Veterinary Parasitology: Taenia and Echinococcus PDF

# Veterinary Parasitology ## Cestodes (TAPEWORMS) ### Genus: _Taenia_ spp. ### Genus: _Echinococcus_ spp. **Dr. Rana Magdy Elseadawy** | Definitive host/Site | Taenia species | Length of adult (m) | Distribution | Intermediate host | Larval stage | Larva site in I.H | Larva morphology | |:---|:-...

# Veterinary Parasitology ## Cestodes (TAPEWORMS) ### Genus: _Taenia_ spp. ### Genus: _Echinococcus_ spp. **Dr. Rana Magdy Elseadawy** | Definitive host/Site | Taenia species | Length of adult (m) | Distribution | Intermediate host | Larval stage | Larva site in I.H | Larva morphology | |:---|:---|:---|:---|:---|:---|:---|:---| | Humans in small intestine | _T. Saginata_ The beef tape worm | 5-10 | Worldwide | Cattle | _Cysticercus bovis_ | Muscles | Small (1 cm in diameter) fluid-filled cysts with single invaginated scolex (has 4 suckers only). | | | _T. Solium_ The pork tape worm | 5 | Latin America, Africa, Asia | Pigs and humans (autoinfection) | _Cysticercus cellulosae_ | Muscles | Small (1 cm in diameter) fluid-filled cysts with single invaginated scolex (has 4 suckers only and an armed rostellum). | | Dogs in small intestine | _T. Ovis_ Common tape worm of dog | 2 | Worldwide | Sheep | _Cysticercus ovis_ | Muscles | Small (0.5 cm in diameter) fluid-filled cysts with single invaginated scolex (has 4 suckers and an armed rostellum). Cysticerci are usually found calcified. | | | _T. Hydatigena_ Largest Taenia of dog | 5 | Worldwide | Sheep, goat, buffalo, camel, pig | _Cysticercus tenuicollis_ | Peritoneum and attached to liver, omentum, mesentery | Large (up to 8 cm in diameter) fluid filled cyst with a single invaginated scolex (has 4 suckers and an armed rostellum) attach to the wall by long neck. | | | _T. Pisiformis_ Dog-rabbit tape worm | 2 | Worldwide | Rabbit | _Cysticercus pisiformis_ | Peritoneum | Small pea-sized fluid-filled cyst usually found in groups resembling a bunch of grapes. Each cyst has a single invaginated scolex with 4 suckers and an armed rostellum. | | | _T. Multiceps_ Muliceps muliceps | 1 | Worldwide | Sheep, goat, cattle | _Coenurus cerebralis_ | Brain and spinal cord | Large (5 cm in diameter) fluid-filled cysts and have several invaginated scolices (has 4 suckers and an armed rostellum) appear as white dots attached to the transparent walls. | | | _T. Serialis_ Muliceps serialis | 0.7 | Worldwide | Rabbit | _Coenurus serialis_ | Subcutaneous tissue | Large fluid-filled cysts and have several invaginated scolices (has 4 suckers and an armed rostellum) attached to the wall and arranged in lines. | | Cats in small intestine | _T. Taeniformis_ Cat-rodent | 0.6 | Worldwide | Rat and mice | _Strobilocercus fasciolaris_ | Liver | Found in pea-sized nodules partially embedded in liver parenchyma. It composed of a small fluid filled cyst attach to an evaginated scolex with false-segmented strobila. The | ## _Taenia_ spp. ### Macroscopic morphology | Species | Shape | Size | Color | |:---|:---|:---|:---| | _T. saginata_ | | 5-10 meter | Grayish white | | _T. solium_ | | 3-7 meter | | | _T. multiceps_ | large segmented tape worm | 1 meter | | | _T. serialis_ | | 0.7 meter | | | _T. hydatigena_ | | 5 meter | | | _T. ovis_ | | 2 meter | | | _T. Pisiformis_ | | 2 meter | | | _T. taeniformis_ | | 0.6 meter | | ## _Taenia saginata_ ### Scolex - Relatively large (about 1.5 mm in diameter). - 4 cup-shape muscular sucker. - Absent of rostellum and hooks. ## _Taenia solium_ ### Scolex - Relatively small (about 0.6-1 mm in diameter). - 4 cup-shape muscular sucker. - Provided with rostellum armed with double rows of taenid hooks. ## _Taenia spp._ ### Mature segments 1. Nearly squarish (slightly broader than long in shape. 2. One set of genital organs. 3. Irregular alternating Common genital pore. 4. Testes are Numerous (300-400 testes) and scattered on the segment. 5. Ovary are Bilobed and Mihli's gland found between the two lobes. 6. Vitelline glands are - Compact mass behind the ovary. 7. Uterus are Simple tube extend anteriorly in the median plane. ### Gravid segments * **_Taenia saginata_** * Much Longer than broad in shape. * Uterus are Longitudinal stem with 15-20 lateral branches on each side. * **_Taenia solium_** * Longer than broad but smaller than of _Taenia saginata_. * Uterus are Longitudinal stem with 7-12 lateral branches on each side. ## _Taenia spp._, Life cycle 1. Eggs or gravid proglottids in feces and passed into environment 2. Cattle (_T. saginata_) and pigs (_T. solium_) become infected by ingesting vegetation contaminated by eggs or gravid proglottids 3. Oncospheres hatch, penetrate intestinal wall, and circulate to musculature 4. Oncospheres develop into cysticerci in muscle. 5. Humans infected by ingesting raw or undercooked infected meat. 6. Scolex attaches to intestine. 7. Adults in small intestine ## _Taenia spp._, eggs * Eggs are small in size (35-45μm). * Globular or spherical in shape. * Brownish in color. * It has emberyophore that double contoured, radially striated and contains a hexacanth embryo. ## _Cysticercus bovis_ - cyst occurs in the intermuscular connective tissue of cattle. - spindle in shape. - creamy white in color. - about 1 cm. - surrounded with thin fibrous capsule and embedded in muscle fibers. - cyst has one envaginated scolex has 4 cup-shape muscular sucker and absent of rostellum and hooks. ## _Cysticercus Cellulosae_ - cyst has one envaginated scolex has 4 cup-shape muscular sucker and provided with rostellum armed with double rows of hooks. - spindle in shape. - about 1 cm. - surrounded with thin fibrous capsule and embedded in muscle fibers. ## Cysticercus tenuicollis - It is the intermediate stage of _Taenia hydatigena_. - Found in the peritoneal cavity of ruminants (sheep, goat and cattle) being attached to the viscera. - It is seen as a large bladder (8 cm in diameter) containing fluid with one long neck invaginated scolex. ## Strobilocercus fasciolaris - It is intermediate stage of _Taenia taeniformis_. - Found in liver of rat and mice. - It is seen as a small vesicle with a long, falsely segmented neck ended with envaginated scolex having a rostellum carrying two crowns of taenoid hooks. ## Coenurus cerebralis - It is the intermediate stage of _Muticeps multiceps_. - Found in the brain and or spinal cord of sheep and other ruminants. - Size up to 5 cm in diameter. - It is seen as a large fluid filled cyst with a transparent wall through which clusters of invaginated scolices are seen on its internal wall. - Each scolex has 4 cup-shape muscular sucker and provided with rostellum armed with double rows of hooks with a transparent wall. ## _Taenia saginata_ - **PATHOGENESIS** Infections are usually asymptomatic in humans and claves; however, infected persons may develop diarrhea and hunger pains. - **EPIDEMIOLOGY** The infection is common in developing as well as developed countries. In many developing countries, human sanitation is poorly developed and the prevalence in humans is high. Calves are often infected during their first few days after birth from infected stockman whose hands contaminated with the eggs. - **In Egypt**, T. saginata prevalence in humans ranges from 0.4 – 6.0%, and up to 6% of cattle have been diagnosed with cysticercus bovis during meat inspection in various slaughterhouses. **Buffaloes** are also infected, but at lower rates. - **DIAGNOSIS** through detection of T. saginata eggs and or/ gravid proglottids in stools of humans. The cysticerci can be diagnosed during meat inspection of slaughtered cattle and buffaloes. **Multiple incisions** in heart, tongue, masseter muscles, intercoastal muscle and diaphragm are required. - **CONTROL** The most important measure to control infection in the developing countries is to **avoid use of human sludge as a fertilizer** for agricultural lands. **Meats should be thoroughly cooked at not less than 57 °C to kill the cysticerci.** In slaughterhouses, infected bovine carcasses more than 25 cysticerci should be condemned. In light infestations, carcasses should be frozen at – 10 °C for at least 10 days. ## _Taenia solium_ - **PATHOGENESIS** Adult _T. solium_ infections in humans and the cysticerci in pigs are asymptomatic. However, when man is infected with the cysticerci, various clinical signs may occur depending on the location of the cysts in the tissue or organ. - **Neurocysticercosis** is the most serious pathology and occurs due to development of the cysticerci in the central nervous system causing mental disturbances, epilepsy and increased intracranial pressure. The cysticerci may also develop in the eye causing loss of vision. - **EPIDEMIOLOGY** Human infections are prevalent in **pork-consuming countries** particularly in Latin America, where neurocysticercosis is considered the most significant food-borne parasitic zoonoses. **In Egypt**, infections are virtually absent. - **DIAGNOSIS** The cysticerci can be diagnosed during meat inspection of slaughtered pigs. In **humans**, _T. solium_ eggs and or/ gravid proglottids can be detected in stools of infected persons. **Neurocysticcerosis-patients** are diagnosed by computed scanning techniques as well as serological assys to detect antibodies in the cerebrospinal fluid. - **CONTROL** As described for _T. saginata_. In addition, the exclusion of pigs from contact with human beings and the proper standards of personal hygiene will reduce the prevalence of infection. ## _Taenia Multiceps_ - **PATHOGENESIS** Acute coenurosis is common in lambs than adult ewes, and results from migration of a large number of the oncospheres leading to multifocal necrotic regions in brain cortex. * In adults, chronic coenurosis is common and the mature coenuri represent space-occupying lesions causing nervous manifestations in infected sheep, which depend on the location of the coenuri. The disease is known as **cerebral coenurosis, gid or sturdy** and the symptoms include circling, stargazing and staggering gait. - **EPIDEMIOLOGY** Cerebral coenurosis is quite common in sheep from Egypt. - **TREATMENT** Surgery is considered the most effective method for the treatment of cerebral coenurosis in small ruminants, but is often not carried out because of the limited finances of many sheep and goat breeders. However, coenurosis can also be controlled effectively through preventative measures, such as anthelmintic treatment of dogs and the proper disposal of infected sheep carcasses. ## _Taenia hydatigena_ - **PATHOGENESIS** Large number of migrating cysticerci in the liver parenchyma may cause severe hepatitis, a condition known as "hepatitis cysticercosa" and is often fatal, and often associated with “Clostidium novyi' causing the “Black leg” disease. Chronic infections are symptomless. - **EPIDEMIOLOGY** Cysticercus tenuicollis have been **frequently found in slaughtered sheep and goats from Egypt**; however, hepatitis cysticercosa cases have not been reported. ## _Echinococcus_ spp. - **Name:** - _Echinococcus granulosus granulosus_. - _Echinococcus granulosus equinus_. - **Common name:** Dwarf tape worm of canine or the smallest tapeworms of dogs. - **F.H:** - For _E. g. granulosus_: Dogs and related carnivorus except red fox. - For _E. g. equinus_: Dogs and red fox. - **I.H:** - For _E. g. granulosus_: Ruminants, pig and man (Horses and donkeys are resistant. - For _E. g. equinus_: Horses and donkeys. - **Site:** - in F.H: Small intestine. - in I.H: In any organs of the body especially lung and liver. - **Larval stage:** Hydatid cyst. ## _Echinococcus granulosus_, adult. - **Scolex** is very small and provided with four suckers and a rostellum with two crowns of taenoid hooks (30 - 36). - **The strobila** consist of 3 - 4 (usually 3) segments; one immature, one mature and the third is gravid. - **The mature segment** is longer than broad, the ovary is horse-shoe, found posteriorly with the Vitelline glands forming a compact mass behind it. - **The gravid segment** is longer than broad measuring about the half of the worm length, the gravid uterus is a longitudinal stem provided with 12 - 15 main lateral pouches filled with egg. ## _Echinococcus granulosus_ Life cycle. - Intermediate host - Hydatid cyst - Definitive host - Egg - Adult - Adult ## Hydatid cyst - cyst surrounded by layer of opaque connective tissue and has a thick wall consists of two layers external thick laminated layer and internal nucleated germinal layer. - it has many invaginated scolices as attached, free scolices and broad capsule (scolices surrounded by germinal epithelium). - The scolices has 4 cup-shape muscular sucker and provided with rostellum armed with double rows of hooks. - From hen's egg to child's head. - Found embedded in internal organs. ### Hydatid cyst, cross section in cystic wall on slide - a cyst surrounded by layer of connective tissue and has a thick wall consists of two layers external thick laminated layer and internal nucleated germinal layer and scolces with restellum and hooks that scolices may be attached, free or found as broad capsule. - Found embedded in internal organs. - Endogenous and exogenous daughter cell may be developed. ## Hydatid sand - Hydatid sand consists of several free scolces and broad capsule swimming in the Hydatid fluid. - The scolices are microscopic and Each scolex has 4 cup-shape muscular sucker and provided with rostellum armed with double rows of hooks. ## _Echinococcus granulosus_ - **Molecularly**, eleven _E. granulosus_ genotypes have been reported and named G1 to G11. - **According to the susceptibility of intermediate hosts to infections with various genotypes:** - **_E. granulosus senso stricto_: G1** (sheep strain), **G2** (Tasmanian sheep strain) and **G3** (buffalo strain). - **_E. equinus_: G4** (horse and donkey strain). - **_E. ortleppi_: G5** (cattle strain). - **_E. canadensis_: G6** (camel strain), **G7** (pig strain) and **G8-10** (cervid strains). - **_E. felidis_: G11** (lion strain). - **PATHOGENESIS** - In dogs, infections are asymptomatic even with thousands of worms. In intermediate hosts, the disease is known as cystic echinococcosis (CE). In animals, CE is usually silent. - On the contrary, CE has pathogenic significance in humans. When large hydatid cysts develop in lungs, respiratory distress can be evidenced. In addition, abdominal distension can be revealed when several cysts develop in the liver. **Rupture of the hydatid cysts can cause anaphylactic shock in humans.** - **EPIDEMIOLOGY** - **CE occurs worldwide.** Sheep appear to be the **most important intermediate host** due to the close association with dogs. In the Middle East, camels are the most important intermediate host. **In Egypt, many CE-infected persons have been reported in the recent few years, and the G6 (camel strain) have been found prevalent among those patients.** In animals, CE occurrence has increased over time and the recent surveys are alarming from Egypt. - **DIAGNOSIS** - Infected dogs can be diagnosed through detection of taeniid-like eggs in **feces**. Those eggs should be identified molecularly using a **PCR amplification approach**. Infected **domestic animals** are usually diagnosed during carcass inspection at slaughterhouses. In humans, scanning radiography is required as well **as sero-testing**. - **TREATMENT** - In humans, chemotherapy, cyst puncture, and PAIR (percutaneous aspiration, injection of chemicals and re-aspiration) have been used to replace surgery as effective treatments for cystic echinococcosis. However, surgery remains the **most effective treatment** to remove the cyst and can lead to a complete cure. ## _Echinococcus multilocularis_ - **PATHOGENESIS** In man, the cysts are usually sterile and developed in the liver or lungs. The disease is known as **alveolar echinococcosis, similar to liver cancer and is fatal with not treatment available.** - **EPIDEMIOLOGY** _Echinococcus multilocularis_ is found in the **USA, Canada and Europe.** **No cases have been reported in Egypt**; however, the parasite has been reported in dogs from neighbouring countries (Tunisia and Morocco).