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Giardia lamblia and giardiasis

  

Giardia lamblia is a small protozoan flagellate parasite. Giardiasis or giardia infection, the major diarrheal disease found worldwide, is a parasitic infection of the small intestine. It is caused by the parasite giardia lamblia it is diagnosed by examining a stool sample and sometimes taking a tissue sample from the small intestine. Giardiasis is spread through contact with infected people.

It can be contracted worldwide, according to the Centers for Disease Control and Prevention. However, it is more common in overcrowded developing countries that lack proper sanitary conditions and water quality control. Pet dogs and cats are often infected with giardiasis.

Giardia lamblia has two forms: an active form called trophozoites because  it moves with flagella, and an inactive form called the parasite cyst, giardia cyst, or cyst. Active trophozoites attach to the lining of the intestine and are responsible for causing the signs and symptoms of giardiasis.

Trophozoites cannot survive for long periods outside the body and therefore cannot cause infection to others. On the other hand, an inactive cyst can exist for long periods outside the body. Caused by giardia cysts in the stool of infected people, the infection is transmitted from one person to another through contamination of food with feces, or through fecal-oral contamination. Cysts also live in water for example in freshwater lakes and streams. As a result, giardiasis is the most common cause of waterborne parasitic diseases.

Host infection begins when the cyst is ingested with contaminated water or food, or through direct fecal-oral contact. The cyst is relatively inert, allowing it to survive for a long time in a variety of environmental conditions. After exposure to the acidic environment of the stomach, trophozoites are secreted into the small intestine. Trophozoites are the vegetative form and reproduce in the small intestine, where they cause symptoms of diarrhea and malabsorption.

 

                               

Causes of infection

The giardia parasite lives in soil, food and water. They can also be found on surfaces that have come into contact with animal or human waste.

Infection can occur via

1. Drink water in which pets have left their droppings, as these parasites thrive in the feces of animals and humans. It can be in contaminated water from swimming pools and lakes.
2. Eating raw or undercooked foods contaminated with the parasite.
3. Giardiasis from food is less common because heat kills the parasites. Poor hygiene when handling food or eating products washed with contaminated water can spread the parasite.
4. Changing a child's diaper and not washing hands adequately are risk factors for transmission from infected children. Children are at risk of contracting giardiasis through potty training from infected adults.
5. Direct contact with a person infected with the parasite or catching the parasite while working in health care centers are common ways of becoming infected.

Life cycle

Infection occurs when a person swallows giardia cysts from contaminated water, food, hands, surfaces, or objects.

When giardia cysts are swallowed, they pass through the mouth, esophagus and stomach into the small intestine where each cyst releases two by dividing into two in a process called longitudinal binary fission. They remain in the small intestine where they can be free or attached to the inner lining of the small intestine. The giardia parasites then feed. It absorbs nutrients from the infected person.

Both giardia cysts and trophozoites in the stool of a person with giardia infection can be observed microscopically to diagnose giardiasis. Giardia cysts become infectious immediately when passed in the stool or shortly thereafter, and the cysts can survive for several months in cold water or soil.

 

 

People most susceptible to infection

1. Giardia infection occurs when there is inadequate sanitation or inadequate treatment of drinking water. Giardia infection is one of the causes of traveler's diarrhea, which happens while traveling.
2. Giardiasis is a common cause of diarrheal outbreaks in health care centers and hospitals due to the high potential for fecal-oral contamination from children, their families and workers in care centres, who are all at risk of infection.
3. Children are three times more likely to become infected with giardia than adults.
4. People who drink contaminated water are also at risk of contracting giardiasis.
5. Giardiasis affects people of all ages. Infection is rare during the first six months of life in breastfed infants, but infants and young children have an increased susceptibility to infection. Age-specific prevalence continues to rise during infancy and childhood and begins to decline only in adolescence.
6. Many of the epidemics documented over the past two decades have originated in care centers and hospitals. Estimates of the prevalence of infection are as high as 20-25% in children younger than 3 years.

Symptoms of infection

Some people may carry giardia parasites without experiencing any symptoms. Symptoms generally appear one or two weeks after exposure.

Diarrhea is the most common symptom of infection. Symptoms and signs of infection do not begin for at least seven days after infection. But it can occur after three weeks or more.

Common symptoms include the following

·        Exhaustion

·         Nausea

·         Diarrhea, greasy and foul-smelling stools

·         Anorexia

·         Vomiting

·         Bloating and abdominal cramps

·         Weight loss and loss of body fluids

·         Gases

·         Headache

·         Stomach ache

·         Difficulty absorbing important nutrients

·         Feeling upset and weak

 

It lasts from 2 to 4 weeks. In most patients, the disease self-limits. However, in many patients who are not treated, the infection can persist for months to years with persistent symptoms.

Some patients recover with or without treatment, but symptoms persist, possibly due to a condition referred to as post-infectious irritable bowel syndrome. The reason for persistent symptoms is unclear but may be due to bacterial overgrowth in the small intestine. Children with chronic infection may be affected by developmental problems.

 Diagnosis

It may be necessary to submit one or more stool samples for testing. This is the most common test for most cases, but in chronic cases and cases that do not respond to treatment, the doctor may also request an intestinal endoscopy. This procedure involves passing a flexible tube down the throat and into the small intestine. This will allow the digestive tract to be examined and a tissue sample taken.

The best single test for diagnosis is the stool antigen test. Antigen testing: a small sample of stool is tested for the presence of giardia proteins. Antigen testing will identify more than 90% of people with giardia infection.

Giardia infection can also be diagnosed by examining the stool under a microscope in search of the cystic phase or the mobile phase. However, it takes three stool samples to diagnose 90% of cases. Although three stool samples are needed, stool microscopy identifies other parasites in addition to giardia infection which can cause diarrheal disease. Therefore, stool microscopic examination has value beyond diagnosing giardiasis, as it can identify and diagnose other parasites as the cause of a patient's illness.

 

                           Appropriate treatment

In most cases, the disease eventually goes away on its own. Your doctor may prescribe medication if the infection is severe or long-lasting. Most doctors recommend treatment with antiparasitic medications, rather than leaving it to recover on its own. Some antibiotics are commonly used for treatment.

1. Metronidazole is an antibiotic that must be taken for five to seven days.
2. Tinidazole is as effective as metronidazole, and is often treated with a single dose.
3. Nitazoxanide is a popular choice for children because it is available in syrup form and only needs to be taken for three days.
4.  Paromomycin is less commonly used to cause birth defects than other antibiotics. This medication is given in three doses over 5 to 10 days. Pregnant women should wait until after giving birth before taking any medication to treat the infection.

Complications

The disease can lead to complications such as weight loss and dehydration resulting from diarrhea. The infection can also cause lactose intolerance in some people. Children under 5 years old are at risk of malnutrition, which can interfere with their physical and mental development, and malabsorption (not absorbing nutrients adequately from the intestine).

Complications of infection also include the following

·         Zinc deficiency in school children

·         Persistent gastrointestinal symptoms 

Protection

1. You can reduce your risk of infection by washing your hands well, especially if you work in places where parasites spread easily.
2. Drink only water that has been treated in existing treatment facilities.
3. If there is any doubt about the adequacy of water treatment, boil the water or filter it through a filter with a pore size of less than 1 micrometer, which excludes microorganisms.
4. Do not drink from freshwater streams or lakes without boiling or filtering the water.
5. Do not use ice or drink beverages made with tap water, which may be contaminated.
6. Do not brush your teeth with tap water, which may be contaminated.
7. Do not eat uncooked or unpeeled fruits or vegetables grown in conditions where parasite contamination may occur.
8. Wash hands before eating, changing diapers, using the bathroom, or touching pets.
9. When traveling to an area where giardiasis occurs, do not drink tap water unless it is boiled or treated or filtered. Bring bottled water with you when you go.

Patient education

Personal hygiene education to reduce person-to-person transmission in high-risk settings is helpful. Patients and individuals at risk should be instructed regarding appropriate hygiene methods, and signs/symptoms of infection. Emphasis should be placed on measures such as washing hands carefully after changing diapers. Health care workers should wash hands to reduce the spread of illness among children and staff.

Hikers and travelers to areas where the disease is endemic should be educated. Before drinking water, it must be disinfected by boiling or using halogen compounds (such as chlorine) or filtration devices.

References

-https://www.mayoclinic.org/diseases-conditions/giardia-infection/diagnosis-treatment/drc-20372790

-https://www.ncbi.nlm.nih.gov/pmc/articles/PMC88984/

-https://www.healthline.com/health/giardiasis

-https://www.ncbi.nlm.nih.gov/books/NBK513239/