Some Observations on Field Cases of Facial Eczema: Liver Pathology and Determinations of Serum Bilirubin, Cholesterol, Transaminase and Alkaline Phosphatase

Chronic pithomycotoxicosis associated with obstructive rhinopathy in sheep

Pithomycotoxicosis (facial eczema) is a seasonal hepatogenous photosensitization of sheep caused by the ingestion of sporidesmin contained in the spores of the fungus Pithomyces chartarum. We describe 4 cases of obstructive rhinopathy associated with chronic pithomycotoxicosis naturally occurring in the north of Spain. Sheep were 5 to 7 years old and Latxa breed. A detailed clinical study was conducted together with computerized tomography examination and completed by necropsy and histopathology. All sheep developed a permanent narrowing of the nasal lumen close to the nostrils causing inspiratory dyspnea and snoring. Computerized tomography demonstrated a significant increase of soft tissue in the rostral nasal cavity. Elevated gamma-glutamyl transferase, alanine aminotransferase, and lipase were noted on serum biochemistry. At necropsy, liver atrophy and fibrosis associated with chronic pithomycotoxicosis was identified in 3 of the sheep. All sheep had whitish elevations and rough surfaces on the alar folds and areas adjacent to the nasal surfaces. Histopathologic assessments, which included histochemical and immunohistochemical techniques, of the nasal lesions identified moderate to severe arteriosclerosis in 21.5% to 61.9% of the small arteries evaluated with surrounding fibrosis and edema. No changes associated with hypersensitivity reactions were found. These lesions were similar to the ones described in blood vessels of the liver in chronic pithomycotoxicosis and in our cases. The results of this study suggest a direct action of the sporidesmin on the rostral nasal cavity. Further studies are needed to analyze the impact of the sporidesmin on the sheep nasal mucosa.

Plant and Fungal Hepatotoxicities of Cattle in Australia, with a Focus on Minimally Understood Toxins

Plant- and fungus-derived hepatotoxins are a major cause of disease and production losses in ruminants in Australia and around the world. Many are well studied and described in the literature; however, this is not the case for a number of hepatotoxicities with economic and animal welfare impacts, such as acute bovine liver disease (ABLD), brassica-associated liver disease (BALD) and Trema tomentosa, Argentipallium blandowskianum and Lythrum hyssopifolia toxicity. Additionally, significant overlap in the clinical presentation and pathology of these conditions can present a diagnostic challenge for veterinarians. This review summarizes the current and most recently published knowledge of common plant- and fungus-associated hepatotoxins affecting cattle in Australia, with a focus on the mechanisms of toxicity and distinguishing diagnostic features. Consolidation of the current understanding of hepatotoxic mechanisms in cattle provides insight into the potential mechanisms of lesser-known toxins, including cellular and subcellular targets and potential metabolic pathways. In the absence of specific etiological investigations, the study of epidemiological, clinical and pathological features of hepatotoxicity provides valuable insights into potential toxic mechanisms and is integral for the successful diagnosis and management of these conditions.

Bile duct lesions associated with turnip (Brassica rapa) photosensitization compared with those due to sporidesmin toxicosis in dairy cows

Cattle grazing turnips or other brassica forage crops occasionally develop hepatogenous photosensitization. In New Zealand, cases of bovine photosensitization associated with such crops frequently occur during late summer and fall, and this coincides with the facial eczema (sporidesmin toxicosis) "season." Clinical chemistry findings in acute photosensitization cases associated with both brassica and facial eczema include marked serum elevations in γ-glutamyl transferase and glutamate dehydrogenase activities. Distinctive bile duct lesions of "subacute" turnip photosensitization in 2 cows, comprising microscopic cholangiectasis with concentric periductal fibrosis of small bile ducts, and a spectrum of changes from bile duct necrosis progressing to obliterative sclerosis are described. These bile duct lesions are compared with those in 3 cases of "subacute" facial eczema in adult cows, where medium-sized and larger ducts tend to be involved and bile duct hyperplasia and portal fibrosis are more prominent, often leading to bridging between neighboring portal triads.

Urinary excretion of immunoreactive sporidesmin metabolites in sheep in relation to factors influencing susceptibility to sporidesmin intoxication

AIM

To study the urinary disposition of orally administered sporidesmins A and D in sheep and identify factors influencing their kinetics, particularly the influence of breeding for resistance and susceptibility to sporidesmin, the mycotoxin responsible for the hepatogenous photosensitisation, facial eczema.

METHODS

A competitive ELISA was used to monitor urinary output of immunoreactive metabolites after the intraruminal administration, to female Romney sheep, of either sporidesmin A or sporidesmin D, the nontoxic analogue. Preliminary characterisation of metabolites was carried out using HPLC with fractions monitored by ELISA.

RESULTS

Maximum urinary excretion rates of immunoreactive metabolites occurred 2-8 h after dosing with sporidesmin D and 15-30 h after dosing with sporidesmin A. Sporidesmin D caused no liver injury, as detected by changes in serum enzyme activity, while the liver injury caused by sporidesmin A was greatest for the sheep with the highest cumulative output of metabolite. When sporidesmin D was administered in two separate doses to sheep bred for either resistance or susceptibility to facial eczema, the variability of metabolic output between sheep within groups was much less after the second dose. The mean urinary metabolite excretion was greater for the susceptible than the resistant sheep but the difference was not significant. Potentiation (caused by pre-administration of small doses of sporidesmin A) resulted in a more severe reaction to the dosed sporidesmin A. Urinary output of metabolite was less in the potentiated than in the unpotentiated sheep. When resistant and susceptible sheep were dosed with sporidesmin A after potentiation there was no difference between them in their cumulative totals or excretion rates of immunoreactive metabolites. However, the volume of urine produced by the susceptible sheep was lower and less variable than the resistant sheep and consequently the concentration of their urinary metabolites was higher. Preliminary ELISA examination of HPLC-fractionated urine from a sheep dosed with sporidesmin A indicated the presence of several metabolites of sporidesmin.

CONCLUSION

Sporidesmin A and metabolites are rapidly excreted in urine but not as rapidly as sporidesmin D and its metabolites. Only minor differences between sheep bred for resistance and susceptibility were seen. Potentiation caused a more severe reaction to sporidesmin A and less urinary excretion of the sporidesmin and its metabolites.

CLINICAL RELEVANCE

This work is part of a programme with the aim of identifying FE-resistant animals without the need for sporidesmin dosing.

Apoptosis induced in macrophages and T blasts by the mycotoxin sporidesmin and protection by Zn2+ salts

Incubation of 48 h concanavalin A stimulated spleen cells (T blasts) and murine peritoneal macrophages with the mycotoxin sporidesmin results in DNA fragmentation characteristic of apoptosis. Morphological changes, particularly condensed chromatin, observed following incubation of these cells with sporidesmin and the immunotoxin gliotoxin and related epipolythiodioxopiperazines (ETP) also show changes characteristic of apoptosis. The presence of Zn2+ salts in the culture medium at concentrations non toxic to the cells over the time period studied protects against DNA damage and morphological change. Interaction between Zn2+ and the reduced form of a simple ETP compound assessed by spectral changes demonstrated the formation of a weak complex between the two molecules. Complex formation between zinc and thiol however was insufficient to prevent oxidative damage to plasmid DNA in vitro by inhibiting auto-oxidation of the reduced ETP compound because of the looseness of the interaction. Cd2+, which appears to form a tighter complex with the dithiol does inhibit cleavage of plasmid DNA. These results establish that the toxicity of sporidesmin may be due in part to its ability to induce apoptosis or programmed cell death in sensitive cells. In addition the immunotoxin gliotoxin and related compounds have now been shown to induce the same characteristic morphological changes in cells of haemopoietic origin. The inhibition of apoptosis induced by ETP compounds by Zn2+ appears to be due to direct inhibition of apoptosis rather than Zn2+ acting as an antioxidant. These results demonstrate the inhibition of apoptosis induced by ETP compounds by Zn2+ and suggest an alternate explanation for the known prophylactic effect of Zn2+ on sporidesmin induced tissue damage.

Photosensitization of albino rats fed on lucerne-protein concentrate

1. The photosensitizing effect of leaf-protein concentrate (LPC) prepared from lucerne (Medicago sativa) was demonstrated when it was included in the diet of albino rats at concentrations between 40 and 480 g/kg diet.

2. Skin lesions of varying severity up to the sloughing of ears and tails occurred when such rats were illuminated with natural daylight through window-glass or with simulated daylight from a bank of lamps having emission maxima at 410, 437 and 660 nm and with approximately 4% of the energy of summer sunlight.

3. Protein concentrates prepared from ryegrass (Lolium multiforum) and a crude chlorophyll extract of spinach (Spinacea oleracea) did not cause these effects.

4. Extracts from blood plasma and livers of rats given lucerne LPC contained pheophorbide-a and two other unidentified green pigments, but no detectable phylloerythrin or chlorophyll. Extracts from the blood of rats given ryegrass LPC had no detectable pheophorbide or other chlorophyll-derived pigments.

5. The lucerne LPC given to the rats contained relatively large amounts of pheophorbide-a among a variety of pigments. The ryegrass LPC and the spinach extracts had only small amounts of this pigment relative to the other chlorophyll-type pigments.

6. These findings indicate that pheophorbide-a and related pigments are the agents responsible for the photosensitization of the rats. Possible explanations of their presence in lucerne LPC are discussed.

Location of liver injury and extent of bilirubinaemia in experimental liver lesions

Reports on experimental hepatotoxicities in domestic animals were reviewed in order to investigate the relationship between the location of liver lesions and hyperbilirubinaemia. A purely centrilobular lesion tends to produce little effect on bilirubin concentration in the circulation. A mild to moderate hyperbilirubinaemia is predictable if a centrilobular lesion is extensive enough to include cells of the outer zones, however, even an apparently mild periportal liver lesion, but one that affects the integrity of cell membranes, results in a marked rise in bilirubin concentration in the circulation.

Phototoxic syndrome induced in mice by rice cultures of Penicillium viridicatum and exposure to sunlight

A hepatogenous phototoxic syndrome was induced in mice by the feeding of rice cultures of P. viridicaunn and exposure to sunlight. The pathologic changes in the livers and skin were similar to those described in facial eczema of sheep in New Zealand and Bermuda-grass and alfalfa-hay toxicoses in the United States of America. The phototoxic syndrome was characterized by congestion of the pinna followed by erythema and edema of the cars, muzzle, paws, and tail, occasionally accompanied by alopecia. In some mice the tip of the ears became gangrenous and sloughed. Keratitis and keratoeonus leading to blindness occurred. The incidence of phototoxic reactions was higher in older mice and in those subjected to delayed exposure to sunlight. Aspermatogenesis and formation of syncytial spermatids occurred in some mice.

A HEPATOGENOUS PHOTOSENSITIVITY DISEASE OF CATTLE. II. HISTOPATHOLOGY AND PATHOGENESIS OF THE HEPATIC LESIONS

The progressive development of the hepatic lesions which occurred in an alfalfa hay-induced photosensitivity disease of cattle was studied by means of multiple liver biopsies from 20 animals and by necropsy of 7 animals killed at different stages of the disease.

Lesions of visceral organs were confined to the liver and biliary system. The hepatic lesions were characterized by a diffuse, acutely developing cholangitis and pericholangitis leading to occlusion of the small ducts. The chief sites of involvement were interlobular ducts of small and medium size. Subsequent proliferation of bile ducts and connective tissue in the portal tracts occurred in proportion to the intensity and duration of the cholangitis, but was never extreme. The toxin causing these lesions is unknown, but since they are confined almost exclusively to the biliary tract it can be speculated that it is concentrated and excreted via biliary secretion without being adequately detoxified in the liver.

The hepatic lesions of the alfalfa hay-induced disease in catle are strikingly similar to those observed in “facial eczema” of sheep. There is little similarity of the lesions to those observed in the other major hepatogenous photosensitivity diseases.