The 2016 forecast for Lyme disease in 2016 and in-depth coverage of the early symptoms,Centers for Disease Control and Prevention.
Lyme Disease
Lyme Disease
Symptoms and Prevention
Lyme disease, also known as Lyme borreliosis, is an infectious disease caused by bacteria of the Borrelia type. The most common sign of infection is an expanding area of redness, known as erythema migrans, that begins at the site of a tick bite about a week after it has occurred. The rash is typically neither itchy nor painful. Approximately 25–50% of infected people do not develop a rash. Other early symptoms may include fever, headache and feeling tired. If untreated, symptoms may include loss of the ability to move one or both sides of the face, joint pains, severe headaches with neck stiffness, or heart palpitations, among others. Months to years later, repeated episodes of joint pain and swelling may occur. Occasionally, people develop shooting pains or tingling in their arms and legs. Despite appropriate treatment, about 10 to 20% of people develop joint pains, memory problems, and feel tired for at least six months.Lyme disease is transmitted to humans by the bite of infected ticks of the Ixodes genus. Usually, the tick must be attached for 36 to 48 hours before the bacteria can spread. In North America, Borrelia burgdorferi sensu stricto and Borrelia mayonii are the cause. In Europe and Asia, the bacteria Borrelia afzelii and Borrelia garinii are also causes of the disease. The disease does not appear to be transmissible between people, by other animals, or through food. Diagnosis is based upon a combination of symptoms, history of tick exposure, and possibly testing for specific antibodies in the blood. Blood tests are often negative in the early stages of the disease. Testing of individual ticks is not typically useful.
Where is the black-legged tick population concentrated?
The Northeast continues to have the most concentrated areas of Lyme cases. But the black-legged tick is now present in nearly half of U.S. counties in 43 states, a jump of nearly 45% since 1998, according to a recent CDC report. The majority of the tick population growth has been in the North-central and Northeast.Sign and Symptoms
Lyme disease can affect multiple body systems and produce a broad range of symptoms. Not all patients with Lyme disease have all symptoms, and many of the symptoms are not specific to Lyme disease, but can occur with other diseases, as well. The incubation periodfrom infection to the onset of symptoms is usually one to two weeks, but can be much shorter (days), or much longer (months to years).Symptoms most often occur from May to September, because the nymphal stage of the tick is responsible for most cases.Asymptomatic infection exists, but occurs in less than 7% of infected individuals in the United States.Asymptomatic infection may be much more common among those infected in Europe.
Early Infection
This "classic" bull's-eye rash |
Early localized infection can occur when the infection has not yet spread throughout the body. Only the site where the infection has first come into contact with the skin is affected. The classic sign of early local infection with Lyme disease is a circular, outwardly expanding rash called erythema chronicum migrans (EM), which occurs at the site of the tick bite three to 32 days after the tick bite. The rash is red, and may be warm, but is generally painless. Classically, the innermost portion remains dark red and becomes indurated (is thicker and firmer), the outer edge remains red, and the portion in between clears, giving the appearance of a bull's eye. However, partial clearing is uncommon, and the bull's-eye pattern more often involves central redness.
The EM rash associated with early infection is found in about 70-80% of people infected. It can have a range of appearances including the classic target bull's-eye lesion and nontarget appearing lesions. The 20-30% without the EM and the nontarget lesions can often cause misidentification of Lyme disease. Affected individuals can also experience flu-like symptoms, such as headache, muscle soreness, fever, and malaise. Lyme disease can progress to later stages even in people who do not develop a rash.
Prevention
Protective clothing includes a hat, long-sleeved shirt, and long pants tucked into socks or boots. Light-colored clothing makes the tick more easily visible before it attaches itself. People should use special care in handling and allowing outdoor pets inside homes because they can bring ticks into the house. People who work in areas with woods, bushes, leaf litter, and tall grass are at risk of becoming infected with Lyme at work. Employers can reduce the risk for employees by providing education on Lyme transmission and infection risks, and about how to check themselves for ticks on the groin, armpits, and hair. Work clothing used in risky areas should be washed in hot water and dried in a hot dryer to kill any ticks.Permethrin sprayed on clothing kills ticks on contact, and is sold for this purpose. According to the CDC, only DEET is effective at repelling ticks.
Management of host animals
Lyme and other deer tick-borne diseases can sometimes be reduced by greatly reducing the deer population on which the adult ticks depend for feeding and reproduction. Lyme disease cases fell following deer eradication on an island, Monhegan, Maineand following deer control in Mumford Cove, Connecticut. It is worth noting that eliminating deer may lead to a temporary increase in tick density.For example, in the U.S., reducing the deer population to levels of 8 to 10 per square mile (from the current levels of 60 or more deer per square mile in the areas of the country with the highest Lyme disease rates), may reduce tick numbers and reduce the spread of Lyme and other tick-borne diseases. However, such a drastic reduction may be very difficult to implement in many areas, and low to moderate densities of deer or other large mammal hosts may continue to feed sufficient adult ticks to maintain larval densities at high levels. Routine veterinary control of ticks of domestic animals, including livestock, by use of acaricides can contribute to reducing exposure of humans to ticks.
Action can be taken to avoid getting bitten by ticks by using insect repellants, for example, those that contain DEET. DEET-containing repellants are thought to be moderately effective in the prevention of tick bites.
In Europe known reservoirs of Borrelia burgdorferi were 9 small mammals, 7 medium-sized mammals and 16 species of birds (including passerines, sea-birds and pheasants). These animals seem to transmit spirochetes to ticks and thus participate in the natural circulation of B. burgdorferi in Europe. The house mouse is also suspected as well as other species of small rodents, particularly in Eastern Europe and Russia.
"The reservoir species that contain the most pathogens are the European roe deer Capreolus capreolus; "it does not appear to serve as a major reservoir of B. burgdorferi" thought Jaenson & al. (1992) (incompetent host for B. burgdorferi and TBE virus) but it is important for feeding the ticks, as red deer and wild boars (Sus scrofa), in which one Rickettsia and three Borrelia species were identified", with high risks of coinfection in roe deer. Nevertheless, in the 2000s, in roe deer in Europe " two species of Rickettsia and two species of Borrelia were identified".
Vaccination
A recombinant vaccine against Lyme disease, based on the outer surface protein A (ospA) of B. burgdorferi, was developed by SmithKline Beecham. In clinical trials involving more than 10,000 people, the vaccine, called LYMErix, was found to confer protective immunity to Borrelia in 76% of adults and 100% of children with only mild or moderate and transient adverse effects. LYMErix was approved on the basis of these trials by the Food and Drug Administration (FDA) on December 21, 1998.Following approval of the vaccine, its entry in clinical practice was slow for a variety of reasons, including its cost, which was often not reimbursed by insurance companies.Subsequently, hundreds of vaccine recipients reported they had developed autoimmune side effects. Supported by some patient advocacy groups, a number of class-action lawsuits were filed against GlaxoSmithKline, alleging the vaccine had caused these health problems. These claims were investigated by the FDA and the Centers for Disease Control, which found no connection between the vaccine and the autoimmune complaints.
Despite the lack of evidence that the complaints were caused by the vaccine, sales plummeted and LYMErix was withdrawn from the U.S. market by GlaxoSmithKline in February 2002, in the setting of negative media coverage and fears of vaccine side effects. The fate of LYMErix was described in the medical literature as a "cautionary tale"; an editorial in Nature cited the withdrawal of LYMErix as an instance in which "unfounded public fears place pressures on vaccine developers that go beyond reasonable safety considerations." The original developer of the OspA vaccine at the Max Planck Institute told Nature: "This just shows how irrational the world can be... There was no scientific justification for the first OspA vaccine LYMErix being pulled."
New vaccines are being researched using outer surface protein C (OspC) and glycolipoprotein as methods of immunization. Vaccines have been formulated and approved for prevention of Lyme disease in dogs. Currently, three Lyme disease vaccines are available. LymeVax, formulated by Fort Dodge Laboratories, contains intact dead spirochetes which expose the host to the organism. Galaxy Lyme, Intervet-Schering-Plough's vaccine, targets proteins OspC and OspA. The OspC antibodies kill any of the bacteria that have not been killed by the OspA antibodies. Canine Recombinant Lyme, formulated by Merial, generates antibodies against the OspA protein so a tick feeding on a vaccinated dog draws in blood full of anti-OspA antibodies, which kill the spirochetes in the tick's gut before they are transmitted to the dog.
Tick removal
Attached ticks should be removed promptly, as removal within 36 hours can reduce transmission rates. Folk remedies for tick removal tend to be ineffective, offer no advantages in preventing the transfer of disease, and may increase the risks of transmission or infection. The best method is simply to pull the tick out with tweezers as close to the skin as possible, without twisting, and avoiding crushing the body of the tick or removing the head from the tick's body. The risk of infection increases with the time the tick is attached, and if a tick is attached for fewer than 24 hours, infection is unlikely. However, since these ticks are very small, especially in the nymph stage, prompt detection is quite difficult. The Australian Society of Clinical Immunology recommends against using tweezers to remove ticks but rather to kill the tick first by using a product to rapidly freeze the tick to prevent it from injecting more allergen-containing saliva. In a tick allergic person, the tick should be killed and removed in a safe place (e.g. an emergency department of a hospital).