Para Lab 2

PARASITOLOGY LABORATORY 2 – NEMATODES USTMED ’07 Sec C – AsM; pictures provided by JV.N.

ANCYCLOSTOMA DUODENALE Ancyclostoma braziliense mouth part

HOOKWORM Hookworm species fertilized ovum.

Typically have a thin, hyaline shell and are bluntly rounded at the ends. They usually are in 4-8 cell stage in fresh feces and the developing ovum tends to fill the shell. In feces, it is not possible to differentiate the eggs of human Hookworm like Necator or Ancyclostoma.

Ancyclostoma caninum adult mouth part

The anterior portion of an adult is responsible for the attachment which is known as the mouth part. Take note of the dental patterns of this parasite. Ancyclostoma species adult male Hookworm Rhabditiform larvae.

NECATOR AMERICANUS Hookworm first-stage (rhabditoid) larvae. These larvae may be confused with Strongyloides larvae, normally passed in feces. The hookworm larva has a long, tubular, buccal canal and the genital primordium cannot be seen. Hookworm Filariform larvae

Hookworm, third-stage, filariform (infective) larva. The third-stage larva is much longer and more slender than its rhabditoid stage, has a short esophagus, a long intestine, and a sharply pointed tail. The iodine stain used here demonstrates the relative length of the esophagus and intestine – a ratio of approximately 1:4 in hookworm larvae. This stage normally is found in soil or in feces cultured for five days or longer. It is possible to differentiate species of the genera Necator and Ancyclostoma based on the morphology of third-stage larva.

Necator americanus adults. Female worm (left). Male worm showing copulatory bursa (middle). Frontal view of head showing pronounced anterior bend or “hook” and cutting plates (below).

Necator americanus female adult worm

Hookworm adult male

Hookworm adult female

Necator americanus male adult worm

ASCARIS LUMBRICOIDES

Ascaris lumbricoides female x-section

Ascaris lumbricoides male x-section

Eggs. Fertile eggs are bile-stained, have a mammillated, thick shell, measures 66-75 u by 35-50 u, and are in the one-celled stage when passed in feces. In some instances, the outer albuminoid, mammillated layer is absent (decorticated eggs). Infertile eggs are elongate, 85-95 u by 43-47 u, and have thin shells, with the mammillated layer varying from grossly irregular mammillations to a relatively smooth layer almost completely lacking mammillations. The internal contents are a mass of disorganized, highly refractive granules. Ascaris lumbricoides fertilized ova. Note the characteristic bile stained, mammillated external layer of the thick shell. This well defined ovum is in the one-cell stage, that normally found in fresh feces. Ascaris lumbricoides embryonated ovum. This typical embryonated egg contains an infective, second stage larva. This egg normally develops in the soil. Ascaris lumbricoides fertilized ovum. In this otherwise normal egg, the external mammillated layer is absent, and the egg is referred to as “decorticated.” Ascaris lumbricoides unfertilized ovum. This infertile egg has a poorly developed irregular mammillated layer.

STRONGYLOIDES STERCORALIS Strongyloides rhabditiform larvae

Strongyloides Filariform larvae Strongyloides third-stage, filariform (infective) larvae. The filariform larvae of S. stercoralis, as in hookworms, are longer and more slender than their rhabditoid stage. With iodine stain (left) or unstained (right) the larva is easily differentiated from that of hookworm by its long esophagus equal in length to the intestine, and by its blunt, notched tail. This filariform larva normally occurs only in soil or in cultured feces.

Ascaris lumbricoides adult worms. Morphology- males are 15-31 cm by 2-4 mm, and have a curved tail. Females are 20-35 cm by 3-6 mm, and have a straight tail. Strongyloides stercoralis adult

Ascaris lumbricoides adult female

Ascaris lumbricoides adult male

Ascaris lumbricoides Anterior (tri-radiate)

(right) The parasitic, adult female of Strongyloides lives threaded into the mucosal epithelium of the human small intestine. There is no parasitic male; the female reproduces by parthogenesis. In contrast to the free-living adults, the female appears small, very slender and filariform, and has a short pointed tail. Parasitic females rarely are seen in feces. (left) Free-living adult female, iodine stain. If feces are allowed to stand at room temperature and remain moist for two to three days, the rhabditoid larvae (arrow) may develop into free-living adult worm. -fin- [email protected] [email protected]