Can WEST NILE VIRUS be isolated from the milk of an infected mammal?greenspun.com : LUSENET : Grassroots Information Coordination Center (GICC) : One Thread
Again, we have the proverbial elephant in the living room that nobody wants to acknowledge. I have searched everywhere for the answer to this question and find it CONSPICUOUS by it's absence! One would think that it would be a primary research question to be answered; Does an infected mammal(horse, cow, human) have live west nile virus in its (or her)MILK? Obviously, the answer to that question has so many health and political implications and ramificatiions that the authorities are keeping the answer to this question very close to their chests. We pay their salary, and have a right to know this!
-- Concerned in Detroit (firstname.lastname@example.org), August 23, 2001
The answer about milk is NO.
Contrary to your complaint that this is somehow "hidden," several official websites that I double-checked just now clearly indicate the way in which the virus is spread -- mosquito bites -- and all say things like "other types of contact" or "other mechanisms of transmission" have NOT been shown to be relevant for mammals. I thought all the websites I checked were quite clear on this. They didn't list each and every possibility individually, but it's hardly meant to be a secret.
Mammals are most often "dead end hosts" for West Nile -- the level of virus found in their blood and other tissues is not high, and it's there only briefly if at all following infection -- so it's not at all likely a mosquito biting an infected horse or human, say, will get the virus from the mammal and spread it during its next blood meal on a different animal. On the other hand, some but not all birds can maintain high levels of virus in their tissues, allowing easy transmission by mosquito bite.
In other words, West Nile transmission is "bird to mosquito to mammal [including people]," NOT "mammal to mammal" nor "mammal to mosquito to [anything else]".
By the way, this pattern is true of many if not most of the other medically important arboviruses (arthropod-borne viruses). Mammals are rarely a source of further infection. Dengue and yellow fever are the major exceptions.
There was one interesting experiment that showed apparent crow-to- crow transmission in the absence of mosquitoes, in a controlled environment, that may suggest a mechanism by which this virus spreads between Corvidae (crows, ravens, and bluejays). The Corvidae are a family of birds that is particularly susceptible to West Nile infection -- we sometimes joke that crows turn into "flying bags of virus" before they die of WNV. But it was a lab experiment and its relevance to wild birds is debatable.
On the whole, the problem is overstated as a risk to humans, although rare human deaths do occur. WNV is much more of a threat to certain birds such as the Corvidae -- which can suffer particularly high mortality (for example, a substantial fraction of the crows in New York State were killed the first two years that WNV appeared in North America).
As an aside, may I suggest this topic may be better pursued by carefully reading the various CDC or state health department websites, and/or calling the West Nile Virus program at your local or state health department with your specific questions.
--Andre Weltman, M.D.
-- Andre Weltman (email@example.com), August 24, 2001.
I agree with you, Andre, that info is available online, and its pursuit there would be most rewarding. But I'd like to add a few things our media has been giving us in the past week, since the darned virus has just arrived in Canada. A dead crow at Windsor and a dead bluejay at a nearby town have both tested positive.
Health authorities are now wanting to examine any and all crows and bluejays in the vicinity. The tests take almost a week to complete. In addition, they have begun collecting and examining mosquitoes--I had never known this, but apparently there are over 80 varieties of mosquitoes, and only one is able to carry the virus from birds to mammals.
Our experts are telling us that household pets are not too vulnerable to the virus, but that horses are. In addition, most humans will not react too strongly if infected with the virus, but the old, the young, and those with weakened immune systems (say those who have been on corticosteroids, for example) are indeed vulnerable and are even at risk of death. Apparently the virus causes a swelling in the brain.
Prevention? Get rid of stagnant water, the breeding grounds for mosquitoes, from your yard--bird baths, old rubber tires, ponds with no aeriation, etc. Wear an insect repellant containing DEET; if you must spend much time outdoors, stay as covered as possible.
Our health authorities are telling us that, now that it's here, it's here to stay. Get used to it.
-- Rachel Gibson (firstname.lastname@example.org), August 24, 2001.
Apparantly the good Dr. and the above lady either never seriously read much more than the CDC press releases about this disease. Or the good Dr. is spouting the party line and the lady is simply ignorant of what other information beyond the press releases is actually available. I have read EXTENSIVELY about this and have found that it is officialy advised that Level 3 precautions be used. It is also officially advised that blood and body fluid precautions be taken with infected persons and animals. There are offficial advisements to KEEP MOSQUITOS AWAY FROM INFECTED PERSONS AND ANIMALS. It is now being studied how much impact this will have on the commercial chicken industry! Pigs also seem particularly susceptable to this virus from what I have read. And, I defy you good Dr. to show me where, ANYWHERE, it is stated that the virus cannot be found in the milk of an infected mammal!
-- Concerned in Detroit (email@example.com), August 25, 2001.
Concerned in Detroit
Since you have read extensively on this subject would you please enlighten us with some source material for your convictions.
-- Martin Thompson (firstname.lastname@example.org), August 25, 2001.
"Concerned in Detroit," you need to distinguish between the extra careful precautions originally intended for lab workers and others who are working *closely* with virus-infected tissues (for example, doing necropsies on crows, preparing samples of internal organs for testing, cell cultures, etc.) versus the rest of the universe where the risk just isn't there, empirically.
I think it's fair to say that sometimes the CDC recommendations are a bit overblown for the real world outside the lab. And oiften they aren't originally meant to apply outside the lab setting. In a similar vein (no pun intended) I noted some years ago to my friends at CDC DVRD that their original set of guidelines for dealing with the bodies of dead mice...potentially infected with Hantavirus... were just way overblown. From the perspective of a state health department, trying to be sensible, we have always suggested throwing a dead mouse w/mousetrap into a regular plastic bag and sending it out in the regular trash, then wash you hands. (A lot more compostable than most garbage!) This is indeed what I do at my own home. The original guidelines included in public documents were silly, treating dead household mice like they were toxic waste. I suspect that often these types of guidelines are extensions or misunderstandings of appropriate precautions for the *laboratory*.
Ask yourself: if this virus (I'm back to West Nile now, but it's true of Hanta too) is so transmissible to humans in the real world, where are all the human cases? [A variation on Fermi's Paradox about extraterrestrial life!] Or don't you believe the statistics on how rare human illness really is? (Come to think of it, I retract that last question...see final paragraphs below).
As regards the risk to other mammals, it seems to vary. I don't have the stats handy right now, but IIRC in the original New York City studies, seroconversion (antibody demonstrating previous infection) was detected in a relatively few cats and dogs, with extremely limited numbers of such animals actually showing any clinical symptoms. Horses are interesting because they do become quite ill. Humans are sort of in-between. I don't know about pigs but I don't recall them being on the list of those animals thought to be at risk from WNV.
And chickens...well, not all birds are created equal. It turns out that "chicken sentinel surveillance" (put chickens outside, let mosquitoes bit them, then test the chickens for seroconversion) is useful for some arboviruses like SLE and EEE, but not useful for West Nile. Corvids and some raptors get infected (and often very sick), chickens just don't seem to. There was lots of fuss a year ago about expanding chicken surveillance systems (already in use in some places for some other arboviruses) for West Nile too, but it turned out not to work. Chickens were not showing antibodies to WNV, at the same time as dead crows and sick horses were turning up.
OK, having tried to offer some useful information, let me comment about the thread itself: The tone of the original question, and even more so of the rant/rebuttal, are pretty insulting.
<< "party line" >>
Oh boy, you obviously don't know me. Which is fine by me.
As far as I am concerned, this thread is over. I don't need this crap.
-- Andre Weltman (email@example.com), August 29, 2001.