Almost everyone has been bitten by a mosquito, tick, or flea. All these organisms are vectors, Vectors  are living organisms that can transmit infectious pathogens between humans, or from animals to humans.

Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later transmit it into a new host, after the pathogen has replicated. Once a vector becomes infectious, they can transmit the pathogen for the rest of their life during each subsequent bite/blood meal. Some vector-borne diseases, like plague, have been around for thousands of years. Others, like Heartland virus disease and Bourbon virus disease, have been discovered recently.

Bugs, including mosquitoes, ticks, fleas, and flies, can spread diseases such as malaria, yellow fever, Zika, dengue, chikungunya, and Lyme. While some cases are mild, these diseases can be severe and have lasting consequences. Some diseases caused by bug bites can be prevented with vaccines or medication, like yellow fever and malaria; however, many cannot, such as Lyme.

Certain groups of people are at a higher risk for disease than others due to behaviors or geographic location that put them in contact with ticks and mosquitoes. Additionally, certain groups of people are more likely to develop severe disease, such as older adults and those who have weakened immune systems. Many vector-borne diseases are preventable, through protective measures, and community mobilization. Understanding risks of vector-borne diseases can help you know when and where to expect ticks and mosquitoes. Learn more about steps you can take to help your volunteers and staff avoid bug bites.

In California we have about 100 common arthropod species (mosquitoes, cockroaches, lice, true bugs, flies, fleas, bees, wasps, ants, ticks, mites, spiders, and scorpions) of public significance because of their impact on human health. Today we will just look at mosquitoes and ticks.

Mosquitoes are arguably the most medically important group of insect vectors.  In addition to causing severe annoyance and allergic reaction, mosquitoes found in California are capable of spreading many diseases to humans and animals including: Chikungunya, Dengue, Filariasis (canine and feline heartworm), Malaria, Saint Louis encephalitis (SLE), West Nile virus (WNV), Western Equine encephalitis (WEE), Yellow fever, and Zika.

In California, we have about 50 species of mosquitos and of those, only a few are considered public health threats due to their potential to transmit mosquito-borne diseases to humans. Historically, California has experience local transmission of malaria, Western Equine encephalomyelitis (WEE), St. Louis encephalitis (SLE), California encephalitis viruses, canine heartworm, and West Nile virus (WNV).  Canine heartworm and West Nile virus continue to have frequent local transmission in California with West Nile virus human cases numbering in the hundreds every year.  However, with increased global travel, the potential for the introduction or reintroduction of many mosquito-borne diseases into California still exists.

West Nile virus (WNV)  is the most common and serious vector-borne disease in California? There have been more than 7,500 human cases and over 300 deaths reported in California since 2003. The mosquitoes that spread WNV are found throughout the state. People who have been bitten by a mosquito infected with viruses such as West Nile, Saint Louis encephalitis, dengue, and Zika may develop life-threatening or life-altering diseases.

West Nile virus is a mosquito-borne virus that causes disease in humans, horses, and birds. WNV spreads to people through the bite of an infected mosquito, and it can make people sick and even cause death. WNV is common in the United States, especially in California, and is a problem that is here to stay. The best way to prevent WNV is to protect yourself from mosquito bites.

Mosquitoes often get WNV from birds (see image to left). Dead bird reports are one way of tracking where WNV could be spreading. You can help the California Department of Public Health (CDPH) track WNV in California by reporting dead birds (Report a Dead Bird https://westnile.ca.gov/report).

Ticks are parasitic arachnids that are part of the mite superorder Parasitiformes. Ticks can transmit an array of infectious diseases that affect humans and other animals. In California there are several different types of ticks and they transmit a number of different diseases. Some diseases that ticks can transmit in California are: Anaplasmosis, Babesiosis, Ehrlichiosis, Lyme disease, Rocky Mountain Spotted Fever, and Tick-Borne Relapsing Fever.

Once a tick finds itself on its host it will immediately begin to look for an appropriate feeding site. Finding a site to feed typically takes a little as 10 minutes but can last as long as 2 hours. When the tick finds a sufficient feeding location it punctures the skin of its host and inserts a feeding tube that secretes a cement like substance and has barbs to help the tick to stay attached to the host. Ticks also secrete saliva onto the punctured area that acts as anesthetic so the host will not feel the tick cutting into the skin. This allows the tick to stay attached to the host longer because they go unnoticed by the host. Once a tick is attached it will then feed on the hosts blood meal for several days and then detach itself from the host. If the tick was infected with a pathogen it may transmit the infection to the host species through its saliva entering the hosts blood stream.

The Lyme disease bacteria causing human infection in the United States, Borrelia burgdorferi and, rarely, B. mayonii, are spread to people through the bites of infected ticks. Borrelia burgdorferi is spread primarily by the western blacklegged tick (l. pacificus) in the Pacific Coast states.

Blacklegged ticks have a 2-to-3-year life cycle. During this time, they go through four life stages: egg, larva, nymph, and adult. After the egg hatches, the larva and nymph each must take a blood meal to develop to the next life stage, and the female needs blood to produce eggs.

• Female ticks infected with Lyme disease bacteria do not pass them to their offspring.
• Deer are important sources of blood for ticks and are important to tick survival and movement to new areas. However, deer are not infected with Lyme disease bacteria and do not infect ticks.

In most cases, a tick must be attached for 36 to 48 hours or more before the Lyme disease bacterium can be transmitted. If you remove a tick quickly (within 24 hours), you can greatly reduce your chances of getting Lyme disease.

Nymphal ticks pose a particularly high risk due to their abundance and small size (about the size of a poppy seed), which makes them difficult to spot. In fact, Lyme disease patients are often not even aware of a tick bite before getting sick. Adult female ticks also can transmit the bacteria but because of their larger size (about the size of sesame seed), they are more likely to be noticed and removed from people before transmission of the bacteria can occur.

If you were bitten by a tick, it's important to watch for symptoms of disease that may appear up to 30 days after being bitten. Symptoms can include:

• Body/muscle aches
• Fever
• Headache
• Fatigue or extreme tiredness
• Joint pain
• Rash
• Rashes can look very different depending on the person or type of disease. Some rashes are a spreading, painless red area, while others look like spots that cover certain parts of the body.
• Stiff neck
• Facial paralysis (being unable to move parts of your face)

If you develop any of these symptoms within 30 days of a tick bite, or 30 days after being in areas where ticks are common, see a doctor or healthcare provider right away. Be sure to tell the healthcare provider if you recently had a tick bite or were outside in areas where ticks may be present. Most tick-borne diseases can be successfully treated with antibiotics, especially if treatment is started early.

Lyme disease can be prevented by avoiding tick bites and promptly removing ticks.

Before going outside:

Know where to expect mosquitos and ticks.

• Most mosquito species in the U.S. increase activity from dusk to dawn, which means you're more likely to get bit if you step outside at that time. People who spend time or live near wooded areas, wetlands or shaded places with standing water, a breeding ground for mosquitoes, are at increased risk of bug bites.
• In California, ticks can be found at any time of the year, though they are more abundant in spring and winter.
  • ​For e​xample, see Seasonal Risk of Exposure to Infected Western Blacklegged Ticks in California graphic (PDF).
  • Ticks live in grassy, brushy, or wooded areas, or even on animals. Avoid wooded and brushy areas with high grass and leaf litter and walk in the center of trails.

Dress for protection.

• Wear loose-fitting long clothing.Covering your skin with long-sleeved shirts and long pants can help stop ticks and mosquitoes from biting.
• Wear light-colored clothes to help you spot any ticks that might be crawling on you.

Apply EPA-registered insect repellent. 

• Use Environmental Protection Agency (EPA)-registered insect repellentswith one of the active ingredients listed below. When used as directed, EPA-registered insect repellents are proven safe and effective, even for people who are pregnant and breastfeeding. Always read and follow label instructions when using.
  • DEET, Picaridin, IR3535, Oil of lemon eucalyptus (OLE), Para-menthane-diol (PMD), 2-undecanone

Treat clothes and gear with products containing 0.5% permethrin. 

• Permethrin is an ingredient that can be used to treat boots, clothing, and gear to kill and repel ticks and mosquitoes. It remains protective through several washings.

Tick Tip.

When you go out into areas where ticks live, bring a pair of tweezers or a tick removal device with you to remove any attached ticks.

After coming inside:

 Take a shower soon after being outdoors. 

• Showering within two hours of coming indoors has been shown to reduce your risk of getting Lyme disease and may be effective in reducing the risk of other tickborne diseases. Showering may help wash off unattached ticks and it is a good opportunity to do a tick check.

Check for ticks

• Ticks are tiny! Check your body, your kids, and your pets for ticks after spending time outdoors, even in your own backyard. Use a hand-held or full-length mirror to view all parts of your body and remove any tick you find. Ticks like to hide so be sure to check these parts of your body:
  • Under the arms
  • In and around the hair and ears
  • Inside belly button
  • Back of the knees
  • Between the legs
  • Around the waist
• What to look for: Ticks have a flat, teardrop-shaped body and are usually brown, reddish, or black, and may have gray or white markings. Ticks can be tiny, so look carefully, or ask someone to help you check the areas you can't easily see.
• Continue to check for ticks on your body and in your bedding for 3 days after being outside in areas with ticks.

Check your clothing for ticks

• Tumble dry clothes.Ticks may hitch a ride into your home on clothing. Place clothes in a dryer on high heat for 10 minutes to kill ticks on dry clothing after you come indoors. If the clothes are damp, additional time may be needed. If the clothes require washing first, hot water is recommended. Cold and medium temperature water will not kill ticks.

Tick removal

 If you find a tick crawling on your clothes or skin, brush it off. If you find a tick attached to your skin, remove it right away.

Th​ere are several tick removal devices on the market, but a plain set of fine-tipped tweezers works well.

1. Use clean, fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible.
2. Pull upward with steady, even pressure. Don’t twist or jerk the tick; this can cause the mouth-parts to break off and remain in the skin. If this happens, remove the mouth-parts with tweezers. If you cannot remove the mouth easily with tweezers, leave it alone and let the skin heal.
3. After removing the tick, thoroughly clean the bite area and your hands with rubbing alcohol or soap and water.
4. Never crush a tick with your fingers. Dispose of a live tick by
   • Putting it in alcohol,
   • Placing it in a sealed bag/container,
   • Wrapping it tightly in tape, or
   • Flushing it down the toilet.
5. Wash your hands and the bite area with soap and water. Then apply an antiseptic or antibiotic ointment to the bite area.
6. Dispose of the tick — throw the tick away in the trash, flush it down the toilet, or save it for identification by a public health agency. Never crush a tick with your fingers. 
   • To save a tick for identification, take a picture of the tick (if possible) and then place it in a sealed bag or tape it to a piece of paper using clear tape.
   • Testing ticks removed from a person for the purposes of medical decision-making is not recommendedby the California Department of Public Health.​​

Tick removal techniques that don’t work, such as applying nail polish, burning the tick with a match, or swabbing it with soap or petroleum jelly, should not be used because they delay removal and can also be dangerous. If you find a tick attached to your skin, it’s important to carefully remove it as soon as possible and not wait to “suffocate” the tick or make it detach by burning it. The longer you wait to remove a tick, the more likely that a tick can transmit germs that cause disease.

Erick Burres

Clean Water Team Coordinator

California Water Quality Collaboration Network Facilitator

Safe to Swim Network Co-facilitator

Email: erick.burres@waterboards.ca.gov

Phone: 213 712 6862 mobile

Mailing address:

Erick Burres – Clean Water Team C/O SARWQCB - 3737 Main Street, Suite 500, Riverside, CA 92501