Parasitology - Enterobius and Strongyloides PDF

 Set your learning environment  Set a good time to watch the lecture  Take notes as how you will take note in a class  DO NOT SPEED UP! Morphology  Parasitic Female is 2.2 by.04 mm.  Slender tapering anterior end and short conical posterior end  Long and slender esophagus ex...

 Set your learning environment  Set a good time to watch the lecture  Take notes as how you will take note in a class  DO NOT SPEED UP! Morphology  Parasitic Female is 2.2 by.04 mm.  Slender tapering anterior end and short conical posterior end  Long and slender esophagus extending to the anterior fourth of the body  Vulva is located 1/3 the length of the body  Uteri contain a single file of 8-12 thin shelled ova  Free living female is 1 mm. by.06 mm  Has a muscular double bulbed esophagus  The intestine is a straight cylindrical tube  Free living male is 0.7 mm. by.04 mm  Has a ventrally curved tail  Has two copulatory spicules  Strongyloides stercoralis (most common)  S. fuelleborni (fülleborni) subsp. fuelleborni  S. fuelleborni subsp. kellyi  S.myopotami  S. procyonis  225 by 16 µm  Has an elongated esophagus with pyriform posterior bulb  Slightly smaller and less attenuated than hookworm  Shorter buccal capsule and larger genital primordium  Feeding Stage  Pyriform Posterior Bulb  Infective and Non-feeding Stage  Similar to the filariform larva of hookworm but is usually smaller and has a notched tail  Direct Life Cycle  Indirect Cycle  Autoinfection  Rhabditiform larvae are passed out of the stool  After short feeding period (2-3 days) larva molts into Filariform larva  Filariform larva penetrates the human skin and enter the venous circulation  Larvae follow the heart-lung journey  Larvae are coughed out to the glottis and swallowed  Larvae reach the upper part of the intestines and develop into adults  Rhabditiform larvae develop into free-living male and females in the soil  Male and female copulate and produce eggs  Eggs develop into rhabditiform larvae  Rhabditiform larvae may develop into Filariform larvae and can enter a new host  Filariform cannot develop into adults and MUST find a new host (Belizario)  Rhabditiform larvae in the intestines may develop immediately into Filariform larvae  Filariform larvae penetrate the intestinal mucosa or perianal skin  Establish a developmental cycle within the host  Resembles the hookworm but prevalence is lower in the temperate regions  Especially prevalent in tropical and subtropical regions  Areas where warmth, moisture and lack of sanitation are present  Most infections are light and usually go unnoticed  3 phases(cutaneous, pulmonary, gi)  Moderate infections can cause burning, dull or sharp, non-radiating midepigastric pain and may exhibit tenderness and pain when pressed  Nausea, vomiting, alternate diarrhea and constipation  Long-standing and heavy infection result in weight loss due to chronic dysentery, malabsorption and steatorrhea (Cochin China Diarrhea)  History of itching in the buttocks, lower back or upper thigh (caused by autoinfection)  Caused when Strongyloides larval dissemination occurs beyond the intestines  Usually seen in patients with high-dose corticosteroids.  Fever and pneumonia  Gram negative bacteremia and/or meningitis  Larvae can be demonstrated in the sputum  May become disseminated  Left untreated, the mortality rates of hyperinfection syndrome and disseminated strongyloidiasis can approach 90%.  S. myopotami — causes Larva curens (nutria itch)  Subcutaneous migration  Recurrent serpiginous maculopapular/urticarial rash along the Bottocks/Perineum/thighs due to repeated autoinfection  S. fuelleborni subsp. kellyi  Causes a severe, systemic illness (protein-losing enteropathy sometimes manifesting as peritoneal ascites— swollen belly syndrome)  Unexplained eosinophilia  Sequence of atypical pneumonia or bronchitis, mucoid or watery diarrhea, epigastric pain and eosinophilia is suggestive  Eosinophilia usually ranges from 10% to 20% but is absent in hyperinfection  Clinical diagnosis is difficult  Examination of feces and duodenal contents (duodenal aspiration)  Presence of motile rhabditiform larva in the stool or duodenal aspirate  In disseminated strongyloidiasis, larvae may be found in sputum or urine.  Eggs are rarely found in the stool and can be obtained only by drastic purge or duodenal intubation  Baermann funnel gauze method  Culture  Harada-Mori culture technique  Koga culture method  Charcoal culture  Beale’s string test (Enterotest)  Antibody detection — if suspected organism not detected on other methods but suspicion is high  Molecular methods  Ivermectin  Albendazole and thiabendazole  Prognosis is good in light infections  Mortality is high in moderate and heavy infection  Hyperinfection can occur in immunocompromised patients which is exacerbated by autoinfection  Sanitary disposal of feces  Protection of susceptible individuals  Treatment of infected individuals  Education on health and sanitation  Old name: Oxyuris vermicularis  Causative agent of enterobiasis/oxyuriasis  Most common helminth parasite in the temperate regions,  Less in tropics Morphology  Adult female is small (8 – 13 mm. by 0.4 mm)  Has cuticular alar expansion at the anterior end (cephalic alae)  Prominent esophagial bulb and pointed tail  Uteri may be distended with eggs if gravid  Male is smaller (2 – 5 mm. in length)  Curved tail and a single spicule  Asymmetrical; one side is flattened and the other side is convex  50 to 60 µm by 20 to 30 µm  Translucent shell consists of outer triple albuminous covering  Inner embryonic lipoidal membrane  Eggs become infective in 4 – 6 hours  Humanity is the only known host  Mature pinworm inhabits the cecum  A single female lays from 4,672 to 16,888 eggs per day with an average of 11,105 eggs, dies upon deposition  Eggs become embryonated in the perianal region within 6 hours.  Upon ingestion or inhalation of eggs, first larval stage hatch in the duodenum  Molts twice and reaches jejunum and upper ileum  Copulation occurs in the cecum  Eggs may be airborne  Retroinfection is also possible but frequency is unkown.  The eggs may survive for some days in dry dust, and airborne eggs can infect persons at a distance via inhalation.  Usually innocuous  Pruritis, perianal, perineal and vaginal itching and irritation  Intense scratching can lead to excoriations secondary bacterial infection  Itching relieved only through scratching  Poor appetite, loss of sleep, loss of weight, enuresis (involuntary passing of urine), insomnia, grinding of teeth, irritability, abdominal pain, nausea and vomiting  Familial disease/group disease  Complications such as appendicitis, vaginitis, endometritis, salpingitis, and peritonitis are all due to aberrant adult worm migration.  Extraintestinal infections are rare  Female reproductive system is the most common  Suspected if patient shows perianal itching, insomnia and restlessness  Bedwetting  Finding of characteristic eggs and adults  Eggs are seldom found in the feces  Scotch adhesive tape method  A drop of toluol may be placed between the slide and the tape to clear the specimen  Repeated consecutive examination is required  Anal swabs (Swube Tubes)  Graham’s scotch adhesive tape swab (perianal cellulose tape swab), done in the morning before defecation  Addition of toluene can clear everything except the eggs and hair  Nails may also be tested (children)  Mebendazole, Albendazole, Pyrantel Pamoate  Mebendazole is teratogenic  Pyrantel pamoate: 11 mg. per kg body weight single dose repeated after two weeks  Side reactions include headache, dizziness, vomiting, abdominal pain and diarrhea and elevated SGOT levels but are mild and transitory  Family members must be diagnosed and treated  Personal cleanliness  Hand washing before and after meals; after using the toilet  Anal region should be washed upon waking up  Infected children should wear tight fitting pants  Infected individual should sleep alone  Underwear, clothes, beddings should be laundered with hot soapy water  Food should be protected from dust