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SGU Parasitology

DH – Canids and wild carnivores – the most common taeniid tapeworm of dogs in US. T. pisiformis
IH - rabbits and hares - Cysticercus pisiformis (pea-like) – found in the liver and peritoneal cavity. T. pisiformis
DH – Canids and wild carnivores. The adult = 2.0 m long T. ovis
IH – sheep - Cysticercus ovis infects the cardiac and skeletal muscles and represents the most important pathological lesion found by US inspectors in imported Australian mutton T. ovis
DH – Canids and wild carnivores. The adult – large tapeworm (up to 5.0 m) T. hydatigena
IH - cattle, sheep, swine, and certain wild ungulates - Cysticercus tenuicolis (long, attenuated neck) T. hydatigena
(8.0 cm diameter) migrates through the liver tissue and encysts on the peritoneal membranes of IH. Cysticercus tenuicolis
Prevalent in sheep, but only detected at meat inspection Cysticercus tenuicolis
sometimes large numbers of developing cysticerci migrate in the liver of sheep or pig producing hepatitis cysticercosa
a condition resembling acute fasciolosis pathology, often fatal. hepatitis cysticercosa
Even small numbers of migrating larvae are capable of inducing “black disease” in the presence of C. novyi. Cysticercus tenuicolis
the subcapsular surface of the liver is studded with greenish nodules of around 1 cm in diameter. Cysticercus tenuicolis
Control: based only on excluding dogs and other canids from sheep pastures, but this is next to impossible; praziquantel (dog). Cysticercus tenuicolis
Cysticercus tenuicolis T. hydatigena
DH – cat. The adult = 60 cm long; treatment: Profender®; praziquantel T. taeniaeformis
IH - mice and other rodents - Cysticercus fasciolaris – strobilocerci found within pea-sized nodules partially embedded in the liver parenchyma T. taeniaeformis
DH – domestic dog and wild canids. The adult = 10.0 m long. T. multiceps
ID - sheep, goats, and sometimes cattle - Coenurus cerebralis in the cranial cavity T. multiceps
mature cyst is a large fluid-filled cyst (~ 5.0 cm or more in diameter), bearing clusters of scolices on its internal wall. Coenurus cerebralis
As the cyst grows over a period of 6 or 8 months, neurological signs of progressive space occupation slowly develop Coenurus cerebralis
There may be: blindness, incoordination, walking in circles, peculiarities in gait, hyperaesthesia or paraplegia and pressing the head against the walls, tree trunks, etc Coenurus cerebralis
If the cyst is located superficially – local softening of the skull; death The clinical syndrome – True Gid
Differential diagnostic with: bacterial encephalitis (listeriosis) and parelaphostrongylosis The clinical syndrome – True Gid
Control – similar with the one for T. hydatigena T. multiceps
DH: humans. Adult tapeworms = 5-15m in length. The scolex has no rostellum or hooks Taenia saginata
The uterus of gravid segment has 15-30 lateral branches on each side of the central stem Taenia saginata
IH: cattle - Cysticercus bovis Taenia saginata
encysts in the striated muscles of heart, tongue, masseter and intercostal muscles bovine cysticercosis
infected humans pass millions of eggs daily, either free in the feces or as intact segments each containing 250,000 eggs Taenia saginata
In the pasture the eggs can survive for several months. Taenia saginata
The bovine get infected by ingesting the oncospheres which travels via the blood to striated muscles Taenia saginata
Humans become infected by ingesting raw or inadequately cooked meat. PPP = 2-3 month Taenia saginata
adult tapeworm may induce diarrhea and hunger pains, but the infection is usually asymptomatic. Taenia saginata
Public Health Concern Cysticercus bovis
is first visible in about 2 weeks after ingestion of the oncospheres, as a pale, semi-transparent spot, of about 1.0 mm diameter Cysticercus bovis
It is only infective to humans after 12 weeks, when it reaches its full size of 1.0 cm, usually enclosed (by the host) in a thin fibrous capsule. Cysticercus bovis
unarmed scolex, lacking the typical hooks of other taeniids is visible Cysticercus bovis
grayish white. Its longevity ranges from weeks to years The cysticercus
The dead ones are usually replaced by a caseous, crumbly mass which may become calcified The cysticercus
the masseter muscle, tongue and heart are examined and the intercostal muscles and diaphragm are inspected Cysticercus bovis
is not a common parasite in US Taenia saginata
DH – humans. The adult tapeworm is similar to T. saginata although the scolex has a rostellum armed with 2 rows of hooks T. solium
Uterus of the gravid segment has only 7-12 lateral branches T. solium
IH – pigs and humans - Cysticercus cellulosae T. solium
Clinical signs insignificant in humans with the adult tapeworms T. solium
Cysticercosis with Cysticercus cellulosae Public health hazard
Humans may become infected with cysticerci after ingestion of eggs on vegetables, other foods contaminated with human feces, handled by infected person, or due to lapse in personal hygiene (autoinfection). Cysticercosis with Cysticercus cellulosae
When the eggs reach the stomach, the oncospheres hatch out, enter the gut wall and wander far and wide in the body, slowly developing into cysticerci Cysticercosis with Cysticercus cellulosae
pigs – inapparent. T. solium
humas - the signs depend on the localization of the cysticerci, usually in the eye (loss of vision), or CNS (neurocysticercosis: mental disturbances, clinical signs of epilepsy or intracranial hypertension may occur) T. solium
2 species of veterinary importance Echinococcus granulosus and E. multilocularis
Unilocular hydatid disease E. granulosus
DH: dogs, wolves, coyotes. Adults located in the small intestine E. granulosus
IH: domestic ruminants, man, pig and wild ruminants E. granulosus
Hydatid cysts – mainly in the liver and lungs. E. granulosus
2 life cycles: pastoral and sylvatic E. granulosus
DH (dog & wild canids); IH – sheep (the natural IH), camel (Middle East), reindeer (Northern Europe). pastoral cycle:
DH- wild canids, ID – wild ruminants. Based on predation or carrion feeding. sylvatic cycle:
most common in Europe. The strain is highly specific for the horse and the eggs do not develop in the sheep E.g. equinus
DH: dog and the red fox. E.g. equinus
IH: horse and donkey E.g. equinus
one of the smallest cestodes of domestic animals (2-8 mm long) E. granulosus
adults have only 4-5 segments E. granulosus
terminal segment is gravid, occupying about half the length of the complete tapeworm E. granulosus
45-65 testes are generally distributed E. granulosus
the genital pore is located at or the posterior the middle of the segment. E. granulosus
oncosheres – very resistant on the ground (may be viable for ~ 2 years) E. granulosus
PPP (DH) – 40-50 days, after which only one gravid segment is shed per week E. granulosus
the adult tapeworm– non-pathogenic (thousands may be present in a dog without clinical signs) E. granulosus
adult worms – very difficult because the segments are small and only sparsely shed E. granulosus
When found – identified by their size (2-3 mm), ovoid shape and single genital pore; eggs resemble Taenia spp eggs E. granulosus
do not infiltrate, in contrast to alveolar hydatid cysts. unilocular hydatid cysts
grows very slowly and infrequently exceeds more than a few centimeters in diameter in slaughtered sheep and cattle. Unilocular hydatid cyst of E.granulosus
The hydatid membrane is surrounded by an inflammatory connective tissue capsule. Brood capsules, each containing many scolices, develop from the germinal epithelium lining the laminated hydatid membrane
Brood capsules, each containing many scolices, develop from the germinal epithelium lining the laminated hydatid membrane. Some of these rupture, releasing scolices to form sediment of so-called hydatid sand
lack brood capsules, scolices and daughter cysts; their identification in cattle and swine is necessarily somewhat presumptive Sterile hydatids
essentially a parasite of tundra regions, with its greatest prevalence in the subarctic regions of Canada, Alaska and former U.S.S.R E.multilocularis
Adult tapeworm – similar to E. granulosus, but with 4-5 segments and 17-26 testes are found posterior to the genital pore E.multilocularis
Alveolar hydatid cyst E.multilocularis
characterized by a diffuse growth with many compartments containing a gelatinous matrix into which the scolices are budded off. Alveolar hydatid cyst
Exogenous budding is not contained within the reactive connective tissue capsule but continuously proliferates and infiltrates surrounding tissues like a malignant neoplasm Alveolar hydatid cyst
DH: wild canids, domestic dog and cat E.multilocularis
Sled-dogs, domestic dogs and cats – potential carriers of infection for humans. Adults – in the intestine E.multilocularis
IH: mainly microtine rodents (voles and lemmings) E.multilocularis
Some of the larger mammals, including humans are also susceptible E.multilocularis
develop in voles, lemmings, cattle, horses, swine and humans, mainly in the liver Alveolar hydatid cysts of E. multilocularis
DH: asymptomatic E.multilocularis
H: alveolar hydatid infection proves invariably fatal in a few years E.multilocularis
Tapeworm of dogs, cats (and birds) Family: Dipylidiidae
Scolex with 4 suckers and an retractile rostellum armed with several rows of thornlike hooks Family: Dipylidiidae
The intermediate stage: cysticercoid Family: Dipylidiidae
the most common tapeworm of the domestic dog and cat, with a worldwide distribution Dipylidium caninum
much shorter than Taenia spp. (up to 50 cm long) Dipylidium caninum
segments are cucumber seed-like and have 2 sets of genital organs and bilateral genital pores Dipylidium caninum
genital apparatus lie slightly behind the middle of the segment, and each egg capsule may contain from 5 to 30 eggs Dipylidium caninum
eggs are clustered in packets (formed by outpocketing of the uterine wall) Dipylidium caninum
DH: dog, cat; rarely humans (usually children). Adults in small intestine. Dipylidium caninum
IH: fleas (Ctenocephalides canis, C. felis and Pulex irritans) and lice (Trichodectes canis), containing cysticercoids Dipylidium caninum
newly passed segments are active and can crawl about on the tail region of the animal. Dipylidium caninum
Dog or cat acquires this tapeworm while ingesting infected insects (e.g., fleas & lice) Dipylidium caninum
PPP = 2-3 weeks Dipylidium caninum
non-pathogenic, but the crawling segments may cause some discomfort (pruritus ani), and a useful sign of infections excessive grooming of the perineum. Rubbing the anus along the floor Dipylidium caninum
presence of a segment(s) on the coat around the perineum or in the pet’s environment Dipylidium caninum
anthelmintics (nitroscanate, niclosamide bunamidine and praziquantel) should be accompanied by the use of insecticides on the animal, bedding and resting places, to eliminate the immature stages of the fleas Dipylidium caninum
multiply asexually in the intestine of dogs and if not totally eliminated by anthelmintics, will repopulate the intestine even without further exposure (tetrathyridium). Mesocestoides corti
Adults - up to 40 cm in length Mesocestoides corti
scolex has 4 suckers but no hooks (or rostellum) Mesocestoides corti
mature segments have a mediodorsal genital pore Mesocestoides corti
eggs accumulate in a thick-walled parauterine organ as the segments mature Mesocestoides corti
gravid segments detach from the strobila and carry their relatively small burden of oncospheres to the exterior Mesocestoides corti
DH: dogs, cats and wild carnivores. Adults found in the small intestine. Mesocestoides corti
IH: (requires 2) Mesocestoides corti
1st: insects or mites, bearing the cysticercoids Mesocestoides corti
2nd: mammals and reptiles, bearing the tetrathyridia in their peritoneal cavity, or birds, bearing the tetrathyridia in their lungs. Mesocestoides corti
Dogs and cats get infected by predation of snakes, birds and small mammals. Mesocestoides corti
PPP=2 weeks Mesocestoides corti
Scolex without rostellum or hooks; lappets present Anoplocephala
Gravid segments are wide Anoplocephala
DH: horses Anoplocephala
IH: Soil (orbatid) mites. The larval stage is a cysticercoid (a small and solid cysticercus with an inverted scolex) Anoplocephala
Grazing animals get infected by the incidental ingestion of these infected arthropods Anoplocephala
specific treatment for adult tapeworms – Praziquantel Anoplocephala
Control – difficult since the forage mites are widespread on pasture. Administer the anthelmintic treatment before the grazing period Anoplocephala
the most common species in horses of all ages, but clinical signs are mainly reported in the animals up to 3-4 years of age Anoplocephala perfoliata
the lowest prevalence in the spring and highest in the winter Anoplocephala perfoliata
large white tapeworm up to 20 cm in length, with a rounded scolex having a lappet behind each of the 4 suckers. Very short neck. Strobila widens rapidly. Anoplocephala perfoliata
eggs – irregularly spherical or triangular, with a diameter of 50-80 um ; the oncosphere is supported by a pair of projections (pyriform apparatus) Anoplocephala perfoliata
DH: horses and donkeys. Adults found in the small and large intestine Anoplocephala perfoliata
IH: various forage mites in the soil and pasture Anoplocephala perfoliata
Mature segments are passed in the feces and disintegrate, releasing the eggs. The forage mites ingest the eggs which develop into the cysticercoid in 2-4 month. The DHs get infected by ingestion of the infected mites Anoplocephala perfoliata
The adult tapeworm develops in the intestine of horses in about 1-2 month Anoplocephala perfoliata
considered to be relatively non-pathogenic, but heavy infection may cause severe clinical signs, and may even be fatal Anoplocephala perfoliata
Found mainly in the cecum, but also tends to cluster in the ileum near the ileocecal valve, where it is associated with ulceration and reactive inflammation of the ileal wall, ileocecal colic in horses. These pathological changes probably account for some Anoplocephala perfoliata
Intestinal obstruction and perforation of the intestinal wall are fatal Anoplocephala perfoliata
Diagnostic– based on clinical signs (colic); serological ELISA (IgG); Multiplex fecal PCR Anoplocephala perfoliata
eggs and segments frequently cannot be demonstrated, either by flotation or sedimentation techniques, in the feces of horses known to be heavily infected with the parasite Anoplocephala perfoliata
common in ruminants; eggs resemble Anoplocephala (pyriform apparatus) Monezia
DH: ruminants. Infection affects mainly lambs, kids and calves during their first year of life. Monezia
More prevalent during the summer associated with the active periods of the forage mite vectors. Monezia
Adult worms found in the small intestine Monezia
long tapeworms (> 2m) Monezia
unarmed scolices with four large suckers Monezia
very wide segments containing 2 sets of genital organs visible along the lateral margins of segments with bilateral genitalia Monezia
interproglottidal glands at the posterior margins of each segment extend the full width of M.expansa but occupy only the midzone of the M. benedeni segment. Monezia
squared eggs, with the pyriform apparatus Monezia
IH: forage (orbatid) mites. The cysticercoids may overwinter in the mites. Monezia
Diagnosis – based on the presence of mature proglottids in the feces and eggs with characteristic pyriform apparatus. Monezia
Mature segments are broader than long. Family: Diphyllobothriidae
The genital organs are concentrated at the centers of the segments. Family: Diphyllobothriidae
The uterus consists of a spiral tube with four to eight loops on each side and opens to the outside through a midventral uterine pore behind the genital pore. Family: Diphyllobothriidae
Operculated eggs are discharged through the uterine pore. Family: Diphyllobothriidae
Tapeworms of dogs, cats and wild carnivores in North and South America, Australia and the Far East Spirometra
DH: natural definitive host is probably the bobcat Lynx rufus. Other definitive hosts: domestic cats, and dogs and the raccoon. S. mansonoides
1st IH = copepods (Cyclops) containing procercoids S. mansonoides
2nd IH = any class of vertebrates except fishes (bearing the pleurocercoids = spargana); even kittens fed procercoids support development of pleurocercoids, which appear in the flat muscles of the body wall and subcutaneous fascia. The natural IH is prob S. mansonoides
Treatment and Control: praziquantel (dogs and cats); prevent pets from predating infected intermediate hosts. S. mansonoides
Important tapeworm of the small intestine of humans in northern climates (Scandinavia, former USSR and North America) acquired by eating uncooked predatory freshwater fish. Diphyllobothrium latum
Very long tapeworm (broadfish tapeworm); up to 20 m in length Diphyllobothrium latum
Unarmed scolex with 2 bothria Diphyllobothrium latum
Mature and gravid segments are square-shaped with a central genital pore Diphyllobothrium latum
Eggs resemble F. hepatica eggs (yellow and operculate, but smaller). Diphyllobothrium latum
DH: humans and fish-eating mammals (dog, cat, pig, polar bear, mongoose, walrus, seals, sea lions, bears, foxes and mink) Diphyllobothrium latum
IH: 1st = an aquatic copepod crustacean (Cyclops) – procercoid Diphyllobothrium latum
2nd = a freshwater fish. The pleurocercoid (5 mm long, already has the scolex) is able to parasitize a series of predatory paratenic hosts until a suitable DH is found. PPP = 4-6 weeks Diphyllobothrium latum
The tapeworm causes a macrocytic, hypochromic (megaloblastic) anemia, due to its uptake of vitamin B12 from the intestine. Diphyllobothrium latum
Diagnosis: Detection of the characteristic eggs in the feces; clinical signs of anemia Diphyllobothrium latum
In areas where infection is common, domestic animals should be fed only thoroughly cooked or deep-frozen fish products Diphyllobothrium latum
are obligate endoparasites of vertebrates with an indirect life cycle (Phylum: Platyhelminthes) (Class: Cestoda)
Adults are GI parasites and the metacestodes (or larval) stages are extra-intestinally located in the intermediate hosts (Phylum: Platyhelminthes) (Class: Cestoda)
The adults are dorsoventrally flattened, segmented with variable length (4mm to > 10 m). (Phylum: Platyhelminthes) (Class: Cestoda)
No alimentary canal – all nutrients are absorbed through the integument (Phylum: Platyhelminthes) (Class: Cestoda)
body divided in 3 parts: scolex, neck and strobila (Phylum: Platyhelminthes) (Class: Cestoda)
the anterior part, holding the attachment organs to the host; 4 suckers with or without a rostellum (Cyclophyllidea) or 2 bothria = longitudinal grooves which become flattened to form organs of attachment (Pseudophyllidea) scolex
the body part of undifferentiated tissue where the segments start to develop neck
a chain of independent, progressively maturing reproductive units (proglottids). Each mature segment is hermaphroditic containing one or two sets of male and female reproductive organs. Gravid segments are full of eggs (onchospheres) strobila
When an infective tapeworm metacestode (larva) first arrives in the intestine of definitive host (DH), most of its body is digested away, leaving only the scolex and the neck. The scolex attaches to the intestinal wall, and the neck begins to bud off segm life cycle 1
These segments remain attached to one another to form the strobila. The reproductive organs (both female and male) gradually begin to mature, eggs and sperm are formed and fertilization occurs. Only the gravid proglottids are eliminated throughout the fec life cycle 2
Created by: alljacks



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