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Warming and Vector-Borne Illnesses

By PAM BERNS
As the world heats up several degrees—and shifting populations flee flood coasts and hot deserts—there will be increases in vector-carrying insects, mosquitoes and ticks caused by longer life cycles and different breeding conditions. Increased rainfall can create stagnant pools of water that attract mosquito-breeding and increase transmission of vector-borne diseases including West Nile, Lyme and Powassan diseases. Wetter springs and warmer winters have affected these populations. The diseases that will continue to propagate here will be fungal, algae, tick-borne and mosquito-borne. Even dengue fever is breeding more freely because of the dying coral reefs and warmer waters.
   
Spread by ticks, the rare Powassan virus has been seen in the U.S., too. The virus affects few victims, but it can cause death within days, following headaches, vomiting, swelling, seizures and permanent neurological symptoms—including memory problems, facial tics and blurred vision. Sometimes Lyme and Powassan symptoms can be confused. But Lyme disease is caused by a bacterium and Powassan is caused by a virus. But their symptoms can appear quite similar. Powassan is assumed to be underreported because the symptoms can appear from the time of the tick bite to the beginning of symptoms a week to a month after contact. And some patients do not exhibit symptoms, but can die suddenly from the Powassan virus. This encephalitis virus is of great concern because there is no treatment.
  
Last year, too, the mosquito-borne West Nile virus returned to the U.S. Four hundred people were infected and 19 of them died.
  
The good news for Midwesterners is that mosquitoes and arachnids like ticks, spiders and mites don’t emerge until it’s above 45 degrees outside. Ticks lay in wait in grasses until a human or animal—such as a dog—brush by. They latch onto their hosts and suck blood—sometimes for days. Ticks are so efficient at spreading disease because they attach by crawling onto the host. They don’t jump or fly. But once they attach to the host, they can crawl all over the body of the host, even the scalp.
  
Most of the ticks humans encounter have hard shells: The Lone Star Ticks, Black-legged “Deer” Ticks, Brown Dog Ticks, American Dog “Wood” Ticks and Winter Ticks. The Lone Star Ticks can transmit Rocky Mountain spotted fever, but rarely Lyme disease. The ticks that usually feed on humans in our area are the Deer Ticks and American Dog Ticks. The Lone Star Ticks can also transmit tularemia and ehrlichiosis to humans, usually between April and July in Illinois.
  
The Deer Tick (Black-legged Tick) and American Dog Ticks can feed on numerous hosts, including human in different stages of their development. In one stage, the larvae feed on small mammals such as mice. The following spring—at the larvae and nymph stages—they feed on larger warm-blooded animals and birds. The following fall, they feed mostly on deer, dogs, raccoons and humans. These ticks are most active in Illinois and surrounding states in the spring and fall. The ticks only reach about an eighth of an inch in length. However, after the ticks feed, they can reach the size of a small cherry.
   
The Deer Tick can transmit Lyme disease, babesiosis and ehrlichiosis to humans. These ticks are usually found along trails and can be seen in many Illinois counties.
   
Of ticks submitted to the state, around 75 percent have been identified as the American Dog Tick or Lone Star Tick.
  
According to the Chicago Tribune, Mark Pfister, Director of Population Health Services for Lake County, the pathogen carried by the ticks is now found in 40 percent of the ticks it has tested.
   
The U.S. Centers for Disease Control and Prevention have been tracking Lyme disease, which is frequently misdiagnosed as arthritis or multiple sclerosis. One of the signs of Lyme disease on a patient is the famous bull’s eye target rash around the bite. They estimate that there are probably more than 300,000 cases of Lyme disease in the U.S. every year but that only 30,000 cases are reported.
   
But the symptoms can be debilitating. Sometimes symptoms include severe headaches, deafness and weakness, even Bell’s palsy—which paralyzes the face. Other symptoms echo illnesses like the flu—with headaches, fatigue and fever. But some patients suffer with symptoms for years without treatment, which usually consists of antibiotics which are often successful if the illness is diagnosed early.
  
According to the New York Times, the Black-legged Ticks found in the Northeast and Midwest can also harbor other even more serious diseases like the aforementioned Powassan virus, anaplasmosis, babesiosis and Borrelia miyamotoi. They write that a patient can be struck with more than one of these illnesses at the same time. The Black-legged Ticks transmit Lyme disease’s bacteria—spirochetes—from rodents to deer to humans. Powassans’s tick carriers favor skunks, rodents, deer and woodchucks.
  
To avoid disease, wear long-sleeved shirts, pants, boots and hats when hiking. Check yourself every few hours. If you see a tick on your body, use masking or duct tape to remove a tick, or grasp it firmly with tweezers. Wash the tick bite area and your hands thoroughly. If you feel ill and have a fever, contact your physician or call 217-782-2016.
    
Researchers are looking into killing the ticks with plant extracts and fungi while trying to avoid injuring wildlife. Other researchers are also looking into vaccinating mice. According to the World Health Organization, “Mosquito species such as Anopheles gambiae comples, A. funestus, A. darlingi, Culex quinque fasciatus and Aedes aegypti are responsible for transmission of most vector-borne diseases and are sensitive to temperature changes as immature stages in the aquatic environment and as adults.”
  
Research into these tick-borne illnesses must be a priority.
   
According to David Leiby of the Red Cross, Babesia microtia, a coinfection of Lyme disease, has transmitted between 70 and 100 cases via transfusion resulting in 12 fatalities over the past 3 decades. It is a malaria-like parasite or “piroplasm.” However a method of screening blood has not been adopted.

Published: April 25, 2014
Issue: Spring 2014 Issue