What is Diphyllobothriasis?
Diphyllobotriasis (Bothriocephalosis) is a helminthiasis that occurs with signs of predominant damage to the gastrointestinal tract and often accompanied by the development of megaloblastic anemia.
A characteristic feature of diphyllobothriasis is confined to areas of cold and temperate climate, the prevailing distribution in the countries of the northern hemisphere.
Even in the last century, major foci of diphyllobothriasis existed in Sweden, Finland, Northern France, Switzerland, Holland, Belgium, Denmark, Romania, Italy and Germany, then endemic foci were identified in the Great Lakes region of North America, Canada, Chile, and Japan.
The first information Zander about the spread of diphyllobothriasis in Karelia refer to 1894. According to modern concepts, in Russia, diphyllobothriasis is widespread in the northern regions of Karelia, on the Kola Peninsula, the Desna, Northern Dvina, Pechora, Ob, Yenisei, Lena, Amur river basins, in the Pribaikalye, the Volga region, and in the Baltic States.
In Ukraine, foci of diphyllobothriasis exist in the Danube Delta, as well as in the Kremenchug and Kakhovka reservoirs, created on the Dnieper. In Moldova, isolated cases of diphyllobotriosis are recorded in the lower Prut and Dniester.
Causes of Diphyllobothriasis
Diphyllobotriasis pathogens belong to the order Pseudophylidea and consist of 12 types of tapeworms, of which the wide tapeworm (Diphyllobothrium latum) is the most common and studied (Unney, 1758, Lube, 1910).
The length of the strobila, consisting of a large number of segments (up to 4000), reaches 2-9 m. The scolex, 3-5 mm long, has an oblong-oval shape, flattened from the sides, on the lateral surfaces – two slits (bothria), through which the parasite is attached to intestinal mucosa. The eggs of the tapeworm are wide-oval, large (70 x 45 microns), with a double-circuit shell, have a lid on one pole, and on another pole a lid. Parasitizing in the organs of the final host, the Lentets release immature eggs, which develop in freshwater bodies of water. The embryo (coracidium) forming in the egg enters the water after 6-16 days. At temperatures below + 150C, coracidia do not leave eggs, remaining viable for up to 6 months. After swallowing coracidia with freshwater crustaceans, after 2-3 weeks they turn into procercoids. In the organism of fish, swallowing crustaceans, the procercoids penetrate into the internal organs and muscles, where in 3-4 weeks they develop into plerocercoids up to 4 cm long and having a formed scolex. In sexually mature lentez, plerocercoids are transformed in the organism of the final host.
Pathogenesis during Diphyllobothriasis
The life cycle of a broad tapeworm.
The development of Lentets occurs with the change of three owners.
Eggs that have fallen into the external environment remain viable for up to 30 days, but continue their development only when they fall into the water. Under favorable conditions (water temperature – 20 ° С, oxygen content not less than 1.5-2.0 mg / l) after 3 weeks coracidia develops in the egg, which, squeezing the cap out, goes into the water. Coracidia has a spherical shape, is provided with three pairs of hooks and a ciliary cover, actively swims in water. The life span of coracid in water, depending on water temperature, is 1–12 days. For further development during this time, it must be swallowed up by the first intermediate host – various types of copepods of the order Copepoda, genera Eudiaptomus, Acanthodiaptomus, Diapthomus (D. gracilis, D. graciloides), Cyclops (C. strenuus, C. insignis, C. serrulatus ). In the intestines of these crustaceans, the coracidia lose ciliary cover and penetrate with the help of hooks into the body cavity, where after 2-3 weeks they turn into the second larval stage — procercoids, representing an elongated larva 0.5–0.7 mm long, equipped at the rear end of the body three pairs of germinal hooks.
Crustaceans containing invasive larvae are swallowed by the second intermediate (additional) hosts – various predatory fish: ruff, perch, pike burbot, pike perch, whitefish, omul, etc. liver and other internal organs of fish. Here they continue their development and within 4-5 weeks reach the last stage of larval development, the plerocercoid. By this time the plerocercoids reach 1-3, less often 5 cm, at their front end two slit-like bothria are visible. Plerocercoids are invasive for the final host. The life cycle of a wide tape-reader can be complicated. When eating small fish (with plerocercoids) by large predatory fish, the plerocercoids are not digested from them, but are preserved in their tissues.
When consumed by humans or carnivorous animals — the final owners (dogs, cats, leopard, otter, seal, walrus, etc.) of such fish, the plerocercoids, entering the digestive tract, attach themselves to the mucous membrane of the upper part of the small intestine and in 2-4 weeks reach the stage mature individuals.
In the intestines of a person usually lives one, rarely several lentets, but described the cases of parasitism of 100 or more individuals. The life span of the parasite is calculated in years – 10, 20 or more years. At the same time, periodically a part of the end portion of the strobila is rejected and in the form of a tape is excreted with feces during defecation.
In the development of the clinical manifestations of the disease, the mechanical effect of helminths on the intestinal wall at the site of its attachment with the development of atrophy and necrosis plays a role; stimulation of interoreceptors with the formation of viscero-visceral reflex reactions and neuro-trophic disorders; allergic reactions due to the sensitization of the host organism with metabolic products of the tapeworm; endogenous hypovitaminosis of cyanoblaminum and folic acid, resulting from impaired absorption and synthesis by the macroorganism and competition for them from the side of the helminth. Depending on the conditions for the formation of foci, classifications were singled out according to the stages of their formation (potential, exogenous, endogenous), according to the level of infestation of the population, the composition of the hosts (natural, anthropic, mixed type), the density of copepods, etc.
The factors contributing to the spread of invasion include, first of all, natural and climatic conditions:
- the presence of a fresh water body (if the content is above 9% salt in the water, the eggs die, the coracidia released settle to the bottom);
- 02 content in water is not lower than 10 -12 mg/l;
- shallow water, well warmed by the sun;
- high number of crustaceans -1000 – 3000 and more per 1 m3 of water.
The sanitary condition of the reservoir, the conditions contributing to its pollution, as well as the dietary habits of the population are of decisive importance.
The final owners of diphyllobothriasis can be humans and different types of domestic and wild animals: a dog, rarely a cat, an otter, a leopard, white and brown bears, a walrus seal, etc.
However, the main source of invasion is an invasive person, which is due to the long-term parasitism of the helminth and the intensive release of eggs with feces — over 2 million per day.
The eggs of the lazers at a temperature not higher than 10 ° С remain viable in water for at least 2 years. In the soil on the surface they die on the 3rd day, in cesspools up to 14 days are stored. Water temperatures above 20 ° C have a detrimental effect on coracidia, which is one of the reasons for the lack of local diphyllobotriosis in countries with a hot climate. The larvae also quickly die in salt water.
The mechanism of infection is oral. Infection occurs by eating insufficiently roasted or boiled, and sometimes raw fish, freshly salted caviar, and tapeworm infested with plerocercoids.
Infection is possible in cases of cutting fish through hands, knives, and dishes that were affected by plerocercoids.
The food habit common in some places — fish on the “horn,” fish shashlik, raw pike caviar freshly prepared with spices — promote infection with diphyllobothriasis.
Plerocercoids have a moderate degree of resistance; they die at low temperatures of -15 ° C in 24 hours, – 10 ° C – 3 days, – 4 – 6 ° C in 5 – 9 days.
High temperatures are more reliable: the survival threshold of the plerocercoid is protein coagulation zone +50 – + 55 ° С.
When the salt content in the finished product 8 – 9% plerocercoids die.
Symptoms of Diphyllobotriosis
The incubation period is from 20 to 60 days. Diphyllobotriasis can have both clinically manifest and latent course. The disease begins gradually. There is nausea, less often – vomiting, pain in the epigastrium or throughout the abdomen, decreased appetite, stool becomes unstable, subfebrile appears. In cases of a long course of helminthiasis, obstructive intestinal obstruction may occur in some patients due to the accumulation of a large number of helminths in the small intestine. In parallel, signs of astheno-neurotic syndrome (weakness, fatigue, dizziness) and B12-deficiency anemia appear and grow. There are pain and paresthesias in the tongue, in severe cases, Henter’s glossitis is observed – the presence of bright red, painful spots and cracks in the tongue. Later, the nipples of the tongue atrophy, it becomes smooth, shiny (“lacquered”). There is tachycardia, expansion of the borders of the heart, soft systolic murmur at the apex, top noise, hypotension. The number of erythrocytes and hemoglobin is sharply reduced, the color indicator remains high, there is an increase in indirect serum bilirubin, relative lymphocytosis and neutropenia, accelerated ESR. With fresh invasion, eosinophilia can be detected. Megaloblasts, Joly bodies, Cabot rings, hyperchromic macrocytes, polychromatophilic erythrocytes and erythrocytes with basophilic granularity are found in a small amount in a blood smear. In some patients, the number of red blood cells and the amount of hemoglobin remain within the normal range, but there are signs of macrocytosis (shift of the Price-Jones curve to the right). The severity of anemia depends on the nature of food and living conditions. In severe course of the disease, the funicular myelosis develops: unsharp paresthesias, disturbances of superficial and deep sensitivity.
Diagnosis of Diphyllobotriosis
In the diagnosis informative epidamnus (stay in an endemic area, eating raw fish, under-salted caviar). Often patients report excretion of parts of worms with feces. Diphyllobotriasis is characterized by the release of fragments of strobila, which distinguishes it from invasion by chains (bovine and porcine). The differential diagnosis between difillobotrioz and Addison-Birmer anemia is possible on the basis of the definition of Castle factor in the stomach contents, which is absent in pernicious anemia. The final diagnosis is established when the helminth eggs are found in the feces.
In case of severe anemia, prior to deworming (expelling worms), vitamin B12 (Cyanocobalamin) is prescribed 200-500 micrograms intramuscularly 2-3 times a week for a month, as well as iron preparations: Ferronate, Ferronal, Hemofer, Aktiferrin, Ferroplekt, Hematogen, etc. .
For expelling of helminths, fenasal, extract of male fern, decoction from pumpkin seeds is used.
Pumpkin seeds are taken for 1 hour inside on an empty stomach in bed – 300 g of raw or pre-dried seeds, pounded in a small amount of water with the addition of honey.
The prognosis in the absence of complications is favorable.
When planning and executing work on the prevention of diphyllobothriasis, it is necessary to carry out a number of measures involving the impact, on the one hand, on the source of invasion, and on the other, on the mechanism of its transmission. Neutralization of the source of invasion is achieved by routinely identifying all persons affected by diphyllobothriasis in existing and possible foci, by specifically treating them, disinfecting the excreta and parasites excreted in the process, followed by clinical examination of the treated ones. People are regularly examined for this invasion according to clinical indications, in addition, fishermen before the spring and autumn Putin and the crew of riverboats before and after navigation. Diphyllobotriasis and deworming are also systematically carried out in the places where new water bodies, reservoirs are created and in the settlements where this invasion has been eliminated. In the existing and possible foci of diphyllobothriasis, attention should be paid to measures to free dogs, cats and other animals from this invasion, which may be additional sources of invasion.
To break the transmission mechanism, a number of measures are taken to prevent the contamination of the external environment, especially water bodies, with wide-spread eggs and exclude the use of fish products, raw fish and its caviar that are not neutralized from plerocercoids. In this connection, the issue of proper treatment of the patient, sanitary control over the discharge of sewage into reservoirs near residential areas (industrial and domestic) and sewage from various types of vessels, the sanitary condition of beaches and shores located near the places of residence or production is of particular importance. activities of people (especially fishermen, navigation personnel of river vessels and workers in the fishing industry), in the preparation of fish products, by-products, dishes and their sale.
Sanitary-educational work among residents of endemic areas and high-risk groups: the fish processing industry, the crew, should be aimed at preventing possible contamination.
When cooking fish dishes, spread portions of fish, minced meat, cutlets and small fish are recommended to be cooked for at least 15 – 20 minutes, and unspawned portions of large fish – no longer than 30 – 40 minutes. In the case of fish salting in a strong brine, the death of plerocercoids occurs in 8–10 days. You can disinfect the fish by freezing to a solid state, raw fish can not be tried during culinary processing.