The Short Textbook of Medical Helminthology Satish Gupte
INDEX
Page numbers followed by f refer to figure and t refer to table
A
Albendazole 125
Allergic syndrome 6
Alopecia 127
Amnesia 56
Ancylostoma
braziliense 35, 68
caninum 9, 68, 114
duodenale 3, 5, 6, 30, 34, 35, 120
lesions of 32f
life cycle of 31f
morphology of 30f
secreted proteins 120
Anemia, severe 18
Angioneurotic edema 130
Angiostrongyliasis 115
Angiostrongylus cantonensis 69, 115
Anorexia 33, 130
Aphasia 56
Appendicitis, acute 18
Artemethur 133
Artemisinin derivatives 133
Artesunate 133
Artificial fertilizer 51
Ascariasis 125, 127, 130
Ascaris 132
lumbricoides 1, 37, 9, 2629, 132
adult worms of 25
vermicularis 4
B
Bacterial infection 93
Baylisascaris procyonis 114, 115
Beef tapeworm 47
Bile duct epithelium and carcinogen exposure, hyperplasia of 106
Biomphalaria
alexandrina 75
glabrata 75
pfeifferi 75
Blindness 56
Blood flukes 104
Bloody diarrhea 18
Blurred vision 56
Bronchospasm 127
Brugia
bancrofti 7
malayi 57, 95, 98, 118, 132
microfilaria of 96f
C
Capillaria
aerophilia 113
hepatica 113
philippinensis 113
Capillariasis 113
Caridina 36
Casoni's test 84, 86
Cerebrospinal fluid 125
Cestodes
features of 2
intestinal 128
Charcot Leydin crystals 29
Chinese liver fluke 35
Chlonorchis sinensis 36
Clonorchiasis 125, 129
Clonorchis sinensis 37, 35, 37, 104, 106, 131
life cycle of 36f
Congestive heart failure 18
CpG islands, aberrant hypermethylation of 107
Cramps, abdominal 131
Crystoluria 130
Cutaneous larva migrans 67, 125, 130, 132
Cysticercosis 22, 125, 129, 131
Cysticercus
bovis 50
cellulosae 55, 55f
D
Dexamethasone 126
Diarrhea 33, 127, 12931
Diatoma sinensis 35
Diethylcarbamazine 126
Diphyllobothriasis 129
Diphyllobothrium latum 2, 4, 5, 7, 4143
life cycle of 43f
Dipylidium caninum 4
Distomat buski 38
Dizziness 128130
Dracunculiasis 7
Dracunculus medinensis 36, 62, 64
extraction of 64f
life cycle of 63f
Dragon worm 61
Drowsiness 128, 130
Drug metabolizing enzymes, activation of 106
E
Echinococcosis 80, 126
hydatidosis 80
Echinococcus 132
granulosus 2, 7, 80, 83, 86, 87, 122, 131
life cycle of 82f
morphology of 81f
multilocularis 80, 88, 89
Emerging helminthic infections 111
Encephalitis 56
Enterobius vermicularis 37, 22, 23, 109, 132
life cycle of 24f
morphology of 23f
Enzyme linked immunosorbent assay 47
Eosinophilic enteritis 114
Epigastric discomfort 33
Epilepsym, Jacksonian type of 56
Esophagostomiasis 112
F
Fasciola hepatica 4, 5, 7, 10, 38, 6567, 131, 132
life cycle of 66f
Fasciolopsis buski 3, 4, 38, 39
life cycle of 39f
Ferrissia tenuis 71, 72
Fever 126, 129
Filaria
bancrofti 90
sanguinis hominis 90
Filarial worms 1
Filariasis 8, 90, 132
lymphatic 125
Flukes, intestinal 132
Food borne trematode infections 8
G
Gastrointestinal disorders 130
Giant intestinal fluke 38
Gnathostoma 111
binucleatum 111
spinigerum 69
Gnathostomiasis 111
Gordius medinensis 4
Guinea worm 61
infection 6
H
Headache 126131
Helminth
infections, treatment of 131t
pathogenic role of 5
Helminthiasis 4
Helminthic
disease 5, 6
gastrointestinal nosocomial infections 109
parasites, vaccines in 120
vaccines 119, 122
Helminths 1
causing nosocomial infections 109t
features of 2
infections, control of 118
intestinal 11
worldwide
prevalence of 6t
status of 7
Hemorrhage 33
Hepatitis 105, 130
Hepatocellular carcinoma 105
Hookworm 1, 127, 130, 132
disease 6
vaccines for 120
infection 126
Human anti-helminthic disease vaccines 122, 122t
Hydatid
cyst 84
fate of 85
morphology of 82f
disease 80, 122
sand 84
Hydrocephalus 56
Hymenolepis nana 2, 57, 44, 46, 109, 131, 132
life cycle of 46f
morphology of 45f
Hymenolepsiasis 129
I
Infection, sources of 6
Intense prutitus 33
Intestinal helminthiasis, treatment of 124
Ivermectin 125
K
Katayama syndrome 78
manifestations of 78
L
Larva 20
migrans 67
Liver fluke 104
infections 106
Loa loa 7, 97, 132
microfilaria of 98f
Loeffler's syndrome 29
Loiasis 125
Lymph node, fibrosis of 93
Lymphangitis, causes of 93
Lymphatic
obstruction, causes of 93
vessels, fibrosis of 93
M
Macracanthohynchus hirudinaceus 10
Maculopapular rash 33
Magnetic resonance imaging 85
Malaise 129
Manson's blood fluke 74
Mansonella
ozzardi 7
perstans 7
Mansonia annulifera 96, 97
Mebendazole 126
Membrane filtration 94
Metrifonate 127
Muscle
biopsy 14
digestion 14
enzymes 14
Myalgia 126
N
Nausea 33, 126, 127, 128, 129, 130
Necator americanus 3, 5, 6, 34, 68, 120, 122
morphology of 34f
Nematodes
features of 3
significance of 3
Neurocysticercosis 107
Niclosamide 128
Nitazoxanide 132
Non-food substances, ingestion of 18
Nosocomial infections 110
O
Obliterate endolyphangitis 93
Obstruction, lymphatic 5, 94
Occult filariasis 94
Oesophagostomum bifurcum 112
Onchocerca volvulus 99, 101, 122, 132
Onchocerciasis 125
Oncogenic helminths 104
Opisthorchiasis 129
Opisthorchis
felineus 8, 104, 106
sinensis 35
viverrini 104, 106
infection 106
Oriental lung fluke 58
Oxamniguine 128
P
Pain, abdominal 126, 127, 129
Paloemonetes sinensis 36
Paragonimiasis 129, 131
Paragonimus westermani 3, 4, 6, 7, 58, 60, 61, 131
life cycle of 60f
Phylum
nemathelminthes 1
platyhelminthes 1
Pinworm infection 6
Pork tapeworm 52
Praziquantel 126, 129
Pruritis 126, 128
Pulmonary distomiasis 58
Puritis 129
Pyrantel pamate 129
R
Radical allergosorbent test 21
Reversible alopecia 126
River blindness 122
S
Saponin lysis 94
Schistosoma
haematobium 3, 5, 6, 71, 73, 75, 104, 105, 121, 122, 127
infection 74, 105
life cycle of 72f
japonicum 6, 10, 75, 7779, 104, 105, 122, 133
life cycle of 78f
mansoni 5, 6, 10, 74, 76, 104, 105, 119, 122
infections 128
life cycle of 75f
Schistosomes 1, 104, 132
Schistosomiasis 71, 127, 128, 129
vaccines for 121
Seizures 128, 130
Serpent worm 61
Simulium
damnosum 118
neavei 118
Skin test 15
Stevens-Johnson syndrome 130
Streptomyces avermitilis 125
Strongyloides
stercoralis 2, 6, 7, 1922, 68, 109, 110, 132
infection 21
life cycle of 20f
Strongyloidiasis 6, 125, 130
Subcutaneous nodules 56
Swimmer's itch 78
T
Taenia
cucurbitina 52
latum 4
saginata 2, 5, 7, 47, 48, 51, 53, 54, 131, 132
life cycle of 50f
morphology of 48f
solium 2, 47, 5256, 104, 107, 109, 121, 122, 131
adult worms of 52f
cysticercus 55
life cycle of 53f
Thiabendazole 130
Thrombocytopenia 127
Tissue helminths 58
Toxocara canis 7, 68, 69
Toxoplasma gondii 7
Trematodes
features of 2
intestinal 129
Trichina worm 11
Trichinella spiralis 3, 6, 7, 11, 14f, 119
life cycle of 13f
pathogenesis of 12f
Trichinellosis 126, 127
Trichostrongyloidiasis. 127, 130
Trichuriasis 126, 127
Trichuris trichiura 1, 57, 15, 18, 132
life cycle of 17f
morphology of 16f
V
Vertigo 127
Visceral larva and migrans 126, 127, 130, 132
Vomiting 126128, 130
W
Wuchereria
bancrofti 5, 6, 8, 90, 92, 93, 9598, 118, 132
diagnosis of 94
life cycle of 92f
microfilaria of 91f
malayi 95
pacifica 90
X
Xenodiagnosis 14
×
Chapter Notes

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Introduction to Helminths1

 
HELMINTHS
Helminth means worm (Greek helmins – worm). They are multicellular, bilaterally symmetrical, elongated, flat or round and three germ layered (triploblastic) metazoan. They are divisible into the following phyla.
  1. Phylum platyhelminthes: They are flat, leaf-like or tape-like segmented, mostly hermaphrodite. Their alimentary canals incomplete or entirely absent and do not possess a body cavity. Human pathogenic helminths of this phylum are of two classes: the cestodes and the trematodes. They infact are the helminths of low organization.
  2. Phylum nemathelminthes: They are elongated, cylindrical, unsegmented bodies with separate sexes, alimentary canal is complete and body cavity is very well present. There is no circulatory system. The body is of an outer layer of longitudinal muscles and a simple excretory system. They are better organized than platyhelminthes.
Table 1.1   Differences between cestodes, trematodes and nematodes
Features
Cestodes
Trematodes
Nematodes
Shape
Tape-like and segmented
Leaf-like and unsegmented
Elongated, rounded cylindrical and unsegmented
Sexes
Not separate
Not separate except in Schistosoma haematobium
Separate
Head end
Suckers usually with hooklets
Suckers without hooklets
Neither suckers, nor hooklets. Buccal capsule may be well developed
Alimentary canal
Absent
Present but incomplete with no anus
Present and complete with anus
Body cavity
Absent
Absent
Present
Examples
Tapeworms
Flukes
Roundworms
 
Top Helminths According to the WHO
  • Ascaris lumbricoides
  • Hookworms
  • Trichuris trichiura
  • Filarial worms
  • Schistosomes.
Above mentioned helminths can even cause quite a number of deaths.2
 
FEATURES OF HELMINTHS
  • Helminths do not multiply in the body of humans. However, Strongyloides stercoralis and Echinococcus granulosus are exceptions.
  • The outer layer or the tegument is quite tough. It may resist intestinal digestion of living worm.
  • Helminths move by muscular contraction and relaxation. Suckers present in some helminths, may help in their movement. However, helminths have no special organs of movement.
  • True body cavity is absent.
  • In some helminths, the digestive system is either rudimentary or altogether absent. They get predigested nutrients from humans.
  • The reproductive system is highly developed.
  • The excretory system is just sufficient.
  • The nervous system is quite primitive.
  • Many helminths may need more than one intermediate host to complete their life cycle.
  • Environmental factors, food habits, practices or customs, etc. influence and modify the transmission of helminthic diseases.
  • Preparation of vaccine is difficult as helminths are multicellular.
 
FEATURES OF CESTODES
  • They are dorsoventrally flattened, segmented and tape-like.
  • Their size varies from a few millimeters to many meters.
  • Habitat of adult worms is intestinal canal of the host.
  • The body of adult worm comprises head (scolex), neck and strobilla.
  • The strobilla contains a large number of proglottids (segments).
  • Cestodes are hermaphrodite.
  • Alimentary canal is absent.
  • Excretory and nervous systems are present.
  • Suckers (cup-like) are present on the scolex. Scolex may bear hooks and rostellum.
  • Reproductive system is highly developed.
  • Examples of cestodes are Diphylobothrium latum, Echinococcus granulosus, Tenia solium, Tenia saginata and Hymenolepis nana.
 
FEATURES OF TREMATODES
  • They are dorsoventrally flattened like a leaf.
  • They are also called fluke.
  • They have segmented body which is covered with tegument.
  • The size varies from 1mm to 3 cms sucker or more.
  • They have two suckers: (a) anterior sucker also called oral sucker (b) posterior sucker with which parasite is attached to the host.
  • Trematodes are hermaphrodite except schistosomes.
  • Body cavity is not present.
  • They lay eggs (oviparous).
  • The alimentary tract is incomplete.
    3
  • The excretory system and nervous system are present.
  • Reproductive system is highly developed.
  • Eggs are operculated except in schistosomes.
  • Examples are Schistosoma haematobium, Paragonimus westermani, Fasciolopsis buski, Clonorchis sinensis, etc.
 
FEATURES OF NEMATODES
  • They are cylindrical and elongated which tapers at both ends.
  • Sexes are separate and males are smaller than females.
  • Size varies from 1 mm (Trichinella spiralis) in length to more than 1 m (Dracunculus medinensis).
  • The cuticle is generally smooth. Striation, ridges, spines, bristles, etc. may be present which are utilized for the identification of worm.
  • Alimentary canal is usually complete.
  • In the body cavity, digestive, genital and other systems float.
  • Circulatory system is absent.
 
SIGNIFICANCE OF NEMATODES
  • More than a billion people are infected with one or more species of intestinal nematodes all over the world.
  • They are more common in areas with poor faecal sanitation especially in developing countries.
  • Nematodal infection may cause malnutrition and diminished working stamina. They are not fatal.
  • Zoonotic nematodal infection do occur, e.g. trichostrongyliasis, capillarias abdominal angiostrongyliasis and anisakiasis.
  • The life cycle is quite varied. Strongyloides stercoralis and Enterobius vermicularis may be transmitted from person to person. On the other hand, Ascaris lumbricoides, Ancylostoma duodenale and Necator americanus may have to pass through soil for development.
  • Heavy burden of adult worms require repeated exposure to parasites in its infectious form (larva or egg). It needs so because helminths fail to replicate themselves. Hence, clinical diseases are seen only in those patients who are prolonged residents in endemic areas.
  • IgE and eosinophilia in abnormal levels must prompt the clinicians to look for occult helminthiasis.
  • It appears as if significant immunity to intestinal nematodes does not develop.