Echinococcus Granulosus, a Parasite Producing Hydatid Cyst: A Review

Abstract

Echinococcosis is a parasitic disease caused by tapeworms of the genus Echinococcus, such as Echinococcosis granulosus. It is characterized by the development of hydatid cysts, which tend to form particularly in the liver and lungs. Echinococcosis granulosus has a complex life cycle involving dogs as definitive hosts and herbivores such as sheep, as intermediate hosts and canbecome infected by consuming contaminated food or water contaminated by Echinococcus eggs. Hydatid cysts are prevalent in rural areas of Africa, the Mediterranean region, South America, Central Asia, and Eastern Europe, where close contact between humans, dogs, and livestock is common. The clinical symptoms of hydatid cyst disease depend on the location and size of the cysts. Many people with hydatid cysts may have no symptoms for years. However, as the cysts grow, they can cause various symptoms, including abdominal pain, nausea and vomiting, chest pain, coughing, headaches, seizures, vision problems, and shortness of breath. The most Effective treatments for hydatid cyst are surgery and Chemotherapy. Chemotherapy has adverse side effects, so plants are used for treatment because they have fewer side effects and are safer. If left untreated, a hydatid cyst can lead to serious problems such as organ failure, rupture, and even death. Understanding the epidemiology and life cycle of Echinococcosis granulosus is crucial for improving diagnosis, treatment, and control measures. This review aims to study Echinococcosis granulosus to improve diagnosis and treatment and to enhance epidemiological understanding and prevention strategies, thereby reducing the public health impact of cystic echinococcosis.

1. Introduction

Hydatid cyst disease, also known as cystic echinococcosis, is prevalent in many parts of the world ( 1 ). Cystic echinococcosis is a serious zoonotic disease caused by the larval stage of the parasite Echinococcus granulosus. Echinococcus granulosus has a life cycle in which dogs are the definitive host and sheep, goats or other livestock are the intermediate hosts ( 2 ):

• • Hydatid cyst disease is especially prevalent in rural, underdeveloped areas where people raise livestock, such as:Africa: Hydatid disease is a major public health concern in many African countries, including those in North Africa, the Horn of Africa, and Southern Africa. Countries with high incidence rates include Morocco, Tunisia, Algeria, Libya, Egypt, Ethiopia, Kenya, and South Africa ( 3 ).

• • South America: Hydatid disease is endemic in several South American countries, especially Argentina, Peru, Chile, and Uruguay. The disease is associated with the domestic dog-sheep cycle in these regions ( 4 ).

• • Mediterranean region: Hydatid disease is prevalent in Mediterranean countriessuch as Spain, Italy, Greece, and Turkey ( 5 ).

• • Central Asia: Hydatid disease is a significant health problem in Central Asian countries such as Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan ( 6 ).

• • Eastern Europe: Hydatid disease is present in some Eastern European countries such as Romania and Bulgaria ( 7 ).

The high incidence of hydatid disease in these regions is linked to the close contact between humans, dogs, and livestock, as well as poor sanitation and hygiene practices. Hydatid cysts cause severe illness and possible death in humansand result in economic losses due to treatment costs, patient disability,and reduced animal product output. Studying hydatid cysts and the Echinococcus parasite help us better understand and diagnose cystic echinococcosis,a parasitic disease .This review will focus on hydatid cysts,the parasite that produces them, and their diagnosis, transmission and epidemiology, and prospects for treatment, control and prevention.

2. Echinococcus Granulosus Parasite and Life Cycle

The parasite Echinococcus granulosus is a zoonotic tapeworm parasite that primarily infects herbivorous animals such as sheep, goats, and cattle. Its life involves a definitive host, such as dogs and other canids), and an intermediate host, such as sheep and other herbivores (Figure 1). The adult tapeworm resides in the intestine of the definitive host, while larval stages infect intermediate host and develop into hydatid cysts in organs such as the liver and lungs (Figure 2). Echinococcus granulosus eggs eventually enter the environment through the host's feces and can survive outside the host for up to two years. Intermediate hosts ingest the egg,and larval stages develop in hydatid cysts. These cysts grow slowly over several months and, if ingested by the definitive host,they can develop into adult tapeworms, completing  the life cycle ( 8 ). Understanding the epidemiology and life cycle of Echinococcus granulosus is important for the following reasons:

Figure 1.

Echinococcus granulosus life cycle.

Figure 2.

Hydatid cyst of the liver.

• 1. Improving diagnosis and treatment with specific diagnostic tests and targeted treatment methods.

• 2. Implement transportation strategies. Identifying high-risk areas and animal sanctuaries allows for the implementation of effective management strategies.

• 3. Vaccine Development: Identify protective antigens to design effective vaccines for human and animal hosts.

• 4. Drug Resistance Monitoring: Monitoring the emergence of drug-resistant strains to guide appropriate chemotherapy strategies.

• 5. Promoting One Health: Achieve integration between human, animal and environmental health, and address this shared disease in humans and animals.

Therefore, The study of hydatid cysts and echinococcosis parasites is an important area of research to address the significant global burden of cystic echinococcosis.

2.1. The clinical Symptoms and Pathogen of Hydatid Cyst Disease

The clinical symptoms of hydatid cyst disease depend on the location and size of the cysts. Many people with hydatid cysts may have no symptoms for years because the cysts grow slowly. However, as the cysts grow, they can cause a various symptoms, including:

• • Abdominal pain, nausea and vomiting (if the cysts are in the liver) ( 9 ).

• • Chest pain, cough, and shortness of breath (if there is a cyst in the lung) ( 9 ).

• • Neurological symptoms such as headaches, seizures and vision problems (if there are cysts in the brain).

• • Allergic reaction  and anaphylaxis with cyst rupture ( 10 ).

If left untreated, a hydatid cyst can lead to serious complications, including organ failure, rupture, and even death. Early diagnosis and appropriate treatment, which may include a combination of surgery, medication and other interventions, are essential for controlling this viral disease ( 11 , 12 ).

2.2. Prevention of Hydatid Cyst Disease

Preventing hydatid cyst disease involves disrupting the life cycle of Echinococcus granulosus. The main preventive measures are:

• • Bathe the dog regularly with tapeworm medication to remove adult tapeworms from the intestines.

• • Limit dogs' access to raw or infected livestock carcasses to avoid ingesting parasites ( 13 ).

• • Dispose of contaminated animal parts by burning or deep burial.

• • Educate people, especially those in rural areas, about the importance of good hygiene, such as washing hands before eating and after handling animals.

• • Improve sanitation and access to clean water in affected areas. Implement monitoring and control program of hydatid disease in livestock ( 14 ).

2.3. Treatment of Hydatid Cyst Disease

The treatment of hydatid cyst disease involves various methods, each with its own advantages and limitations. The most appropriate treatment depends on factors such as the cyst's size and location, the patient's overall health, and the availability of medical resources. The treatment of hydatid cyst disease involves various methods, each with its own advantages and limitations. The most appropriate treatment depends on factors such as the cyst's size and location, the patient's overall health, and the availability of medical resources.

2.4. Surgical Options

Surgical treatment is considered the most effective method for removing hydatid cysts. There are two types of surgery: radical, where the entire cyst and surrounding tissue are removed, or conservative, where only the affected organ is partially resected, if possible ( 15 ). Surgical treatment is considered the most effective method for removing hydatid cysts. There are two types of surgery: radical, where the entire cyst and surrounding tissue are removed; and conservative, where only the affected organ is partially resected, if possible. Compared to conservative surgery, radical surgery is considered a better treatment method for hydatid cysts. This conclusion is based on the results of various studies comparing the outcomes of radical and conservative surgical interventions for liver hydatid disease. Radical surgery involves completely removing the cyst and surrounding tissue. This significantly reduces the risk of postoperative recurrence. In contrast, conservative surgery, which involves partial resection or drainage of the cyst, has been associated with higher rates of complications and recurrence. While conservative surgery may be a good choice in some cases, such as when the cyst is located in a sensitive location or the patient is seriously ill, radical surgery is generally more effective in preventing postoperative recurrence and providing  timely treatment ( 16 ).

2.5. Percutaneous intervention (PAIR)

Percutaneous intervention, also known as PAIR, is a minimally invasive procedure. It involves removing the cyst using a needle inserted into the skin. This is often combined with albendazole therapy to prevent recurrence of the cyst ( 16 , 17 ).

2.6. Chemotherapy

Chemotherapy using albendazole or mebendazole is another treatment option. These medications effectively reduce ing the size of the cysts and can be used in combination with PAIR or as a standalone treatment. However, the efficacy of chemotherapy alone isnot very effective, soit is often used in conjunction with other methods ( 18 ).

2.7. Watch and Wait Approach

In some cases, hydatid cysts are inactive and cause no symptoms. In these cases, a "watch and wait" approach is often recommended, which involves monitoring the cyst for signs of activity or growth. This method is usually used for static cysts that are not problematic ( 19 ). Generally,the most effective  method for treating cystic disease  is surgical removal of the cyst. However, if surgery is not possible or if the cyst is located in a sensitive area, percutaneous drainage and chemotherapy using albendazole or mebendazole may be recommended, In humans, these drugs must be taken in high doses and for a long time, and they have undesirable side effects. Giventhese facts, it is crucial to develop new drugs that are more effective and have fewer side effects for treating hydatid cysts. . For this reason, identifying and preparing effective, side-effect-free drugs, such as medicinal plants, for the treatment of hydatid cysts is important.

2.8. Scolicidal Effects of Plant Extracts

In recent decades, scientists have searched for new, safe and effective scolicidal agents to inactivate the contents of cysts. Recently, studying the antiparasitic activity of medicinal plants has become a popular research topic.Studies have demonstrated the the potent scolicidal properties of various plants including Eucalyptus microtheca ( 20 ), Myrtus communis ( 21 ), Sideritis perfoliata ( 22 ), Sambucus ebulus ( 23 ), Zingiber officinale ( 24 ). The hydroalcoholic extract of Pistachio Atlantica fruits exhibited strong scolicidal activity in laboratory tests ( 25 ). Phytochemical analysis of the plant extracts showed the revealed of various bioactive compounds like flavonoids, alkaloids, tannins, and terpenoids. These phytochemicals appear to be responsible for the anti-protoscolices (anti-hydatid cyst) effects of the plant extracts. The mechanisms by which these plant extracts kill the protoscolices are not fully understood but may involve membranes disruption , enzymatic activities inhibition , and oxidative stress induction. The concentration and exposure time of the plant extracts appear to be important factors in determining their scolicidal potency. In summary, the phytochemicals such as alkaloids, flavonoids, and terpenoids, seem to be the key component conferring the anti-hydatid cyst effects observed in these studies ( 26 - 29 ). The mechanisms by which these plant extracts kill protoscolices are not fully understood but may involve membrane disruption, enzymatic activity inhibition, and oxidative stress induction. The concentration and exposure time of the plant extracts appear to be important factors in determining their scolicidal potency. In summary, phytochemicals such as alkaloids, flavonoids, and terpenoids seem to be the key components conferring the anti-hydatid cyst effects observed in these studies ( 26 - 29 ).

2.9. The identification of Live and Dead Parasites Using Eosin Dye

In parasitology, the identification of live and dead parasites using eosin dye is a technique employed in parasitology to distinguish between viable and non-viable parasites.Live parasiteshave intact cell membranes which prevent certain dyes ,like eosin, from entering the cell. Dead parasites, on the other hand, have compromised cell membranes that allow the dye to penetrate and stain the cell (Figure 3). In this method, a solution of eosin dye is mixed with the parasites, and the mixture is then observed under a microscope. Live parasites do not take up the dye and appear as clear or transparent cells. Dead parasites are stained red or pink because the dye can penetrate their damaged cell membranes. Eosin dye is used in this process because it is a vital stain, meaning it is excluded by live cells but taken up by dead cells. This property makes eosin dye useful for quickly and easily assessing the viability of parasites ( 30 ).

Figure 3.

Live and dead parasites using eosin dye. Live parasites (a). Dead parasites (b).