L3 :Balantidium coli

L3:Balantidium coli
Trophozoites
Considered as the largest protozoan known to humans, the typical Balantidium coli trophozoite my measure from 28 ?m to 152 ?m in length, with an average length of 35 to 50 ?m. The average trophozoite width is approximately 40 ?m but may range from 22 ?m to 123 ?m. The ovoid to sac – shaped. B. coli trophozoite tapers at the anterior end. The organism typically exhibits rotary, boring motility. The trophozoite contains two nuclei. The micronucleus is located adjacent to the macronucleus. The micronucleus is often not readily visible, whereas the macronucleus may often appear as a hyaline mass, especially in unstained preparations. Two contractile vacuoles are located in the granular cytoplasm. In addition, the cytoplasm may also contain food vacuoles, as well as ingested microbes (bacteria). The trophozoite is equipped with a small cytosome. A layer of cilia surrounds the organism, which serves as its means of locomotion.





Table ( ) : Balantidium coli trophozoite : Typical characteristics
28 to 152 ?m in length
22 to 123 ?m wide Size range
Rotary, boring Motility
Two : Kidney shaped macronucleus
Small spherical micronucleus Number of nuclei
One to two visible contractile vacuoles
may contain bacteria
Small cytosome present
Layer of cilia around organism Other features



Cyst

Averaging in size from 52 ?m, the subspherical to oval. B. coli cyst may measure from 43 ?m to 66 ?m. Although the cyst technically contains both the macronucleus and micronucleus, the micronucleus may not be observed in wet or permanent preparations. One or two contractile vacuoles may be visible, particularly in young unstained cysts. A double – protective cyst wall surrounds the organism. A row of cilia may be visible between the two cyst wall layers in unstained young cysts. Mature cysts tend to lose their cilia. Stained cysts typically reveal only the macronucleus, the other structures are not usually apparent.






Table ( ) : Balantidium coli cyst : Typical characteristics
43 to 66 ?m. Size range
Two : Kidney shaped macronucleus, usually present and small, spherical micronucleus, may not be observable Number of nuclei
One to two visible contractile vacuoles in young cysts
Double cyst wall
Row of cilia visible in between cyst wall layers of young cysts Other features


Life cycle

Human infection with B. coli is initiated upon ingestion of infective cysts in contaminated food or water . unlike that of E. histolytica , multiplication of the B. coli nuclei does not occur in the cyst phase . following excystation in the small intestine , the resulting trophozoites take up residence and feed primarily in the cecal region and terminal portion of the ileum, as well as in the lumen, mucosa, and submucosa of the large intestine. The multiplication of each trophozoite occurs by transverse binary fission, from which two young trophozoites emerge. The B. coli trophozoites are delicate and do not survive in the outside environment. Encystation occurs in the lumen. The resulting cysts mature and ultimately become the infective form for transmission into a new host. These cysts may survive for weeks in the outside environment.





Clinical symptoms

Balantidiasis. Symptomatic patients may experience a variety of discomforts, ranging from mild colitis and diarrhea to full – blown clinical balantidiasis, which may often resemble amebic dysentery. In this case, abscesses and ulcers may form in the mucosa and submucosa of the large intestine followed by secondary bacterial infection. Acute infections are characterized by up to 15 liquid stools per day containing pus mucus, and blood. Patients who suffer from chronic infections may develop a tender colon, anemia, cachexia, and occasional diarrhea, alternating with constipation. Balantidium coli has been known to invade areas other than the intestine, such as the liver , lungs, pleura, mesenteric nodes, and urogenital tract.

Laboratory diagnosis

Laboratory diagnosis of Balantidium coli is accomplished by examining stool specimens for the presence of trophozoites and cysts. Stools from infected patients experiencing diarrhea are more likely to contain B. coli trophozoites. Although it does not occur frequently, suspicious formed stools may contain cysts . sigmoidoscopy material may also reveal B. coli organisms when collected from patients suffering from sigmoidorectal infection .