METAMONADS

• Metamonads

  Amitochondriate multi-flagellated protozoa that have hydrogenosomes or mitosomes, small specialized organelles found in anaerobic eukaryotes that are considered relics of mitochondria

  
• Metamonads

  • Typically pyriform in shape, may have 1 or 2 axostyles and a pelta
  • Flagella are arranged in 1 or more clusters near the anterior end; one may be a trailing flagellum
  • Besides a basal body, some have a parabasal body
  • Reproduce asexually, usually by binary fission
  • May form cysts

  
• Trichomonads

  • Have 1 nucleus in anterior end of body, a parabasal body, 1 axostyle, may have a pelta
  • Have a number of basal bodies (BB) anterior to the nucleus
  • Typically pyriform in shape
  • Have 1-5 anterior flagella (AF) and a posterior flagellum, which may end as a trailing flagellum, arising from the BB
  • Do not form cysts
• Transmission of trichomonads is by direct contact, except for Histomonas meleagridis
• Genera of trichomonads

  • Tritrichomonas
  • Trichomonas
  • Trichomitus
  • Tetratrichomonas
  • Pentatrichomonas
  • Histomonas
  • Parahistomonas
• Tritrichomonas foetus

  Thought to be pathogenic only in cattle causing bovine trichomonosis, a venereal disease; also occurs in the zebu, horse, deer and recently cats and pigs
• Tritrichomonas foetus

  • Organ locations: vagina, uterus, macerated fetus, prepuce, penis, epididymis, and vas deferens of infected hosts
  • Worldwide incidence has markedly decreased due to use of artificial insemination (AI)
  • Listed among notifiable diseases
  • Readily grows on various culture media
  • Has 3 serologically distinct strains: Belfast, Manley, and Brisbane
  • Transmission is naturally by coitus, AI and gynaecological examination of cows
• Pathogenesis of Tritrichomonas foetus in bulls

  Preputial cavity is the principal infection site; generally inapparent; semen contaminated with preputial fluid containing trichomonads will remain infectious in spite of addition of diluents and antibiotics, and freezing
• Pathogenesis of Tritrichomonas foetus in cows

  1. Inflammation of the genital tract

  2. Highest number of organisms in vagina occurs 14-18 days post-infection

  3. Few cases - normal conception and delivery of normal healthy calf

  4. Frequently - early abortion at 8-16 weeks; abortion beyond 6 months is rare

  5. Following abortion - prolonged or permanent sterility; in case of closed cervix and retained corpus luteum - closed pyometra results where fluid swarming with trichomonads accumulates over several weeks
• Immunity to Tritrichomonas foetus

  Little evidence in the bull (infected for life), cows recover spontaneously and only a small proportion remain as carriers for more than a year
• Diagnosis of Tritrichomonas foetus

  1. Presumptive - based on clinical history of reproductive problems associated with introduction of a new bull

  2. Confirmatory - demonstration of the organism: in the vagina, uterine discharge, stomach content for aborted fetuses, preputial washings, after culture (e.g. In-Pouch® TF test kit), serological test, PCR; visualization of movement in fresh fecal smear
• Treatment of Tritrichomonas foetus

  1. Bull - it is not usually recommended, diminazene diaceturate

  2. Cow - breeding rest for 3 months followed by AI; dimetridazole was reported to be effective
• Control of Tritrichomonas foetus

  1. Culling and slaughter of infected bulls

  2. Vaccination and AI in cows
• Tritrichomonas foetus is zoonotic, having been isolated from at least 3 cases in man with meningoencephalitis, peritonitis, biliary and respiratory tract infections, especially in immunocompromised individuals
• Tritrichomonas blagburni

  • Previously identified as T. foetus; occurs in the colon and cecum of dogs (rare) and cats (common) causing chronic waxing and waning mal-odorous large bowel diarrhea that may respond temporarily to antibiotic treatment
  • Diagnosis is vs. Pentatrichomonas hominis in dogs and vs. Giardia in fresh wet fecal smear - live T. blagburni's movement is described as "jerky, forward motion", Giardia as "falling leaf"
  • Ronidazole is reported to be effective in cats but should be given with caution due to its adverse effects in cats and humans (as mutagen)
• Trichomonas gallinae

  • Primarily in pigeons and mourning doves causing avian trichomonosis or canker; also in other birds, e.g. chicken, turkey, hawk, eagle (frounce - disease in raptors)
  • Axostyle is narrow and protrudes a short distance from the posterior end of the body
  • Undulating membrane (UM) extends only to about 2/3 of the body
  • Has 3 strains: Jone's Barn or JB (most virulent) with generation time of 3.5 hours, TG with generation time of 3 h and 50 min, and YG (less virulent) with generation time of 5 h and 50 min
• Pathogenesis of Trichomonas gallinae

  1. Lesions - yellow, circumscribed necrotic lesions in the mouth, esophagus, crop, and proventriculus; possible involvement of the liver, lungs, serous surfaces of the intestine, pancreas, and heart; the abscesses in the liver is considered the cause of death, especially in pigeon squabs

  2. Transmission is via regurgitated crop content ('pigeon's milk'); adult birds are carriers

  3. Treatment is dimetridazole

  4. Control is treatment and prevention of wild birds' access to drinking water
• Trichomonas phasioni

  • Causes enteric disease (diarrhea, dehydration and anorexia) in 3-12-week old pheasant poults
  • Treatment is dimetridazole, furazolidone
• Trichomonas vaginalis

  • Largest of the human trichomonads (mean size: 17 µm by 7 µm)
  • In the vagina, prostate and urethra
  • Experimentally the golden hamster and mouse can be infected
• Infection with Trichomonas vaginalis

  1. Frequently asymptomatic especially in males

  2. Symptoms - degeneration and desquamation of the vaginal epithelium, vaginitis and vulvitis, leucocytic discharge - "may tulo" (copious, greenish-yellow frothy discharge), urethritis that is persistent or recurrent bacterial or fungal infection may accentuate the inflammatory reaction

  3. Diagnosis - microscopic examination of vagina or urine in females and urine or prostate secretions in males, FAT, culture method

  4. Treatment is metronidazole
• Tetratrichomonas gallinarum

  • Forms with 3 or 5 anterior flagella (AF), 4 is the most usual number
  • In the lower digestive tract sometimes the liver of turkey, domestic fowl, and guinea fowl; also found in the quail, pheasant, and partridge
• Pathogenesis of Tetratrichomonas gallinarum

  1. In turkeys, the lesions may resemble enterohepatitis caused by Histomonas meleagridis but they are said to have more irregular outline and are raised from the liver surface instead of being depressed

  2. Infection is by ingestion of contaminated feed or drinking water
• Histomonas meleagridis

  • In the ceca and liver of turkeys; causes histomonosis, infectious enterohepatitis or blackhead (one of the signs is cyanosis of the comb and wattle and other part of the head), particularly in poults
  • Chickens are occasionally affected but are the principal reservoir of infection
  • Also found in the peafowl, guinea fowl, pheasant, partridge and quail
• Histomonas meleagridis

  • In intestinal lumen and culture - it is flagellated (1 or 4 flagella) and ameboid (5-30 µm in diameter), cytoplasm with clear ectoplasm and granular endoplasm, nucleus is vesicular
  • In tissues - occurs singly or in clusters, 8-15 µm in diameter, ameboid but without flagellum

  
• Infection with Histomonas meleagridis

  Ingestion of contaminated feed or drinking water containing infected embryonated eggs of cecal worms
• Histomonas meleagridis is now known to produce cyst-like forms
• Pathogenesis of Histomonas meleagridis

  Fatal in turkey poults in the absence of treatment
• le nucleus

  H. meleagridis
• H. meleagridis

  • Parasite found in the ceca and liver of turkeys
  • Causes histomonosis, infectious enterohepatitis or blackhead
  • Cyanosis of the comb and wattle and other part of the head is one of the signs, particularly in poults
  • Chickens are occasionally affected
  • Principal reservoir of infection
• Hosts

  • Turkeys
  • Peafowl
  • Guinea fowl
  • Pheasant
  • Partridge
  • Quail
• Morphology of H. meleagridis

  • Pleomorphic
  • Flagellated (1 or 4 flagella) and ameboid (5-30 µm in diameter) in intestinal lumen and culture
  • Cytoplasm with clear ectoplasm and granular endoplasm
  • Vesicular nucleus
  • In tissues, occurs singly or in clusters, 8-15 µm in diameter, ameboid but without flagellum

  
• Infection

  Ingestion of contaminated feed or drinking water containing infected embryonated eggs of cecal worms
• H. meleagridis is now known to produce cyst-like forms
• Pathogenesis


  1. Fatal in turkey poults in the absence of treatment

  2. Ulceration of cecal mucosae

  3. Gain entry into the liver via the hepatic portal system
• Lesions


  • Focal necrosis that enlarges by peripheral extension producing the pathogmonic circular depressed lesions with grayish periphery and yellow to yellowish green necrotic centers
  • Development is probably associated with bacteria (Escherichia intermedia, Streptococcus faecalis, Clostridium perfringens)
• Clinical signs


  • Appear 8 or more days after infection
  • Usual signs – sulfur-colored droppings (not a common sign in the chicken), cyanotic the skin of the head and wattles in some birds
• Immunity


  Reinfected recovered birds do not develop disease but harbor the organism in their ceca
• Diagnosis


  • Sulfur yellow droppings
  • Liver lesions
  • Histopathological examination of liver
• Treatment


  • Aminonitrothiazole (Enheptin-T)
  • Acetyl aminonitrothiazole (Enheptin-A)
  • Furazolidone
  • Nithiazide
  • Nitroimidazole antibiotics, e.g. ronidazole, ipronidazole, dimetridazole
• Control


  • Preventive medication
  • Good husbandry (separate chickens from turkeys)
  • Anthelmintic medication vs. H. gallinarum