intestinal nematodes

nematodes general characteristics

• aka roundworms

• infect intestines, blood, body fluid and tissues

• females are larger than males

• have complete digestive systems

nematodes life cycle

• intestinal- have direct life cycle

• tissue- have an arthropod vector

• all cycles include 4 larval stages

nematodes diagnosis

identification of eggs and or larvae in stool

enterobius vermicularis

• aka pinworm

• found worldwide

• infects children primarily

• frequently spread in families, daycare centers

enterobius vermicularis transmission

• direct fecal oral route

• ingestion or inhalation of embryonated ova from contaminated fingers or fomites

enterobius vermicularis clinical infection

• often asymptomatic

• anal itching

• insomnia

• vomiting

• utis are seen in young girls

enterobius vermicularis lab diagnosis

• stool sample is unsatisfactory!!!

• identification of eggs in perianal scrapings or cellulose tape prep

enterobius vermicularis adult characteristics

• 7-15 mm long

• pointed tale resembling a pin

enterobius vermicularis egg characteristics

• most common

• 50-60 long by 20-30 micrometers wide

• oval thick colorless shell flattened on one side

• look like letter D

trichuris trichiura

• aka whipworm

• most common soil transmitted helminth

trichuris trichiura transmission

• ingestion of infected ehh from soil contamination

trichuris trichiura clinical infection

• light infections are asymptomatic

• heavy infection- intestinal bleeding, weight loss, abdominal pain, nausea, vomiting

• complications- colitis, rectal prolapse, hypochromic anemia

trichuris trichiura lab diagnosis

dinding eggs and occasionally adult worm in feces

trichuris trichiura egg characteristics

• eggs in stool most common

• football shape

• prominent polar plugs

• 50-55 long by 22-23 wide

trichuris trichiura adult characteristics

• 300 mm-50mm

• males are smaller and have a coiled tail

ascaris lumbricoides

• more than 1 billion people worldwide are infected

• children are most commonly infected

• soil transmitted helminth

• can be infected with hundreds of them in the intestine

ascaris lumbricoides transmission

ingestion of eggs by fecal/oral, soil contamination

ascaris lumbricoides clinical infection

• abdominal discomfort, loss of appetite, colikcy pains

• heavy infections-malabsorption, intestinal obstruction

• larval migration- asthma, edeme, ascaris pneumonitis

• sputum may contain eosinophils, charcot leyden crystals and larvae

ascaris lumbricoides lab diagnosis

• identification of undeveloped eggs in feces

ascaris lumbricoides unfertilized egg characteristics

• elongated

• have mammillations

ascaris lumbricoides fertilized egg characteristics

• oval shaped

• thick hyaline wall

• brown bile stained outer layer

• 45-75 by 35-50

Intestinal nematodes hookworms are

• necator americanus

• ancylostoma duodenale

necator americanus characteristics

• aka new world hookworm

• have 4 pointy teeth

• africa, s cental america

• 
  

ancylostoma duodenale

• aka old world hookworm

• europe, n. africa, mediterana, asia , s america

hookworms clinical infections

• ground itch- itchy red papule at the site of larval penetration

• symptoms may vary to phase of life cycle and worm burden

• larval migration to lungs

• adult infection- asymptomatic or fever, diarrhea, vomiting, eosinophilia, pica

• chronic/heavy infection- malnutrition, microcytic hypochromic anemia

hookworms lab diagnosis

• eggs and rhabditiform larva are diagnostic stages

hookworm egg characteristics

• impossible to distinguish between species of hookworms

• disorganized globular contents with thin oval clear smooth colorless shel

strongyloides stercoralis

• aka thread worm

• parasite can be persistent in host for decades

• has direct, indirect, and auto infection life cycle

strongyloides stercoralis diagnostic stage

• rhabditiform larvae in feces, duodenal material, sputum

• ova or adults occasionally found

strongyloides stercoralis transmission

• penetration if human skin by filariform larvae in contaminated soil

• adults live in the small intestine

strongyloides stercoralis clinical infections

• asymptomatic

• cutaneous- itching at point of entry, no prominent papule

• pulmonary- mild cough

• intestinal- abdominal pain, diarrhea

• complications in immunocompromised hots- disseminated strongyloidiasis

strongyloides stercoralis rhabditiform larva characteristics

• short buccal capsule

• large bulb in esophagus

• large genital primordium

strongyloides stercoralis filariform larva

• may be identified in sputum of patients with hyperinfection