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IAHI Block 1 > Parasitology > Flashcards

Flashcards in Parasitology Deck (37):
1

Symbiosis

A relationship of distinct organisms in close association with one another

2

Mutualism:
Commensal:
Parasitism:

Mutualism: Benefits both
Commensal: Benefits one and neutral for the other
Parasitism: Benefits one and harfmul for the other (parasite vs host)

3

Human parasites are divided into:

Endo (infection inside the body)
Ecto (Infestation or within skin)

4

Endoparasites are divided into:

Protozoan (unicellular)
Helminths (multicellular worms)

5

Parasite (Biological Definition)

An organism that grows, feeds, and is sheltered on or in a host organism to the detriment of that host

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Definitive Host

Host in which the sexual stage of a parasite life cycle occurs

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Intermediate Host

Host in which asexual reproduction or development occurs

8

Incidental Host

Host is not an obligate part of parasite life cycle

9

Reservoir Host

Animal hosts that maintain the natural cycle in the wild - often are not really harmed by carriage

10

Vector Host

A host species that transmits an infections form of the parasite to another host species

11

Worldwide parasitology prevalence of Malaria

300-500 million cases per year
655,000 deaths, mostly children

12

Prevalent parasitologies

Malaria
Leishmaniasis
Chaga's disease
Schistosomiasis
Lymphatic Filariasis
Ascariasis

13

The 6 Kingdoms

Eubacteria
Archeobacteria
Protista
Fungi
Plantae
Animalia

14

Cyst

Dormant stage of parasite, found encysted in host (intermediate or definitive)

15

Cyst, Hydatid

Specialized cysitcercal form of the cestode Echinococcus granulosus - found in the intermediate host

16

Larvae alternative names

Metacercaria
Miracidium
Microfilariae
Cercaria
Filariform
Rhabditiform
Schistosomula
Sporocyst

17

Class Cestoda

- Tapeworms; flattened segmented bodies
- NO internal digestive system; nutrients absorbed across cuticle
- Adults attach by anterior end (scolex) to the gut wall of definitive host
- Segments (proglottids) mature from anterior to posterior; specialized for reproduction
- Transmission by ingestion of larval cysticerci or eggs

18

Class Trematoda

- Flukes of the lungs, liver and blood
- Broad flattened bodies with a simple digestive system; a single opening serves as mouth and anus
- One or more intermediate hosts, one of which is a snail
- Transmission can be invasive or injestive

19

Tapeworms associated with:
1) Raw Beef
2) Raw Pork
3) Eggs
4) Undercooked fish

1) Taenia saginata (intestinal)
2) Taenia solium (Intestinal/lung)
3) Echinococcus granulosus (liver,lungs)
4) Diphyllobothrium (intestinal)

20

Schistosoma spp. (Trematoda)

Located in veins to gut/bladder
Cercaria penetrate skin

21

Pork tapeworm: Taenia solium
Location:
Definitive Host:
Intermediate Host:
Transmission:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Adults - Intestine; Cysticerci - any tissue
Definitive Host: Humans
Intermediate Host: Pigs or humans
Transmission: Ingestion
Pathology: Abdominal discomfort, occasionally nausea, vomiting, diarrhea, weight loss and obstruction; Cysticercosis can affect brain functioning
Diagnosis:Self; active proglottids
Immunity: Humoral response to adult worms
Treatment: Praziquantel/ Dexamethasone
Prevention: Good public and personal hygiene

22

Diphyllobothrium latum: Fish tapeworm
Location:
Definitive Host:
Intermediate Host:
Transmission:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Lumenal, intestinal
Definitive Host: Humans
Intermediate Host: Copepod that infects fish
Transmission: Ingestion
Pathology: Adults absorb 80-100% dietary B12; anemia
Diagnosis: Active proglottids (eggs in feces)
Immunity: None
Treatment: Praziquantel; B12 supplement
Prevention: Good public hygiene

23

Echinococcosis: tapeworm Echinococcus
Location:
Definitive Host:
Intermediate Host:
Transmission:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Tissues mainly lungs and liver, but also spleen, kidneys, heart, bone and CNS
Definitive Host: Wild and domestic canines
Intermediate Host:Wild and domestic ungulates (hoofed animals); humans
Transmission: Ingestion of eggs from dogs
Pathology: Hyatid cysts in liver (50-70%) and lungs (20-30%) but also spleen kidney, bone and CNS; releases protoscolices; anaphylaxis
Diagnosis: CAT scan; presents as slow growing tumor; Serology used for confirmation
Immunity: Circulating antibodies to hydatid cyst antigens
Treatment: Percutaneous drainage with instillagion of hypertonic saline or alcohol; surgical removal; albendazole
Prevention:

24

Schistosomiasis (Blood Flukes) - 3 types

1) Schistosoma mansoni - inferior mesenteric veins
2) Schistosoma joponicum - superior mesenteric veins
3) Schistosoma haematobium - venous plexus (bladder)

25

Schistosomiasis
Location:
Definitive Host:
Intermediate Host:
Transmission:
Epidemiology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Eggs migrate to descending colon, small intestine, bladder
Definitive Host: Humans
Intermediate Host: Snails
Transmission: Invasive, aquatic cercaria penetrate skin
Epidemiology: 240 million infected globally - contaminated water supply
Diagnosis: Observation of eggs in feces or urine; serology
Immunity: Adults masked by absorption of host serum proteins
Treatment: Praziquantel in single or multiple doses potentiates active immune system killing of worms
Prevention: Reduce source, control intermediate hosts; avoid contact with infested water

26

Schistosomiasis Pathology

Early (0-2 wks): Rash from invading cercaria; fever headache nausea as they migrate
Middle (1-2 months): Symptoms from immune response to eggs, intense fever with onset of oviposition; Katayama syndrome
Chronic (5-15 years): Severe liver disease; portal hypertension; fibrosis of bladder

27

Schistosome mating

Male and female are attached
Male takes in nutrients
Female produces eggs

28

Pathogenic types of Nematoda (round worm)

1) Lumenal - intestinal/anal/colon
2) Hookworm - intestinal soil
3) Tissue Worm - muscle/blood/tissue

29

Pinworm
Location:
Definitive Host:
Intermediate Host:
Transmission:
Pathology:
Diagnosis:
Immunity:
Treatment:
Epidemiology:

Location: Adults in colon
Definitive Host: Humans
Intermediate Host: n/a
Transmission: Ingestion of eggs, direct person to person
Pathology: Intense perianal pruritis (itchy skin); Urogenital invasion in females can lead to bacterial infection; psychological trauma
Diagnosis: Persistent perianal itch, restlessness, insomnia
Immunity: none
Treatment: Pyrantel pamoate, mebendazole, albendazole
Epidemiology: Prevalent in children, day care centers

30

Whipworm
Location:
Definitive Host:
Intermediate Host:
Transmission:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Adults attach to colonic mucosa
Definitive Host: Humans only
Intermediate Host: n/a
Transmission: Ingestion of embryonated eggs
Pathology: Low: usually none; High: Disrupted colonic mucosa, bloody stool, prolapse, anemia; heavy - impaired growth in children
Diagnosis: Only by eggs in stool
Immunity: Acquired immunity in natural infections
Treatment: 3 days of ivermectin, mebendazole or albendazole
Prevention: Good personal and public hygiene

31

Ascariasis
Location:
Definitive Host:
Transmission:
Epidemiology:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Adults free in upper intestine
Definitive Host: Humans
Transmission: Ingestion of eggs from soil
Epidemiology: 25% of people infected worldwide - considered a US NDP (Neglected disease of poverty)
Pathology: Heavy worm loads can lead to intestinal obstruction; stressed worms migrate to nose, ear, peritoneal
Diagnosis: Eggs in stool
Immunity: Allergic inflammation from larval migration through lungs
Treatment: Mebendazole, albendazole or iermectin
Prevention: Good personal and public hygiene

32

Hookworms
Location:
Definitive Host:
Transmission:
Epidemiology:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Small intestine
Definitive Host: Humans
Transmission: Invasive of skin in contact with soil
Epidemiology: US-NDP, poor public sanitation, children and farmers with no shoes
Pathology: Pruritis at penetration sites; heavy infection, larval migration through lungs can cause bronchitis; Exsanguination
Diagnosis: Anemia; confirmed by eggs in stool
Immunity: Asthmatic pathology with repeated infection
Treatment: Pyrantel pamoate, albendazole and mebendazole
Prevention: Good public hygiene, shoes

33

Strongyloides
Location:
Definitive Host:
Transmission:
Epidemiology:
Pathology:
Diagnosis:
Immunity:
Treatment:
Prevention:

Location: Small intestine
Definitive Host: Humans
Transmission: Filariform larvae penetrates skin
Epidemiology: US-NDP, up to 100,000 infections in the US; autoinfection can result in long-term infection
Pathology: Pulmonary manifestation, high burden leads to chronic intestinal malabsorption, rashes due to autoinfection - can lead to immunosuppression and hyperinfection that can be fatal
Diagnosis: Larvae in stool or sputum; serology
Immunity: Asthmatic pathology with repeated infection
Treatment: Treat all cases ivermectin 1st choice thiabenazole 2nd choice
Prevention: Good public/personal hygeine; wear shoes

34

3 Alternative Life cycles of Strongyloides

Direct: Like hookworms: Invade skin goes to circulation then lodges in lungs; coughed up and swallowed, matures in intestine
Indirect: Sexual reproduction in soil
Autoinfection: Larvae mature in host, enter through colonic mucosa or perianal skin

35

Diagnostic staining and culture procedures for Strongyloides

1) Wet mount of stool
2) Human fecal smear stained with auramine O
3) Agar plate culture method
4) Gram staining of a sputum

36

Trichinosis
Location:
Definitive Host:
Incidental Host:
Transmission:
Epidemiology:
Pathology:
Diagnosis:
Treatment:
Prevention:

Location: Adults in intestine; larvae in muscle
Definitive Host: Meat eating mammals
Incidental Host: Humans are dead end hosts
Transmission: Raw/undercooked meat (pork)
Epidemiology: Developed world, home-made sausage; Hunting (Inuits)
Pathology: Mild pathology from adult worms (nausea, cramps); Inflammation around individual cyst; Severe symptoms - fever, neural dysfunction, conjunctivitis
Diagnosis: Eosinophilia, periorbital edema, myositis, fever - serology > 3 weeks after infection
Treatment: Mebendazole or albendazole
Prevention: Cook food

37

Toxocariasis
Location:
Definitive Host:
Incidental Host:
Transmission:
Epidemiology:
Pathology:
Diagnosis:
Immunology:
Treatment:
Prevention:

Location: In dogs, adult worms free in upper intestine of dog; In humans, larva can be found in any tissue
Definitive Host: Dogs
Incidental Host: Humans
Transmission: Ingestion of embryonated eggs from soil
Epidemiology: More commonly in warmer climates
Pathology: Heavy worm loads can lead to necrosis in any location; enlarged liver, pulmonary complications
Immunology: Asthmatic and immune hypersensitivity common
Diagnosis: ELISA for larval antigens, but can cross with Ascaris
Treatment: Sever cases only, albendazole or mebendazole
Prevention: Disposal of dog waste