Cysticercosis

Cysticercosis, a disease caused by the parasitic invasion of tissues in animals and humans by one of the larval stages of tapeworms belonging to the order Cyclophyllidea, specifically the cysticercus or bladderworm. The latter represents a vesicular formation, on the inner wall of which a scolex buds off (in contrast to the cenurus and echinococcus, only one), floating in the fluid filling the bladder and being in an everted state. When careful pressure is applied to the cysticercus shell or when the latter enters a suitable environment (e.g., bile), the scolex everts outward.

Cysticercosis of humans is caused by the larva of the pork tapeworm (Taenia solium). However, there are isolated reports of the possibility of Cysticercus bovis parasitizing human tissues.

Figure 1. Cysticercus cellulosae with a scolex floating in the cysticercus, 2-with a scolex everted outward

stages of the beef tapeworm (Taenia rhynchus saginatus). In animals, C. of other species also occurs. C. in animals is often called finnose. C. in humans, caused by Cysticercus cellulosae, can be found in all parts of the globe; its distribution is linked to the distribution of pigs that suffer from C. and infect humans with teniasis, which in turn leads to C. in both humans and pigs (see Teniidosis). C. in humans was known as early as the 16th century. According to Berlin statistics, in the middle of the last century, cases of C. constituted 2% of all autopsies. With the introduction of veterinary control in city slaughterhouses, the number of cysticercotic corpses begins to fall and in 1901 amounts to 0.15% of all autopsies (Germany). However, precise statistics on C. in humans to this time do not exist. In patho-anatomical autopsies, the brain is not always examined, which is the organ of most frequent localization of cysticerci. Moreover, without the use of a special method of complete helminthological examinations (see Helminthological research methods), only the most intense cysticercus invasions are detected. Therefore, figures characterizing the spread of C. in humans based on conventional patho-anatomical methods are significantly lower than the actual ones. Within the USSR in recent years, thanks to improved research methods, C. of the eye is comparatively frequently diagnosed. Balabinina in her work 'Epidemic of cysticerci of the eye in Donbass' (Stalinsky district) describes 20 cases of C. of the eye that passed through the Yuzovskaya eye outpatient clinic. By 1930, Sadagov registers about 200 cases of C. of the eye, of which about 150 fall on the 20 years. C. of the brain, due to the awakened interest in this disease, is also described in the USSR in recent times comparatively often. C. of the skin has also been diagnosed in the USSR on multiple occasions, although much less frequently than C. of the eye or brain. In individual cases, cases of C. of the human heart, diaphragm, serous covering of the stomach, lung, etc. have been described in the USSR. For a cysticercus to form in the human body, it is necessary for the oncosphere of Taenia solium to enter the acidic environment of the stomach, then, after being freed from its shell, to penetrate the wall of the stomach or intestine, where it makes its way with the help of its hooks, and ultimately to enter the bloodstream. Being carried by the blood to one organ or another, the oncosphere penetrates from the capillaries into the tissues with the help of its hooks, where it undergoes a series of changes, as a result of which it turns into a cysticercus. The entry of the oncosphere into the stomach can occur in two ways: 1. The oncosphere enters the mouth with food products contaminated with excrement containing oncospheres of the pork tapeworm; or else through uncleanliness of a person infected with the pork tapeworm, they infect themselves or others (e.g. by handshaking, etc.). 2. The oncosphere enters the stomach without previously exiting into the external environment by being thrown back from the intestine with the help of antiperistaltic movements during vomiting, nausea, etc. The mature proglottids of the Pork tapeworm that may enter the stomach during this process, packed with eggs, are digested, the eggs are released, the shell of the eggs and oncospheres dissolves, and autoinvasion occurs. Thus, persons infected with Taenia solium are always under threat of C. This can be caused by accidental diseases accompanied by nausea or vomiting (seasickness during travel by sea or air, etc.). This can also be caused by nausea and vomiting during anesthesia, postoperative vomiting movements, insertion of duodenal or gastric probes, etc. The cysticercus is often enveloped in a connective tissue capsule due to the reaction of the host tissue. The structure of the capsule and changes in the adjacent tissue in C. of the brain differ depending on whether the parasite is alive or dead. In the first case, the capsule is narrow, consists mainly of elongated cells, and is almost imperceptible in places. The brain tissue, except for some compression, shows no special changes. The capsule of dead parasites is rich in cells, and a huge number of plasma cells are often observed in the outer layer. The glial tissue near a dead parasite is usually loosened, sometimes infiltrated with plasma cells. Endarteritis and infiltration of the perivascular spaces are observed, mainly with plasma cells. These changes sometimes reach a severe degree, giving a picture of encephalitis (Vinogradova, 1929) (Fig. 2). The size and shape of cysticerci depend to a large extent on the surrounding tissue, namely on the conditions of nutrition and on the degree of resistance offered by it to the growth of the cysticercus. Initially, the growing cysticercus has a round shape, which it usually retains in loose connective tissue. In muscles it is somewhat elongated. In some cases, a very peculiar growth of the cysticercus is noted at the base of the brain: the cysticercus flattens and elongates into long formations with constrictions, branches, grape-like protrusions, etc., sometimes reaching up to 25 cm in length (the so-called Cysticercus racemosus). In loose tissue (subcutaneous tissue, eye, brain), young cysticerci are capable of movement, which is confirmed by clinical observations (ophthalmoscopy). The number of cysticerci in one individual can reach several thousand. The localization is the most diverse, however Figure 2. most frequently C. is found in the eye and brain (thus, according to Vosgien, 800 cases of C. in humans were distributed by localization as follows: in 372 cases - eye or conjunctiva; in 330 - brain or spinal cord; in 51 - skin and connective tissue; in 28 - muscles, and in all other cases - other organs: heart, lungs, glands, bones, etc.). Infection of the fetus through the mother's body is also possible (Luppov). The lifespan of cysticerci averages 3-10 years, but cases of their existence for 15-17 years have also been described. Dead cysticerci are as a rule found in a state of calcification. The clinical picture of C. is extremely diverse, depending primarily on the localization of the parasite. C. of the eye usually leads to visual disturbances, often up to complete loss of vision. The clinical picture of C. of the brain depends on the intensity of the invasion and on the location of the cysticerci in the central nervous system. The actual clinical picture of C. of the brain has been studied rather poorly so far. The diagnosis was established in the vast majority of cases only at autopsy or on the operating table. However, in recent times, cerebral cysticercosis is sometimes recognized clinically. C. of the brain very often gives a characteristic picture of a brain tumor and can be diagnosed as a brain neoplasm (Shek-Novsep'yants, 1930). However, it can also give characteristic symptoms of epilepsy. Thus, Mac Arthur (1933) describes 22 cases of epilepsy observed in the Milbank Hospital, in 10 of which the etiological factor was C. of the brain. C. of the brain is very often associated with mental disorders. Chervakov repeatedly found C. of the brain in suicides. Localization of cysticerci in the brain ventricles can lead to sudden death. This can occur not only in a serious condition of the patient, but sometimes during a period of apparent health (cases of Shek-Novsep'yants, 1930). An extremely important diagnostic symptom of C. of the brain is the sharp fluctuations in the course of the disease with periods of very severe condition of patients and intervals between them of complete or almost complete health. These fluctuations are noted not only in the subjective condition of the patient, but also in the objective signs of the disease. Thus, even such a symptom as changes in the fundus of the eye can fluctuate sharply over a short period of time. A fairly significant sign in the diagnosis of C. of the brain is eosinophilia, which however can sometimes be absent. An even more valuable symptom is the presence of Taenia solium in the intestine and cysticerci in the subcutaneous tissue. However, the absence of teniasis or skin C. by no means argues against C. of the brain. In the vast majority of cases of C. of the brain, intestinal teniasis is not registered either in the present or in the past. Such cases partially have a different epidemiology, and partially teniasis is undoubtedly overlooked, as it often occurs without severe clinical manifestations. As for cysticercosis of the skin, the figures above show that it occurs much less frequently than C. of the brain. Shek-Novsep'yants points out that out of 124 cases of cerebral cysticercosis, only 12 were accompanied by skin C. (9.5%).

Cysticercosis of the brain (from the museum of helminthology of the All-Union Institute). Cysticercosis of the subcutaneous tissue does not give a severe clinical picture even with mass distribution of cysticerci throughout the body. In some cases, confusion of cutaneous C. with lipoma, atheroma, and other skin neoplasms is possible. However, upon excision of the cysticercus and its microscopic examination, the diagnosis presents no difficulties. With deep location of cysticerci under the skin or in the intermuscular layers of connective tissue, diagnosis by means of X-ray is possible only in cases of calcification of the cysticerci, and differentiation from calcified capsules of trichinae is quite easy based on the significantly smaller size of the latter. Clinical diagnosis of C. of the heart, diaphragm, and other internal organs at the present time does not seem possible. Surgical intervention, which often gives good results in C. of the eye, in C. of the brain should be considered as a palliative measure, since in the vast majority of cases C. of the brain is multiple. In addition to public prevention of C. (see Teniasis), mandatory therapy for intestinal teniasis is necessary.