Parasitology Exam 3: Microfilariae Flashcards
What are microfilaria?
Roundworms (nematodes) that infect blood/tissue in humans
How are microfilaria transmitted?
Blood-sucking arthropod vector (mosquito, midge, fly)
How are microfilaria identified?
Morphology of microfilaria, define circadian rhythm, and location within human host
What are the blood and tissue microfilaria that infect humans?
W. bancrofti
B. malayi
Loa loa
O. volvulus
Mansonella spp.
Dirofilaria spp.
How is Wuchereria bancrofti transmitted?
Via mosquito bite from Anopheles, Aedes, or Culex fatigans
Morphology of Wuchereria bancrofti adult worm
Has a sheath
NO nuclei present in end of tail
What is the most commonly identified species of filarial worms that infects humans?
W. bancrofti
What disease does W. bancrofti cause?
Bancroftian filariasis and elephantiasis including hydrocele, chyluria, tropical pulmonary eosinophilia
What is hydrocele?
Fluid-filled sac within the scrotum
What is chyluria?
Milky white urine due to obstruction of lymphatic vessels
What is an endosymbiont?
Bacteria (Wolbachia) required for larval development of certain microfilaria (W. bancrofti, Brugia spp., and Onchocerca volvulus)
Wolbachi
Endosymbiont, obligate intracellular organism
What is Knott concentration?
Used to recover small numbers of microfilaria in the blood, centrifugation is used to concentrate organisms onto a slide
Describe the morphology of Brugia malayi
Has a sheath that stains BRIGHT PINK
2 terminal nuclei in tail
How is Brugia malayi transmitted?
Mosquito (Anopheles or Mansonia)
Which microfilaria is distributed throughout the Far East?
Brugia malayi
Differentiate between the 2 periodic forms of Brugia malayi
Nocturnal form - located near rice fields (most common)
Nonperiodic form - located near swampy forests
Describe the disease presentation of Brugia malayi
Essentially same as W. bancrofti (Elephantiasis, lymphadema)
EXCEPT no hydrocele or chyluria
Lab ID of brugia malayi?
ID of microfilariae in blood
What is another name for Loa loa?
The eye worm
What is the vector of Loa loa?
Deer fly (Chrysops spp)
What is the diurnal periodicity of loa loa?
Peak numbers of worms in blood between 12pm and 2pm
What is the disease presentation of Loa loa?
Calabar swellings
- Localized area of angioedema in response to production of parasitic metabolic products
Involves swelling of the eye area
Describe morphology of Loa loa
Have a sheath (unstained)
Nuclei extend through the tip of the tail
Describe the morphology of Onchocerca volvulus
NO sheath!
NO nuclei into tip of tail!
Vector of Onchocerca volvulus
Black fly (Simulium spp)
Disease presentation of Onchocerca volvulus
River Blindness
- Skin infections
- Lymph node infections
- Eye infections that can lead to blindness
Lab ID of onchocerca volvulus
ID of microfiliarie in tissue
What is the vector/transmissioon of Mansonella spp?
Biting midges (Culicoides)
Where are the different species of Mansonella spp found?
M. streptocerca
M. perstans
M. ozzardi
M. streptocerca: skin
M. perstans: pericardial, pleural, and peritoneal cavities
M. ozzardi: unknown
Lab ID of Mansonella spp?
ID of microfilaria in blood/body fluids
Morphology of M. streptocerca
NO sheath
Nuclei extend to tip of tail
Shepherd’s crook
Morphology of M. perstans
NO sheath
Nuclei extend to tip of tail
Morphology of M. ozzardi
NO sheath
Nuclei do NOT extend to tip of tail
What is the main organism of Dirofilaria spp and what does it cause?
D. immitis
Causes heartworm in dogs and wild canids
Definitive host of D. immitis
Dogs and wild canids
Dead-end host of D. immitis
Humans
Lab ID of Dirofilaria immitis
Examination of inflammatory lung tissue or skin nodule
Worm’s cuticle contains chitin which is visualized with calcofluor white stain
