Rat lungworm has a ground zero, Puna.

[randomq]

Hmm, who is voting/voted on the park study? I'd contact them...

[DoryGray]

Just watched Monsters Inside Me. It was about Smiley's son Phoenix and how he caught rat lungworm from siphoning. The narrator, biologist Dan Riskin said "RLW is pretty rare in the world, but recently there has appeared what seems to be an 'outbreak' on the big island of Hawaii." Kudos to him for telling it like it is, on national TV.

[Guest]

Here is a well written article on RLW from the Maui news.

http://www.mauinews.com/news/local-news/...m-disease/

I still can't believe how much the state down plays the number of RLW cases. The real number of RLW cases are indeed much higher than 16 in the state of Hawaii, the state has no way of really knowing. Hundreds of RLW cases have been misdiagnosed by state doctors and hundreds more were never tested or treated for RLW. jmo

[Jimbo2017]

Hot off the presses - Publication by Kay Howe and the Jarvi team and collaborators - Bad news for catchment

" Live, infective-stage larvae were able to traverse rainwater catchment polypropylene sediment filters of 20 #956;m, 10 #956;m, 5 #956;m, and 1 #956;m filtration ratings, but not a 5 #956;m carbon block filter. These results demonstrate that live, infective-stage A. cantonensis larvae emerge from drowned snails and slugs, survive for extended periods of time in water, and may be able to enter a catchment user's household water supply."

https://journals.plos.org/plosone/articl...ne.0209813

Mauka Hilo-side

[MarkP]

A couple of thoughts:

First, most filter ratings are nominal meaning that for a nominal 20 micron filter the average particle stopped is 20 microns but some particles both larger and smaller still get through. Second, what is the nominal diameter of a cat or a rat? Coompare that to the size of hole they can wiggle through if they really want to.

It may be that the 5 micron carbon block filter is pretty much all 5 micron holes whereas even a 1 micron yarn wrapped filter still has a few 10 or 20 micron holes in it.

[MarkP]

Interesting reading. The 10 micron filter let through more larvae than the 20 micron filter did. The researchers note that the construction of the 10 micron filters was different, having smaller diameter yarn and they seemed more loosely woven. The study acknowledged that the filter ratings were nominal meaning they would stop a range of particle sizes centered around the nominal value. They said more testing would be required to see the performance of filters with absolute ratings. The L3 larvae that infect people can swim but 95% of the larvae were detected in the bottom samples out of 3 samples taken from 50ml water columns. Whole drowned slugs yielded more larvae than minced slugs. The larvae didn't start jumping ship in significant numbers the first 2 days after drowning, peaked during the 3rd and 4th days and tapered off quickly after that. The L3 larvae lasted "at least" 21 days and the L1 larvae lasted at least 56 days. Not sure what at least means. I take it to mean that the dangerous L3 larvae remain viable about a month. All filters stopped most of the larvae and the 5 and 1 micron filters tested let hardly any through. They disinfected their equipment between test runs with 10% bleach solution so I assume that concentration of bleach will reliably kill them.

Having read the report it is clear to me that sediment filters do filter the larvae out to some degree. Getting high quality filters is important. Filling from the bottom and drawing from the top can potentially make a huge difference. A 5 micron carbon block filter stopped all larvae in this study. I think a safe catchment system is possible and it should have the following features:

1. The tank design should exclude slugs and snails.
2. Water from roof should enter bottom of tank and pump pickup should draw from the top level. Avoid excessive mixing. You want the tank to stratify.
3. Multiple filters of progressively smaller filtration size. The 20 micron filters let through less than 10% of the larvae. The 5 micron filters basically let through no larvae except one run showed 1.2% transmission. 10% x 1% is already a very tiny percentage getting through. Finally use a 5 micron carbon block filter and you are down to basically complete removal of larvae.

I think the real threat would be in getting a bad filter with a leak in it, screwing up when changing filters so as to compromise function, or just general poor habits that let lots of unfiltered water through during filter changes. However even unfiltered water is unlikely to have enough larvae to really hurt you though.

[Midnight Rambler]

It may be that the 5 micron carbon block filter is pretty much all 5 micron holes whereas even a 1 micron yarn wrapped filter still has a few 10 or 20 micron holes in it.

That was my thought as well. When I was shopping for filters last time I noticed that the fine print says something like (for a 10 micron filter) "blocks 95% of particles over 10 microns and 99% over 20 microns". Which isn't very good!

The results from the 1 micron polypropylene filters were especially interesting. The 1 micron didn't let any through and the 5 micron only a very few, but the last run tested them after letting the filter sit for a while, flushing through water that didn't have any worms in it. So that showed that worms that had stuck on the filter before, were able to get through when it was restarted. I wish they had done more replicates though, because one of the 1 micron filters let none through, while another let in 64, much more than any of the 5 micron filters. I wonder how the different brands vary as well. I expect they're pretty variable, but it would also be a huge amount of work to test them.

The pump can't draw from the top of the tank, because it has to be able to pull water when the level drops. But I believe you can get a float so that you can pull water from just below the surface (you don't want to get stuff that's floating either). Pulling from just above the bottom is probably good enough anyway.

Lisa Kaluna, one of the authors, said on FB that they're in the process of testing UV systems now. The worms apparently aren't killed by UV sterilizers (tough buggahs!), but it's not clear whether they are still infective.

[MarkP]

My tank is set up so the water enters gently through a diffuser at the bottom of the tank and leaves through a floating pick-up 6" below the surface. That feature alone does a lot of the filtering.

ETA: The danger of most germs is that they will reproduce once they get inside you. UV sterilization doesn't kill the germs it makes them unable to reproduce. The threat posed by the rat lungworm larvae is that each larva goes walkabout in your nervous system and does a tiny amount of damage before it dies and in people it was not going to reproduce anyway. I have no doubt that enough UV could kill anything but what makes UV sterilization work so well is that it targets the Achilles Heel of most infectious agents, their high reproductive capacity, by taking out their DNA with a small economical dose of UV, and that won't faze these larvae who do their damage before reproducing.

[MarkP]

I have been coming on strong saying that rat lungworm is not a problem in catchment systems if they are built right. To be fair though there have been a couple of times when I have found semi-slugs in my living area and I don't know how they got there. One time I had left some cans of soup outside and brought one in after dark. Shortly after that I found one of the little buggers crawling on my kitchen counter. I assume that it was on the can from outside. Imagine leaving a bag of groceries on the front stoop with salad makings in it. A slug could get in like that quite easily and your mainland lettuce could be the vehicle for a slug getting inadvertently eaten.

I do think that a catchment system can be made safe because it can be a closed system downstream of all the filters but these darn semi-slugs are sneaky.

[HereOnThePrimalEdge]

Live, infective-stage larvae were able to traverse rainwater catchment polypropylene sediment filters...

Since so many people in Puna use water catchment with sediment filters, why is the incidence of rat lungworm so low here? We shower in that water, wash our dishes, hands (with which we eat), cuts and wounds in that water, even brush our teeth with that water, and yet we're not all dead yet.

Most of the rat lungworm cases I've read about were attributed to eating vegetables, a few were undetermined but not many.

Are most of us not exposed through some combination of good fortune and luck? Or, are many of us unknowingly exposed, with the vast majority of cases undiagnosed and far less severe than those who are hospitalized?