Amazon Web Services



3611880-11747500-668655691515Snakebites: Don’t Be So Hissssterical! 00Snakebites: Don’t Be So Hissssterical! -91440057404000Got any plans this summer? Longing for that crisp-warm air, the lingering craving for a “Cold one”, after a long day, the late sunsets, BBQs and your right to wear flip flops day to night. Ever thought about accounting for the Australian Brown Snake, responsible for 23 of the 35 deaths recorded from 2000 to 2016 amongst those plans? No? Welcome to Australia, home to 3 of the top 10 most lethal snake venoms in the world.Although there are approximately 20 distinct families, only 4 are venomous snakes (see Figure 1). The Elapids (Elapidae) and their subfamily the Hydrophiidae, or sea snakes, are the main group which inhabit Australia. With 20 of the 80 species of Elapids large and equipped with a venom strong enough to severely envenomate, or kill, this family alone was responsible for the 1000-3000 bites each year in Australia.Globally, snakebites result in the reported deaths of 81 000 -138 000 individuals per year. However, many victims are left with permanent disabilities due to toxicity. Regions of South Asia where it is difficult to gain access to treatment, have suffered death rates exceeding 10,000 deaths. The majority of snake bites occur due to provocation, and have proven to be a seasonal injury. Increases in the duration of snake activity could perhaps be attributed to the expansion of farmlands and climate change.Despite the idea that the topic of snake bites should not only spark an interest to a clinical physician, but a neurologist, nephrologist, hematologist and cardiologist, unfortunately, in 2009 the World Health Organisation (WHO) added snake bites to the list of neglected tropical diseases. Although they are relatively uncommon as life-threatening injuries, they cause harm on not only the victim, but also the families which may be dependent on them. Many will often survive with some form of permanent damage, possibly impacting their ability to work. Aside from aiding in defense, venoms play an important role in the digestion of prey. The quantity of venom injected at a time varies. A snake may severely envenomate its prey by striking multiple times, controlling the amount of venom injected through its fangs. Snake venoms are compromised of a cocktail of protein components and other small molecules which are responsible for the range of local and systemic effects on the body of the prey, that act by producing pain and/ or targeting specific systems or the enzymes necessary in metabolic function. For example, neurotoxins act on the nervous system; myotoxins on the skeletal muscle; haemotoxins on the coagulation, or the fluidity of blood; cytotoxins affect cellular process, often leading to cell death (necrosis); cardiotoxins target the cardiac system; nephrotoxins may cause damage to the kidneys. [Mention here somewhere which snakes have what toxins and the fact that there are no cytotoxic snakes in Australia]A particular enzyme, phospholipase A2, has been found to be present in the venom of poisonous snakes across all families. It is responsible for the damage to many red blood cells, leukocytes that are associated with immunity, skeletal muscle and vascular cells, as well as destroying the junction existing between motor neurons (nerve cells) and muscle fiber, impacting muscular contractions. The smaller molecules existing in the venom could be easily transported across the synapses involved in neural communication. Snake venoms act on the neuromuscular junction by producing flaccid paralysis of the voluntary muscles, causing death due to asphyxiation by either obstructing respiration or preventing sufficient airflow (Campbell CH). Depending on the venom, either the presynaptic or post-synaptic neuromuscular junction may be affected. Post-synaptic neurotoxins have been identified in the venom of snakes belonging to the Elapidae and Hydrophiidae families, whereas presynaptic neurotoxins showing a range of phospholipase A2 activity have been found across all four major families of venomous. The Elapids and Hydrophiidae are an exception which act on both sites (Wayne C Hodgson). There are two mechanisms involved in the disruption nerve cell communication. Through the post-synaptic mechanism, the receptors on a cell may become blocked by the neurotoxin, making it extremely difficult to receive signals. Otherwise, disruption may occur in the presynaptic site where the enzymes involved in packaging and recycling of neurotransmitters (chemical messengers) is interfered. These enzymes are crucial in removing the neurotransmitters in order to impede their stimulating effects, and therefore, a build up of neurotransmitters leads to continuous stimulation of the neurons and eventually cell death (Simpson, Lance 1971). Coagulation, Myotoxicity, Nephrotoxicity and cardiotoxicity (Brief summary of each- in one paragraph) Symptoms of snake bites Treatment methods ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download