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Chances of getting Schistosomiasis from african cichlid expo
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Ciklido
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Joined: 06 Aug 2005
Location: Ontario, Canada

PostPosted: 2011.01.21(Fri)22:23    Post subject: Chances of getting Schistosomiasis from african cichlid expo Reply with quote

I just had that question because I am now learning about schistosomiasis and their life cycle/treatment/detection methods and thus since the african river valleys and over 200 million sick people its probably likely that some water in the great african lakes or like lake victoria for example might have some degree of infection. How do fish exporters account for this?

EDIT here is an article I found everyone can view it and describes the problems with lake victoria, its quite intersting and quite surprising to most african cichlid enthusiasts if they are new.

http://www1.american.edu/TED/victoria.HTM
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unissuh
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Joined: 29 Mar 2005
Location: Melbourne, Australia

PostPosted: 2011.01.22(Sat)0:58    Post subject: Reply with quote

Sorry if I've misunderstood your concerns - are you asking what are the chances of catching schistosomiasis from your cichlids or from the lake?

I have a passing understanding of this parasite/disease, one of the labs within my research department works on schistosomes and I have proof-read a few documents and theses on the topic. Very Happy

Schistosomes have very specific life cycle requirements, the human-infective stage can only be produced from infected snails. The chances of you getting schistosomiasis from your cichlids are zero. Chances of acquiring it from the lake however, depend on whether the snail host exists in the waters. They are fairly fussy parasites and will only infect one specific snail species. It seems pretty likely that the lake is contaminated with sewage from the secondary mammalian host.
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Ciklido
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Location: Ontario, Canada

PostPosted: 2011.01.22(Sat)1:39    Post subject: Reply with quote

Yes that was my original question. I know that the eggs hatch once in water and the miracidia are released. These pass through the snail tissue and then have succesive regenrations within the snail asexually until cercariae are released in the water free swimming eventually contacting human skin and passing through that tissue.

I guess I was thinking how the aquarists over there in lake victoria and nearby are able to export cichlids (sometimes I see ads of african exports wild type) and 1, not get infected, and 2, make sure that the water used for transport is free of parasites.

A sad fact I read in the link above is that less than 50% of native Haplochromis species exist due to the human introduced perch. and how is it that cercariae can differentiate between a fish and human? I guess would be another question id look into. Laughing
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unissuh
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PostPosted: 2011.01.22(Sat)1:54    Post subject: Reply with quote

Don't know if they are able to avoid being infected...treatment is fairly easy and effective (for now) though. Just pop a pill of praziquantal and all the parasites die.

There is a large dilution effect here - hundreds of miracidia are released but what sort of volume are we talking about in a lake? Add this to the fact that miracidia have a time limit to infect something - offhand it's not very long, half a day or so. Even if there was miracidia present in the water, it'd die long before it got to you.

As for infectivity, there are two fairly easy explanations for this. First is that miracidia are attracted to host via "smelling" chemical cues from the skin - presumably fish do not secrete the same chemicals as mammals. Secondly, they burrow into the skin with the help of various proteases; scales are obviously quite different to skin and thus these may not be sufficient to penetrate into the fish. The last answer as to why the parasites don't infect fish - probably because any that did didn't survive. They have some quite specific requirements in order to mature into adult worms, in mammalian hosts this involves migrating all around the body (including specifically to the lungs and liver) in order to mature, find a mate and then start producing eggs. The worms themselves are pretty big, about 1 cm long and 1 mm wide. Even in a mouse, it's a pretty bloody fiddly trying to dissect them out of the mesenteric veins which are barely wide enough for the worms to fit (yes, I have done this). The same worms would probably cause a heart attack in a fish, which is also quite physiologically different (e.g. doesn't have lungs).
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Ciklido
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PostPosted: 2011.01.22(Sat)18:45    Post subject: Reply with quote

Yea your correct all those points make sense. I was curious if there were ever any cases with aquaculturists being infected and how they would go about catching the african cichlids without being prone to infection. I know that praziquantel is the most effective for now although reocurrence rates seem to be high since their lifecycle has to this date not been highly interrupted.

I did see some nasty pictures online in google. In my lecture for this course we watched a couple of videos of school children being tested. I guess we humans are just too cozy Exclamation
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unissuh
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PostPosted: 2011.01.22(Sat)21:36    Post subject: Reply with quote

My guess is they don't avoid being infected to be honest. I can't think of how one would avoid being infected as the parasites are capable of burrowing into any exposed skin. What seems to be the easiest explanation is just that anyone who has been exposed would just pop a dose of praziquantal afterwards to kill any parasites. Not something that will continue for much longer IMO, there are a few recent reports of parasites showing resistance to praziquantal. If this becomes widespread, it could get interesting...offhand there is only one other drug that has widespread efficacy against schistosomes and it is mainly reserved for malaria infections, a disease which is largely considered more important...

It should, in theory, be fairly easy for aquaculturists to avoid schistosome contamination. Just kill all the snails. Of course, we all know how hard this actually is in practice, without completely wiping out the rest of one's stock that is.

There are some interesting pictures and videos that parasitologists show. I remember one of the lectures I had back in undergrad - it contained a picture of a group of children in an African village they had treated with anti-parasitic drugs with the huge pile of dead parasites next to them (half the height of the children!).
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Ciklido
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PostPosted: 2011.01.23(Sun)20:54    Post subject: Reply with quote

wow yeah thats really schocking site. Anywho my course for this topic just had a test and I just finished a concept paper so now we will be moving to the next topic. And by the way just curious since you seem to be in research are you a Masters student or doing a phd in biology or something? I'm just in a life science degree due to ignorance and carelessness in first year but I'm doing well now.

And also I have this 55 gallon aquarium but I don't know what to do with it! its empty, its where I used to have african cichlids.
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unissuh
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PostPosted: 2011.01.23(Sun)21:50    Post subject: Reply with quote

Yep, PhD in microbiology/immunology, more so the latter than former.

Perhaps you should try to culture schistosomes in the tank. Twisted Evil In all seriousness, I wouldn't know what to do with a 55g myself...much bigger than any tank of mine.
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