Soil-Transmitted Nematodes (And pinworms later on) Hookworms Ascaris Whipworm

Nematodes The most common macroparasite and can infect humans along with other organisms (mammals to plants) Impermeable cuticle and have a complete digestive system with a mouth and anus Often their mouths are made up of papillae, cutting plates, lips and/or auxiliary sensory organs (DIAGOSTIC FEATURES) The majority are dioecious with extreme sexual dimorphism Females tend to be larger and are packed with eggs or LARVAE

Nematodes cont. Males have a single testis, seminal vesicle and copulatory spicules Spicules are inserted into the vulva of the female and assist the passage of sperm There is quite a diversity of spicules and can be used for identification In some cases males have a copulatory bursa that aids in reproduction. Some have muscular rays that are used to clasp female during copulation

Nematodes cont. Females usually have two ovaries which appear to elongate threads that gradually widen to become the oviduct and eventually the uterus BASIC pattern Eggs (L1 or J1 larva develops) Ecdysis occurs and usually (some cases the second) juvenile stage hatches from egg (if intermediate host is present it is the L1 or L2 that is infective to ind. host)  L3’s are the infective stage to definitive hosts

Taxonomy Kingdom Animalia Phylum Nematoda Class Adenophorea Subclass Enoplia Order Trichurata Super Family Trichocephaloidea Family Trichuridae Genus species Trichuris trichiura

Trichuris trichiura The odd structure of this worm is generated by the esophagus (whipworm) The feed by embedding their anterior section (stichosome) into the intestinal mucosa Your slides will be females (males are rare since they have a short lifespan) The posterior portion contains the gonads The mouth lacks lips People infected with whipworm can suffer light or heavy infections. People with light infections usually have no symptoms. People with heavy symptoms can experience frequent, painful passage of stool that contains a mixture of mucus, water, and blood. Rectal prolapse can also occur. Children with heavy infections can become severely anemic and growth-retarded. Whipworm infections are treatable with medication prescribed by your health care provider.

Adult  eggs (L1 environment) L2L3(infective, but still enclosed in the egg eggs hatch in stomach and molt to an L4 stage and mature

21 Adult Female, 22 Adult Male Stichosome esophagus 21 Adult Female, 22 Adult Male Egg (slide 20)

Hookworms Kingdom Animalia Phylum Nematoda Class Rhabditea Order Strongylida Family Ancylostomatidae Genus species Necator americanus or Ancylostoma duodenale

Hookworm (Necator americanus) New World Hookworm (Americans and Australia, BUT can be found in Africa and Asia) Males have a copulatory bursa and a set of muscular bursal rays. This structure functions to envelope the vuvla of the female during copulation to transfer sperm. Chitinous specialization of buccal capsule (chitonous plates) The copulatory bursa has two spicules and fused tipped with a barb

Eggs are passed in the stool , and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil , and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective . These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed . The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host . Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years.

N. americanus Buccal capsule, cutting plate (arrow) Copulatory Bursa Hookworm egg (species indistinguishable)

Ancylostoma duodenale Old world (Africa and Asia) NO cutting plates This species of hookworm has “TEETH” Larger than Necator (more damage in intestinal tract)

A. duodenale Cutting plates

N. americanus and A. duodenale 0.10 mm length, 0.4 mm diameter. Female > Male 9000 eggs/day, eggs have 3-5 yrs survival Buccal capsule set with two crescent-shaped cutting plates on ventral side Ingests 30 µl blood/day 12 mm in length, 0.6 mm in diameter. Female > Male 20,000 eggs/day, eggs have 1 yr survival Buccal capsule set with symmetric pair of sharp teeth on ventral side. Ingests 260 µl blood/day

Taxonomic Classification Kingdom Phylum Class Order Family Genus Species Animalia Nematoda Rhabditea Ascaridida Ascarididae Ascaris lumbricoides

Ascaris lumbricoides Up to a half of a meter 200,000 eggs released per day Subjecting their eggs to formalin, potassium dichromate, and even a 50% solution of sulfuric acid does not prevent eggs from developing Observe the cross sections of Ascaris

Worldwide, the most common helminth infection in humans More common in tropical and subtropical areas Occurs in S.E. United States Eggs (J1)J2(still in egg)eggs are consumed and hatch in the intestine and penetrate into the circulatory system and move to the lungs where they molt twice to the J4 stage Migrate up to the pharynx and are swallows  once in the intestine the worms develop into maturity

Ascaris lumbricoides Female Male Ascaris unfertilized egg. Ascaris egg containing a larva, which will be infective if ingested. Ascaris fertilized egg.

Taxonomic Classification Kingdom Phylum Class Order Family Genus Species Animalia Nematoda Secernentea Ascaridida Oxyuridae Enterobius vermicularis

And Pinworms Eggs are deposited on perianal folds . Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area . Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g. , curtains, carpeting). Some small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs. Following ingestion of infective eggs, the larvae hatch in the small intestine  and the adults establish themselves in the colon . The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area . The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions . Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.