Human fleas: distribution, routes of infection

1. home
2. Pest control
3. Destruction of fleas
4. Diseases transmitted by fleas

Fleas are found in both warm and cold areas.
However, parasites are most widespread in subtropical and temperate climates. In addition to climate, seasonal weather fluctuations also affect pest numbers. For example, during periods of moderate temperature (when it is neither hot nor cold), populations reach their maximum numbers. According to confirmed data, there are more than 2000 varieties of fleas. They comprise 15 different families. Some of the most common families include Ischnopsyllidae, Ceratophyllidae and Hystrichopsyllidae. The most studied are the so-called rat (Xenopsylla cheopis) and human (Pulex imtans) fleas. As you might guess, the victims of these species are humans or rats: the parasite feeds on the blood of its victim. Interestingly, sometimes warm-blooded birds and animals can also become victims. And sometimes several types of parasites can live on one creature at once. Fleas easily change hosts, jumping from one to another.

But there are also species that can only inhabit a certain type of animal. For example, fleas from bats cannot jump from them to another species of animal or to a person.

Intensive study of these pests began immediately after it was discovered that they were active carriers of the plague. To date, 60 species have been identified that are capable of transmitting more than 25 diseases. Both people and animals can become infected. In addition, fleas can become carriers and, accordingly, temporary hosts of parasitic worms. Jumping from rodents to people, individuals are capable of transmitting such terrible diseases as plague, rat typhus, etc.

Transmission of the infection occurs either through a bite or through insect excrement. At the time of the bite, the parasite’s saliva enters the skin, which causes severe irritation, itching, and inflammation. If the bite was caused by a penetrating flea (Sarcopsylla penetrans), there is a high risk of developing gangrene and even losing a limb.

Signs of a human flea

These insects are classified as temporary blood-sucking pests. The habitat becomes burrows and other habitats of domestic animals and rodents, which the parasites attack for the purpose of feeding.

In the process of evolution, insects lost their wings and became wingless for the second time. The type of oral apparatus is piercing-sucking. Its main purpose is to pierce the skin of warm-blooded creatures for feeding.

The body of the individual is quite long, flattened on the sides. The body consists of a head, abdomen, chest and three pairs of legs. Individuals move by jumping from place to place; the second and third pairs of legs are used for pushing, which allows them to jump quite high. The paws end in claws, which ensures rapid movement across the surface and a tenacious hold on the body of their prey. The parasite is protected from being crushed by a thick layer of hair, which in some way resembles thorns.

Diseases that fleas can transmit

With the passage of time, the sanitary situation of cities does not improve, but rather the opposite. With the growth of industrial facilities, the amount of waste increases, hence all kinds of insects, etc. In this regard, people are increasingly interested in the question of where fleas come from and how to get rid of them.

A major role in the spread of diseases is played by the parasite’s tendency to change hosts – so-called temporary parasitism. When an individual sucks blood, it becomes infected with flea plague. The bacteria become established in the insect's body and can later be spread along with it over vast distances, entering other organisms through bites. Despite the fact that the causative agent of the disease can remain in an active state in the body of a flea throughout its life, it is not transmitted to its offspring.

It is rat parasites that transmit infections in a unique way. They spread endemic flea and epidemic typhus. A person can get the virus through a bite and contact of broken skin, respiratory tract or mucous membranes with rodent excrement. The infection process occurs most easily in warm regions, especially if there has been a massive spread of the pathogen among rodents.

Along with typhus, the flea body retains the causative agents of tularemia, melioidosis, pseudotuberculosis, anthrax, etc. for a long time. Human fleas, as well as cat and dog fleas, are often carriers of helminths.

Faces of Plague

Currently, the main forms of plague are bubonic, pneumonic and septicemic. Occasionally, other varieties are also found: cutaneous, intestinal, pharyngeal and meningeal. Bubonic plague usually develops after the bite of a flea carrying Y. pestis or after working with the carcasses of infected animals and is characterized by inflammation of the lymph nodes with the formation of their painful conglomerates - “buboes”, “bumps” of different sizes. If treatment is not treated in time, the infection can become generalized: sepsis (secondary septicemic plague) or pneumonia (secondary pneumonic plague) develops. In the latter case, the sputum serves as an infectious substance for other people, who subsequently develop primary pneumonic plague. It is precisely because of the ability to be transmitted from person to person (by airborne droplets) that the pulmonary form of the disease causes the greatest concern. Septic and pulmonary forms sometimes occur at lightning speed, and death cannot be avoided without emergency antibiotic therapy.

It is possible that the predominance of any form of plague (predominant damage to one or another organ) during various epidemics is associated not only with the mechanisms of bacterial transmission, but also with the properties of a particular pathogen strain.

The decisive factor was the third pandemic, which broke out in China in 1855. All scientific forces, which had become considerably stronger by that time, were thrown into solving the most terrible mystery. Finally, in 1894, research by the French bacteriologist Alexandre Yersin and the Japanese physician Shibasaburō Kitasato, conducted independently of each other in Hong Kong, brought long-awaited results. By examining human pathological material and rodent corpses, Kitasato and Yersin isolated and described the coccobacilli believed to cause plague. And if Yersin’s results did not raise any complaints, the Japanese bacteriologist’s reputation was considerably damaged (and caused endless disputes regarding the priority in the discovery of the plague bacillus) by contradictions in the description of the pathogen, apparently explained by contamination of samples with opportunistic pneumococci [4].

Can humans have fleas?

Despite its name, this type of parasite cannot have a permanent residence on the human body. The individual visits the human body only during feeding moments. Individuals constantly live in the folds of clothes and linen, in carpets, in pets’ bedding, in furniture, etc.

It is a misconception that pests prefer human hair. In fact, a variety of parts of the human body can be bitten: arms, legs, back, stomach, neck and sometimes the face. Visually, the bites look like large red pimples. They are accompanied by itching and sometimes develop into allergic reactions.

To cope with unpleasant sensations, you should apply a cooling cream to the bite site. The drug should be an antihistamine or antipruritic, for example, the drug "Fenistil". If there are scratches and, as a result, abrasions, it is necessary to treat this area with an antiseptic.

Pest prevention

Of course, most often you should pay close attention to the animals around you. That is:

• If you occasionally visit nurseries or other similar places, use insect repellent spray. Treat clothing and exposed skin every time.
• Also treat your pets with care: carefully inspect their fur, because they can bring parasites from garbage dumps or from other animals.
• It's better to be safe than to end up with a problem. So, buy a pet product to protect them from pests. This could be a collar or a special product for applying to the coat.

If somehow insects entered the house and started hunting you, you need to immediately take decisive action. Unfortunately, local treatment of yourself and animals will not solve the problem. But there is a reliable way to kill a human flea.

What do bedbugs look like?

Insects are distinguished by a flat, wide body measuring from 4 to 8 mm. This body shape helps parasites survive in bed conditions, reducing the risk of being crushed by a sleeping person. In a well-fed state, they enlarge and become more vulnerable. Bedbugs have no wings, and the constrictions on the back are clearly visible. Bedbug larvae are similar to adults, but their color is less saturated. The eggs of these insects can be mistaken for small grains of rice. Their length does not exceed one millimeter.

Ways to fight

The most effective is considered to be the adoption of exterminatory measures in places where parasites are especially concentrated, as well as manipulations to stop the reproduction of a particular population. In such cases, when burrows are discovered, aerosol bombs are used for deep treatment with insecticides.

If a source of pest spread has been found in nature, a study of the territory in the system is carried out, forecasts are made for the further development of the colony and, importantly, planned epizootological monitoring is carried out, that is, the colony is checked for the presence of infections.

Indoors, pests multiply in the burrows of synanthropic rodents; in addition, their habitats include accumulations of dust and debris, cracks in the floor, and places where pets regularly stay.

Literature

1. It's better to see once, or Ultra-high-resolution microscopy;
2. Beyond the diffraction barrier: Nobel Prize in Chemistry 2014;
3. Plague. The Black Death. National Geographic website;
4. Bibel D. J. and Chen T. H. (1976). Diagnosis of plaque: an analysis of the Yersin-Kitasato controversy. Bacteriol. Rev. 40 (3), 633–651;
5. Suntsov V.V. and Suntsova N.I. Plague. Origin and evolution of the epizootic system (ecological, geographical and social aspects). M.: KMK, 2006. - 247 p.;
6. Zimbler DL, Schroeder JA, Eddy JL, Lathem WW (2015). Early emergence of Yersinia pestis as a severe respiratory pathogen. Nature. 6, 7487;
7. Caulfield AJ, Walker ME, Gielda LM, Lathem WW (2014). The Pla protease of Yersinia pestis degrades fas ligand to manipulate host cell death and inflammation. Cell Host Microbe. 15 (4), 424–434;
8. Fleas. Illinois Department of Public Health website;
9. Zilber L.A. (1966). Operation "ORE". Science and life. 12;
10. It's a plague;
11. Mammoths, bones and drug resistance: new technologies allow studying the evolution of infectious disease agents;
12. Attic: “European rats turned out to be innocent in medieval plague epidemics.”

Types of pest control

Deratization refers to actions to destroy and prevent the appearance of pathogenic insects. Depending on the situation, disinfestation can be of two types:

1. Emergency . Emergency disinfestation is based on the process of exterminating individuals at a specific site. This occurs if the presence of a colony at the facility is confirmed. If the customer only has suspicions, the sanitary service master travels and conducts an analysis on site to determine the presence and nature of the infection.
2. Preventive . Prevention measures include both household and chemical measures. At the household level, it is recommended to carefully monitor the condition of pets and the cleanliness of residential and industrial premises. However, speaking about government and commercial institutions, scheduled chemical treatments are mandatory. Such work requires less time and resources, which also makes its cost lower. Of particular importance in this case is sanitary control over port cities and railway stations, where imported sick rodents may appear.

Victim of mutation

It has been known for quite some time that the ancestor of the plague bacillus is Yersinia pseudotuberculosis, an enteropathogen, the causative agent of pseudotuberculosis. Presumably, Y. pestis separated from its ancestral species about twenty thousand years ago. The reason for the evolution was a sharp climate change in the late Pleistocene (the Quaternary period of the Cenozoic era): cold was replaced by heat, causing a restructuring of ecosystems; As a rule, such weather “jumps” stimulate the evolution of species [5]. However, until recently, the genetic changes critical for the transformation of a pathogen that causes an infectious intestinal disease into a dangerous microorganism that can infect the lungs and provoke fulminant sepsis were not known.

The evolutionary branch of Y. pestis was studied by scientists from Northwestern University in the USA. In the study, Wyndham Lathem and Daniel Zimbler found that the acquisition of a single gene transformed early forms of Y. pestis, already somewhat genetically and phenotypically different from Y. pseudotuberculosis, into a successful pulmonary pathogen. To identify the mechanism of “relocation” of the plague bacillus from the intestines to the lungs, the authors conducted experiments on ancient strains of bacteria and analyzed their behavior in the body of mice. When comparing strains that cause pneumonic plague with relatively harmless ancestors, only one, but very significant, difference was revealed: the acquisition of the surface protein Pla (see sidebar) as part of the pPCP1 plasmid became critical. To test the hypothesis, this gene was introduced into the DNA of evolutionarily earlier strains - and the results confirmed the involvement of the Pla protease in effective damage to the respiratory tract.

However, this acquisition of Y. pestis was not enough to learn how to cause a very dangerous systemic infection (septic form of plague). It turned out that such an improvement required only one (!) amino acid substitution in the Pla protein - I259T . This substitution optimized the proteolytic activity of the protein and significantly increased the invasive potential of bacteria during the development of bubonic plague. Thus, scientists believe that first of all, the bacterium acquired the properties of a pulmonary pathogen, a provocateur of outbreaks of pneumonic plague, and later, as a result of an additional mutation, even more dangerous strains appeared that cause pandemics of pulmonary septic and bubonic septic plague [6].

Nevertheless, among all the disadvantages of Y. pestis, scientists also find advantages of its contact with people. In 2014, the journal PLoS ONE published an article by Sharon de Witte from the University of South Carolina, which stated that people who survived the plague pandemic experienced better health. Scientists examined the remains of people who lived before, during and after the plague, paying special attention to the causes of death and the condition of their bones. The results showed that survivors of the epidemic, as well as their descendants, lived on average to 75 years and had enviable immunity.

Stages of professional pest control

Let's look at the stages of professional pest extermination.

1. Preparing the premises for disinfestation

The degree of effectiveness of the procedure depends not only on the professionalism of the specialist, but also on the extent to which the instructions for preparing the premises for treatment are followed. Instructions are provided by the SES operator by telephone before the specialist arrives.

In different cases, the necessary actions may differ. But in general they come down to the following list:

• The kitchen area should be prepared in this way: collect all the dishes and food and pack them in bags, then put them in cabinets. The same must be done in relation to pet food and bowls.
• Personal items (combs, toothbrushes, etc.) should also not be exposed to chemicals. So they pack up and go away.
• It is strictly recommended to carry out wet cleaning to remove dust and dirt from the floor and all surfaces. The fact is that a layer of dust will prevent the action of chemicals on the surface, which will significantly shorten the period of action of the substances.
• The aquarium (if there is one) should also be prepared: turn off the air supply and close the lid tightly until work is completed.

1. Work of an SES employee

Having arrived at the site, which has already been prepared by the customer, the employee begins to destroy the human flea.

• Assessment of the situation. A competent specialist will definitely make a final inspection to ensure that the correct pest control strategy and appropriate products have been selected.
• Preparation of drugs. Having identified all the locations of the parasites and the degree of infection, the master prepares a chemical solution. To do this, you need to accurately calculate the dosage and concentration.
• Treatment. The application procedure itself does not take much time. Thanks to a modern development - a fog generator - the master is able to quickly and evenly spray the chemical in an infected room.
• Recommendations. Before leaving, the SES officer provides recommendations on preventing the appearance of insects in the future.

1. Final steps after killing fleas

To consolidate the effect, as well as protect the family from poisoning, it is important to follow the rules:

• The drug should infuse for 1 hour. This means that the windows and doors of the apartment must remain closed.
• After this, it is necessary to thoroughly ventilate the home. 2-3 hours will be enough for this.
• Before all family members return home, all work surfaces should be wiped down with a damp cloth. You should also wet clean the floor, retreating 10 centimeters from the baseboard. It is recommended to refrain from general cleaning for 3 weeks.
• Bed linen and furniture covers must be removed and washed at high temperature. This will achieve two goals at once: the destruction of the chemical odor and the extermination of those individuals that were hiding in things.