Dr. Zhou - Lecture 20 Flashcards
1
Q
Helminths
A
Worms
2
Q
Constitutional symptoms
A
a group of symptoms characteristic to a disease, effecting many different body systems
Ex: weight loss, fevers, idiopathic fevers, hyprehidrosis, chronic pain, fatigue, dyspnea, etc
3
Q
Trichinosis is caused by:
A
- Any species of Trichinella parasite
- In artic bear + walrus meat, most common species: T. nativa
4
Q
General features of a helminth
A
- Helminth = worm
- Usually large (0.3 mm-25m)
- Grotesque:
- squirming white worms coming out of nose; feeling and seeing a worm creep beneath your skin; slither across your eye
5
Q
Categories of helminth
A
- Nematodes: roundworms
- Trematodes: flukes
- Cestodes: tapeworms (huge, long; infects intestines of pts or animals)
6
Q
helminth Life and Transmission Cycles
A
A COMPLETE life cycle:
- Fertilized egg (embryo) –> larva –> adult
Some worms have:
- Intermediate (2ndary) host: where larval development
- Definitive (final) host: adulthood + mating
SEXUAL reproduction
- separate sexes: nematodes
- Separate or hemaphroditic: trematodes
- Hermaphroditic: Cestodes
7
Q
Basic Helminth Life Cycles - Source of Infection, Route of Infection, # life cycles
A
Source:
- Contaminated food
- Soil, water
- Infected animals
Route:
- PO
- Skin penetration
5 basic life cycles
8
Q
Cycle A
A
- Source: food + water contaminated w/ mature eggs
- Route: PO
- Human eats contaminated food/water –> Larva hatches in tissues –> travels to intestines to mature + mate
- Embryonic eggs are then released back into environment
9
Q
Cycle B
A
- Source: contaminated soil or other environment contact
- Route: Skin penetration
- Eggs + larvae mature in environment instead of host to allow skin penetration
- Larvae migrates to intestines to mature + mate –> eggs released back into environment
10
Q
Cycle C
A
- Source: Contaminated meat
- Route: PO
- Person eats contaminated livestock (host 1) –> Cyst formation in muscle/gut of host 2 –> larva released in digestive tract –> travel to intestines to mature + mate
- Eggs released back into environment
- Eggs taken up by livestock again (host 1)
3 settings
11
Q
Cycle D
A
2 Routes/Source: Contaminated meat OR direct skin penetartion
- Parasite travels into intestines of bladder –> mature + mate to make eggs (1)
- Eggs released into environment (2) –> eggs develop into 1st larva stage –> infect intermediate (2ndary) host (3) –> 2nd larva stage development
- 2nd stage larva can infect via infected meat or direct skin penetration
- More complicated
12
Q
Cycle E
A
- Source: Insect bites
- Route: skin penetration
- Infected larva gets lodged in tissues
- New larva released into circulation, ready to be transferred into insects + new hosts
Humans + insects
13
Q
Epidemiology
A
Large # infections:
- # worm infections > # humans
Kids in rural tropics/subtropics
- Schistosomiasis
- Filariasis
- Hookworm diseases
- Ascariasis
- Oncocerciasis
In developed nations:
- Pinworm and trichinosis
Continuing infection :
- Unprocessed sewage as fertilizer, eating raw fish/meat, exposing bare feet in contaminated soil/water
Pts can get infected mult times
14
Q
Helminth infection patho
A
Symptoms:
- Organ enlargement
- Hemorrhage
- Weight loss
- Anemia
Worms migrate w/ enzymes to liquefy + penetrate tissues: feeding, tissue damage (=inflamm), blocked ducts + organs, toxic secretions (growing mass of worms block lymphatic ducts), pressure
Host immunity incomplete bc worms often have: protective coverings, large, inaccessible to immune system attacks, and migration
15
Q
Helminth Diagnosis (3)
A
- Eosinophilia: increase # of eosinophils (granular leukocytes that destroy worms)
- Travel history
- Detecting eggs in stool, urine, or blood
16
Q
Major Helminth Infections
A
I: Nematode (roundworm infections)
- Headless worms w/ smooth, protective outer cuticle, periodically shedding as worm grows
- Distinct sexes (female vs. male worms)
- One of the most abundant animal groups
- Most are NOT parasites
- 50 species –> human parasites
- 2 types (based on infection site + maturation):
- Intestinal nematodes
- Tissue nematodes
17
Q
I-1: Intestinal Nematodes - Cycla A
A
- Cycle A
- Ascaris Lumbricoides (A. Lumbricoides) causes Ascariasis
*300 mm long (~1ft)
*1 Billion infections
*in US: mostly in southern states - Life cycle:
Larva + adult in humans –> embryonic eggs in feces –> contaminates food –> Eaten –> intestines –> circulation –> heart –> lungs –> throat –> swallowed –> small intestine –> 200,000 embryos/day/worm
18
Q
A. lumbricoides
A
- Worms keep motility, do not attach
- Severe inflamm rxns mark on skin on migratory route
- Allergic rxns can happen
- Heavy worm loads can retard physcial + mental development
19
Q
I-2: Intestinal Nematodes
A
- Cycle B
- I-2-1: hookworms - larvae burrowing into skin –> circulation –> lung –> throat –> small intestine (similar to A except route of entry)
- Small hook-like tails, teeth to anchor into intestines
20
Q
I-2-1 symptoms
A
- Dermatitis (ground itch)
Pneumonia - NV, pain, bloody diarrhea
- Chronic fatigue, anemia
21
Q
I-2-2
A
Strongyloidiasis
- Threadworm (aka Pinworm) infections
- 100-200 mill pts worldwide
- Threadlike inflamma marks on skin
22
Q
I-2-2 Symptoms
A
- Bloody diarrhea
- Liver enlargement
- Bowel obstruction
- Malabsorption
23
Q
I-2-3
A
- Trichinella spiralis (T. spiralis) causes Trichinosis
- Mammalian hosts
- Encysted larval form in muscles
- Human infections source: raw meat from pig or bear
- US: few new cases/yr
24
Q
I-2-3 Symptoms
A
Initially:
- Fever
- Diarrhea
- Nausea
- Abdominal pain
- Sweating
2nd phase: - Intense muscle + joint pain - SOB - Eosinophilia Leading to heart + brain damage and death (if untreated)
25
I-2-3 Prevention:
- Cook meat well
- Freezing also kills worm larvae (T. spirolus in pork also) but NOT for Alaska variant (T. nativa) since they're used ot the cold
26
T. nativa
- in Alaska bear + walrus meat
- Cold-resistant
- Freezing will NOT kill larva cysts
- Bear + walrus meat are safe once entire piece of meat is completely cooked to a GRAY color
- USDA: internal temp of at least 160 degrees F
- Microwaving may not make food safe bc of uneven cooking
27
I-3: Tissue nematodes
I-3-1
I-3-1: Filarial nematodes; filariasis
- Cycle E
- Long threadlike worms
- BIPHASIC life cycle: alternating btwn humans + mosquitos/flies
- 2 MAJOR species:
* Wuchereria bancrofti (W. bancrofti)
* Onconcerca volvulus (O. volvulus)
28
I-3-2
- Disease: Bancroftian filariasis
- W. bancrofti (long threadlike worm)
- Affects 120 mill
- Symptoms: elephantiasis - inflamm + blockage of main lymph channels --> fluid accumulation
29
I-3-3
- River blindness: invasion of eyes
- West African villages along rivers: 50% adults blind
- Breeding sites for black flies
- O. volvulus
- Onchocerciasis: inflamm, granulomatous lesions; river blindness
30
I-3-4:
- Loa Loa: African eye worm
- Transmitted by fly
- Can be felt slithering beneath skin
31
I-3-4 Treatment
- Pull worm out
| - Diethylcarbamazine
32
I-3-5
- Dracunculus medinensis (D. medinensis): Dragon worm
- Disease: dracontiasis
- India, Middle East, Central Africa
- Cyclops: arthropod in still water
Infection cycle:
Ingestion of larva in cyclops --> intestine --> SQ tissue --> irritants released --> itching blisters (fireworm) --> blisters erupt in water --> cyclops released
33
II. Trematodes/Flukes
Fluke: mostly flat (flatworms)
| 2nd major category of worms
34
II-1
Blood flukes: the Schistosomes
- Cycle D
- Infection: Old disease - ancient Egyptians observed males "mensturating" --> kidney schistosomiasis
- Overall 200 mill infections in world (Africa, South America, middle East, Far East)
35
Blood Fluke Symptoms
Symptoms:
- Fever
- Chills
- Diarrhea
- Cough
Chronic infections:
* Hepatomegaly (liver enlargement)
* Splenomegaly (spleen enlargement)
* Bladder obstruction
* Kidney damage
* Bloody urine
* Brain damage
36
Blood Fluke Life-Cycle and Control
Life Cycle:
Infected humans --> eggs released from host to environment --> develop into ciliated larva (miracidium) --> snails infected (1st host) --> forked larva (cercaria) --> penetrating human skin --> circulation --> liver --> intestine (mature+mate+make more eggs) --> feces (released into environ
- Males + females are intertwined FOR LIFE to facilitate mating + reproduction
Control: Snail-eating fish
37
II-2: Liver and Lung Flukes (cycle, reproduction, hosts, sources of infection, body location)
- Cycle D
- Develop in liver or lung
- Sexual development in humans
- Intermediate (2ndary) hosts: snails
- Infection caused by ingesting not fully cooked or raw freshwater fish + crustaceans
- Hemaphroditic
38
II-2 Life Cycle
Hatched larva --> cross into bile duct and grows+matures --> shed eggs into intestinal tract --> releasing into feces in standing water --> taken up by snails --> cercariae --> infect fish
39
III: Cestode/Tapeworm Infections (cycle, morphology)
- Cycle C
- Usually very long
- Hermaphroditic
Morphology:
- Scolex: head - sucker, NO MOUTH
- Neck
- Strobila: ribbon made up of reproductive segments (prolgottids)
40
Beef Tapeworm
- Taenia saginata (T. saginata)
- Disease: Taeniasis
- 2000 proglottids anchored by a scolex w/ suckers per T. saginata
- Worldwide
- Cows infected by eating in fields w/ proglottids or eggs contamination
- Human infection source: eating raw beef
Symptoms:
- Mild abdominal pain
- Nausea
41
Beef Tapeworm life cycle
Eggs eaten by cows --> ecysted larva (cysticercus) in grow in beef muscle --> human eats contaminated undercooked meat --> develop into proglottids --> released in feces into environment
42
Swine Tapeworm
```
Taenia solium (T. solium)
- SAMLLER than T. saginata
```
- Endemic in areas eating raw or partially cooked pork (Southeast Asia, South America, Mexico, Eastern Europe)
- Disease: Cysticercosis: severe form of T. solium infection
43
Cysticercosis
- Severe form of T. Solium infection
- Tapeworm larvae migrate to different tissues
- Form peculiar cysticerci
- Tissue damage: heart, brain, eye
- Caused by raw/partilally cooked pork, undercooked fish
44
Worms in my Sushi?
- Yes: fish helminths
Anisakis --> anisakiasis
- Tingling feeling in throat a few hrs after eating sushi or sashimi
- Anisakis try burrowing into tissue
- Acute GI pain, cramping, and vomiting
- Expelled w/o further symptoms (NO MAJOR SYMPTOMS)
Tape worm D. latum
- Great lakes region, Canada, Alaska
- Humans are DEFINITIVE hosts
- Lasting infection + damage
What to do if you like sushi:
- Reputable sushi bar: chef picks out larvae
- Have tuna + octopus (not so much); avoid salmon + halibut (more likely to have fish worms)
- Freeze fish for 5 days at -20 degrees C
45
Controlling Helminth infections (Prevention and Treatment)
Prevention - Sewage treatment:
- No human feces as fertilizers
- Water treatment
- No raw meat
Treatment: Chemo (2 mechs)
- Paralyze worms
- Interfere w/ metabolism (toxic to worms)
46
Ascariasis Treatment:
- Piperazine
- Pyrantel
- Mebendazole
47
Pinworm Treatment
- Piperazine
| - Pyrantel
48
Hookworm Treatment
- Piperazine
- Pyyrantel
- Mebendazole
- Thiabendazole
49
Trichinosis Treatment
- Pyrantel
- Mebendazole
- Thiabendazole
50
Trichuriasis (whipworm) Treatment
Mebendazole
51
Stronglyoidiasis Treatment
Thiabendazole
52
Guinea worm Treatment
Thiabendazole
53
Echinococciasis Treatment
Albendazole
54
Filariasis Treatment
-Diethylcarbamazine
55
Loiasis Treatment
Diethylcarbamazine
56
Schistosomiasis Treatment
- Niridazole
- Praziquantel
- Metrifonate
57
Tapeworm Treatment
Praziquantel
58
Other flukes Treatment
Praziquantel
