Veterinary Parasitology Lecture Notes PDF

Veterinary Parasitology Helminthology and Immune Parasitology Code: PAR314 Dr. Mohamed Abdelmoghny [email protected] / [email protected] https://linktr.ee/dr_vet98  Genus: Taenia T. multiceps...

Veterinary Parasitology Helminthology and Immune Parasitology Code: PAR314 Dr. Mohamed Abdelmoghny [email protected] / [email protected] https://linktr.ee/dr_vet98  Genus: Taenia T. multiceps Taenia of Dog ▪ Synonym: Multiceps multiceps. ▪ Final host: Dogs. ▪ Intermediate host: Sheep, cattle, man may be accidentally infected with larval stage. ▪ Metacestode: Coenurus cerebralis. ▪ Disease condition: Gid, sturdy, staggers. ▪ Habitat: Brain and spinal cord (intermediate hosts); small intestine (final hosts). ▪ Geographical distribution: Worldwide. ▪ Morphology: ▪ Gross: The adult tapeworm is up to 100 cm long, generally similar to that of Taenia. In ruminants and man, the mature metacestode, Coenurus cerebralis, is present in the brain and spinal cord. It is large fluid filled transparent bladder up to 5 cm or more in diameter as the size of a hen’s egg. Clusters of macroscopic scolices can be seen by the naked eye attached to the inner wall. No broad capsules or daughter cysts. ▪ Microscopic: The coenurus bears clusters of several hundred invaginated protoscolices on its internal wall. ▪ Life cycle: It is similar to Taenia Spp. The eggs when ingested by sheep or other ruminants are carried in the blood to the brain or spinal cord where each develops into the larval stage, coenurus cerebralis. The coenurus takes about 8 months to mature in the central nervous system and then develops clinical signs. The cysts in sheep and goats often persist throughout the life of the animal. The life cycle is completed when the final host, dog eats an infected sheep brain or spinal cord. ▪ Pathogenesis: The effect of the adults resembles those of adult Taenia spp. The Coenurus causes damage to the brain tissue or spinal cord resulting in neurological disturbances, pressure atrophy of the brain and bones of skull adjacent to the cyst. Acute or chronic coenurosis can occur. Veterinary Helminthology 138  Coenurosis ▪ Definition: Infestation of animal or human C.N.S. by Coenurus cerebralis (larval stage of Taenia multiceps). The disease usually occurs in sheep, rarely in cattle and accidentally in man (usually shepherds). ▪ Mode of infection: By swallowing the eggs of Taenia multiceps with food contaminated by faeces of infected dogs. ▪ Pathogenesis and clinical signs: In sheep: C. cerebralis causes clinical syndrome known as gid, Staggers or sturdy. Acute disease is likely to occur when sheep are grazed on pasture heavily contaminated with faeces from untreated dogs. The migration of large numbers of larval stages through the brain can rapidly lead to neurological dysfunction and death. Chronic disease presents as a progressive focal lesion of the brain with signs of neurological dysfunction appearing about 3–6 months from initial infection and is usually seen in sheep of 6–24 months of age. Clinical signs depend on the location and size of the cyst or cysts and include circling behaviour (The animals hold their head to one side and turns in a circle towards the affect side (due to the associated meningoencephalitis), visual defects (blindness in the eye on the opposite side), uncoordinated jerky gait ( affect the spinal cord and partially or wholly paralysis of legs particularly hind limbs occur). In man: C.N.S. is affected, rarely spinal cord. There is headache and epilepsy. In spinal cord, it leads to paraplegia. ▪ Diagnosis: X-rays or serology. Differential diagnosis with infection of Listeria monocytogenes, Oestrus ovis. ▪ Treatment: Surgical removal is possible if the cyst is situated on the brain surface. This may be detected by local softening of the skull or by detailed neurological examination. However for many cases there is no treatment. ▪ Control: Regular de-worming of dogs with an effective anthelmintic and proper washing of vegetables. Veterinary Helminthology 139  Genus: Taenia T. serialis Taenia of Dog ▪ Synonym: Multiceps serialis. ▪ Final host: Dogs. ▪ Intermediate host: Rabbit and rarely man. ▪ Metacestode: Coenurus serialis. ▪ Habitat: small intestine (definitive host); intramuscular and subcutaneous connective tissue (intermediate host). ▪ Geographical distribution: Worldwide. ▪ Morphology: ▪ The adult tapeworm is around 70 cm long. In rabbit and man, the mature metacestode, Coenurus serialis, is present in subcutaneous tissues. It differs from C. cerebralis in having scolices arranged in streaks or lines or strands (as the name ‘serialis’ implies) usually radiating form a central point and may develop internal and external daughter cysts. ▪ Life cycle: Infection of the intermediate host is through ingestion of tapeworm eggs shed by dogs. The intermediate stage Coenurus serialis is found in the rabbit, usually subcutaneously or in the intermuscular connective tissue. The final host is infected by ingesting the metacestode stage. ▪ Pathogenesis: Infection is usually asymptomatic in both the definitive and the intermediate host. ▪ Diagnosis: Infection of the intermediate host is detected through the presence of cysts in subcutaneous or intramuscular connective tissue. ▪ Epidemiology: There is a high prevalence in hunting dogs. Veterinary Helminthology 140  Family Taeniidae Genus: Echinococcus ▪ The adult is the smallest cestodes found in the small intestine of dog, fox and Species: E. granulosus wild carnivores. ▪ It measure 2-7 mm long, with 3 to 4 proglottids (rarely up to 6) and therefore it’s difficult to find in the freshly opened intestine. E. g. granulosus ▪ The scolex has rostellum which is armed with 2 rows of taenioid hooks (30-60 in number). E. g. equinus ▪ The body consists of scolex, neck and strobila (one immature, 1-2 mature and 1-2 gravid proglottids). Species: E. multilocularis ▪ The mature segment contains single set of genital organs, genital pores alternate irregularly and normally open on the posterior half of segment. ▪ The terminal gravid segment occupying about half the length of the complete tapeworm. ▪ Ovary is bilobed, kidney-shaped, testes 40-65 and the uterus is well-developed diverticula (pouches) in the gravid proglottid (400-800 eggs). ▪ The metacestodes, hydatid cyst, is found in liver and lungs of herbivores, pig and man. ▪ The eggs are typically taeniid egg and measure 32-36 × 25-30 μm and the embryophore is radially striated with a six-hooked oncosphere. Veterinary Helminthology 141  Genus: Echinococcus E. granulosus Dwarf dog tapeworm ▪ Common name: Dwarf dog tapeworm. E. g. granulosus ▪ Final host: Canids, mainly dogs. ▪ Intermediate host: Sheep, cattle, pig and man (Sub. granulosus) and equine (Sub. E. g. equinus equinus). ▪ Metacestode: Unilocular hydatid cysts. ▪ Habitat: Mainly liver and lungs (intermediate hosts); small intestine (definitive host) ▪ Geographical distribution: Worldwide (Sub. granulosus) and Europe (Sub. equinus). ▪ Morphology: ▪ Gross: Hydatid cysts are large fluid-filled vesicles, 5–10 cm in diameter, surrounded by a thick fibrous capsule of host origin followed by a thick outer laminated wall and an inner germinal layer which is of parasitic origin. ▪ Microscopic: The germinal layer produces numerous scolices and small vesicles or brood capsules, each containing up to 40 scolices, invaginated into their neck portions and attached to the wall by stalks. Brood capsules may become detached from the wall of the vesicle and float freely in the vesicular fluid and form ‘hydatid sand’. ▪ Infective stages: Hydatid cyst for D/H and E. granulosus eggs for I/H. Veterinary Helminthology 142 Life cycle: ▪ Life cycle: Indirect (one intermediate hosts is required). ▪ Developmental stages: The eggs pass with the faeces of dogs after disintegration of the gravid proglottid in the intestine (one gravid segment is shed every 1-2 weeks). These eggs (can survive several months to 2 years in pasture) are accidently ingested by I/H with grasses and water. The eggs hatch in the intestine and released oncospheres penetrate the gut wall and travels to the liver and/or the lungs. The oncospheres metamorphose into the larval stage (hydatid cyst) and maturity being reached in 6–12 months. The size of the cyst vary from 5-10 cm in diameter embedded in the organs but may reach to 50 cm diameter in the abdominal cavity and contain several litres of fluid. Sometimes, complete daughter cysts are formed either inside the mother cyst or externally and may be carried to other parts of the body to form new hydatids. The final host acquires the infection by ingestion the fertile hydatids, then the wall is digested off and scolices are released in the small intestine where becomes adults. ▪ Prepatent period: 40-50 days. ▪ Pathogenesis and clinical signs: The pathogenicity based on location, size and number of the cysts. ▪ In Dogs: The adult tapeworm is harmless to dogs (echinococcosis). In large numbers, enteritis may be seen in dogs. ▪ In Domestic animals: The hydatid in the liver or lungs is tolerated without any clinical signs, and the majority of infections are only revealed at the abattoir. Metastasis and pressure by growing cyst may cause a variety of clinical signs (cystic Hydatidosis). ▪ In Man: Digestive disturbances and possibly ascites when the liver is infected. Dyspnoea and pulmonary oedema when occur in the lungs. Rupture of the cyst can lead to fatal anaphylactic shock. Veterinary Helminthology 143  Genus: Echinococcus E. multilocularis Dwarf fox tapeworm ▪ Common name: Dwarf fox tapeworm. ▪ Final host: Wild canids (foxes, wolves and bears). ▪ Intermediate host: Rodents, some larger mammals and accidentally man. ▪ Metacestode: Multilocular or alveolar or malignant hydatid cyst. ▪ Habitat: Lower small intestine (final hosts); liver also lungs, brain, muscles, lymph nodes (intermediate hosts) ▪ Geographical distribution: Worldwide mainly Northern hemisphere. ▪ Disease/Pathological condition caused: Alveococcosis or alveolar echinococcosis (D/H), alveolar Unilocular hydatid cysts hydatidosis (I/H). ▪ Morphology: ▪ Gross: It’s generally similar to E. granulosus. ▪ Microscopic: The scolex has four suckers and possesses a double row of large and small hooks. genital pores are in front of the middle of each segment. The uterus is sac-like with no lateral pouches in the terminal proglottid. Gravid segments contain around 200–300 spherical eggs. The structure of the metacestode consists of a germinative gelatinous matrix that forms multiple compartments (multilocular). ▪ Life cycle and pathogenesis: As E. granulosus. The larval metacestode stage develops primarily in the liver which is invasive, extending locally and capable of systemic metastases to other sites. Multilocular hydatid cysts Veterinary Helminthology 144 Epidemiology: ▪ E. g. granulosus; the sheep is the natural intermediate host, in parts of the Middle East the camel is the main reservoir of hydatids. Human infection being by accidental ingestion of oncospheres from the coats of dogs, or from vegetables and other foodstuffs contaminated by dog faeces. ▪ E. g. equinus; highly specific for the horse and the eggs do not develop in the sheep. The horse strain does not appear to be infective to man. ▪ E. multilocularis; human can be infected following contact with the contaminated fur of foxes and wolves or eating vegetables or fruit contaminated by infected foxes. Diagnosis: ▪ Diagnosis of infection in dogs with adult tapeworms is difficult, because the segments are small and are only shed sparsely. The egg is very difficult to differentiate from other taeniid eggs. ▪ Administration of purgative anthelmintics (arecoline hydrochloride, 2 mg/Kg BWt orally) so that the whole tapeworm is expelled in mucus and can be searched for in the faeces for confirmatory diagnosis. ▪ Immunodiagnostic tests have been developed that are based on the faecal antigen detection, antibody sandwich ELISA technique. Treatment: ▪ Echinococcus is more difficult to remove than Taenia, but several drugs, praziquantel, are available highly effective. After treatment it is advisable to confine dogs for 48 hours to facilitate the collection and disposal of infected faeces. Control: ▪ Regular treatment of dogs to eliminate the adult tapeworms (four times/year) and exclusion from their diet of animal material containing hydatids. Denying dogs access to abattoirs, and where possible, by proper disposal of sheep carcases on farms. Veterinary Helminthology 145  Hydatid cyst ▪ Definition: It is the larval stage of Echinococcus present in different tissues of the intermediate hosts. ▪ Types of hydatid cyst: Unilocular (fertile or sterile) or multilocular hydatid cyst. ▪ Morphology of unilocular hydatid cyst: ▪ Size: Varying in size from a tennis ball to man’s fist and its diameter might reach 20-50 cm. ▪ Shape: Spherical vesicle, opaque white in colour, filled with pale yellow fluid called hydatid fluid. ▪ Wall: Composed of an outer fibrous layer which surrounds the cyst and is formed by the host tissue as a defence mechanism. The proper cyst wall is formed of two layers an outer inert thick laminated non-nucleated layer and an inner thin active germinal layer. ▪ Contents: 1-Solitary scolices: Scolices are attached to the germinal layer. 2-Brood capsules: Formed of a group of scolices surrounded by a thin membrane. 3-Solitary scolices and brood capsules eventually fall into the cavity of the cyst. 4- Hydatid fluid. 5-Calcerious corpuscles (chalk bodies). 6-Taeniidae hooks.7-Endogenous daughter cysts. ▪ Daughter cysts: Usually formed in the same infected organ and may be exogenous or endogenous. 1- Exogenous daughter cyst: Surrounded by laminated and germinal layers. They herniate through a weak point in the fibrous capsule due to increase in the intracystic pressure. 2- Endogenous daughter cysts: They fall into the mother cavity. Grand daughter cysts may be formed. ▪ Hydatid sand: If we aspirate the contents of the cyst and the aspirate left to sediment in a conical flask, the sediment is known as hydatid sand and the supernatant clear fluid as hydatid fluid. Hydatid sand looks like granules of soft sand and is formed of scolices, brood capsules, newly formed daughters cysts and degenerating scolices giving rise to chalk bodies (calcerious corpuscles) and Taeniidae hooks. All these structures are microscopic. ▪ Sterile cyst: The cyst in which the germinal layer fails to produce scolices or brood capsules. They are common in unsuitable intermediate hosts as man. ▪ Multilocular hydatid cyst: consists of a germinative gelatinous matrix that forms multiple compartments (locules) with few scolices. Veterinary Helminthology 146  Differences between Unilocular and Multilocular hydatid cysts Character Unilocular hydatid cyst Multilocular or Alveolar hydatid cyst Adult Echinococcus granulosus Echinococcus multilocularis Definitive host mainly dogs foxes and bears. Intermediate host Herbivorous animals, man Rodents, accidentally man Size and growth Slowly growing and reach 20 cm in diameter Rapidly growing Outline Well defined and spherical Ill-defined and irregular Fibrous capsule Surrounded by fibrous capsule No fibrous capsule Laminated layer Present- thick Absent or very thin Habitat Different organs Mainly liver Locule and free fluid Cyst is formed of one locule containing fluid and Cyst formed of many locules containing gelly-like Fertility thousands of scolices (fertile) matrix in which few scolices are embedded (sterile) Daughter cyst Present as internal and external daughter cysts in Exogenous and branched daughter cyst the same infected organ Brood capsules Present Absent Metastasis No metastasis into other organs Metastasis is common Geographical distribution Worldwide Europe, Asia, North America, Japan Surgical removal Can be removed Can not be removed Veterinary Helminthology 147  Hydatid disease ▪ Definition: Infestation of the human tissues by the larval stage of Echinococcus granulosus (Hydatid cyst). ▪ Mode of infection: 1.Playing, fondling and kissing of infected dogs and ingestion of eggs of E. granulosus. 2.Ingestion Echinococcus granulosus of food or water contaminated with the eggs of excreted in dog faeces. ▪ Pathogenesis: 1.Depend on the location (liver, lung brain and any other organ), size and number of the cyst. 2.The cysts cause pressure and tumour like symptoms. 3.Rupture of the cyst causing secondary cysts and anaphylactic shock. ▪ Diagnosis: 1.Clinical picture ( cystic lesion). 2.High eosinophilia. 3.Intradermal test (Casoni’s test). 4.Serological test as ELISA. 5.Precipitation reaction. 6.X-ray picture, CT and U/S. ▪ Treatment: 1.Surgical removal. 2.Killing of the germinal membrane by injection of (10% formalin or hypertonic saline or alcohol) in the cyst. 3.Medical treatment (if surgery is contraindicated) mebendazole 20-40 mg/kg/d for 3 months. ▪ Control: Periodic treatment of dogs. Avoid playing, fondling or kissing of dogs. Proper washing of vegetables. Avoid entrance of dogs into slaughter houses. Veterinary Helminthology 148 Order Cyclophyllidea (Eucestoda) Family: Dilepididae ▪ Adult parasites are found in mammals and birds. Genus: Dipylidium ▪ Suckers are mostly armed. ▪ Presence of retractable rostellum which is usually armed with D. caninum one or more rows of rose-thorn shaped hooks. Genus: Amoebotaenia ▪ Presence of either one or two sets of genital organs in each mature segment. A. cuneata ▪ Uterus is sac- like or may be break into egg capsules or replaced by par-uterine organ. Genus: Choanotaenia ▪ The intermediate stage is a cysticercoid. C. infundibulum Veterinary Helminthology 149  Genus: Dipylidium D. caninum Common dog tape worm ▪ Common name: Double-pored or cucumber seed tapeworm. ▪ Final host: Dog, cats and occasionally human particularly children. ▪ Intermediate host: Fleas (Ctenocephalides spp, Pulex irritans) and lice (Trichodectes canis). ▪ Metacestode: Cysticercoids. ▪ Habitat: Small intestine. ▪ Geographical distribution: Worldwide. ▪ Morphology: ▪ Gross: Dipylidium is a much shorter tapeworm than Taenia, 15-50 cm in length and maximum length being about 80 cm. The mature and gravid segments have a characteristic elongate oval shape resembling cucumber seeds (cucumber seed tapeworm). ▪ Microscopic: The scolex has unarmed suckers and a protrusible (retractable) conical rostellum, which is armed with 3-5 rows of small rose-thorn shaped hooks. The mature proglottid has double sets of genital organs, with bilateral genital pores opening on each margin (double-pored tapeworm). The ovary and vitelline gland form resembling a bunch of grapes on either side and testes scattered throughout the proglottid. The gravid segment has uterus break into egg capsules and each contains up to 30 eggs. Veterinary Helminthology 150 Life cycle: ▪ Life cycle: Indirect (one intermediate hosts is required). ▪ Developmental stages: Gravid segments either creep out of the anus (active and motile) or pass with faeces. Egg capsules are ingested by larvae (has chewing mouthparts) of the dog flea Ctenocephalides canis, cat flea (C. felis) or human flea Pulex irritans or any stage (larval or adult) of dog louse (Trichodectus canis). The oncosphere hatch in the gut of the intermediate host, burrow through the wall, and develop into cercocystic cysticercoid in the hemocoele when the flea or louse mature. The final host is infected by ingestion of the flea or louse containing the cysticercoids which is liberated in the small intestine and developed into adult worm after 21 days. The children get this infection by accidental ingestion of infected flea or lice or free cysticercoids present on the coats or the lips of dog during playing with their pets. ▪ N.B: -This is an example of hyper parasitism since the flea is itself a parasite. ▪ Prepatent period: 3 weeks. ▪ Pathogenesis and clinical signs: ▪ In Dogs: The adult is non-pathogenic and several hundreds can be tolerated without clinical effect. They shed segments, which, as they crawl actively from the anus, may cause some discomfort, itching, and rubbing the anus along the floor or a ground. Such behaviour is associated with pruritus and impacted anal glands. ▪ In Man: Usually symptomless in mild infections but in heavy infections, abdominal pain with or without diarrhoea and restlessness may be presenting in a complain. Veterinary Helminthology 151 Diagnosis: ▪ By finding the characteristic gravid segments (elongate shape, and the double genital organs) either passing spontaneously from the anus (perineum, coat, floor or bed) or in the faeces single or in short chain. ▪ Egg capsules may be seen in stools contain 20-30 eggs or on testing gravid segments which are easily seen under the microscope. Treatment: ▪ Anti-taenial drugs like praziquantel, should be accompanied by the use of insecticides (Deltamethrin) as it is clearly of no value to eliminate the adult tapeworm while leaving a reservoir in the animal’s ectoparasites. Control: ▪ Avoid fondling with infected dogs and cats. ▪ Spraying pet dogs & cats and bedding materials with insecticides. ▪ Treatment of infected persons and pet dogs & cats. Veterinary Helminthology 152  Cestodes of poultry Family: Dilepididae Genus: Amoebotaenia Choanotaenia infundibulum Amoebotaenia cuneata A. cuneata D.H Fowl , turkey Fowl Habitat Small intestine Small intestine Genus: Choanotaenia I.H House fly and beetles Earth worm Cyst Cysticercoids The same C. infundibulum Length 20 cm 4 mm Scolex 4 sucker, retractable rostellum with 4 suckers with rostellum armed with single few large rose thorn hooks row of hooks Mature segment Single set of genital organs with Single set of genital organs with irregular regular alternate genital pores alternate genital pores Gross appearance Each segment is wider posteriorly Triangular appearance of the segment giving the margin of the tapeworm a ‘saw-edge’ appearance. Gravid Transverse sac like, leave the Transverse Sac and lobed segment segment before it is completely gravid and may contain egg capsules with single egg. Veterinary Helminthology 153  Cestodes of equines and ruminants Family: Anoplocephalidae Genus: Anoplocephala ▪ Essentially tapeworms of herbivores; horses (Anoplocephala, Paranoplocephala) and ruminants (Moniezia). A. perfoliata ▪ Scolex is large, globular, with four suckers and has neither rostellum nor hooks. A. magna ▪ Neck is absent with large strobila. ▪ Mature and gravid segments are wider than long. Genus: Paranoplocephala ▪ Testes are numerous and the uterus may persist or be replaced by egg-capsules, or eggs may pass into one or more par-uterine organs. P. mamillana ▪ Presence of either one or two sets of genital organs in each mature segment. ▪ The genital pores are marginal and alternate irregularly if one set of genital organs Genus: Moniezia is present. ▪ The eggs have three coverings: an outermost vitelline membrane; a middle M. expansa albuminous coat and an innermost chitinous membrane, which has a pair of hooked projections which support the oncosphere called pyriform apparatus. M. benedini ▪ The intermediate hosts are oribatid mites and the larval stage is a cysticercoid. M. trigonophora M. Denticulata (M. alba) M. pallida Veterinary Helminthology 154 Cestodes of equines Genus: Anoplocephala Genus: Paranoplocephala Character A. perfoliata A. magna P. mamillana D.H Horse and donkey Horse and donkey Horse Habitat Small and large intestine Small intestine Stomach and small intestine I.H Oribatid mites (soil and pasture) The same The same Metacestode Cysticercoid in the tissue of mites The same The same Length Adults are up to 4-8 x 1.2 cm Adults are up to 80 x 2.5 cm Adults are 10-50 × 4-6 mm in size (Short neck and segments widen (dwarf horse tapeworm) rapidly, Cigar shape) Scolex Rounded scolex, 2 mm with a lappet Larger 4-6 mm and wide without Narrow and large with slit opening in (tongue shape) behind each sucker lappet the suckers without lappet Mature segment Broader than long with single set of The same but the genital organs As A. perfoliata genitalia and genital pores are are single and the pores are alternate irregularly unilateral. Gravid segment Transverse large sac The same The same Eggs Irregularly spherical or triangular, Smaller in size (50-60 µm in irregularly spherical or triangular (51 with well developed pyriform diameter) × 37 μm in diameter) apparatus (65-80 µm in diameter) Veterinary Helminthology 155 Cestodes of equines Genus: Anoplocephala Genus: Paranoplocephala A. perfoliata A. magna P. mamillana Veterinary Helminthology 156 ▪ Life cycle: ▪ Life cycle: Indirect (one intermediate hosts is required). ▪ Developmental stages: Gravid segments or eggs are passed in the faeces of infected animals. These proglottids may be eaten by birds, which may disseminate the infection or eaten by oribatid mites in which the cysticercoids are formed in the body cavity. The infective cysticercoids are produced in approximately four months. Infection occurs by swallowing the infected intermediate host with herbages. In the small intestine of the final host, the cysticercoids attach themselves to the mucosa and develop to adults. ▪ Prepatent period: 1-2 months. ▪ Pathogenesis and clinical signs: ▪ They are less pathogenic and asymptomatic mostly in light infection but accompanied with severe condition even fatal in heavy infections. ▪ A. perfoliata are usually found around the ileo-caecal junction and cause ulceration of the mucosa at the site of attachment with formation of granulation tissue and oedema. Adults may obstruct the ileo-caecal junction; they may perforate the intestine leading to peritonitis and death. Clinically, unthriftiness, abdominal pain and diarrhoea. ▪ Heavy infections of A. magna may cause catarrhal, haemorrhagic or ulcerative enteritis and clinically, diarrhoea and colic. ▪ Paranoplocephala is usually considered to be relatively non-pathogenic. ▪ Diagnosis: By finding eggs or gravid segments in faeces and the adults in postmortem. ▪ Treatment: Pyrantel at 38 mg/kg and Praziquantel at 1 mg/kg are effective. Veterinary Helminthology 157 Cestodes of ruminants Genus: Moniezia Character M. expansa M. benedini M. trigonophora M. Denticulata M. pallida (M. alba) D.H Ruminant (small) Ruminant (Cattle) Ruminant (Camel) Ruminant (cattle) Equine Habitat Small intestine Small intestine Small intestine Small intestine Small intestine I.H Oribatid mites Oribatid mites Oribatid mites Oribatid mites Oribatid mites Metacestode Cysticercoid Cysticercoid Cysticercoid Cysticercoid Cysticercoid Length 6 meters x 1.5 cm 2 meters x 2.5 cm 60-120 cm 0.5-2.5 m 140 cm Scolex Small scolex with 4 prominent suckers without rostellum or hooks and narrow neck (broad neck in T. saginata) Mature segment Segments are broader than long, with two sets of genital organs and bilateral (marginal) genital pores. The ovary and vitelline glands form a ring (horse-shoe-shaped) on either sides median to the long. excretory canals Testes Diffuse throughout the Diffuse throughout the two lateral triangles (heaps or Diffuse throughout the Diffuse throughout the segment and central fields segment and central fields pyramids) leaving the central segment and central fields segment and central fields zone free. Uterus Medial to the Ex. canal Medial to the Ex. canal Medial to the Ex. canal Medial to the Ex. canal Lateral to the Ex. canal Interproglottidal glands Present in a row extend Confined to a short Interproglottidal glands are No Interproglottidal glands Interproglottidal glands are along the full breadth of continuous row or band situated in the middle of the diffuse, linear and posterior margin of the in the median field of the posterior margin of each indistinct at the posterior segment posterior margin segment similar to M. expansa border of each segment Gravid segment Transverse sac filled with eggs and may be reticular Eggs Triangular, measure 50-60 irregularly quadrangular Square to round Square to round Square to round (have well defined pyriform μm In diameter eggs, 55-75 μm in apparatus) diameter Veterinary Helminthology 158 Veterinary Helminthology 159 M. expansa M. trigonophora M. Denticulata (M. alba) M. benedini Veterinary Helminthology 160 ▪ Life cycle: ▪ Life cycle: Indirect (one intermediate hosts is required). ▪ Developmental stages: Gravid segments and eggs pass in the faeces on pasture. They are ingested by oribatid forage mites in which cysticercoids are formed in their body cavity in 1-4 months and infection of the final host is by ingestion of infected mites during grazing. In the small intestine of the final host cysticercoids attach themselves to the mucosa and develop into adult in 6 weeks. Its life span is 3 months. ▪ Prepatent period: 1.5 months. ▪ Pathogenesis and clinical signs: ▪ Moniezia spp. are common in lambs and calves. The affected young animals have a rough coat with loss of wool. ▪ Heavy infections are usually associated with weakness, anaemia, diarrhoea, oedema and retarded growth. ▪ The intestine obstructions with a solid mass of tapeworm's may be recorded and accompanied with nervous signs like convulsions. ▪ Diagnosis: By finding eggs or gravid segments in faeces (triangular, M. expansa; quadrangular, M. benedeni that contain the oncosphere. The eggs of M. benedeni are slightly larger than those of M. expansa) and the adults in postmortem. ▪ Treatment: Broad-spectrum benzimidazole compounds like albendazole 5 mg/kg Bwt. ▪ Control: Prophylactic and therapeutic deworming of animals, proper disposal of animal’s dung and control of mites in pastures by insecticides like malathion. Veterinary Helminthology 161  Cestodes of rabbits Family: Anoplocephalidae ▪ Final host: Domestic and wild rabbits. Genus: Cittotaenia ▪ Intermediate host: Oribatid mites (Forage). ▪ Metacestode: Cysticercoids. C. ctenoides ▪ Habitat: Small intestine. C. denticulata ▪ Geographical distribution: Europe, Asia, America. ▪ Morphology: C. pectinata ▪ Gross: Tapeworms of the genus Cittotaenia are up to 80 cm long and 1 cm wide. ▪ Microscopic: The scolex is about 0.5 mm wide with short neck (C. ctenoides), 0.8 mm in diameter without neck (C. denticulata) and 0.25 mm with long neck (C. pectinata). Proglottids are broader than long and each contains two sets of genital organs. Eggs are about 64 μm in diameter and have a pyriform apparatus. ▪ Life cycle: Mature proglottids or eggs are passed in the faeces and on to pasture where the oncospheres are ingested by forage mites. The embryos migrate into the body cavity of the mite where they develop to cysticercoids. Infection of the final host is by ingestion of infected mites during grazing. ▪ Pathogenesis: Heavy infections especially with C. ctenoides frequently cause digestive disturbances, emaciation and even death among affected rabbits. ▪ Diagnosis: based largely on the presence of mature proglottids in the faeces. Veterinary Helminthology 162  Cestodes of ruminants Family: Thysanosomidae Genus: Stilesia ▪ Closely related to the Anoplocephalidae, (Stilesia, Avitellina, Thysanosoma S. hepatica and Thysaniezia). ▪ The worms are medium-sized tape worms which inhibit the small intestine S. globipunctata of ruminants (found mainly in sheep and other ruminants ). ▪ Some of the family members are found in bile ducts of sheep and cattle S. vittata (Stilesia hepatica and Thysanosoma actinoides). Genus: Avitellina ▪ Their significant pathogenicity is produced in small intestine not the bile ducts and only in heavy infections. A. centripunctata ▪ These tape worms do not produce any acute form of disease but long-term persistence in the host causing significant morbidity. A. woodlandi ▪ The gravid uterus disappears and is replaced in function by paruterine Genus: Thysanosoma organs. ▪ Eggs have no pyriform apparatus with thick wall and found in groups of 10– T. actinoides 15. ▪ The intermediate hosts are oribatid mites and the larval stage is a Genus: Thysaniezia cysticercoid. T. ovilla Veterinary Helminthology 163  Cestodes of ruminants Family: Thysanosomidae Genus: Stilesia ▪ Final host: Ruminants especially in sheep (S. vittata in camels). S. hepatica ▪ Intermediate host: Oribatid mites. ▪ Metacestode: Cysticercoids. S. globipunctata ▪ Habitat: Small intestine (S. globipunctata and S. vittata) and bile ducts (S. hepatica; liver tapeworms). ▪ Geographical distribution: Southern Europe, Africa and Asia. S. vittata ▪ Morphology: ▪ Gross: The adult tapeworm measures around 30-60 cm x 2.5-3 mm. The neck is broad and the scolex has prominent suckers. Segments are short but more visible than Avitellina. ▪ Microscopic: The mature segments have single set of genital organs with irregular alternating genital pore. Uterus is long transverse and dumbbell-shaped (two rounded portion connected by transverse duct) in the middle of segment. The ovary at one side of the uterus and the testes (10-14) are found in 2 groups on each side and medial to excretory canal and may cover it. The vitelline glands are absent. Gravid segments with 2 thick wall par-uterine organs, each containing about 30 eggs. The eggs lack a pyriform apparatus. ▪ Life cycle: Similar to genus Moniezia. ▪ Pathogenesis: Generally considered to be of low pathogenicity and no apparent clinical signs. In infected livers there may be slight cirrhosis and the walls of the bile ducts are usually thickened. Intestinal inflammation may occur in severe infection with epithelial desquamation and nodules formation. Veterinary Helminthology 164 Mature segments of Stilesia Gravid segments of Stilesia Veterinary Helminthology 165  Cestodes of ruminants Family: Thysanosomidae Genus: Avitellina ▪ Final host: Ruminants, mainly in sheep (A. woodlandi in camels). A. centripunctata ▪ Intermediate host: Oribatid mites. ▪ Metacestode: Cysticercoids. A. woodlandi ▪ Habitat: Small intestine. ▪ Geographical distribution: Europe, Africa and Asia. ▪ Morphology: ▪ Gross: The adult tapeworm is around 3 meters x 3 mm, scolex is small with 4 oval suckers and no rostellum. It resembles Moniezia on gross inspection except that the segmentation is so poorly marked (ribbon-like appearance) and the posterior end is almost cylindrical in appearance. ▪ Microscopic: Proglottids are short, not distinctly segmented and have single set of genital organs with irregular alternating genital pore. Uterus lies transversely in the middle portion of the proglottid as median opaque line in posterior part of the segments. The ovary is spherical, situated toward the genital pore and the testes arranged in four groups in either sides, medial and lateral to excretory canal. The vitelline glands are absent (hence the name). Gravid segments have a single large thick-walled pear shaped par-uterine alternating from side to side in the segments and appear as n opaque white line in the medial portion of the proglottids. The eggs are large, thick shelled and lack a pyriform apparatus. ▪ Life cycle: Similar to genus Moniezia. ▪ Pathogenesis: Negligible pathogenesis. Veterinary Helminthology 166  Gravid segments of Avitellina Mature segments of Avitellina Veterinary Helminthology 167  Cestodes of ruminants Family: Thysanosomidae ▪ Common name: Fringed tapeworm. Genus: Thysanosoma ▪ Final host: Ruminants, mainly in sheep, cattle and deer. T. actinoides ▪ Intermediate host: Oribatid mites. ▪ Metacestode: Cysticercoids. ▪ Habitat: Small intestine, bile and pancreatic ducts. ▪ Geographical distribution: North and South America. ▪ Morphology: ▪ Gross: Adult tapeworms measure 15-30 cm x 8 mm. ▪ Microscopic: The scolex is up to 1.5 mm; segments are short and fringed posteriorly (Hence the name fringed tapeworm). Each segment contains two sets of genital organs with the testes lying medially. Uterus is a single undulating tube and the eggs then pass into several paruterine organs (each usually contains 6-12 eggs) which present in each proglottid and the eggs have no pyriform apparatus. ▪ Life cycle: Similar to genus Moniezia. ▪ Pathogenesis: Generally not considered pathogenic. Blockage of the bile or pancreatic ducts may occur resulting in digestive disorders and unthriftiness. Veterinary Helminthology 168  Cestodes of ruminants Family: Thysanosomidae ▪ Synonym: Thysaniezia giardia. Genus: Thysaniezia ▪ Final host: Cattle, sheep, goat, camel and wild ruminants. T. ovilla ▪ Intermediate host: Oribatid mites. ▪ Metacestode: Cysticercoids. ▪ Habitat: Small intestine. ▪ Geographical distribution: Southern Africa. ▪ Morphology: ▪ Gross: Adults reach 200 cm in length, varying in width up to 12 mm. ▪ Microscopic: The scolex is small, measuring up to 1 mm in diameter. Segments are short, bulge outwards (cirrus- sac) giving the margin of the worm an irregular appearance, and contain a single set of genital organs, rarely two, with genital pores alternating irregularly. The testes are lateral to the excretory canals. Eggs are devoid of a pyriform apparatus and found in groups of 10–15 in elongated paruterine organs, with a thick grey shell. ▪ Life cycle: Similar to genus Moniezia. ▪ Pathogenesis: Not considered pathogenic as the worm is rarely seen in number sufficiently large to produce clinical signs. Veterinary Helminthology 169