Phylum Nematoda If all the matter in the universe except the nematodes were swept away,…we should find our world’s mountains, hills, vales, rivers, lakes and oceans represented by a thin film of nematodes. N.A. Cobb (1914, Yearbook of the United States Department of Agriculture)

Phylum Nematoda Parasitic and free-living Numerous and diverse 6.7 ml of coastal mud 1,074 individuals 236 species Rotting apple: 90 thousand individuals Farmland: 9 billion per acre

Phylum Nematoda Roundworms Dioecious (mostly) Tapered at both ends Pseudocoelomate Pseudocoel Complete digestive system Mouth and anus What kind do platyhelminths have?

Pseudocoelomate Characteristics “false” body cavity ectoderm pseudocoelom mesoderm Gut endoderm the pseudocoelom is lined by mesoderm on ONE side only

Characteristics of the Phylum Nematoda

Phylum Nematoda Triradiate pharynx Pharynx between mouth and esophagus

Photo by Agustín Jimenez

Phylum Nematoda Body covered by: Cuticle Noncellular Molts 4 times during development

Elaboration of Cuticle Aspidodera

Phylum Nematoda Movement Contraction of muscles Longitudinal muscles Hydrostatic skeleton Fluid filled pseudocoel Cuticle Contraction of muscles Antagonized by pressure of pseudocoel and hydrostatic skeleton

Tube within a tube Female Esophagus Uterus Vulva

Tube within a tube Male Cloaca = common area for openings of genital pore and anus

Copulatory Spicules Hold vulva open during copulation

Reproduction Dioecious Some Monoecious (rare) Parthenogenesis Females reproduce without males Unfertilized eggs develop into new individuals Sometimes systems are mixed (heterogamy) Mate Finding Pheromones Thigmotaxis (papillae near reproductive structures)

Papillae Sensory structures

Mating Behavior Male coils tail around female and searches for vulva.

Characteristics of the Phylum Nematoda Nematode development is similar in all nematodes.  Consists of 4 juvenile stages between the egg and adult. Each stage is separated by a molt of the cuticle.   Hatch M1 M2 M3 M4 Egg J1 J2 J3 J4 Adult Juvenile stages may be passed within the egg, free-living in soil, parasitic in an intermediate host, or parasitic in definitive host.

Parasitic Nematodes

Order Ascaridida Ascaris lumbricoides Ascaris suum Toxocara canis Ascaridia galli Parascaris equorum Anisakis sp. Baylisascaris procyonis

Ascarids These are large roundworms of animals, and humans (7-40 cm). As adults they live in the small intestine of mammals and birds. These are predominantly parasites of young animals and people.

Ascaris lumbricoides and A. suum Similar species Ascaris lumbricoides Humans Ascaris suum Pigs Probably dealing with two diverging populations Cross infection can occur

Facts The annual global morbidity (# of people infected) due to Ascaris infections is estimated at 1 billion with a mortality (# of people that die) of 20,000. Ascariasis can occur at all ages, but it is more prevalent in the 5 to 9 year age group. The incidence is higher in poor rural populations.

Biology Adults live in the small intestine (1 foot long by 5-6 mm in diameter). Worms are along the mucosa so ordinarily not much obstruction. Feed on semi-digested material.

Life Cycle Adults in small intestine mate and lay eggs which are passed in the feces of the host. Eggs must embryonate in soil (not infective initially) takes about 1 month; molt to J2 (J3) stage in egg.

Biology One worm will lay 200,000 + eggs per day. Extremely resistant; infective eggs will last for years in the soil.

Biology Eggs are golden brown in color. Eggs are covered with proteinaceous coat (mammillated surface) which makes them very sticky! Unfertilized egg Fertilized egg Decorticated egg

Eggs Unfertilized egg Fertilized egg Decorticated egg Size 50-75 X 40-50 μm

Life Cycle In order to be infected humans must swallow embryonated eggs with J2 (J3)’s!

Contaminated food, hands, etc.

Life Cycle Eggs swallowed Hatch in small intestine Juveniles penetrate mucosa and enter blood stream

Life Cycle Juveniles pass through liver and heart to lungs and molts to J3 Develop for 10-14 days Penetrate the alveolar walls, ascend the bronchial tree to the throat and molts to J4

Life Cycle Swallowed Go back to small intestine Molt and mature into adults

Pathology and Symptoms Usually in people the first few times we are exposed to Ascaris not much response. However, humans are allergic creatures, and the more times exposed the more severe the reaction!

Pathology and Symptoms Get granulomas in liver! Liver milk spots

Pathology and Symptoms Have trouble breathing in lungs, coughing, even pneumonia and sometimes death!

Pathology and Symptoms Ascaris has characteristic 3 lips. Use to chew mucosa. Secretes enzymes of their own on the surface.

Pathology and Symptoms Enzymes interfere with our own enzymes (may be a reason why we don’t digest them). Children with infection don’t grow normally  not absorbing nutrients adequately.

Pathology and Symptoms In the Philippines, calorie cost is equivalent to 100,000 lbs of rice a day!

Pathology and Symptoms Boy (8) mysteriously died & authorities originally thought it was homicide until an autopsy revealed that he was infected with hundreds (921) of Ascaris lumbricoides.

Pathology and Symptoms People don’t usually die from ascarid infections even though they have hundreds of worms. Won’t feel good, and will be robed of nutrients. Symptoms are practically non existent to abdominal discomfort and diarrhea

Pathology and Symptoms Occasionally obstruction can occur when worms are treated in heavy infections and form knots.

Pathology and Symptoms Worms migrate looking for mates. Can crawl out through the nose, ears, anus. Problem is that they can wander into small holes or other areas.

Pathology and Symptoms Infant suffocation due to worms wondering into trachea. Known to get in Eustachian tubes in ear and cause balance problems. Crawl into appendix.

Distribution and Treatment Drugs of choice: Ivermectin and Mebendazole. Cosmopolitan!

Toxocara canis and Toxocara cati Common ascarids in the intestines of dogs and cats! Prevalence in dogs and cats is estimated to be between 20 to 100%. These parasites are enzootic in Oklahoma dogs and cats.   Adults are much smaller than Ascaris. - males are about 10 cm in length - females are 18 cm in length

Toxocara canis Life Cycle 4 aspects to the life cycle: 1. Normal cycle in the dog (dogs up to 6 months of age) Dogs are infected by ingestion of eggs with J2 (J3) Juvenile undergo migration through lungs and are swallowed Reach adulthood in dog small intestine 1. Normal cycle in dog

Toxocara canis Life Cycle 2. Addition of a paratenic host (rodent) If a mouse ingests an infective egg, the juvenile J2 (J3) hatches and migrates to many internal organs. It develops no further. If mouse is eaten by a dog, the J2 (J3) penetrates the dog’s intestine and undergoes normal migration.  

Toxocara canis Life Cycle Transplacental transmission If a bitch becomes infected, the migrating J2 (J3) can cross the placenta to infect the fetal puppies. When the puppies are born, they are already infected with worms; PPP 3-4 weeks. Prevalence rates in puppies can reach 100% because of the efficiency of transplacental transmission.

Toxocara canis Life Cycle 4. Human infection Human infections of Toxocara cause "visceral larva migrans" This disease results when eggs with J2 (J3) are accidentally ingested by humans.

Toxocara canis Life Cycle J2 hatch in the human small intestine, penetrate the intestine, and enter the circulation. J2 are carried throughout the visceral organs where they wander randomly - hence, the name "visceral larva migrans".

Toxocara canis Life Cycle Eventually, the human immune system recognizes the parasite encapsulates it, and the J2 (J3) is killed.  

Pathology of Visceral Larva Migrans PATHOLOGY - dependent upon which organs are invaded by the J2 (J3) The liver is commonly invaded - hepatomegaly & cirrhosis may occur. Brain invasion results in a severe tissue reaction that can result in death 3. The eyes may be invaded - scar tissue deposition in the retina can result in blindness   J2 (J3) in retina Scar tissue in retina

Tragically, most human cases involve children due to their close association with pets.  

Diagnosis and Treatment of Toxocara in Dogs & Cats Adults in dog - Identify egg in feces Diagnostic features – 85-90 X 75 μm subsperical, yellow-brown, thick shell with coarsely pitted surface, 1 cell stage TREATMENT – Ivermectin, Piperazine

Diagnosis and Treatment of Human Visceral Larva Migrans Larvae in human are very difficult to ID - only way is to do an ELISA  TREATMENT – mebendazole has recently been reported to be successful.

Prevention of Human Infection Many cities have enacted "pooper scooper" laws that require owners to clean up after their pets. Especially important in parks where pet owners take animals for walks and children are playing.

Parascaris equorum

Parascaris equorum Parasite of equids Cosmopolitan Pathogenic in young animals Pneumonia Bronchial hemorrhage Intestinal perforation Obstruction Older animals usually immune

Parascaris equorum Worms are 15-50 cm in length; eggs are 100 X 90 μm, dark brown, thick shell with a finely granulated surface!

Lifecycle Eggs are passed in manure and become infective J2 (J3) in the grass.

Lifecycle Eggs are passed in manure and become infective J2 (J3) in the grass. While grazing, the horse swallows the eggs, which hatch and burrow into the walls of the intestine.

Lifecycle Eggs are passed in manure and become infective J2 (J3) in the grass. While grazing, the horse swallows the eggs, which hatch and burrow into the walls of the intestine. From there, they are carried by the bloodstream into the liver and lungs. The horse coughs up the J4 and swallows them again. Worms mature into egg-laying adults in the intestine.

Ascaridia galli Parasite of domestic fowl Life cycle No migration After hatching, burrow into intestinal mucosa Develop Return to lumen and become an adult Wandering worms can end up in chicken eggs

Ascaridia galli Worms are about 10 cm long; the eggs are elliptical with a smooth thick shell 85 μm X 50 μm.