Vector Borne Helminth Infections and Schistosomiasis Flashcards
Nematoda, Cestoda, and trematoda
Roundworms, tapeworms, flukes
Themes in helminth infections
Long ter mand chronic
ANy type of host
All life cycle stages can cause symptoms
Host response is responsble for symtoms
Host responses to helminths
Lots of morbidity but little mortality
Th2 like response
IgE with eosinophilia and mast cell responses
Wuchereria bancrofti and brugia malayi vector and dz
mosquito and lymphatic filariasis
Loa loa
Onchocerca volvulus
Dirofilaria immitis
Vectors and dz
Crysops fly - loasis
Simulium fly - river blindness
Mosquito - canine heartworm
Lymphatic filariasis transmission
Any kind of mosquito…anopheles, culex, aedes
Anopheles and culex bite at night while aedes bites in day
Lymphatic filariasis infeciton process
MF (microfilariae) develop in the mosquito and migrate outside of the surface of the proboscis…migrate in from the skin to the blood to the lymph tissue
Live 5-10 years and are viviparous (no egges)
Timing and release of MF
Synchronized with biting habits…anopheles and culex in lymph nodes release MF at night
Some people develop elephantitis, most do not
Pregression of lymphatic filariasis
Larvae mature in lymph nodes for 6 months to a year…migrate to lymph nodes in lower extremities like legs, groin, genitalia…can remain paired for 5-40 years…fever may be present and then recurrent lymphedema due to worms lodged in lymphatic system
If adult worms die, huge immune response that results in formation of granulomas that become fibrotic, blocking vessels and causing localized damage
Elephantiasis
Giant swelling of organs or tissues triggered by lymph entering the tissue causing prolif of tissue and skin in localized manner
Men can get ____ with lymphatic filariasis
Orchitis with hydrocele (enlargement of the scrotum)
Tx of lymphatic filariasis
Focus on controlling MF grwoth Piperizine derivatives (diethylcarbamazine DEC) is a prophlyactic for mass tx...paralyzes MF and then cleared by liver...potential allergic side effects cause anaphylaxis in some cases
Ivermectin/mebendazole can work
Surgical
Strategies to control filarial dz
Control of contact with vectors
Detect with periodic blood smears
Periodic admin of DEC to both symptomatic and asymptomatic patients
Loa loa
Transmitted by chrysops biting fly
Slow developing dz
Loa loa life cycle
MF enter fly bite during blood meal…develop into adults (1-4 years)…migrate through tissue and release MF…live worms and MF do NOT elicit a significant immune response of cause severe pathology in loa loa
Migration of loa loa
Occurs subcutaneously
Generally painless but can be felt on bridge of nose, conjunctiva and eyelid
Calabar swelling can occur - severe angioedema
Liver worms elicit minor pathology than dead
Dead elicit huge eosinophilic response
Ocular involvement of loa loa
Cause ocular filariasis - release MF which interfere with cornea and retina
Must be removed surgically
Detection, tx, and periods of loa loa
Detect MF, highest levels are midday…can detect ocular with slit lamp
DEC kills MF and immature stages but not adults (be careful with dose)…ivermectin and mebendazole can also be used
Adult worms must be removed during transit through eye
Incubation - 2-12 months
Prepatent - 6 mos -4 years
Patent - 4-17 years
Onchocerca volvulus
Transmitted by simulium of black flies
Only females
Transmit 3rd stage larvae (L3) or MF
Repeated infections can cause progressive blindness
Progression of onchocerca volvulus
MF migrate through skin maturing for about a year…slow migration results in nodules…worms mate and produce MF which migrate to skin and eye…MF taken back up by simulium flies
Symptoms of onchocerca volvulus
Cutaneous - papular dermatitis (craw craw), thickening of skin (sowda), changes in pigmentation…also elephantiasis
Ocular - mostly from dead MF…keratitis…chroioretian ldamage in anterior chamber of the eye…inflam damage to optic nerve and retina
Diagnosis and tx of onchocerca
Skin snips from nodules
Slit lamp of anterior chamber
Sclerocorneal punch biopsy
Rarely detectable in blood
DEC (could worsen cutaneous symptoms), Ivermectin, surgery
Treamtodes
Leaf or oval shaped Blind alimentary canal Locomotion by muscle movement Adults pair for life Use snails as IM hosts
Schistosomiasis stages
Eggs are released in partially matured state…mature in bodies of water and release miracidia…miracidia infect snail and form sporocyst within which thousands of cercariae are formed…cercariae are released from snail to water and infect the human…mature in humans to adults and form mating pairs
Schistosomiasis structure and cause of pathology
Female in the gynocophorous canal of the male
Eggs responsbile for pathology caused by worms
Life cycle of schistosomiais in humans
Cercariae burrow in skin or swallowed…intesstinal migrate to mesenteric veins…urinary migrate to pelvic veins…eggs are shed
At site of infection
Maculopapular rash in hours-week
Intestinal schistosomiasis
Acute - takes 14-84 days
Fever, headache, hepatomegaly, bloody diarrhea, S mansoni can have resp syndromes
Eosinophilia
Symptoms coincide with depositon of eggs
Chronic intestinal schistosomiasis
Immune response to eggs and granuloma formation
Force eggs into the lumen of the boewel
Maximal granuloma at intestine and following portal circulation, the liver
Hypogastric pain with blood in the stool, diarrhea and constipation…colon cancer symptoms
Liver fibrosis promoting hepatomegaly…postal hypertension, anemia, and ascites due to liver damage
Urogenital schistosomiasis
Initial symptom in hematouria Increased proteourea Granulomas in the bladder Obstruction of ureters Renal colic and failure Women can get female genital schistosomiasis as ulcertive, hypertrophic lesions on the vulva and perineum (also from intestinal)
Pulmonary schisto
Escape of eggs to lungs leads to pulmonary hypertension and cardiac hypertrophy
CNS shisto
S japaniocum can impair blood flow
Childhood schisto
Anemia, growth and reatardation
Intestinal schisto vs. urinary times
Intestinal has patent period of 25 years, uro only 25 weeks
Tx of schisto
Praziquantel and tetrahydroquinolones
Microbilharzaria variglandis
Cercarial dermatitis caused by schisto in lakes and ponds
Dead end host
Rash, itching, localized edema
Topical corticosteroids and antihistamines
other flukes
Liver
Lung
Intestinal
