Syphilis in animals. Conditions and ways of infection with syphilis

Long before the discovery of pale treponema, scientists made attempts to infect animals with syphilis. Now it is difficult to establish who was the first to do this, since the clinic in animals was not supported by the discovery of the pathogen.

II Mechnikov and Ru in 1903 successfully inoculated syphilis into two chimpanzees. The first experiments on infecting a rabbit in the eye are attributed to Jense (1881); Bertarelli (1906) infected a rabbit with syphilis by rubbing it into a scratch on the cornea of ​​the eye. In 1907, Parodi first infected a rabbit by introducing material from a syphilitic papule under the tunica vaginalis.
Currently, the rabbit is the main animal for experiments on obtaining experimental syphilis. Animals are infected with a suspension of pale treponema extracted from syphilitic manifestations by intratesticular injection (early orchitis), intradermally on the scrotum (receiving chancres), on the side into the clipped skin surface, by rubbing into the scarified skin surface or intradermally, into the anterior chamber of the eye, suboccipitally, into the brain.

After an incubation period (2-3 weeks), a small induration appears at the injection site of pale treponema, gradually increasing and acquiring a cartilaginous texture. In the center of it, necrosis and chancre are formed, covered with a small bloody crust. In the contents of the chancre, a huge number of treponemas are found. There are no inflammatory phenomena on the periphery of the chancre. After about 3-4 weeks, the chancre softens and the number of treponema decreases. Serological reactions become positive, their titer gradually increases.

Simultaneously with the chancre in a rabbit, regional lymph nodes the size of a pea are probed. 2.5-3 months after the formation of the chancre, the animal may experience secondary manifestations (papular, papular-crusty, rupiate-like rashes), in the contents of which pale treponemas are found. Roseola does not appear. The percentage of onset of secondary manifestations in rabbits is different. Most often, secondary manifestations are localized in the skin of the scrotum, limbs, roots of the ears, superciliary arches. For the secondary period of syphilis in rabbits, baldness is characteristic. There is also the development of parenchymal keratitis, the number of which varies depending on the season.

The manifestation of the tertiary period of syphilis is very rare. So far, there are no convincing data on damage to the nervous system. Involvement in the pathological process of the internal organs of rabbits is observed: aortitis, changes in the liver, etc. (L. S. Zenin, 1929; S. L. Gogaishis, 1935). There are isolated reports in the literature (P. S. Grigoriev, K. G. Yarysheva, 1928) about successful experiments in obtaining congenital syphilis from them. Sometimes, when infected with pale treponema, rabbits do not have any signs of the disease or there are no clinical manifestations if the pathogen is present in the lymph nodes or internal organs (such rabbits are called nullers - they have infectious immunity to syphilis).
On an experimental model of syphilis, the study of the therapeutic efficacy of drugs is being carried out.

In recent years, there have been reports that after immunization of rabbits with treponemal vaccines, it was possible to obtain protection from subsequent infection of these animals with a suspension of pathogenic treponema pallidum. However, these results were not confirmed by N. M. Ovchinnikov et al.

Pale treponema enters the human body through damaged skin or mucous membranes. Entrance gates can be so small that they go unnoticed. A patient with syphilis is contagious to others, especially with active manifestations of the infection. Pale treponemas can come to the surface with serous fluid from the depths of the tissues due to friction (when walking), friction (during sexual intercourse), irritation (mechanical or chemical), and also from the oral cavity if syphilitic papules are found there.

Currently, sexual contact should be recognized as the main route of infection with syphilis. Cases of domestic infection (through dishes, cigarettes, pipes, etc.) are rare. Extrasexual infection is possible if there are eroded syphilitic elements in the patient's mouth. Much less often, the discharge of syphilitic elements falls on household items, which become

no one in the transmission of infection (in a humid environment, treponemas remain viable for a long time outside the human body). Medical workers can become infected when examining a patient with syphilis or during medical procedures. Such cases were observed among midwives, surgeons, obstetrician-gynecologists, dentists, venereologists, laboratory workers who conducted research on pale treponema. To avoid such infection, it is necessary to work with gloves, monitor the integrity of the skin of the hands, and after examining the patient (especially with the infectious stage of syphilis), remove gloves, wipe your hands with a disinfectant solution and wash them with soap and water.

Very rare cases of infection with syphilis during direct transfusion (transfusion) of blood from a donor with syphilis. It is believed that the patient's saliva is contagious only if the patient has syphilitic elements in the oral cavity. It is suggested that human milk is contagious, even if there are no visible syphilitic changes in the area of ​​the nipple of the mammary gland. They also interpret the question of the contagiousness of sperm, in the absence of manifestations of the disease on the genitals of a patient with active syphilis. However, it is believed that the urine and sweat of patients with syphilis are not contagious. Transmission of infection from a sick mother to the fetus through the placenta is possible. As a result, congenital syphilis may develop.

For the development of syphilis, the amount of the pathogen introduced into the body of the experimental animal is also important. Apparently, this happens in humans in a similar way. In persons who have repeatedly had sexual contact with a patient with active syphilis, the possibility of infection is much higher than in those who have had a single and short-term sexual contact. In the blood serum of healthy people there are factors that immobilize pale treponema. Along with other factors, they help explain why contact with a sick person does not always lead to infection. Domestic syphilidologist M.V. Milic, based on his own data and analysis of the literature, believed that infection may not occur in 49-57% of cases.

Pathogenesis. The main routes of spread of pale treponema in the body are the lymphatic and circulatory systems. Pathological studies have shown that in the first days after infection, pale treponemas fill the lymphatic clefts and perivascular lymphatic spaces. Only after that they are found in the lumens of small blood vessels and their walls. Explanation

such tropism of pale treponema, which is a facultative anaerobe, is seen in a significantly lower oxygen content in the lymph compared to arterial and venous blood. Pale treponemas that have entered the body multiply intensively and spread in the lymph, where the oxygen content does not exceed 0.1%, while in the venous blood it is 100, and in the arterial - 200 times higher (8-12 and 20%, respectively) .

Along with the promotion of the lymphatic system, treponemas are carried with the blood flow to all organs and tissues. This is confirmed by the known cases of infection of recipients with the blood of donors who are in the incubation period of the disease.

In primary and in the first months of secondary syphilis, the spiral form of pale treponema predominates, and later it transforms into L-forms and cysts, which serves as a pathogenetic justification for the change of manifest periods of syphilis by latent ones. With a long stay in the patient's body of altered forms of pale treponema, the phenomenon of seroresistance is associated - the preservation of positive serological reactions after full treatment. Cysts that are not affected by penicillin have antigenic activity, so serological reactions remain positive as long as altered forms of pale treponema persist in the body.

The ability of cysts and L-forms to turn back into a virulent spiral form plays an important role in the pathogenesis of clinical and serological relapses of the disease after full treatment. In some patients, after the disappearance of clinical signs of syphilis and negativism of serological reactions, after a few months they suddenly become positive, and in some cases, clinical signs of infection reappear. Additional specific (antibiotics) and non-specific (pyrogenal, vitamins) therapy does not always give the desired results. Only after a few months, the titer of serological reactions may decrease spontaneously and without additional treatment. Positive serological tests in any case require specific treatment.

The immune system is activated when Treponema pallidum interacts with antigen-presenting cells: monocytic cells and Langerhans cells. Having captured the antigen, Langerhans cells pass into the mature stage, lose their processes and migrate to the lymph nodes and spleen, where they affect subpopulations.

T- and B-lymphocytes, enhance the presentation of CD4 antigens, keratinocytes and inflammatory infiltrate cells. In this case, suppression of the cellular link of immunity is observed.

Immunity. Superinfection. Reinfection. With a syphilitic infection, non-sterile (infectious) immunity is formed, which persists until the disappearance of treponema. Infection occurs in people with a deficiency of humoral and cellular immunity factors, low levels of treponemostatic and treponemocidal substances in the blood serum. Syphilis, according to the WHO classification, refers to diseases with immune failure. Cellular immunosuppression was established in the early stages of infection, a decrease in the number of T-lymphocytes in peripheral blood and T-dependent zones of lymphoid organs.

In the incubation period of syphilis, pale treponemas spread rapidly through the lymphogenous route. The reaction of the body in the form of primary syphiloma and regional scleradenitis is late. At the end of the primary and the beginning of the secondary period of syphilis, there is a mass reproduction of treponema and their spread throughout the body (treponemal sepsis). This is due to the development of general symptoms of the disease (fever, weakness, malaise, pain in the bones and joints, polyadenitis). As a result of the mobilization of immunobiological defense mechanisms, most of the treponemas die and a latent period of secondary syphilis sets in.

As the protective processes of the macroorganism weaken, treponemas multiply and cause a relapse (secondary recurrent syphilis). After that, defenses are again mobilized, and if left untreated, pale treponemas (possibly cysts) contribute to the persistence of a syphilitic infection. The undulating course of infection in the secondary period reflects the complex relationship of micro- and macroorganism.

In the secondary period, factors that suppress the proliferative function of lymphocytes are activated, the phagocytic activity of neutrophils decreases and their ability to form phagosomes increases. The synthesis of antibodies is activated, the concentration of serum immunoglobulins G, A and M increases. It is believed that at the beginning of syphilis, the level of serum IgG, IgM is higher, and in late forms only IgG remains. The antigen-antibody reaction specific for syphilis maintains an undulating, staging course of the disease, especially pronounced in the primary and secondary periods.

In the tertiary period of syphilis, when only a small amount of pale treponema remains in the tissues, high sensitization to treponema and their toxins manifests itself as a kind of anaphylactic reaction with necrosis and subsequent scarring. Since not only the manifestations of syphilis, but also the humoral-cellular factors of immune defense regress after the cure, a new infection is possible with repeated contact.

Re-infection is called reinfection. For the diagnosis of reinfection, a different location of the chancre is required than during the first infection, the presence of pale treponema in it and the appearance of regional scleradenitis. Reliability of reinfection is confirmed by sufficient treatment of the first infection and negative serological reactions after treatment. Take into account the existence of syphilitic infection in sexual contact. Reinfection is distinguished from superinfection - re-infection of an uncured patient. At the same time, a new portion of pale treponemas is added to the existing ones, so in different periods of the disease, superinfection manifests itself in different ways. So, in the incubation period and in the first 10-14 days of the primary period of syphilis, when infectious immunity has not yet formed, additional infection is manifested by the development of a new chancre. This chancre is smaller and occurs after a shortened incubation period (up to 10-15 days). Such chancres are called successive (ulcera indurata seccentu-aria). In other stages, during superinfection, the body responds to a new infection with rashes corresponding to the stage in which it was at the time of the arrival of a new "portion" of treponema. So, in the secondary period, a papule or pustule appears at the site of infection, in the tertiary period - a tubercle or gumma.

Classification of syphilis

The reaction of the body to the introduction and reproduction of pale treponema is manifested by a change in active, clinically pronounced periods of the disease and periods without manifestations on the skin and visible mucous membranes (the so-called latent, latent periods). The French syphilidologist Rikor drew attention to the regular change of periods in the "classical" course of syphilis. During syphilis, there are incubation, primary, secondary and tertiary periods.

In our country there is a single classification of syphilis. It is based on the stage of the disease in which the patient first sought medical help.

The following is the division of syphilis according to the International Classification of Diseases of the 10th revision. The ICD is based on the etiology, anatomical localization, circumstances of the onset of the disease with a diagnostic description of local manifestations, complications, and the main disease processes. To obtain reliable statistical data, their centralized processing, especially with the help of computers, analysis of the epidemiological situation, and an adequate assessment of the effectiveness of treatment methods, it seems appropriate to use a single terminology.

Since 1999, the ICD has replaced all other classifications of diseases in Russia.

Long before the discovery of pale treponema, scientists made attempts to infect animals with syphilis. Now it is difficult to establish who was the first to do this, since the clinic in animals was not supported by the discovery of the pathogen. II Mechnikov and Ru in 1903 successfully inoculated syphilis into two chimpanzees. The first experiments on infecting a rabbit in the eye are attributed to Jense (1881); Bertarelli (1906) infected a rabbit with syphilis by rubbing it into a scratch on the cornea of ​​the eye. In 1907, Parodi first infected a rabbit by introducing material from a syphilitic papule under the tunica vaginalis.

Currently the rabbit is the main animal for experiments for experimental syphilis. Animals are infected with a suspension of pale treponema extracted from syphilitic manifestations by intratesticular injection (early orchitis), intradermally on the scrotum (receiving chancres), on the side into the clipped skin surface, by rubbing into the scarified skin surface or intradermally, into the anterior chamber of the eye, suboccipitally, into the brain.

After the incubation period (2-3 weeks) at the injection site of pale treponema a small compaction appears, gradually increasing and acquiring a cartilaginous consistency. In the center of it, necrosis and chancre are formed, covered with a small bloody crust. In the contents of the chancre, a huge number of treponemas are found. There are no inflammatory phenomena on the periphery of the chancre. After about 3-4 weeks, the chancre softens and the number of treponema decreases. Serological reactions become positive, their titer gradually increases.

Simultaneously with the chancre in a rabbit, r regional lymph nodes pea-sized. In 2.5-3 months after the formation of the chancre, the animal may experience secondary manifestations (papular, papular-crusty, rupe-like rashes), in the contents of which pale treponemas are found. Roseola does not appear. The percentage of onset of secondary manifestations in rabbits is different. Most often, secondary manifestations are localized in the skin of the scrotum, limbs, roots of the ears, superciliary arches. For the secondary period of syphilis in rabbits, baldness is characteristic. There is also the development of parenchymal keratitis, the number of which varies depending on the season.

The manifestation of the Tertiary period syphilis is very rare. So far, there are no convincing data on damage to the nervous system. Involvement in the pathological process of the internal organs of rabbits is observed: aortitis, liver changes, etc. (L. S. Zenin, 1929; S. L. Rogaishis, 1935).

There are isolated reports in the literature (P. S. Grigoriev, K. G. Yarysheva, 1928) about successful experiments in obtaining from them congenital syphilis. Sometimes, when infected with pale treponema, rabbits do not have any signs of the disease or there are no clinical manifestations if the pathogen is present in the lymph nodes or internal organs (such rabbits are called nullers - they have infectious immunity to syphilis).

On the experimental model of syphilis study of the therapeutic efficacy of drugs.

Speaking about whether syphilis occurs in animals, one should separate natural conditions and intentional infection of animals with a disease - the so-called experimental syphilis. If in ordinary, natural life the disease practically does not occur in representatives of the fauna, then in laboratory conditions it was still possible to achieve certain results. Such studies were carried out so that scientists inventing various drugs designed to defeat syphilis were able to test them and track exactly how they affect the causative agent of the disease.

Among the known animals, not all were able to be infected with experimental syphilis, moreover, until the beginning of the last century, it was believed that they could not get syphilis, since not a single vaccination could provoke the disease. To date, the research results are as follows:

• Rabbits - successfully experimented, today they are widely used in scientific research related to this disease;
• Monkeys - despite the fact that they managed to instill experimental syphilis, it gave little for scientific research, because for some unknown reason, primates immediately develop symptoms of the secondary period, bypassing the primary stage;
• It was possible to instill syphilis in animals familiar to laboratory research - mice. However, even here there are certain difficulties, because, despite the obvious presence of the disease in the body of the animal, confirmed by the analyzes, no external manifestations of it are observed. This complicates the process of drug testing because it does not give a complete picture of its action.

In no other animal species, syphilis vaccinations have shown any pattern in the outcome. Such experiments made it possible to improve the already invented drugs and find new ones, because only empirically it was possible to establish exactly how the drug will affect the disease. It was these studies that also made it possible to establish the fact that spirochete pallidum can be found in the lymph long before the first symptoms of the disease appear.

However, not a single animal study can be considered completely finished, and before applying the obtained data to humans, it is necessary to take into account many nuances and make the necessary amendments so that instead of benefit, more harm is not done.