Introduction to Parasitology Suggested Textbook Markell and Voges

Introduction to Parasitology Suggested Textbook : Markell and Voge’s Medical Parasitology. 9 th ed. John DT & Petri WA. 2006.

Helminth 蠕蟲 (-ology) Nematoda 線蟲 Trematoda 吸蟲 Cestoda 絛蟲 Protozoa 原蟲 (protozoology) Arthropoda 節肢動物 (Entomology 昆蟲學) Vector 媒介 : biological 生物性, mechanical 機械性 Parasitic zoonoses 人畜共通寄生蟲病

Parasite 寄生蟲 : infection temporary暫時性, stationary定留性 ecto-, endoobligatory 專性, facultative 兼性 pathogenic 致病性, non-pathogenic 非致病性 spurious 假性, pseudo- 假的 accidental 偶然 Host 宿主 : Final host (FH) (definitive host) 終宿主 Intermediate host (IH) 中間宿主 Paratenic host (transport host) 保幼宿主 Reservior host (RH) 保蟲宿主

Mode of infection : oral, skin penetration, congenital infection Infective form 感染型 Effects of parasites on hosts : 1. Compete for the nutrients 2. Feed on host tissue 3. Mechanical damage 4. Toxic substance 5. Others

-osis -asis Prevention : 1. Treatment of patients and reservoir hosts 2. Treatment of excreta of final hosts 3. Control of vectors and intermediate hosts 4. Prophylaxis against infections 5. Scientific nomenclature :

The “top ten” human parasites Parasite No. infected (億) Deaths/year (萬) Ascaris 蛔蟲 13 2 -6 Hookworms 鉤蟲 13 5 -9 Trichuris 鞭蟲 9 Amebae 阿米巴 5 4 -11 Malaria 瘧疾原蟲 4 -4. 9 250 Giardia 梨形鞭毛蟲 2 Schistosomes 血吸蟲 1. 5 Filarias 絲蟲 1. 46 Trypanosomes 錐蟲 0. 25 6. 5 -10 Leishmania 利什曼原蟲 0. 12 8 50 -100

Outline of Nematoda (約50萬種) Morphology : generally elongated and cylindrical, tapering at both end Differ greatly in size : (F > M) Strongyloides stercoralis 糞線蟲 2 mm Dracunculus medinensis 麥地那蟲 > 1 m Body wall : cuticle 角皮層 hypodermis 皮下層 musculature 肌肉層

Digestive system : mouth buccal cavity esophagus intestine rectum anus Reproductive system : male : single coiled tubule accessory copulatory apparatus : spicule 交尾刺 bursa 交尾囊 female : single or double tubules

Life cycle : Egg L 1 L 2 L 3 L 4 Adult Oviparous 卵生 mature egg FH Egg embryonated egg IH ( infective larva) FH hatched larva infective larva FH IH ( infective larva) FH Larviparous 幼生 (ovoviparous 卵胎生) Larva IH ( infective larva) FH

No reservior host Transmission control 90%於下肢 No immunity and cure

I. Ascaris lumbricoides 蛔蟲 The giant intestinal roundworm Ascariasis, ascariosis Distribution : worldwide Morphology : Male : 15– 30 cm x 2– 4 mm Female : 20– 35 cm x 3– 6 mm Egg : unfertilized, embryonated, mature

Life cycle Prepatent period : 2 – 3 months Life span : 1 – 2 years RH : pig (Ascaris suum ? ) Infective form : mature egg (soil–transmitted) Mode of infection : contamination of food and water Habitat : small intestine

2 -3 wks

Pathology and Symptomatology : Migrating larvae : fever, cough, hemmorrhage, Loffler syndrome eosinophilia, increased level of Ig. E pneumonitis (heavy infection) Adult worms : protein–energy malnutrition, vague abdominal discomfort, intestinal obstructions heterotopic (ectopic) 異所寄生 Pica 異嗜症

Diagnosis : stool examination (20萬 eggs/隻/天) Treatment : Mebendazole (Vermox) Albendazole (Zentel) Pyrantel pamoate (combantrin) Levamisole (Tetramisole) Piperazine salts (Antepar) Surgical consideration Prevention : Epidemiology :

II. Toxocara canis 犬蛔蟲 Toxocara cati 貓蛔蟲 toxocariasis Distribution : cosmopolitan Morphology : cervical alae 頸翼 T. canis male : 4– 6 cm (max. 13) female : 6– 10 cm (max. 20) T. cati male : < 6 cm female : < 12 cm Egg : pitted shell

Encyst? L 2 T. cati 不經胎盤感染

Infective form – mature egg (Soil–transmitted parasite) PH : man, mice, rat, rabbit, chicken, etc. Pathology and Symptomatology : Granuloma in liver, lung, kidney, heart, striated muscle and eye VLM (visceral larva migrans): asymptomatic or characterized by eosinophilia, hepatomegaly, pulmonary infiltration, hyperglobulinemia, fever and cough OLM : eye lesion usually painless, unilateral and symptomless, may lead to total retinal detachment (retinoblastoma ? )

Diagnosis : Biopsy Serologic tests Treatment : Mebendazole Albendazole + Corticosteroids (anti–inflammatory) Surgery (OLM) Epidemiology : children, owners of dogs or cats (seroprevalence : 5% in USA, France) Prevention :

III. Anisakine Nematodes 海獸胃線蟲 Herring worm, codworm Anisakis spp. : A. simplex, A. typica, A. physeteris Pseudoterranova (=Teranova, Phocanema) spp. Contracaecum spp. etc. Distribution : cosmopolitan

Morphology : Anisakis sp. : male 3– 9 cm female 6– 10 cm infective larva 2– 3. 5 cm x 0. 3– 0. 6 mm Life cycle : IH : small marine crustaceans PH : marine fishes and squids FH : marine mammals Habitat : FH – stomach Man – stomach, intestine, throat

Pathology and Symptomatology Transient anisakiasis : throat irritation nausea, gastric distress within a few hours after ingestion of fish Eosinophilia Pain, ulcer and granuloma of stomach and small intestine; bloody stool; severe appendicitis; usually mistaken for carcinoma

Diagnosis : Identification of specimens removed by gastric endoscopy or surgery Treatment Pluck out the worms by using a gastroscope Surgical operation Prevention

IV. Gnathostoma spp. 棘口線蟲 Gnathostoma spinigerum , gnathostomiasis Distribution : Far East Morphology : headbulb 頭球, hooklets, cuticular spines Male : 11– 25 mm Female : 25– 54 mm

G. I.

Life Cycle : 1 st IH : copecopds 水蚤 (Cyclops spp. ) 2 nd IH and PH : crustaceans (experimentlly), freshwater fish, amphibians, reptiles, birds and mammals (except felines and canines) RH : felines and canines Mode of infection

Pathology and Symptomatology : CLM : rash, stabbing pain, pruritis VLM Neurological g. : eosinophilic myeloencephalitis Ocular gnathostomiasis : palpebral edema (長江浮腫) , exophthalmos, subconjunctival hemorrhage, blindness Diagnosis : history Identification of the removed worms Treatment : Albendazole, surgery Prevention

V. Enterobious vermicularis 蟯蟲 pinworm (spindle–shaped) Distribution : worldwide 溫帶多於熱帶, 都市多於鄉村 Morphology : cephalic alae, esophageal bulb Male : 2– 5 mm Female : 8– 13 mm Egg : asymmetrical shape

Life Cycle : Infective form : emberyonated egg (6– 7 hrs after oviposition) Prepatent period : 15– 43 days (3– 4 weeks is more common) Life span : 4– 8 weeks Habitat : cecum Mode of infection *Family infection, retroinfection

Pathology and Symptomatology : Asymptomatic or Peranal, perineal or vulval pruritis Appendicitis Heterotopic parasitism : peritonitis Diagnosis : Anal swab (Graham’s Scotch tape swab technique)

Treatment : Mebendazole Albendazole Pyrantel pamoate Pyrvinium pamoate Piperazine salts Prevention :

VI. Angiostrongylus cantonensis 廣東血線蟲 Rat lung worm, angiostrongyliasis Distribution : Southeast Asia and pacific islands 日、中、台、泰、越、馬來西亞、夏威夷、大溪地等 Morphology : Male : 16– 19 mm (small bursa) Female : 21– 25 mm Barber’s pole pattern – white uterine and black intestine Egg : hatch in the lung of rat

Life cycle : IH : land snail – 非洲大蝸牛、扁蝸 freshwater snail – 圓田螺、福壽螺、元寶螺 slug 蛞蝓 PH : 渦蟲、蛙、蛇、蝦、蝲蛄、螃蟹等 RH : rat, bandicoots Accidental host Mode of infection ? Habitat ?

F. H. I. H.

Pathology and Symptomatology : Asymptomatic or Eosinophilic meningitis Eosinophilic meningoencephalitis Fever, vomiting, nausea, severe headache, stiff neck, sensory impairment, death Eye invasion – visual impairment, ocular pain

Diagnosis : Young adults in CSF Blood and CSF : eosinophilia, pleocytosis CT, ELISA Treatment : Anthelmintic treatment is not recommended Supportive treatment, corticosteroid Removal of CSF Immunotherapy ? Prevention :