Parasitology Notes

MedicoPlexus

Parasitology Notes

Component 1 – Taxonomy

Classification of 

• Kingdom Protista 
• Kingdom Animalia 
• Phylum Sacromastigophora 
• Phylum Sporozoa 
• Phylum Platyhelminthes 
• Class Cestoda 
• Phylum Nemathelminthes 
• Phylum Arthropoda 
• Class Insecta

Refer to taxonomy/classification document here for diagrams

CLASSIFICATIONS

Kingdom Protista 

Kingdom Protista has phylum sacromastigophora which has subphylums sacrodina and mastigophora. 

Subphylum sacrodina has genus entamoeba which has species histolitica and coli. Subphlum mastigophora has genus typanosoma, leishmania, trichomones and lamella. 

Kingdom Protista has phylum cilidphora which has species balamtidium coli. Kingdom Protista also has phylum sporozoa which has genus taxoplasma and plasmodium. Genus Toxoplasma has species gondii and genus plasmodium has species vivax, malariae, falciparum and ovale.

Kingdom Animalia

Kingdom Animalia has phylum platyhelminthes, nematoda, annelida and arthropoda. 

Phylum playhelminthes has subphylum trematoda and cestoda. Subphylum trematoda has genus fasicola and genus dicrocoelium. Subphylum cestoda has order psedudophyllidea which has genus Diphyllobothrium and order cyclophllidea which has genus taenia. 

Phylum nematoda has order ascaridida which has genus ascaris, order oxyurida which has order enterobius and order trichocephalida which has genus trichocephalus and trichinella. 

Phylum annelida which has order Lumbriculida with genus lumbricus and order haplotaxida which has genus hirudo.

Phylum Sacromastigophora

Phylum Sacromastigophora has sub Phylum Sacrodina which has species Entamoeba Histolytica and Entamoeba amoeba coli. Also has subphylum mastigophora which has Genus Trypanosoma, Genus Leishmania, Genus Trichomonas and Genus Lambila. Genus Trypanosoma has species Trypanosoma Gambiense and Trypanosoma Rhodesiense . Genus Leishmania has species Leishmania Donovani, Leishmania Tropica and Leishmania Braziliensis. Genus Trichomonas has species Trichomonas Tenax, Trichomonas hominis and Trichomonas Vaginalis. Genus Lambila has species Lambila Intestinalis.

Phylum Sporozoa 

Kingdom Protista also has phylum sporozoa which has genus toxoplasma and plasmodium. Genus Toxoplasma has species gondii and genus plasmodium has species plasmodium vivax, plasmodium malariae, plasmodium falciparum and plasmodium ovale.

Phylum Platyhelminthes

Phylum platyhelminthes has subphylums trematodes and cestodes. 

Subphylum trematoda has genus fasicola and genus dicrocoelium. Genus fasciola has species fasciola hepatica. Genus dicrocoelium has species dicrocoelium lanceatum. 

Subphylum cestoda has order psedudophyllidea which has genus Diphyllobothrium and order cyclophllidea which has genus taenia. Genus Diphyllobothrium has species Diphyllobothrium latum. Genus taenia has species taenia solium and taenia saginata. 

Class Cestoda

Class cestoda has order pseudophyllidean which has genus Diphyllobothrium which has species Diphyllobothrium latum. The class also has order cyclophillidea which has genus taenia which has species taenia solium, taenia saginata and echinococcus graulosus.

Phylum Nemathelminthes

Phylum nemathelminthes has class nematoda which has order ascaridida which has genus ascaris, order oxyurida which has genus enterobius and order trichocephalida which has genus trichocephalus and trichinella, Genus ascarius has species ascaris lumbrocoides. Genus enterobius has species enterobius vermicularis. Genus Trichocephalus has species trichocephalus trichiurus. Genus trichinella has species trichinella spiralis.

Phylum Arthropoda 

Phylum Arthropoda has class Crustacea, Arachnida and instecta. 

Class crustacea has genus cyclops and genus diaptomus. 

Class Arachnida has subclass scorpiones, aranei and acari. 

Subclass scorpiones has species euscorpius carpaticus and euscorpius italicus. 

Subclass aranei has species lathrodectes trecymguttatus. 

Subclass Acari has order Acariformes and Parasitiformes. 

Order Acariformes has family sacroptidae which has species sacroptes scabiei, and family demodecidae which has species demodex folliculorum. 

Order Parasitiformes has suborder gamasida which has species Dermanyssus gallinae and suborder Ixodida which has family Argasidae and family Ixodidae.

Class Insecta

Class insecta has orders blattodea, anoplura, heteroptera, aphaniptera and diptera. 

Order blattodea has genus blatta which has species blatta orientalis and blatta germanica. 

Order anoplura has species pendiculus and phthirius pubis. 

Order heteropteran has species cimex lectularis. 

Order aphaniptera has species pulex irritans. 

Order diptera has family Culicidae, muscidae and pyschodidae. Family Culicidae has genus anopheles which has species elutus and superpictus and also has genus culex. Family muscidae has genus Musca which has species Musca domestica and genus glossina which has species palpalis and morsitans . Family psychodidae has species pappataci.

Component 2 – Morphology 

Phylum Sarcomastigophora

• Are unicellular or colonial forms, and may be either autotrophic or heterotrophic
• Have one or more flagella or pseudopods 
• Usually between 10-30µm
• Free living and parasitic amoebas
• Post primitive form of animal forms
• All live in large intestine except E. gingivalis
• Are reproducing by closed mitosis
• E. histolytica is an important pathogenic parasite of humans 

Phylum Sporozoa:

• They are unicellular
• Have a basal body
• Oval or round body
• Rarely they have flagellum or pseudopods
• Micropores on the whole body for ingesting food
• Some species have special structures (Conoid, Rhoptrien, Micronemen ) for penetration of host cells 
• All members of phylum have an infectious stage: sporozoite
• Can be extracellular (e.g., Intestine) and intracellular (e.g., red blood cells)
• They are divided into 2 gender: Female –  Male
• All can produce sexual or asexual reproduction

Class Insecta

• Head of six fused segments
• Three segmented thoraxes with 3 pairs of legs + 2 pairs of wings
• Abdomens consist of a maximum of 11 segments
• Body is encased in more or less rigid sclerotic tissue, connected by a flexible chitinous membrane

Ephalic appendages:

• Converted to sensory organs
• Multijointed antennae, compound/ simple eyes, masticatory organs (chewing organs)
• Simplest form: chewing or biting mouth can be modified for pierce sucking or sponging-lapping

Thorax:

• Composed of prothorax, metathorax and mesothorax
• Each has a pair of legs
• Wings are theoretically on meso- and metathorax but there are degenerations resulting in only 1 pair

Abdomen:

• Number of segments are reduced in more specialized species
• No appendages
• Last segments may by modified for sexual purpose into hypopygrum (male) and ovipositor (female)

Nervous system:

• Chain of neutral ganglia
• 3 main ganglia: protocerebrum, deutocerebrum and tritocerebrum
• From there nerves pass to sensory organs and tissues

Respiratory system:

• Branching tracheal tubes communicating with exterior by spiracies

Circulatory system:

• Poorly developed
• Consists of a dorsal pulsating organ and an aorta and an open body cavity (hemocele)

Digestive system:

• Consist of a foregut, midgut and hindgut
• Consist of a pharynx,  a slender esophagus (Speiseröhre), proventriculus, stomach (midgut), intestine (hindgut), rectum and anus
• In bloodsucking insects, the muscular pharynx acts as a suction pump
• Paired salivary glands open in mouth part

Excretory system:

• Several slender Malpighian tubules that empty into the intestinal canal above the hindgut/midgut junction

Reproductive system:

• Two testes, a seminal vesicle, accessory gland and hypopygium (male)
• Ovaries, oviduct, seminal receptacle, shell and cement glands and ovipositor

Phylum Nematoda

General information: 

• widely distributed in water and soil
• Parasitic species live in plants, arthropods, vertebrates 
• Length between 2mm up to > 1m 
• Separate sexes, men are smaller with a curved posterior and in some species a bursa/spicule

Body: 

• Elongated, cylindrical worm, primarily bilaterally symmetrical
• Anterior end may be equipped with hooks, teeth, plates, setae and papillae for purposes of attachment, abrasion and sensory response
• The supporting body wall consists of an outer, hyaline, unicellular cuticle , a subcuticular epithelium and a single layer of muscular cells
• The cuticle has various surface markings and spines, bosses or sensory papillae 
• The thin subcuticular layer is thickened into 4 longitudinal cords (dorsal, ventral, 2 lateral) – that project into the body cavity and separate the somatic muscle cells into four groups . These cords carry longitudinal nerves and often lateral excretory canals. 
• The Body wall surrounds a cavity within which lie the digestive, reproductive and parts of the nervous and excretory systems. The cavity is lined by connective tissue and a single layer of muscle cells.

Alimentary tract:

• A simple tube extending from the mouth to the anus, which opens ventral a short distance from the posterior extremity
• The mouth is usually surrounded by lips or papillae and in some species, it is equipped with teeth or plates 
• It leads into a tubular or funnel –shaped buccal cavity, which can be expanded for sucking purposes
• Esophagus, lined with an extension of the buccal cuticle, has a striated muscular wall, a triradiate lumen and associated esophageal glands
• The esophagus terminates in a bulbular extension equipped with strong valves
• The intestine is a flattened tube with a wide lumen that follows a straight course from esophagus to rectum and its wall consists of a single layer of columnar cells
• In the female the intestine leads into a short rectum and in the male, it joints with the genital duct to form the common cloaca which opens through the anus.
• Around the anus are papillae which numbers and patterns aid in species identification

Circulatory System:

• Not existent
• The fluid of the body cavity consists of hemoglobin, glucose, proteins, salts, and vitamins and fulfills the function of blood

Nervous System

• Consists of a ring/commissure of connected ganglia surrounding the esophagus 
• From this commissure 6 nerve trunks pass forward to the head and 6 extend posteriorly
• Sensory organs are situated in the labial, cervical, anal and genital regions

Male Reproductive System

• Located in posterior third of the body as a single coiled or convoluted tube
• This tube contains testis, vas deferens, seminal vesicle, and ejaculatory duct
• The Spermatozoa traverse vas deferens -> seminal vesicle ->muscular ejaculatory duct -> cloaca 
• The accessory copulatory apparatus consists of either one or two spicules and at times of a gubernaculums and in some species of wing-like appendages or a copulatory bursa to attach to the female

Female reproductive System

• It is either a single or a bifurcated tube 
• It is differentiated into ovary, oviduct, seminal receptacle, uterus, ovejector and vagina
• The ovum passes from ovary to into the oviduct where it is fertilized. The true shell , a secretory product of the egg, begins to form immediately after sperm penetration 
• In the uterus the protein coat is added as a secretion of the uterine wall
• The daily output of gravid eggs divers from 20 to 200.000 eggs

Excretory System:

• Two lateral canals that lie in the lateral longitudinal cords 
• The two canals join in a bridge near the anterior end 
• From there a terminal duct leads to a ventral pore in the region of the esophagus

Nematodes possess only longitudinal muscles which produces their typical sinuous movement. They remain their position in the intestine by attachment to the mucosa, by attachment with their attenuated end and by retention in the folds of the mucosa. Metabolic processes are anaerobic. Cuticle provides protection against intestinal juices etc. 

They feed by sucking blood, ingestion of lysed tissues, feeding on intestinal contents, or ingestion of nourishment from the body fluids.

The adult worms react to touch, heat, cold and chemical stimulus. 

Phylum Platyhelminthes

   Platy = Flat, Helminth = Worm The phylum represents the early triploblastic forms. The forms have the power of locomotion and bilateral symmetry

• represented both by free living and parasitic forms
• flattened dorsoventrally, leaflike
• no body cavity, space between body wall and alimentary canal is filled with mesenchyme (connective tissue)
• length between 1mm and 20 meters depending on species
• consists of 3 proglottids up to 4000 proglottids depending on species
• head with either 2 or 4 suckers or 4 suckers + rostellum 
• neck: posterior part is region of growth 

• – strobila: region where a chain of segments progressively develops in dorsal direction (segments are called proglottids)
  • each proglottid is essentially a function individual 
  • originate at posterior part of neck and become progressively more mature
  • -the anterior undifferentiated segments become large mature proglottids with completely formed sexual organs. These turn into gravid proglottids , which are basically a uterus filled with eggs. They either break off from the strobila or disintegrate
  • respiration by diffusion
  • reproduction is sexual. Majority of the forms are hermaphroditic
  • triploblastic body (ectoderm, mesoderm, endoderm)
  • 3 muscle layers beneath epidermis, circular/longitudinal/sidelong –> can’t be used effectively due to absent skeleton
• -homogenous, elastic, resistant cuticle/tegument with spinelike structures called microtriches, or microvilli. 

Digestive system

• The blind-ending intestine of trematodes consists of a two-branched gut/coeca with an oral  and a ventral sucker, a prepharynx, pharynx and esophagus; an anus is usually lacking, but a few species have one or two anal pores
• pharynx between mouth and intestine
• undigested food comes out through mouth
• cestodes: no digestive tract, absorb nutrients from host across body wall
• most other flatworms have digestive system 

Excretory system

• -The excretory system consists of protonephridia. These are branching canals ending in so-called flame cells—hollow cells with bundles of constantly moving cilia.

Nervous system

• nerve centers (ganglia), of nervous system and major sense organs are concentrated at anterior end(scolex)
• usually, they have 2 accessory longitudinal nerve trunks extending on each side of the cephalic ganglia.
• there are transverse connections after each proglottids, which consists of male and female reproductive organs

Reproductive system

• with very few exceptions, they are hermaphroditic
• male consists of many testes, vas efferens, vas deferens, seminal vesicle, prostatic gland, ejaculatory duct or cirrus, and cirrus pouch.
• female consists 1-2 ovaries, oviduct, ootype, Mehlis gland, seminal receptacle, vitellaria, vitelline duct, common vitelline duct, vitellaria reservoir, uterus, metraterm
• tapelike body divided into series of segments, or proglottid

• -Each male and female reproductive system may have its own gonopore, or the terminal regions of each system may join to form a common genital atrium and a genital pore
• -Self-fertilization is more common than cross-fertilization
• -Species can be separated by the appearance of their gravid proglottids(different amount of    branches, or shaped like a rosette)

Phylum Arthropoda

• They all are invertebrate animals
• Have an exoskeleton, it is composed of the epicuticle (thin) and procuticle (thick) made of α-chitin
• Segmented body, each with a pair of appendages
  • Head, Thorax, Abdomen
• Jointed appendages
• Characterized by their jointed limbs and cuticles
• Cuticles are replaced by molting
• Size range from microscopic plankton up to forms a few meters long
• Open circulatory system
•  Nervous system is ladder-like with paired ventral nerve cords running through all segments and formed paired ganglia in each segment
• The head is formed by fusion of the ganglia of these segments
• Respiratory and excretory systems vary, for each environment state
• Most arthropods have sophisticated visual systems
  with compound eyes and pigment-pit ocelli
• Have wide range of chemical(taste and smell) and mechanical sensors  
• reproduction and development are diverse
  – individuals of most species remain of one sex their entire lives
  – do internal or external fertilization depending on species
  – most arthropods rely on sexual reproduction
• nervous, muscular, open circulatory, and excretory, digestive, respiratory systems have repeated components
  – have a coelom
  – membrane-lined cavity between the gut and the body wall
• Most arthropods lay eggs, but scorpions are viviparous
• Newly born arthropods have diverse forms, and insects alone cover the range of extremes
• The three-part appearance of many insect bodies and the two-part appearance of spiders
• have two body elements that are not part of this serially repeated pattern of segments
  – an acorn at the front
  –  telson at the rear, behind the anus