Latest Infectious Disease News
Fall is here, but don't think you can walk through the woods safe from ticks -- some species are active all year long. And you have extra reason to watch for ticks in 2019. Tick experts anticipate a rise in tick-borne infections like Lyme disease and Rocky Mountain spotted fever, continuing a decades-long trend.
Recent news reports also show rarer tick-related diseases such as Powassan encephalitis disease in Massachusetts and New York, and Heartland virus in Illinois.
Of all the backyard pests, ticks cause the most disease by far in the United States. Every year, more than 95 percent of the diseases caused by pests have come from a tick bite, according to a public health review published last year.
Since the 1990s, confirmed reports of Lyme infection have quadrupled. Other tick-borne illnesses have risen even more. Diseases like babeisosis, anaplasmosis, and red meat allergy (also caused by ticks) are all being reported more widely.
When they bite a person, a tick can spread disease quickly, according to Charles Patrick Davis, MD, PhD.
"Disease transmission can occur in less than a minute with soft ticks," Dr. Davis says. "The bite of some of these soft ticks produces intensely painful reactions."
In some regions around the United States, more bites from disease-spreading ticks are being reported, and in some areas the rate of diseases caused by ticks is also ramping up each year. In some regions where no ticks had been found in the past, reports are now appearing of tick bites and related diseases.
Where Tick Habitats Are Expanding
American Dog Tick
This tick is the main carrier of Rocky Mountain spotted fever, and it can spread lesser-known diseases too. It is known as an "ambush tick" because it tends to lie in ambush along woodland trails and roadsides.
Dog ticks can be found across the Eastern United States from Florida to the northern border. They can also be found in California and southern Oregon. As winter temperatures increase further north, their habitat is widening into northern climates, including Canada.
Lone Star Tick
The Lone Star tick is known for aggression. Rather than wait for a blood meal, Lone Star ticks pursue their hosts by following their scent. They can transmit Heartland virus, Ricketsettia bacteria, and other diseases.
Once limited to south of the Ohio river valley, this tick species is also spreading further north year after year. New populations have been reported in Michigan, Pennsylvania, and most New England counties. The tick has also migrated west to Nebraska and South Dakota in recent years.
Gulf Coast Tick
This tick also transmits Rickettsia infection, as well as the dog pathogen Hapatozoon americanum.
Gulf Coast ticks can be found as far south as Central America. They were once limited to states along the Gulf Coast and South Atlantic, but that picture is changing. Today this tick has migrated into several new states, including Arkansas, Oklahoma, Kansas, and Tennessee. It has even been found in southern Arizona.
This is the tick that spreads Lyme, along with a wider variety of diseases than any other North American tick. And winter weather barely slows it down. Adults remain active as long as the temperature isn't freezing, according to the Rhode Island Tick Encounter Resource Center.
This tick has spread as it migrates with its primary host, the white-tailed deer. As these deer have been reintroduced into reforested habitats around the Eastern U.S., the blacklegged tick has spread to these areas too. Recently this tick has encroached northwest into Quebec, Canada, as well as west into Iowa. Indeed, their populations seem to be thriving more and more in nearly all regions east of the Mississippi river.
Why Are More Ticks Biting People?
Scientists have offered several explanations for the rise in harmful tick bites. In some cases people have built neighborhoods deeper into forested areas, which puts people in closer proximity to these pests. In other cases, host animals have been increasing their numbers and territorial ranges. Many believe that climate change has inspired these increases, as ticks thrive in warmer climates.
What Are Tick Bite Symptoms and Signs?
Unfortunately for the purpose of detection, the tick bite is usually painless and remains that way even after the tick stops the blood meal and falls off of the skin. Later, the bite site may develop:
- redness or red spot
- rarely, localized intense pain like in the joints (some soft tick bites) in some individuals
Although most tick bites do not transmit pathogens, some do. It is not possible to determine if a tick is carrying pathogens visually. The following is a list of all of the major tick-borne diseases, the usual tick vector(s), and the pathogen(s) the tick transmits that may occur in the United States.
- Tularemia -- Dermacentor variabilis (American dog tick; several species are also known as a wood tick) (hard tick) and Amblyomma americanum or lone star tick (hard tick) -- vectors for Francisella tularensis bacteria
- Anaplasmosis (human granulocytic anaplasmosis or HGA) -- Ixodes species (hard tick) -- vectors for Anaplasma phagocytophilum bacteria
- Colorado tick fever -- Dermacentor andersoni (hard tick) -- vectors for Coltivirus, a RNA virus
- Powassan encephalitis -- Ixodes species and Dermacentor andersoni (both hard ticks) -- vectors for Powassan encephalitis virus, an RNA arbovirus
- Babesiosis -- Ixodes species (hard ticks) -- vectors for Babesia, a protozoan
- Ehrlichiosis -- Amblyomma americanum or lone star ticks (hard ticks) -- vectors for Ehrlichia chaffeensis and Ehrlichia ewingii bacterial species
- Rocky Mountain spotted fever -- Dermacentor variabilis (American dog tick) and Rocky Mountain wood tick (Dermacentor andersoni) (hard tick) are the primary vectors and occasionally the brown dog tick (Rhipicephalus sanguineus); Amblyomma cajennense (hard tick) is the vector in countries south of the U.S. -- vectors for Rickettsia bacteria
- Lyme disease -- Ixodes species including deer ticks or also known as black-legged ticks (hard ticks) -- vectors for Borrelia species of bacteria
- Heartland virus -- a viral disease discovered in 2012 transmitted by Amblyomma americanum or lone star tick
- Tick-borne relapsing fever -- Ornithodoros moubata or African tick; (soft tick) -- vectors for Borrelia species of bacteria
- Q fever -- Rhipicephalus sanguineus, Dermacentor andersoni, and Amblyomma americanum (all three are hard ticks) -- vectors for Coxiella burnetii, a bacterium
- Southern tick-associated rash illness (STARI) -- Amblyomma americanum or lone star tick (hard tick) -- infectious agent not yet identified according to U.S. Centers for Disease Control and Prevention (CDC)