If you're enjoying the outdoors this summer, whether at a barbeque or hiking in the woods, you know it can be hard avoiding pests who want to take a bite out of you. After all, the season of outdoor fun is also peak season for bugs like mosquitoes and ticks.
But public health experts advise that preventing bites is important - especially as some vector-borne illnesses, like Lyme disease, become more widespread.
"Over the past years, we have seen an uptick in reported tick-borne disease cases," said Chantal Vogels, an assistant professor of epidemiology (microbial diseases) at the Yale School of Public Health. "Several explanations contribute to this upward trend, including expanding tick populations due to changes in land use and more favorable environmental conditions, improved awareness and detection, behavioral changes, and other factors."
In an interview, Vogels discusses the most common vector-borne diseases, when you should see a doctor, and the best ways to "fight the bite."
The interview has been edited for length and clarity.
Most people think of summer as the season for mosquitoes and ticks. When can we expect to see ticks and mosquitoes outside?
Chantal Vogels: Mosquito and tick activity generally starts increasing when temperatures warm up during the spring. Peak activity is reached over the summer and decreases again during the fall when days get shorter and temperatures start to drop. Most mosquitoes and ticks are dormant during the winter, but some species will remain active, and warmer winters can result in prolonged activity.
During these warm months, which vector-borne diseases are most common? Are certain groups of people at higher risk for disease?
Vogels: Several vector-borne diseases are circulating in the United States. West Nile virus is one of the most common mosquito-borne viruses. The virus is transmitted in a natural transmission cycle between Culex mosquitoes and birds. Humans can become infected via the bite of an infected mosquito but do not contribute to onward transmission. In principle, anyone can become infected with West Nile virus, but the majority of cases will remain without symptoms. An estimated 20% of infections result in fever, and less than 1% develop severe disease. Particularly older or immunocompromised individuals are at increased risk of severe disease.
Several tick-borne illnesses are present in the U.S., including diseases caused by bacteria like Lyme disease and Anaplasmosis, protozoa like Babesiosis, and viruses like Powassan virus. Of these, Lyme disease is one of most common tick-borne diseases, particularly in the Northeast and Midwest where it is spread by the blacklegged tick, Ixodes scapularis. People spending a lot of time outdoors are at highest risk of acquiring tick bites and becoming infected with tick-borne pathogens.
With mosquitoes, we often know if we've been bitten thanks to itchy bumps on our skin. But with ticks, it's sometimes not as obvious. How can we determine if we've been bitten by a tick, and what symptoms should we look out for?
Vogels: Mosquitoes typically feed for very brief periods of time, whereas ticks can feed for several days. A tick bite is therefore most easily recognized when the tick is still attached to the skin. It is important to check yourself for ticks after spending time outdoors. Immature [ticks] can be as small as a poppy seed, so careful inspection is critical. Early removal is key to decrease the risk of tick-borne pathogen transmission, which in many cases can take 24 hours or longer.
However, transmission may occur faster. For example, laboratory studies have shown that the tick-borne Powassan virus may be transmitted within 15 minutes after tick attachment. After removing a tick, it is recommended to take note of the date and monitor for the development of fever or rash during the following weeks. If any of these symptoms develop, then it is recommended to see your doctor.
If someone is concerned about a tick or mosquito bite, when should they see a doctor? What treatments help?
Vogels: If you develop febrile illness [fever] or a rash after a tick bite, then you should talk to your doctor. Antibiotic and antimicrobial treatments are available for Lyme disease, Anaplasmosis, and Babesiosis, but treatment depends on the stage and severity of disease. No specific treatments or vaccines are available for the majority of mosquito- and tick-borne viruses, including West Nile virus and Powassan virus.
Step into any store, and you'll see a variety of products designed to repel mosquitoes and ticks, from zappers and candles to sprays and bracelets. What are the best ways to protect ourselves from these pests?
Vogels: Avoiding mosquito and tick bites is the most effective way of preventing disease. While many products are on the market, there is limited evidence for their effectiveness. The main mosquito species that transmits West Nile virus is most active during dawn and dusk. Staying inside during peak activity or covering yourself up with loose-fitting long-sleeved shirts and pants and using Environmental Protection Agency [EPA]-registered insect repellents on exposed skin are most effective in preventing mosquito bites. You can also control mosquitoes in and around your house by screening windows and doors, using air conditioning, and frequently emptying any water-holding containers - like buckets, flowerpots, birdbaths, and trash - to remove potential mosquito breeding sites.
Tick bites can be acquired when spending time outdoors, particularly in brushy or wooded areas with tall grass and leaf litter. When spending time outdoors, it's recommended to wear permethrin [a type of insecticide]-treated long-sleeved shirts and pants and use EPA-registered insect repellents on exposed skin. Showering and carefully checking your body for ticks is important for early removal of ticks to lower the chances of tick-borne pathogen transmission.
