Family Retortamonadidae

Members of this family have 2 or 4 flagella, of which 1 is trailing, a single nucleus and a cytostome with supporting fibrils. There are 2 genera of veterinary interest, Retortamonas and Chilomastix.

Genus Retortamonas

The body is usually piriform or fusiform, drawn out posteriorly, and plastic. There is a large cytostome near the anterior end containing in its margin a cytostomal fibril which extends across the anterior end and posteriorly along each side. An anterior flagellum and a posteriorly directed, trailing flagellum emerge from the cytostomal groove. The cysts are piriform or ovoid, have 1 or 2 nuclei, and retain the cytostomal fibril. A synonym of this genus is Embadomonas Mackinnon, 1911. Species occur in various insects, amphibia, reptiles and mammals. (Ansari, 1955, 1956).

Retortamonas intestinalis (Wenyon and O'Connor, 1917) Wenrich, 1932 (syns., Embadomonas intestinalis, Waskia intestinalis) occurs in the cecum of man and probably also in the chimpanzee, macaques and other monkeys. Dobell (1935) was unable to infect a Macaca mulatta and a M. sinica with cultures of R. intestinalis from man, but nevertheless believed it likely that the Retortamonas of man and macaques belong to the same species. It is not common in man, and is non-pathogenic.

The trophozoites of R. intestinalis are elongate piriform, 4 to 9 u long and 3 to 4 u wide. The cysts are uninucleate, piriform, 4.5 to 7 u long and 3 to 4.5 u wide and have a rather thick wall. This species can be cultivated in the usual culture media for intestinal protozoa.

Retortamonas ovis (Hegner and Schumaker, 1928) (syn., Embadomonas ovis) was described from trophozoites and cysts in cultures from sheep feces in Maryland. The trophozoites are piriform and average 5.2 by 3.4 u.

Retortamonas cuniculi (Collier and Boeck, 1926) (syn., Embadomonas cuniculi) occurs in the cecum of the rabbit. The trophozoites are generally ovoid but occasionally have a tail-like process; they measure 7 to 13 by 5 to 10 u. The cysts are oval and measure 5 to 7 by 3 to 4 u. Collier and Boeck (1926) found this species in 1 of 50 rabbits. It is apparently non-pathogenic.

Genus Chilomastix

The body is piriform and plastic, with a large cytostomal groove near the anterior end containing in its margin a cytoplasmic fibril which extends across the anterior end and posteriorly along each side. The nucleus is anterior. There are 3 anteriorly directed flagella and a short fourth flagellum which undulates within the cytostomal cleft. Cysts are formed. Synonyms of this genus are Macrostoma Alexeieff, 1909 and Fanapepea Prowazek. Chilomastix is found in mammals, birds, reptiles, amphibia, fish, insects and leeches. All species are apparently non-pathogenic.

Chilomastix mesnili (Wenyon, 1910) Alexeieff, 1912 (syns., Macrostoma mesnili, Chilomastix suis, Chilomastix hominis) is found in the cecum and colon of man, the orang-utan, chimpanzee, a number of monkeys (Macaca, Cercopithecus, Cebus, Pithecus) and the pig. It is quite common in man, having been found in 1 to 28% in various surveys; according to Belding (1952), it was found in 3.4% of 35,577 persons in recent surveys in the United States, and in 6.1% of 19,006 persons elsewhere in the world. Frye and Meleney (1932) found it in 3 of 127 pigs in Tennessee. Kessel (1928) found it in pigs in California, and Reichenow (1952) in Hamburg, Germany. Simitch et al. (1959) found it in 1.7% of 1800 pigs in Yugoslavia.


Kessel (1924) transmitted C. mesnili from man to monkeys, and Deschiens (1926) from the chimpanzee to Macaca sinica. However, Sim itch el al. failed to transmit C. mesnili from man to 2 young pigs and consequently named the pig form C. suis.

The trophozoites of C. mesnili are asymmetrically piriform, with a spiral groove running thru the middle half of the body. The posterior end is drawn out when the protozoa are moving. The trophozoites are 6 to 24 u long and 3 to 10 u wide. The cytostomal cleft is about 6 to 8 u long and 2 u wide. A complex of 6 minute blepharoplasts lies anterior to the nucleus; from them come the 3 free anterior flagella (of which 2 are short and the third is relatively long), the cytostomal flagellum, and the 2 cytostomal fibrils. The cysts are lemon-shaped, 6.5 to 10 u long, and contain a single nucleus and the organelles of the trophozoite.

C. mesnili is ordinarily considered non-pathogenic. However, Mueller (1959) suggested that it might possibly be a mild pathogen occasionally. He referred to an outbreak of watery diarrhea in very young children in Czechoslovakia and to his own experience with watery diarrhea accompanied by swarms of Chilomastix following a visit to Mexico. This species can be cultivated in the usual media used for intestinal protozoa.

C. cuniculi da Fonseca, 1915 occurs in the cecum of the domestic rabbit. It is morphologically similar to C. mesnili. The trophozoite is ordinarily 10 to 15 u. long, but may range from 3 to 20 u.

C. caprae da Fonseca, 1915 was reported from the rumen of the goat in Brazil. Das Gupta (193 5) found it in India. It is morphologically very similar to C. mesnili and is 8 to 10 u long and 4 to 6 u wide.

C. gallinarum Martin and Robertson, 1911 occurs in the ceca of the chicken and turkey. McDowell (1953) found it in 40% of a large number of chickens in Pennsylvania. The body is pear- or carrot-shaped, 11 to 20 by 5 to 12 u. The nucleus is pressed against the anterior end of the body. The cytostomal pouch is 8-shaped, spirals toward the left on the ventral side, and extends 1/2 to 2/3 of the body length. Cysts are rare in cecal material but common in culture. They are lemon-shaped, measure 7 to 9 by 4 to 6 u, and have a single nucleus. McDowell (1953) cultivated C. gallinarum easily in Ringer's solution with 0.2% gastric mucin at 39 to 40 C.

C. intestinalis Kuezynski, 1914 and C. wenrichi Nie, 1948 occur in the cecum of the gunea pig, and C. bettencourti da Fonseca, 1915 in that of the laboratory rat, domestic mouse and golden hamster.