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Mosquitoes! Just the mention of them brings most of us back to the time when we had so many little red welts we were contorting ourselves to get them all scratched. In the U.S., the fact that mosquitoes can be disease vectors is not top of mind for most of the public. That’s because mosquito-borne diseases like malaria have been all but eradicated in the U.S. (although we still get about 1,500 cases in the U.S. each year, most of them travel-related, and only about five fatalities a year, according to the Centers for Disease Control and Prevention). Worldwide, though, malaria still kills an estimated 750,000 to 1 million people per year, making the humble mosquito the most dangerous insect in the world.

Considering how much growth the pest control industry is seeing in the mosquito control market (according to the 2018 PCT State of the Mosquito Market Report, 22% of survey respondents reported a 50% or more increase in service requests from 2016 to 2017), many PCOs are focusing more on this segment. It’s for this reason PCT hosted the recent Mosquito Control Virtual Conference, which included a presentation from Dr. Phil Koehler, endowed professor of urban entomology at the University of Florida.

SELL ON QUALITY. Koehler began by recounting conversations he’s had with regulators who shared concerns that PMPs might sell their mosquito services out of fear, rather than on good quality. Some PMPs told him they don’t want the liability that comes with dealing with mosquitoes. Koehler emphasized that if PMPs sell the service as mosquito control rather than disease control there should be no worries about liability.

PMPs, at any rate, do not need to sell the disease control aspect of this service. That work already has been done, he said, noting that the media have provided the industry with $73 million-worth of free advertising. Mosquito-related diseases have been on the public’s mind since the media began focusing on diseases such as West Nile virus and Zika, especially in Texas and Florida, which seem to have the lion’s share of local transmissions. The main points of Koehler’s webinar presentation centered around 1) diseases and their vectors; and 2) how to best treat for mosquitoes.

The St. Louis variety of encephalitis is vectored by Culex pipiens and Culex quinquefasciatus, or the northern and southern house mosquito, which interbreed with each other and are night feeders. (In Florida, the vector is sometimes Culex nigripalpus.) St. Louis encephalitis has occurred in all states. The western equine variety is found in the western 2/3 of states. Eastern equine encephalitis occurs in the eastern 1/3 of states, generally, and La Crosse (vectored by the Aedes triseriatus, the eastern treehole mosquito) transmits the pathogen that causes a disease called California encephalitis. Ten percent of people with this virus will develop behavioral problems and there is a one percent mortality rate, CDC reported. From 2007 through 2016, an average of seven cases of St. Louis encephalitis were reported annually, CDC reported. There are an average of 63 La Crosse encephalitis cases reported per year, according to CDC.

The western variety has caused fewer than 1,000 cases since 1964. West Nile virus was first discovered in Uganda in 1937 and was introduced to the U.S. in New York in 1999. West Nile virus cases in this country tend to be mild, with 80 percent of infected persons exhibiting no symptoms, although Koehler relayed that he had seen an outbreak in Greece a few years ago that was the second largest West Nile virus epidemic in Europe. It is spread by Culex among birds, and then to humans. It will produce encephalitis in only one percent of infections. All states except Hawaii and Alaska have reported West Nile virus cases. In addition, dog heartworms can be transmitted through the bite of an infected mosquito.

The vector of dengue is the Aedes aegypti mosquito, while the primary vector of chikungunya is Aedes albopictus, also called the Asian tiger mosquito. Aedes aegypti mosquitoes have a brown tint and a “lyre” shape on the back of the thorax, while Aedes albopictus has a black head and thorax with a white stripe. Both Aedes aegypti and Aedes albopictus travel no further than a ½ mile. As adults, Aedes aegypti has a more southern U.S. distribution than Aedes albopictus, which handles cold weather better. Both lay their eggs in old tires, pots, birdbaths, rain barrels, sunken parts of trees, septic tanks or any type of exterior container where water can stagnate.

Dengue and chikungunya also differ when it comes to symptomology. Individuals who have contracted dengue experience muscle pain on their back, arms and legs and joint pain in their knees and shoulders; those with chikungunya have joint pain in their hands and feet. Dengue typically produces rashes on people’s faces and limbs, while chikungunya can create rashes on areas such as trunks, limbs, face, palms and feet.

Though yellow fever is rare in America, it has had a rapid growth worldwide and may be the next introduction in the U.S. in travel-related cases.

DISEASES. There are a number of high-profile mosquito-borne diseases in the U.S. and throughout the world, including chikungunya, dengue, yellow fever, West Nile virus and encephalitis of the St. Louis, Eastern Equine, La Crosse and Western equine varieties. All of these have occurred in the United States but sometimes only in a certain region.

A NEW THREAT EMERGES. While the aforementioned viruses have been on the public’s mind for some time, the real headline-grabbing virus in recent years has been Zika. In May 2015, the first local transmission of Zika virus in the Americas was reported in Brazil. The disease has mutated and changed in its form as it spread around the world.

Zika is transmitted to people primarily through the bite of an infected Aedes mosquito (usually Aedes aegypti). These are container-breeding mosquitoes, meaning they like to utilize containers such as rain barrels, kids’ swimming pools, etc.

In the U.S. the virus is transmitted between humans and urban mosquitoes, primarily Aedes aegypti. Other forms of transmission include sexual contact and through blood transfusions; of particular concern is intra-birth transfusion, in which a mother transmits the disease to an unborn baby.

Zika symptoms are typically mild and these might include severe headaches, bloodshot eyes, diarrhea, muscle aches, fever and skin rashes. However, the vast majority of people don’t have those symptoms. Zika is of greatest concern in pregnant women; the virus can cause fetuses to have a birth defect of the brain called microcephaly (see related article featured above).

In rare cases, Zika can cause Guillain-Barré syndrome, wherein the immune system attacks the nervous system.

While Zika is not grabbing the headlines that it once was, that does not mean it is going away. So far in 2018, there have been 430 symptomatic Zika virus disease cases that breaks down as follows:

  • 417 cases in travelers returning from affected areas
  • 5 cases acquired through presumed local mosquito-borne transmission in Florida (2) and Texas (3)
  • 8 cases acquired through other routes; sexual transmission (7) and laboratory transmission (1)

“Zika virus did not disappear,” Koehler noted. “It is going to stay with us one way or another because it is something that is occurring in other parts of the world and travelers are continuing to bring it back.”

TREATMENT OPTIONS. So how should PMPs deal with mosquitoes? First, as previously noted, they should offer mosquito control and not disease control. “Your purpose is to reduce the number of disease-vectors out there,” Koehler said.

Koehler prescribed these activities: educating technicians and other staff members; providing educational resources to customers (e.g., CDC fact sheets); equipment training on such items as mist blowers; monitoring; and offering a free inspection along with their regular service.

“I’ve often told [PMPs] that any time a customer calls in for a service you should offer them a free mosquito inspection. That can be an add-on to possibly expanding your service offerings, to visiting customers or even to new customers by saying, ‘We will do a free inspection for mosquitoes on your property.’ If you find [mosquitoes] then that is going to determine a need for treatment.”

In terms of mosquito treatments, Koehler recommends an integrated program that involves the use of ultra-low volume (ULV) space sprays; mist blower adulticide residual spraying; larvicide treatments; and applying a residual spray under eaves.

“There are some advantages and disadvantages to residual sprays and space sprays,” Koehler noted. “Basically, it’s very easy to apply a residual spray that’s going to provide long-term control as opposed to a space spray and that’s going to provide immediate knock down, but very short-term control.”

Koehler said his team at the University of Florida has found that spraying with a combination larvicide and adulticide has proven effective for mosquito control.

OPPORTUNITIES ABOUND. Koehler encouraged PMPs to “deal with change” when it comes to mosquito management and not let opportunities pass them by. “You need to do everything you can to make sure everyone is on board with responsible mosquito control — not disease control,” he said.

In addition to educating your team about mosquito biology, behavior and control methods, distribute educational brochures and perhaps push yourself out of a comfort zone and provide a free mosquito inspection.

“In the words of Nelson Mandela, you can ‘Change the world and make it a better place.’ It’s in your hands to make a difference and mosquitoes are a big problem for your customers. But all problems are opportunities in disguise.And these are opportunities for you and for your company.”

The author is a service professional at Greenway Pest Control, Albuquerque, N.M.