More ticks and more tick disease

Tick-borne disease and the number of ticks are on the rise globally, especially in the United States, thanks to a milder winter in many regions. Ticks are arachnids, and live on a variety of mammalian host species. Ticks bite, attach and live on their mammalian hosts as they feed on their blood. During their attachment, however, ticks may transmit disease through their saliva if they are infected with a disease-causing organism. Recently, it has been found that ticks may also cause an allergy to red meat.

Lyme disease on the rise

Probably the most well-known tick-borne disease is Lyme disease, also known as Lyme borreliosis, as it is caused by Borrelia bacteria, a spirochete with flagella. In the United States, the disease is caused by either Borrelia burgdorferi or Borrelia mayonii, whereas in Asia and Europe, Borrelia afzelii and Borrelia garinii are additional causes of Lyme disease. The genus of tick that carries these bacteria is Ixodes.

Nearly 75% of individuals who contract Lyme disease will have a recognizable “bullseye” rash at the site where the tick had attached. Symptoms include rash, muscle pain and weakness, neurological problems such as facial palsy, meningitis and joint pain. If untreated, Lyme can become a chronic condition with a variety of potential symptoms from arthritis and weakness to cognitive difficulties and palsy.

More than 350,000 people are diagnosed with Lyme disease annually from sixty countries. The primary treatment is an antibiotic regimen. Transmission usually occurs from mammals to humans via deer, rodents and pets. The best way to prevent Lyme infection is to check for ticks after spending time outdoors in infested regions, as the tick must be attached 36-48 hours before enough bacteria enter the body to result in Lyme infection.

Although ticks can acquire the Lyme bacteria from a variety of mammalian sources, the vast majority are infected from white-footed mice. With a recent increase in population of this mouse species, the number of Lyme cases is expected to continue to rise.

And it’s not just Lyme

Powassan (POW) virus is another tick-borne disease. The virus is an RNA virus of the Flavivirus family, related to West Nile (which is spread by mosquitoes). In North America, rodents are the main reservoir of the virus; these include woodchucks and the tick Ixodes cookei, squirrels and the tick Ixodes marxi, and white-footed mice and the tick Ixodes scapularis. According to the Centers for Disease Control (CDC), I. scapularis is more likely to bite humans than the other tick species, so it is the main vector of POW infection.

In recent years, incidence in POW virus has increased in the United States, Canada and Russia where the disease is primarily reported. Although many individuals infected with POW virus do not exhibit any symptoms, effects of the virus can be severe, including encephalitis and meningitis. More common, however, are symptoms such as fever, headache, seizures, vomiting, weakness and speech difficulties. Half of those infected will have long-term effects of the disease, including memory loss and muscle wasting.

And it’s not just disease

Clinicians have noticed over the past decade that the incidence of meat allergies has increased. They identified a link between individuals with meat allergy and patients with Rocky Mountain spotted fever, another tick-borne disease spread by the lone star tick carrying the bacteria Rickettsia rickettsii. It turns out, the lone start tick is triggering an allergy to galactose-alpha-1,3-galactose (alpha-gal), a sugar molecule present in red meat.

Researchers found that a bite from a lone star tick causes nearly a 20-fold increase in the level of alpha-gal antibodies in humans, resulting in the red meat allergy. However, the agent in the tick saliva that actually causes the increase in alpha-gal antibodies has yet to be identified. On top of all this, the lone star tick, which has traditionally stuck to geographies in the southern United States, is spreading north. Meat allergies and the associated tick bites have been diagnosed in both New Hampshire and Minnesota.

How to prevent tick-based effects

The best way to prevent tick bites is to check yourself carefully for ticks after spending time outdoors in areas known to have ticks. Additionally, wearing long pants, long-sleeved shirts, and appropriate footwear in tick-infested regions is recommended. Keep pets protected with commercially available tick repellents. With the rise in ticks and incidence of tick-borne disease, it is paramount to take the necessary precautions.

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