Biology of human parasites. Parasites definition in biology What is a parasite in biology

The real ones that are actually in another organism are excreted in its feces where they can be found (house fly larvae);

False (imaginary), which can accidentally get into the feces, brought, for example, for analysis (flies can lay eggs on them, and larvae quickly hatch from them).

1. Depending on the number of likely hosts:

Evriksenny (from the Greek.ωύρύω - wide) - those that have a wide range of hosts (ixodid ticks, mosquitoes);

heteroxenni (from the Greek.έτερος - different, different) - those that go through complex development cycles due to several owners. Yes, dog tick. passes three stages of development: larva, nymph, imago - and at each stage it has its own host.

Temporary - those that live outside the host's body and attack him only to feed on blood (ticks, fleas, mosquitoes, mosquitoes) lasting from half a minute to several days;

Permanent - live in the host's body or on its covers at all stages of development.

3. Depending on the location:

External - live on the outer covers of the host (lice, fleas, mosquitoes);

Skin - live in the thickness of the skin, and partly on its surface (scabies verbun);

Cavitary - live in cavities that communicate with the external environment - in the external auditory canal, in the nasal cavity (wolfart fly larvae).

Cavitary - live in the body cavities of internal organs (ascaris, gostrik);

Tissue - in muscle, nervous tissues (trichinela);

Internally (sporozoans, flagellates).

Living beings in nature react to each other and enter into relationships in many ways. One such type of communication between two organisms is commensalism, or parasiticism. Examples of such relationships in nature are quite common. Let's consider the most striking of them.

Definition of freeloading (commensalism)

Relationships formed between organisms that interact in nature can be symbiotic in nature. One type of symbiosis is called freeloading, where one organism benefits from the relationship while the other species is neither benefited nor harmed. In total, there are four areas of benefit:

Nutrition.
Housing.
Transportation.
Seed dispersal.

Types of commensalism

Most environmental experts group commensal relationships into the following types:

Chemical commensalism is most commonly seen between two species of bacteria, one of which feeds on the chemicals or waste products of the other.
Inquilinism - One animal uses the body or body cavity of another organism as a refuge or living space.
Entoikia is a form of commensalism that occurs when one species inadvertently creates a home inside another's cavity, but has an outlet to the outside environment.
Phoresia occurs when one organism attaches itself to another organism for the purpose of transportation.
Sinoikia (lodging) occurs when one living being uses another being or its dwelling as its home.

Freeloading examples

Commensalism is a scientific term that characterizes the relationship between two living creatures from different species, in which one of the organisms benefits for itself, while the other, as they say, is neither hot nor cold. Often commensalism occurs between a large animal and a smaller one. Here are some examples of cheating:

Some shells cannot move on their own and attach themselves to certain inhabitants of the sea, such as whales. The former benefit from being able to transport across the ocean. The latter receive neither benefit nor harm from this connection.
The white heron follows herds of cattle and feeds on the insects that pursue them.
The monarch butterfly extracts the poisonous chemical from the spurge plant and stores it in its body to protect itself from predators.
The remora fish and the shark are a good example of commensalism.

The term "commensalism"

Commensalism is the scientific term for the notion of freeloading. In terms of time, this type of relationship can be quite short, or it can look like a lifelong symbiosis. The term was coined in 1876 by the Belgian paleontologist and zoologist Pierre-Joseph van Beneden, who originally applied the word to describe the activities of accompanying animals that followed predators to eat their prey. The word "commensalism" comes from the Latin word commensalis, which means "separation, at the same table" (com - together, mensa - meal).

Examples of freeloading are very common. Wood frogs use plants as protection. Jackals expelled from the pack will follow the tiger to get hold of the remnants of his meal. Small fish live on other marine animals, changing color to blend in with the host, thus gaining protection from predators.

Burdock produces spiky seeds that cling to animal fur or human clothing. Plants rely on this method of seed dispersal to reproduce, while animals are unaffected.

Freeloading: examples of animals and plants

Also, commensalistic relationships are those in which one organism forms a habitat for another. An example of freeloading in this case is a hermit crab - here a shell from a dead gastropod is used for protection. Another example would be larvae living on a dead organism.

An animal is attached to another for transportation. This type of commensalism is most common in arthropods such as insect-eating mites. Other examples include the anemone attachment to the shells of hermit crabs, mammal-dwelling pseudoscorpions, and bird-traveling centipedes.

Commensal organisms can form communities within the host organism. An example of such freeloading is the bacterial flora found on human skin. Scientists debate whether the microbiota is truly a type of commensalism. For example, in the case of skin flora, there is evidence that bacteria confer some protection on the host (which would be reciprocated).

Pets and commensalism

Dogs, cats, and other animals also seem to have commensal relationships with humans. It is believed that the ancestors of dogs followed hunters to eat the remains of carcasses. Over time, the "cooperation" became mutual, with humans also taking advantage of the relationship to gain protection from other predators and help track prey.

Marine "freeloaders"

Examples of parasiticism in nature are relations between individuals of two species, in which one species receives food or other benefits from the other without harming or benefiting the latter. A pilot fish swims alongside a great white shark. Thanks to the flat oval sucking disk structure at the top of the head, the remora fish sticks to its host's body. Both of these freeloader fish feed on the remnants of their owners' food. One of the best-known examples of commensalism in the ocean is the relationship that exists between clones and sea anemones.

Examples of paraphernalia in biology clearly show between organisms, which is beneficial for one of them, and neutral for the other. Many cases of commensalism are surrounded by controversy, as there is always the possibility that the commensal host also benefits or is harmed in a way as yet unknown to science.

Relations of this type are of great importance in nature, as they contribute to closer cooperation between species, more efficient development of space and enrichment of the diversity of food resources.

Forming cysts, amoebas leave the human body with undigested food residues. Light cysts spread easily. If you do not wash your hands and food, then they can become infected.

Malarial Plasmodium

If a malaria patient is bitten again by a malarial mosquito, then now the plasmodia will get from the person to the mosquito. In the body of a mosquito, Plasmodium reproduces sexually.

Malaria is common in Africa. This is a very dangerous disease. Malaria is fought, including by destroying malarial mosquitoes.

Trypanosomes

The carrier of sleeping sickness is the tsetse fly. This disease is typical for tropical Africa. Sleeping sickness develops in two stages: in the first weeks a person is tormented by fever and pain, after a month or more, drowsiness, sleep disturbance and coordination, and a change in consciousness occur. The disease is easier to treat in the first stage.

lamblia

A person becomes infected with giardiasis by eating unwashed food containing giardia cysts. Leaving the cyst, lamblia sticks to the intestines and feeds on digested food.

Leishmania

There are different types of leishmaniasis associated with damage to various tissues of the body. One of them is the skin disease Pendin's ulcer.

coccidia

Coccidia belong to the genus Toxoplasma. Their representatives cause such a widespread disease in humans as toxoplasmosis. A person becomes infected from pets or poorly cooked meat food. Toxoplasma affects many organs, including the nervous system.

Depending on the localization, they are divided as follows:

Sapronoses;

It is most convenient to distribute individual infectious diseases according to their epidemiological characteristics. This makes it possible to characterize the routes of infection transmission and the associated mechanism of human infection.

The causative agents of infectious diseases can enter the human body in various ways:

a) through the gastrointestinal tract (intestinal infections);

b) through the upper respiratory tract (respiratory tract infections);

d) through the outer integument (skin and mucous membranes).

The modern classification was proposed by Academician of the Russian Academy of Medical Sciences V.I. Pokrovsky (2003), which, depending on the natural habitat of pathogens, divides all infections into three groups.

Anthroponoses - the habitat of pathogens is the human body. These diseases are peculiar only to humans and are transmitted from person to person;

Zoonoses (from the Greek Zun - animals.) - the habitat is the body of animals.

All infectious diseases according to the etiological principle, i.e. according to the affinity of pathogens, they are divided into viral infections, mycoplasmosis, rickettsiosis, bacteriosis, spirochetosis, mycosis, protozoosis, helminthiasis.

The opinion was expressed that among the existing ecological and epidemiological classifications of infectious diseases, the most rational is the classification of B.L. Cherkassky, which reflects both the specifics of the reservoir of pathogens and the features of the transmission of pathogenic microorganisms to humans from these reservoirs. A refined ecological and epidemiological classification of infectious diseases is proposed, providing for the differentiation of infections into classes according to the main reservoir of the pathogen (anthroponoses, zoonoses, sapronoses), and within them into groups according to the leading mechanism of pathogen transmission (human infection) and localization of the pathogen in the human body (fecal- oral, or intestinal, aerosol, or respiratory, transmissible, or blood, contact, or integument). The proposal on the expediency of dividing sapronoses into soil, water and zoophilic ones was taken into account. Taking into account modern scientific data, the list of sapronose infections has been expanded.

40. An integrated approach to the implementation of preventive and anti-epidemic measures aimed at three links of the epidemic process, highlighting the leading link.

41. Measures aimed at the pathogen reservoir in the host organism: clinical diagnostic, isolation, therapeutic and regime-restrictive measures for anthroponoses, as well as sanitary, veterinary and deratization measures for zoonoses.

A significant role is played by preventive measures aimed at the source of infection, in which, in anthroponotic diseases, a person is a patient or a carrier of pathogens, and in zoonotic diseases, an animal.

This group of preventive measures for anthroponoses includes diagnostic, isolation, therapeutic and regime-restrictive measures. Active and complete detection of patients is carried out on the basis of complex diagnostics, including clinical, anamnestic laboratory and instrumental studies. With a number of infections (especially dangerous infections, typhoid fever, viral hepatitis, etc.), hospitalization of identified patients is mandatory. In other nosological forms (dysentery, escherichiosis, measles, chicken pox, etc.), in the absence of epidemiological and clinical contraindications, isolation of patients at home is allowed.

42. Measures aimed at breaking the transmission mechanism of the pathogen: sanitary-hygienic, disinfection and pest control measures.

Anti-epidemic measures can be defined as a set of recommendations that are justified at this stage in the development of science, ensuring the prevention of infectious diseases among certain groups of the population,

reduction in the incidence of the total population and the elimination of individual infections. Anti-epidemic measures are carried out in the event of the occurrence (detection) of an infectious disease, preventive measures are carried out constantly, regardless of the presence or absence of an infectious patient.

The basis for the prevention of infectious diseases on a national scale is the increase in the material well-being of the people, the provision of the population with comfortable housing, qualified and affordable medical care, the development of culture, etc.

Medical aspects of infectious disease prevention include

systematic sanitary control over the water supply of the population; sanitary

and bacteriological control of food quality, sanitary

state of food industry enterprises and public facilities

food, trade and children's institutions; planned

disinfection, disinfestation and deratization measures

Preventive measures aimed at breaking the transmission mechanism of the pathogen are divided into 3 groups:

1. Sanitary and hygienic measures;

2. Disinfection measures;

3. Disinsection measures.

At intestinal infections of the fecal-oral mechanism of infection, when the infection is transmitted through food and water (less often through dirty hands), general sanitary and hygienic measures are of the greatest importance, as well as various methods of disinfection, which is carried out in foci of infectious diseases, in public places, regardless of the presence outbreaks during epidemics.

At respiratory tract infections carrying out measures to stop the transmission of the pathogen is associated with serious difficulties. Preventive measures for respiratory infections are the sanitation of indoor air, the use of respirators. Disinfection is carried out with scarlet fever, diphtheria - with other respiratory tract infections, disinfection is practically not used, due to the instability of pathogens in the external environment: measles, chickenpox, rubella, mumps.

At vector-borne infections An important role in prevention is played by means of disinsection for the destruction of carriers of pathogens - blood-sucking insects.

43. Measures aimed at preventing diseases in case of infection with pathogens of infectious diseases: planned and emergency immunoprophylaxis.

Emergency immunoprophylaxis is carried out in cases where contact with a source of infection is expected. Unlike routine vaccination, it can be carried out not constantly, but according to epidemic indications, i.e. if the epidemic situation for some infectious disease has worsened in the area. For example, in connection with the influenza epidemic. Such vaccination is usually carried out by decision of the territorial executive authorities and in advance (2-3 months in advance).

Also, emergency immunoprophylaxis is carried out in case of suspected infection after contact of a healthy person with a sick person (post-exposure prophylaxis). Unscheduled prophylaxis is necessary in the event of circumstances that may contribute to the occurrence of diseases, such as injury, burns or a bite from a wild animal.

In contrast to routine immunization, which uses antigenic preparations (vaccines and toxoids), emergency prevention of certain infectious diseases requires rapid protection, the so-called passive artificial immunity. It is created through the use of immune sera and immunoglobulins. For example, for emergency prevention of tetanus or rabies, a person is given anti-tetanus or anti-rabies (against rabies) gamma globulin. For the prevention of measles, rubella, scarlet fever, meningitis, human normal immunoglobulin is used, which contains antibodies against pathogens of many infectious diseases.

The most common diseases are:

Causes

The cause of the disease is T. Solium (pork tapeworm). People become infected by eating improperly cooked pork. Lack of hygiene is also risky.

If a person swallows an egg, larvae are released in the stomach and duodenum, which enter the bloodstream through the intestinal wall and spread throughout the body. In the place where the larva is attached (for example, in the muscles or in the human brain), it turns into a cysticercus, which matures within 2-3 months and lives for several years.

Diagnostics

Treatment

In the case of ophthalmic cysticercosis, surgical removal of the cysticercosis can be used.

Manifestations

Symptoms of the disease vary depending on the localization of cysticerci in the body. Neurocysticercosis, in which cysticerci are found in the human brain and spinal cord, has the following symptoms:

epileptic seizures;
intracranial hypertension (increased intracranial pressure);
mental disorders.

Toxoplasmosis of the brain - neurotoxoplasmosis

Treatment

Toxoplasmosis in immunocompetent (with an intact immune system) and non-pregnant women does not require specific treatment. As an alternative, symptomatic therapy is chosen (relief of individual symptoms - such as pain, fever, etc.). In certain cases, drugs of the antiprotozoal group are introduced - in particular, Pyrimethamine, it is possible to combine it with Sulfadiazine (a group of sulfanilamide chemotherapy drugs). In rare cases, a decision is made to surgically remove the localization or abscess.

Manifestations

Symptoms of cerebral toxoplasmosis are quite diverse and include the following types:

epileptic seizures;
intracranial hypertension;
headache;
vomiting/nausea;
anxiety;
apathy or irritability;
disturbance of consciousness;
focal neurological symptoms (impaired speech, walking, sensations, feelings);
paralysis of cranial nerves;
hemiparesis (paralysis of a limb on one side);
mental disorders;
mental changes (slow reaction, changes in behavior, personality disorders);
visual impairment.

Some experts suggest a connection between the latent form of Toxoplasma and the effect of T. gondii on the human nervous system, for example:

changes in the production of brain hormones;
schizophrenia;
increased irritability and aggressiveness;
cerebral allergy symptoms;
increased sexual activity while reducing the social and emotional depth of relationships (superficial relationships);
increased selfishness and resentment;
decrease in social intelligence (disorders in the field of communication, lack of social tact);
decreased sense of self-preservation;
phobias of subjectively or objectively dangerous places and situations;
an increase in the likelihood of traffic accidents.

Elevated levels of testosterone, dopamine, inflammatory markers, and other brain responses to toxoplasmosis can also increase an affected individual's aggression or trigger schizophrenia if predisposed.

However, other studies have not shown an association between the risk of motor vehicle accidents, schizophrenia, violent and non-violent behavioral changes, suicide attempts, decreased response and short-term memory, and other symptoms with toxoplasmosis. The results of many subsequent studies were also mostly negative.

Echinococcosis

cystic echinococcosis (caused by E. granulosus);
alveolar echinococcosis (caused by E. multilocularis).

There are 2 less common forms - polycystic and cystic echinococcosis.

The disease has a relatively long incubation period. Signs depend on the location and size of the cysts. Alveolar disease usually starts in the liver, but can spread to other parts of the body, such as the lungs or brain.

Forecast

Manifestations

Signs of the disease in many ways resemble those of brain cancer and include the following symptoms:

dizziness;
cephalgia;
epileptic seizures;
intracranial pressure.

Diagnostics

Cysts are displayed using ultrasound or CT. ELISA can also be used to detect antibodies and antigens.

According to doctors, the mortality rate during infection is more than 98%.

Initially, the person suffers from fever, nausea, vomiting, neck stiffness, and headache. Death occurs within 5-7 days. The disease does not spread from person to person.

Helminths

Cystidicola farionis

Trienophorus nodulosus

Diphyllobotrium latum

thoroughly clean the fish;
cut into pieces of 1 cm;
boil for 30-40 minutes.

For salting infected fish, it is necessary to withstand it for 10-12 days at low temperatures, and then insist 7-8 days at room temperature in a saline solution. Salt must be added in an amount of at least 3 parts by weight of the fish. Careful preparation and handling of infected fish does not guarantee that infestation will not occur. That is why, in order to exclude the development of serious diseases, infected fish meat should not be included in your diet.

Russian cuisine does not have dishes with raw fish. But in this case, one should not forget about the herring. This type of product is quite popular due to its taste and low cost. Not every manufacturer complies with the technology for making herring, therefore, infection with the use of this product is not completely excluded.

Among the dangerous helminthic invasions, one can single out an ink-spotted disease that infects fish that contain the causative agent of postodiplostomiasis in their bodies. This disease is not very dangerous, but experts recommend refraining from eating fish, on the body of which there are dark spots.

How to distinguish infected fish

An unusable product has certain differences, knowing which you can protect yourself from infection:

Infected fish have damaged muscle structures. When pressed, the resulting hole is not leveled.
The pupils of the fish are cloudy, and the mucous membrane is usually dry.
The belly of the fish is sagging and swollen.
The gills acquire a characteristic swampy hue, while the internal organs of the fish have a fetid odor during cutting.
The anus protrudes above the main body of the fish and a viscous cloudy mucus flows out of it.

When cooking infected fish, the broth has quite specific characteristics. The decoction is usually cloudy. There is no fatty film on its surface. Instead, the broth contains a mass of dark particles and flakes of unknown origin.

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