Clinical & pathological features of acute toxicity due to Cassia occidentalis in vertebrates

Indian Journal of Medical Research, July, 2009 by V.M. Vashishtha, T.J. John, Amod Kumar

Cassia occidentalis is an annual shrub found in many countries including India. Although bovines and ovines do not eat it, parts of the plant are used in some traditional herbal medicines. Several animal studies have documented that fresh or dried beans are toxic. Ingestion of large amounts by grazing animals has caused serious illness and death. The toxic effects in large animals, rodents and chicken are on skeletal muscles, liver, kidney and heart. The predominant systems involved depend upon the animal species and the dose of the beans consumed. Brain functions are often affected. Gross lesions at necropsy consist of necrosis of skeletal muscle fibres and hepatic centrilobular necrosis; renal tubular necrosis is less frequent. Muscle and liver cell necrosis is reflected in biochemical abnormalities. The median lethal dose ([LD.sub.50]) is 1 g/kg for mice and rats. Toxicity is attributed to various anthraquinones and their derivatives and alkaloids, but the specific toxins have not been identified. Data on human toxicity are extremely scarce. This review summarizes information available on Cassia toxicity in animals and compares it with toxic features reported in children. The clinical spectrum and histopathology of C. occidentalis poisoning in children resemble those of animal toxicity, affecting mainly hepatic, skeletal muscle and brain tissues. The case-fatality rate in acute severe poisoning is 75-80 per cent in children.

Key words Animal toxicity--Cassia occidentalis--poisoning

Introduction

An acute illness of young children, with brain involvement and high case-fatality, has been plaguing Saharanpur and several neighbouring districts in western Uttar Pradesh (UP) over the past two decades or more (1,2). It occurs in annual seasonal outbreaks and was earlier diagnosed presumptively as acute encephalitis of unknown viral actiology (1,2) Recent studies have shown the illness to be an acute hepatomyoencephalopathy (HME) syndrome, caused by toxicity from a common weed, Cassia occidentalis (3-8). The illness develops in children within several hours after eating the beans of C. occidentalis (3-8). The exact toxin(s) involved are not known.

For definitive diagnosis of a toxic disease the toxin has to be identified. Unfortunately, toxicological investigations in children with this syndrome have not been possible (4,5). We have so far not been able to identify laboratories capable of and willing to investigate for detection and characterization of unspecified toxins. Although several toxicology laboratories were approached, none felt interested or confident to identify specific toxins causing HME syndrome. Plants are notorious to contain multiple toxins and it will be quite arduous and expensive to attempt to identify the specific toxin(s) causing a specific syndrome.

In the absence of identified toxin(s) involved in HME, the actiological association is based only on epidemiological and observational studies (4-8). In order to enhance the strength of evidence for causally associating C. occidentalis with HME, biological plausibility of such association will be helpful. Fortunately a large body of information is available on clinical features and on tissue pathology of Cassia poisoning in animals, due to accidental poisoning as well as experimental studies.

The weed: Cassia occidentalis

General features: The Cassia spp. (family: Fabaceaesae) are erect, lightly branched leguminous trees and shrubs. Cassia shrubs are usually 6 to 8 feet tall and are mostly annual, but some species are perennial. All Cassia spp. are toxic or poisonous, but C. occidentalis and C. obtusifolia are considered to be more toxic than others (9,10).

C. occidentalis is found as a weed among various crops (Fig.). In Europe it is found in corn and soybean fields (9). In India it is widely prevalent as an opportunist that grows along roadsides, fence lines and over heaps of waste material, in addition to agricultural fields (9-11). In Hindi, the weed is known as Pamaad (Panwaad) and Kasondi. Pamaadis actually the name of another similar-looking weed, C. obtusifolia, found less frequently than Kasondi. C. obtusifolia is less prolific in growth, flowering and poding (10).

The leaves of C. occidentalis are alternate, compound and pinnate, consisting of four to five pairs of leaflets widely spaced along a common stalk. The leaflets are pointed at the tips, in contrast to the rounded leaflets of C. obtusifolia. The flowers are yellow and produced in loose clusters in the terminal leaf axils (9-11). In India the flowering time is after the heavy monsoon rains (after July) (10). The fruits of the plant are in form of 'pods'--thin, fiat, 3-4 inches long and pale green when tender, thick and dark green when mature. The poding time is from September to November (10-11). The pods are slightly curved and with paler longitudinal stripes along the edges. Each pod contains around 50-60 small beans (seeds) together weighing 1.9 to 2.25 g. Each bean is about the size of a cumin seed, but shorter. The tender beans are green, soft and juicy and taste like peas. From December onwards the pods start drying up, turn brown and the beans turn dark brown (10).