1、Hookworms The hookworms cause hookworm disease,which is one of the five major parasitic disease in China(malaria,shistosomiasis,filariasis,kala-azar and hookworm disease).At least two species of hookworms infect man,Necator americanus and Ancylostoma duodenale.They live in small intestine.I.Morpholo
2、gy1.Adults:They look like an odd piece thread and are about 1cm.They are white or light pinkish when living.is slightly larger than.The males posterior end is expanded to form a copulatory bursa.2.Eggs:6040 m in size,oval in shape,shell is thin and colorless.Content is 2-8cells.Adults of A.duodenale
3、 Adults of N.americanusDifferences between two hookworms Scanning electron micrograph of the mouth capsule of Ancylostoma duodenale,note the presence of four teeth,two on each side.Scanning electron micrograph of the mouth capsule of Necator americanus,another species of human hookworm.Note the pres
4、ence of two cutting teeth“.Ancylostoma duodenale-copulatory bursa and spines of male(a side view)Copulatory bursa of N.americanus(a side view)Left picture:Copulatory bursa and spines of N.americanus(a side view);Right picture:copulatory bursa of A.duodenale(a top view)Morphologically it is not possi
5、ble to differentiate between A.duodenale and N.americanus.Interference contrast.400.Enlarged by 5.4.3.The Morphological Differences between Two species of Hookworms_ A.duodenale N.americanus_ Size larger smaller_ Shape single curve,looks like C double curves,looks like S _ Mouth 2 pairs of ventral t
6、eeth 1peir of ventral cutting plates_ Copulatory circle in shape oval in shape Bursa (a top view)(a top view)_ Copulatory 1pair with separate 1pair of which unite to form spicule endings a terminal hooklet_ caudal spine present no_ vulva position post-equatorial pre-equatorial _II.Life Cycle 1.Final
7、 host:man 2.Inf.Stage:Larva 3 or filariform larva 3.Inf.Route:by skin 4.Food:blood and tissue fluid 5.Site of inhabitation:small intestine 6.Life span:Ad 15years,Na 3-7years 7.Blood-lung migration:skin,cavum,right heart,lungsLife cycle of hookwormIII.Pathogenesis and Clinical Manifestations 1.Larval
8、 migration (1)Dermatitis,known as ground itch or stool poison.The larvae penetrating the skin cause allergic reaction,petechiae 0r papule with itching and burning sensation.Scratching leads to secondary infection.(2)pneumonitis(allergic reaction),Loeffiers syndrome:cough,asthma,low fever,biood-tinge
9、d sputum or hemoptysis,chest-pain,inflammation shadows in lungs under X-ray.These manifestations go on about 2 weeks.2.Adults in small intestine (1)Epigastric pain as that of a duodenal ulcer.(2)A large worm burden results in microcytic hypochromatic anemia(character manifestation).The symptoms are
10、lassitude,edema,palpitation of the heart.In severe case,death may result from cardiac failure or physical exhaustion.(3)Allotriophagy(orpica)is due to the lack of trace element iron.(4)Amenorrhea,sterility,abortionmay take place in women.(5)Gastrointestinal bleeding (6)Infantile hookworm disease Adu
11、lts in intestinal mucosaIv.Diagnosis Criterion:1.hemoglobin is lower than 120g/L in man,110g/L in woman.2.find hookworm egg Method:1.saturated brine flotation technique2.direct fecal smear3.culture of larvaeV.Treatment1.Albendazole 2.MebedazoleVI.Epidemiology worldwide distribution.22-26 is the opti
12、mal temperature for Ancylostoma duodenale development,Ancylostoma duodenale mainly prevalent in north of China.31-35 is suitable for Necator americanus,it is mainly prevalent in south of ChinaVII.PreventionUnified measures:1.sanitary disposal of night soil,2.individual protection,3.health education,4.cultivate hygienic habits,5.treat the patients and carriers.
