NewLec30-09-62Cysticercosis

Parasitic Zoonosis Cysticercosis 30/09/2019 (2 hrs.) By Asst. Prof. Dr. Khampee Pattanatanang

Class Cestoidae Phylum Platyhelminthes Class Cestoidae formerly called Cestoda Cestode or tapeworm (ribbon-like)

Class Cestoidae 11 orders  9 orders (annelids, fishes, amphibia or reptiles)  2 orders (domestic animals and men)*

Class Cestoidae  Usually segmented endoparasites in host’s digestive tract  Body divided into segments called “Proglottids”  No epidermis or cuticle

Class Cestoidae  Specialized Tegument Microtrix (Microtriches)  Complete absence of alimentary canal  No mouth  No digestive organ



Class Cestoidae 2 Subclass S.c. Cestodaria=minor group S.c. Eucestoda=major group*

Subclass Eucestoda  Morphology- 3 distinct regions: 1.Scolex (Anterior end) 2.Neck (Next Between the scolex and immature proglottid) 3.Strobila (Many proglottids 800- 900 proglottids)

Subclass Eucestoda  Morphology- 3 distinct regions: 1. Scolex or head (p.scolices); holdfast organ  Acetabulate scolex (Cyclophyllidian group)  armed scolex, these hooks are usually grouped at the apical end of the scolex on a protusible rostellum

H. nana (SOURCE: D. Scott Smith, M.D./CDC)

Subclass Eucestoda  Morphology 2. Neck region  situated immediately posterior to scolex

Subclass Eucestoda  Morphology 3. Strobila (body)  Linearly arranged segments called proglottids form a chain  The Newest segment (immature proglottid) is next to neck and the oldest (gravid proglottid) at tail end



Subclass Eucestoda Segmentation (Strobilation)  Asexual process of forming segments or proglottids  Scolex  neck  young segments (immature)  old segments (mature)  the oldest segments (gravid or ripe)

Subclass Eucestoda  Body wall  Several layers thick  Outer most is“tegument” (nonciliated cytoplasmic syncytium overlying muscle layers) * syncytium= A multinucleated mass of cytoplasm that is not separated into individual cells





Subclass Eucestoda  Body wall  some tapeworms, the surface of the tegument is covered in numerous highly modified microvilli called \"microtriches\"

Subclass Eucestoda  Body wall  Pinocytosis (endocytosis) and exocytosis (excretion) can occur here

Subclass Eucestoda Excretory system  Most through body wall  Protonephridial system(Flame cells) in tapeworms closely resembles that in trematodes



Subclass Eucestoda Nervous system  Typical no specialized sense organs  Continuous along proglottids  Brain in scolex and 2 lateral cords run longitudinally through strobila

Subclass Eucestoda Nervous system  Ring-like commisures in each proglottid  Sensory nerve endings in tegument  No sense organs





Subclass Eucestoda Respiration  Largely anaerobic, but have enzymes for aerobic respiration also

Subclass Eucestoda  Reproductive system  The majority of tapeworms are hermaphrodites  Monoecious Self fertilization within single proglottid and between proglottids  Dioecious Cross fertilization is necessary; Copulation between 2 worms if they bump into each other in the gut of the host

Subclass Eucestoda Reproductive system  Complete reproductive system in each proglottid  Basic structure similar to digenetic trematodes  Vagina and cirrus usually open together through a genital atrium

Subclass Eucestoda Reproductive system  Fertilized eggs usually stored in blind uterus.(except for pseudophyllidean)  Terminal proglottids packed with eggs break off and eggs are freed and pass out through intestine in feces or proglottids crawl out anus by themselves. (cyclophyllidean)

Testes Vitellaria Genital atriu Uterus Vagina Ovary Pseudophyllidean reproductive organ



Cyclophyllidean reproductive organ



Subclass Eucestoda Order Pseudophyllidea (Pseudophyllidean group) Order Cyclophyllidea (Cyclophyllidean group)*

Pseudophyllidean group Family Diphyllobothriidae  Genus Diphyllobothrium  Genus Spirometra

Cyclophyllidean group  Family Taeniidae  Family Hymenolepididae  Family Anoplocephalidae  Family Davaineidae  Family Mesocestoididae  Family Dipylididae

Cyclophyllidean group The body consists of  Head or Scolex  usually provided with suckers and hooks  Strobila  consists of a number of segments or proglottids

Cyclophyllidean group  Between the scolex and the strobila there may be a short unsegmented portion(stem cells) that is often called the neck  Vary in size from a few millimetres to several metres in length

Cyclophyllidean group  The scolex is usually more or less globular and bears four suckers with muscular walls which may be armed with hooks  Anteriorly the scolex may be armed with a protrusible part, the rostellum, which may bear one, two or several rows of hooks

Cyclophyllidean group  These hooks vary much in shape, but generally they may consist of 3 parts  Handle or Base  Guard  Blade  The hooks are sometimes lost, especially when they are small



Cyclophyllidean group  The strobila may consist of a few (Echinococcus spp.) or numerous proglottids (Taenia spp.)  These vary considerably in shape and size in different species

Cyclophyllidean group  The anterior ones are the youngest, and they increase in size and development of their internal parts progresses (strobilation)  The structure of the body is somewhat similar to that of the trematodes

Cyclophyllidean group  The body is covered by a tegument.  Beneath the tegument the body is filled with a parenchyma similar to that of the trematodes  In this lie more centrally, strong bundles of longitudinal muscle fibres

Cyclophyllidean group  Internal to these there is a thinner layer of transverse muscles which divide the body into outer cortical and inner medullary portions  The medulla contains the excretory, nervous and reproductive organs

Cyclophyllidean group  The excretory system consists of  Flame-cells and efferent canals as in the trematodes  There are usually, on either side, two longitudinal canals, a larger central and a smaller dorsal

Cortical portion Medulla portion



Cyclophyllidean group  Nervous system  The central part of the nervous system is situated in the scolex and consists of several ganglia and commissures, from which two large and several smaller nerve trunks run through the strobilia  The main trunks are lateral to the large excretory canals

Cyclophyllidean group  Reproductive system  The male genital organs are the first to develop in the young proglottids or immature segments  Segments in which the reproductive organs have become mature and functional are called mature segments or proglottids