Studies on the Pathology of Dicrocoeliasis and Fascioliasis in the Goat I. The Histopathology of the Liver and Bile Ducts

Dicrocoeliidae Family: Major Species Causing Veterinary Diseases

This chapter analyses the taxonomic position of the Dicrocoeliidae family and several of its genera and species. The chapter reviews the biology of major veterinary disease-causing species, including Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum. All these species have indirect life cycles with two intermediate hosts: molluscs as the first host and ants, grasshoppers and lizards as the second host. Dicrocoelium dendriticum is a widespread liver fluke found in ruminants across Europe, Asia, North Africa and North America. It can also infect humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, while D. chinensis is mainly found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite that lives in the bile ducts, gall bladder, pancreatic ducts and intestines of ruminants. It is found in Europe, Madagascar, Asia and South America. Adults of P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information on the epidemiology, pathology, clinical aspects, diagnosis, treatment, control, prevention and economic impact of Dicrocoeliosis caused by D. dendriticum, Eurytrematodosis and Platynosomiosis have been included.

Survey of Dicrocoelium dendriticum infection in imported Romani and local sheep (Ovis aries), and potential epidemiological role in Saudi Arabia

The epidemiology of parasite infection in local and imported breeds is quite an essential topic in the meat industry and human health. This study aims to determine the prevalence of Dicrocoelium dendriticum in local sheep breeds (Naemi, Najdi, and Harri) and imported breeds from Romania (Romani breed) and the epidemiology of the infection in Saudi Arabia. Morphological description, the relationship between dicrocoeliasis and sex, age, and histological changes were also presented. A total of 6845 slaughtered sheep at Riyadh Automated slaughterhouse were investigated and followed up for 4 months between 2020-2021. It included 4,680 local breeds and 2,165 imported Romanian breeds. Fecal samples and livers and gallbladders from slaughtered animals were examined for apparent pathological lesions. The results indicated that the infection rate in slaughtered animals was 10.6% in imported Romani sheep and 0.9% in the local Naeimi breed. After identifying the parasite morphologically, negative results were obtained from examining feces, gallbladders, and livers of Najdi and Harry sheep breeds. The mean number of eggs per 20 µL/gallbladder was low (72.78 ± 17.8: 76.11 ± 5.07), medium (334.59 ± 90.6: 292.91 ± 26.63), and high (1113.2 ± 22.3: 1004 ± 143.4) in imported and Naeime sheep, respectively. Significant differences were found between gender and age (males and females were 3.67% and 6.31%; > 2 years 4.39%, 1-2 years 4.22%, and 1 year 3.53%) respectively. Histopathological lesions in the liver were more pronounced. Our survey confirmed the presence of D. dendriticum in imported Romani and local Naeimi sheep, and the potential role of imported sheep in the epidemiology of dicrocoeliasis in Saudi Arabia.

Dicrocoeliidae Family: Major Species Causing Veterinary Diseases

This chapter analyses the taxonomic position of Dicrocoeliidae family and several of its genus and species. The biology of the major species causing veterinary diseases such Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum, has been reviewed. All these species have an indirect life cycle, involving two intermediate hosts (molluscs as first and ants, grasshoppers and lizards as second). Dicrocoelium dendriticum is a very widespread hepatic trematode in the ruminants of many countries in Europe, Asia, North Africa and North America, even affecting humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, whilst D. chinensis has mainly been found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite whose adults live in ruminant bile ducts, gall bladder, pancreatic ducts and intestines in Europe, Madagascar, Asia and South America. Adult P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information about the epidemiology, pathology, clinical aspect, diagnosis, treatment, control, prevention and economic impact mainly of Dicrocoeliosis produced by D. dendriticum, as well as of Eurytrematodosis and Platynosomiosis, has been included.

Field and experimental studies onDicrocoelium dendriticumand dicrocoeliasis in northern Spain

The transmission, control and the relationship betweenDicrocoelium dendriticumand its definitive (sheep and cattle) and intermediate (molluscs and ants) hosts under natural and experimental conditions are described. Eleven species of molluscs and four of ants were found infected with larvalD. dendriticumin León province, north-west Spain. Infected ants were observed between April and November and in tetania at 7.5–26.9°C. The highest shedding of eggs by sheep and cattle was detected in winter. Two treatments applied in November and January were the most effective. In experimentally infected molluscs, the parasite was not visible under the stereomicroscope, at least until 50 days post-infection (p.i.). The prepatent period in experimentally infected lambs was 49–79 days p.i. The number of eggs per gram increased with the days p.i. and the parasite burden. The aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transpeptidase, leukocyte and neutrophil values of infected lambs increased, but those of lymphocytes decreased. Using the enzyme-linked immunosorbert assay technique, the IgG antibody response to excretory–secretory and somatic antigens ofD. dendriticumwas positive from day 30 p.i., although the maximum antibody levels were observed on day 60 p.i. The number of worms per lamb ranged between 30 and 2063. Cholangitis and cholangiectasia of the septal bile and hepatic ducts were observed. The best enzymatic systems for adult and larvalD. dendriticumcharacterization were lactate dehydrogenase, glucose phosphate isomerase and phosphoglucomutase. Genetic variability of adultD. dendriticumwas high using the random amplified polymorphic DNA technique.

Pathological and immunohistochemical study of the liver and hepatic lymph nodes in goats infected with one or more doses of Fasciola hepatica

Lesions produced by Fasciola hepatica in the liver, gall-bladder and hepatic lymph nodes (HLNs) of four groups of five goats are described; in addition, the distribution of CD3+ T lymphocytes and IgG-lambda light chain-bearing cells was analysed in the hepatic lesions and HLNs. One group of goats received a single oral dose of metacercariae, but the other four groups received four or five doses at different intervals over a period of 11 weeks. Animals that survived were killed 53-55 weeks after the first infective dose. Goats were more susceptible to multiple doses than to a single dose, even when the total number of metacercariae was the same. This greater susceptibility was manifested by the occurrence of deaths and the severity of hepatic lesions. CD3+ lymphocytes were sparse in the infiltrate surrounding the acute migratory tracts, suggesting inhibition of the local cell-mediated immune response. Goats with numerous hepatic calcareous granulomas showed the most severe hepatic damage, including marked cirrhosis, with a striking infiltrate of CD3+ T lymphocytes and lambda IgG- plasma cells, replacing extensive areas of hepatic parenchyma, in which hypertrophy of the smooth endoplasmic reticulum of hepatocytes was evident. These findings were observed mainly in the goats given more than one infective dose.

Response of goats to repeated infections with Fasciola gigantica

One or two mature primary infections with Fasciola gigantica which had been removed by anthelmintic treatment resulted in a significant reduction in the number of flukes recovered from challenge infection as compared with that from controls. Characteristic lesions of fascioliasis were seen in the livers of the 3 groups, however, goats with two primary abbreviated infections prior to challenge showed more severe lesions than those of animals with one primary abbreviated infection or those of challenge controls. The former group also showed the highest serum glutamate dehydrogenase and sorbitol dehydrogenase peaks following challenge infections and pulmonary fascioliasis was encountered in one of the goats of this group. Haemoglobin concentration and packed-cell volume decreased after infection in the three groups of goats.

The influence of thyroid and testicular hormones on globule leucocytes in the rat duodenal crypt epithelium

The globule leucocyte is a cell with a wide distribution in the digestive, respiratory, biliary, urinary and genital tract epithelia of homeotherms. It occurs in the crypts of the rat small intestine and within the epithelium on the villous bases but not on the remainder of the villi. A characteristic feature of this cell is the presence of acidophilic cytoplasmic granules, 0.5 to a few micrometers in diameter. The nucleus resembles that of intraepithelial intestinal lymphocytes. In this investigation, a quantitative study was made of the effect of thyroidectomy and/or castration on the number of globule leucocytes in the duodenal crypts of immature and adult rats. In sham-operated rats, globule leucocytes were rare, occurring with a frequency of 1 or 2 per 1,000 epithelial cells. After thyroidectomy, they increased to 14--20 per 1,000 epithelial cells. Castration did not influence the number of globule leucocytes but resulted in an increase in the number, size and acidophilia of their cytoplasmic granules. In immature rats, but not in adults, castration combined with thyroidectomy enhanced the effect of thyroidectomy, increasing globule leucocyte number to 32 per 1,000 epithelial cells. Treatment of thyroidectomized-castrates with thyroxine, initiated 38 days after operation, reduced the crypt globule leucocyte population to normal, whereas treatment with testosterone did not. Growth hormone failed to influence the elevated number of globule leucocytes in thyroidectomized rats, suggesting that this action of thyroxine was not mediated via an influence on growth hormone release. Because of their similar nuclear morphology, intraepithelial crypt lymphocytes were also counted and there was no obvious relationship in the fluctuations of these two cell populations. It is suggested that the greater number of crypt globule leucocytes in thyroid deficiency may reflect changes in the intestinal secretory immunoglobulin system and this is being investigated, beginning with a study of the distribution of IgE.