The main characteristic of natural focal diseases is that their pathogens are transmitted to humans from birds or animals. As a rule, transmission occurs through the bites of blood-sucking insects, for example, mosquitoes. Several pathogens can co-exist in one natural focus: bacteria, viruses, helminths, protozoa, etc. In order to protect themselves from natural focal diseases, many of which pose a serious threat to people's lives, it is important to have information about the transmission routes and methods of prevention Diseases.
What is a "natural hearth"?
The phrase "natural focus" directly indicates that the source of infection exists in nature. Transmissible and natural focal diseases are associated with certain biogeocenoses. The causative agents of natural focal diseases have the property of being transmitted from people to animals, which means that a person who finds himself in a similar biogeocenosis can be infected. In this case, pathogens are transmitted in various ways: through insect bites, by inhalation of dried excrement of infected animals, etc.
The teaching of Academician EN Pavlovsky
The doctrine of natural focal diseases of Academician Pavlovsky is one of the most outstanding achievements of biological science.
Pavlovsky's teaching says that in some landscapes there are foci of diseases that can be transmitted to a person. These foci are formed during the long evolutionary development of biogeocenosis.
A natural-focal disease occurs when there are three links at the same time:
- population of pathogens;
- population of animals that are hosts (reservoirs) of pathogens;
- population of vectors of pathogens.
For example, the natural focal diseases include the Pendin ulcer, which is common in some areas of Central Asia. The causative agent of the disease are leishmania. The reservoir of leishmania is gerbils - small rodents, living in deserts. And the leishmania is transferred through mosquito bites.
In one territory, several foci of diseases may be present simultaneously, which is important to take into account when developing preventive measures.
Varieties of natural foci
The natural-focal disease can be of two types:
- monovector - in the transmission of pathogens from one organism to another, only one vector can participate;
- polyvector - transmission can be carried out by several types of vectors.
E. N. Pavlovsky identified another type of natural foci - anthropurgic. The appearance of these foci is due to human activity and the ability of some vectors to pass to a synanthropic existence. Such carriers, for example mosquitoes or mites, are found mainly in urban or rural conditions, that is, not far from a person's home.
Carriers of natural focal diseases
Natural focal infectious diseases can be spread by two types of vectors: specific and nonspecific. In the organisms of specific vectors, the causative agent of the disease passes through several stages of its life cycle: it multiplies, accumulates, or even turns from an egg into a larva. The causative agent can maintain its vital activity only in the organism of a specific vector, having adapted to it in the process of evolutionary development.
Nonspecific vectors move causative agents mechanically. In this case, the pathogen remains for some time either on the proboscis or in the intestine of the distributor.
How can infection occur?
Infection with natural focal diseases can occur in various ways:
- industrial contamination is associated with work carried out on or near the forest areas, infection can occur during construction or logging operations, during harvesting of flax, vegetables, etc .;
- contamination when working in the suburban area: often rodents that carry the infection live in cottages or sheds, infection can occur by inhaling dried feces of mice and rats;
- household contamination, which often occurs in houses located near forests, is caused by the fact that rodents penetrate into sheds, cellars or into living quarters;
- infection during a short stay in the forest, for example, on a walk or in a hiking trip.
The most common diseases
Tick-borne encephalitis is a natural-focal disease characterized by severe intoxication and damage to the brain and spinal cord. Patients develop persistent irreversible neurologic disorders, a lethal outcome is possible.
Japanese encephalitis is an acute disease that occurs with damage to the brain and its membranes. The transporter of Japanese encephalitis is mosquitoes. The main symptoms: lethargy, fatigue, speech and vision disorders, fever, chills and vomiting. A lethal outcome is observed in 40-70% of cases.
Rabies is one of the most dangerous natural focal diseases. Symptoms are anxiety, hypersensitivity to bright light, insomnia, seizures, hydrophobia. The patient sees hallucinations, becomes aggressive.
Foot and mouth disease is a natural-focal disease that affects the mucous membranes, the peri-osseous bed and the folds between the fingers. The causative agent penetrates the body through food. The onset of foot and mouth disease is quite sharp, flowing with a sharp increase in temperature. The prognosis is often favorable, although children may experience serious complications.
Anthrax is a disease that has two forms: skin and septic. The cutaneous form is characterized by the appearance of numerous ulcers. This form develops rather slowly and can be treated well. The septic form is more dangerous, a lethal outcome can occur in just a few days.
Prevention of natural focal diseases
Pavlovsky's teaching about natural focal diseases had a huge impact on the approach to prevention. If initially the main measure of preventing epidemics was the treatment of infected people and the destruction of vectors, such as mosquitoes or ticks, then today the main goal is the elimination of animal reservoirs.
In order to protect oneself from natural focal diseases, it is important to observe a number of preventive measures: do vaccinations in a timely manner, do not visit the habitats of animals that carry disease pathogens, and protect oneself from the bites of insect vectors using closed clothing or by applying special repellents .