Venom of a six-eyed crab spider, Sicarius testaceus (Purcell, 1908), causes necrotic and haemorrhagic lesions in the rabbit.

By employing haematological, histological and isotope studies on rabbit, it was shown that envenomation by the South African crab spider, Sicarius testaceus, results in tissue necrosis and a marked increase in the permeability of the blood vessels in the vicinity of envenomation. The venom also acts systemically, which results in petechial bleeding of some viscera, thrombocytopaenia and elevated fibrinogen levels. Rabbit envenomation by this species results in a dramatic drop of the platelet count, without haemolytic anaemia. Should these parameters be the same in humans, they may serve as a yardstick to distinguish presumptive S. testaceus envenomation from that of Loxosceles.

Putative cardiotoxicity of the venoms of three mamba species.

The venoms of all mamba species are known to contain potent neurotoxins. Some authors suggest that cardiotoxins from mamba venom are responsible for heart failure in envenomated patients. This study was undertaken to come to a better understanding of the mechanisms and possible effects of mamba venom on the hearts of animals. The venoms of three mamba species namely Dendroaspis polylepis, Dendroaspis angusticeps, and Dendroaspis jamesoni were screened for cardiotoxicity by the cardiomyocyte viability test on cardiomyocytes isolated enzymatically from guinea pig ventricle muscle. This analysis was followed by an electrophysiological evaluation of the effects of venoms (from the Dendroaspis species) on cardiac ion channels by employing the whole-cell clamp procedure. In this study the cardiomyocyte viability test indicates differences among the venoms of the three mamba species. The venom of D. jamesoni seems to be the most potent followed by D. angusticeps and then D. polylepis. The whole-cell clamp results indicate that the venoms have no affinity for cardiac potassium channels but have an inhibitory influence on cardiac L-calcium channels. Although this study provides evidence that mamba venoms have a specific effect on isolated myocytes of guinea pig, it is doubtful that it will have a profound influence on a human heart in case of envenomation.

Cardiotoxicity of the skin of the red-banded rubber frog, Phrynomerus bifasciatus (Smith 1847).

The skin of the red-banded rubber frog is said to secrete an unidentified toxin. Whole skin extract as well as HPLC fractions were tested for toxicity on viable, isolated cardiomyocytes. The skin extract and one of its fractions were shown to be cardiotoxic. Whole-cell clamping tests demonstrated that both extract and fraction interfered with the function of the potassium channels of the cardiomyocytes and that the toxic substance has an affinity for the IK, channels. Investigations are in progress to isolate and characterize the toxic substance.

[The Tugela-Vaal state water scheme as a bilharzia risk]. / Die Tugela-Vaal-Staatswaterskema as 'n bilharziarisiko

The Tugela-Vaal River water scheme constitutes a possible source for the introduction of bilharziasis into an area where the disease is at present not endemic. A survey was made of the snail species in the area encompassed by the scheme. Although Bulinus (Physopsis) africanus (a host of Schistosoma species responsible for urinary bilharziasis) was found in the proposed source area of the water scheme, it is not possible at this stage to determine with certainty whether this host will be introduced over the Drakensberg escarpment into the Orange Free State. However, this is a distinct possibility, and it is discussed in relation to ecological factors.