Heliotropium europaeum poisoning of sheep with low liver copper concentrations and the preventive efficacy of cobalt and antimethanogen

The aetiology, prevalence and morbidity of outbreaks of photosensitisation in livestock: A review

BACKGROUND

Photosensitisation is a clinical condition occurring in both humans and animals that causes significant injury to affected individuals. In livestock, outbreaks of photosensitisation caused by ingestion of toxic plants are relatively common and can be associated with significant economic loss.

OBJECTIVES

The agents that are most commonly implicated in outbreaks of photosensitisation have not been formally investigated on a global scale. To address this question, a systematic review of the literature was undertaken to determine the most common causative agents implicated in outbreaks of photosensitisation in livestock in Australia and globally, as well as the prevalence and morbidity of such outbreaks.

METHODS

A systematic database search was conducted to identify peer-reviewed case reports of photosensitisation in livestock published worldwide between 1900 and April 2018. Only case reports with a full abstract in English were included. Non peer-reviewed reports from Australia were also investigated. Case reports were then sorted by plant and animal species, type of photosensitisation by diagnosis, location, morbidity and mortality rate and tabulated for further analysis.

RESULTS

One hundred and sixty-six reports qualified for inclusion in this study. Outbreaks were reported in 20 countries. Australia (20), Brazil (20) and the United States (11) showed the highest number of peer-reviewed photosensitisation case reports from this analysis. Hepatogenous (Type III) photosensitisation was the most frequently reported diagnosis (68.5%) and resulted in higher morbidity. Panicum spp., Brachiaria spp. and Tribulus terrestris were identified as the most common causes of hepatogenous photosensitisation globally.

CONCLUSIONS

Hepatogenous photosensitisation in livestock represents a significant risk to livestock production, particularly in Australia, Brazil, and the United States. Management of toxic pastures and common pasture weeds may reduce the economic impact of photosensitisation both at a national and global level.

Acute intoxication by Crotalaria retusa in sheep

Acute intoxication by seeding Crotalaria retusa occurred during the dry season, in a flock of 80 sheep, in the semi-arid region of the state of Paraiba, northeastern Brazil. Anorexia, severe depression, mild jaundice, incoordination and recumbence were observed in 16 sheep that died within 12 h. At necropsy the liver had a nutmeg appearance. Seeds of C. retusa were found in large amounts in the rumen of the dead animals. Histologic lesions of the liver were characterized by centrilobular necrosis. Seeds of C. retusa were given to six sheep at doses of 2.5 (two sheep), 5, 10, 20 and 40 g/kg bw (one sheep for each dose). Sheep ingesting 5-40 g/kg bw were killed when moribund, 38-120 h after the start of the administration. Clinical signs and gross and histologic lesions were similar to those observed in field outbreak. The seeds used in the experiment contained 1.4% of monocrotaline. It is concluded that hungry sheep can be affected spontaneously by acute monocrotaline intoxication when they ingest large amounts of C. retusa seeds in a short period of time.

Intoxicação espontânea por Senecio brasiliensis (Asteraceae) em ovinos no Rio Grande do Sul

Descreve-se a ocorrência de um surto de intoxicação espontânea por Senecio brasiliensis em ovinos em um estabelecimento do município de Mata, Estado do Rio Grande do Sul, em meados de janeiro de 1997. De um total de 94 ovinos, 51 (54,25%) animais adoeceram e 50 (53,2%) morreram. Esse rebanho permaneceu durante aproximadamente 7 meses (de junho de 1996 a janeiro de 1997) em piquetes de pastagem nativa onde havia grande quantidade de S. brasiliensis. O quadro clínico manifestado pelos animais afetados consistia em fotossensibilização, emagrecimento progressivo, apatia, fraqueza, perturbações neurológicas como depressão, andar a esmo e desequilibrado, icterícia e hemoglobinúria. Houve melhora das lesões de pele naqueles ovinos que desenvolveram fotossensibilização hepatógena depois que foram retirados do sol. As principais lesões macroscópicas observadas em 9 dos 10 ovinos necropsiados incluíam fígado diminuído de tamanho, firme, difusamente marrom amarelado ou esverdeado, com quantidades variáveis de nódulos de 1-3 mm de diâmetro, bem circunscritos, salientes na cápsula, amarelados, distribuídos aleatoriamente por todo o parênquima. A vesícula biliar estava repleta e preenchida por bile verde escura e espessa. Havia também derrames cavitários (hidropericárdio e ascite). Crise hemolítica aguda fatal associada à intoxicação crônica hepatógena por cobre foi observada em cinco ovinos. Além das lesões hepáticas macroscópicas já mencionadas, foi observada icterícia generalizada da carcaça, rins tumefeitos, friáveis, difusamente escurecidos ou com fino pontilhado enegrecido; a urina era marrom escura (hemoglobinúria). As principais lesões microscópicas foram observadas no fígado e consistiam em hepatomegalocitose, proliferação de ductos biliares (hiperplasia ductal) e fibrose periportal moderada acompanhada de infiltrado inflamatório mononuclear. Macrófagos carregados de pigmento acastanhado formavam aglomerados nas tríades portais ou estavam dispersos entre os hepatócitos remanescentes. O material armazenado no citoplasma desses macrófagos correspondia a ceróide e cobre, positivo nas técnicas de PAS e rodanina, respectivamente. Nos rins de cinco animais, havia nefrose hemoglobinúrica caracterizada por degeneração e necrose do epitélio tubular, presença de hemoglobina e hemossiderina no citoplasma das células epiteliais dos túbulos contorcidos e cilindros de hemoglobina na luz tubular. Evidência morfológica de encefalopatia hepática incluía degeneração esponjosa (status spongiosus) da substância branca do encéfalo. Achados ultra-estruturais no fígado incluíam graus variáveis de degeneração hepatocelular caracterizada pelo acúmulo de numerosas gotas lipídicas no citoplasma das células hepáticas e presença de lisossomos carregados de material eletrodenso que, na maioria dos casos, correspondia à lipofuscina-ceróide. Adicionalmente, havia discreta dilatação do retículo endoplasmático rugoso e moderada hiperplasia do retículo endoplasmático liso em algumas regiões do citoplasma dos hepatócitos. No epitélio dos túbulos contorcidos proximais do rim foi observado edema intracelular e diversas alterações mitocondriais de caráter degenerativo que incluíam tumefação, desorganização e ruptura das cristas, matriz finamente granular, acúmulo de gotículas de gordura e ruptura das membranas em alguns casos. Lisossomos contendo material fortemente eletrodenso foram observados em muitas células tubulares renais. O exame laboratorial de fragmentos de fígado e rim dos ovinos afetados revelou níveis elevados de cobre que variaram respectivamente de 369 ppm a 1248 ppm e 152 ppm a 687 ppm com base na matéria seca. O diagnóstico de intoxicação por Senecio brasiliensis baseou-se em dados epidemiológicos, clínicos, de necropsia, histopatológicos e laboratoriais.

The characteristics and causes of sheep losses in the Victorian Mallee

The extent and causes of sheep losses in the semi-arid Mallee region of north-western Victoria were assessed by interviewing the owners of 79 randomly selected farms running 241 flocks in 1987/88 and 245 flocks in 1988/89. Mean annual losses were higher in ram flocks (21%) than in ewe flocks (7%), in flocks of non-Merino sheep (rams 24%, ewes 11%, weaners 5%) than in Merino (rams 11%, ewes 6%, wethers 4%, weaners 4%) and in ewe flocks 3 or more years old (10%) than in young ewe flocks (3.5%). In flocks where losses exceeded 5%, the causes most often reported by farmers were blowfly strike (especially in Merino sheep and weaners), ewe losses in autumn close to lambing, and heliotrope (Heliotropium europaeum) poisoning. Heliotrope poisoning was considered by the authors to be the main reason for the higher losses in old ewes than in young ewes and in non-Merino sheep than in Merino sheep. Losses of ewes associated with pregnancy and lambing were considered by the authors to be often predisposed by liver damage caused by heliotrope poisoning, and high losses in non-Merino ram flocks were attributed to both heliotrope poisoning and their ability to escape through boundary fences. Reasons for continuing high losses due to enterotoxaemia are discussed. Losses due to gastro-intestinal parasites, footrot and foot abscess were low.