Leeches

If you plan to visit Asia, particularly South East Asia then you should be prepared for leeches. There simply is no avoiding the fact. I find them absolutely fascinating, as I find people's various reactions to them. So I've decided to dedicate a whole page to them in deference to their importance in the ecosystem and in the psyche of the birder. 

How to understand them:

The haemadipsids are terrestrial, parasitic, blood-feeding leeches with an unusual biogeographic distribution; they are found only in the Indian subcontinent, Southeast Asia, Wallacea, Australia, Melanesia, Madagascar, and the Seychelles but not in Africa or South America. There are many different species. The other leech families, which are mostly aquatic, have a global distribution.

The sanguinivorous leeches that I am most familiar with in Asia have a substance called hirudin in their saliva which is an anticoagulant. So when you are bitten by a leech you will bleed long after it's had its fill. Generally speaking the bites do not hurt - it is thought that they also have a mild anaesthetic in the saliva. Some leeches certainly don't use an anaesthetic and possibly have larger mouth parts. The leeches at Da Lat in Vietnam are, for some reason, particularly painful. The upside is that by giving themselves away, they are easy to get rid of!  Leeches tend to be more prevalent after rain but there is controversy about who in a group is most likely to be bitten - the leader on a trail or the followers. My opinion is that the front person cops the brunt but those at the back tend to disagree for some reason! There are two common questions asked about leeches - how do they know you are coming and do they spread disease? Neither of these are easy to answer! Regarding the latter question, the straight answer is easy - no, they definitely don't. But if you have an enquiring mind, you might ask "why not?". I am still researching the answer to that one. It may be because they are thought to feed infrequently, possibly only once or twice a year and so any pathogens they ingest are already dead by the time they get to the next host.

The former question has a couple of answers. Leeches are responsive to light and mechanical stimuli. First, they can detect movement. So if you brush against a tree and tread heavily they will feel, rather than hear, you coming. Secondly, they can detect you by your body temperature. They have heat receptors. Leeches easily dry out and go into a torpid state if they do. But add water and they will rapidly spring into action.

How to get rid of a leech and more importantly how to avoid them altogether:

If you find a leech attached to your body the first thing to do is don't panic! The only thing a leech does is steal a tiny bit of your blood, look revolting and make a bit of a bloody mess. Is it really worth missing that rare skulker or new pitta because of a leech?! There are a few ways of getting rid of your leech. You can simply wait till it drops off, thereby avoiding touching the slimy thing and, after all, once it's attached it makes no difference when you remove it. You can just physically pull it off but then it may leave its mouthparts embedded in the skin potentially leading to infection. (Although this can happen anyway.) Lastly, you can resort to chemical means - anything that the leech won't like such as vinegar, lemon juice, salt, fire or, my personal favourite, tiger balm (or equivalent). Fire, such as a lit match or cigarette, should be avoided - you could end up with far worse injuries than those sustained from the leech. Tiger balm is great because it is easy to carry in your pocket, it's not messy and the leeches hate it.

Leech-proof socks in action

I have been to some amazingly leech infested places. I've seen them so thick on the ground, you can literally hear them crawling towards you. Some particularly good places to see leeches include Danum Valley and Khao Yai. But don't let this stop you from travelling to these hotbeds of biodiversity, there is an excellent way of avoiding leeches (almost) altogether. I used to scoff at these things called leech-proof socks believing that leeches should just be ignored. Over the years though and after many bites it seems that you develop a bit of a reaction to leech bites and the itching can drive you crazy. Also, the potential for infection should not be underestimated; this can be a real problem in the tropics especially as most bites will occur around the ankle area where shoes and socks tend to rub. Leech proof socks are the best way of denying access to your bare skin. (Most leeches can easily tunnel through the weave of your socks.) They are, of course, sock-shaped pieces of fine-woven material such as calico and are put on over your regular socks and under your boot. They are long with a pull-tie at the top which you tie up firmly under your knee cap and above your calf. If the leeches are particularly bad, it may be necessary to spray the boot and sock with an insect repellent otherwise they will simply climb up your leg to the nearest point of entry. I once counted over 60 leeches attached to my leech-proof socks at Kerau Game Reserve in Malaysia! So they did the job for me. Of course, the socks won't make you immune to the problem as the leeches will also climb on to you from overhanging vegetation and can attack you around the waist or the neck as well. Another tip is to always tuck in your shirt.

How to treat the bite:

The only way to stop the bleeding is to apply pressure at the point and wait. There is a strong possibility that the bite will start to itch after a day or so and if you have a few bites around the ankle this can become a problem. Again, my favourite remedy is tiger balm or balsam hijau (which is even better but harder to get) from Indonesia. There are a number of anti-itch concoctions available from chemists and these work almost as well. If its really bad, it might be necessary to use an antihistamine. Of course, if the bites become infected then it's a whole different story and you will need to consult a doctor.