Protozoan Parasites: Flagellates, Amoebae, Ciliates...
Transcript of Protozoan Parasites: Flagellates, Amoebae, Ciliates...
Protozoan Parasites: Lecture 17 - Trichomonas & Histomonas
Pages 10-18
Spencer Greenwood
BSc, MSc, PhD, DVM
Dept. of Biomedical Sciences
Office: 2332N AVC-North Annex
Phone: 566-6002
Home: 892-4686
E-mail: [email protected]
http://people.upei.ca/sgreenwood/index.htm
Trichomonosis
• Bovine Trichomonosis – “Trich”
• Avian Trichomonosis – “Canker” or “Frounce”
• Feline Trichomonosis
• Non-pathogenic Trichs – Pigs, horses & dogs...
Bovine Trichomonosis
• Tritrichomonas foetus
• Infection of the reproductive tract
• Morphology
• Only a single life stage – Trophozoite is the infectious stage
– pyriform shaped
– 10-25 um long with 3 flagella & an undulating membrane with a posterior free flagellum
• Do not produce cysts
Life Cycle
• Direct – Transmitted by “natural
service”
• Bulls – Trophs in the prepuce, penis,
epididymis & vas deferens
• Cows/ heifers – Trophs in the vagina, cervix &
uterus
Transmission
• Cows/heifers – Trophs during copulation
– Infections persist for weeks- months
– Usually recover
• but can be re-infected
• Bulls – Trophs during copulation
– Bulls may be infected for life (carrier)
– Mature bulls > young bulls
• A.I. – Rare - contamination
Prevalence
• Bull infection rates 6-8% – BUT as high as 44%!!
• Reports increasing: – New Mexico
– Colorado
– Oklahoma
– Alberta...yes, Canada too!
Pathogenesis
• Invasion of the uterus – Leads to placentitis which results in detachment, death & abortion of
fetus
• Trophs may also invade the fetal tissues
Clinical signs
Cows/heifers • Typically minimal
– Mild mucopurulent discharge
• “Open cows” – Calf production decreases by 50-
80% in newly infected herd
• “Abortion” before 5 months gestation
• Vaginitis &/or pyometra
• Retained fetus & membranes – Leading to endometritus &
sterility
• Increased calving interval
Clinical signs
Bulls • No clinical signs of infection
Diagnosis
• Trophs – Preputial scrapings or
washings (smegma)
– Vaginal secretions, vaginal washings
– Absorbed fetuses
– Avoid contamination with gastrointestinal trichs (non-pathogenic confounders)
• Distinct "rolling" motion
• Diff-Quick/iodine stain
http://www.indiancountryextension.org/extension.php?=24
Diagnosis
• In Pouch TF - culture kit – Look for trophs under microscope
– Selective medium for Trichs
• Polymerase chain reaction (PCR)
• Immunofluorescent assay (IFA)
• Repeat sampling may be required to confirm infection status – 3 tests @ weekly intervals
Treatment
Cows/heifers: – No treatment available
• 4 months sexual rest to clear infection
• ~3% remain as ‘carrier cows’
• Normal term pregnancy expected
Treatment
• Bulls: – No approved drugs
– CULL ALL INFECTED BULLS
Control
• Bulls: – Cull infected bulls & use non-
infected or virgin bulls
– Pre-breeding exam
• Test all bulls for trich
• Use A.I.
• Younger bulls – Reduce transmission
– Replace every two years
Control
Cows: • Maintain a limited breeding
season
• ID & separate infected cows – Sexual rest of 4 months or cull
• Buy only confirmed pregnant replacements
• Vaccine: Trich Guard®
• Female herd only
• “partial” efficacy
• Annual re-vaccination
• No efficacy in Bulls
Avian Trichomonosis Trichomonas gallinae - Infection of the crop of birds
Trichomonas gallinae Infection of the crop of birds
• Disease known by many names:
– ‘Canker’
• pigeons, songbirds...
– ‘Frounce’
• Raptors
– ‘Roup’
• poultry & fowl
Morphology
• Trophozoite – Single life stage
– Pyriform shaped
– 5-9 um, with 4 flagella & an undulating membrane with embeded recurrent flagellum
• Trophozoite or Trich is the infectious stage
• No cysts
http://www.ucm.es/info/parasito/gallinae.jpg
Life cycle
• Transmission:
• Direct – Oral-oral, contaminated
waterers, bird baths, puddles... Moist bird feed!
– Trophs reproduce by binary fission
– T. gallinae & other Trichs are normal oral flora
• Avirulent & virulent strains
– STRESS
Transmission
Pathogenesis
• Rapid disease
– 10-14 days
• Trophs invade upper intestinal tract
– Oral cavity, sinuses, pharynx, esophagus & crop
Pathogenesis
• “Canker” - yellow, caseous nodules
Pathogenesis
• Liver may be invaded by trophs (rare)
– Lesions on surface, solid white-yellow & circular
Clinical signs
• Difficulty swallowing – Yellow-caseous mass,
– Drool, green- yellow mucus in oral cavity & dripping from beak
• Gape mouth
• Listless, ruffled & emaciated
Diagnosis
• Clinical signs & gross lesions (PM) – Restricted to the upper portion of the
digestive tract
• Direct smears - Definitive Dx – Trophs in oral fluids or lesions in the
mouth, crop or digestive tract
• Culture – In Pouch technique useful
• Medium selective for Trichs
• Confounding non-pathogenic Trichs
• PCR
Trich research in action
Control & Treatment
• Eliminate infected birds & suspected carriers
• Avoid feeding pigeons to raptors in rehab
• Proper sanitation – Source of fresh, clean food & water
– Prevent pigeons from contaminating water & food supply of domestic fowl
• Anti-flagellate drugs – Metronidazole, dimetronidazole & ronidazole
• REDUCE STRESS
Feline Trichomonosis
• “Discovered” in 1996
• Problem in young cats
– in multi-cat households, catteries & shelters
• Tritrichomonas foetus
– Morphology identical to bovine trichomonad
• 31% infection in 117 cats from 89 catteries @ International cat show
• First reports found that feral cats, same demographic - no trichs!
Transmission
• Trichomonads usually commensal organisms & cause no clinical signs
• Transmission route unknown – No cysts, so trich/troph is
infectious stage
• Direct “cat to cat” most likely – Mutual grooming
• Multi-cat litter box? – Trichs can survive ~6-24 hours in
feces (moist but firm)
Clinical Signs
• Chronic large bowel diarrhea – Waxing & waning
– Duration up to ~ 2 years
• May resolve spontaneously
– Cow-pie diarrhea
• w/wo blood & mucus
– Often with fecal incontinence
• P.E. – Anus edematous & painful
– Dribbling feces, rectal prolapse... http://www2.ncsu.edu/unity/lockers/project/cvmaprhome/gookin_file2.htm
Pathogenesis
• T. foetus colonizes mucosal surface of ileum, cecum & colon – Less frequently found in colonic crypts lumen
• Infiltration of lymphocytes & neutrophils, loss of goblet cells in intestinal mucosa
– mild to severe lymphoplasmacytic colitis
• Mechanism unknown
– likely involves disruption of normal flora, adherence to the epithelium & induction of host cytokines & enzymes
http://www2.ncsu.edu/unity/lockers/project/cvmaprhome/gookin_file2.htm
Diagnosis
• Direct fecal smear
• In pouch TF culture – Medium selective for Trichs
• Polymerase chain reaction (PCR) @ CVM-NC State University
• Confounding organisms – Other trichomonads, Giardia...
Treatment
• Sanitation & hygiene – Human infections?
• Reduce stress – Numbers of cats…
• No approved treatment – Ronidazole: 30 mg/Kg twice
daily for 2 weeks
– Resolves diarrhea & eradicates infection!
Transmission - Cross infection?
Histomonosis
• Histomonas meleagridis
• Blackhead disease or Infectious enterohepatitis
Histomonosis
• Site of infection
– Cecum & liver
• Morphology
– Pleomorphic
– Various trophozoites
• Flagellate & amoeba stages
• 5-30 um long
• No cysts?
“Artist’s rendering…not mine”
Transmission
• Fecal-oral
– Heterakis eggs
– Earthworm
– Mechanical vectors • Flies…
• Cloacal drinking
• Virulence/isolates?
Epidemiology
• Common in North America
• Histomonas remain viable within Heterakis eggs for 1-2 years
• Mainly affects young birds
– Turkeys 3-12 weeks old
• High mortality (50 - 100%)
– Chickens 4-6 weeks old
• High morbidity, low mortality
Pathogenesis
• Trophs penetrate – Cecum & invade liver via
the blood stream
• Cecal lesions – Edematous & lumen is
filled with yellow caseous smelly exudate
• Liver lesions – Circular depressed yellow-
green to grey areas of necrosis (1-2 cm)
– ~ 10 days post infection w3.ufsm.br/.../ histomonastrofozoitofigado2.jpg
Clinical signs
• 2-3 weeks post infection – Hunched appearance, droopy wings &
tail, ruffled feathers
– Anorexia & emaciation
– Black or cyanotic head (occasionally)
– Foul smelling, sulfur- coloured diarrhea
Diagnosis
• Clinical signs
– Brilliant yellow (sulfur) feces with cecal & liver lesions (PM)
• Histomonas on histo sections (liver & cecum)
• Cecal or liver scrapings
– Saline smear
• Beware confounding cecal flagellates – Normal flora?
http://www.vet.purdue.edu/courses/ai/vm550/Spring%202003/Bird/fig8.jpg
http://www.affrc.go.jp/AVEM/Japanese/atlas/protozoa/histomonas/histom1.jpg
Treatment & Control
• Good sanitation practices
• Turkeys & chickens must be raised separately
• Control Heterakis gallinarum in birds & limit access to eggs & earthworms
• Prophylactic & therapeutic treatment? – Antibiotic resistance emerging…
– Tiamulin 25 mg/kg for five days • (Birch et al. 2007 Vet Record)
Amoebae, Ciliates & Coccidia