Health Wanted: Rats

The Episode

Rats—they are often seen as pests or spreaders of disease, but they are also surprising public health heroes. This week on Health Wanted, host Laurel Bristow explores the role rats play in disease transmission, from the Black Death to modern outbreaks, and uncovers their contributions to science, from sniffing out landmines to serving as human proxies in lab studies. Then, she is joined by Kaylee Byers, PhD, to talk about the history of rats and humans existing together.

Listen to the episode now

The Listener Questions

Is the sex of a baby completely determined by sperm, or are there other parental factors that influence it?

A recent study suggests that, while the sex of the baby is determined by if the egg is fertilized by a sperm with an X or X chromosome, there could be maternal factors that influence if a X or Y sperm is successful in fertilizing an egg.

The study does not sway me particularly hard that maternal factors have a huge impact on sex.  The strongest connection they found was between maternal age and the likelihood of having multiple kids of the same gender, implying something about the way the reproductive environment changes and becomes preferential to certain sperm.

But they didn’t look at paternal age, so who’s to say it’s not that the environment of older fathers influences which sperm survive?

The genetic analysis is also pretty weak. It found some similar gene expression in a small number of people who had more kids of one sex. But that association isn’t causation, and there could be other factors that influence that gene expression.

So, right now there is not solid enough data to say that the sex of a baby can be predicted or engineered when pregnancies occur the old-fashioned way.

Why did a test show that I’m not immune to measles, even though I was vaccinated as a child? How can I protect myself and my baby from measles during pregnancy?

First, to be clear: Just because your measles titers are low or even show zero, it doesn’t actually mean you’ve lost immunity and are as susceptible to measles as a newborn baby.

You have an immune memory that can be activated to produce new antibodies. Some people have what’s called “secondary vaccine failure,” which is when they don’t produce enough antibodies, and they do get the disease. Those cases tend to be mild, because the vaccine still reduces the severity.

Lowered antibody titers can happen over time with some people because their immune system doesn’t keep those antibodies stocked when they aren’t exposed to the pathogen.

There are two main reasons why we want to give measles, mumps, and rubella (MMR) vaccines to people who might have low levels and are trying to get pregnant:

1. To help them develop more actively circulating antibodies to measles, which can be passed to their baby during delivery. Those antibodies provide stronger passive immunity until the baby hits the age where they get vaccinated themselves.
2. Having low titers for rubella when pregnant is actually a bigger problem than measles. Rubella infection in pregnancy can cause the baby to be born without the ability to hear.

If you have no immune levels for measles, mumps, or rubella while you are pregnant they will likely want to give you one dose of MMR after delivery, before discharge. That is so you can have some passive immunity to give to your baby through breastfeeding, and also so that you’re set if you have more kids in the future.

For everyone who is not planning to become pregnant, documentation that you received the appropriate number of vaccinations for your circumstances supersedes laboratory tests of your antibody levels as proof of immunity. 

Now, you may be wondering how many vaccine doses you should have had, or when additional doses are recommended:

• If you were born before 1957, it’s assumed you’ve had measles and you do not need to get any vaccine doses. The exception is if you work in a health care facility, in which case you should consider one MMR vaccine if you’ve never been vaccinated. If you work in a facility that is located within an active outbreak it’s recommended that you get vaccinated.
• If you were born in 1957 or later and have documentation that you have received at least one live measles vaccine, or you have laboratory confirmation of a prior infection or immunity, you do not need additional doses.
• If you were born in 1957 or later but you have no evidence of any vaccination, nor laboratory confirmation of infection or immunity, you need one dose of live MMR vaccine.
• If you were born in 1957 or later and work in a health care facility, are an international traveler, or are attending secondary education or college, and you do not have any evidence that you’ve gotten vaccinated or have antibodies in your blood, you should get two doses.

High-risk individuals without proof of vaccination or immunity should get the full series. Two doses, at least 28 days apart.

Catch all the listener questions and Laurel’s answers on the full episode of Health Wanted by:

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