Why Mosquitoes Are A Serious Threat
Mosquitoes can cause sickness and death through the diseases they can carry. The information provided below describes which mosquito-borne (carried) diseases threaten us here in Louisiana both currently and potentially. Apart from the ability to carry diseases, mosquitoes also cause major nuisance problems for rural homeowners and can ruin recreational activities such as hunting and outdoor sports. In extreme situations, high levels of flood-water mosquito species can pose a life-threatening situation for livestock and wild animals as well.
The economic impact of the problems that mosquitoes cause is staggering for such a tiny little insect. In Africa alone where mosquito control efforts are severely lacking businesses note that work absences related to mosquito-borne diseases cost them $12 billion a year in lost productivity. Back here at home, excluding the cost of mosquito control efforts by governmental agencies, the cost of WNV related health care is estimated to be over 56 million dollars per year in the U.S. alone.
Mosquito-Borne Disease Quick Facts
- According to the World Health Organization, mosquitoes infect between 330-600 million people a year with Malaria and Dengue, just two of the life-threatening diseases that mosquitoes can carry.
- According to the World Health Organization, over 400,000 deaths occurred from malaria in 2019. The Centers for Disease Control reports that 22,000 people die from Dengue-related deaths every year.
- According to the Centers for Disease Control in the United States alone since 2001 over 50,000 confirmed cases of West Nile Virus infections in humans have occurred. Of those cases, over 2,300 have resulted in death.
- According to one study (CDC Emerging Infectious Diseases Journal 2009), three million unconfirmed human West Nile Virus infections occurred between 1999 and 2008 alone.
- Over 1 million pets in the U.S. alone are estimated to be infected with heartworms. The infection rate for dogs over 2 years old is thought to be over 80% in South Louisiana.
- Mosquitoes kill more people (over 700,000 per year) than any other animal on the planet by far. The closest in fact would be snakes, they kill around 50,000 people per year.
For More Information
To obtain more information about mosquitoes and the diseases they can carry check out these informative links.
- The Louisiana Mosquito Control Association
- The American Mosquito Control Association
- The Centers For Disease Control
- The World Health Organization
Top Mosquito-Borne Disease Threats in The U.S.
Eastern Equine Encephalitis
- Abbreviation: Eastern Equine Encephalitis (EEE)
- Fatality Rate: 30%
- Primary Mosquito Vector: Culiseta Melanura in birds / Culex Quinquefasciatus in man
- Potential Mosquito Vectors: Cs. Inornata, Aedes Albopictus, Aedes Sollicitans, Aedes Vexans, Aedes Infirmatus, Aedes Atlanticus, and Coquillettidia Perturbans
- Threat Status: Intermittent
Deadliest Mosquito-Borne Disease in The U.S.
Eastern Equine Encephalitis much like West Nile Virus and St. Louis Encephalitis is a viral infection maintained in the wild by a bird to mosquito to bird cycle. Horses are involved with humans as dead-end hosts meaning they cannot transmit the disease between themselves. Of the many mosquito-borne diseases, EEE is the deadliest mosquito-borne disease to occur in the United States with a 30% fatality rate for those infected. Half of those who survive the infection are stricken with various degrees of mental disability and paralysis. People younger than 15 and those older than 50 are the most prone to infection although EEE can affect persons of any age.
A major outbreak of EEE struck Louisiana in 1947 when the virus caused disease in over 15,000 horses and 15 human cases resulting in 7 people dead. Since that outbreak understanding of the transmission cycle in the wild and the creation of a vaccine for horses has resulted in much fewer infections for horses and humans. Although incidents of disease in humans have been low in recent times EEE still remains a deadly mosquito-borne disease for both horses and man.
St. Louis Encephalitis
- Abbreviation: St. Louis Encephalitis (SLE)
- Fatality rate: 3 to 30%
- Primary Mosquito Vector: Culex Quinquefasciatus (Southern House Mosquito)
- Potential Mosquito Vectors: Culex Salinarius
- Threat Status: Intermittent
Saint Louis Encephalitis is another arboviral disease found commonly in the United States. Much like West Nile Virus, St. Louis Encephalitis is maintained in the bird population by mosquitoes with humans being an accidental or dead-end host. As with West Nile Virus, humans are infected when a mosquito that has fed on an infected bird also feeds on a human host. St. Louis Encephalitis can affect persons of any age however the effects are usually far more severe in those above 60 years old.
Most Severe Epidemic
The most severe St. Louis Encephalitis epidemic in recent times was the one that rolled through the Mississippi River Valley in 1975. A total of 1,941 human cases were recorded 95 of which resulted in death. The most severe outbreak of SLE in Louisiana to date occurred in 2001. The outbreak which consisted of 70 cases happened in Ouachita parish and was centered in the city of Monroe. Since then, human cases have been sporadic, averaging about 128 in the U.S. per year. Since mosquito surveillance began in earnest in 2004, WBR Parish has had several recorded SLE positive mosquito samples, but no confirmed human cases to date.
West Nile Virus
- Abbreviation: West Nile Virus (WNV)
- Fatality Rate: Less than 1%
- Potential Mosquito Vectors: Aedes Vexans, Aedes Aegypti, Aedes Albopictus, Aedes Triseriatus, Anopheles Quadrimaculatus, and Culex Salinarius.
- Primary Mosquito Vector: Culex Quinquefasciatus (Southern House Mosquito)
- Threat Status: Current
West Nile Virus first arrived in the United States in 1999 in the New York area, since then it has spread rapidly covering virtually every part of the country. WNV most often starts out as a bird disease, it is then maintained and passed around from bird to bird in the wild by mosquitoes. Humans are infected when a mosquito that has fed on an infected bird then turns around and feeds on a human. WNV is not transmitted from human to human but rather from bird to mosquito to man, with humans being an accidental or dead-end host.
People over the age of 75 are at the greatest risk of succumbing to the severe form of the disease known as neuroinvasive WNV. Human cases have occurred in 75% of Louisiana Parishes. Most WNV human cases are concentrated in major urban areas.
West Nile Fever
Most healthy persons who contract the disease will experience the less severe form of the disease known as West Nile Fever and make a full recovery. Less than 1% will experience the more severe form of the disease known as neuroinvasive WNV. Nueroinvasive WNV can cause symptoms such as high fever, convulsions, tremors, vision loss, paralysis, and muscle weakness. Those who recover are often left with permanent neurological effects. Around 10% of neuroinvasive cases result in death. Since 1999 over 51,000 confirmed WNV human infections have occurred in the U.S, resulting in 2,390 deaths. Louisiana has recorded over 2,900 confirmed human WNV infections since 1999, resulting in 76 deaths. One study (CDC Journal of Emerging Infectious Diseases October 2009), estimates that over 3 million people were infected with WNV between 1999 and 2008 alone.
Since surveillance began in earnest in 2004 West Baton Rouge Mosquito Control has submitted over 32,000 mosquito samples to LSU Disease Diagnostic Lab for testing. Over 2,700 of those have tested positive for WNV with several testing positive for St.Louis Encephalitis as well. West Nile Virus is likely to be a long-term problem in Louisiana and is now officially considered endemic (native) to this state.
- Fatality Rate: rare / can cause devastating birth defects
- Potential Mosquito Vectors: Aedes Aegypti, Aedes Albopictus
- Primary Mosquito Vector: Aedes Aegypti
- Threat Status: unknown
In 2015 Brazil and other areas in South America experienced a large outbreak (over 7,000) of Zika human cases. Outbreaks soon followed in other parts of the world including Africa, Asia, the Pacific, and in Miami, Florida during 2016. To date, over 86 countries have reported cases of mosquito-based Zika infections.
What Makes Zika Different
What makes Zika Virus so different and dangerous is that unlike many other mosquito-borne diseases, humans serve as the primary host for the disease. The disease is then spread from person to person via mosquito bite. Also, unlike many other mosquito-borne diseases, Zika can be spread by sexual contact, blood transfusion, and organ transplant. Zika Virus can also be transferred from the mother to fetus during pregnancy.
The main concern with Zika Virus is the threat it poses to an unborn fetus during pregnancy. A Zika infection passed from the mother to fetus can result in the baby being born with Microcephaly (smaller than normal head size) and other defects that collectively are known as Zika congenital syndrome. Between 2015-2016 over 3,000 cases of Microcephaly (due to Zika Virus) were reported in infants, mostly in South America. The Centers for Disease Control estimates that the cost of healthcare over a lifetime for a child born with microcephaly is more than 10 million dollars.
Is Zika a Threat to The U.S?
When and if the United States or Louisiana for that matter experiences widespread problems with Zika Virus remains to be seen. If Louisiana does experience widespread problems with Zika Virus more than likely the mosquito species to blame will be Aedes Aegypti or Aedes Albopictus. These species breed entirely around the home, so it will become more important than ever to empty those containers and rid your yard of standing water. For more information on these container breeding mosquitoes and their breeding habits check out our Important Mosquito Species Page.
The situation with Zika Virus is one that is changing constantly, so for answers to your questions about Zika Virus you can call our office at 225-214-5900 or you can visit the Center for Disease Control information page on the current status of Zika Virus in the United States. You can also check out our Facebook page where we post updated information constantly on Zika Virus and other mosquito-borne disease threats.
- Local infection rate: in Southern Louisiana over 80% of dogs over 2 years old
- National infection rate: more than 1 million pets are thought to be infected in the U.S.
- Potential mosquito vectors: Culex Quinquefasciatus, Aedes Albopictus, Aedes Vexans
- Threat status: constant
Heartworms and preventatives
If you are the owner of a dog, cat, or ferret, listen up! A heartworm infection can be a potentially life-threatening problem for your pet and it only takes one bite from an infected mosquito for the process to begin. A heartworm infection causes not only a serious medical condition for your pet, but it can be spread by a mosquito bite from your pet to other animals.
Louisiana is home to several species of mosquito that are capable of transmitting heartworm. In fact, Louisiana ranks second in the nation for the highest incidence of heartworm infections. The top 5 states for heartworm infection are all located in the Southern portion of the United States.
The good news is that heartworm infections are easily preventable. Make sure your animal is under the care of a veterinarian and follow the recommended guidelines for heartworm testing and preventative application. For more information regarding heartworms and what you can do to prevent them, you can visit the American Heartworm Society website here.