UC Davis tick study, rural northern California

Below is the complete text of an article by UC Davis entomologists describing a study conducted in a watershed near Ukiah, California, in 1988-89. The crucial piece of information it contains for northern California residents is on page 45 in the following quote:

Except for [a particular study in the northeastern U.S.] the cumulative frequency and annual incidence of Lyme disease in the Ukiah study area are comparable to, or higher than, the cumulative frequencies/incidences reported from the Northeast.      Robert Lane

This refutes any claim made by California doctors or insurance providers that Lyme disease does not exist in California or is so rare in California as to justify their treating you like a mental case when you suggest you might have it. In a paper presented at a Lyme conference in 1999, Phyllis Mervine, publisher of Lyme Times magazine, includes this study in a group of three similar studies and compares the results of those studies to California Department of Health Services statistics. [VIII International Conference on Lyme Borreliosis in Munich, June, 1999, published in Lyme Times, No. 28, Spring 2000, p. 35, “Risk of Lyme Disease in California.”]

In describing the study presented below, Mervine cites a later study by Lane and Talleklint-Eisen of ticks in 5 California counties. (The counties are not named, but it is a reasonable assumption that they include the four in Lane’s earlier study.) In that study, the researchers found that nymphal I. pacificus ticks, nymphs being more likely to be carrying Bb in this species, were infected with Lyme disease from 4 to 41% of the time. The average for nymphal ticks at all the sites considered was 14%. That means that at some of the sites, 41% of the nymphal ticks could infect humans with Lyme disease. [Talleklint-Eisen, L. and R. S. Lane, “Variation in the Density of Questing I. pacificus Nymphs Infected with Bb at Different Spatial Scales in California,” J. Parasitology, 85 (7), 1999.]

I have, myself, heard Dr. Lane say at a conference in Ukiah, that those figures vary with micro-environment and annual weather conditions, which indicates to me that though they could be lower, they could also be higher. (I wish I could provide the year of that conference in the name of better scholarship, but I can’t because I have Lyme disease and don’t have the energy to sustain normal scholarly standards. You’ll just have to believe me or not believe me on that one.)

At even the most literate of Lyme doctors’ offices, I have seen Lyme disease information sheets posted that include the widespread but highly distorted 2% figure for I. pacificus ticks infected with Bb. Well, I saw it on my Lyme doctor’s bulletin board and called him on it, whereupon he told me others had posted it and he certainly was not using that number as a guide to anyone’s probability of having Lyme disease. But, that is the figure almost all doctors are using to calculate your probability of having contracted Lyme disease from your I. pacificus tick bite.

That figure comes from one study and one study only, done in 1989 by William Burgdorfer, the scientist who discovered the Bb pathogen that causes Lyme disease. Burgdorfer did not design his study to discover the percentage of I. pacificus ticks infected with Bb and probably never meant for it to be used this way. It is not based on a controlled sample. He merely asked people to send him ticks from anywhere in the range of I. pacificus, which includes most of the West. It is known that the percentage of infected ticks varies greatly from one spot to another. Lane’s studies show this. No control was done in Burgdorfer’s study to insure that more ticks did not come from some areas than others and the 2% is an average for the entire huge range of I. pacificus.

Right there are two enormous sampling errors, if the study had been designed to produce an incidence statistic for Bb in Pacificus ticks, which it was not. Yet, based on that one study, even Lyme doctors will use that number to assess your chances that the tick that bit you was bearing Bb. Non-Lyme doctors will use it to ridicule and not diagnose you; insurance companies will use it to deny you treatment and, probably, Lyme research funding organizations will use it to determine where research should be done, i.e., on the East coast, where that number is much higher.

In her conference presentation, Mervine states that the California Department of Health Services studied four nothern counties and then revised an earlier low Lyme incidence rate for Humboldt County (14 per 100,000) to 66 per 100,000, a rate double the incidence rate for New York state at that time. The point is that persons considering the probability that a tick bite from I. pacific us has given them Lyme disease must not allow themselves to be misled by doctors using incidence statistics for the state as a whole or for the infection rate of I. pacificus nymphs as a whole.

If you were bitten in Humboldt, Mendocino, Sonoma or Lake counties, the incidence rate for California, .5 per 100,000, which averages in counties with a zero incidence, does not apply to you. Those four counties, said Mervine, are responsible for the bulk of reported cases in the state, at least in 1999, when the paper was presented. If the incidence rate for those four counties alone is calculated, relating Lyme cases to the population of those four counties alone, using figures from 1991 to 1995, the incidence rate is from 9 to 74 per 100,000 people, as high or higher than that rate on the East coast. And, even those figures can be assumed to be a fraction of the truth, given the enormous number of cases that do not meet the unrealistically stringent reporting criteria used by public heath entities, following the lead of the Centers for Disease Control.

On top of all that the CDC itself has always said that, in order to get the true incidence of Lyme disease in any given area, one must multiply their incidence by a factor of ten! They acknowledge and even specify to doctors that their reporting criteria are too narrow to be used for diagnosis and only catch a tenth of the real cases. Its just that doctors and insurance providers routinely ignore them on this.

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2 Responses to UC Davis tick study, rural northern California

  1. Ruby hubbs says:

    I 1st got Lyme in 1992 & again in 1999 ?

    • Jentri says:

      I’m not sure if you are asking me a question, but I’ll answer it anyway. If you know for sure you got it in 1992, there is no way to know for sure if you ever completely got rid of it in the sense that you eliminated the bacteria from your body. Antibiotic treatment will cause some of the bacteria to take on forms that cannot be detected by tests, while causing your symptoms to abate. But, the bacteria are still there and, in fact, are multiplying. When conditions are favorable, i.e., the antibiotics have stopped and your immune resistance is low, perhaps from another disease or stress or menopause or pregnancy, they will emerge and start causing symptoms again. Your 1999 case could simply be a resurgence of your 1992 case. Why does that matter? Because it should be treated as a late, not an early, case and the treatment is different. Also, if the 1999 case followed a known tick bite, you should know that any tick bite, not just the bite of a Lyme-bearing tick, can cause Lyme symptoms if you already are infected. The bacteria already present, the ones in the forms that do not cause symptoms, are reactivated by the saliva of any species of tick. Again, not a new case, but a resurgence of the old case.

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