Lecture #11: THE BLOOD FLUKES

General characteristics

1.      They are elongatedly cylindroidal in shape with prominent oral and ventral sucker.

2.      They have separate sexes (dioecious).

3.      Absence of muscular pharynx

4.      Intestine bifurcates and unites at a certain level to form the united intestinal ceca.

5.      The male adult are provided with gynecophoral canal on the ventral side, the function of which is to cuddle the female throughout its entire life except during oviposition. Since they are always in perpetual copula, they are known as the most romantic parasites.

6.      Their life span may be as long as 30 years.

7.      They are the only trematodes found in the bloodstream, they can also be isolated in stool and urine.

8.      Ova are embryonated and not operculated.

9.      They are the only trematode which requires one intermediate host.

10.  Since they have no metacercaria, the infective stage is the cercaria which has a characteristic fork–tailed appearance.

******  SCHISTOSOMA JAPONICUM  ******

Common name:       Oriental blood fluke

Synonyms:                Sinobilharzia japonica (Katayama’s disease)

1.      Adult

a.      Male adult measures 12 – 20 mm and 0.5 mm in diameter, oral and ventral suckers located near the anterior end of the worm; considered as the biggest of all blood flukes; cuticles are smooth and non–tuberculated, provided with 6–9 testes arranged in rows. Intestinal ceca bifurcates, then fuses very posteriorly.

b.      Female adult measures 26 mm x 0.3 mm (longer and more slender), more than one esophageal bulb with fine cuticles, ovary located centrally, uterus is long and well–developed with 50 –100 eggs, the female is usually found held in the gynecophoric canal of the female, the females are capable of laying about 1500–3500 eggs per day (most destructive).

2.      Ova is 75–100 x 50u, broadly ovoidal in shape with very characteristics cellular debris, it has a rudimentary or abbreviated lateral spine, the shell stained acid fast, sloping shoulder miracedium inside.

Habitat:

Superior mesenteric plexus and ocassionally the inferior mesenteric and portal venous system

Intermediate host:               Oncomelania quadrasi

Reservoir host:                     Dogs, cats, mice, cattle, pigs, goats

Life cycle

******  SCHISTOSOMA MANSONI  ******

Common name:       Manson’s blood fluke

Disease:                     Manson’s intestinal schistosomiasis or bilharziasis

Morphology:

1.      Adult

a.      Male measure 6–12 x 1 mm, coarse tuberculation, lateral margins interlock and are held in position by acuminate spines which are longer than the other integumentary ones, minutes sensory papilles are distributed over the surface and the tuberosities are provided with microscopic tufts of the hair. There’s early union of the intestinal ceca; 3–13 small testes arranged in clusters.

b.      Female measure 7–17 x 0.25 mm with only one esophageal bulb; early union of intestinal ceca; ovary located anteriorly with a short uterus containing 1 – 4 eggs; females are capable of laying 10–300 eggs per day.

2.      Ova measures 114 – 175u and has a very prominent lateral spine

Habitat  

Inferior mesenteric plexus or portal venous sytem

Intermediate host:   Australobis, Biomphalara, Planorbis

Life cycle

*******  SCHISTOSOMA HAEMATOBIUM  *******

Common name:       Vesical blood fluke

Disease:                     Vesical schistosomiasis, schistosomal hematuria

                                    Vesical or urinary bilharziasis

Morphology:

1.      Adult

a.      Male has shorter, stouter organism, measuring 10–15 x 0.8–1 mm. It has fine tuberculation and has 2 suckers (ventral is larger); behind the ventral sucker, the body of the male is infolded ventral all the way to the caudal extremity to form the gynecophoral canal, there is late union intestinal ceca, there are 4 – 5 tested arranged in clusters or columns.

b.      Female are long and slender, measuring 20 x 0.25 mm, the suckers are small, subequal and are not conspicuously muscular; ovary located at the posterior end with a long uterus containing 20 to 30 eggs, the female is capable of producing 20–290 eggs per day.

2.      Ova measures about 120u and is provided with a very characteristic terminal spines.

Habitat:

Vesical and pelvic plexuses of the venous circulations

Intermediate Hosts:                         Bulinus, Planorbis

Life cycle