BACKGROUND INFORMATION Some mosquito-borne pathogens, like the dengue, chikungunya, and Zika viruses, cause diseases for which there are not yet effective treatments or vaccines. Zika virus in particular has spread to more than 80 countries to date, making it a global concern. Zika can cause a debilitating illness of the nervous system called Guillain-Barré syndrome and, when a pregnant woman is infected, severe birth defects including microcephaly. An increasingly common approach to preventing the spread of these diseases is to target mosquito fertility rather than use insecticides, which can have negative environmental effects. One of these techniques involves using the naturally occurring Wolbachia bacteria that infect mosquitoes, making them, in some cases, infertile. When male mosquitoes are infected with Wolbachia, they must mate with an infected female to produce viable embryos. If they mate with an uninfected female, their sperm are unable to go through mitosis after embryo formation. Consequently, in the field, after mating with a Wolbachia-infected male, an uninfected wild female will lay eggs that never hatch. This is called cytoplasmic incompatibility.

What’s the claim, reasoning, and evidence.

Additional Discussion Questions (optional)

1. Describe the differences in the percentages of eggs hatched between treated and untreated sites.

2. During which months do you see the greatest impact of the treatment? Why do you think that is?

3. Why is it important to include untreated sites in this study?

4. Describe what the error bars mean in this figure. How do you interpret the differences between treated and untreated?

5. What type of statistical analysis would convince you that the decrease in the mean percentage egg hatch in the months of June, July, and August was statistically significant?

6. Why do you think the researchers chose to release only male mosquitoes instead of both males and females?

7. Why didn’t the release of infected males result in zero eggs hatched at the treated site?

8. If this site was left untreated the following year, predict what this same graph might look like.

9. Based on these results, would you recommend treatment with Wolbachia as a way to reduce A. albopictus mosquito populations? Why or why not?