L15: Trichurida

Question 1

Please give the old method of classifying nematodes

Answer 1

Due to the presence of phasmids (excretion and chemoregulation) , however these may be difficult to see

Question 2

Give the new method of classifying nematodes

Answer 2

Due to the presence of the stichosome (glandular oesophagus) and lateral excretory glands

Question 3

Briefly describe the Class Adenophorea

Answer 3

• Stichosome
• No phasmids
• No excretory canals
• Not parasitic

Question 4

Briefly describe the Class Secernentia

Answer 4

• No stichosome
• Phasmid present
• Excretory canals present
• Lateral excretory duct present
• Mostly parasitic

Question 5

Give the two orders in the Class Adenophorea

Answer 5

Order Trichurida

Order Dictyophymata

Question 6

Describe the causual agent of Trichuriasis

Answer 6

Humans- Trichuris trichuria (Large intestine of humans)
Dogs- Trichuris vulpis
Pigs- Trichuris suis

Question 7

Explain the distribution of Trichuriasis

Answer 7

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

Question 8

How does T. trichiura feed on blood of the host?

Answer 8

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

Question 9

How do we differenciate the male T.trichura from the female

Answer 9

Female- 50mm long 
Anterior end- 100um diameter 
Posterior end- 500um diameter 
End is not coiled 
Male- smaller with a coiled posterior end

Question 10

Describe the Trichuris eggs

Answer 10

Lemon-shaped with terminal plugs at both ends

Question 11

What are the dimensions of a typical T triciura egg

Answer 11

20-25cm by 50-55cm

Question 12

What causes a prolasped rectum in extreme cases of Trichuriasis

Answer 12

Metabolic products of the parasite temporarily numb the ganglia associated with the terminal end of the rectum

Question 13

Give the symptoms of T.trichiura infection

Answer 13

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

Question 14

Explain what is meant by the term “verminous intoxication”

Answer 14

The parasite is releasing its own metabolic byproducts which are absorbed by the host

Question 15

Explain the process of diagnosis of the parasite

Answer 15

Examination of stool

Question 16

Which drugs may be used to treat infection

Answer 16

Albendezol

Mebendazol- 3 days

Question 17

True or False- Trichuriasis infections might be accompanied by E histolytica

Answer 17

True

Question 18

List some control methods for this parasite

Answer 18

Improved hygiene and sanitation

Proper cooking of food

Question 19

What is geophagia and in which group does it most commonly occur?

Answer 19

The ingestion of soil which commonly occurs in children

Question 20

What can we deduce from the graphs shown in the lecture

Answer 20

Children are most likely to be infected and to have high intensity infection

Question 21

What contributes to the high prevalence of Trichurasis

Answer 21

• High Geophagia

- Low immunity

Question 22

Explain the hypothesis and outcome of Joel Weinstock’s experiment

Answer 22

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

Question 23

What issue arised when treating Trichinellosis with mebendazole

Answer 23

Kills all parasites at once and can cause a major inflammatory response
Steriods used to combat the inflammatory symptoms

Question 24

What methods of detection can be used for Trichinellosis

Answer 24

Muscle biopsy for nurse capsules
Antibody detection
Microscopy

Question 25

Give the main features of Trichinellosis

Answer 25

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

Question 26

Give an account of the general description of the parasite which causes Trichinellosis

Answer 26

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)

Question 27

Give an Immunological account of Trichenellosos

Answer 27

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.