Alveococcus

Alveococcus is the larva of a parasitic worm (multi-chambered echinococcus) and causes the dangerous disease alveococcosis, which in terms of severity, complexity of treatment and real threat of death is compared to cirrhosis and liver cancer.

For Ukraine, this type of helminthiasis is quite rare, but you can catch this parasite in Europe, America, and Central Asia, which are endemic areas for it. So information about what alveococcus is will not be superfluous.

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Structure of alveococcus

Alveococcus is a type of the helminth echinococcus, which is widespread throughout the world, and belongs to the order of tapeworms (cyclophyllids) of the class of cestodes (parasitic flatworms). The size of an adult female capable of reproduction is no more than 3-3.2 mm in length. This cestode parasitizes the small intestine of carnivores, in particular, canines (foxes, arctic foxes, wolves, jackals, dogs), as well as wild mouse-like rodents.

The structure of the alveococcus, that is, the structure of its body in a mature state, includes a head (scolex), a neck, and several segments. The body (strobilus) is covered with special cells that absorb food from the host's intestines. On the head are chitinous hooks, which are the organs of attachment. Next comes the neck - the growth zone of the worm, and behind it are segments (proglottids). Tapeworms have a hermaphroditic reproductive system, and each segment has one.

The last segment of the alveococcus, which functions as a sexual organ, contains a uterus filled with eggs. The uterus has no exit hole, so the eggs are laid as follows: the segment, together with the uterus, breaks away from the body, gets into the excrement of the host animal and is carried outside. There, the segment breaks and scatters the eggs. After this, the next proglottid replaces the one that has separated, since the nematode's body can be restored by forming new segments.

Each egg contains a larval embryo (oncosphere), also equipped with hooks. Alveococcus eggs have increased resistance to adverse environmental conditions and can survive at any temperature.

It should be noted that the alveococcus (multi-chambered echinococcus), like all invertebrates, has an orthogonal nervous system consisting of several pairs of longitudinal cords, tactile and receptor cells in the skin and a paired ganglion (nerve node), which is located in the scolex.

Life cycle of alveococcus

The life cycle of the alveococcus is the stages of development of the organism of one individual, which changes its host - intermediate and main. In the main (final) host - predatory mammals, including dogs - the adult parasite lives in the intestine. The eggs of the alveococcus enter the intermediate host (rodents, cattle and small cattle, humans) (through the esophagus - with water or food). And here in the tissues of the body, cavities and organs a new stage of development begins - the larval (larvocyst stage).

The entire life cycle of the alveococcus proceeds strictly in accordance with the stages and has the following phases:

• first stage: in the intestines of the definitive host, adult individuals live and reproduce, forming eggs;
• the second stage: the eggs reach the required condition and are “laid” by being released outside the body of the main host;
• third stage: embryos (oncospheres) are finally formed in the eggs, which are completely ready for the second larval phase, which must take place in a new host - the intermediate one;
• fourth stage: the eggs enter the body of the intermediate host and turn into larvae.

Let's take a closer look at how this happens when alveococcus eggs enter the human body. Once in the stomach and intestines, the embryo-larva emerges from the egg and, with the help of its hooks, penetrates the wall directly into the bloodstream and gets to any point with the blood. Most often, the liver becomes the "location site" of the parasite, much less often - the lungs or other internal organs.

In the liver, the larva begins its main larval stage, during which a multi-chambered bubble, the larvocyst, is formed in the tissues of the human organ. Inside each small bubble that makes up the larvocyst, there is liquid and the embryonic head of the parasite, and in it the final maturation of the bladder larva will take place and the structure of the alveococcus will be formed.

In this case, larvocysts behave quite aggressively: they grow into liver tissue and constantly grow due to an increase in the number of bubbles. Necrosis of the liver parenchyma occurs around them, capillaries are damaged and stop functioning. Intensive growth of the colony of alveococcus larvae can spread to nearby structures, leading to the formation of fibrous nodes with the inclusion of larval bubbles.

All this can last for several years, resembling the metastasis of a cancerous tumor.