The following points highlight the top two genus of class mastigophora (flagellate). The genus are: 1. Trypanosoma 2. Leishmania.
Class Mastigophora: Genus # 1. Trypanosoma:
Trypanosome, blood flagellate protozoon, is an elongated spindle shaped body with tapering ends. Its nucleus is central and anterior to kinetoplast. The undulating membrane is proceeding forward as free flagellum (Fig. 106.1).
Human pathogenic trypanosomes are:
1. T. brucei — rhodesiense – gambiense group (Human strain) T. rhodesiense (Fig. 106.2) and T. gambiense (Fig. 106.3) causes African trypanosomiasis.
2. T. cruzi (Fig. 106.4) causes South American trypanosomiasis (Chagas disease).
T. gambiense occurs in 3 forms (long, short and intermediate) in blood lymph node, CSF.
Life Cycle of Trypanosoma:
T. gambiense multiply in the blood of man (definite host). After ingestion by intermediate host (tsetse fly, Glossina palpalis), they reproduce in the lumen of the fly and migrate back to salivary gland (anterior station development). These metacyclic infective forms are introduced into man by the bite of the fly.
Clinical features of Trypanosoma:
An elevated painful “trypanosomal chancre” at the site of bite. After trypanosomal invasion, lymph nodes, spleen, liver are enlarged. If the CNS is invaded, sleeping sickness develops with severe headache, mental dullness and apathy and the sleepiness becomes pronounced and finally death ensues.
In the laboratory (A) Trypanosome can be demonstrated microscopically in:
1. Peripheral blood;
2. Lymph aspirate;
3. Bone marrow smear and
4. CSF.
(B) Cultivation in media.
(C) Animal inoculation.
Serology of Trypanosoma:
Gel precipitation test, indirect fluorescent antibody test (IFAT). CFT, ELISA. Besides, ELISA and capillary passive haemagglutination (HA), a Card agglutination test (CATT) has been recently introduced. It is simple, specific and sensitive.
Treatment of Trypanosoma:
Melarsoprol and Berenil are current drugs.
Trypanosoma Cruzi:
It is a pleomorphic trypanosome, occurs in human blood as typical trypanosome (Fig. 106.1) and in reticuloendothelial cells and tissue as Leishmania. In vectors as Leishmanial (Fig.106.5) Crithidia (Fig. 106.6) and metacyclic trypanosome. It can be cultivated on Novy MacNeal and Nicolle (NNN) medium (Fig. 106.7—Leptomonas).
Life Cycle:
Reduviid bug (Triotoma infestans) ingests trypanosomes while biting infected man. In its stomach, they transform into amastigote, (Fig. 106.5), promastigote (Fig. 106.8) epimastigote (Fig. 106.9) and metacyclic forms which are excreted with its faeces (Posterior station development).
These infective metacyclic trypanosomes (Fig. 106.10) are rubbed into the scratches made by bug, invade the subcutaneous tissue, transform into amastigote, promastigote and trypomastigote forms which are liberated in the circulation. Thus, the cycle is repeated.
Clinical features:
In the skin, primary lesion (Chagoma) blocks the lymphatic’s and produces oedema. Chagas disease may be acute or chronic. In acute form, there is high fever, swollen face and oedema of eyelids (Romana’s sign) and keratitis. In chronic form, there is cardiac rhythm disturbance, cardiomyopathy, paraplegia, spastic paralysis.
Laboratory diagnosis:
(a) By demonstration of T. cruzi in blood and tissue;
(b) Xenodiagnoses,
(c) Antibody by CFT; G-agglutination test is very recent method; ELISA is specific and sensitive. The gelatin particle indirect agglutination test is simpler, sensitive, recent test.
Treatment:
Few mg. of Azardirachtine (a substance of neem tree seed) is a very current drug which blocks the reproduction of T. cruzi.
Class Mastigophora: Genus # 2. Leishmania:
Three species of Leishmania:
(1) L. donovani causes kala-azar,
(2) L. tropica – Oriental sore; L. braziliensis – Mucocutaneous leishmaniasis.
Morphology: L. donovani has two stages:
1. Leishmania (amastigote);
2. Leptomonas in sand fly, and in culture.
Leishmania is an ovoidal body (2, 3 microns), intracellular in the monocytes and polymorphonuclear leucocytes of man. In blood smear stained by Giemsa stain, its cytoplasm is pale blue and the nucleus is red, parabasal body is red. The kinetoplast is at tip. Leptomonas is long slender and spindle shaped, (15 µ 1.5 µ) motile with single flagellum and grows on NNN medium.
Life cycle of Leishmania:
The sand fly (Phlebotomus argentipes) draws the circulating leishmania and parasitized macrophages during its blood meal. In its intestine, Leishmania transform into leptomonas which multiply and are found in its buccal cavity (anterior station development). The transmission to man is effected by the bite of the infected sand fly.
Leptomonas engulfed by reticuloendothelial cells, multiply intracellularly by binary fission into leishmania until the parasitized macrophages are destroyed. Free leishmania and parasitized macrophages enter into the circulation. Thus, the cycle is repeated.
Clinical features of Leishmania:
The incubation period is 2-4 months. The symptoms are malaise, headache, fever, splenomegaly and abdominal pain, oedema of the skin, emaciation of chest, dysentery and diarrhoea, bleeding from gums and cachexia. The skin is dry, rough, darkened. Death due to complications.
Laboratory diagnosis of Leishmania:
1. Direct method to demonstrate L. donovani in blood smear, culture and biopsy of lymph node and sternal puncture. Polymerase Chain Reaction (PCR) can detect L. donovani in impression smear.
II. Indirect method, blood count, old serology — Aldehyde test, Antimony test and CFT. Recent serological techniques — IF AT, CIEF and ELISA and Direct agglutination test (DAT). IF AT is very sensitive; ELISA is specific, sensitive and most practical test. As compared to ELISA and IF AT, DAT is most recent technique and is found to be most specific sensitive and easy to perform and economical.
Treatment of Leishmania:
Ketoconazole is effective against L. donovani. Amphotericin B intravenously is very effective to multidrug (sodium stibogluconate, allopurinol plus ketoconazole and pent-amide iso-thionate) resistant L. donovani and is extremely effective relapse-free.
Leishmania Tropica:
(Causes Delhi boil or Oriental sore)
In its morphology and life cycle. It is similar to L. donovani but it does not invade the viscera.
Clinical features:
The incubation period is several months. Lesion on the skin (reddish papule, ulcer with raised edge), Symptoms are fever, chills and inflammation.
Laboratory diagnosis:
Microscopic examination of stained smear from the sore will reveal L. tropic but blood smear will not. Montenegro reaction (skin test) can also be done.
Leishmania braziliensis:
Its morphology, life cycle and laboratory diagnosis are similar to that of L. donovani and L. tropica.
Clinical features:
Ulcer in the mucous membrane of the mouth, and hard and soft palate. Symptoms are fever, anaemia, pain and malaise.
Giardia intestinalis (Fig. 106.14, 15, 16 — see in page 497) (See also page 484 under intestinal protozoa)
Genus:
Trichomonas has been classified according to their habitats into :
(1) Trichomonas hominis — lleo — caecal region (Fig. 106.11)
(2) Trichomonas tenax — Oral cavity (Fig. 106.12)
(3) Trichomonas vaginalis — Vagina and urinary tract (Fig. 106.13)
Trichomonas Vaginalis:
History:
Donne (1836) observed this species in female and male genital organs.
Habitat:
This flagellate is mostly found in human vagina and prostate gland.
Morphology:
It exists only in trophozoite stage (Fig. 106.13). It is considerably larger (13 microns), its undulating membrane is shorter and its cytostome is much less conspicuous.
Biology and Life cycle:
In the female, this parasite feeds on the mucosal surface of the vagina, ingesting bacteria and leucocytes. It grows in the more acid condition than that of the healthy vagina. The infected female is the reservoir of T. vaginalis and the infection is acquired by male in extra-marital intercourse.
Pathogenicity and Clinical Features:
T. vaginalis causes degeneration and desquamation of the vaginal epithelium, followed by leucocytic inflammation of the tissue layer. Very large numbers of trichomonads and leucocytes are now present in the vaginal discharge which is greenish or yellow. The vaginal secretions diagnosis can be found in centrifuged urine and vaginal secretion.