1

ORDER CYCLOHPYLLİDEA

Family Taeniidae : The adults are, in most case, large tapeworms and are found in carnivores (domestic and wild) and human in the small intestine. Genera of importance are Taenia and Echinococcus. The scolex has an armed rostellum with a concentric double rows of hooks ( the important exception is Taenia saginata whose scolex is unarmed). The gravid segments are longer than they are wide. The stages are a cysticercus, coenurus, hydatid cyst , tetrathyridium, cysticercoid and strobilocercus and these occurs in mammals, arthropods, amphibians and reptiles . The egg, as seen outside the host’s body, is small and spherical, and the embryophore consists of the typical double layer, outer vitelline and inner chitinous. In this family, the apperance of the embryophore in optical section is of radial striation. The outer shell is lost in the uterus of the tapeworm, and is not seen in diagnostic material, and its colour is brown.

Genus Taenia : The members of the genus Taenia are large tapeworms comprising a number of species. It has the essential morphological characters of the family, with a double row of hooks on the scolex, and single genital pore. In the proglottids, the genital pores open alternately on either side in successive proglottids, but not regularly so. Usually there are numerous testes. The ovary is in the hinder parts of the proglottids. The uterus has a median longitudinal stem with lateral brnches that may themselves be branched. Differentiation is usually based on the size of the scolex, the size of the rostellum and number of hooks, and on the morphology of the genital system within the mature segments. The larval stages themselves are very simply diagnosed morphologically becase of the wide range of forms, and biologically because of their high selectivity for particular intermediate hosts and tissues. The adults of Taenia are usually of minor importance in domestic , and it is the larval stages which are of veterinary interest. The basic life cycle of taeniidae: the gravid segments are passed in the faeces, singly or in short lengths, and the embryophores are broken down in the digestive organs ( stomach, abomasum or small intestine etc.) of the intermediate hosts. The free oncosphere migrates actively into the intestinal mucosa using its six hooks and reaches the bloodstream, in which it may be carried to any organ, tissue and cavity. It has highly selective tissue requirements, and only if it arrives in its predilection tissue will it develop. The (metacestode ) has usually reached its fully infective form in two or three months from ingestion, and final host ingests the predilection tissue containing it. Most of larval stages can survive until the death of the intermediate host for several days - years, an important factor in an epidemiological system where carrion-feeding carnivores exist.

Species : Taenia saginata

The adult tapeworms is usually 5-8 m long, rarely up to 15 m. The scolex has neither a rostellum nor hooks. Gravid segments are 16-20 mm long by 4-7 mm wide and the uterus has 15-35 lateral branches on either side. In cattle , the mature cysticercus, C. bovis, is greyish- white, oval, about 0.5-1.0 cm long and filled with fluid in which the invaginated scolex clearly visible. As in the adult tapeworm, it has neither rostellum nor hooks. 2

Prediction side : Small intestine ( T. saginata ; in definitive host ); muscle (Cysticercus bovis – metacestode stage - larva stage ; in intermediate host ) Final hosts : Human

Intermediate hosts : Cattle, although other ruminants can serve as intermediate hosts

Life cycle : In infected human pass millions of eggs daily, either free in the faeces or as intact segments each containing about 250.000 eggs, and these can survive on the pasture for several months. After ingestion by suitable bovine, the oncosphere travel via the blood to striated muscle. It is firsly grossly visible about 2 weeks later as a pale semi-transparent spot about 1.0 mm in diameter, but it is not infective to human until about 12 weeks when it has reach its full size around 1.0 cm. By then it is enclosed by in a thin fibrous capsule but despite this capsule the scolex can usually still be seen. The longevity of the cysts range from weeks to years. When they die they are usually replaced by a caseous crumbly mass, which may become calcified, and both living and dead cysts are frequently in the same carcass. Human become infected by ingesting raw or inadequately cooked meat. Development to patency takes 2-3 months.

Pathogenesis and clinical signs : Most people who become infected with T. saginata, which is usually a single tapeworm , remain asymptomatic. Some symptoms, such as diarrhea, abdominal-pain, change appetite, and slight weight loss, may be experienced by T. saginata. In addition, symptoms including dizziness, vomiting, and nausea may also develop in such patients. Laboratory tests often reveal the presence of a moderate oesinophilia. The prognosis is usually good.

Although C. bovis may occur anywhere in the striated muscles, the predilection sites, at least from viewpoint of routine meat inspection, are the heart, the tongue and masseter and intercostal muscles. Under natural conditions the presence of cysticerci in the muscle of cattle is not associated clinical signs although, sometimes in massive infections of C. bovis developed severe myocarditis and heart failure associated with developing cysticerci in the heart.

Diagnosis : In human, definitive diagnosis depends on identification of the proglottids passed by the patient. The eggs in the stool can be identified only Taenia spp. , because the eggs of all tapeworm in the genus of Taenia look alike.

In the intermediate hosts, individual countries have different regulations regarding the inspection of carcasses, but invariably the masseter muscle, tongue and heart are incised and examined and intercosatal muscles and diaghram inspected; triceps muscle is also incised in many counties. The inspection is inevitably a compromise between detection of cysticerci and preservation of the economic value of the carcass. Treatment : All yet there is no licensed drug available that will effectively destroy all the cysticerci in the muscle. In human, the drug of choice praziquantel effective in a single dose administration.

Control : As in most parasitic infections of the food animals contagious to man, the first point of attack is the prevention of private slaughter of the animals. In approved abattoirs inspection 3 of carcasses may be undertaken , and though countries vary in the intensity of examination, the essential features are similar. Cooking of the meat is never included in regulations and it should be recognised that, though the thermal death point of C. bovis is only 57°C , this temperature should be reached in the middle of a thick piece of meat. Regulations usually require that infected carcasses are frozen at – 10 °C for at least 10 days, which is sufficient to kill the cysticerci although the process reduces the economic value of the meat.

Species : Taenia solium The tapeworm is most prevalent in South and Central America, India, Africa and parts of Far East . It is now uncommon in many developed countries and Islamic countries.

The adult tapeworm is 3-5 m long, up to 8 m. The rostellum has four suckers and rostellum bears 22-23 hooks in two rows. Gravid segments are 10-12 mm long and 5-6mm wide. The ovary is in the posterior third of the proglooid and has two lobes with an accessory third lobe. The uterus has 7-12 lateral branches on either side. The name of the larval stage is Cysticercus cellulosa which have morphologically distinct types. The commenest is the ‘cellulosa’ cysticercus which has a fluid-fiiled bladder that is 0.5-1.5 cm in length with an invaginated scolex. The ‘racemose’ form has no evident scolex, but are larger and up to 20 cm in length.

Pedilection side : Small intestine ( T. solium- adult tapeworm, in final host); muscle ( Cysticercus cellulosa- larval stage , in intermediate hosts) Final hosts : Human

Intermediate hosts : Pig, wild boar, rarely dog and human

Life cycle : Gravid segment passed in the feaces, frequently in chains, each contain around 40,000 eggs and because they are non-motile they tend to be concentrated over a small area. After ingestion by susceptible pig the oncosphere travels via the blood to striated muscle. The principal location is the striated muscle, but cysticerci may also develop in other organs, such as lungs, liver, brain and kidney. Human become infected by ingesting raw or inadequately cooked pork containing viable cysticerci. The human, final host, may also act as an intermediated host and become infected with cysticerci . This is most likely to occur from accidental ingestion of T. solium eggs via unwashed hands or contaminated food. There is also, apparently , a minor route of autoinfectionin a person with an adult tapeworm, from the liberation of oncospheres after the digestion of a gravid segment that has entered the stomach from the duodenum by reverse peristaltics. The prepatent period is 2-3 months.

Pathogenesis and clinical signs : Cysticerci, comprising a single large cyst and inverted scolex, measure 1-2 cm and easily visible between muscle fibres. The cysticerci are rapidly ensheathed in connective tissue and create a crescentic zone of degenerative lysis around them, thereby allowing room to grow. Pigs are usually slaugtered at an age when all cysticerci are generally still viable.

Clinical signs are inapparent in pigs naturally infected with cysticerci and generally insignificant in humans with adult tapeworms. However, when humans are infected with cysticerci, various clinical signs may occur depending on the location of the cysts in the organs, muscle 4 or subcutaneous tissue. Cysticerci may be found in every organs of the body in humas but are most common in subcutaneous tissue, eye and brain. Larvae that reach the brain develop in the ventricles and frequently become racemose in character. Most seriously, cysticerci that develop in the CNS produce mental disturbances or clinical signs of epilepsy or increased intracranial pressure. They may also develop in the eye with consequent loss of vision.

Diagnosis : For all practical purpose, diagnosis in pigs depends on meat inspection procedures but this lack for low infection levels. Individual countries have different regulations regarding inspection of carcasses, but in variably the masseter muscle, tongue and heart are insiced and examined and the intercostal muscles and diaphragm inspected. In humans, proglottids can sometime be seen in faeces, and the diagnosis of cerebral depends primarily on the detection of cysticerci by computed tomography (CT) and on the finding of antibodies to csyticerci in the cerebrospinal fluid.

Treatment : No effective drugs are available to kill cysticerci in the muscle, although in human praziquantel and albendazole are considered to be some value as possible alternatives to surgery. In humans, the drug choice of praziquantel effective a single dose administration.

Control : This depends ultimately on the enforcement of meat inspection regulation and deep- freezing procedures. Freezing pork meat at - 10 ° C to - 18°C constinuosly for 4 days kills the cysticerci, but chilling the meat at 0°C is not sufficient and cysts may remain viable in chilled meat for 70 days. The exclusion of pigs from contact with human faeces, the through cooking of pork and proper standarts of person hygiene will reduce the prevalence of infection.

Taenia and Echinococcus species in domestic animals

Species Hosts Intermediate hosts Metacestodes stages

Name Sites

E. granulosus dog,fox,wolf,jackal,dingo livestock and human hydatid cyst liver,lung,etc.

E. equinus dog horse hydatid cyst liver, lung,etc.

E. orteleppi dog cattle hydatid cyst liver,lung,etc.

E.multilocularis fox,cat,dog rodents,human,pig,horse Alveolar cyst liver,lung,etc.

E.vogeli bush dog,dog rodents hydatid cyst peripherial,

(polycystic) liver,lung

E. oligarthrus wild felids rodents hydatid cyst peripherial

(polycystic) liver,lung

T. ovis dog,fox sheep,goat Cysticerc us ovis muscle

T. pisiformis dog,fox rabbit C.pisiformis abdominal

cavity,liver

T.hydatigena dog,fox livestock C.tenuicollis abdominal

cavity,liver 5

T. multiceps dog,fox livestock,human Coenurus cerebralis brain,

spinal cord

T. serialis dog rabbit Coenurus serialis connective

tissue

T.taeniaformis cat small rodents Strobiocercus liver

fasciolaris

T. crassiceps dog,fox small rodents C.longicollis abdominal cavity

Genus : Echinococcus

The genus Echinococcus is composed of several species that expolit predator-prey systems between carnivores (mainly canids) or felids as principal hosts and intermediated hosts that range from rodents to livestock depending on the species. Six species are currently recognised in the genus Echinococcus with a seventh, Echinococcus shiquicus, recently described. Considerable phenotypic and genetic variability has been observed within the species Echinococcus granulosus and several strains have been identified based on molecular genotyping. New data demostrate that Echinococcus granulosus is an assembly of several rather diverse starins abd genotypes (desiganed G1-G10) thatsShow fundamental differences, not only in their epidemiology but also in their pathogenicity to humans.

Species Hosts Intermediated hosts Site E. granulosus dog,fox,wild canids sheep,cattle,goat,deer liver,lungs

camel,pig,buffalo,man

E. multilocularis dog,cat,fox,wild canid rodents,pig liver E.equinus (G4) dog horse,donkey liver

E.orteleppi (G5) dog cattle liver

E.vogeli wild canids rodents liver

E.oligatrhus wild felids rodents liver Echinococcus equinus was formerly known as the horse strain (G4) of E. granulosus. Echinococcus orteleppi, the former cattle strain (G5), is adapted to transmission by cattle. Echinococcus oligarthus and E. vogeli exist in wildlife cycles anda re morphologically similar to E. multilocularis and cause polycyctic echinococcosis in humans. General morphology

An adult Echinococcus is only a few milimeters long (rarely more than 7 mm ) and usually has no more than six segments, and, like all tapeworms, Echinococcus has no gut and all metabolic intercharge takes place across the syncytial outer covering, the tegument. Anteriorly, the adult 6

Echinococcus possesses a specialised attachment organ, the scolex, which has four muscular suckers and two rows of hooks, one lerge an done small, on the rostellum. The body ,or strobila, is segmented and consists of a number of reproductive units (proglottids), which may vary in number from two to six. The adult tapeworm is hermaphrodite with reproductive ducts opening at a common, lateral, genital pore, the position of which may vary depending on species and strain. There is prominent cirrus sac, which may be horizantel or tilted anteriorly and the vitellarium is globular. The uterus dilates after fertilisation , eventually occupying most of the terminal segment when the eggs are fully developed.

The eggs are ovoid ( 30 -40 µm diameter ), consisting of a hexacant embryo ( oncosphore) surrounded by several envelopes the most noticeable one being the highly resistant keratinised embryophore, which gives the eggs a dark striated appearance. The outer capsule quickly disappears once the eggs are liberated from the host. The eggs of Echinococcus are morphologically indistiguishable to those of other tapeworms of the genus Taenia.

Metacestode (larval stage) basically consists of a bladder with an outer acellular laminated layer and an inner nucleated germinal layer, which may give rise by asexual to brood capcules. Protoscoleces arise from the inner wall of the brood capsules. The structure and development of the metacestode differs between the four species of Echinococcus.

General life-cycles Basic life-cycle pattern :

Echinococcus spp. require two mammalian hosts for completion of their life cycles. Segments contain eggs (gravid segments) or free eggs are passed in the faeces of the definitive host, a carnivore. The eggs are ingested by an intermediated host, in which the metacestode stage ( larval stage) and protosoleces develop. The cycle is completed if such an intermediated host in eaten by a suitable carnivore.

Eggs in the environment :

The eggs are highly resistance to environmental factors an d can remain infective for many months or up to about 1 year in a moist environment at lower of temparatures (about 4 °C to 15°C). Eggs of Echinococcus spp. are sensitive to desication. At a relative humidity of 25%, eggs of Echinococcus spp. were killed within 4 days and 0% within 1 day. Heating to 60°C - 80°C killed eggs of Echinococcus in less than 5 min. On the other hand, Echinococcus eggs can survive frezzing temparatures.

Intermediated and aberrant (= accidental) hosts :

The intermediate hosts, represented by a wide range of mammals, acquired the infection by the ingestion of eggs. Following the action of enzymes in the stomach and small intestine, the oncosphore is released from the keratinised embryophore. Bile assists in activating the oncosphere, which penetrates the wall of the small intestine. Penetration is then aided by the hooks movements, and possibly by secretions, of the oncosphere. Upon gaining access to a venule or lacteal, the oncosphere is passively transported to the liver, where some are 7 retained. Others reach the lungs, and a few may be transported further to the kidneys, spleen, mıscles, brain or other organs. All mammals ( including humans) in which metacestodes of Echinococcus species develop after infection with eggs, may be referred to as ‘ intermediated host ‘ . From the epidemiological point of view, it might be useful to differentiate between ‘intermediate host’, which play a role in the perpetuation of the life cycle, and ‘ aberrant host or accidental host’ which represent a ‘blind alley’ fort the parasites as the latter are not involved in disease transmission. With a few rare exceptions, humans belong to the group of ‘ accidental host’.

The metacestode stage :

Once the oncosphere has reached its final host, it develops into the metacestode stage. Time of develop is variable and it may take several months before protosoleces are produced ( fertile metacestode / fertile larval stage / fertile cycst ). There may be several thousand protosoleces within a single cyst of E . granulosus or an aggregation of vesicles of E. multilocularis. Each single protoscolex is capable of developing into a sexually mature adult tapeworm. Not all metacestodes produce protoscoleces ( sterile metacestode / sterile cyst ). When protosoleces are ingested by a suitable definitive host, following the action of pepsin in the stomach, they evaginated in the upper duodenum in response to a change in pH, exposure to bile and to increased temparature. They then develop to the sexually mature adult tapeworm, approximately four to eight weeks after infection, depending on the species and strain, and on the susceptibilty of the host.

Species : Echinococcus granulosus

Adult tapeworm varies between 3mm -7mm in length ( rarely up to 11 mm ) and usually possesses three or four segments ( rarely up to six) , terminal gravid one occupying about half the length of the complete tapeworm, and is therefore difficult to find in the freshly opened intestine. The scolex is typically taeniid and the rostellum has two rows of hooks, varying from in number from 30 to 60. Each segment has a single genital opening, with the penultimate segment sexually mature and the last segment gravid. The genital pores alternate irregularlly. There are 40 to 60 testes in the mature proglottid and the ovary is shaped like horse shoe or spleen, with the opening posterior. The gravid uterus possesses short lateral branches and contains 400 to 800 eggs. The gravid proglottids normally disintegrates in the alimentary tracts and only eggs are expelled in faeces.

The name of the metacestode stage of E. granulosus is hydatid cyst (= unilocular hydatid cyst ). Hydatid cysts are large fluid- fiiled vesicle, 5- 20 cm in diameter, with a thick concentrically laminated cuticle and an internal germinal layer. The germinal layer produces numerous small vesicles or brood capsules each containing up to 40 scolices, each of which is termed a protoscolex ( plural, protoscolices ), invaginated into their 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’ . The hydatid cyst or hydatid membrane is surrounded by, but usually is not attached to, an inflammatory connective tissue layer or capsule ( as known adventitial layer ). The space between the host and the hydatid cyst genarally contains a small volume of clear, colorless, or light-yellow liquid. Endogenous 8 daughter cysts may be found free in the fluid-filled cyst cavity or attached to the germinal epithelium. Exogenous daughter cyst are relatively unusual; they may be found in the pericystic space between the hydatid membrane and the host connective tissue capsule. Daughter cyst have a germinal layer and a laminated layer. Steril hydaids, so called, because they lack protoscolices, often cattle ans swine, making the diagnosis sometimes difficult and presumptive.

Predilection site : Small intestine Final Hosts : Echinococcus granulosus ; dog and many wild canids , E. equinus ; dog and red fox , E. orteleppi ; dog and lion

Intermediated hosts : E. granulosus ; domestic and wild ruminants, human and primates, pig, lagomorphs ; horses and donkeys are resistance. E. equinus ; horse,donkey, mule, ass . E. orteleppi ; cattle

Geographical distribution : E. granulosus worldwide; E. equinus , mainly Europe ; E. orteleppi mainly Africa

Life cycle : The prepatent period is in the final hosts is around 40-50 days, which only one gravis segment is shed per adult tapeworm in per week. After ingestion by the intermediate host, the oncosphere penetrates the gut wall and travels in the blood to the liver or lymph to the lungs. These are commonest sites for larval development , but occasionally oncosphere escape into general systemic cirrulation and develop in other organs and tissues ( brain, kidney, muscle, eyes, bone marrow ). Growth of the hydatid cyst is slow, mturity being reached in 6-12 months. In the liver end lungs the cyst may have a diameter of up 20 cm, but in the rarer sites, such as the abdominal cavity, where unrestricted growth is possible, it may be very large and contain several litres fluid. The cyst capsule consists of an outer membrane and an inner germinal membran ( or germinal epithelium) from which, when the cyst growth is almost complete , brood capsules each containing a number of scolices ( protoscolices )are budded off. Many of these brood capsules become detached and exist free in the hydatid fluid; collectively these and protoscolices are often referred to as “ hydatid sand”. Sometimes, complete daugther cysts are formed either inside the mother cyst or externally; in the later case they may be carried to other parts of the body to form new hydatids.

When protosoleces are ingested by a suitable definitive host, following the action of pepsin in the stomach, they evaginated in the upper duodenum in response to a change in pH, exposure to bile and to increased temparature. They then develop to the sexually mature adult tapeworm, approximately four to eight weeks after infection.

Infection of humans with Echinococcus granulosus may result from : a) handling infected definitive hosts, egg-containing faeces or egg-containing plants or soil follwed by direct hand to mouth transfer. The eggs of E. granulosus adhere to the coat of the dogs, particularly to the hairs around the anus , on the thighs, muzzles on the paws. b ) ingetion of vegetables, salads, fruits and other plants which have become contaminated directly with E. granulosus eggs. 9 c ) drinking of water contaminated with E. granulosus eggs by faeces of infected carnivores is a potential route of infection d ) Foodstuffs or surfaces may possibly be secondarily contaminated with Echinococcus eggs via agents such as wind, birds, beetles and flies.

Pathogenesis and clinical signs : The adult tapeworm is not pathogenic, and thousands may be present in the small intestine of a dog without clinical signs.

Infections with the hydatid cyst of Echinococcus granulosus occur in a broad specturum of natural intermediate host species, but also in animals which differ biologically from intermediate hosts in that they do not play a role in the transmission cycle ( = aberrant or accidental hosts ). Hydatid cysts grow slowly and usually take several years to develop to a size where they may cause disease and symptoms in animals. Fertile cysts may occur within about 2-4 years insheep ( but only 50 % of hydatid cysts are fertile by 6-6.5 years). Cysts are rarely fertile in cattle in most countries, except where the cattle strain is present.

Hydatid cysts in the intermediate hosts occur mostly in the liver and lungs, but they can also develop in other organs and tissue including the central nervous system, the skeletal muscle and marrow cavity of bones, kidney, pancreas, rarely in eyes. The cysts are vary greatly in size and shape ( typically unilocular but sometimes multilobed or multilocular) , and may be present in large numbers one or several organs.

It is well known that the infection of the intermediate hosts with cyst of E. granulosus may be asymptomatic during the whole life-span of the host. In the domectis animals the hydatid cyst in the liver and lungs is usually tolerated without any clinical signs, and the majority of infections are only revealed at the abottoir.

Hydatid cysts develop in various organ and tissues of the human body from oncosphore liberated from ingested eggs of E. granulosus, and hydatis cysts may establish in virtually all anatomic sites, but the liver and lungs are the most frequently affected organs. One or both lungs may be affected causing respiratory symptoms, and if several hydatid cysts are present in the liver there may be gross abdominal distension. If the cyst should rupture there is a risk of death from anaphylaxis; alternatively if the person survives, released daugther cysts may development in other regions of the body.

Diagnosis: Diagnosis of the infection with E. granulosus in definitive hosts is difficult, because the eggs of all Echinococcus and Taenia species are morphologically indistinguishable from one another, and the characteristic small segments of Echinococcus spp. ( E. granulosus and E. multilocularis ) may be absent from the faeces or can be easily overlooked. Two major diagnostic methods have been extensively used in dogs and other final hosts. These are purgation of arecoline hydrobromide or arecoline acetarsol and necropsy of the dogs. Recently, several new techiques are available fort he diagnosis of Echinococcus spp. in dogs and other final hosts.

Handling of material containing viable eggs of E. granulosus represents an infection risk for humans. In order to rduce or exclude an infection risk for laboratory personnel, the fecal samples and small intestines should be deep-frozen at -70°c to - 80°C for one week before 10 diagnosis. This procedure kills the eggs of E. granulosus and E. multilocularis. Strict safty precautions should be observed during the whole the diagnosing procedure.

Diagnosis of infection dogs with adult tapeworms is difficult, because the segments are small and are only shed sparsely. When found, identification is based on their size ( 2.0-3.0 mm), ovoid shape and single genital pore. If a necropsy is available the small intestine should be opened and immersed in shallow water, when the attached tapeworms will be seen as small slender papillae. Immundiagnostic tests have been developed based on the detection of faecal antigen by the antibody ELISA technique. In living dogs, PCR techniques have been used the diagnosis of E. granulosus infection.

The diagnosis of hytadit cysts in the intermediate hosts of E.granulosus is mainly on necropsy findings. Immunological tests fort he diagnosis of E. granulosus metacestodes in intermediated hosts are less sensitive ans specific.

The diagnosis of cystic echinococcosis in humans is mainly on clinical symptomps, confimation by imaging ( US, CT, X-ray, etc) and identificationof characteristic or suspicious cyst structures, confirmation by detection of spesific antibodies with ELISA.

Treatment: Echinococcus tapeworms are more difficult to remove than Taenia, but several drugs has been evaluated for efficacy against Echinococcus infection in definitive hosts.

The current first choice of drug is praziquantel. The recommended dose of praziquantel for dogs and cats is 5.0 mg / kg bw for oral treatment and 5.7 mg /kg bw for intramuscular administration. Praziquantel is available as tablets to be administered orally, and an injectable solution for intramuscular administration ( subcutaneous injection is less effective against Echinococcus ). Although the efficacy of praziquantel is highly reliable in almost all cases, the possibility of low residual tapeworm burdens in some of the treated animals can not be exclude, notably if mistakes of drug administration occur. Praziquantel is safe (safety index in dogs > 36 ) to use in pregnant animals, dogs tolerated high dose for extended periods without organ damage or disturbance to the reproductive processes.

Epsiprantel, a more recently developed drug, is avaibale as coated tablet for oral administration to dogs at 5.5 mg/kg bw and cats at 2.75 mg / kg bw. Epsiprantel is well tolerated by dogs and cats.

Various other drugs, such as nitroscanate and various benzimidazole compounds, are partially effective against E. granulosus, but they do not reach efficacy level of praziquantel or epsiprantel.

Since a low residual worm burden may persist after a single treatment repeated treatmnet is recommended. The second treatment dose of the drug should ve applied within 1-7 days after the first treatment, but practical reasons treatment may be carried out on two subsequently days.

After treatment it is advisable to confined dogs for 48 hours to facilitate the collection and disposal of infected faeces. 11

The treatment of the intermediate hosts is not economical and no treatment in the sheep, cattle, goat and other intermediated hosts. In humans, hydatid cysts may be excised surgically, although mebendazole, albendazole and praziquantel therapies have been reported to be effective. Control: This is based on the regular treatment of dogs to eliminate the adult tapeworms and on the prevention of infection in dogs by exclusion from their diet of animal material containing hydatidosis. This is achieved by denying dogs Access to abattoirs and, where possible, by proper disposal of sheep carcasses on farms. For control programmes, a single treaetment is usually recommended at intervals of six weeks for E. granulosus, since the prepatent periods of this species normally exceed 42 - 45 days. There is, however, evidence that these intervals can be exceeded in control programmes as re-infection intervals may be longer than the prepatent periods.

Epidemiology: It is customary to consider the epidemiology as being based on two cycles, pastoral and sylvatic. In the pastoral cycle the dog is always involved, being infected by the feding of ruminants offall containing hydatit cysts. The domestic intermediate host will vary according to the local husbandry but the most important is the sheep, which appears to be the natural intermediated host, scolices from these animals being the most highly infective for dogs. The pastoral cycle is the primary source of hydatidosis in humans, infection being by accidental ingestion of eggs from the coats of dogs, or from vegetables and other foodstuffs contaminated by the dog faeces. The sylvatic cycle occurs in wild canids and ruminants and is based on predation or carrion feeding. It is less important as asource of human infection, except in hunting communities where the infection may be introduced to domestic dogs by the feeding of viscera of wild ruminants.

The dogs have played various roles in the villages, as guard-dogs and sheep-dogs. The village area, and particularly within about 200 meters around dog owners’ house, may be the place for probable higher contact between dog faeces and human population, and thus increased the risk of exposure to the parasite. Hygienic conditions and behaviours that induce direct contact with the dogs such as feding it, playing with it, and allowing with it to stay inside the house, or direct contact with faeces have seem found to be risk facrors. Sheep-dogs are principally responsible for pasture contamination (mountain pasture), and livestock animals (mainly sheep) become infected through the ingestion of the eggs in the grazing season.

Dogs’ feding habits are important. Dogs have been observed feeding with uncooked viscera and whole carcass on several occasions. Home slaughtering ( also festival sacrifices) is still practiced, and it is probably an important source for dog infection. Species : Echinococcus multilocularis

Echinococcus multilocularis is one of five species of hydatid cyst-forming tapeworms ( genus: Echinococcus) that occur as adults in the small intestineof carnivores ( principally canids). All five species of Echinococcus are potentially zoonotic, but E. multilocularis is the most pathogenic. Echinococcus multilocularis occurs across the northen hemisphere mainly in upland ecosystems or in the holartic zone. But, new cases occur annually in western and central Europe, the Near East, eastern Russia, northwest Chinia and northern Japan. 12

Echinococcus multilocularis is a very small tapeworm ((1.2-4.5 mm) and is generally similar to E. granulosus , but usually with four to five segments, the terminal one measuring less than half the length of the whole tapeworm. The scolex has four suckers and possesses a double row of large and small hooks ( about 14-34 ). The third segment of the adult worm is sexually mature and the genital pore are in front of the middle of each segment. The uterus is sac- like with no lateral sacculations in the terminal segment. The gravid segment contain around 200- 300 eggs. Eggs that are shed have a diameter of about 30-40µm and possess asmoothe thick shell.

The metacestode of E. multilocularis is a complex structure and develops quite differently to that of E. granulosus. The name of metacestode stage of E. multilocularis is alveolar cyst (= multilocular cyst ) . It is a multilocular, infiltrating structure consisting of numerous small vesicles embedded in a more or less dense stroma of connective tissue. This metacestode has a thin acellular laminated layer and a nucleated germinal layer, but not found a inflammatory connective tissue layer or adventitial layer which is formed by intermediated hosts. The structure of the metacestode consists of a germinative gelatinous matrix forming a cyctic structure with internal brood capsules and protoscolices. Proliferation occurs endogenously and exogenously and is attributable to the cells of the germinal layer. The metacestode consists of a network of filamentous solid cellular protrusions of the germinal layer which are responsible for infiltrating growth transforming into tube-like and cystic structure. Furthermore, the detacment of germinal cells from infiltrating cellular protrusions and their subsequent distribution via the lymph and blood can give rise to the distant metatas tic foci characteristic of E. multilocularis.

Predilection site : Lower small intestine

Definitive hosts : Fox, dog, coyote, wolf, raccoon dog and cat, althougth the cat is a less suitable host than dog.

Intermediated hosts : Mainly rodents, some of the large mammals, including human, are also susceptible.

Life cycle : Eggs of E. multilocularis , passing out of definitive hosts in faeces, are ingested by the intermediated hosts, and then the oncospheres penetrated the intestinal wall and are carried by the portal circulation to the liver where it rapidly vesiculates. In contrast to E. granulosus, in which growth is slow and variable, E. multilocularis develops rapidly in its natural intermediated hosts, producing protoscoleces in only 2-4 months.

The definitive hosts becomes infected when it ingests an intermediated host or its viscera that harbor alveolar hydatid csyt with protoscolices. The prepatent period is about 5 weeks, and adult tapeworms are relatively short-lived, about 6 months.

Humans are an aberrant host fort he metacestode of E. multilocularis. Human cases of multilocular hydatid disease may result when fruits and vegetables contaminated by the faeces of infected canine, and water contaminated by egg-containing feaces are consumed.

Pathogenesis and clinical signs : The larval metacestode stage develops primarily in the liver as the so-called multilocularis or alveolar cyst , a diffuse growth with many compartments 13 containing a gelatinous matrix into which the protoscolices are budded off. Growth in the intermediate host is invasive, extending locally and capable of systemic metastases to other sides such as lungs, brain, muscle and lymph nodes. These hydatids are the causative agent of alveococcosis and alveolar echinococcosis. The adult tapeworm cause little damage in the intestine of the final hosts. In the liver invasion by the metacestode stage can result in atrophy of the parenchyma cause cirrhosis.

Adults tapeworms are usually asymptomatic in the definitive hosts. In the intermediated hosts, cilinical signs are dependent on the level of infection and the location of the cysts. Infection in the human presents with few signs until the infection has markedly progressed. The slow infiltration of organs may cause symptoms resembling those of a slow-growing carcinoma.

Alveolar echinococcosis in dogs and cats is an extremely rare diagnois in endemic areas. It generaly is thought that a dog can become infected with the metacestode stage of E. multilocularis via two routes. The first is though ingestion of large numbers of infected eggs.

The second way is a consequence of infection with adult parasites that release eggs inthe dog’s intestine; the eggs hatch in the intestine, invade the intestine wall andd proceed to develop. Thus, dogs can be infected simultaneously with both adult and metacestode stage of E. multilocularis. These larvae can cause depression, ascites, progressing abdominal enlargement , anorexia / weigth loss, intermittent diarrhoea, nausea and, occasionally, death in dogs. It is important that veterinary practitioners recognize that dogs can act as intermediate and difinitive hosts for E. multilocularis, and that dogs with intestinal infectiond pose a serious zoonotic threat.

Epidemiology : Though E. multilocularis has a wide distribution in the northen hemisphere, it is essentially a parasite of tundra regions with its greatest prevalence in the sub-arctic regions of Canada, Alaska and Russia. Its basic epidemiological cycle in these regions in the arctic fox and wolf, and their prey, small rodents. Over last decade the population of red foxes expanded in Europe and foxes have also extended their distribution into urban and peri-urban areas. Eating vegetables or fruits contaminated by infected foxes and dogs seeking garden voles may occasionally infect suburban humans.

Diagnosis : The necropsy is the well-established method for the detection of intestinal E. multilocularis in the definitive hosts. More recent research techniques include th edetection of copro-DNA by PCR and detection of E. multilocularis specific coproantigen in an ELISA- baseed assay. Serological and PCR-based tests are available for the detection of infection in human.

Treatment : Dogs and cats can be treatment with praziquantel or epsiprantel. A single oral administration of praziquantel (5.0 mg/kg bw) is 100 % effective against E. multilocularis in the definitive hosts. The spot-on preparate of praziquantel (4 % w/v ) applied dermally at 8 mg/kg is highly effective in removing E. multilocularis from the small intestine of cats infected with immature and mature (in prepatent time ) infection of E. multilocularis. 14

Epsiprantel, a more recently developed drug, is avaibale as coated tablet for oral administration to dogs at 5.5 mg/kg bw and cats at 2.75 mg / kg bw. Epsiprantel is well tolerated by dogs and cats. Control : Precautionary neasures include:

● the wearing of protective rubber gloves whe handling fresh skins/ furs of foxes, wolves

● thorough washing of forest fruits and berries pror to consumption in regions where infection is endemic

● treatment of dogs and cats with effective cestodial anthelmintic