Heu Kan

[thedi]

Hi,

'heu kan' are a common problem in Isarn (Khon Kaen). This are small water snails living on plants in 'huay's which bite you if you get in contact with them. Such bites look like flea bites and itch for days.

Heu kan seem to be only in certain places in a huay. Also there are times when a lot of fisherman get biten by them - in other seasons nobody is biten by heu kan.

Does anybody know anything about them? They have a spiral shell which is flat, not rising to the center and are about 1cm in diameter. They like to cling to roots of floating plants too.

The reason I want to know: I intend to plant lotus and other plants in my pond. But the pond should still be usable for swimming. Last year I bought some lotus in a plant shop and they had heu kan on their roots; fortunately my gardener saw and knew them.

Local people tell me they are mostly found in clear water; me pond has very muddy water (clay particles). But I intend to chenge that.

If I get heu kan, how could I get rid of them?

Does anybody know a name for heu kan which could be googeled?

Thanks for any help

Thedi

[Farma]

หอยคัน is the Thai name for them. Google gives plenty of replies in Thai.

[thedi]

This is a typical example, as well known here in the huay in Bankok Manchakiri:

But this one looks not like a heu kan to me, so it was under this title in the internet:

So I have now images, I still don't know much about them: why are they only in certain eareas of a huay? what are the natural enemies? what are their prvered environment?

Thedi

[Farma]

My wife remembers the itchy snails from her childhood but hasn’t heard of them for years. Maybe they have died out in her area. She provided the Thai name for them.

There is a snail that looks like the one in your top photo listed as living in Thailand.

Family Planorbidae

Physastrini with possibly 12 valid genera:…… Ameriana (north and north-east Australia, New Guinea, Indonesia, Thailand and the Philippines),………”

Hope this helps.

More info from applesnail.net

Most Planorbidae have a flat shell, somewhat similar to a ramshorn in shape, hence their common name ramhorn snails. However, not all snail with this shape are Planorbidae, for example the Ampullariidae genus Marisa has a similar shell shape.

The shell of many Planorbidae is right turned (dextral), but their body is sinistral, a situation similar with the Lanistes genus of the Ampullariidae (apple snails), which have a sinistral shell and dextral body. Because collected shells are often empty, these snails are considered dextral for practical, determination reasons, but on anatomical grounds one could call these snail hyperstrophic dextral. On the other hand, some Planorbidae genera like Ameriana and Physastra from the Physastrini tribe have sinistral, globose conic shells, while the Ancylus genus have flat hood-shaped shells, similar to the Acroloxidae snails.

The eggs of these hermaphroditic Planorbidae snails are laid in transparant clutches on plants, stones or other objects.

Most Planorbidae members prefer habitats with slow moving or stagnant waters like ponds, lakes and swamps.

Edited October 23, 2006 by Farma

[Farma]

Some more websites to look at.

This site has many photos http://members.aol.com/Mkohl2/Planorbidae.html

"Many of these species harbor the larvae of parasitic worms, particularly southern and Old-World taxa.”

The dermnetnz site is more what you are looking for. It refers to Swimmers Itch with information on treatments etc.

http://dermnetnz.org/arthropods/swimmers-itch.html

“The technical name for swimmer's itch is cercarial dermatitis. In developing countries, swimmer's itch has been called ‘rice paddy itch’, ‘clam diggers itch’, ‘sawah’ (Malaysia), ‘kubure’ or ‘kobanyo’ (Japanese) and ‘hoi con’ (Thailand).”

[thedi]

Congratulations, well done, Farma!

The dermnetnz site is more what you are looking for. It refers to Swimmers Itch with information on treatments etc.

http://dermnetnz.org/arthropods/swimmers-itch.html

“The technical name for swimmer's itch is cercarial dermatitis. In developing countries, swimmer's itch has been called ‘rice paddy itch’, ‘clam diggers itch’, ‘sawah’ (Malaysia), ‘kubure’ or ‘kobanyo’ (Japanese) and ‘hoi con’ (Thailand).”

Yes, you solved it. All the phenomenas like why are just certain places in the huay - and just at some times - invested are clearly explained. With this information it will be quite easy to keep the problem out of my pond. Even if I would get invested through water from the canal or imported plants, there is no reason for panic as long as there are no birds in the pond. The worst that could happen is, that I would have to wait for a view month before I could swim again in my pond.

I certainly will not rise ducks in my pond now (I was considering to have just one or two pairs, but that's out now).

Thank you very much for your help in researching this. I would never have found it.

Regards

Thedi [email protected]

[Khonwan]

Local wisdom here in Nakhon Sawan treats the ihuay kan nfected ponds with cut papaya trees. Worked for my pond!

[thedi]

Local wisdom here in Nakhon Sawan treats the ihuay kan nfected ponds with cut papaya trees. Worked for my pond!

The whole papaya trees, or just the leaves?

Whole or shredded?

How big is your pond, and how many papaya trees did you use?

Is there a constant flow of water through your pond, or is there always the same water?

Are there o lot of other plants (pak bung, lotus etc), = food for the heu kan in the pond?

Do ducks have access to the pond = natural enemy of snails?

[Khonwan]

Local wisdom here in Nakhon Sawan treats the ihuay kan nfected ponds with cut papaya trees. Worked for my pond!

The whole papaya trees, or just the leaves?

Whole or shredded?

How big is your pond, and how many papaya trees did you use?

Is there a constant flow of water through your pond, or is there always the same water?

Are there o lot of other plants (pak bung, lotus etc), = food for the heu kan in the pond?

Do ducks have access to the pond = natural enemy of snails?

Hi Thedi. Quick reply since I see you are online just now. My pond is around 400 sq.m. Use the tree trunk (with leaves if you wish). A couple of young trees or one mature tree cut in half (both halves being used!). My pond has no flow (except when overflowing during the rainy season!). I have some pak bung and lotus but not much since I swim regularly. No ducks. I now also rear some fish in this pond: pla taptim (talapian [sp]) and pla jeramet (butterfish). The pla jeramet eat snails! They are also tastier than the pla taptim, in my opinion, and grow very quickly. I did not have them at the time my pond became infected. The huay kan flowed into my pond at that time from a neighbour's small, shallow, stagnant pond during the rainy season. No problems this year, presumably due to the pla jeramet. With regards to the papaya trees: the snails attach themselves to the floating trunks. I assume it is the papain (yang mulagor), the sap in the tree, that does the job.

[thedi]

Hi Konwan,

Thanks, this sounds interesting. I will keep your post for later reference, if my pond gets heu kan.

Right now there is no problem with heu kan. My current problem is that the water is too muddy to swim. So I want to reduce the fish and plant more pak bung and other plants. This is the way to get problems with heu kan and I am looking for a solution ahead of time, if this pest should come into my pond.

Thanks for your tip.

Thedi [email protected]

[Crushdepth]

I think the itch is not from the snails but from a parasite they host during part of its life cycle.

You can kill snails with copper sulfate solution (I forget the dose but I'm sure you can google it). I suggest that the most environmentally friendly way to do it would be to soak your lotus plants in the solution for a while, rather than treat the actual pond (as it will kill most other invertebrates and fish as well). Alternatively, you could grow some lotus from seed.

Unless you are using bore water, it is quite likely you will end up with snails in your pond anyway.

[thedi]

Yes, the itch is not from the snails, but from parasites of the snails. The parasites need two hosts to propagate: some sorts of snails and the birds, usually ducks. Ducks eat snails, but they can get invested by the parasites this way. The parasites can come with bird shit or new water into the pond. There is no sure way to keep this parasites out of a pond, but if either the snails or the birds are missing, the will die out. I don't know how long this would last.

My pond contains about 3000 qm of water. So poison is out of the question, it would need to much.

I just try to reduce the risks. As view snails as possible, no ducks, mostly just rain water and water from a irigation canal only when there is a lot of water flowing there. This year I didn't take any water from that canal at all.

I think I may get around this parasites in the long time. After 4 years I do not have them yet. The discussion started here because I want to increase the water quality (it is too turbid now), and for this reason I plan to deplay less fish and more plants.

Thanks, to the help of some board members I understand now where the itching would come from, hence I can decide better what to do.

Thanks to all who contributed to this discussion

Thedi [email protected]

[Crushdepth]

You could try stocking some snail-eating kinds of fish in your pond to help keep the numbers down. Not sure what local species are snail eaters, but bound to be some available.