Effect Measure


With all the talk about non avian reservoirs for H5N1, a little talk about flies might be in order, not because we think they are vectors for H5N1 (so far no evidence of that), but just because we like to talk about them. The subject came up recently in a New Zealand Medical Journal article (authors B. Harris and W Nelson), about which we’ve only seen news reports (we are away from our home base library, on vacation, which is one of the reasons we are slow on comments and light on posting; using a slow dial-up is pure torture).

Anyway. Flies.

According to the New Zealand docs, flies and too many cattle close to New Zealand cities is one of the explanations for their high rate of campylobacter food poisoning. Campylobacter is a bacterium responsible for a significant amount of food poisoning. New Zealand is reporting 14,000 cases a year and this is probably an underestimate (by a factor of ten to twenty, according to the authors). It is frequently found in chicken but it is easily destroyed by cooking. The paper analyzes temperature and chicken consumption in relation to campylobacter foodborne case reports. When temperature increases so do campylobacter reports. Campylobacter is commonly found in cattle feces. So how do they get to food?

Mr Harris said flies were the link between environmental sources of campylobacter and food. In New Zealand, the primary source of infection is thought to be the faeces of dairy and beef cattle.

It was the proximity to rural environments that allowed flies to transmit the bacteria to food, particularly during the warmer months when they are most active.

The bacteria is transferred through fly faecal deposits on common surfaces such as hand rails and door handles. Campylobacter deposited on fingertips can survive for at least an hour, and have been recovered from dry surfaces 24 hours after being deposited. (New Zealand Herald)

I haven’t read the original paper, so my criticism here is really unfounded. But I have a very hard time believing this, because t is pretty uncommon to trace disease outbreaks to flies (typhoid in the Spanish American War being one of the few historical exceptions). Now flies are admittedly pretty disgusting creatures. Insects have different kinds of mouthparts (biting, chewing, etc.) and domestic flies have sponging mouthparts. They essentially soak up their nutrients via a spongelike apparatus. In order to do this, the nutrients have to be liquified and flies do this by vomiting on the food to liquify it. After eating they also defecate on the food “(fly specks” come in light brown and darkbrown varieties, one being vomit, the other feces; thought you’d like to know). Flies also have very hairy legs and readily carry moist material from one place to another. Since they need to lay eggs in warm moist places, they frequently alight on masses of animal feces, picking up material when they do so.

I tell you these delightful things because I don’t much like flies. They are really hygienically nasty. But it’s very hard to find instances where they really have been shown to spread disease. The same with cockroaches. Cockroach guts are loaded with pathogens. I once took a class into the city hospital cafeteria and we trapped, ground up and plated out organisms from a cockroach (Periplaneta americana, for those interested in which one). We found the usual enteric organisms, including Salmonella spp. and if we’d assayed for enteric viruses we’d have found them, too. But it is very difficult to find instances in the medical literature that demonstrate cockroaches cause disease outbreaks. It is plausible they might. Most people think they do. But really showing it is another thing.

So when I see articles like this, which on their face present only a handwaving demonstration, I am skeptical, particularly when I see this:

The research, which appears in the New Zealand Medical Journal today, says eating chicken is also a “significant risk factor”.

The study warns that takeaway chicken meals are particularly risky if food is eaten without washing hands.

I can believe chicken is a risk factor, but not eating it without washing your hands as a risk factor is nonsense (to be fair, this is a newspaper rendition of the article; I don’t know what the original said or what the authors said to the reporter). Most foodborne illnesses require a significant inoculum of the organism to make someone sick, an inoculum usually only achieved by the organism growing to significant levels through a failure in food sanitation. This means the food is improperly cooked or has become contaminated by cross-contamination (e.g., contact with a cutting board used to cut raw meat) and afterward allowed to incubate for four hours or more. If just having it on your hands is enough to infect you, then eating cooked chicken is secondary. You could infect yourself in any way you put your hands in your mouth.

Campylobacter and many other pathogens increase as environmental temperature increases, so the relationship noted by the authors is plausible. But the implication flies are to blame is another matter. It could be true, but the medical literature rarely demonstrates it.


  1. #1 william
    August 22, 2006

    It is a relief to know flies ae not a reservoir for bird flu.
    It is also a relief to know 17 people in Garut, Indoesia, which is part of Cikelet, have bird flu symptoms, as reported today. I now feel much better, since in Forbes Magazine it says: “Experts have failed to uncover evidence of bird flu spreading between humans in a remote area of Indonesia, where 3 people have become infected with the virus, the World Health Organization said.”
    Now that WHO has reached this conclusion, we can safely conclude the 17 people in Garut were infected by sick chickens. It obviously does not matter these infections started more than 2 weeks ago in the village. It does not matter dogs were fed sick chickens by the villagers.
    I feel better knowing WHO will probably not investigate dogs as a possible mammalian reservoir for human H5N1 infections. Let sleeping dogs lie. It does not matter that in Thailand, investigators discovered dogs were asymptomatic carriers of bird flu. WHO should ignore these facts.
    WHO is doing an excellent job under these difficult field conditions in Indonesia. Of course all the sick chickens were probably culled weeks ago, but obviously chickens that are sick are secretly entering the village at night, and mysteriously infecting villagers. And if all chickens are killed in the village, there are probably guerrilla chickens that are sick, that sneak in at night and infect villagers.
    It is possible WHO reps will now recommend all villagers receive Tamiflu, and all those with bird flu symptoms need to have a vein opened in their arms, and large amounts of blood drained, in order to flush the virus from their bodies.
    This latter treatment was used in past centuries with great success. For example, they drained blood from George Washington, with obviously good results.

  2. #2 william
    August 22, 2006

    I forgot to mention that if this epidemic in Cikelet spreads beyond the 17 victims mentioned above, Vice President Dick Cheney, who is a certified psychopath; may have stated he will direct the CDC to stop this epidemic before it spreads.
    He may have said the best way to control the epidemic in the village is to send in the CDC, with instructions to shoot everybody, including the WHO investigators. He believes this method is much better then using Tamiflu. And if that does not work, he will shoot some more lawyers.

  3. #3 Tom DVM
    August 22, 2006

    Maybe we could blame H5N1 and the war in Iraq on flies as well.

  4. #4 David
    August 22, 2006

    Bush should declare Indonesia a “no fly zone.” That should solve it!

  5. #5 mugwump
    August 22, 2006


    * Sawabe K,
    * Hoshino K,
    * Isawa H,
    * Sasaki T,
    * Hayashi T,
    * Tsuda Y,
    * Kurahashi H,
    * Tanabayashi K,
    * Hotta A,
    * Saito T,
    * Yamada A,
    * Kobayashi M.

    Department of Medical Entomology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan; Department of Veterinary Science, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan; Department of Virology III, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan.

    During the outbreak of highly pathogenic avian influenza that occurred in Tamba Town, Kyoto Prefecture in 2004, a total of 926 flies were collected from six sites within a radius of 2.3 km from the poultry farm. The H5 influenza A virus genes were detected from the intestinal organs, crop, and gut of the two blow fly species, Calliphora nigribarbis and Aldrichina grahami, by reverse transcription-polymerase chain reaction for the matrix protein (M) and hemagglutinin (HA) genes. The HA gene encoding multiple basic amino acids at the HA cleavage site indicated that this virus is a highly pathogenic strain. Based on the full-length sequences of the M, HA, and neuraminidase (NA) segments of virus isolates through embryonated chicken eggs, the virus from C. nigribarbis (A/blow fly/Kyoto/93/2004) was characterized as H5N1 subtype influenza A virus and shown to have > 99.9% identities in all three RNA segments to a strain from chickens (A/chicken/Kyoto/3/2004) and crows (A/crows/Kyoto/53/2004) derived during this outbreak period in Kyoto in 2004. Our results suggest it is possible that blow flies could become a mechanical transmitter of H5N1 influenza virus.

    PMID: 16896143 [PubMed – as supplied by publisher]

  6. #6 revere
    August 22, 2006

    mugwump: I know this article (and commented previously here). You can find this virus in the environment. The question has always been, what is the effective way it transmits from bird to human or human to human. As I noted, flies and cockroaches are loaded with viruses and pathenic bacteria but rarely seem to be involved in disease transmission, at least as far as we’ve been able to ascertain. Presence of the virus in flies, etc., would be expected as mechanical transmitters. So far we don’t know it infects insects or the insects are a competent vector for this virus. Could be, but I’d bet against it. Just my hunch. I could be wrong, but so far there isn’t much (or any) evidence to suggest it other than the clear plausibility of mechanical carriage, which is essentially a hygiene issue. True reservoirs, like mammals that might harbor the virus, become infected and that is a different matter.

  7. #7 kyangadac
    August 22, 2006

    I’d have thought that there would be a good case for arguing that trachoma is spread by flies.

    You should also bear in mind that until fairly recently flies were in plague proportions in Australia and N.Z. because of the excessive amounts of (exotic) cattle dung lying around. The introduction of dung beetles in the 1970’s(IIRC) had a significant impact in Australia (don’t know the situation in NZ). You only have to look at old newsreel footage from Canberra to see the aussi wave being practiced by all, from royalty down, prior to the 1970’s.

  8. #8 william
    August 22, 2006

    The actions and statements on the Cikelet cluster by the WHO team proves beyond any doubt that to be a WHO investigator, they must first determine you are mentally challenged, or in other words, mentally retarded. The mental giants of WHO could not even find their own butts, much less H5N1.
    People with obvious bird flu symptoms are diagnosed as having Typhus. No tests are done on dead bird flu victims.
    Henry Niman said today, in very clear language, there is more efficient human to human transmission of H5N1 in Cikelet. Please read his comments at http://www.recombinomics.com.
    These infections started in Cikelet more than two weeks ago; so how could this be transmitted by sick chickens?
    And what about the dogs that ate the dead birds? Why doesn’t a brillant WHO investigator let one of those dogs lick his or her face for a while?
    Why do they not select blind investigators for WHO? They would be just as effective.
    Please do not turn these investigators loose in the US, if people in the US become H5N1 positive.
    If the situation regarding WHO investigators were not so tragic, since they are probably helping to kill people, it would be comic.

  9. #9 Kevin
    August 22, 2006

    William, you need to tone it down.
    We are all aware of Dr Niman and his website. You don’t need to parrot him here.

  10. #10 william
    August 22, 2006

    You need to mind your own business. Yor are not God.

  11. #11 william
    August 22, 2006

    Would you please explain to me why WHO and Indonesian Government officials continue to insist there is no evidence of H2H? Do you also believe there is no evidence of H2H?
    And if so, would you please explain why? And by the way, Kevin old buddy, I do not need to parrot anybody.
    There are now 5 Cikelet patients that died proior to collection of samples. Why were blood samples not taken? Are you in favor of not taking blood samples?
    Three of the deaths are related to patients who tested positive. Another problem is that Tamiflu will mask the presence of H5N1, making it more difficult to get positive results.
    The relationship, combined with the diseaase onset dates, meaning the dates are too far apart for there to be a single poultry source, demonstrates H2H
    How in the hell can WHO reps and Indonesian govenment officials keep giving us the same old crap, day in and day out, meaning no evidence of H2H. They know better and you know they know better.

  12. #12 Kevin
    August 22, 2006

    I’m in favour of a lower hysteria level, William.
    Assigning blame is pointless and makes tiresome reading.

  13. #13 william
    August 22, 2006

    You did not answer my question. Do you believe WHO representatives when they say there is no evidence of human to human transmission of H5N1?
    I am sure you are very intelligent, I would like to know what you think about the presence of a large human cluster in Cikelet.
    Let me for a moment parrot or quote Revere, from a previous post, when he spoke about H5N1 human clusters:
    “Cases closer together in space or time (or both) are of interest only for what they can tell us about what is going on about disease transmission and occurence. Many people can be infected within a few days by a common source, (eg. poultry), with a virus that is passing more easily to humans. On the other hand, people falling ill a week or so apart might indicate person to person transmission if they have had indirect contact with each other.” I am not sure this is the exact quote, but I think it conveys the correct meaning
    Kevin, I would only humbly submit to you that what is happening in Cikelet meets the latter rather than the former case, as stated above by Revere. This disease transmission of H5N1 has been occurring for over 2 weeks in Cikelet.
    Let me try to say it as simply as I can. If many people get sick at about the same time, within a week’s period; then we can conclude they became sick as a result of exposure to poultry.
    But if they become sick over a period of time that exceeds a week, then something else is probably infecting these people. We are now at more than 2 weeks, and people continue to get sick and die. This may very probably mean H2H exists there.
    We have a failure to test the blood of 5 people who have died. If the sequences from those who died fail to match an avian source, then how can you say the source is sick birds. Andrew Jereminko, a virologist who has worked for years in Indonesia, says the only match they have is from a cat.
    Since dogs ate the dead birds, they may be infected with bird flu. But they are not being tested. If it is not H2H, a more logical procedure would be to test the mammals in the area, to determine if some type of mammal, such as a cat or a dog, is a reservior, meaning people continue to become infected through contact with a mammal.
    I am sure others can explain this to you much better than I can, but I hope you understand what I am saying.
    For WHO representatives to continue to insist there is no evidence of H2H just does not make sense. The very fact we are at over 2 weeks with this cluster is itself evidence.

  14. #14 Kevin
    August 22, 2006

    William, my point is that regular readers of this blog are well acquainted with Niman, Webster, Osterholm, the WHO web site, CIDRAP, Pro-Med, etc. I read them all myself. I don’t particularly want or need a situation update or synposis of the latest postings elsewhere, especially of “the sky is falling” variety. I would prefer comments stay on topic with the post commented upon (flies, in this case). I don’t run this place, I just read it, so it’s only a suggestion. There are lots of places that welcome this sort of posting – the Flu Wiki has a thread for everything. Indulge in WHO conspiracy theories there.
    A personal suggestion: use some of this frentic posting energy to prepare your household and your community.
    I’ve done what I can to prepare myself and my household, and knowing I’ve done that helps my perspective. You need to be prudent, but life is short, and you cannot devote it all to obsession with H5N1.

  15. #15 caia
    August 22, 2006

    William, I think Kevin made a reasonable suggestion, although you’re technically correct that he is not god. In this, god would be Revere, who would probably strenuously object to the label. I don’t think you need automatically dismiss all criticisms from someone other than the blog owner just because they technically have no ability to silence you. Besides, if you ignore their objections, why should they respond to yours?

    We are all here because we either are concerned about the progress of H5N1, or we’re interested in public health, or both. In such a self-selected audience, you may rest assured that most readers are aware of the existence of Dr. Niman. You may be assured that most are likewise concerned about the structural and strategic weaknesses of the WHO. (If you doubt that, just go back and read the comments on Revere’s multi-part series on the history of the WHO which is posted at the old blogsite; and read Revere’s final assessment of WHO, as well.) Therefore it is tiresome to be ranted at in hyperbolic terms on every other post as if we were unaware of either of those things.

    I am not even a local god, but I think you should know that I’ve started skipping past your comments. If your goal is to reach more people, then toning it down as Kevin suggests is a good idea. (If your goal is to rail at people who share your interests and concerns, by all means, carry on.)

  16. #16 Nancy
    August 22, 2006

    Caia wrote: “I think Kevin made a reasonable suggestion, although you’re technically correct that he is not god. In this, god would be Revere, who would probably strenuously object to the label.”

    Strenuously? Apoplectically is more like it.

  17. #17 Tom DVM
    August 22, 2006

    Caia. I have to say that your post at 10:08 is a fine piece of writing. Thanks

  18. #18 william
    August 22, 2006

    I apologize to you, Kevin, and all other readers for ranting.
    The Cabinet in Thailand was told yesterday by medical specialists in the country human flu is spreading rapidly.
    The clusters in Indonesia, especially Cikelet, continues to grow and people continue to die.
    But all government officials in Asia and WHO representatives can talk about are sick chickens as the source. To me this is insanity.
    But I will try to keep my comments at a more rational level.

  19. #19 caia
    August 22, 2006

    Nancy: Probably. *g* Tom DVM: Thanks. William: Thank you as well, for listening. I do appreciate it.

    I agree with you that testing of other possible animal vectors is a good idea, and have ever since I heard about “aaargh plop”; unfortunately, I’m not a local god there, either, and can’t make that happen. And it worries me that WHO’s lag time in investigating and intervening seems to be so great. (This concerns me far more than them publically downplaying the danger; I could take a bit of smokescreening more readily if I felt they were on the ball behind the scenes.)

    Even if the situation seems to warrant it, I cannot tear my hair out every time they occur. (I reserve the right to freak out at any time in the future.) What you may see as complacency or lack of concern on the part of fellow commentors may just be a wait-and-see attitude as a result of having watched previous outbreaks in Karo, in Turkey, etc.

  20. #20 revere
    August 22, 2006

    william: I am in agreement with Kevin, here. You need to get a grip. This is a potentially deadly serious business that requires a clear head, clear thinking and a willingness to mobilizing the community to face what might happen. The harangue against WHO, CDC and others is unhelpful and misplaced. I have been very critical of them here, but I also have an appreciation for what a difficult job they are doing and one that can be quite dangerous. You are manning a keyboard. You aren’t in the field. Many a WHO employee has died ridding the world of SARS, smallpox, riverblindness and more. We need to support the many good and dedicated people within those agencies while being constructively critical to strengthen their hands.

  21. #21 g510
    August 22, 2006

    Here’s my vote for “Cut the metaprocess, dammit!”

    Back to topic.


    Seems to me this shouldn’t be an either/or but an and/both. On one hand, as a matter of science we need to know if or to what degree various insects could be vectors (mechanical or otherwise) for emerging diseases. On the other hand, even if the answer is “little to none,” good sanitation still calls for minimizing insect nuisances: keeping the damn flies & roaches away from food, refuse, etc., keeping streets & public areas clean particularly of animal wastes, and so on. There is nothing to be gained from reducing attention to basic sanitation practices that should be second-nature to the point of nearly reflex behaviors. And regardless of whether insect droppings on common surfaces are a verifiable vector path for a specific disease, there are enough other sources of infection that use common surfaces (e.g. people who cough or pick their noses and then put their hands on doorknobs), that regular hand-washing should also be second-nature to the point of reflex.

    Regardless of scenario or situation, getting lax about basic sanitation necessarily complicates matters further. And as a quick peek in any public WC shows, it’s not like we’ve already won those battles hands-down to the point where we can take it easy.

  22. #22 revere
    August 23, 2006

    g510: I of course agree with your excellent points. The only additional point I would make, however, is that sometimes the cure is worse than the disease, as in the case of pesticides and cockroaches.

  23. #23 revere
    August 23, 2006

    kyangadac: You make a good point about trachoma. I was mainly referring to Musca domestica and enteric or respiratory infections, however. Eye-seeking flies like M. sorbens are more likely to carry the chlamydial organism of trachoma, but your point about trachoma is broadly correct.

  24. #24 william
    August 23, 2006

    You are correct. I am not in the field risking my life, so I have no right the criticize people who are. It is easy to criticize from a distance.
    I am an American living in Medellin, Colombia; and if the pandemic hits here, the situation could get really bad, very fast. But I will do what I can to organize family members and to help the sick. I have learned much from you about getting the community ready. It appears to me the storm clouds are already forming, and time is running out.
    What woke me up is when you said “This is a deadly serious business.” Thanks to you many people will be ready when the storm hits.

  25. #25 gaudeamus
    August 23, 2006

    Campylobacter is a very interesting organism. It is part of the normal gut flora of dairy cows and chickens, as well as flies, and now causes more food poisoning in the US than salmonella and shigella combined. At least half of the cases are due to raw poultry exposure. Raw milk products are also cited as a source.

    I recall a case study where about 20 college students became ill after consuming raw milk at a farm. The farmer and his family drank the same milk and did not become ill. This makes me wonder if Campylobacter wasn’t once a more prevalent contituent of human gut flora as well?

  26. #26 Marissa
    August 23, 2006

    Recently it was proved beyond a doubt that M. sorbens is a mechanical vector for trachoma. M. ventustissima is also a likely candidate in Australia. However, none of these are bug repositories.

  27. #27 caia
    August 23, 2006

    Gaudeamus: Interesting case. Could it also be that the farmer and his family had frequent exposures to Campylobacter which built their resistance (to their own cows’ strain)? Or perhaps they just had more “friendly” gut bacteria to be able to balance the Campylobacter? College students aren’t known for having the healthiest diets.

    I don’t know if either of those are plausible, forgive me if they’re not… just wondering.

  28. #28 FrenchieGirl
    August 24, 2006

    We have discussed flies as in mechanical vector, as in H5N1 from flies’ feet being deposited on food. Old memories remind me that in some places of Africa, you cannot let your washed linen dry on a line outside, because flies/insects make eggs on them and then infect you with some type of parasite. In some parts of the world, some insects are considered delicacies, such as grasshoppers, some other insect in Central Africa which you roast and present with your first round of drinks at dinner time… Do they eat insects in Asian countries?

  29. #29 gaudeamus
    August 24, 2006


    Thank you for your reply. Yes, it seems a plausible notion that the farmers do have immunity due to previous exposure – something the idustrialized world doesn’t enjoy.

    The same idea seems to apply to allergies as well – sterile environments and low exposure to life on earth = lots of allergic people. A study comparing East Berlin to West Berlin before the wall came down supports this.

  30. #30 Ground Zero Homeboy
    August 24, 2006

    If five people sleep in a hut, and one of them has a blood-borne disease like Hep B or HIV, and a mosquito makes its rounds…

    How can it not spread the disease?

  31. #31 revere
    August 25, 2006

    GZB: There is more to vector-borne spread than just having it in the blood and being bitten by a mosquito. The virus has to reach sufficient levels in them mosquito to be an effective inoculum and it has to reach those levels in the mosquito salivary glands, then be injected during a bite. The virus has to reach sufficient levels in the human’s blood to be efficiently transmitted to the mosquito. The immune defenses at the bite site must also be insufficient, etc. As far as we know (and it has been looked at a lot) Hep B and HIV are not mosquito borne. It may seem plausible, but it doesn’t happen.

  32. #32 Albert
    August 26, 2006

    Frenchiegirl: Yes, in large parts of Africa, some flies deposit their eggs on drying clothes and the larvae bury in the skin after hatching. That is why we had to iron all clothes after drying, even undergarments. I was lecturing the subject of medical entomology in a medical college in Lusaka, Zambia at the time but even I got infected with several larvae of the Tumbu fly (Cordylobia anthropophaga). Fortunately not in as sensitive a place as my colleague 🙂

  33. #33 Paulene
    September 27, 2006

    Does anyone know if many or if any people through the years have dies after eating food that a fly had thrown up on or deficated on? If so, please send me the article or whatever proof you have of this, as my husband and I have a bet going that people have indeed dies from it. He says no otherwise we would have heard of it on the news.

  34. #34 revere
    September 27, 2006

    Paulene: There is pretty good evidence for preventing typhoid with good fly control (Spanish American War). Probably another case or two, but not much. Practically nothing for cockroaches.

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