Acute Lantana camara poisoning in a Boer goat kid

INTRODUCTION Lantana camara, a member of the Verbenaceae, is an exotic ornamental shrub that is of particular importance in South Africa as a cause of cattle intoxication in the moist eastern parts of the country. It was originally introduced from Central and South America and occurs commonly in many tropical and subtropical regions of the world. The most important toxic principle of Lantana camara is lantadene A, a pentacyclic triterpene acid. This substance has been shown to cause injury to the bile canalicular membranes, with subsequent cholestasis and hepatocellular damage. Ingestion of the plant by cattle and sheep results in secondary photosensitivity, icterus and constipation, or in some cases, diarrhoea. Two other members of the Verbenaceae, Lippia rehmannii and L. pretoriensis, also contain pentacyclic triterpene acids and may cause photosensitivity when dosed to ruminants. Reports of naturally occurring Lantana camara poisoning in goats are rare. Munyua et al. reported a case of acute L. camara poisoning in Kenya, when a group of calves, sheep and East African goats on zero-grazing were inadvertently exposed to the plant. The clinicopathological features of acute and chronic lowdose L. camara poisoning in indigenous Zimbabwean goats were investigated by Obwolo et al.. Acute poisoning was clinically characterised by anorexia, dehydration, ruminal stasis and severe icterus within 1–4 days of consuming the plant , but no photosensit isat ion occurred. The necropsy findings in this case included severe icterus, dehydration, constipation, hepatosis, distention of the gall-bladder and nephrosis. Moderate hepatosis with single-cell necrosis and bile stasis, as well as acute renal tubular necrosis, were confirmed histologically.


INTRODUCTION
Lantana camara, a member of the Verbenaceae, is an exotic ornamental shrub [2][3][4]6 that is of particular importance in South Africa as a cause of cattle intoxication in the moist eastern parts of the country [2][3][4]6 . Itwas originally introduced from Central and South America and occurs commonly in many tropical and subtropical regions of the world 6,14,15,17 .The most important toxic principle of Lantana camara is lantadene A, a pentacyclic triterpene acid [2][3][4]6,7,18 .This substance has been shown to cause injury to the bile canalicular membranes, with subsequent cholestasis and hepatocellular damage 12 .Ingestion of the plant by cattle and sheep results in secondary photosensitivity, icterus and constipation, or in some cases, diarrhoea [1][2][3][4][5]10,12,15 .Two other members of the Verbenaceae, Lippia rehmannii and L. pretoriensis, also contain pentacyclic triterpene acids and may cause photosensitivity when dosed to ruminants 4,5,13 .
Reports of naturally occurring Lantana camara poisoning in goats are rare 10 .Munyua et al. reported a case of acute L. camara poisoning in Kenya, when a group of calves, sheep and East African goats on zero-grazing were inadvertently exposed to the plant 9 .The clinicopathological features of acute and chronic lowdose L. camara poisoning in indigenous Zimbabwean goats were investigated by Obwolo et al. 10,11 .Acute poisoning was clinically characterised by anorexia, dehydration, ruminal stasis and severe icterus within 1-4 days of consuming the plant, but no photosensitisation occurred [9][10][11] .The necropsy findings in this case included severe icterus, dehydration, constipation, hepatosis, distention of the gall-bladder and nephrosis.Moderate hepatosis with single-cell necrosis and bile stasis, as well as acute renal tubular necrosis, were confirmed histologically.

CASE HISTORY
During May 1996, a farmer near Pretoria, Gauteng, reported 3 mortalities in a flock of approximately 35 Boer goats recently introduced from the Kuruman area in the Northern Cape province.Necropsy of a 5-month-old Boer goat kid revealed icterus, dehydration, an enlarged, brown liver and a distended gall-bladder with multiple subserosal petechial haemorrhages at the gallbladder neck.The kidneys were pale with a yellow, glistening appearance and bulged at the cut surfaces.Moderate, diffuse pulmonary congestion was present.The colon and rectum were impacted with putty-like faeces.No skin lesions consistent with photosensitisation were present.
Specimens of the liver, kidneys, lung and spleen were collected in 10 % buffered formalin for histology.Sections were routinely prepared and stained with haematoxylin and eosin, and Masson's trichrome 8 method for connective tissue.Hepatocytes were diffusely and moderately swollen and possessed finely granular cytoplasm, with distinct cell borders.Some cells contained large intracytoplasmic vacuoles (Fig. 1).The cell nuclei varied in size and were hypochromatic, occasionally multinucleate, with finely stippled chromatin and one or more prominent nucleoli (Fig. 1).Several of the hepatocytes contained intracytoplasmic, yellowish-green bile pigment globules.Scattered hepatocytes exhibited coagulative necrosis in which karyorrhexis, karyopyknosis or karyolysis were variably present in addition to cytoplasm condensation and hypereosinophilia (Fig. 1).Hepatic cell plates were generally disrupted and the spaces of Disse moderately dilated.Mild bile duct proliferation and portal fibroplasia were present.Inflammatory cell infiltrates, consisting mostly of small numbers of neutrophils, lymphocytes and plasma cells, were present in the portal tracts and scattered throughout the parenchyma (Fig. 1).
Kidney lesions comprised areas of coagulative necrosis of the proximal tubules, predominantly in the cortex, but extending into the medulla (Fig. 2).Most of the remaining tubular epithelial cells were swollen, with finely granular cytoplasm (Fig. 2).Some proximal and distal convoluted tubules were dilated, while scattered tubules, especially at the cortico-medullary junction, contained yellowish-pink granular casts (Fig. 2).Other lesions included moderate, diffuse pulmonary congestion and multifocal atelectasis.The spleen was moderately diffusely congested.
During a farm visit, numerous Lantana camara shrubs were found in the garden and surrounding camps of the smallholding.The farmer had noticed some of the goats consuming Lantana camara plants in the garden and on closer examination it was clear that the plants had been browsed.Another species, identified by the National Botanical Institute, Pretoria, as Lantana mearnsii Moldenke var.latibracteola Moldenke, was also growing on the premises, although in far lower numbers than L. camara.This is an indige-nous Lantana sp. of uncertain toxicity.At the time of the visit, the rest of the flock appeared to be in good health.

DISCUSSION
The clinical signs, gross and histopathological findings in this case are compatible with those described for acute L. camara poisoning in cattle, sheep and goats 2,3,5,9,11,[16][17][18] .The fact that photosensitisation was not present in this case correlates with previously described cases of experimental toxicity in goats in Zimbabwe 10,11 .It is believed that this may be attributed to relatively mild liver damage, insufficient to prevent elimination of phylloerythrin 10 .Alternatively, the course of the toxicosis may have been too acute for the animal to have been sufficiently exposed to sunlight.
Other toxic or infectious causes for the presence of icterus in the case examined were ruled out on the basis of the necropsy and histopathological findings.Although only 1 goat was presented for examination, it is possible that the other mortalities in the flock could also be attributed to L. camara poisoning, especially when the epidemiology of this case is taken into account.
To our knowledge, this is the 1st report of naturally occurring Lantana camara poisoning in goats in South Africa.Goats usually avoid eating these unpalatable plants.An important predisposing factor is the introduction of goats from an area where L. camara does not occur to a smallholding where the plant grew abundantly.In addition, the pasture was of poor quality at the time of introduction.Subsequent to our diagnosis, the premises were cleared of all L. camara shrubs and no further cases were reported.

Fig. 2 :
Fig. 2: Kidney: necrosis of epithelial cells in some proximal tubules is present (arrowhead).The remainder of the tubular epithelial cells show degenerative changes.There is also dilation of occasional tubules, some of which contain cellular casts (short arrow).HE ×400.