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Lecture

Microbiology and Immunology 2500A/B Lecture Notes - Serous Fluid, Cysticercosis, Dracunculus Medinensis


Department
Microbiology and Immunology
Course Code
MICROIMM 2500A/B
Professor
C.Y.Kang

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Lecture 8: Parasitology II 09/26/2012
Helminths
The Gang of Four: DALYs (Disability Adjusted Life Years)
HIV/AIDS 84.5 million
NTDs 56.6 million
Malaria 46.5 million
TB 34.7 million
Neglected Tropical Diseases Group
Soil transmitted helminths (worms)
Other helminths
Protozoa
Bacterial infections
13 Core NTDs in Order of Prevalence
1. Ascariasis
2. Trichuriasis
3. Hookworm
4. Schistosomiasis
5. Lymphatic filariasis
6. Trachoma
7. Onchocerciasis
8. Leishmaniasis
9. Chagas disease
10. Leprosy
11. African trypanosomiasis
12. Buruli ulcer
13. Dracunculiasis (almost
gone)
NTDs
High prevalence
Associated with rural poverty
Ancient (not emerging)
Chronic disability and disfigurement
Low mortality
Helminths
MEMORIZE THESE THREE TERMS!
Nematodes (roundworms) in cross section, are round (e.g. earth worms)
Cestodes (tapeworms) segmented flat worms
Trematodes (flukes) unsegmented flat worms
Intestinal Nematodes
Enterobius vermicularis (pinworm)
Ascaris lumbricoides
Trichiuris trichiura (whipworm)
Hookworms
Strongyloides stercoralis
Anisakis
Enterobius Vermicularis
Pinworms
Macroscopically visible
Easy to see because they’re moving
About 5 mm long, quite slender
Harmless
Symptoms itchy anus at night
Nocturnal pruitis ani when females migrate to perianal skin to lay eggs live in the secum (large valve) every
night, females migrate and lay their eggs
Benign
Most common nematode infection in North America
30% of children infected worldwide
Scotch tape test sticky side out, wrapped around a tongue depressor and used to find pinworms
Flat on one side and round on the other
Soil Transmitted Helminths
Worms cannot reproduce in the body
whatever you get infected with in the
first place, is what you have
The longest a worm can live in one’s body
is 8 9 years
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Nematodes (roundworms)
o Ascariasis
o Hookworm
o Trichuriasis (whipworm)
Ascaris Lumbricoides
Large, about size of a pencil
Male and female ascaris
Normally harmless, unless there’s a lot of them – causes bowel destruction
One billion infected worldwide, #1 NTD
Adult worms live in the upper small intestine
Females produce enormous numbers of eggs which do not become infective until they are embryonated, 2 3
weeks in soil
Problems arise due to migration of adult worms and hypersensitivity to larvae in lungs
Ascariasis: Pulmonary Phase
Cough, blood tinged sputum, wheezing, dyspnea + urticaria (hives)
Transient 30% - 50% eosinophilia
o eosinophilia levels increase good screening test
Transient pulmonary infiltrates
Ascariasis: Intestinal Phase
Usually asymptomatic unless heavy infestation
Adult worms may be coughed up, vomited or emerge from nose or anus
Adult worms may migrate into common bile duct, pancreatic duct, appendix, etc. and cause obstruction
Trichuris Trichiura
Whipworm
Light infections asymptomatic
Heavy infections lead to dysentery and blood loss in the stool
Trichuris dysentery syndrome anemia, rectal prolapse, finger clubbing and growth stunting
Rx: mebendazole or albendazole
Intestinal Hookworms
Ancylostoma duodenale, Necator americanus
End up in bowels, sucking on the micro-villi that line the bowels
Heavy infestation causes anemia
Light infestation doesn’t really do any harm
About 25% of world population infected, 80% in some areas
Most asymptomatic but depends on worm burden and stage
Ground itch is first manifestation following skin penetration: maculopapular or vesicular pruritic dermatitis
Pulmonary symptoms (cough, wheezing, blood tinged sputum with transient eosinophilia) occur when larvae
migrate through lungs on way to intestine
Intestinal infection usually asymptomatic but heavy infestation causes anemia
Hookworm Management
CBC to check for anemia
Albendazole
Pyrantel pamoate (OK in pregnancy)
Mebendazole
Note: any of these simultaneously treat ascariasis and trichuriasis
Cutaneous Larva Migrans: Ancylostoma brasiliense
Dog or cat worm
Cannot complete life cycle in humans
Crawl around and produces intense itchiness
Strongyloides stercoralis
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