The experimental production of krimpsiekte in sheep with Tylecodon grandiflorus (Burm.f.) Toelken and some of its bufadienolides

Six bufadienolides were isolated from Tylecodon grandiflorus ( Burm .f.) Toelken . The paretic syndrome, krimpsiekte , could be induced in sheep either by repeated oral administration of small quantities of plant material or the intravenous injection of small quantities of certain bufadienolides . A mild to moderate, acute to subacute, multifocal cardiomyopathy was evident in sheep poisoned by both the plant and the bufadienolides .     

Cardiac glycoside poisoning in sheep caused by Urginea physodes (Jacq.) Bak. and the isolated physodine A

Urginea physodes (Jacq.) Bak., a species closely related to or possibly synonymous with U. pusilla, is described and its distribution given. Four bufadienolides were isolated from U. physodes and the approximated LD50 and cumulative effect of some of them determined in guinea pigs. The most toxic one proved to be mildly cumulative. Typical signs of acute cardiac glycoside poisoning, involving the locomotory, gastro-intestinal, respiratory and cardiac system, were seen in the field cases and/or were experimentally induced by the plant. Similar signs could also be induced by injecting the isolated bufadienolide, physodine A, to a sheep.     

Clinical development and serological antibody responses in sheep and rabbits experimentally infested with Psoroptes ovis and Psoroptes cuniculi

Psoroptes ovis of sheep origin, and Psoroptes cuniculi of rabbit origin were used in experimental infestations. In experiment I, groups of four rabbits and four sheep were infested with 50-100 mites of each isolate on the skin of the back (skin infestation, SI) or in the external auditory canal (aural infestation, AI). In rabbits, SI and AI with P. cuniculi and AI with P. ovis induced in all animals typical ear lesions and pronounced antibody reactions to P. cuniculi antigens in ELISA. After SI of rabbits with P. ovis no clinical signs were detected, no mites could be reisolated and no specific antibodies were detected. In sheep, P. ovis SI induced mange whereas AI did not induce typical clinical signs and mites could not be reisolated. In both these animal groups, ELISA revealed pronounced and comparable specific antibody reactions. After SI and AI with P. cuniculi no clinical symptoms were observed and no mites could be reisolated. Nevertheless, low levels of specific antibody were detected. In experiment II, clinical progression and antibody reactions to P. ovis SI in naive sheep were compared with sheep previously exposed to P. ovis or P. cuniculi. In both pre-exposed groups of animals, clinical signs appeared within 2 days after challenge infestation and three days earlier than in primarily infested sheep. Subsequently, no obvious difference in the clinical progression was observed between the three groups of animals. The results of this study document antigenetic crossreactivity of the two morphologically and genetically distinguishable Psoroptes species but differences in their biological behaviour and virulence which both are of epidemiological and taxonomic relevance.     

A potential krimpsiekte vaccine

Krimpsiekte, a chronic form of cardiac glycoside poisoning, is an important plant-induced intoxication of small stock in South Africa. It is caused by cumulative, neurotoxic bufadienolides, such as cotyledoside. A cotyledoside-bovine serum albumin conjugate was synthesized to immunize animals. The efficacy of the cotyledoside-conjugate in inducing an immunological response was ascertained in rabbits (n = 4) and sheep (n = 4) by determining cotyledoside antibody titres with an ELISA using cotyledoside-hen ovalbumin as antigen. The formation of anticotyledoside antibodies was induced in both rabbits and sheep following immunization with the cotyledoside-protein conjugate. Protection provided by the vaccine was demonstrated by challenging sheep (n = 4) with repeated, daily doses of cotyledoside (0.015 mg/kg) administered intravenously, commencing 45 days after the initial vaccination. One control animal died on Day 3 of the challenge period and the other was severely affected after administration of the third cotyledoside dose. The immunized ewes (n = 2) remained clinically unaffected and the challenge was suspended following six daily injections. Vaccination as a means of preventing krimpsiekte seems to be quite feasible and deserves further investigation.     

BIOCHEMISTRY OF NATURAL AND AMPROLIUM-INDUCED POLIOENCEPHALOMALACIA IN SHEEP

SUMMARY Polioencephalomalacia (PEM) induced in sheep was compared with the disease found in naturally occurring cases. Blood biochemical indicators measured were pyruvate, lactate, glucose, erythrocyte transketolase (TK) and stimulation of TK by addition of thiamine pyrophosphate (TPP effect). Faeces and rumen contents were assayed for thiaminase activity. The effect of treating affected sheep with thiamine was also noted. It was found that amprolium treatment could induce thrombocytopenia, but once the sheep became accustomed to amprolium in the diet they seemed to be resistant to this effect. In sheep receiving amprolium significant weight losses preceded the onset of clinical signs. Further weight loss continued throughout the recovery period despite removal of amprolium from the diet and treatment with thiamine. Blood glucose was variable, and was elevated only when marked clinical signs were present. Pyruvate and lactate levels showed marked variation throughout the trial. TK values were depressed and TPP effects increased well before the onset of clinical signs, although some naturally occurring cases had normal levels. Faecal thiaminase activity was negligible in all the sheep on the amprolium trial but most field cases had a high level. High faecal thiaminase was observed in about 5% of clinically normal animals from affected flocks. Depression of erythrocyte TK activity coupled with the presence of faecal thiaminase appeared to be the most reliable diagnostic biochemical parameters for PEM. Treatment of PEM affected sheep with thiamine rapidly brought the biochemical status of the animals to normal. However where advanced brain lesions were present the damage was permanent and such sheep treated with thiamine remained partially decorticate.     

Efficacy, toxicity and metabolism of imidocarb dipropionate in the treatment of Babesia ovis infection in sheep

An intramuscular dose of 1.2 mg kg-1 of imidocarb dipropionate (IMDP) was effective in controlling fatal infections with Babesia ovis in sheep. The sheep were infected by the intravenous injection of sheep blood containing B ovis. A severe recrudescence of infection occurred in most sheep 10 to 14 days after therapy but this could be controlled by a second dose of 1.2 mg kg-1 IMDP. Studies on the toxicology, residues and metabolism of IMDP showed this to be a safe dosage regimen. Transient or mild signs of toxicity were seen at 2.4 and 4.8 mg kg-1 IMDP. Severe toxicity was observed in sheep treated with 9.6 mg kg-1.     

Sunlight associated hyperthermia as a consistent and rapidly developing clinical sign in sheep intoxicated by St John's wort (Hypericum perforatum)

OBJECTIVE: To assess the usefulness of rectal temperature responses in Australian bred Merino sheep, following the oral administration of Hypericum perforatum (St John's wort), as an early indicator of Hypericum intolerance. DESIGN: Thirty-three Merino ewes were divided into three groups of 11. Each group was dosed with finely ground, dried, flowering growth stage H perforatum plant material at either 5.7, 4.0, or 2.85 g dry plant per kg live weight. This corresponded to 5.3, 3.7 and 2.65 mg hypericin per kg live weight, respectively. PROCEDURE: The sheep were dosed with a plant slurry by stomach tube and then exposed to bright sunlight for up to 5 h per day over successive days. Their clinical responses were observed and rectal temperature measured. RESULTS: Ingestion of H perforatum followed by exposure to bright sunlight frequently resulted in clinical signs attributable to skin irritation and central nervous effects, including an inappropriate increase in body temperature. A decrease in H perforatum ingestion from 5.7 to 2.85 g dry plant per kg live weight and a corresponding decrease in hypericin ingestion from 5.3 to 2.65 mg per kg live weight, was associated with a decrease in the severity of the clinical signs, including the severity of the hyperthermia. CONCLUSIONS: The rectal temperature rise in affected sheep is a reliable indicator of the early development of an adverse clinical effect. There appears to be an absolute requirement for exposure to bright sunlight before any effects of H perforatum will develop. A single dose of H perforatum remains potentially effective for up to 4 days. In the small group of Merino sheep tested a tolerance level for H perforatum, eaten at the flowering stage, of < 1% (plant wet weight) of body weight and a tolerance level for hypericin of < 2.65 mg per kg live weight, were demonstrated.     

Diagnosis of psoroptic sheep scab with an improved enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of specific antibodies against crude Psoroptes antigen. The diagnostic sensitivity was 93.7% in 191 sheep with clinical signs associated with mange. These animals originated from 29 flocks in which psoroptic mites were detected. All of 59 sheep infested with Psoroptes ovis were seropositive. Additionally, in 49% of 70 clinically unaffected sheep originating from P. ovis-infested flocks, specific antibodies could be detected, suggesting that asymptomatic infestations can be diagnosed by serology. The specificity of the ELISA was 96.5% as determined with 254 sheep originating from 44 flocks without clinical mange. Cross-reactivity in a low range was detected with selected sera of sheep with clinical chorioptic or forage mite infestations. Four sheep seroconverted 2 weeks after experimental P. ovis infestation, i.e. 2 weeks before clinical signs became obvious. After successful doramectin treatment of 14 sheep with naturally acquired P. ovis infestation, the ELISA values declined slowly but remained positive in seven cases beyond 17 weeks.     

Arthritis associated with ovine progressive pneumonia

Chronic nonsuppurative arthritis developed in carpal and tarsal joints of border Leicester sheep that were naturally or experimentally infected with ovine progressive pneumonia (OPP) virus. Clinical signs of arthritis began at 1 to 6.2 years of age (1 to 5.7 years after inoculation of OPP virus) and slowly progressed in severity until the sheep died or were killed. The joint lesions were characterized by edema, hyperemia, hyperplasia, and necrosis of the synovial membrane; by necrosis and erosion of articular bone; by necrosis and fibrosis of subchondral bone; and by extensive periarticular fibrosis. The OPP virus alone was isolated from arthritic joints. In 7 of 14 sheep, the arthritis was associated with interstitial pneumonitis induced by the virus. Therefore, it was concluded that OPP virus was the cause of arthritis in this group of sheep.     

Bur buttercup poisoning of sheep

Bur buttercup (Ceratocephalus testiculatus) has not been considered to be poisonous, but the sudden death loss of 150 ewes while grazing it prompted study of the plant. It was found that bur buttercup can be highly toxic to sheep, with a lethal dose being as little as 500 g of green plant for a 45-kg sheep. Clinical signs of bur buttercup poisoning are weakness, depression, diarrhea, labored breathing, anorexia, and occasional fever. Postmortem findings include inflammation and edema of the rumen; hemorrhage in the left ventricle of the heart; congestion of the lungs, liver, and kidneys; and excessive fluid in the thoracic and abdominal cavities.     

Toxic hepatopathy in sheep associated with the ingestion of the legume Tephrosia cinerea.

A disease known as water belly (barriga d'água), characterized by chronic progressive ascites, affects sheep in the semiarid region of northeastern Brazil. The objectives of this investigation were to study the disease and to determine its cause. Only sheep grazing for long periods in pastures where Tephrosia cinerea represents 80% to 100% of the available forage are affected. Most animals die after a clinical manifestation period of some weeks or months, but others recover when they are withdrawn from the pastures or after the first rains. At necropsy, large amounts of liquid were found in the abdominal cavity, and the liver was hard, with an irregular surface. On histology examination, the main liver lesion was chronic periportal and subcapsular fibrosis with bridging. The disease was produced experimentally in 1 sheep by the administration of large amounts of T. cinerea for 232 days. Another sheep, recovered from the spontaneous disease, had clinical signs after the ingestion of large amounts of the plant for 40 days. Seeds and leaves of the plant were examined by gas chromatography-mass spectrometry for the presence of pyrrolizidine alkaloids with negative results. It is concluded that the disease is caused by the ingestion of T. cinerea.     

Neurotoxicity in calves induced by the plant, Nierembergia hippomanica Miers var. violacea Millán in South Africa

The plant Nierembergia hippomanica var. violacea has been incriminated in field outbreaks of neurotoxicity in calves in the Free State Province. Hepatotoxicity and electrocardiogram (ECG) deviations were induced in a sheep dosed with 5 g/kg dried plant material on four consecutive days. A calf dosed with 2.5 g/kg dried plant material, on two consecutive days, did not show overt clinical changes. Voluntary ingestion of approximately 30 g/kg fresh flowering plants by a second calf resulted in nervous signs characterized by chewing motions, protrusion of the tongue, dysphagia, hypermetria, ataxia, paresis and lateral recumbency. Salivation, dehydration and cardiac irregularities completed the clinical picture. Clinical chemistry changes revealed muscle damage and increased serum urea and creatinine concentrations indicative of kidney involvement. This is the first confirmed outbreak of Nierembergia hippomanica var. violacea intoxication of stock in South Africa.     

The pathogenesis of the nervous syndrome of Phalaris aquatica toxicity in sheep

The clinical signs displayed by 96 sheep affected by the nervous syndrome of Phalaris aquatica toxicity and 10 normal sheep injected intravenously with the phalaris alkaloid, 5-methoxy dimethyltryptamine (dose range 0.01 to 5.0 mg/kg), were observed. The distributions of phalaris indole-like cytoplasmic pigments in nuclei of the brains and spinal cords of 9 naturally affected sheep were determined microscopically. Based on the relationship between clinical signs and the central nervous system nuclei involved in their production, the distribution of phalaris indole-like pigments, and the pharmacology of dimethylated tryptamines, it is suggested that the nervous syndrome induced by Phalaris aquatica results from a direct action of phalaris alkaloids upon serotonergic receptors in specific brain and spinal cord nuclei.     

Paratuberculosis in sheep: its possible role in the epidemiology of paratuberculosis in cattle

A total of 50 sheep originating from 15 Dutch farms with a known paratuberculosis infection in their cattle herd, but with no history of paratuberculosis infection in their sheep flock, were examined for infection with Mycobacterium avium subsp. paratuberculosis (Map). The sheep had been grazing on the same pastures as the cattle or on pastures fertilised with manure from these cows. The sheep were screened for paratuberculosis by serum biochemistry, serology and intradermal skin tests. At necropsy they were examined macroscopically, microscopically and bacteriologically for paratuberculosis.From 10 sheep, originating from eight flocks, Map could be isolated from various tissues but not from the intestinal contents, after an incubation period of 2.5-4 months. Six of these culture-positive sheep had no macroscopic signs of paratuberculosis at necropsy. Seven sheep were Map culture negative but showed macroscopic and microscopic lesions consistent with a paratuberculosis infection. Results of serology and skin tests did not correlate with the results of bacteriological culture. Serum concentrations of calcium, albumin and total protein of the infected, suspected and negative sheep were not different. These results indicate that a substantial number of the sheep examined were infected with Map. Even though this bacterium was not isolated from their faeces, the possibility that these sheep could have been shedding Map with their faeces below detection level or at a later stage of the disease cannot be eliminated. Map infected sheep should, therefore, be considered as a possible factor in the epidemiology of with Map infected cattle herds in The Netherlands. At necropsy bacteriological culture of Map should be performed on a routine basis to improve the diagnosis of paratuberculosis in sheep.     

内蒙古荒漠草原区分采食成分的最佳蜡层指示剂组合

应用蜡层指示剂法对内蒙古荒漠草原绵羊采食物种的含量和比例进行计算时,需要确定采食物种饱和链烷、长链醇和长链脂肪酸划分采食物种的准确性和可能性。因此通过气相色谱法,测定了采食物种的饱和链烷、长链醇和长链脂肪酸的含量;利用主成分分析和方差分析方法对内蒙古荒漠草原不同放牧率下如何更好划分采食植物的最佳蜡层指示剂组合进行了探讨。结果表明:蜡层指示剂方法可应用于内蒙古荒漠草原采食植物的划分,其中饱和链烷+长链醇的指示剂组合最适用于内蒙古荒漠草原采食植物的划分,并为内蒙古荒漠草原的采食量和采食比例的估测提供了计算模式和理论依据。     

Emory milkvetch (Astragalus emoryanus var emoryanus) poisoning in chicks, sheep, and cattle.

A severe outbreak of Emory milkvetch poisoning in cattle and sheep occurred near Roswell, New Mexico, in the spring of 1975. Mortality averaged 2% to 3% and morbidity averaged 15% to 20%. Emory milkvetch collected from the infested area contained miserotoxin measured as 5 to 9 mg of NO2/g of plant (dry weight). Chicks fed extracts of Emory milkvetch showed toxic signs when fed one dose as 300 mg of NO2/kg of body weight, and died within 5 to 8 hours when fed milkvetch as 400 mg of NO2/kg. A sheep fed Emory milkvetch for 7 days in the form of 38 mg of NO2/kg/day developed signs of nitro poisoning on the 7th day. Cattle were poisoned or died when fed Emory milkvetch as 12 to 20 mg of NO2/ig for several days. The toxic signs observed in the field and under experimental conditions were similar.     

Brain lesions of naturally occurring pregnancy toxemia of sheep.

The neuropathology and biochemical features of 17 sheep with clinical signs and gross necropsy features of naturally occurring pregnancy toxemia were retrospectively evaluated. The sheep ranged in age from 3 to 6 years and were of seven different breeds and three breed crosses. Thirteen sheep (case Nos. 1-4, 6-9, 11-14, 16) showed astrocytic nuclear swelling, hypertrophy and proliferation, and cerebrocortical neuronal necrosis. Seven of these sheep had Purkinje cell necrosis (case Nos. 2, 3, 6, 11, 12, 14, 16), and seven had vacuolation of cerebral and cerebellar sub-cortical white matter (case Nos. 1-4, 9, 12, 13). The neuropathologic features were similar to those of naturally occurring hypoglycemia of human beings and experimentally induced hypoglycemia of primates and the rat. The lesions seen in the sheep studied may have been caused by cerebral hypoglycemia, but data for blood or cerebral glucose concentrations were not available.     

Detection and clinical evolution of scrapie in sheep by 3rd eyelid biopsy

The goal of this article was to characterize the clinical evolution of scrapie in naturally affected sheep. Eighteen sheep with scrapie diagnosed by examination of 3rd eyelid biopsy and 12 control ewes were studied throughout the duration of their disease. Diagnosis was confirmed postmortem by histopathologic, immunohistochemical, and Western blot analysis of nervous tissue. Complete clinical examinations were performed every 2 weeks for each animal, of which 3 clinical examinations per animal are reported. Those clinical signs that showed a significant frequency within the corresponding clinical examination were considered representative of each stage of the disease (ie, early, middle, and late). The representative clinical signs for the early stage were hypoesthesia in the limbs, alteration of mental status, and a body condition score <3. Remarkably, hypoesthesia in the limbs was one of the 1st signs appearing during the early clinical stage in the affected animals, even before the appearance of other signs. For the middle stage, representative signs were the same as those for the early stage, together with hyporreflexia in the limbs, cardiac arrhythmia, pruritus/wool loss, and the appearance of the nibbling reflex. Representative clinical signs for the late stage were the same as those for the early and middle stage, together with head tremors, hyperexcitability to external stimuli, ataxia or gait abnormalities, and teeth grinding. On the basis of these results, we propose the calculation of an objective clinical index that allows the differentiation among clinical stages and that could be useful for further studies. The usefulness of 3rd eyelid lymphoid tissue biopsies for sequential clinical studies in naturally scrapie-affected sheep is demonstrated.     

Susceptibility of transgenic mice expressing chimeric sheep,bovine and human PrP genes to sheep scrapie

The use of Transgenic (Tg) mice expressing chimeric sheep/mouse (Sh/Mo) prion protein (PrP) and chimeric bovine/mouse (Bo/Mo) PrP genes was evaluated as a sheep scrapie model. We also investigated the potential for the transmission of sheep scrapie to a human/mouse (Hu/Mo) PrP Tg mouse line. The Sh/Mo PrP and Bo/Mo PrP Tg Prnp(+/+) or Prnp(0/0) mouse lines were inoculated intracerebrally with brain homogenates from three sheep with natural scrapie (KU, Y5 or S2). Incubation periods were slightly shorter in Sh/Mo PrP Tg Prnp(+/+), than in non-Tg mice inoculated with KU brain homogenate. In contrast, the incubation period was significantly prolonged (p<0.05) in Bo/Mo PrP Tg Prnp(+/+) mice inoculated with KU brain homogenate. The incubation period was significantly longer in all Tg Prnp(+/+) and Prnp(0/0), than in non-Tg mice (p<0.01) inoculated withY5 brain homogenate. None of the Tg Prnp(0/0) mice inoculated with S2 brain homogenate developed clinical signs and PrP(Sc) was undetectable in their brains. These results suggested that expression of the Sh/Mo PrP or Bo/Mo PrP transgenes does not confer susceptibility to sheep prions upon mice, and thus none of the Tg mouse lines could be a suitable model of sheep scrapie. Hu/Mo PrP Tg Prnp(0/0) mice inoculated with natural and experimental scrapie or mouse prions did not develop clinical signs of scrapie and PrP(Sc) was undetectable. These results suggested that neither sheep nor mouse strains of scrapie are highly transmissible to humans.