PLATYHELMINTHES
Vesselin Alexandrov, PhD Department of Languages and Specialized Training 1 TAXONOMY
Class Turbellaria – Cilliated worms free living worms, 4500 species Class Trematoda (Trematodes) – Flukes endoparasites, 11000 species Class Cestoda (Cestoidea) – Tapeworms endoparasites, 3400 species Class Monogenea – Monogeneans fish ectoparasites, 1100 species
2 WORLD DISTRIBUTION
Free living worms in oceans, seas, freshwater lakes and rivers, and wet habitats
Endoparasites in almost all vertebrates
Ectoparasites, especially on the fish gills
3 Trematoda - Flukes
4 Тrematoda – Flukes Morphology Entirely parasitic life Endoparasites Biohelminths Body Flat, unsegmented, leaf shaped (mostly) Covered by integument, three layers of muscles under it Dimensions: from several mm to 10 cm Oral sucker – for feeding and attachment Ventral sucker – for attachment
5 Тrematoda – Flukes Morphology Digestive system: one opening, muscle gullet (mostly), esophagus, two blind gut branches, no anus Nervous system: ganglion type, pharyngeal ganglion (nervous ganglion ring), two longitudinal nerve cords. No sensory organs Excretory system: protonephridial type, two collecting excretory channels, excretory bladder No respiratory and circulation system: diffusion through all the body surface Reproductive system: hermaphrodites (mostly), allogamy (cross-fertilization) Eggs: ovoid, some of them with operculum
6 Trematoda – reproductive system Hermaphrodites
7 Trematoda – reproductive system Schistosoma
8 Main fluke types Hermaphrodites: Liver flukes: Clonorchis sinensis (South-East Asia, China, India) Fasciola hepatica (cosmopolitan) Fasciola gigantica (up to 10 cm) (Egypt, Tropics) Intestinal flukes: Fasciolopsis buskii (China, South-East Asia) Lung flukes: Paragonimus westermani (South-East Asia, China, India) Paragonimus mexicanus (South America) Sexually differentiated: Blood flukes: Schistosoma haematobium (Egypt, West Asia) Schistosoma mansoni (Africa, South America, Caribbean) Schistosoma japonicum (Far East, Japan, China, Philippines)
9 Liver flukes - morphology Fasciola hepatica (Sheep liver fluke) Size: 3-5 cm Pumpkin seed shaped Organs with tree-like embranchment Dicrocoelium dendriticum (Lancet liver fluke) Size: 6-10 mm Leaf shaped, sharp conical anterior end, round posterior end Blind ended guts, no branches Ovoid ovary and testes, testes at anterior end, uterus at posterior end Opistorchis felineus (Cat liver fluke) Size: 8-13 mm Shape: leaf shaped, sharp anteriorly, round posteriorly Testes at the posterior end, uterus at the anterior end
10 Trematoda operculated eggs
11 Fasciola hepatica (Sheep liver fluke) Life cycle
12 Fasciola hepatica (Sheep liver fluke) intermediate hosts
Lymnaea stagnalis Lymnaea truncatula
13 Fasciola hepatica (Sheep liver fluke) Developmental stages Miracidium Cercaria
Metacercaria Redia
14 Fasciola hepatica (Sheep liver fluke) Pathogenicity: Mechanical damage of bile duct and liver, sometimes diaphragm and lungs Secondary bacterial infection Nutrition and toxic effects Clinical symptoms: Fever, nausea, pain in the right upper abdominal part Hepatomegaly Allergic reactions Diagnostics Fecal helminth ovoscopy – eggs in the feces
15 F. hepatica in a child eye
16 Dicrocoelium dendriticum (Lancet liver fluke) – life cycle
17 Dicrocoelium dendriticum (Lancet liver fluke) - intermediate hosts
Zebrina sp. Helicella sp. Formica sp.
18 Dicrocoelium dendriticum Lancet liver fluke Pathogenesis Mechanical damages of the bile and liver duct wall Secondary bacterial infections Toxic effects Clinical features The massive invasion causes heavy injuries of liver parenchymal tissue Hepatic cirrhosis Bile duct obstruction Diagnostics Helminth ovoscopy: eggs in stools or in the duodenal juice
19 Opisthorchis felineus (Cat liver fluke) life cycle
20 Opisthorchis felineus (Cat liver fluke) hosts
Scardinius Barbus barbus erythrophthalmus (barbel) (rudd)
Leuciscus cephalus Tinca tinca (chub) (tench, doctor fish)
Bithynia leachii Cyprinus carpio Esox lucius (carp) (Northern pike)
21 Opisthorchis felineus (Cat liver fluke) Pathogenesis Pancreatic or hepatic injuries Inflammation of bile duct Secondary bacterial infection Clinical features Pain in the right upper abdominal part, chills, nausea, vomiting Allergic reactions Liver enlargement and Opisthorchis felineus tenderness, cirrhosis on a late in tissue cross sections stage Diagnostics Helminth ovoscopy: eggs in stools or in the duodenal juice
22 Blood flukes (Schistosoma sp.) – morphology and differences
Diecious. Sexually differentiated Male – short and thick, up to 15 mm, gynecophoric canal Female – thin and long, up to 26 mm, fits into the gynecophoric canal Lack of muscular pharynx Both of the intestines reunite after bifurcation and form a single canal The eggs are non-operculated No redia and metacercaria stage Cercariae have a forked tail and actively penetrate the host’s skin
23 Trematoda stages comparison
24 Schistosoma eggs – non-operculated Schistosoma – life cycle
26 Schistosoma (S. japonicum, S. mansoni, S. haematobium) – intermediate hosts
Oncomelania sp. Bulinus sp. Australorbis sp. (Biomphalaria sp.) 27 Miracidium – ciliated and motile form
28 Cercaria with a forked tail
29 Cercaria with a forked tail
30 Cercaria with a forked tail
31 Cercaria with a forked tail
32 Schistosoma mansoni Schistosoma mansoni - male
34 Schistosomiasis – the second world distributed parasitic disease
35 Schistosomiasis – World distribution
36 Schistosomiasis Pathogenesis and clinical features Swimmer’s itch – after skin penetration Cercarial dermatitis and lesions at the site of entry Anaphylactic and toxic symptoms (fever, headache, urticaria) Enlarged liver, palpable spleen Egg deposition Painless hematuria Hyperplasia and inflammation of bladder and intestinal mucosa Chronic stage and tissue proliferation Chronic cystitis Generalized hyperplasia and fibrosis of vesical and intestinal mucosa Pseudoabscesses due to infiltration of lymphocytes, plasma cells, eosinophils at the site of egg deposition Caliculi in the bladder due to oxalate deposition and uric acid crystals Carcinoma of the bladder and the large intestine Diagnostics Eggs in stools and urine Immunology tests
37 Hystopathological tissue cross section of urinary bladder with eggs of Schistosoma haematobium,
Schistosoma eggs and adult worms in lung tissue
38 Swimmer’s itch
39 Tortuous Varicosities in Chronic Schistosomiasis
40 Way of schistosomiasis distribution
41 Ernst Haeckel's “Kunstformen der Natur” or “Art forms of nature”
42