Biology

Ticks, a health risk?

All of us who have cats or dogs at home have ever found one or more ticks attached to the animal’s skin. At least in those cats and dogs that sometimes go out on the street. These annoying arachnids can be removed with tweezers or oil, and there is no risk of transmission once they are attached to an animal. If it is not removed manually, the tick will let go of its own accord once it has satiated by drinking blood.

But do they pose any risk to human health? Is it correct to remove them using the mentioned methods? In this article we will talk about these and other topics related to ticks.

Some pretty annoying mites

Ticks are not insects, but arachnids. Specifically, they are a type of large mites. Adult individuals of some species can grow up to several centimeters when they are completely filled with the blood of an animal.

There are three families of ticks: the so-called soft ticks ( Argasidae ), which mainly parasitize birds; hard ticks ( Ixodidae ), which include most of the known species and can parasitize birds, mammals or reptiles; and a third family consisting of a single species,  Nuttalliella namaqua , native to southern Africa.

All ticks are blood-sucking ectoparasites . This means that they pierce the skin of the host animal and feed on its blood. A tick can grow several times in size as it feeds. The way these parasites reach their hosts is to perch on vegetation and latch onto the fur of an animal when it passes by (or a person’s clothing), from where they reach the skin.

a health risk
a health risk

Tick ​​saliva contains a number of analgesic, anti-inflammatory and anticoagulant substances, which makes their bite imperceptible and the wound does not close while the tick feeds. Once the host’s skin has been opened, the tick completely inserts its oral apparatus into the skin and secretes a substance that solidifies and keeps it firmly anchored to the wound.

Ticks as disease vectors

As with fleas and other blood-sucking insects, a tick can feed on several hosts throughout its life, and these can be of different species, so the tick acts as a vector for the transmission of bacteria and other pathogenic microorganisms between different species.

Some tick-borne diseases can be life threatening to humans. But before listing the number of diseases that ticks can transmit, two things should be clarified. 

The first, that the vast majority of tick bites are harmless , either because the tick does not transmit any pathogen or because it is detected and eliminated before it can transmit it. It is considered that bites lasting less than 35 hours does not involve a health risk .

Second, many of the potentially dangerous diseases that can be transmitted by ticks are located in a specific geographical area, where the animal species that acts as the natural host of the pathogen is found.

Perhaps the best known of all diseases that are transmitted by ticks is Lyme disease or borreliosis . This disease is caused by bacteria of the genus  Borrelia  present in Europe or North America, the effects of the disease can vary between paralysis of some part of the body, headaches or stiff neck. A peculiarity of this disease is that the symptoms can appear long after the tick bite and on some occasions the disease can persist chronically in the patient.

Other diseases of bacterial origin transmitted by ticks are typhus, tularemia or Rocky Mountain fever (known in Brazil as spotted fever). Even more dangerous are some viral diseases, such as meningoencephalitis caused by flaviviruses (in Europe and Asia) or Crimean-Congo hemorrhagic fever (mainly in Africa). A disease caused by protozoa and transmitted by ticks is babesiosis or piroplasmosis, similar to malaria.

A very particular case is the bite of the lone star tick ( Amblyomma americanum ), named for having a white spot on its reddish body. This tick is native to the northern part of South America and has been introduced in Mexico and the US. In addition to acting as a vector for the transmission of different diseases such as tularemia, Lyme disease or the Heartland virus, the tick’s own saliva can cause a persistent allergy to meat in the host . Once symptoms appear, eating red meat can lead to fatal anaphylactic shock. The causes of this striking phenomenon are not yet well understood, but it appears to be linked to immunoglobulin E, a type of antibody.

There is another disease caused by the saliva of some ticks, which is not caused by an infectious agent, and that is tick bite paralysis . This disease is caused by a neurotoxin that has not yet been isolated. Symptoms begin several days after the tick bite, when the tick is still attached to the host, and include muscle fatigue and progressive limb paralysis, which can lead to fatal respiratory failure. The best preventive technique for this disease (and the only one that exists) is the elimination of the tick, after which the symptoms that have manifested usually disappear progressively.

Ways to remove a tick

As we have already mentioned, ticks can transmit infectious pathogens found in the blood of their hosts. During the feeding stage of the tick, the tick ingests blood from the host and as it swells it may regurgitate some of the ingested blood back to the host, causing infection. For this reason, it is not recommended in any case to squeeze the body of the tick, where the ingested blood is located, or this backflow of blood mixed with pathogenic organisms could occur.

The well-known technique of covering the tick with oil or alcohol to free itself from the host is also not recommended, as it can cause a backflow of blood back to the host. Burning the tick can also cause this reflux.

The correct way to eliminate a tick is using tweezers , holding the mite by the part of the body closest to the jaws, avoiding squeezing the rest of the body. The tick should not be twisted while it is attached, as this could tear the skin. It should be pulled by moving the forceps up and down, until the jaws have become detached or dislodged. If the mouth remains of the tick have remained in the wound, they must be removed.

The wound must be disinfected later. We must ensure that the tick is dead once removed, wrapping it in duct tape is a surefire way to ensure this. Despite their small size, they are surprisingly tough if you try to crush them.

An optimal way to eliminate ticks is to kill them beforehand by applying cold locally, for example with an ethyl chloride spray. This avoids any possible reflux of the gastric contents of the tick and facilitates its subsequent removal with tweezers. In the event that we detect a tick on our skin, the best solution is usually to go to a medical center so that it can be safely removed there.

Tips for going to the field in tick season

To avoid these annoying mites during field trips, just follow a few small tips, especially in spring, which is the most intense time for these mites.

  • Wear clothing that covers the entire body such as long pants and long sleeves on the arms
  • Wear boots and socks that prevent ticks from sneaking in, such as the unsightly but very practical, wearing socks over pants
  • Clothes, if possible, be light in color to easily identify if a tick has landed on us
  • Use repellants to avoid them and avoid going through areas of lush vegetation because, as mentioned, ticks are perched there.
  • Sitting in areas with a lot of vegetation is also not recommended.
  • On the way home, check to see if a tick has attached itself to us, being more exhaustive with the hair, groin, armpits, navel, behind the ears … and shower.
  • Clothes back from the field should be washed in hot water.
  • If you go with pets to the countryside, use a good repellent and check it when you return home.

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