Parasitology Part 2 Flashcards
1
Q
Strongyloides stercoralis
A
- Eggs
- Eggs are oval and thin-shelled
- 50-58 um long by 30-34 um wide (a bit smaller than hookworm eggs)
- Strongyloidiasis
- Because of autoinfection, infection lifelong
- Generally controlled by cell mediated immunity
- Hyperinfection syndrome when disrupted
- HTLV, steroids, hematologic malignancy
- Little with HIV
- Clinical Features
- Frequently asymptomatic
- Dermatologic manifestations: Rash, larva currens, Migratory, serpiginous dermatitis
- Gastrointestinal symptoms: abdominal pain, diarrhea/ constipation
- Pulmonary symptoms
- Disseminated strongyloidiasis
- Blood eosinophilia
-
Hyperinfection syndrome
- immunosuppressed individual become Equilibrium is disturbed
- use of immunosuppressive drug
- The infection proliferates with large number of larvae being produced and found in every tissue of the body
- Gram-negative sepsis/ meningitis
- High mortality
- Laboratory Diagnosis
- Routine stool O+P examination
- Agar plate culture
- Nematode “culture”, Baermann, Harada Mori
- Stool exam
- Duodenal aspirate
- larvae
- In chronic infection, low worm output
- Serology
- ELISA based on soluble antigen from 3 rd stage S. stercoralis larva— Detects IgG
- Patients from endemic area about to become immunosuppressed
2
Q
*Enterobius vermicularis
(Pinworm)*
A
- Pinworm
- General
- Endemic throughout world
- Temperate zones
- Most common helminth in U.S.
- Adults 1 cm
- Lifespan 4 12 wks
- Migrate from cecum to anus to lay eggs
- Hatch in 6 hours
- Transfer to hands, bedclothes, dus
- Person person transmission
- Disease: enterobiasis
- Symptoms:
- Pruritis ani
- Irritability
- Insomnia
- Teeth grinding
- Abdominal pain
- Poor appetite, weight loss
- Nausea
- Pelvic inflammatory disease
- Diagnosis
- Finding characteristic eggs, scotch tape test
- Eggs not usually seen in stool (only 5 15%)
- One tape test 50% sensitive; 3=90%; 5=99%
- Perianal scrapings or swabs from under the fingernail
- Finding adult worms round the anus
3
Q
Trichuris trichiura
A
- Trichocephalus dispar or the human whipworm
- Cause trichuriasis
- Morphology
- Adults ~ 4cm
- Live in cecum, right colon
- Life expectancy 1 3 years
- Whip like head embeds in colonic wall
- Female produces 20,000 eggs/day
- Barrel shaped, plugs
- Infective after 2 4 weeks in soil
- Clinical Manifestations
- Light infections are asymptomatic
- Some have mild eosinophilia
- Some have Inflamed mucosa, tenesmus diarrhea, abdominal pain, Rectal prolapse
- Diagnosis
- Stool O&P
- Large number of eggs: diagnosed easily by O&P
6
Q
Nematodes: Overview
A
- Intestinal
- Enterobius
- Trichuris
- Ascaris
- Hookworms
- Strongyloides
7
Q
Ascaris lumbricoides
A
- General
- Most common human helminth
- Over ¼ world’s population infected
- Most asymptomatic
- Morbidity in 15% of infected
- Contributes to 60,000 deaths/year
- Largest intestinal nematode
- Adults 15-35 cm
- Reside mostly in jejunum
- 200,000 eggs/day/female
- Eggs passed to environment; become infective in 10 14days
- Best in warm, humid conditions
- Viable up to 6 years
- Eggs
- Fertilized egg
- are round
- have a thick shell with an external mammilla layer
- often stained golden brown by bile
- 45 75 µm long and 50 µm wide
- Unfertile eggs
- are elongated
- larger than fertile eggs
- up to 90 µm in length
- shell is thinner
- mammillated layer is more variable, either
with large protuberances or practically none
- Fertilized egg
- Clinical Disease
- incubation: 60 70 days
- pulmonary ascariasis (larva)
- intestinal ascariasis
- intestinal obstruction
- intestinal perforation
- adults migration
- Small proportion 2 weeks after infection:
- Cough
- Fever
- Eosinophilia
-
Larval lung migration
- The first passage of larvae through the liver and lungs usually elicit no symptoms
- Signs of pneumonitis if the number is large
- Reinfection and subsequent larval migration may lead to intense tissue reaction
- Even with a small number of larvae
- Ascaris pneumonitis
- Loeffler’s syndrome
- Charcot Leyden crystals
- Malnutrition in children, impaired
- Diagnosis
- Finding eggs in stool
- Passage of worms in stool
- Stool O&P
- Large number of eggs: diagnosed easily by O&P
- 60 70 micron
- Concentration not necessary
- Expelled adults
- Smooth, unsegmented, cream colored
- 15-35 cm
8
Q
Hookworms
A
- Ancylostoma duodenale and Necator americanus
- 900 million people infected
- N. americanus the predominant hookworm worldwide
- Disease
- Ground itch
- Eosinophilia
- develops 25-35 days after exposure
peaks:- 1 month (N. americanus)
- 2 months (A. duodenale)
- Transient Pneumonitis (less common
- Intestinal infection:
- Necrosis of the intestinal tissue
within the adult worm mouth - Blood loss by direct ingestion of blood by the worms and continues blood loss from original attachment sit
- Chronic infections:
- Both mental and physical retardation
- Necrosis of the intestinal tissue
- Laboratory Diagnosis
- eggs in stool: concentration, Kato katz method for helminth eggs
- larve –(culture), the Harada Mori method nematode larvae culture method
- Distribution
- Worldwide in areas with moist, warm climate
- N. americanus and A. duodenale are found in Africa, Asia and the Americas
- Necator americanus predominates the Americas and Australia
- Ancylostoma duodenale is found in Middle East, North Africa, and southern Europe
- Significant increase seen in Haiti
9
Q
Lymphatic Filariasis: Clinical
A
- Most infected persons asymptomatic
- • Clinical disease develops after repeated exposure, many years
- Acute adenolymphangitis
- Lymphedema
- Hydrocoele
- Elephantiasis
- Tropical Pulmonary
- Eosinophilia
10
Q
Lymphatic Filariasis: Diagnosis
A
- Clinical picture
- Ultrasound of lymphatics
- “Filarial Dance Sign”
- Thick smear for microfilaremia
- Giemsa, HE
- Midnight
- Lymphatic Filariasis: Serology
- Antigen testing (for bancroftian filariasis; not for brugian)
- Detects presence of worms
- Not necessarily live
- Available as ELISA and immunochromatographic test (ICT)
- High sensitivity and specificity
- •Antibody detection: utilizes a crude filarial extract
- Poor discrimination of the filariae
- Sensitive, but only fair specificity
- IgG4 more specific, correlates better with active infection
- IgG1 detects active or inactive infection, less specific
11
Q
Intestinal Cestodes
A
- Taenia saginata
- Taenia solium
- Echinococcus granulosus
- Hymenolepis nana
- Hymenolepis diminuta
- Dipylidium caninum
- Diphyllobothriam latum
- Phylum Platyhelminthes (flatworms)
- Segmented body
- Have intermediate and definitive hosts
- Localization digestive tract in humans and animals
- Tapeworms lack digestive tract; must absorb all required nutrients
- Human acquire infection by ingestion of infective larval stages in meat, fish, or insect
12
Q
Taenia sp.
A
- Cause taeniasis: infection in humans with
- Taenia saginata or Taenia solium
- Humans are definitive hosts
13
Q
Taenia saginata
A
- Beef tapeworm
- Length: 4-12 meters
- T. saginata : 13-20 branches in the proglottid
- Worldwide
- More common than T. solium particularly in the United States
- Disease
- Abdominal pain
- Weight loss
- Loss of appetite
- Nausea
- Diagnosis
Identification- Identification of eggs and/ or proglottids in feces
- Treatment
- PRAZIQUANTEL
- NICLOSAMIDE
- Epidemiology
- reservoir human, proglottids with eggs excreted
- wherever contaminated raw beef is eaten
- eating raw or undercooked beef is the primary risk factor for acquiring taeniasis
14
Q
Taenia solium
A
- Pork
- Length: 2-7 meters
- T. solium: 7-13 branches in proglottid
- Disease: taeniasis
- Asymptomatic
- Minor abdominal symptoms
- abdominal pain
- indigestion
- constipation
- Diagnosis
- Microscopic identification of eggs and proglottids in feces
- Repeated examination for light infections
- All Taenia species produce eggs that are identical
- Gravid proglottids or scolex allows species determination
- Serological tests for antibody detection
- Coproantigen detection (enzyme linked immunosorbant assay)
- Consultation with CDPH
- Cysticercosis
- determined by the larval form of Taenia solium in the human body
- ingestion of Taenia eggs
- autoinfection
- CNS
- Muscular tissue
- cellular subcutaneous tissue
- ocular
- cardiac
- pulmonar
- hepatic
- Cysticercosis Diagnosis
- X ray examination
- CT
- MRI
- CSF, enzyme linked immunoelectrotransfer blot (EITB)
- CDC does immunoblot for neurocysticercosis
- Diagnosis sometime depends on surgical removal of the parasit and microscopic examination for the presence of suckers and hooks on the scolex
- Fine needle aspirate
- Epidemiology
- Worldwide
15
Q
*Echinococcus granulosus
(Taenia echinococcus)*
A
- Definitive host: dog, wolf, other canids
- Intermediate host: sheep, goats, swine
- Hydatid Cysts Liver
- Hydatid sands
- Disease: Cystic Echinococcosis
- Usually asymptomatic for years
- >90% cysts in liver or lungs
- Rarely brain, bones, spleen, kidneys, heart
- Cyst leakage: anaphylaxis
- Progressive enlargement
- 1-5 cm/ year
- Biliary involvement
- Hydatid cyst evolution
- Calcification
- Complications after rupture of the cyst, anaphylactic shock and cyst dissemination
- Diagnosis
- X rays
- Ultrasound
- CT
- MRI
- Serologic test for confirmation
- Antibody detection
- CDC does ELISA and immunoblot
- Imaging
- Daughter cysts, protoscolices (“hydatid sand”); calcifications
- Cyst aspiration
- Echinococcosis: Treatment
- Surgery
- Recurrence 2 25%
- Routinely use
- ALBENDAZOLE
- MEBENDAZOLE
- Epidemiology
- Worldwide distribution
- Especially: Patagonia, Kenya, former Soviet republics, China, Mediterranean
- Communities involved in sheep farming: high prevalence
- Prevalent in rural areas
- Egg ingestion: accidental consumption of soil, water, or food that has been contaminated by the fecal matter of an infected dog
16
Q
Hymenolepis nana
A
- The dwarf tapeworm
- Length: 15 to 40 mm
- Small rounded scolex
- Disease: Hymenolepiasis
- Mostly asymptomatic
- Heavy infections cause weakness, dizziness, headaches, irritability, anorexia, abdominal pain, and diarrhea
- Eosinophilia
- Young children with heavy infections may have loose stools or even diarrhea containing mucus
- The eggs are infectious and unpreserved stools should be handled with caution
- Treatment
- PRAZIQUANTEL
- NICLOSAMIDE
- Epidemiology
- Highest prevalence among cestodes, 50 75 million people are infected worldwide
- fecal-oral transmission
- Most commonly seen in institutionalized children
- Adults can get infected
- Control
- Hygiene measures, sanitation, education
- Treatment of infected persons epidemics
17
Q
Hymenolepi diminuta
A
- H. diminuta infection
- Usually asymptomatic
- Heavy infections include diarrhea,anorexia, nausea, headache, and dizziness
- Most infections reported from children younger than 3 years
- Diagnosis
- Although adults can be passed spontaneously in the stool usually eggs are recovered and identified
- Differentiate eggs from those of H. nana
- Concentration techniques and repeated examinations for light infections
- Treatment
- PRAZIQUANTEL
- NICLOSAMIDE
- Epidemiology
- Worldwide distribution in normal hosts
- Reservoir rodents, rats with infected fleas
- Rare in humans
- Transmission: accidental ingestion of fleas
- From India, the former Soviet Union, Japan, Italy and certain areas of the southern United States
- (Tennessee, Georgia and texas)
- Commonly found in rats and mice
- Prevention and Control
- Rat control programs might decrease human exposure
- Insecticides
18
Q
Dipylidium caninum
A
- Fleas
- Disease: Dipylidiasis
- Mostly asymptomatic
- When symptoms are present:
- Abdominal pain
- diarrhea
- Allergic manifestations
- Anal pruritus
- Children indigestion and appetite loss
- Eosinophilia may also be present
- Diagnosis
- Finding the typical proglottids or egg packets in the stool or the environment
- Proglottids have
- 2 uterine pores, one on each sid
- Eggs
- Identification typical egg packets
- Egg packets can be squeezed from the proglottids for easier identification
- Macerate egg packets, adding a drop of saline, examining microscopically
- PRAZIQUANTEL
- NICLOSAMIDE
- Epidemiology
- Rare in humans, but worldwide distributed
- Transmission: accidental ingestion of dog fleas
- Dogs and cats, both domestic and wild
- Human infections in many areas of the world
- including
- United States
- Europe,
- Philippines
- China
- Japan
- Argentina
- Most infections have been in children
- Ingestion of intermediate hosts (fleas)
- contact with dog or cat
- Pets scraping across grass or carpeting
- Passage of proglottid in anal area, feces, diapers, carpet, furniture
- Prevention and Control
- Periodic treatment of dogs and cats and the use of flea powder
- Avoid contact of children with animals
19
Q
Diphyllobothrium latum
A
- Called the fish or broad tapeworm
- Largest human tapeworm
- Has a scolex with two bothria
- (sucking organs)
- Outbreaks reported from time to time
- 2 shallow grooves (bothria)
- Disease: Diphyllobothriasis
- Asymptomatic
- When symptoms present:
- Digestive manifestations
- Nervos manifestations
- Pernicious anemia
- Intestinal obstruction
- Diarrhea
- Abdominal pain
- headache
- dizziness
- weakness
- numbness,
- paresthesia,
- movement and coordination problems
- impairment of deep sensibilities
- Diagnosis
- Diagnosis identification of egg or proglottid
- Eggs are usually numerous and can be demonstrated without concentration techniques
- Treatment
- PRAZIQUANTEL
- NICLOSAMIDE
- Epidemiology
- reservoir definitive host (human)
- lakes with vegetation
- delta
- consuming undercooked fish with
- parasitic forms of D. latum
- Worldwide
- Areas of the world with a high incidence of
- infection:
- Baltic countries, Finland, Sweden
- Countries within the former USSR
- Tropical Africa (Uganda)
- Parts of Asia
- North America
- South America (Chile)
- Freshwater fish infected with Diphyllobothrium spp. larva may be transported to and consumed in geographic areas where active transmission does not occur
- Prevention and Control
- Adequately freezing or cooking fish will kill the parasite
- Do not eat raw or undercooked fish
- Detection and treatment of human cases
22
Q
Fasciola hepatica
A
- Sheep liver fluke
- Ingestion of aquatic plants, watercress
- Mint, parsley
- Prepatent period 3-4 months
- Egg
- Size: 130-150 µm long by 60-90 µm wide
- Opercular end
- Abopercular end
- Miracidia go into snail
- In snail
- sporocyst
- rediae
- cercariae(free swimming)
- Metacercariae on vegatation
- Pond Snail
- Disease
- Acute: fever, abdominal pain, migratory tracks through liver and abscesses, marked eosinophilia
- Lasts 2-4 months
- Heavy infection may lead to cholestasis when the bile cannot flow from the liver to the duodenum; hepatic atrophy and periportal cirrhosis
- Chronic: often subclinical
- cholangitis infection of the bile duct
- Biliary obstruction
- Acute: fever, abdominal pain, migratory tracks through liver and abscesses, marked eosinophilia
- Diagnosis
- Stool O&P, or eggs in bile ducts (not in acute phase)
- Serology sensitive, poor specificity
-
Epidemiology
- Worldwide distribution
- Common zoonotic hosts: cattle and sheep
- Highest known rates of human infection are in the Andean highlands of Bolivi (66%) and Peru (34%)
- Recent estimates:
- 2.4 million people in 61 countries infected
- 180 million at risk throughout the world
- Treatment
- Triclabendazole, 10 mg/kg (1-2 doses)
- 80-90% cure
- Bithionol 10-15 doses
- Frequent GI side effects
- Triclabendazole, 10 mg/kg (1-2 doses)
23
Q
Fasciolopsis buski
A
- The largest intestinal fluke of humans
- Adult has poorly developed oral and ventral suckers
- Fasciolopsis buski adult; approximate length = 50 mm
-
Eggs
- Size 130-150 µm long by 60-90 µm wide
- Operculum
-
Fasciolopsiasis
- Intestinal disturbances, gastric pain
- Severe diarrhea
- Nausea
- Bowel obstruction
- Eosinophilia and leukocytosis
- The adults inhabit the duodenum and jejunum
- Stools are profuse, yellow-green and contain increased amounts of undigested food (malabsorption process)
- Epidemiology
- Pigs a major reservoir
- East and SE Asia: India, China, Taiwan, Indonesia, Malaysia
- Treatment
- Praziquantel
- Thiabendazole
- Mebendazole
24
Q
Echinostomatidae
A
- E. hortense , E. macrorchis , E. revolutum , E. ilocanum and E. perfoliatum
- Many animals may serve as definitive hosts for various echinostome species, including aquatic birds, carnivores, rodents and humans
- Adults of Echinostoma spp. are much longer than wide and measure about 2-10 mm long by 1-2 mm
wide, depending on the species and are reddish gray - Small oral sucker
- Circumoral disk with a crown of spines
- Echinostomiasis Symptoms
- Light infections the patient may be asymptomatic and the adult worms cause only minor problems other than localized inflammation
- Heavy infections the worms can produce mild ulceration, diarrhea and abdominal pain
- Egg
- may range from 80-135 µm long by 55-80 µm wide
- They have an inconspicuous operculum and the abopercular end is often thickened.
- The larger eggs are very similar to Fasciola and Fasciolopsis .
- Eggs are passed unembryonated in feces. Adults are needed for a definitive diagnosis
- Echinostoma Prevention
- Both rats and dogs have been found to be infected in areas where infection is endemic
- Cook mollusks and restrict night soil for fertilizer
25
Q
Clonorchis
A
- Liver flukes
- Cause similar disease; differ mainly in distribution
- Prevalence can be 20-80% in endemic areas
- Clonorchis sinensis
- The adult flukes (measure 10 to 25 mm by 3 to 5 mm)
- Clonorchis sinensis eggs
- eggs range in size from 27 to 35 µm by 11 to 20 µm
- Eggs are oval-shaped with a thick, pale brownish-yellow shell and distinct opercular shoulders surrounding the operculum
- At the opposite (larger, abopercular) end, a small knob or hook-like protrusion is often visible
- EPI
- Humans become infected by ingesting the metacercariae in undercooked, salted, pickled, or smoked freshwater fish
- Endemic to East Asia 30 millions infected
- Prevalence:
- 2% Korea
- 50% Taiwan
- China: up to 55% (Guangxi)
26
Q
Opisthorchis
A
- Opisthorchiasis associated biliary stones
- Opisthorchis viverrini (Southeast Asian liver)
- 5 mm to 10 mm x 1 mm 2 mm
- Opisthorchis felineus (cat liver fluke)
- 7 mm-12 mm x 2 mm 3 mm
- Adults reside in the bile ducts of the definitive host
- Adults are transparent and leaf shaped
- Adults are similar but often smaller than Clonorchis sinensis
- Eggs
- 19-30 µm long by 10 20 µm wide wet mount concentrated stool
- Life cycle in snails 1st intermediate host ( Bithynia and Cordiella)
- Life cycle in freshwater fish 2nd intermediate host
- The mammalian definitive host (cats, dogs, and various fish eating mammals including humans) become infected by ingesting undercooked, smoked, pickled, salted or dried fish containing metacercariae
- EPI
- O. felineus : northern Europe and Asia (former Soviet Union)
- O. viverrini : Southeast Asia.
- Thailand 25%
- Laos 40 80%
- Opistorchis spp. Prevention
- Prevent defecation in or near ponds or lakes
- Don’t mix untreated night soil with any other soil or store near animal food supplies
- Cook fish well
- Clonorchis and Opisthorchis Disease
- Acute infection:
- fever, hepatomegaly, eosinophilia
- Chronic infection: often asymptomatic
- Fatigue, abdominal pain
- Biliary obstruction
- Pigment stones
- Ascending cholangitis
- Cholangiocarcinoma
- 5x 15x risk compared to controls
- Diagnosis:
- Stool O&P
- Ultrasound: cystic dilation of intrahepatic ducts
- Pathology
- Antibody tests exist, but not available in U.S.
- Sensitive, but not specific
- Antibodies persist for years
- Treatment
- Three doses praziquantel 25 mg/kg (in one day)
- High cure rates
27
Q
Heterophyes heterophyes
A
- Adult Measures 1-2 mm in length by 0.3-0.4 in width and have a broadly round posterior end
- The surface of the worm is covered with minute spines
- Eggs
- are indistinguishable from those of Metagonimus yokogawai and resemble those of Clonorchis and Opisthorchis
- Examination of purged adult worms
- Heterophyiasis Symptoms
- Little damage to the GI tract mucosa except for a mild inflammatory reaction
- Heavy infections worms cause abdominal pain, mucous diarrhea, and ulceration of the intestinal wall
- Eggs may provoke pathologic lesions, particularly in the heart and brain
- Neurological symptoms due to adult worms or eggs in the brain have been reported
- EPI
- Acquired through the ingestion of pickled or uncooked/ raw fish
- Can infect birds and mammals
- China, Egypt, India, Iran, Israel, Japan, Korea, Sudan, Taiwan, the Philippines, Tunisia and Turkey
28
Q
Metagonimus yokogawai
A
- minute intestinal fluke, the smallest human fluke
- Diagnosis on the basis of clinical findings, patient history, or recovery of adult worms after therapy or at autopsy
- Metagonimiasis Symptoms
- Depend largely on worm burden of the host
- Symptoms are diarrhea and colicky abdominal pain
- Eggs infiltrate into the intestinal capillaries and lymphatics and are carried to the myocardium, brain spinal cord, and other tissues where emboli or granulomatous reactions may occur
- Migration of the eggs to extraintestinal sites (heart, brain) can occur, with resulting symptoms
- Metagonimiasis Diagnosis
- Microscopic identification of eggs (26-28 µm by 15 17 µm) in the stool
- Formalin ethyl acetate sedimentation concentration
- Metagonimiasis Epidemiology
- Far East, as well as Siberia, Manchuria, the Balkan states, Israel, and Spain
- Human infections outside endemic areas may result from ingesting pickled fish or sushi made from fish imported from endemic areas
- Metagonimiasis Prevention
- control intermediate host (snails) by use of molluscidals
- education to ensure all people fully cook all fish
- implementing sanitary water conditions would reduce the continual reintroduction of eggs to water sources
29
Q
Paragonimus spp
A
- Lung fluke
- Snail then crustacean then human
- Cause paragonimiasis or pulmonary distomatosis, acquired through ingestion of raw or undercooked crabs or
crayfish, is usually a lung infection - Adults Size
- range 8 to 16 mm by 4 to 8 mm.
- The adult worm is a plump, ovoid, reddish
- Paragonimus westermani
- P. philippinensis
- P. africanum
- P. kellicotti
- P. mexicanus
- Adults possess oral and ventral suckers
- Paragonimus Egg
- Eggs are yellowish-brown, 80-120 µm long by 45-70 µm wide, thick-shelled, with an operculum
- P. kellicotti has been acquired in the United States, with multiple cases from the Midwest.
- Several cases have been associated with ingestion of uncooked crawfish during river raft float trips in Missouri
- Paragonimiasis
- 2-15 day incubation
- Acute (in minority):
- Diarrhea/ abdominal pain followed by
- Fever, pulmonary symptoms: dyspnea, chest pain and bronchitis
- Eosinophilia
- Chronic symptoms
- Cough, brown sputum
- Chronic bronchitis/ bronchiectasis
- Cysts, nodules, cavities, pleural effusions
- confused with TB
- CNS: headaches, seizures, visual disturbances,
meningitis, mass lesions
- Diagnosis:
- O&P stool, sputum
- Microscopic demonstration of eggs in sputum or stool on different days as a result of
coughed up eggs that are swallowed - Eggs are also occasionally encountered in pleural effusion fluid or biopsy material
- Complement fixation antibody test
- Sensitive, but nonspecific
- Becomes negative 6 12 months after cure
- ELISA
- 90% sensitive and specific
- Takes 4 24 months to become positive after
infection, longer to normalize after cure
- EPI
- Endemic mostly to Asia
- Prevalence: China, Korea, Philippines, Japan, Vietnam, Taiwan, and Thailand
- Also equatorial Africa, Peru, Equador
- 20 million cases worldwide
- 293 million at risk
- Acquired via undercooked crustaceans
- Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P. westermani
- Treatment
- Three doses praziquantel 25 mg/kg (in one day)
- High cure rates
- Prevention
- Never eat raw freshwater crabs or crayfish Cook crabs and crayfish to at least 145 F (~63 C)
- Travelers should be advised to avoid traditional meals containing undercooked freshwater crustaceans
30
Q
Schistosoma mansoni
A
- Liver
- Require definitive and intermediate hosts for life cycles
- Human is definitive host for
- S. mansoni, S. japonicum, S. haematobium, S. mekongi , S. malayensis and S. intercalatum
- S. mattheei causes infections in
- sheep, cattle and horses; also infects humans and can cause disease
- Differ from other trematodes in
- Live in the blood vessels
- Have nonoperculated eggs
- Sexes of adults separate
- Transmission by skin penetration
-
(Bilharzia, Bilharziosis or Snail)
- Afflicts >200 million worldwide
- Significant cause of disease in endemic areas
- Acquired by (intact) skin contact with infected fresh water
- Mostly in tropics, areas of poor sanitation
- Bifurcate Cercaria
- Adult Worms
- Male worms are robust, tuberculate and measure 6 12 mm in length.
- Females are longer, 7 17 mm in length, and slender
- Schistosoma mansoni Eggs
- 114 to 180 µm long by 45-70 µm wide
- Schistosoma mansoni Symptoms
- Symptoms are related to stages, previous host exposure worm burden and host response
- Include:
- Cercarial dermatitis
- skin penetration and reaction
- Cercarial dermatitis
- Acute schistosomiasis (Katayama fever )
- Associated with heavy primary infections and the initiation of egg production
- Similar to serum sickness
- High fever, hepatosplenomegaly, lymphadenopahty, eosinophilia and dysentery
- Not well understood or common
- Passage of eggs through wall of intestine can produce fever, abdominal pain, liver tenderness,
urticaria and general malaise - Immune response to antigenic substances released by egg
- Include:
-
31
Q
Schistosoma haematobium
A
- Urine!
- 110-170 µm long by 40-70 µm wide
- Conspicuous terminal spine
- Eggs contain mature miracidium when shed in urine
- Humans only significant reservoir hosts
- Naturally infects monkeys, baboons, and chimpanzees
- Pathology of S. haematobium schistosomiasis includes:
- Hematuria
- Scarring
- Calcification
- Squamous cell carcinoma
- Occasional embolic egg
- granulomas in brain or spinal cord
32
Q
S. intercalatum
A
- Eggs are similar to S. haematobium in general, shape and in possessing a terminal spine,
- but are usually longer (140 240 µm), often have an equatorial (central) bulge and are shed in stool, not urine
33
Q
Schistosoma japonicum
A
- Eggs are large and more rounded than other species
- 70-100 um long by 50-65 µm wide
- The spine is smaller and less conspicuous than other species
- Spine may be absent
- Eggs are shed in stool, sometimes urine
- Far East, including China, Indonesia, Japan, and the Philippines
- Many reservoir hosts (cats, cattle, dogs goats, horses, sheep, pigs, mice, rats and water buffaloes) are naturally infected
- Night soil issues
34
Q
Schistosoma mekongi
A
- Infections occur in the Mekong River basin in Cambodia, Laos, and Thailand
- Dogs and rodents harbor the infection
- Eggs similar to S. japonicum but smaller with a range of 50-80 µm by 40-65 µm
- Lateral Spine!
35
Q
Early Schistosomiasis
A
- Pruritic, papular rash hrs 1 day after exposure (diff. from swimmer’s itch): cercarial dermatitis
- More common in previously exposed
- Acute/ toxemic schisto in some: Katayama Fever S. japonicum > S. mansoni
- 2-8 wks after infection (in previously unexposed)
- Fever, headache, generalized myalgias, nausea, abdominal pain, hematuria, hepatosplenomegaly, diarrhea, cough, rash
- Eosinophilia
- Rare with S. haematobium
- Rarely: CNS involvement
- S. mansoni : transverse myelitis
- S. japonicum : cerebral mass lesions
36
Q
Chronic Schistosomiasis
A
- Sequelae related to worm burden, duration of exposure
- Immune reaction to eggs
- Adult lifespan averages 3-7 years
- Egg production:
- 300/day ( S. mansoni ) vs. 3,000/day ( S. japonicum
- Mainly in natives of endemic areas(vs. tourists or expats)
- Likely contributes to anemia, growth retardation in children in endemic areas
- Chronic GI schisto (S. mansoni, S. japonicum
- Abd pain, diarrhea/ constipation, hepatic fibrosis (Symmer’s or “pipe stem”), hepatosplenomegaly, portal HTN
- Liver failure rare
- Chronic urinary schisto ( S. haematobium)
- Hematuria, dysuria, strictures
- Bladder cancer
38
Q
Helminth Eggs Chart
A
