5) Nematode Eggs and Larvae

genus and species?

Trichuris trichiura (egg)

characteristics of Trichuris trichiura (egg)?

symmetrical barrel shape

plugs on each end

embryonation requires 2 weeks

developmental stage?

Trichuris trichiura (egg)

genus and species?

Trichinella spiralis (adult in intestinal mucosa)?

characteristics of

Trichinella spiralis (adult in intestinal mucosa)?

b. posterior end of male showing pseudobursae and papillae

c. adult female w/ L1s.

d. larvae in muscle

e. thick collagen capsule (C)

developmental stage?

Trichinella spiralis (adult larvae in intestinal mucosa)

genus and species?

Necator americanus (hookworm eggs)

characteristics of

Necator americanus (hookworm eggs)?

embryo surrounded by thin shell

developmental stage?

Necator americanus (hookworm eggs)

genus and species?

Rhabditiform vs. filariform larvae

characteristics of Rhabditiform vs. filariform larvae?

a. anterior end of rhabditiform (L1) hookworm larvae

corpus (C)

isthmus (I)

end bulb (E)

b. large buccal capsule (BC)

c. filariform (L3)

• no isthmus, but end bulb (E) present

• nerve ring (arrow)

  • infective larval stage

developmental stage?

Rhabditiform vs. filariform larvae

genus and species?

Ascaris lumbricoides (eggs)

characteristics of

Ascaris lumbricoides (eggs)?

outermost shell = proteinaceous and bumpy

uncleaved embryo in feces

L3 in 2-6 weeks

can appear smooth

developmental stage?

Ascaris lumbricoides (eggs)

genus and species?

Ascaris lumbricoides (larvae in lungs)

characteristics of

Ascaris lumbricoides (larvae in lungs)?

Larva (arrow) breaking into alveolus

b. Bronchus w/ inflammatory cells, and larvae (arrow) traveling up to pharynx

developmental stage?

Ascaris lumbricoides (larvae in lungs)

genus and species?

Toxocara canis (embryonated eggs)

characteristics of

Toxocara canis (embryonated eggs)?

golf ball like

contains L3

doesnt develop into adults in humans, only dogs

developmental stage?

Toxocara canis (embryonated eggs)

genus and species?

enterobius vermicularis (eggs)

characteristics of

enterobius vermicularis (eggs)?

embryonate after 6 hours

contaminated bed sheets, clothing, air

serve as delivery of trophozoites of dientamoeba fragilis

developmental stage?

enterobius vermicularis (eggs)

genus and species?

Dirofilaria immitis (adults)

characteristics of

Dirofilaria immitis (adults)?

threadlike appearance

microfilaria (incompletely developed L1) in peripheral blood smear

developmental stage?

Dirofilaria immitis (adults)

genus and species?

Microfilariae in peripheral blood smears

Brugia malayi (a and b)

Wucheraria bancrofti (c and d)

Loa loa (g and h)

characteristics of microfilariae in peripheral blood smears?

number of tails and spacing of nuclei

• Malayi has terminal and subterminal nuclei in tail

• Banfrofti has none

• Perstans has densely packed nuclei

• Loa loa has 5-6 scattered nuclei

packing of nuclear column

• dispersed in W. bancrofti and compact in others

length of nucleus-free cephalic space

• long in malayi and short in others

presence of a sheath

• absent in M. perstans and present in others

L. loa stains with hematoxylin (g) but not Giemsa (h)

perstans has smaller size and blunter tail

genus and species?

Onchocerca volvulus (adult)

characteristics of

Onchocerca volvulus (adult)?

b) microfilariae in female uterus

c) dermis showing wandering microfilariae (arrow)

d) microfilaria in tissue smear

• no sheath

• short cephalic space

  • curved tail tip

developmental stage?

Onchocerca volvulus (adult)