More than fifty species of ixodid ticks live on the territory of Russia, the most massive and widespread among which is Ixodes ricinus (which is also called the dog, European forest or common ixodid tick). In the people, this species is often called the borreliosis tick, since it is the main carrier of a dangerous infectious natural focal disease - Lyme borreliosis.
The photo below shows such a tick attached to a human body:
On a note
In terms of incidence, borreliosis occupies a leading place among natural focal infections and is one of the important problems of modern medicine, leading in terms of prevalence in most countries of Europe, Asia and the United States. Borreliosis accounts for approximately 90% of all diseases carried by arthropods.
About 8,000 cases of human Lyme borreliosis infection are registered annually in Russia alone. It should be borne in mind that without proper treatment, the disease can be deadly.
About the danger of Lyme borreliosis, the nuances of contracting it through tick bites and ways to prevent serious consequences - we will talk about all this further and talk in more detail ...
Spread of Lyme borreliosis
Tick-borne borreliosis is a very serious infectious disease, extremely dangerous for humans.In medicine, a number of synonyms are used:
- systemic tick-borne borreliosis;
- Lyme disease;
- Lyme borreliosis;
- chronic migratory erythema;
- tick erythema.
Some of these names briefly describe the symptoms of the disease, which, generally speaking, can vary in severity over a wide range. Because of this, the disease is often incorrectly identified and the necessary treatment is not prescribed in time. This circumstance also explains the fact that the causative agent of the disease was discovered and described relatively recently - at the same time, the role of ixodid ticks in the transfer of pathogens from wild animals to humans was also studied.
On a note
The name of the disease comes from the city in which there was a massive outbreak of human disease (the city of Lyme, Connecticut, USA). The clinical picture resembled arthritis, but this hypothesis was quickly ruled out, since most of the patients were young.
It wasn't until 1977 that the mysterious disease was discovered to be related to ticks. Having studied ticks of the genus Ixodes, experts found a pathogen in their body - a spirochete. But as a separate, independent disease, borreliosis was registered much later, only in 1984.
Sometimes the inhabitants call an infected tick a Lyme tick, believing that "Lime" is the name of a scientist who studied the disease. In fact, this is a big mistake: Allen Steer was studying the problem, and the word "Lyme" refers to a small town in which cases of the disease were recorded.
At this stage, tick-borne borreliosis is widespread in the USA, Europe, Australia, a number of African countries, China and Japan. Russia is no exception to this list - the disease occurs in many regions of our country.At the same time, experts note that there are more cases of human infection with Lyme disease every year, and there is even an opinion that borreliosis is second only to AIDS in terms of spread rate.
If you look at the map of the distribution of tick-borne borreliosis, you can see that the boundaries clearly coincide with the boundaries of the distribution area of the dog tick.
The fact that it is the common forest tick that plays the primary role in maintaining the focus of this disease is an indisputable fact at the moment. At the same time, of course, not every tick in a potentially dangerous area is borreliosis (that is, it is a carrier of spirochetes), but such a possibility is always present in most regions of Russia.
Natural reservoirs of the disease and the pathogen entering the tick
The spirochete Borrelia burgdorferi (named after its discoverer) is the causative agent of Lyme disease. It was isolated from the lymph, blood and cerebrospinal fluid of sick people. After some time, the bacterium was found in the organs and soft tissues of some animal species (deer, small rodents, birds).
The photo below shows what Borrelia look like at 400x magnification (laboratory samples stained with silver salts for contrast):
Ultimately, Borrelia was removed from the digestive tract of the ixodid tick. Thus, the leading role of ticks in the transfer of the pathogen from wild animals to humans was proved.
Borrelia in the natural environment is found exclusively in the body of a natural host. Experts number about 200 species of animals that are natural reservoirs of this type of spirochetes. The main ones are deer, dogs, cats, cattle, small mouse-like rodents (voles, gerbils, pied gerbils, hamsters) and a large number of birds belonging mainly to the family of Passeriformes.
On a note
Spirochetes are found in many host tissues and organs, but the highest concentration of Borrelia is found in the blood and lymph. So they circulate in the host's body for quite a long time, and at a certain stage, contact of the focus with the carrier, the ixodid tick, may occur.
Borrelia, together with the blood of the animal on which the tick feeds, enter the body of the parasite. First, they are in the intestines of the tick for some time. Further (after about 5-6 hours), spirochetes migrate through the membrane of the esophagus into the hemolymph (analogous to our blood) and spread throughout the body of the parasite.
However, the density of colonization of the organs of the tick by borrelias is not the same: their greatest number is found in the salivary glands and malpighian vessels (excretion organs) - this circumstance plays a primary role in the transmission of the pathogen from the tick to humans.
On a note
Ticks are universal carriers of spirochetes and some other pathogens of dangerous diseases. Microorganisms, along with the blood, enter the intestines of the tick, from where they migrate throughout its body. The internal environment in terms of temperature and pH is favorable for the vital activity of the pathogen, and the absence of a special membrane in the intestine, as in insects, allows bacteria to freely penetrate into any tissues and organs of the parasite.
As noted above, not every ixodid tick is borreliosis. That is, in the body of a tick, pathogens of borreliosis will not necessarily be contained.For example, if the parasite did not feed on sick animals, then it is epidemiologically clean.
Ixodid ticks are the main carriers of Lyme disease.
The dog tick is one of the main carriers of Lyme disease in Russia and, accordingly, plays a key role in the territorial spread of the infection. However, not only he can carry borrelia in himself.
Spirochetes are also found in the body of the taiga tick Ixodes persulcatus (the so-called encephalitic tick), as well as other representatives of the genus Ixodes:
- I. dammini;
- pacificus;
- I. scapularis;
- tanguliceps.
However, these species either do not occur in Russia, or are relatively few in number, and therefore do not play an important role in the spread of the disease.
Below in the photo is a taiga tick (for a non-specialist, it will not be so easy to distinguish it from a dog one):
The dog tick lives almost everywhere on the territory of our country (mainly in forests). The density of populations is uneven and is rather local. Mass outbreaks of the parasite are periodically observed, and the tick is most active in spring and autumn.
The life cycle takes place according to the type characteristic of all Iksodov and consists of four stages:
- Egg;
- Larva;
- Nymph;
- Adult individual (imago).
In the spring, the female lays eggs on grass or other substrate, then larvae develop in them.
The photo below shows the eggs of a dog tick:
After the larvae hatch from the eggs, they begin an active search for a host. At this stage, ticks parasitize mainly on small rodents, which are natural reservoirs of borreliosis. Already in this period, there is a transition of spirochetes into a tick.
Having fed, the larvae go to winter or molt into nymphs.
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The tick nymph differs from the larva in the number of pairs of legs - the nymph has 4 of them, and the larva has only 3.
For further development, nymphs also need to suck on blood, and they choose their victims from larger wild animals, or birds, which may also contain Borrelia in their bodies. The constant need for all stages of the tick's life cycle in food increases the chances that the tick will be saturated with the blood of a sick animal and become "borreliosis".
After winter diapause, nymphs molt into adults.
It is interesting
Borrelia are in the body of a tick from the moment it enters it along with the blood of a sick animal. In the process of development, the tick molts, and complex rearrangements occur in its body, but this does not affect the viability of spirochetes in any way. Even after a long time, the borreliosis tick remains contagious.
Borrelia is capable of being in a metabolically inactive state for a long time in the midgut of ixodid ticks (for example, during the wintering period of the parasite). After the tick is sucked and the first portions of blood enter its gastrointestinal tract, Borrelia begin to multiply actively.
An adult tick has an oval body, covered from above with a shiny shield. In females, the shield occupies 1/3 of the dorsal surface, in males it completely covers the back. Both females and males can be carriers of tick-borne borreliosis.
Outwardly, an infected tick looks absolutely identical to an uninfected individual. It is also impossible to distinguish them morphologically. To determine whether a tick is a carrier of borreliosis, it is necessary to conduct special laboratory tests.
How does a person become infected with borreliosis
Currently, in addition to natural foci of Lyme disease, anthropogenic foci are also formed, where the disease circulates not only between ticks and wild animals, but is also relatively often transferred to humans. The carrier of infection is found in park areas, in squares and on the streets of large and small cities, where infection may well occur.
Ticks are found in almost all plant communities of the city. But their greatest number is observed along forest roads and paths, in overgrown clearings, in ravines and gullies, along river floodplains.
Usually a person is bitten by adult ticks (adults), the probability of infection, from which, is much higher. However cases of infection of the person and from nymphs are registered. In general, it is not so important at what stage of ontogenesis the tick became a carrier of Lyme disease: when bitten, pathogens can still enter the victim's body.
The disease from a tick is transmitted transmissibly, when, when a person is bitten by a tick, pathogens pass into our circulatory system. The tick releases a large amount of saliva into the wound to prevent blood from clotting. Along with saliva, Borrelia also enter the human body.
If the borreliosis tick just crawled through the body, but did not have time to bite, then infection will not occur (although there are rare exceptions).
On a note
The causative agents of borreliosis can enter our body in other ways. Since a large number of Borrelia are contained not only in the salivary glands of the tick, but also in the excretory organs - Malpighian vessels, there are also a large number of them in the excrement of the parasite.With prolonged feeding on a person, the tick defecates, and spirochetes can enter the body through damaged areas of the skin.
Thus, the longer the tick is on the body, the higher the likelihood of infection. However, even if bitten by a borreliosis tick, a person may not get sick, because our body has immune defense reactions. As a result, according to statistics, the probability of contracting borreliosis with a tick bite is approximately 5 cases per 100 episodes of suction.
Clinical picture of the disease: its symptoms and danger
Initially, pathogens are concentrated in large numbers at the site of the bite, thereby causing a local immune response. A bright red spot (erythema) appears in the center of the bite, which increases in diameter - sometimes up to 5 centimeters or more. This is the first and clear sign of human infection with borreliosis.
Erythema can migrate throughout the body: more often it develops on the thigh, in the inguinal and axillary regions. At this stage, a person, as a rule, is not bothered by fever and other characteristic symptoms.
Erythema migrans has now been proven to be an integral clinical sign of Lyme borreliosis. (although not always noticed by patients in time, which can make it difficult to diagnose when the infection moves to the next stage).
The second stage of Lyme disease develops approximately in the second month after infection and is characterized by damage to several organs and systems at once:
- skin cover;
- musculoskeletal system;
- of cardio-vascular system;
- nervous system.
Skin lesions appear most quickly and are expressed in a large number of erythema and subcutaneous nodules on the body, which often disappear and appear, and also change their localization.There are pains in the joints (as in arthritis), the patient feels aching pain in the limbs. Pains can change their location and disappear as suddenly as they arise.
The defeat of the cardiovascular system is much less common. These can be inflammatory processes in the heart muscle (myocardium) or a violation of the conduction of an electrical impulse in the heart, which is potentially threatening to the life of the whole organism.
Damage to the nervous system manifests itself in periodic severe headaches, as with meningitis, but without nausea and vomiting. Often there is a burning pain between the shoulder blades, in the chest and in the lower extremities. In the elderly, these symptoms are most pronounced and are most pronounced at night.
If the disease is started and the necessary measures are not taken in time, then the third stage of borreliosis develops, also called late. It is characterized by a more serious lesion of any of the body systems.
If Lyme arthritis develops, then large joints are severely affected: knee, shoulder, elbow, less often - hip and small (joints of the hands and feet). Typical symptoms of arthritis appear: swelling, severe pain, limited joint mobility.
The acute phase can last several months, after which there comes an equally long stage of "rest". At this stage, all methods of clinical diagnostics show the absence of pathogens of borreliosis in the body.
Skin lesions at a late stage are manifested in the form of atrophic rashes throughout the body. At the same time, large purple spots appear on the limbs, on which the skin dies over time.
But the most dangerous is precisely the neglected neuroborreliosis, when the nervous system is affected. Among the dominant clinical manifestations in this case are noted:
- short-term severe pain in the face;
- paralysis of the upper or lower extremities;
- dysfunction of the pelvic organs;
- decrease in memory and mental abilities.
On a note
With such a development of borreliosis, it is at this stage that the strongest mental disorders are manifested, characterized by aggressiveness and prolonged depression, up to memory loss.
Borreliosis is especially dangerous for children (borreliosis ticks can bite them while playing outdoors). School-age children are often infected, but preschoolers after contact with Borrelia are much less likely to get sick.
The course and symptoms of the disease in children are similar to those in adults. However, children develop meningitis more often and faster. Since the nervous system is affected, even after complete recovery, almost 90% of children show consequences: sleep disturbances, depressive mood, and unhealthy nervous reactions.
If a borreliosis tick has bitten a pregnant woman, then no special complications appear. In the scientific literature, there are no data on intrauterine infection with borreliosis of the fetus or complications of pregnancy. Animal experiments have shown that there is no direct relationship between infection of the mother with borreliosis and premature birth or miscarriage, as well as a variety of fetal pathologies.
What to do with a tick bite to prevent dangerous consequences
Lyme disease responds well to broad-spectrum antibiotics (such as tetracycline). Even the third, especially advanced stage, responds well to treatment.But in order to initially protect yourself from a number of serious problems that may arise after a tick bite, it is better to foresee a set of preventive measures in advance.
Preventive actions should primarily be aimed at minimizing the likelihood of contact with ticks. Unlike tick-borne encephalitis, there is no vaccine for Lyme disease. Therefore, when you are in nature, you should avoid the most likely places of mass accumulation of ticks (paths of animals, old localities overgrown with grass and shrubs).
Do not neglect protection methods such as repellents, treating your clothes and exposed areas of the body with them every time you go to nature. The most important thing is to periodically carefully examine yourself and loved ones for the presence of ticks on the body.
If the tick nevertheless sticks, it must be removed from the skin as soon as possible, and very carefully so that the head of the parasite or its proboscis does not remain in the wound. The longer the borreliosis tick sucks blood, the higher the chance of infection.
After removing the parasite from the body, the wound should be treated with an antiseptic (for example, an alcohol solution of iodine, brilliant green or hydrogen peroxide). The extracted tick must be taken to a diagnostic center for examination. Further, experts will prompt an algorithm of actions in case the tick turns out to be infected.
Useful video: what is important to know about tick-borne borreliosis (Lyme disease)
What to do first when bitten by a tick
