An organism that lives in a more or less closeassociation with another organism of adifferent species (the host), derivessustenance from it and is pathogenic to thehost, although this potential is not alwaysexpress ed. protozoa (unicellular organisms and metazoa,including helminths (parasitic ―worms,‖) Numerous diseases (parasitoses) in human,e.g. malaria
eukaryotic, single-celled microorganisms 1–150 lm in size. enclosed by a trilaminated cell membrane. They possess one, rarely two nuclei (andmultinuclear reproductive forms). Reproduction is asexual by binary or multiplefission of the cell, or sexual
Parasite of the small intestine of humans thatcan cause enteritis. Infection occurs by peroral ingestion ofGiardia cysts. Various species of mammaliananimals are reservoir hosts.
Giardia exists in two morphological forms: amotile vegetative stage, the trophozoites, anda cyst stage. The trophozoites live on the small intestinemucosa. Pear split lengthwise, are 9–21 lm long and5–12 lm wide and possess eight flagella, twonuclei one on each side. Reproduction is by means of longitudinalbinary fission of the trophozoites
G. intestinalis produces oval cysts (8 –18 ! 7–10 lm) with four nuclei, flagella, and Has claw-shaped median bodies. The cysts (and, less frequently, trophozoites)are excreted in stool
In the small intestine, G. intestinalis cancause inflammation as well as othermorphological changes and malabsorption. Gallbladder infections. Patients with symptomatic infectionsexperience chronic and recurrent diarrhea, steatorrhea, and signs of malabsorption aswell as upper abdominal pains, vomiting,occasionally fever, and weight loss.
The standard diagnostic method is stool. Examination using the SAFC technique to detectcysts ELISA kits are now also available to detectGiardia-specific structural and soluble antigensin stool samples. Nitroimidazole compounds are used forchemotherapy of infections, For instance Metronidazole, Ornidazole, andtinidazole as well as the Benzimidazolecompound Albendazole The recently introduced nitazoxanide(nitrothiazole compound).
Transmitted mainly by sexual intercourse. It causes vaginitis in women and urethritis inmen.
Pear-shaped protozoon about 10–20lm longand 2–14 lm wide. Trichomonads are anaerobic protozoa that possess hydrogenosomes, which arespecialized organelles producing Hydrogen asa metabolite. T. vaginalis colonizes the mucosa of theurogenital tract and reproduces bylongitudinal binary fission. Trichomonads donot encyst
Humans are the sole reservoir of T. vaginalis.The parasites are transmitted Mainly during sexual intercourse. About 2–17% of female neonates born of infectedmothers contract a perinatal infection.
T. vaginalis primarily colonizes the vaginalmucosa, more rarely that of the cervix. The infection results in production of apurulent, thin, yellowish discharge in whichTrichomonads, pus cells, and bacteria arefound. The parasites also enter the urethra in about75–90% of cases, where they can also causean inflammation, but only rarely infect theurinary bladder or uterus.
A fresh specimen of vaginal or urethral secretionis mixed with physiological saline solution andexamined under a microscope for trichomonads,recognized by their typical tumbling movements. Also identified in smear preparations followingGiemsa staining or in an immunofluorescencetest with Monoclonal antibodies. The most reliable diagnostic results are obtainedBy culturing specimens in special liquid media. Other special methods are based on detection ofantigen (ELISA ) or DNA (PCR)
It is always necessary for both sexualpartners to receive treatment. EffectiveNitroimidazole In women vaginal application—includemetronidazole, tinidazole and ornidazole. These substances are contraindicated in earlypregnancy.
Trypanosoma brucei gambiense andTrypanosoma brucei rhodesiense causeAfrican trypanosomosis (sleeping sickness) In humans, which presents interalia as feverand meningoencephalitis The trypanosomes are transmitted by thebites of tsetse flies (Glossina). Trypanosomatidae multiply by longitudinalbinary fission
Giemsa staining of a blood smearpreparation.
Important diagnostic tools include directdetection of the trypanosomes in the blood,lymph node aspirate and, in cerebral forms, inthe cerebrospinal fluid. Trypanosomes can be detected in native bloodpreparations, in Giemsa-stained Since low level parasitemias are often present,concentration methods may be required, e.g.,micro-hematocrit centrifugation, anion exchange chromatograph y, or the QBC techniques, Othermethods are cultivation and mouse inoculationtests
Sleeping sickness in initial stage one isafebrile glandular condition withlymphadenopathy and hemolymphatic stage Meningoencephalitic condition follows assecond stage of infection. In stage one trypanosomes multiply in tissuefluids and at inoculation sites. Second stage involves invasion of centralnervous system.
The activation of kallikrein, kinin, complement,and the coagulation system by circulatingimmune complexes. This resulting in increased vascular permeability,edema, hemostasis, tissue hypoxia, tissuedamage, disseminated intravasal coagulation The trypanosomes cause CD8+ T cells andmacrophages to produce IFN c and TNF. IFN c stimulates trypanosomes to multiply. TNF contributes to immunosuppression and mayinitiate tissue damage.
In stage one, T. gambiense infections aremainly treated with pentamidine, T. rhodesiense infections are treated withsuramin. This drugs are no effective in the secondstage prompting the use of arsenic cpdmelarsoprol, a relatively toxic substance. Eflornithine is used for treating the late stageof the T. gambiense infection.
Causative agent of leishmanosis. Leishmania parasitize in mononuclearphagocytic cells (macrophages, monocytes,Langerhans cells) in the amastigote form.