Aphasmids: Morphology, Life Cycle & Trichuris, Capillaria, Trichinella | Lecture notes Ethics

ACTIVITY 11

Questions for Research:

1. What are the general characteristics of aphasmids?

Phasmid (causal sensory organs) absent.

Amphids (anterior sense organs) of various types, rarely pore-like.

Excretory system absent. If present poorly developed.

Well-developed mesenterial tissue.

Caudal adhesive glands present.

2. What are the morphological features of aphasmids?

Trichuris trichiura

Eggs. The average barrel-shaped (also considered by some to be football-shaped) Trichuris trichiura

egg measures 50 to 55 µm by 25 µm. The undeveloped unicellular embryo is surrounded by a smooth

shell that retains a yellow-brown color from its contact with host bile. A prominent hyaline polar plug

is visible at each end.

Adults. The typical adult whipworm measures 2.5 to 5 cm in length. The anterior end of the adult

appears colorless and contains a slender esophagus. The posterior end assumes a pinkish-gray color,

consisting of the intestine and reproductive systems. The adult male is usually smaller than the adult

female. In addition to a digestive system, intestinal tract, and reproductive organs, the male possesses

an easily recognizable curled tail. The posterior end of the adult T. trichiura is large and resembles

that of a whip handle. The anterior end is much smaller and looks like the whip itself. It is these two

morphologic features that are the basis for the name whipworm.

Trichinella spiralis

Encysted Larvae. The average juvenile encysted larvae measures from 75 to 120 µm by 4 to 7 µm. A

fully developed larva may reach up to a length of 1 mm. These larvae settle by coiling up in muscle

fibers and becoming encysted. Biopsies of these larvae often reveal a distinctive inflammatory

infiltrate in response to the presence of the larvae. A striated muscle cell, known as a nurse cell,

surrounds the coiled larva.

Adults. Although the small T. spiralis adult worms have rarely been seen, they have been described.

The female measures 4 by 0.5 mm, whereas the male is significantly smaller, measuring 2 by 0.04

mm. The typical male adult characteristically possesses a thin anterior end equipped with a small

mouth, long and slender digestive tract, and curved posterior end with two somewhat rounded

appendages. The female differs from the male in two respects. The female possesses a blunt, rounded

posterior end and a single ovary with a vulva located in the anterior fifth of the body

Capillaria philippinensis

Adults.The parasites in this superfamily characteristically have a thin filamentous anterior end and a

slightly thicker and shorter posterior end. The male worms are about 1.5 to 3.9 mm in length, while

females are 2.3 to 5.3 mm long. The male spicule is 230 to 300 μm long and has an unspined sheath.

The esophagus has rows of secretory cells called stichocytes, and the entire esophageal structure is

called a stichosome. The anus is subterminal, and the vulva in females is located at the junction of

anterior and middle thirds.

Partial preview of the text

Download Aphasmids: Morphology, Life Cycle & Trichuris, Capillaria, Trichinella and more Lecture notes Ethics in PDF only on Docsity!

Questions for Research:

1. What are the general characteristics of aphasmids?  Phasmid (causal sensory organs) absent.  Amphids (anterior sense organs) of various types, rarely pore-like.  Excretory system absent. If present poorly developed.  Well-developed mesenterial tissue.  Caudal adhesive glands present. 2. What are the morphological features of aphasmids? Trichuris trichiura Eggs. The average barrel-shaped (also considered by some to be football-shaped) Trichuris trichiura egg measures 50 to 55 μm by 25 μm. The undeveloped unicellular embryo is surrounded by a smooth shell that retains a yellow-brown color from its contact with host bile. A prominent hyaline polar plug is visible at each end. Adults. The typical adult whipworm measures 2.5 to 5 cm in length. The anterior end of the adult appears colorless and contains a slender esophagus. The posterior end assumes a pinkish-gray color, consisting of the intestine and reproductive systems. The adult male is usually smaller than the adult female. In addition to a digestive system, intestinal tract, and reproductive organs, the male possesses an easily recognizable curled tail. The posterior end of the adult T. trichiura is large and resembles that of a whip handle. The anterior end is much smaller and looks like the whip itself. It is these two morphologic features that are the basis for the name whipworm. Trichinella spiralis Encysted Larvae. The average juvenile encysted larvae measures from 75 to 120 μm by 4 to 7 μm. A fully developed larva may reach up to a length of 1 mm. These larvae settle by coiling up in muscle fibers and becoming encysted. Biopsies of these larvae often reveal a distinctive inflammatory infiltrate in response to the presence of the larvae. A striated muscle cell, known as a nurse cell, surrounds the coiled larva. Adults. Although the small T. spiralis adult worms have rarely been seen, they have been described. The female measures 4 by 0.5 mm, whereas the male is significantly smaller, measuring 2 by 0. mm. The typical male adult characteristically possesses a thin anterior end equipped with a small mouth, long and slender digestive tract, and curved posterior end with two somewhat rounded appendages. The female differs from the male in two respects. The female possesses a blunt, rounded posterior end and a single ovary with a vulva located in the anterior fifth of the body Capillaria philippinensis Adults.The parasites in this superfamily characteristically have a thin filamentous anterior end and a slightly thicker and shorter posterior end. The male worms are about 1.5 to 3.9 mm in length, while females are 2.3 to 5.3 mm long. The male spicule is 230 to 300 μm long and has an unspined sheath. The esophagus has rows of secretory cells called stichocytes, and the entire esophageal structure is called a stichosome. The anus is subterminal, and the vulva in females is located at the junction of anterior and middle thirds.

Eggs. Female worms produce characteristic eggs, which are peanut-shaped with striated shells and flattened bipolar plugs These eggs, which measure 36 to 45 μm by 20 μm, are passed in the feces and embryonate in the soil or water. They must reach the water in order to be ingested by small species of freshwater or brackish water fish.

3. Give the pathology, epidemiology, and prevention of different aphasmids. Trichuris trichiura Pathology Epidemiology Considered as the third most common helminth, T. trichiura is found primarily in warm climates of the world where poor sanitation practices are common, such as defecating directly into the soil or using human feces as a fertilizer. Areas of the United States that have been known to harbor whipworm include the warm humid South, particularly in rural settings. Persons most at risk for contracting whipworm infections include children as well as those in psychiatric facilities. Infections with both Trichuris and Ascaris, another intestinal nematode (covered later in this chapter), are known to occur. This is likely caused at least in part because the human port of entry, which serves as the mode of organism transmission, is identical for both parasites. Prevention The spread of T. trichiura infections may be halted by exercising proper sanitation practices, especially avoidance of defecating directly into the soil, using feces as a fertilizer, and placing potentially infective hands into the mouth and prompt and thorough treatment of infected persons, when indicated. Educating children and aiding institutionalized mentally handicapped persons in their personal hygiene and sanitation practices is crucial to eradicate whipworm infections completely Trichinella spiralis Pathology Humans become infected by eating raw, undercooked, or under-processed meat from infected animals, most commonly pigs, wild boar, or bear. Larvae excyst in the small bowel, penetrate the mucosa, and become adults in 6 to 8 days. Epidemiology With the exception of the tropics, where it is only rarely reported, T. spiralis is found worldwide, particularly in members of the meat-eating population. This organism may be found in a number of different animals, including the pig, deer, bear, walrus, and rat. The wide variety of temperature zones in which these animals reside suggests that T. spiralis is resistant to colder regions of the world as compared with most parasites studied thus far. In developed areas, it is presumed that the feeding of contaminated pork scraps to hogs accounts for a major mode of T. spiralis transmission. Similarly, other animals contract this parasite from consuming contaminated meat. Prevention

In the Philippines, nearly 2,000 cases have been documented from the Northern Luzon provinces from 1967 to 1990. Cases have also been documented in Zambales and Southern Leyte. Infections are acquired by eating uncooked small freshwater/brackish water fish. Ilocano people enjoy eating bagsit and other fishes found in the lagoons. In Monkayo, Compostela Valley Province, an outbreak described as a “mystery disease” in 1998 resulted in the death of villagers due to misdiagnosis. Intestinal capillariasis was diagnosed in 17% of the cases presenting with chronic diarrhea. A more recently described endemic area in the Philippines involved Zamboanga del Norte, where more than 70 deaths were recorded and 4.9% of those examined in a parasitologic survey were confirmed to have capillariasis. A few cases have also been confirmed in Zamboanga del Sur, Agusan del Sur, and Misamis Occidental.

6. Give the laboratory diagnosis of Trichinella spiralis. Eosinophilia and high serum CPK in the acute phase. At the encystment stage, use muscle biopsy, muscle crush preparation and serology (IFAT or ELISA). Sources: Belizario, V. Y., & Leon. (2013). Philippine textbook of medical parasitology. University Of The Philippines Manila. Chiodini, P. L., Moody, A. H., Manser, D. W., & Jeffrey, H. C. (2001). Atlas of medical helminthology and protozoology. Churchill Livingstone, Repr. Gockel-Blessing, E. A. (2013). Clinical parasitology : a practical approach (2nd ed.). Elsevier Saunders. Neupane, L. (2022). Phylum Nematoda- Characteristics, Classification, Examples. The Biology Notes. Retrieved from https://thebiologynotes.com/phylum-nematoda/

Draw and label the life cycle of the parasite.  Trichiuris trichiura

 Trichiniella spiralis Draw and label the microscopic appearance of the given parasite in terms of:

 Ova/Egg Trichiuris trichiura Capillaria philippinensis Trichiniella spiralis  Mature/Adult Worm (Male and Female)

Trichiniella spiralis

Aphasmids: Morphology, Life Cycle & Trichuris, Capillaria, Trichinella, Lecture notes of Ethics

Related documents

Partial preview of the text

Download Aphasmids: Morphology, Life Cycle & Trichuris, Capillaria, Trichinella and more Lecture notes Ethics in PDF only on Docsity!