TOUCHED BY LYME: Got MALC? Try this interactive tick & Lyme map

This week, someone from San Mateo County posted this on Facebook: “My grandmother was bitten by a tick yesterday in our own backyard, and has a bullseye rash clear as day. But upon calling Kaiser, the advice nurse told us that there are no infected ticks in California (wrong), you shouldn’t worry about Lyme Disease unless you’re from the east coast or have a fever following a bite (also wrong), and bug bites don’t need medical attention unless they start to ooze (very wrong).”

I was chagrined but not surprised. Another case of MALC—Medically Acquired Lyme Cluelessness. (It’s a highly contagious condition that runs rampant in the medical community in California and many other states.) Alas, being inaccurately told by medical professionals that Lyme is rare or non-existent around here is the unfortunate norm, not the exception.

So, I’m pleased the State of California has unveiled a project that has been in the works for a while. It’s an interactive map showing tick and Lyme data for each county.

See, for years, the California Department of Public Health and other agencies have collected ticks in some parts of the state and tested them for Lyme disease. But until now, there’s never been an easy way for the public to access the data.

Here’s how it all works. You click on the link that takes you to a state map, and then you click on the county in question. Up pop summaries for how many blacklegged ticks have been reported there since 1985 (broken down by larval, nymphal and adult stages), how many tested positive for Lyme, and how many human Lyme cases by county of residence from 2002 to 2011.

Things to keep in mind:

1. Some parts of the state have had little or no tick surveillance, so there are no numbers to report. On the map, purple diamonds show where ticks have been collected. Having few or no purple diamonds doesn’t mean the county is free of ticks—just free of tick data.

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2. The number of human Lyme cases is kept artificially low because California follows the CDC’s highly restrictive surveillance criteria. As a result, health officials toss out many thousands of positive Lyme cases, which will never show up on this map. (Click here for more discussion of that problem.)

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3. It’s important to remember that people are more likely to get sick from nymphs, which typically have a higher infection rate than adult ticks. They are also so small that people often fail to see and remove them, increasing the possibility of disease transmission. Nevertheless, most tick surveillance studies involve adult ticks, which are easier for researchers to find. This can skew the perception of what your risk of infection actually is.

Keeping those three points in mind, let’s look at our example of San Mateo County. Both adult and nymphal deer ticks have been collected in the county, with about a 2% Lyme infection rate for both. Not huge numbers, to be sure, but not insignificant either.

In Mendocino County, 1% of adult ticks are infected with Lyme, while 10% of nymphs are. Sacramento County has an adult infection rate of .4%, with a nymphal tick infection rate of 23%. In Contra Costa County, 1.5% of adult ticks are infected, while 23% of nymphal ticks are.

Now take a look at San Luis Obispo. According to this, there’s never been a Lyme-infected tick in the whole darn county! However, the paucity of purple diamonds shows us there hasn’t been much tick surveillance there either. Some adult ticks have been collected in three locations, none infected with Lyme. No nymphs. So the fact that SLO County reports a 0% Lyme infection rate for ticks is basically meaningless.

I know people who were bitten by ticks in SLO and subsequently developed Lyme disease. Many were told by their doctors there’s no Lyme in their county. (Relying on inadequate data could lead you to draw that conclusion, yes?) More surveillance, in different locations, with an emphasis on finding nymphs, might paint a different picture. However, with current budget woes, that’s unlikely to happen any time soon.

Officials say new data will be added to the interactive map as it becomes available. With additional information from future tick studies, its value as an awareness tool should continue to expand.

Unfortunately, MALC can be even more difficult to eradicate than chronic Lyme disease. At least in some counties, this map should prove a useful tool to those trying to educate MALC sufferers that yes, you can catch Lyme disease in California.

So the next grandmother with a bull’s-eye rash after a tick bite won’t be denied treatment by a medical organization which surely ought to know better.

Click here to see the maps and statistics for yourself.

TOUCHED BY LYME is written by Dorothy Kupcha Leland, LymeDisease.org’s VP for Education and Outreach. Contact her at dleland@lymedisease.org.