Parasites in the body

Human parasites are organisms that live on or in the human body and obtain nutrients and protection at the expense of the host. These organisms can range from microscopic protozoa and helminths (worms) to larger arthropods. Parasites have different life cycles and transmission routes and can affect different organs and systems of the body.

Single-celled parasites (protozoa) and multicellular parasites (helminths, arthropods) are antigenically and biochemically complex, as are their life histories and the pathogenesis of the diseases they cause. Over the course of their lives, parasitic organisms usually go through several developmental stages, which are accompanied by changes not only in structure, but also in biochemical and antigenic composition. Some larval stages of helminths bear little resemblance to the adult stages (e. g. tapeworms and flukes). Some protozoan parasites also change significantly over the course of their lives; For example, Toxoplasma gondii is an intestinal coccidia in cats, but in humans it takes a different form and is localized in deep tissues.

Some of these infections can progress from a well-tolerated or asymptomatic state to a life-threatening disease. Many parasitic infections are transmitted from animals to humans (zoonic infections).

Protozoan parasites

Protozoa are microscopic single-celled organisms that can be free-living or parasitic in nature. Transmission of protozoa living in the human intestine to another person usually occurs via the fecal-oral route (e. g. , through contaminated food or water or through person-to-person contact). Protozoa that live in human blood or tissue are transmitted to other people through arthropod vectors (e. g. , through the bite of a mosquito or midge fly).

Human protozoan parasites can be divided into four groups depending on their mode of locomotion.

1. Sarcodidae: Use pseudopodia for movement. These include the amoebas Entamoeba (dysenteric liver abscess), Dientamoeba (colitis), and Acanthamoeba (can cause a serious, often fatal infection of the brain and spinal cord called granulomatous encephalitis).
2. Flagellates (sarcomastigophores): Use flagella for locomotion. These include Giardia (diarrhea), Trypanosoma (sleeping sickness and Chagas disease), leishmania (visceral, cutaneous and mucocutaneous leishmaniasis), and trichomoniasis, a sexually transmitted infection (STI).
3. Apical complexes: The apical complex is used for movement. These include Plasmodium (malaria) and Toxoplasma (a zoonotic infection caused by the parasite Toxoplasma gondii with a variety of clinical syndromes in humans).
4. Ciliates: These move by cilia and include Balanidium, a large protozoan, the only known ciliated animal to infect humans (dysentery). About 1% of the world's population is infected with balantidiasis.

Helminths

Helminths are large multicellular organisms that are usually visible to the naked eye in the adult stage. Helminths can be either free-living or parasitic in nature. In their adult form, helminths cannot reproduce in the human body. There are three main groups of helminths that are human parasites:

• Trematodes: Fasciola hepatica – liver fluke; Fasciolopsis buski – intestinal fluke; Paragonimus_westermani – lung fluke; Schistosoma is a leech.
• Cestodes (tapeworms): Diphyllobothrium Latum – broad tapeworm; Hymenolepis Nana – dwarf tapeworm; Taenia Saginata – beef tapeworm; Taenia solium – pork tapeworm.
• Nematodes (roundworms) cause various diseases in humans that can affect the intestines or directly attack certain tissues. Ascaris
• Lumbricoides – giant roundworm; Enterobius Vermcularis – pinworms and others.

Ectoparasites

These are organisms that live externally on the skin of their hosts. Skin parasites feed on blood and epidermis. They are usually so small that you cannot see them. Some species burrow into the skin, others live on the surface. Some parasites can spend their entire life cycle inside the human body, but many live outside the body and only feed occasionally.

• Cimex Lectularius is a common parasite known as a bed bug.
• Dermatobia hominis is the larva of the human horsefly.
• Sarcoptes scabiei is a mite that causes scabies.

Human parasites affect millions of people around the world, particularly in regions with limited access to clean water, sanitation and healthcare.

Causes of pathology

• Contaminated food and water. Poorly treated or contaminated water sources can contain parasites such as Giardia lamblia and Cryptosporidium, which lead to gastrointestinal infections. Consuming undercooked or contaminated foods, especially raw or undercooked meat and seafood, can lead to the transmission of parasites such as Toxoplasma gondii and Trichinella spiralis.
• Poor hygiene and sanitation. Many parasitic infections, particularly those caused by helminths (e. g. , roundworms, hookworms), are transmitted through contact with fecal-contaminated soil, food, or water.
• Vector transmission by insect vectors. Parasites such as Plasmodium (malaria), Trypanosoma (Chagas disease, African sleeping sickness) and nematodes (causing lymphatic filariasis) are transmitted through the bites of infected insects: mosquitoes, bedbugs and midges.
• Animal-to-human transmission: Some parasites are reservoirs in animals, and humans can become infected through direct contact with infected animals or their feces. For example, Toxoplasma gondii can be transmitted through contact with cat feces.
• Imported infections. People traveling to regions where certain parasites are endemic may be at risk of contracting infections not normally found in their country.
• Person-to-person transmission. Some parasites in the body, particularly intestinal parasites such as Enterobius vermcularis (pinworms) and Giardia lamblia, can be transmitted from person to person through direct contact, often in crowded conditions or shared accommodation.
• Contaminated soil: Some species of helminths, including nematodes, can infect humans through contact with contaminated soil that contains eggs or larvae of parasites.

Symptoms of the disease

Depending on the type of parasite in the human body, the location of the infection and the severity of the infestation, helminthiasis can manifest itself in various symptoms:

• Abdominal pain, cramps and discomfort.
• Nausea and vomiting.
• Diarrhea or constipation.
• Weight loss and malnutrition.
• Anemia due to loss of blood and nutrients.
• Visible worms in the stool.
• Perianal itching (a pinworm infection (Enterobius vermcularis) can cause perianal itching in children, especially at night).
• Respiratory symptoms: Some worms, such as: B. Ascaris lumbricoides, can migrate into the respiratory tract and cause symptoms such as coughing and wheezing.
• High temperature: In some cases, helminth infections can cause a low-grade fever.
• Infection with some liver flukes or tapeworms can cause enlargement of the liver (hepatomegaly) or spleen (splenomegaly).

Protozoa (protozoan parasites) most commonly cause diarrhea. Excessive diarrhea can lead to dehydration, a condition particularly common in children under 5 years old. Toxins released by the pathogen and entering the bloodstream cause weakness, pain in the abdomen and muscles. If the infection becomes chronic, weight loss and skin rashes occur.

Diagnosis of the disease

Diagnosis of parasitic infections requires a combination of clinical examination, laboratory tests for parasites, and sometimes imaging studies.

A detailed medical history, including information about travel to other countries, exposure to contaminated water or food, and symptoms, helps healthcare providers narrow down possible parasitic infections. A physical exam can reveal signs and symptoms associated with infections, such as: B. Skin rash, tenderness in the abdomen or enlarged organs.

Microscopic examination of stool samples is a common method for identifying intestinal parasites, including helminths (worms) and protozoa. If enterobiasis is suspected, a smear from the perianal area is prescribed, which is then examined under a microscope. Blood tests for parasites can be used to detect antibodies, antigens, or DNA from parasites.

• To diagnose echinococcosis, serological tests and sometimes an ultrasound scan of the liver are prescribed.
• Diagnosis of opisthorchiasis is made through stool examinations and serological tests, sometimes through DNA testing.
• Toxocariasis can be detected by tests to detect antibodies to Toxocara, a DNA test for parasites and a general blood test that shows eosinophilia.
• Giardiasis is diagnosed using stool analysis and serological tests.
• To diagnose ascariasis, stool microscopy and tests for antibodies to Ascaris are used.
• Trichinosis: Serological tests and DNA analysis of trichinella.

Urine samples can be tested for the presence of eggs, larvae, or antigens of parasites, particularly in infections such as schistosomiasis.

Radiological imaging such as ultrasound, computed tomography or MRI can visualize and assess the extent of tissue damage caused by certain parasites, particularly cystic or tissue-infiltrating parasites.

Treatment

Treatment of parasitic infections usually involves the use of antiparasitic medications. The specific medications and duration of treatment depend on the type of infection causing the infection, its severity, and the organs affected. Metronidazole and tinidazole are active against a variety of protozoa, including Entamoeba histolytica and Giardialamlia. Atovaquone-Proguanil: Used to treat and prevent malaria and some protozoan infections. Anthelmintics include albendazole, praziquantel, ivermectin, pyrantel pamoate, sulfadiazine, and suramin.

Prognosis and prevention of the disease

The prognosis for treating parasites in the body varies greatly and depends on several factors, including the type of parasite, the severity of the infection, the organ systems affected, and the person's general health. In many cases, prompt and proper treatment can lead to a favorable outcome, while lack of treatment or serious infections can lead to complications and long-term health consequences.

The human immune system plays an important role in determining the outcome of a parasitic infection. Immunocompetent people may have a better prognosis than people with weakened immune systems.

The development of complications such as organ damage, chronic inflammation or secondary infections can significantly influence the prognosis. Complications can arise from long-term or untreated infections.

Some parasitic infections can become chronic and persist for a long period of time. Chronic infections can cause ongoing health problems and can be difficult to treat.

The involvement of critical organ systems such as the nervous, cardiovascular or respiratory systems can have a significant impact on the prognosis. Parasites that attack vital organs can cause more serious and life-threatening complications.

To prevent parasitic infections, various measures must be taken to reduce the risk of infection and transmission. General recommendations for preventing parasite infestation are:

• Wash your hands thoroughly with soap and water after using the toilet, before eating, and after touching pets or soil.
• Keep your nails short and clean to minimize the risk of parasite eggs or cysts getting under your nails.
• Cook meat, fish and poultry thoroughly to kill parasites. Wash fruits and vegetables thoroughly, especially if they are eaten raw.
• Drink clean drinking water from purified or boiled sources, especially when traveling to areas where there is a high risk of waterborne parasites.
• Use insect repellent to prevent bites from mosquitoes, ticks and other vectors that can transmit parasitic diseases.
• Make sure your pets receive regular veterinary checkups and deworming medications.
• Dispose of pet waste properly to minimize the risk of pest infestation.