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EWG’s 2018 Guide to Bug Repellents
July 17, 2018

EWG’s 2018 Guide to Bug Repellents : Bug-Borne Diseases

Mosquitoes

The number one mosquito-borne disease threat in the U.S. is West Nile virus. Travelers to tropical regions and some other places could encounter Zika, malaria, dengue fever, yellow fever and a few other diseases.

The most common diseases carried by mosquitoes are listed beow.

Mosquito Genus

Diseases

Aedes

Dengue fever, Rift Valley fever, yellow fever, chikungunya, Zika virus, lymphatic filariasis

Anopheles

Malaria, lymphatic filariasis

Culex

West Nile fever, Japanese encephalitis, lymphatic filariasis

Source: World Health Organization,1 2017

West Nile virus struck more than 2,000 Americans last year.2 Two-thirds of those cases were complicated with a neuro-invasive disease such as meningitis, encephalitis or acute flaccid paralysis, according to the Centers for Disease Control and Prevention.3 Symptoms can include high fever, headache, stupor, tremors, convulsions and neurological damage. 

Between 1999 and 2008, 64 different mosquito species tested positive for West Nile virus.

According to the CDC, infections from mosquitoes carrying West Nile virus occur primarily in the summer months, peaking in August. West Nile cases have been found in almost every state in the nation, with the highest 2017 numbers reported in Arizona, Texas, California and Illinois.4

Malaria can cause fever, chills, headache, vomiting, diarrhea and, in severe cases, organ failure, coma and death. In 2016, 91 countries and areas had ongoing malaria transmission, and nearly half of the world's population was at risk from malaria, according to the World Health Organization.5

Some 30 to 40 of the 400 different species within the Anopheles genus transmit malaria. These species are widespread throughout the world.

What tests tell us – and what they don’t

Repellents are not tested against all mosquito species. The most common mosquito used in tests is the Aedes aegypti because it is very sensitive to repellents and easy to cultivate in laboratories. Other Aedes mosquito species require higher doses and more frequent reapplication of repellents.6

One repellent may not always protect a person from all the different mosquito species, nor from other pests. 

Ticks

Diseases carried by ticks are rare, but can be severe. EWG recommends prudent tick prevention methods to anyone who spends time in tick-infested areas.

Eight tick species in the U.S. may carry disease.

Tick

Disease(s)

Symptoms

Blacklegged tick, also known as deer tick

Anaplasmosis
Babesiosis
Lyme disease
Ehrlichiosis
Powassan virus disease

Anaplasmosis: fever, headache, chills and muscle aches
Babesiosis: varies from none to flu-like and life-threatening
Lyme disease: bull’s-eye rash, fatigue, chills, fever, headache, aches, swollen lymph nodes
Ehrlichiosis: fever, headache, chills, malaise, muscle pain, nausea/vomiting/diarrhea, confusion, red eye, rash
Powassan virus: fever, headache, vomiting and generalized weakness. Usually progresses to meningoencephalitis.

Borrelia miyamotoi disease: fever, fatigue, chills, severe headache, muscle aches, joint pain

Western blacklegged tick

Anaplasmosis
Borrelia miyamotoi disease
Lyme disease

American dog tick

Rocky Mountain spotted fever

Tularemia

Rocky Mountain spotted fever: fever, headache, vomiting, muscle pain and, in some cases, death
Tularemia: fever, chills, headache, cough, sore throat, abdominal pain, vomiting and diarrhea, fatigue

Brown dog tick

Rocky Mountain spotted fever

Gulf Coast tick

Rickettsiosis

Rickettsiosis: fever, scabs, rash

Lone star tick

Ehrlichiosis
Tularemia
Heartland virus disease
Bourbon virus disease
Southern tick-associated rash illness (STARI)

Heartland virus: fever, fatigue, decreased appetite, headache, joint and/or muscle pain, nausea, diarrhea
Bourbon virus: fever, tiredness, rash, headache, body aches, nausea, vomiting
STARI: red bull’s-eye rash, fatigue, headache, fever, muscle pains

Rocky Mountain wood tick

Rocky Mountain spotted fever
Colorado tick fever
Tularemia

Rocky Mountain spotted fever: fever, headache, vomiting, muscle pain and, in some cases, death
Tulameria: Skin ulcer with regional lymph node swelling
Colorado tick fever: fever, chills, headache, muscle pain, lethargy

Groundhog Tick

Powassan virus disease

 

Source: CDC,7 2014

Lyme disease, carried by the blacklegged tick and Western blacklegged tick, is the most prevalent tick-borne disease in the U.S., with 26,203 known and 10,226 probable cases reported in 2016, the latest year for which data are available.8 The actual numbers are likely much higher, according to a CDC analysis of clinician data, which provided an estimate of 329,000 cases annually.9

Most cases occur from Virginia to Maine and in the upper Midwest – mostly Wisconsin and Minnesota.

Adult blacklegged ticks are about the size of a sesame seed. Most Lyme disease is transmitted via bites from immature nymphs that feed during the spring and summer. You are most likely to contract tick-borne Lyme disease between mid-April and August.

The lone star tick, found in the eastern half of the U.S., carries Southern tick-associated rash illness, an infectious disease similar to Lyme disease.

Rocky Mountain spotted fever can cause fever, headache, vomiting, muscle pain and, in some cases, death. It can be transmitted to humans by bites from the American dog tick, Rocky Mountain wood tick and brown dog tick. The disease has been reported throughout the lower 48 states, with most cases occurring in North Carolina, Oklahoma, Arkansas, Tennessee and Missouri. The incidence rate has increased over the past 20 years to more than 3,000 U.S. cases annually.10 But the fatality rate has greatly decreased over the past 50 years from 5 to 10 percent to less than 0.5 percent.11


References:

1 Vector-Borne Diseases: Mosquitoes. World Health Organization, 2017. Available at www.who.int/en/news-room/fact-sheets/detail/vector-borne-diseases

2 Preliminary Maps & Data for 2017. Centers for Disease Control and Prevention, 2018. Available at www.cdc.gov/westnile/statsmaps/preliminarymapsdata2017/index.html

3 Preliminary Maps & Data for 2017. Centers for Disease Control and Prevention, 2018. Available at www.cdc.gov/westnile/statsmaps/preliminarymapsdata2017/index.html

4 West Nile Virus Disease Cases by State. Centers for Disease Control and Prevention, 2018. Available at www.cdc.gov/westnile/statsmaps/preliminarymapsdata2017/disease-cases-state.html

5 Malaria: Key Facts. World Health Organization, 2018. Available at www.who.int/news-room/fact-sheets/detail/malaria

6 A. Badolo et al., Evaluation of the Sensitivity of Aedes Aegypti and Anopheles Gambiae Complex Mosquitoes to Two Insect Repellents: DEET and KBR 3023. Tropical Medicine and International Health, March 2004, 9(3):330-334. Available at www.ncbi.nlm.nih.gov/pubmed/14996361

7 Tickborne Diseases of the United States. Centers for Disease Control and Prevention, 2014. Available at www.cdc.gov/ticks/tickbornediseases/tickID.html

8 Lyme Disease Data Tables. Centers for Disease Control and Prevention, 2017. Available at www.cdc.gov/lyme/stats/tables.html

9 Christina A. Nelson et al., Incidence of Clinician-Diagnosed Lyme Disease, United States, 2005-2010. Emerging Infectious Diseases, 2015, 21(9). Available at wwwnc.cdc.gov/eid/article/21/9/15-0417_article

10 Rocky Mountain Spotted Fever: Statistics and Epidemiology. Centers for Disease Control and Prevention, 2017. Available at www.cdc.gov/rmsf/stats/index.html

11 Rocky Mountain Spotted Fever: Statistics and Epidemiology. Centers for Disease Control and Prevention, 2017. Available at www.cdc.gov/rmsf/stats/index.html