Protozoan Disease: Definition, Symptoms, Examples, Treatment

What are Protozoa Diseases?

Protozoa diseases are infections caused by protozoa. Protozoa are tiny, unicellular eukaryotic cells that have the capability of self-propelled movement. They can be parasitic or free-living based on how they move. Their mode of nutrition is heterotrophic, i.e. they feed on organic matter or other living organisms as parasites.

A disease caused by protozoa happens when these parasites enter the body. They move on their own and feed on organic matter. Some protozoa live freely, while others survive as parasites inside humans, animals, or plants. Protozoa diseases spread through water, food, or insect bites.

Differences Between Protozoa and Other Microorganisms

Protozoa are single-celled organisms that differ from other microbes like bacteria and viruses in structure, function, and life cycle. They often live as parasites and have complex survival strategies. Understanding these differences helps in identifying their role in disease. Some major differences between protozoa, bacteria and viruses are discussed below:

Protozoan Diseases and Their Causative Agents

Protozoan diseases are caused by different protozoa and spread through water, food, or insect bites. These diseases are common in areas with poor hygiene and sanitation. It is important for both personal and public health. The following table enumerates a few prevalent protozoan illnesses, along with information on how they are caused and spread:

Some Common Protozoan Diseases in Humans

Protozoan diseases are caused by parasites that affect health and organs in several ways. Some of the common examples of diseases caused by protozoa, along with their symptoms and causative agents, are discussed below:

Malaria

It's caused by a plasmodium species and mainly by P. falciparum, P. vivax, P. ovale, and P. malariae. This is spread through bites of infected female Anopheles Mosquitoes. This is acquired by a parasite from the person who is infected by this mosquito. To prevent malaria, you can use bed nets, indoor spraying and prophylactic medications in case of seriousness.

Amoebiasis

This protozoan disease is caused by Entamoeba histolytica. This disease is common in tropical areas and is transmitted via contaminated food or water containing protozoan cysts. Symptoms of this protozoan causative agent may vary from mild diarrhoea to severe dysentery and may lead to liver abscesses. Preventive steps against this protozoan disease include hand hygiene, drinking safe water, and ensuring proper sanitation.

Trypanosomiasis (Sleeping Sickness)

This protozoan disease is caused by Trypanosoma species, with T. brucei. This is responsible for causing African Trypanosomiasis and T. cruzi, causing Chagas disease in South America. African Trypanosomiasis spreads through infected tsetse flies, while Chagas disease is transmitted by triatomine bugs ("kissing bugs"), through contaminated food, or blood transfusions. Symptoms of this disease vary from fever and headaches to severe neurological or cardiac issues. For preventive measures, you can include using insect repellents, improving living conditions, and avoiding contact with street vectors

Protozoan Diseases in Animals and Plants

Protozoa diseases do not only affect humans. They also harm animals and plants. A disease caused by protozoa can reduce health, growth, and productivity.

Protozoa Diseases in Animals

1. Babesiosis: This is a disease caused by ticks which are infected with Babesia. It causes fever and anaemia in animals like dogs and cattle.

2. Coccidiosis: Livestock and poultry are affected by this illness when they ingest Eimeria species. As a result of this parasite, there will be diarrhoea and damage in the small intestine.

3. Theileriosis: Theileria species cause the infection in cattle, which is spread by ticks. Anaemia, fever, and enlargement of lymph nodes of the lymphatic system.

Protozoa Diseases in Plants

1. Clubroot Disease: It is most commonly caused by Plasmodiophora brassicae. It promotes large root formation and stunted plant growth in cruciferous vegetables.

2. Phytomonas: A plant disease that reduces plant health and yields in crops like oil palm and coconut.

Transmission of Protozoa Diseases

Protozoa infect the host's body by entering through the digestive tract, skin, or blood. Once inside, they multiply and damage tissues or organs. Some may avoid the immune system, making infections worse. Each species uses a unique mechanism to cause disease. Protozoa may be the causative agents of disease via numerous different mechanisms:

• Invasion: Protozoa go into host cells and tissues, in which they propagate and therefore disrupt normal body activities.

• Immunoevasion: Protozoa have techniques (antigenic variation) permitting them to hide from recognition by the host's immune system.

• Tissue destruction: Protozoa generate damage in 2 ways: direct cell death of host tissues or induction of inflammatory reactions.

Person-to-Person Transmission

• Direct Contact: Trichomoniasis is transmitted through intimate contact.

Indirect Transmission

• Contaminated Food and Water: Protozoa such as Entamoeba histolytica and Giardia lamblia are transferred from an infected person through ingestion of contaminated food and or water.

• Fomites: Some protozoa can survive on surfaces and be transmitted through contact with contaminated objects.

Vector-Borne Transmission

• Insects: Protozoa like Plasmodium spp. (malaria) and Trypanosoma spp. (Chagas disease and African sleeping sickness) are transmitted by insect vectors like mosquitoes and tsetse flies.

Signs and Symptoms of Protozoan Diseases

Protozoa diseases show different symptoms depending on the parasite and the organ affected. A disease caused by protozoa may cause mild illness or severe damage. Early detection is important to reduce risks.

General Symptoms

• Fever is common in diseases such as malaria.

• Diarrhoea may be seen in diseases such as amoebic dysentery and giardiasis.

• Fatigue

• Abdominal pain is common in infections.

Specific Symptoms

• Malaria: Fever and shaking chills, anaemia, fatigue, and an enlarged spleen.

• Amoebiasis: diarrhoea with mucus and blood, stomach pain, and weight loss.

• Giardiasis: Watery faeces, gas, and malnutrition.

Risk Factors of Protozoa Disease

Acquiring protozoan infections is more likely if you have:

• Poor sanitation

• Drinking infected water

• Access to medical care

• Weakened immune systems

• Travel to places with contagious diseases

Diagnosis of Protozoa Diseases

Diagnosis of protozoa diseases usually involves lab tests like blood smear, stool test, or antigen detection. Identifying the parasite early helps in better treatment. Microscopes and modern diagnostic tools are used. Accurate diagnosis is important for controlling the disease. Diagnosing disease caused by protozoa typically involves using:

• Microscopy: Microscopy of stool, blood, or tissue specimens to find the protozoan.

• Serological Testing: Identification of specific antigens or antibodies in the blood.

• Molecular Methods: For detecting protozoan genetic material, such as PCR and other DNA-based methods

Treatment of Disease Caused by Protozoa

Protozoa diseases are treated using antiparasitic drugs. The type of medicine depends on the species of protozoa involved. In severe cases, hospital care may be needed. Timely treatment can prevent serious complications. Treating protozoan infection includes:

• Maintain fluids and nutrients, and treat the symptoms with supportive care.

• Antiparasitic medications are used to treat amoebic dysentery and chloroquine for malaria.

• In extreme cases, removing affected body parts could result in a surgical operation.

Prevention and Control of Protozoa Diseases

Protozoa diseases are harder to treat than bacterial or viral infections. A disease caused by protozoa is complex because these parasites can hide from the immune system. It is difficult to develop a vaccination for protozoan diseases. As a result, preventing protozoan infection is more convenient than treating it. The strategies for preventing protozoan infection include:

• Sanitation: Maintaining clean water and food practices.

• Vector Control: Reducing insect vectors with the use of insecticides, bed nets, and repellents

• Personal Protection: Avoid infected water and food, have safe sex, and wear protective clothing.

Complications of Disease Caused by Protozoa

If protozoa diseases are left untreated, they can lead to serious health problems. A disease caused by protozoa may damage organs, cause long-lasting weakness, or even lead to death. Some protozoa diseases may return or become chronic. Prevention and early treatment are key to avoiding such outcomes.

Immediate Effects

• Significant Anaemia: Especially in malaria, it leads to fatigue and pallor.

• Organ Damage: Protozoa, such as species in Malaria, may result in impaired organ function, including liver and splenic damage.

• Shock: Severe infections can result in a systemic inflammatory response and shock.

Chronic Effects

• Chronic disease syndromes: Prolonged symptoms in the form of chronic fatigue or gastrointestinal morbidity.

• Neurological Failure: Long-term effects that can develop following cerebral malaria infections or be associated with immunocompromised patients.

MCQs on Protozoan Diseases

Q1. Which one of the following diseases is caused by a protozoan?

1. Malaria

2. Amoebiasis

3. Both (a) and (b)

4. All of the above

Correct answer: 4) All of the above

Explanation:

As we have already studied in Protozoan Disease -

Malaria and Amoebiasis is a type of protozoan diseases. Malaria is caused by a parasite, Plasmodium and transmitted into the human body by the bite of a female mosquito called Anopheles. Its symptoms include malarial fever, restlessness, less appetite and muscular pain. Amoebiasis is caused by Entamoeba histolytica. It can be caused by the faecal-oral route or sexual transmission. Its symptoms include stools with blood and abdominal pain

Hence, the correct option is 4) All of the above.

Q2. Which one of the following cannot be used for the preparation of vaccines against plague?

1. Formalin-inactivated suspensions of virulent bacteria

2. Avirulent live bacteria

3. Synthetic capsular polysaccharide material

4. Heat-killed suspensions of virulent bacteria

Correct answer: 3) Synthetic capsular polysaccharide material

Explanation:

Plague is an infectious disease caused by the bacterium Yersinia pestis. Inactivated bacteria have been used since 1890 but have been less effective against pneumonic plague, so live attenuated and recombinant protein vaccines have recently been developed to prevent the disease. Synthetic capsular polysaccharide vaccine for the treatment of pneumonia and meningitis. Therefore, synthetic capsular polysaccharide materials cannot be used in the preparation of vaccines against harmful organisms.

Hence, the correct answer is option 3) synthetic capsular polysaccharide material.

Q3. Which one of the following diseases is not caused due to contamination of water?

1. Hepatitis-B

2. Jaundice

3. Cholera

4. Typhoid

Correct answer: 1) Hepatitis-B

Explanation:

Hepatitis B is spread through body fluids like blood, sperm, sputum, mucus, and vaginal fluids. It can be transmitted via direct contact with infected fluids, such as through unprotected sexual contact, sharing needles, or from an infected mother to her baby during childbirth. The virus can also be transmitted through exposure to contaminated blood products or medical equipment that hasn't been properly sterilised. In some cases, the virus can be spread through sharing personal items, like razors or toothbrushes, that may have come in contact with infected blood. Hepatitis B can lead to chronic liver disease, liver cancer, or cirrhosis if left untreated.

Hence, the correct answer is option 1) Hepatitis-B.