Hi there, thought I'd share an experience I had last year when I was bitten by a smallish male Thrasops jacksoni.
First, a little background for anyone who has never seen one of these extraordinary colubrid snakes. They are basically a Dispholidine snake, the same grouping that includes the Boomslang and African Twig snakes (both rather dangerous, even fatal). Although they possess no true "fangs" for venom injection, their saliva is known to be quite toxic (it contains the "3-finger toxin" found in elapid venom) and Dr. Brian Fry of VenomDoc states that they may be as toxic as Boomslangs.
In appearance they mimic a black boomslang rather closely. At first glance they are difficult to distinguish but somebody familiar with both snakes should be able to identify the Thrasops by its SLIGHTLY longer head shape and a difference in labial scalation. (Actually, baby Thrasops and Dispholidus don't look all that alike).
Currently in my collection are 2.1 T. jacksoni (and I want more!). They are active, interesting snakes and make great displays in tall vivaria. Mine are housed in enclosures that mimic a bunch of weaver bird nests hanging on some branches, with tangles of banana root screwed to the walls to give the appearance of dense savannah thicket. I use natrualistic nest-boxes designed for finches and hang these from larger branches. The snakes really thrive in this environment and can always be seen popping in and out of their arboreal hidey-holes.
They are ravenous feeders, curious and utterly fearless. If you open their enclosure, you had better have a hook on you because they will quickly stretch out to investigate you and whether or not you have any food! They are not AGGRESSIVE as such... they just seem to have a shark-like instinct to bite anything once in case it's edible. I actually saw one bite itself during a feeding and continue to chew for some time...
Once they are out of the terrarium and know they are not being fed, they can actually be free-handled with little danger (although I definitely do not recommend doing so without gloves and a long shirt - just read on).
Thing is, last year I was bitten and suffered quite severe effects (for a rear-fang) from one of my Thrasops and I thought I'd relate a little about the symptoms since I can't seem to find another case history for this species.
Whether or not this is a "harmless" snake used to be quite confused (it certainly was when I got into them!), with some claiming to have been bitten and suffering no ill effects. Certainly, I had taken a nip or two with no symptoms, and both my small male and my female have each actually attempted to swallow my finger on individual occasions with absolutely no ill effect.
Because I had never suffered any ill effects... I got careless. I was sloppy, and I took a bad bite.
The small male missed the proffered mouse entirely, slid up the tongs, and sank its teeth into the forefinger of my left hand. Not wanting to hurt it or break any of its teeth I unwisely let it hang on there for a couple of minutes. Eventually, however, I got tired of watching my own blood run down my hand and tried to insert a playing card between the snake's mouth and my skin to gently prise it off.
Probably thinking its prey was attempting to escape, the snake really went for it, frenziedly chewing even harder. Once I had finally got him off, I realised that I was going to feel some ill effects...
I know that the bleeding just didn't seem to stop for ages and ages. Boomslangs have anticoagulants in their venom that prevent the blood from clotting, and so it must be for Thrasops. Throughout the following few days a steady trickle of blood and plasma would leak from the bite wound.
The other thing I remember clearly about the initial reaction is the itching. The back of my hand and my palm both started to really itch, and the bitten finger became kind of stiff over the next fifteen minutes. That stiffness was to gradually extend down to the next figer, then to the knuckles and finally, after a few hours, the whole hand was noticably swollen. A nasty bruise had developed at the bite site and blood and tissue fluid would continue to ooze out for the next few days.
Annoyed and not unpeturbed, I nonetheless decided that these local symptoms didn't require medical attention (you might think me foolhardy or reckless. You're probably right, but remember I was not aware of how toxic this species might be at the time - I just passed it off as a reaction to some little rear-fanged snake that would be gone in a day or two). I kept careful notes and observations of the bite throughout.
The following morning my hand had swollen up to the wrist and was showing no signs of stopping. Over the next two days it would swell to about twice its original size, stretching the skin so much that the hairs all stood on end. My knuckles, fingerprints and palm lines had disappeared in a mass of shiny, pink flesh. My hand at that point looked not unlike an inflated rubber glove.
Of course the extent of the oedema (which would reach half way up my arm) meant that I was in quite severe pain for more than a week. Added to this, the lymph nodes in my left armpit and neck were enfarcted and painful as hell.
The bite wound was black and blue and the bitten finger was obviously the worst affected - immensely painful, bloated and unable to bend for weeks afterwards.
By this time I was obviously wise to the fact that this was no ordinary "mild symptom" and started doing research. It might surprise you to learn that, other than a course of anti-histamines I took no medication and from day one continued to go to work and live a normal life... fool that I am.
(Although, yeah, it was quite the talking point!)
Anyway, after ten days the swelling had mostly gone down. The bite is invisible and I have suffered no after-effects. Looking at my hand even a month or two after the incident you'd never know I'd been bitten. In hindsight, I should probably have checked in to A&E on the first night just to be on the safe side - you read so much about the two to four day latency period on Dispholidus bites and it really sets you thinking!
So that's it, pretty much, I gained a healthy respect for my little Thrasops (which are now pushing 6/7 feet and not so little anymore!). Just thought some of you might be interested in what a bite from one would be like, because I know there's little or no anecdotal evidence that I can find.
In my opinion I received such severe effects because, having just shed, I had not offered the snake food for more than a week and it must have built up a nice little stock of venomous saliva. That, and the fact that I allowed it to chew for too long (and when I tried to remove it it must have thought its dinner was going to get away and went berserk). If I had worn gloves I would not have been in that situation.
A lot about the whole bite history is reminiscent of some case histories of envenomation for Philodryas olfersii that I have read, and that species has caused a handful of deaths. I have to note that the specimen that bit me was quite small for a Thrasops, only about 48" or so. A much larger individual (and they grow quite large) could conceivably cause a much more serious - even fatal - envenomation.
I guess I may as well put up my own moral to the story, which is "who is worse, the fool or the fool who follows him?"
I was foolish for underestimating a poorly known rear-fanged snake. I was also foolish for not seeking medical attention. Learn from my errors, and give your FWCs, Boiga, Philodryas, Leioheterodon and other rearfangs the respect they deserve!