Parasitology_By_Omar Islam 2025 (PDF)

# Parasitology_By_Omar Islam 2025 (11 of 141) ## Nematodes of blood & tissue ### Trichinella spiralis - **Morphology**: Small, thread like, females are larviparous - **Life cycle**: Eating larvae → Adults in S.I. fertilization → larvae to circulation → active striated muscles: deltoid, diaphragm,...

# Parasitology_By_Omar Islam 2025 (11 of 141) ## Nematodes of blood & tissue ### Trichinella spiralis - **Morphology**: Small, thread like, females are larviparous - **Life cycle**: Eating larvae → Adults in S.I. fertilization → larvae to circulation → active striated muscles: deltoid, diaphragm, biceps, tongue, jaw muscles → encysted larvae (Trichinella capsule) in the longitudinal axis of the muscle - **DH**: Man - **RH**: Pigs & rodents (infected by eating infected flesh of other pigs and rodents = cannibalism) - **Habitat**: Small intestine - **Diagnostic stage**: Trichinella capsule - **Infective stage**: Trichinella capsule in flesh of pigs - **Mode of infection**: Eating undercooked pork meat containing Trichinella capsule - **Pathogenesis**: - **Intestinal phase (1st week)**: Irritation → gastroenteritis: nausea, vomiting, diarrhea, colic, fever (resembles acute food poisoning) - **Migration or muscle invasion phase (2nd & 3rd week)**: Allergic reaction & myositis of striated muscles, characterized by: - orbital edema. - myalgia and muscle weakness - fever, anorexia, malaise, headache. - Splinter hemorrhage under nail (Diagnostic) - **Convalescent stage (encystation of larvae by the end of 3rd week)**: Symptoms subside & patient recover with no effects. OR RARELY: patients may die due to myocarditis, HF, pneumonia, encephalitis. ### Dracunculus medinensis - **Definition**: Medina worm OR Guinea worm - **Morphology**: Larviparous - **Life cycle**: Larvae → adults → female migrate to S.C. tissue → forms a blister around the anterior end of the female worm → ruptures when exposed to water & The female protrudes its end from the ulcer and discharges first-stage larvae into the water. (release larvae each time it is immersed in water) → Cyclopes develop into infective third-stage larvae in about 2 weeks → ingestion of cyclopes → larvae migrate to subcutaneous tissue of thorax from S.I. It takes a year for the female to migrate to S.C. tissue. - **DH**: Man - **RH**: Domestic animals - **IH**: Cyclopes - **Habitat**: Subcutaneous tissue - **Diagnostic stage**: Larvae present in blister - **Infective stage**: Infective larvae in cyclopes - **Mode of infection**: Drinking water of wells or ponds with infected Cyclops containing the infective larvae. - **Pathogenesis**: - **Before the female pierces the skin**: papule → blister. - **Burning sensation**: redness, induration in foot, legs, hands, arms, back. - **Systemic allergic manifestations**: low grade fever, urticaria - **Secondry infection of ulcer**: cellulitis, tetanus. - **Ulcers may heal spontaneously**: but broken worm may cause irritation → allergy & fibrosis (Up to anaphylactic shock) - **Dead or ruptured worm**: sterile abscess - **Arthritis**: if worm close to joint → Contracture. - **RARELY**: ectopic lesions: lung, pericardium, spinal cord (compression & abscess) ### Cutaneous larva migrans (CLM) - **Definition**: Dermatological condition caused by the migration of non-human nematode filariform larvae of the dogs and cats' hookworms Anclystoma Brasiliense (cats) or Anclystoma caninum (dogs). - **Mode of infection**: - Skin contact with contaminated soil with stool of cats and dogs → infective filariform larvae penetrate the skin. - In animals (DH) act as the human A.duodenale. - In human (accidental host) → larvae cannot penetrate the basement membrane to invade the dermis, so larvae keep migrating in the epidermis without further development till they die. - **Pathogenesis**: - **The first symptom**: intense pruritis followed by raised, erythematous track starts near site of penetration. - **The larva itself**: is usually migrating ahead of its track. The track may move in the skin at a rate of 1-2 cm/ day (slow), progressing in a curved or serpiginous way for weeks or months till larvae die. - **The lesions**: may be single or multiple. Secondary bacterial infection may occur. - **The commonest sites**: are the hands, feet, back or buttocks. - **Important note**: between creeping eruption & larva currens ## Trichinella spiralis | **Diagnosis** | **Description** | **Treatment** | **Prevention & Control** | |---|---|---|---| | **History**: Gastroenteritis within 48 hours of eating pork. | **Clinically**: Facial edema, fever and myositis are suggestive. | **DOC**: Mebendazole | **Proper cooking of pork meat or avoiding eating it.** | | **Labs**: Parasitological: Muscle biopsy from deltoid or gastrocnemius and examined for larvae (the best diagnostic method in the 3rd & 4th weeks). | **Labs**: Immunological: Serological tests (IFAT, ELISA) OR Bachman intradermal test: Immediate hypersensitivity test: Done by injection of 0.1ml of 1:10.000 dilution of antigen prepared from dried powdered larvae gives local wheal in 20 minutes in positive cases (positive 3 weeks after infection). | **Thiabendazole** | **Meat inspection at slaughterhouses.** | | **Blood picture**: High eosinophilia (3rd & 4th week). | **Blood picture**: High eosinophilia (3rd & 4th week). | **Corticosteroids**: anti-allergic & toxic reactions. | **Destruction of rats and proper breeding of pigs.** | | **Radiological**: X-ray for calcified cysts. | **Radiological**: X-ray for calcified cysts. | **Complete rest & symptomatic treatment** | **Avoid feeding raw garbage to pigs.** | ## Dracunculus medinensis | **Diagnosis** | **Description** | **Treatment** | **Prevention & Control** | |---|---|---|---| | **Clinically**: Skin lesions ± outlines of the female visible or palpable | **Labs**: Parasitological: a. larvae may be present in blister fluid b. Active larvae can be obtained by immersing the infected part in a container with water. The protruding adult female will shed larvae which are then observed under the microscope | **Wet compresses, occlusive bandage.** | **Eradication of Cyclops in wells and other water sources.** | | **Labs**: Blood picture: eosinophilia | **Labs**: Blood picture: eosinophilia | **Analgesics and anti-inflammatory drugs.** | **Boiling and filtration of well water prior to consumption.** | | **Radiological**: . X-ray for calcified worms. | **Radiological**: . X-ray for calcified worms. | **Topical antiseptic and antibiotic ointment for secondary infection.** | **Covering wells with water pumps.** | | | | **Removal of the worm by gentle traction over a few days by twisting the worm around a stick, taking care not to break the worm to avoid severe allergic reactions (Anaphylaxis).** | **Providing alternative healthy water sources.** | | | | **Metronidazole and mebendazole: reduce inflammation around the worm for easier extraction.** | **Health education.** | ## Cutaneous larva migrans (CLM) | **Diagnosis** | **Description** | **Treatment** | **Prevention & Control** | |---|---|---|---| | **Diagnosis**: Is based mainly on clinical features. | **No eosinophilia**: if there is high eosinophilia then migration of the larvae into the tissue should be suspected. | **The lesion is self-limiting; larvae migrating in the skin usually die after 5-6 weeks.** | **Avoid skin contact with soil polluted with dogs or cat stool: wearing shoes or sitting on protective mats.** | | **Skin biopsy**: is not useful? since the location of the migrating larva cannot be predicted by the visible track. | **The lesion is self-limiting; larvae migrating in the skin usually die after 5-6 weeks.** | **Albendazole or ivermectin: ↓ symptoms & kill larvae.** | **Regular deworming of cats and dogs.** | | | | **Topical thiabendazole applied under an occlusive dressing for up to 10 days especially for early localized lesions.** | **Prompt disposal of animal waste.** | | | | **Antibiotics for 2ry infection.** | | | | | **Antihistaminic drugs.** | | ## Creeping eruption & Larva currens | Causative Parasite | Track | Site | Rate of Movement | Duration | |---|---|---|---|---| | Ancylostoma braziliense | Serpiginous | Hands, feet, back or buttocks | 1-2 cm/ day | Weeks or months | | Ancylostoma caninum | | | | | | Strongyloides stercoralis | Linear | Perianal region, thigh and back | 5-10 cm/ hour | Few hours only |