Echinococcosis Overview and Control Measures

Echinococcosis Overview

• Echinococcosis is a zoonotic disease caused by tapeworms of the Echinococcus genus.
• It occurs in four forms: cystic echinococcosis (hydatidosis), alveolar echinococcosis, polycystic neotropical echinococcosis, and unicystic neotropical echinococcosis.
• Cystic and alveolar echinococcosis are the most medically and public health relevant forms in humans.

Objectives of the Presentation

• Describe and discuss the epidemiology, mode of transmission, and preventive and control measures of Echinococcus granulosus.
• Describe and discuss the epidemiology, mode of transmission, and preventive and control measures of E. multilocularis.

Introduction to Echinococcosis

• Human echinococcosis is a zoonotic disease transmitted from animals to humans.
• The parasite is a tapeworm.
• Echinococcosis occurs in four forms.

Echinococcus granulosus (Cystic Echinococcosis)

• This form, also known as hydatid disease, results from infection with E. granulosus
• The cysts are typically located in the liver and lungs, and less frequently in other organs like bones, kidneys, and spleen.
• The presentation is frequently asymptomatic.

Distribution of E. granulosus and Cystic Echinococcosis (2011)

• A global map shows high-endemic areas, regions with rare cases, and areas where the parasite is probably absent.

Echinococcus multilocularis (Alveolar Echinococcosis)

• This type of echinococcosis is caused by E. multilocularis
• It usually develops in the liver and may expand widely with metastases to other organs.

Identification of E. granulosus

• E. granulosus is in the larval stage of a tapeworm.
• It is responsible for the most common form of hydatid disease.
• The cysts slowly enlarge over several years.
• Cyst sizes range (1-15 cm) in diameter and may be larger.
• Infections are often asymptomatic until the cysts cause significant effects.
• Signs and symptoms depend on the size, location, and number of cysts.

Infectious Agent, Reservoir, and Intermediate Hosts for Echinococcus granulosus

• The infectious agent is Echinococcus granulosus, a small tapeworm.
• Definitive hosts are dogs and other canids, who may harbor thousands of adult tapeworms.
• Intermediate hosts include sheep, goats, pigs, horses, other animals, and humans.
• The incubation period ranges from 12 months to years. This depends on the number and location of the cysts, and their growth rate.

Period of Communicability & Susceptibility for E. granulosus

• The infection is not directly transmitted between humans or from one intermediary host to another.
• Dogs shed eggs 5-7 weeks after infection.
• Most infections resolve after 6 months, but some adult worms may remain up to 2-3 years.
• Children are more susceptible due to higher risk of contact with dogs and poorer hygiene practices.

Mode of Transmission for E. granulosus

• Human infection often involves hand-to-mouth transfer of eggs from infected dogs.
• Eggs also spread through contaminated food, water, soil, or fomites, which come in contact with infected dog feces.

Life Cycle of Echinococcus granulosus

• The life cycle involves six steps. These steps include:
  • Adult tapeworms in the intestines of definitive hosts (dogs)
  • Eggs released in dog feces
  • Ingestion of eggs by intermediate host (sheep, or other species)
  • Eggs hatch, oncospheres penetrate the intestinal wall
  • Develop into protoscolices, which form hydatid cysts in the liver, lungs, or other tissues of intermediate hosts
  • Dogs and other canids get infected after consuming an infected intermediate host

Cyst Layers and Contents

• The cyst has a fibrous capsule (made by the host) and a lining made by the Echinococcus
• Within the cyst cavity filled with fluid are daughter cysts (containing protoscolices.
• The protoscolices are small bud-like structures that can develop into more cysts.

Echinococcosis Epidemiology

• Echinococcus granulosus is a cosmopolitan parasite, found on all continents.
• Endemic regions experience significant public health problems, including Central and South America, parts of Europe, the Middle East, North Africa, sub-Saharan Africa, Russia, and China.
• The annual incidence rates for diagnosed human cases vary greatly, from less than 1 per 100,000 inhabitants to high levels in endemic areas.

Mortality/Morbidity for Cystic Echinococcosis

• Cystic echinococcosis is rarely fatal.
• Death can be caused by anaphylactic shock or if the cyst causes cardiac tamponade (pressure on the heart.)
• Rare locations of the cyst (muscle, bone, brain, or orbit) can lead to severe disabling symptoms (blindness, paralysis, etc.).

Race, Sex, and Age in Relation to Infection

• No racial predisposition exists.
• In endemic countries, females are more often infected than males, likely due to lifestyle practices and greater contact with the parasite.
• Individuals of all ages are affected, but children often have higher infection rates linked to increased contact with dogs.

Signs and Symptoms of Infection with E. granulosus

• Human infection typically leads to one or more hydatid cysts, frequently in the liver and lungs, occasionally bones, kidneys, spleen, muscles, and the central nervous system.
• The incubation period can be many years with no symptoms.
• Cysts growing too large can cause signs like abdominal pain, nausea, and vomiting (especially in the liver.)

Signs and Symptoms: Lung Involvement

• If lungs are involved, symptoms include chronic coughing, chest pain, and shortness of breath.
• Other general symptoms depend on the cyst location and pressure exerted on nearby tissues.

Case Scenario (Patient presented with abdominal pain)

• A 32-year-old female patient presented with right upper quadrant and epigastric abdominal pain and nausea.
• Physical examination revealed an abdominal mass.
• Liver function tests were normal.
• An MRI showed a low-density cystic mass (Hydatid cyst).
• Cystectomy was performed, and hydatid sand containing protoscolices of E. granulosus was found.
• Antiparasitic treatment given and the patient was asymptomatic after two months.

Methods of Control: Preventive Measures

• Avoid ingesting raw vegetables/water contaminated with dog feces.
• Hygiene practices, such as handwashing, and washing fruits/vegetables.
• Educate high-risk individuals about exposure to dog feces or infected dogs.

Control Measures: Interrupting Transmission

• Prevent contact between dogs and potentially contaminated/uncooked animal viscera.
• Dispose of viscera by burning or deep burial.

Control Measures: Dog Treatment

• Periodically treat high-risk dogs and dogs in high-risk areas.

Control Measures: Safety Precautions

• Field and laboratory personnel must adhere to strict safety precautions to prevent ingesting tapeworm eggs.

Control Measures: Patient, Contact, and Environment

• Report cases to the local health authority.
• Isolation, concurrent disinfection, quarantine, and vaccination of contacts is recommended.
• Investigate contacts and the source of infections using ultrasound, X-rays, etc., to check for cysts.
• Assess individual's practices and behaviors that increase infection risk.

Control: Specific Treatment

• Treatment is based on WHO classification.
• Surgical intervention is commonly used for liver cysts.
• Percutaneous techniques (like PAIR: puncture, aspiration, injection, re-aspiration) are used for other cyst types
• Mebendazole and albendazole used for treatment.
• If the primary cyst ruptures, praziquantel and protoscolicidal agents are used.

Prognosis

• Prognosis is usually good, depending on the cyst location.
• Surgery for treating cardiac cysts can be quite risky.
• Development of new cysts after removal of one cyst is sometimes observed.

Echinococcosis due to E. multilocularis (Alveolar Echinococcosis)

• Highly invasive and destructive disease due to the E. multilocularis larval stage.
• Lesions are commonly found in the liver, but they can spread widely, resulting in secondary cysts in other organs.
• Clinical manifestations often mimic hepatic carcinoma or cirrhosis.
• The disease is usually fatal, but in some cases, spontaneous cure and calcification have been observed.
• Diagnosis often involves histopathology and serodiagnosis using E. multilocularis antigen.

Echinococcus multilocularis Staging

• WHO has proposed a staging system (PNM) based on:
  • Hepatic location(P)
  • Extra-hepatic involvement of neighboring organs (N)
  • Presence of metastases (M)

E. multilocularis Reservoir and Transmission

• Adult tapeworms are found mostly in foxes.
• Human infection can occur if dogs or cats eat rodent intermediate hosts.
• Transmission happens via ingestion of eggs in fecally contaminated areas.

E. multilocularis Signs and Symptoms

• Alveolar echinococcosis has an asymptomatic incubation period of 5-15 years.
• Characteristic symptoms include weight loss, abdominal pain, general malaise, hepatic failure.
• Metastasis to adjacent or distant organs (e.g. lungs, brain) may occur.
• The disease is progressive and usually fatal.

Treatment for E. multilocularis

• Radical surgical excision followed by chemotherapy is often the approach.
• Mebendazole or albendazole may be used for a fixed or extended period after surgery, or for inoperable patients, to prevent disease progression.

Echinococcosis due to E. Vogeli and E. Oligarthrus (polycystic and unicystic echinococcosis)

• Occurs in the liver, lungs, and other viscera with symptoms varying depending on cyst size/location.
• The species is identified by its rostellar hooks.
• These species are unique due to how the germinal membrane forms new cysts and septum to divide the cavity for numerous microcysts.
• Brood capsules containing protoscolices develop in the microcysts.
• E. vogeli and E. oligarthrus are commonly found in Central and South America.
• Immuno-diagnosis isn't sufficient to always identify this species from alveolar echinococcosis.
• Albendazole is commonly used for chemotherapy.

Summary of Echinococcosis

• Human echinococcosis is a parasitic disease caused by Echinococcus tapeworms.
• Cystic and alveolar echinococcosis are prevalent forms.
• Humans are infected through ingesting parasite eggs in contaminated food, water, soil, or from direct contact with animal hosts.
• The treatment is often complex and may involve lengthy surgery and medication.

Prevention Programs:

• Deworming of dogs, improved food inspection, slaughterhouse hygiene, public education campaigns, and vaccination of lambs.
• The goal is to break the cycle of transmission or to lower the infection rate amongst the population.

This quiz provides an overview of echinococcosis, a zoonotic disease caused by Echinococcus tapeworms. It covers the various forms of the disease, their epidemiology, transmission, and important preventive measures. Explore the impact of E. granulosus and E. multilocularis on public health.