L15: Trichurida Flashcards
Please give the old method of classifying nematodes
Due to the presence of phasmids (excretion and chemoregulation) , however these may be difficult to see
Give the new method of classifying nematodes
Due to the presence of the stichosome (glandular oesophagus) and lateral excretory glands
Briefly describe the Class Adenophorea
- Stichosome
- No phasmids
- No excretory canals
- Not parasitic
Briefly describe the Class Secernentia
- No stichosome
- Phasmid present
- Excretory canals present
- Lateral excretory duct present
- Mostly parasitic
Give the two orders in the Class Adenophorea
Order Trichurida
Order Dictyophymata
Describe the causual agent of Trichuriasis
Humans- Trichuris trichuria (Large intestine of humans)
Dogs- Trichuris vulpis
Pigs- Trichuris suis
Explain the distribution of Trichuriasis
Tropical Disease
Children 5-15
Mostly in Asia but also South America and the Caribbean
795-1050M cases globally
DALY’s lost==0.8-6.4M
Transmitted within families usually in poorer areas
How does T. trichiura feed on blood of the host?
They possess a sharp stylet which pierces through the large intestine causing the anterior end to burrow in between epithelial cells where they feed on blood
How do we differenciate the male T.trichura from the female
Female- 50mm long Anterior end- 100um diameter Posterior end- 500um diameter End is not coiled Male- smaller with a coiled posterior end
Describe the Trichuris eggs
Lemon-shaped with terminal plugs at both ends
What are the dimensions of a typical T triciura egg
20-25cm by 50-55cm
What causes a prolasped rectum in extreme cases of Trichuriasis
Metabolic products of the parasite temporarily numb the ganglia associated with the terminal end of the rectum
Give the symptoms of T.trichiura infection
The intestinal epithelium and submucosal layer experience damage and hemorrhaging which can result in anaemia and protein losing enteropathy. In Since the colon is not sterile there may also be bacterial infections and even allergic responses causing swelling. In extreme cases there may be a prolapsed rectum, stunting and finger clubbing.
Often there is also insomnia, nervousness, loss of appetite, vomiting, prolonged diarrhea, skin rashes, constipation, flatulence and verminous intoxication
Explain what is meant by the term “verminous intoxication”
The parasite is releasing its own metabolic byproducts which are absorbed by the host
Explain the process of diagnosis of the parasite
Examination of stool
Which drugs may be used to treat infection
Albendezol
Mebendazol- 3 days
True or False- Trichuriasis infections might be accompanied by E histolytica
True
List some control methods for this parasite
Improved hygiene and sanitation
Proper cooking of food
What is geophagia and in which group does it most commonly occur?
The ingestion of soil which commonly occurs in children
What can we deduce from the graphs shown in the lecture
Children are most likely to be infected and to have high intensity infection
What contributes to the high prevalence of Trichurasis
- High Geophagia
- Low immunity
Explain the hypothesis and outcome of Joel Weinstock’s experiment
Observation- Increase in intestinal diseases following reduced incidents of intestinal worm infection in developed countries
Hypothesis-Bowels in the absence of parasites become overactive causing bowel disease
Experiment- Exposure of patients with Chron’s disease and ulcerative colitis (incurable) with T. suis eggs
Results- Disappearance of symptoms with 50-70% relapses
Conclusion- Our immune systems have evolved to combat intestinal parasites and so in the absence of them, these same systems may become overactive
What issue arised when treating Trichinellosis with mebendazole
Kills all parasites at once and can cause a major inflammatory response
Steriods used to combat the inflammatory symptoms
What methods of detection can be used for Trichinellosis
Muscle biopsy for nurse capsules
Antibody detection
Microscopy
Give the main features of Trichinellosis
Parasite- Trichinella spiralis
Other species of Trichinella are now recognized
T. pseudospiralis (mammals and birds worldwide)
T. nativa (Arctic bears)
T. nelsoni (African predators and scavengers)
T. britovi (carnivores of Europe and western Asia).
Geographic Distribution:
Worldwide. Most common in parts of Europe and the United States
About 50M human infections
Give an account of the general description of the parasite which causes Trichinellosis
t is the smallest nematode parasite of humans
Male 1.5mm
Female 3.0mm
A single host acts as both the definitive and intermediate host
Adults in small intestine
Larvae occur muscle
There are no free-living stages
A zoonosis
The disease in humans is a dead end for the parasite
Discovered by London medical student James Paget in 1835 in cadavers provided for dissection (gritty particles in musculature)
Give an Immunological account of Trichenellosos
Light infections may be asymptomatic.
Intestinal invasion by L1’s can be accompanied by gastrointestinal symptoms (diarrhea, abdominal pain, vomiting).
Larval migration into muscle tissues (one week after infection) can cause periorbital and facial edema, conjunctivitis, fever, myalgias, splinter hemorrhages, rashes, and blood eosinophilia.
Larvae are present in the muscles in a ‘nurse cell-parasite complex’ causes myalgia and weakness, followed by subsidence of symptoms.
Eventually nurse cell-parasite complex calcifies
Occasional life-threatening manifestations include myocarditis, central nervous system involvement, and pneumonitis.
