Parasitology

• Malarial parasites have a complex life cycle that involves two hosts - a mosquito as the secondary host and a human host.
• The nucleus of Entamoeba coli has an eccentric nucleolus.
• The life cycle of Entamoeba coli is the same as in Entamoeba histolytica except that it remains a luminal cyst without tissue invasion and is nonpathogenic.
• The cyst of Entamoeba coli has eight nuclei.
• Entamoeba coli has a cyst membrane.
• Phagocytosed bacteria are found in the nucleus of Entamoeba coli.
• Parasites are generally larger or more complex than bacteria, limiting the efficiency of immunological attack on the protective antigens.
• Selective tests for immunoglobulin M (IgM) are helpful in differentiating current infections from old infections.
• This type of immunity to reinfection is dependent on the continued presence of residual parasite population and is known as "premunition".
• Once the parasitic infection is completely eliminated, the host becomes susceptible to reinfection.
• Immunological protection against parasitic infections is much less effective than against bacterial or viral infections.
• Excessive IgE response occurs in helminth infections, particularly in helminthic cysts.
• Parasites have evolved to be closely adapted to the host and most parasitic infections are chronic and show a degree of host specificity.
• Many protozoa and helminths live inside body cavities, protecting them from immunological attack.
• Antibodies belonging to different immunoglobulin classes are produced in response to parasitic infections.
• Parasites, like other infectious agents, can infect both humans and animals, causing diseases in the host.
• Cysts and ropes of E. histolytica, C. albicans can be demonstrated in feces.
• An appropriate clinical spectrum should be collected for definitive diagnosis of parasitic infections.
• Parasite escape mechanisms include intracellular habitat, resistance to microbial phagocytosis, masking of antigens, variation of antigen, suppression of immune response, and sharing of antigens between parasite and host molecular mimicry.
• Stool examination is important for the detection of intestinal infections like Giardia, Enlameoba, Ascaris, Ancylostoma, etc.
• Following specimens are usually examined to establish a diagnosis of parasitic infections: stool, urine, sputum, cerebrospinal fluid (CSF), tissue and aspirates.
• Vaccination is not effective against human parasites due to their complex life cycles, adaptive responses, and antigen variation.
• Eggs of roundworm and tapeworm are also found in stool.
• Laboratory diagnosis of parasitic infections depends on microscopy, culture, serological tests, molecular methods, imaging, and histology.
• Most parasitic infections cannot be conclusively diagnosed in the laboratory.
• The larvae of parasites are found in the feces.
• Clinical diseases caused by flagellates include Giardia lamblia, which causes diarrhea, and Trichomonas vaginalis, which can produce vaginitis and urethritis.
• Visitors to such places frequently develop traveler's diarrhea caused by giardiasis through contaminated water.
• Habitats of group-living flagellates include duodenum and jejunum, vagina and urethra, mouth, large intestine (cecum), large intestine (colon), large intestine (cecum and colon), reticuloendothelial cells, connective tissue and blood, and GIARD/A LAMBLIA.
• Giardia lamblia exists in two forms: Trophozoite (or vegetative form) and Cyst (or cystic form).
• Group-living flagellates include Giardia lamblia, Trichomonas vaginalis, Trichomonas tenax, Trichomonas hominis, Chilomastix mesnili, Enteromonas hominis, Retortamonas intestinalis, Dientamoeba fragilis.
• Giardia lamblia is one of the highest recorded protozoan parasites and is worldwide in distribution.
• Giardia lamblia lives in the duodenum and upper jejunum and is the only protozoan parasite found in the lumen of the human small intestine.
• Endemicity of Giardia lamblia is very high in areas with low sanitation, especially in the tropics and subtropics.
• Most of the protozoa are completely nonpathogenic but a few may cause major diseases such as malaria, leishmaniasis and sleeping sickness.
• Out of 10,000 species of parasitic protozoa, man harbours only about 70 species.
• The typical protozoan cell is bounded by a trilaminar unit membrane, supported by a sheath of contractile fibrils enabling the cell to move and change in shape.
• Protozoa are eukaryotic microorganisms belonging to the kingdom Protista, which are classified as Protozoa (Greek protos: first; zoon: animal).
• The single protozoa cell performs all functions.
• The cytoplasm of a protozoa has two portions: Ectoplasm, the outer homogeneous part that serves as the organ for locomotion and for engulfment of food by producing pseudopodia, and Endoplasm, the inner granular portion of cytoplasm that contains nucleus.