Lecture 6 - Cestodes (Biology and Epidemiology)

What are the risk factors of human AE identified?

- Dog ownership - Free ranging dogs - Infrequent deworming

What other species of Echinococcus exist?

- E. canadensis (Cervid strain G8/G10) - E. intermedius (Pig strain G7) - E. intermedius (Camel strain G6) - E. equinus (Horse strain G4) - E. ortleppi (Cattle strain G5)

What is the pathology of cystic echinococcosis (CE)?

- Expansive growth - Liver > Lungs >> Other Organs - LOW fatality rate * 1 DALY per case

What are the clinical and laboratory diagnosis of human Echinococcosis?

- Imaging - Serology (specific Ab detection) - Molecular confirmation - Macro-and histopathology

What is the pathology of cysticersosis?

Usually depends on the infected organs and the immunological reaction (inflammatory response). *Severe symptoms in the case of NEURAL cysticercosis.

What factors affect the urban cycle of E. multilocularis and the infection pressure with E. multilocularis eggs?

- Agriculture & Recreational Area and Urban Periphery - Human population - Anthropogenic food supply - Fox density - Abundance of intermediate hosts - Predation on rodents by foxes - Environmental egg contamination - Recreational and soil linked activities (farming, gardening, etc.) - Free ranging dogs and cats

What are some control strategies against E. granulosus (sheep strain) in continental areas which proved effective?

- Antihelminthic treatment of dogs -Combined antihelminthic treatment of dogs and vaccination of sheep - Vaccination of sheep, antihelminthic treatment of dogs and removal of old sheep (this was the most effective. shortest period of time as well)

What was found in the study of socio-cultural factors on transmission of Taenia spp. and Echinococcus granulosus in Kosovo?

- E. granulosus was common in sheep in the mountains - CE was high in humans (high annual incidence even in urban areas) - Prevalence of E. granulosus in dogs: 1.3% - CE in slaughtered cattle 72% over the country ***Found that force of infection with parasites increased after the celebration of Eid due to high home slaughtering activity of mostly old sheep. Recommend treatment of all dogs 4-6 weeks after the Fast of Sacrifice and further treatment depending of slaughtering events.

What are alternatives of intra vitam diagnosis of intestinal Echinococcus infections?

- Genus identification: ELISA (ie; copra-antigens) - Species of strain identification: PCR/sequencing (ie; Taeniid eggs / copra-DNA) Monospecific or multiplex or multi-tests for polyspecificity *Specific immune reactions are not reliable

What are some of risks associated with CE caused by the E. intermedius (pig strain) in Lithuania?

- High number of pet dogs in villages - No antihelminthic treatment - Home slaughtering of pigs - Social conditions - Habits

What is the pathology of alveolar echinococcosis (AE)?

- Infiltrative growth - Liver >>> Other Organs - HIGH fatality * 37 DALYs per case

What are control strategies of cystic echinococcis?

- Long-term measures of PH education with primary health hcare - Veterinary PH activities (improvement of slaughter hygiene and meat inspections, dog registration and sanitation measures)

What are "attack phase" control strategies of CE?

- PH education of farmers - Improvement of slaughter hygiene and meat inspection (especially private sector) - Intensive praziquantel treatment of dogs - Monitoring of the epidemiology epidemiological situation - Vaccination of sheep (new approach) - Culling of infected (old) sheep) *No vaccine for dogs available

What is the morphology of E. granulosus?

- Protoscolex - Eevagianted protoscolex - Gravid worm

What are the goals of the European Scientific Counsel Companion Animal Parasites (ESCAAP)?

- Provide vets and pet owners the best possible information for controlling pet parasite infections, infestations, and zoonoses. - Create independent guidelines and educational materials for optimal pet parasite control - National activities focused on local situations

What is the current CE situation in Europe?

- Several thousand cases per year - There are no reasons not the establish control programs i the very near future. * There is SUFFICIENT epidemiological base line data available for control strategies for CE in Europe.

How is human cystic echinococcosis usually treated?

- Surgery - PAIR (Puncture, Aspiration, Injection, Re-aspiration) - Chemotherapy - Wait and see strategy

What are some control strategies of AE?

-Hygiene (Wash/cook food/hands/avoid fox contact) - Deworm dogs -Prevent dogs from predation on rodents - Elimination of definitive hosts (feasible only in small situations) - Intensive hunting within the border zone of the city of Zurich had no significant impact **Praziquantel treatment of dogs and foxes in endemic situations (Local baiting strategy)

What is the susceptibility of humans for AE?

-Risk of oral uptake -Risk of infection -Risk of disease In 100 cases of oral egg uptake: 1 AE case, 99 resistant (75 without liver lesions, 24 with "abortive" liver lesions)

What infectious diseases are caused by Echinococcus cestodes?

1 - Alveolar Echinococcosis (Echinococcus multilocularis AKA Alveococcus multilocularis) 2 - Cystic Echinococcosis, Hyatid Disease (Echinococcus granulosus)

What is the factors which affect transmission biology of E. multilocularis?

In the DEFINITIVE hosts: Ecology, Susceptibility, and Development In the INTERMEDIATE hosts: Ecology and Development

What was the control strategy for E. intermedius in Lithuania?

Praziquantel treatment of dogs with baits (4 times a year). This had a high impact in reducing transmission of CE.

How many sheep strain of E. granulosus exist?

Three: G1 / G2 / G3

This parasite's physiology depends on its current host. What are the different physiological forms of Taenia and Echinnococcus?

1 - Intestinal stage (***TAPE WORM***) in definitive host 2 - Larval stage (***METACESTODE***) in intermediate hosts/aberrant hosts/accidental hosts/dead-end hosts Note: Infectious eggs with oncospheres in between intestinal and larval stages (this is what infects intermediate hosts).

What are critical points of failure for Taenia saginata. control?

1 - Low morbidity (Generally just an embarrassing infection) 2 - Unsatisfactory meat inspection 3 - Difficult to control environmental contamination 4 - Vaccination of farm animals (cattle) are not commercialized and chemotherapy is not practical. *Ie in Switzerland: Relatively low economic impact and low medical significance -> Low priority for politics and no funding provided for control strategies.

What is the lifecycle of Echinococcus granulosus?

1 - Proglottid with eggs are released with excreta 2 - Eggs are taken up by sheep, cattle, camels, pigs, or humans. 3 - Cysts develop in liver (metacestodes) of intermediate host. 4 - Canines infected and parasite develops into adult.

What infectious diseases are caused by Taenia cestodes?

1 - Taeniosis (Taenia saginata) 2 - Taeniosis, Cysticercosis, Neurocysteicercosis (Taenia solium) 3 - Rare Cysteicercoses (Taenia spp. of carnivores) *Taeniosis → names of the intestinal disease Cysticercosis → name of disease of the metacestode extra-intestinal stage of the parasite (this is much more serious).

What is the global burden of cystic echinococcosis?

4.1 billion USD (54% human costs, 46% animal health costs) CE affects ~1.2 million people worldwide (3 million DALYs lost globally every year)

What is the WHO diagnosis criteria for AE?

At least one: - Typical lesions in imaging - Serology (screening and high specificity contamination of AE) - Histopathology - Detection of DNA in clinical specimen

Which intermediate host is Taenia saginata commonly found?

Cattle *Found a lot of Taenia saginata infected dairy cattle in Switzerland with taeniosis and bovine cysticercus.

What is the lifecycle of Echinococcus multilocularis?

Domestic animal (dogs, cats) and Foxes are the definitive host Eggs are found in excreta Rodents come into contact with contaminated feces Metacestode reproduces in liver of rodent Domestic animals come into contact with infected rodent Adult stage of parasite in domestic animals / foxes

What is the estimated number of new AE cases per year?

Europe: 100-200 (Significant increase found in Switzerland, Austria, Poland, Lithuania) Russia: 1,100 China: 17,000

What are the ways of E. multilocularis transmission?

Fox/Dog feces contaminate soil/food, etc. Humans come into contact with contaminated feces in the environment (hands (gardening, etc.) and contaminated foods)

What is the global distribution of cystic echinococcosis in intermediate hosts (caused by G1-3, G5, G7)?

G1-3 are predominant in most of Europe, the Middle East, and parts of Asia. G7 is predominant in parts of Central and Eastern Europe. G5 predominant in Central Europe (ie; Switzerland)

What is the epidemiological distribution of E. multilocularis in foxes?

Global North In Europe -> CENTRAL and EASTERN regions

What is the epidemiological distribution of Taenia solium (cyticercosis/taeniasis)?

High prevalence in the global south. Low prevalence in North America, Europe, and Australia.

Which type of infection is Taenia saginata most specific for?

High specificity for INTESTINAL INFECTION. Note: Only primates can host them in the intestine.

What are dead-end hosts?

Hosts which are involved as intermediate hosts in the lifecycle, but is not contributing to the transmission.

How does cysticercosis usually develop in humans?

Humans are usually ACCIDENTAL host after eating contaminated food with eggs, or due to mechanical transmission by flies, or reverse peristalsis.

Why is imaging important for diagnosis of human Echinococcosis?

Imaging provides the FIRST-LINE approach to diagnose human CE and AE, while serology provides strong complemental support. *Important for individual diagnosis and epidemiological investigations.

What are characteristics of E. multilocularis: intestinal stage?

Known: - Prepatency 26-37 days - Mean number of eggs per proglottis: 200-300 Unsure/Unknown: - Patency 2-3 months up to 1 year??? - Rate of proglottisation???? - Total egg production per worm?

What are the weaknesses of usual CE central strategies?

Long-term PH and veterinary PH activities may not be sufficient and TOO SLOW for effective E. granulosus control Need for "attack phase" control.

What is the E. multilocularis prevalence in dogs in Germany, Switzerland, and France?

Mean prevalence 0.2-0.3% (1,000 infected dogs in GH and 10,000 in GER) Dogs with free access to rodent habitats: 3-7%

What causes human AE?

Metacestode stage of Echinococcus multilocularis.

In general, how severe is pathology for intestinal and larval stages of Taenia and Echinococcus?

Moderate pathology = INTESTINAL stages Nearly no symptoms. V good adaptation of parasite in the intestines. Serious pathology = LARVAL stages

What is the Echinococcus ortleppi occurrence in cattle in Switzerland?

NO documented reports since 2000 in cattle (data from a slaughterhouse in St. Gallen, Switzerland).

Can humans who have cysticercosis contribute to the infectious cycle?

No. They are dead-end hosts. With this form of disease, humans cannot contribute to Taenia spp. transmission.

What are the susceptibility to infection and development of AE in different dead-end hosts?

Non-human primates: High infection and AE development Humans: Low infection (high in immunosuppressed) and Moderate-high AE development *Slide 79 for complete chart

Are more protoscoleces found in younger or older sheep?

Old. The mean number of protoscoleces observed in each age class shows that sheep 6 and older had the highest number.

What were some risk factors included in the analysis for bovine cysticercosis?

Railway lines near farms. Leisure activities on the farm. Car par on the farm. Visitors on the farm.

What is the morphology of Taenia?

Scolex (head) with hooks/suckers for attachment. Microtriches throughout body for absorption of nutrients. (Makes them susceptible to chemotherapy) Segmented body -> each segment is a proglottid. Every proglottid has male and female organs. Each can produce thousands of eggs. Eggs are not released. Proglottids can detach and be excreted in stool.

How is intestinal Echinococcus infections (E. granulosus and E. multilocularis) usually diagnosed?

Sedimentation and Counting Technique (SCT) This is the GOLD STANDARD Sensitivity: 80-100% Specificity: >98%

What are two genera of cestodes?

Taenia and Echinococcus

What are carnivore transmitted cysticercoses?

Taenia crassiceps

Which intermediate host is Taenia solium highly specific for?

Taenia solium has high host specificity in intermediate hosts: PIGS.

Among other Taenia species, which one is the most common cause of cysticercosis?

Taenia solium. It is rarely other Taenia spp.

Based on reproduction, which genus of cestodes are easier to control?

Taenia spp. This is because from 1 egg, they either produce 1 cysticercus/strobilocercus or 100-1,000 coenurus. On the other hand, 1 egg from Echinococcus spp. : can get 1,000 - 10,000 larval stage parasites.

What are cestodes?

Tape worms

What is the main biological trait of Taenia and Echinococcus cestodes?

They are obligate dixenous parasites. (2 hosts to complete lifecycle) *Definitive and intermediate hosts are usually different species.

True or False. There are more species of Echinococcus which cause cystic echinococcosis than alveolar echinococcosis.

True

Why is it hard to treat cysticercosis?

When treated, dead cysticercus elicits severe or even fatal inflammatory response.

What is the epidemiological distribution of Taenia saginata?

Worldwide