylase were significantly decreased in sheep either naturally infected or during the acute stage of experimental fascioliasis (killed 5 weeks post-infection). The activity of UDP-glucuronyltransferase was decreased in naturally infected sheep and those killed 9 or 13 weeks post-experimental infection.

Hematology and clinical pathology of experimental Fascioloides magna infection in cattle and guinea pigs

The hematologic and clinico-pathologic response to Fascioloides magna infection in cattle and guinea pigs was investigated. Twelve calves (six infected and six controls) were monitored for 26 weeks after inoculation with 1000 metacercariae. All calves remained healthy and there were no significant differences in weight gains between infected and control groups. Flukes (mean = 9.2, range 1-32) were recovered from the liver and abdominal cavity of all infected calves. The only significant response observed in the complete blood counts was an eosinophilia present in the infected calves extending from Weeks 2 to 26 post-infection. There were no significant differences in serum levels of aspartate aminotransferase and only minor increases in the levels of gamma-glutamyl transferase and sorbitol dehydrogenase. A total of 48 infected and 48 control guinea pigs from three separate experiments were monitored for 16 weeks after inoculation with 20 metacercariae of Fascioloides magna. Infected guinea pigs died between 7 and 114 days after infection, and flukes (mean = 2.5, range 0-13) were recovered from the liver, abdominal cavity, lungs, thoracic cavity, skeletal muscle and subcutaneous tissue. There were no differences in weight gains between infected and control guinea pigs. Complete blood counts showed increases in white blood cells, monocyte and neutrophil counts from between the third and fourteenth weeks post-infection; however, the differences were not consistently significant. Infected guinea pigs developed a significant eosinophilia and basophilia from 2 to 16 weeks post-infection. There were no significant changes in the serum levels of alanine aminotransferase or gamma-glutamyl transferase. There was an increase in the serum levels of aspartate aminotransferase beginning at 5 weeks post-infection. The response observed in the guinea pigs was similar to that reported in sheep, suggesting the suitability of the guinea pig as a model for Fascioloides magna infection in the sheep.

Studies on naturally-occurring ovine fascioliasis in the Sudan

Haematological, biochemical and pathological changes were investigated in 214 sheep naturally infected with Fasciola gigantica in an endemic area in the Sudan together with 82 uninfected controls. Infected animals showed a clear decrease in erythrocyte counts, haemoglobin concentration and packed cell volume, a normochromic, normocytic anaemia, leucocytosis and eosinophilia. Serum concentrations of the enzymes glutamate dehydrogenase, sorbitol dehydrogenase and glutamate oxaloacetic acid transaminase were also elevated in the infected group, indicating hepatic damage. This was confirmed by histopathological changes, which comprised degenerative and necrotic changes in hepatocytes associated with haemorrhage, fibrosis, increased lobulation of the liver, mononuclear cell infiltration with haemosiderin deposition in fluke tracks and portal areas and the formation of granulomata around fluke eggs and fluke remnants. In the infected group there was slight hyperglobulinaemia and a marked hypoalbuminaemia, with a decrease in A/G ratio. A slight rise in the level of serum bilirubin was also observed.

The use of haemoglobin, packed-cell volume and serum sorbitol dehydrogenase as indicators of the development of fascioliasis in sheep

Haemoglobin, packed-cell volume and serum sorbitol dehydrogenase activity were studied in 8 groups of 3 Corriedale weaner wethers artificially infected with a range of fluke burdens. Data from haemoglobin and packed-cell volume measurements were analysed using regression procedures. All parasitised groups exhibited a decrease in haemoglobin and packed-cell volume compared with the control group. The rate of this decrease was approximately linear, and dependent on the size of the fluke burden. Prediction equations for the rates of decrease of haemoglobin and packed-cell volume in fluke-infected sheep are presented. Death occurred when haemoglobin fell below 5 g 100 ml-1, and packed-cell volume to 15%. Anaemia became profound in sheep infected with more than 346 flukes and these sheep died 56-63 days after infection. Serum sorbitol dehydrogenase activity exhibited several peaks, before and after Week 12 post-infection, when flukes should have been present in the bile ducts. Reason for the activity later than Week 12 was not clear, although stress or immune responses may contribute. Haemoglobin and packed-cell volume may be useful in predicting the size of fluke burdens when the duration of the infection is known, and may indicate that time of death of infected sheep. Sorbitol dehydrogenase is an unreliable indicator of the size or the duration of fluke burdens.

Intrahepatic vascular lesions in experimental and natural ovine fascioliasis

Using acrylic resin casts prepared from the liver vasculature and histology, subdivisions of the portal and hepatic systems stenosed as a result of experimental and natural infections of F. hepatica were identified as terminal, secondary and tertiary portal veins and central and sublobular hepatic veins; primary portal veins were also involved in the experimentally infected livers. Fewer veins tended to be involved in livers naturally-infected and they were more evenly distributed among liver lobes than in the experimental disease where most were found in the ventral lobe. Casts of both types of infection also demonstrated enlargement and tortuosity of arteries in ventral lobes and those forming the peribiliary arterial plexus, as well as showing that multiple anastomotic channels had formed. The arterial changes and anastomoses were suggested as developing to compensate for the effects of vascular stenosis. Portal vein stenosis induced experimentally was the outcome of replacement of eosinophils and oedema-like fluid present in veins around fluke tracks and of the organisation of fluke tracts impinging upon veins. During the post-migratory period of infection, stenosis became more marked, for which no adequate cause was identified. In livers naturally-infected, in addition to stenosed portal and hepatic veins, vascular channels in collagen septa in sinusoids and a slight convolution of arteries were seen.

Susceptibility of desert sheep to infection with Schistosoma mansoni of Northern Sudan

Each of two Desert Sheep was infected with 1500 cercariae of Schistosoma mansoni of Northern Sudan. Signs of infection were anorexia, soft faces, progressive weakness and loss of wool. The sheep were killed 254 and 269 days after infection. The findings were heavy infiltration of the lamina propria with inflammatory cells, numerous ova in the submucosa, hyperplasia of lymphoid tissue, oedema of the mesenteric lymph nodes, and focal pulmonary oedema and congestion. There were egg granulomas, focal necrosis, schistosomal pigment, fatty change, depletion of glycogen and reduction in the activity of adenosine triphosphatase, succinic tetrazolium reductase and glucose-6-phosphatase in the liver. In one sheep 1330 cercariae penetrated and 700 matured to produce males and females in a 5:2 ratio. In the other sheep, about one third of the cercariae penetrated and matured. The ratio of males to females was 3:1.