Protozoan Diseases
Protozoa is a phylum or a grouping of phyla that consists of many unicellular eukaryotic organisms which belong to the kingdom Protista. Protozoa can be of several types such as amoebas, flagellates, ciliates, sporozoans, and lots more. Protozoal diseases are diseases that are caused by protozoal infections. Protozoans are responsible for various infections and diseases which affect different types of organisms including plants, animals, and some marine life. Protozoans also cause some deadly diseases in human beings. These organisms are mostly parasitic. They mostly thrive on the human host for their entire life cycle whereas some carry out the reproductive part in insects or other hosts.
Protozoal Infections
Protozoal infections have an enormous impact on the health economic and social sectors mostly in the tropical and subtropical regions. Protozoan parasites that are infectious to human beings pose a significant threat to health. These protozoal infections claim almost 1.1 million lives annually. The diseases caused by protozoa are not only limited to humans but also affect plants and other organisms. Some of the most prevalent and deadly protozoan diseases in humans include malaria, African Sleeping sickness, Chagas disease, amoebic dysentery, Leishmaniasis, Toxoplasmosis, Giardiasis, and Cryptosporidiosis. The burden of human protozoan infections has been magnified by the lack of licensed and effective vaccines for some of the diseases these parasitic protozoans cause.
Protozoan Diseases in Humans
Malaria is caused by a single-celled eukaryotic microorganism called protozoa. Specifically, the parasitic Plasmodium genus is responsible for this disease. Mainly Plasmodium falciparum and Plasmodium vivax are responsible for malaria in humans out of the six Plasmodium species. Malaria leads to significant morbidity and economic downfall. Pregnant women, children, and old-aged people are more prone to malaria. The symptoms of malaria include fever and flu-like sickness accompanied by shaking chills, muscle pain, headache, and tiredness. Nausea, vomiting, and diarrhoea may also occur alongside. Malaria may also cause anaemia and jaundice because of the heavy loss in the RBC count. The patient should be treated with proper antimalarial drugs such as Chloroquine, Doxycycline, and lots more.
African sleeping sickness is the other name of African trypanosomiasis. This disease is caused by the parasitic protozoan of the Trypanosoma genus. It has two forms namely West African and East African trypanosomiasis. These protozoal infectious diseases are caused by Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Trypanosoma brucei gambiense accounts for about 95% of the cases. This parasitic protozoan causes a chronic infection which may emerge as a severe disease years later. Its symptoms include fever clubbed together with severe headaches, irritability, and extreme fatigue. Swollen lymph nodes and aching muscles and joints are also some of the common symptoms. Some typical neurological problems may occur if the disease has spread into the central nervous system.
Chagas disease is also known as American trypanosomiasis. It is an emerging health concern in Latin America. It is caused by infection with Trypanosoma cruzi. Leishmaniasis is a group of complex diseases caused by different species of the Leishmania genus. There are different clinical forms of Leishmaniasis such as visceral leishmaniasis (VL), cutaneous leishmaniasis (CL), and mucocutaneous leishmaniasis (MCL). Giardiasis is a disease caused by a flagellated protozoa named Giardia. Toxoplasma gondii causes a protozoan infectious disease known as toxoplasmosis. It has world-wide epidemiology. Toxoplasmosis infects about 25-30% of the world population.
Did You Know?
“Protozoa” means “first animals” in Greek.
Ford and Dutton detected Trypanosoma as the cause of Gambian fever which later turned into African Sleeping sickness in 1992.
The transmigration of Entamoeba histolytica remains for about 30-40 years in human beings. This protozoan parasite can invade the intestinal mucosa and spread to other organs like the liver, etc.
FAQs on Protozoal Disease
1. What exactly is a protozoa?
A protozoa is a single-celled eukaryotic organism belonging to the Kingdom Protista. While many protozoa are free-living and harmless, a significant number are parasitic, meaning they live in or on another organism (the host) and cause harm. These parasitic protozoa are responsible for causing various diseases in humans and animals.
2. What are protozoal diseases?
Protozoal diseases are illnesses caused by infections with parasitic protozoa. These microscopic organisms can be transmitted through various means, including contaminated food and water, insect vectors, or direct contact. Once inside a host, they multiply and disrupt normal bodily functions, leading to a wide range of symptoms.
3. What are the key protozoal diseases mentioned in the CBSE Class 12 syllabus?
The CBSE Class 12 syllabus, under the chapter 'Human Health and Diseases', primarily focuses on two major protozoal diseases:
- Malaria: Caused by the protozoan Plasmodium (e.g., P. vivax, P. falciparum) and transmitted by the female Anopheles mosquito.
- Amoebiasis (Amoebic Dysentery): Caused by Entamoeba histolytica, which is typically transmitted through contaminated food or water.
4. How does the Plasmodium parasite cause the recurring fever and chills typical of malaria?
The classic symptoms of malaria are directly linked to the parasite's life cycle in human red blood cells (RBCs). After an initial multiplication phase in the liver, the parasites invade RBCs. Inside the RBCs, they multiply asexually, eventually causing the blood cell to rupture. This rupture releases a toxic substance called haemozoin, along with new parasites that infect other RBCs. The release of haemozoin triggers the characteristic high fever and shaking chills. Since this happens in synchronized cycles (every 48 to 72 hours, depending on the Plasmodium species), the fever and chills are recurrent.
5. What is the main difference between amoebiasis and amoebic dysentery?
Amoebiasis is the infection caused by the protozoan Entamoeba histolytica. A person can be an asymptomatic carrier. Amoebic dysentery is the severe, symptomatic form of this infection. While basic amoebiasis might cause mild diarrhoea and cramps, amoebic dysentery is characterised by more severe symptoms, including abdominal pain, frequent stools containing blood and mucus, and fever, indicating significant invasion of the intestinal lining.
6. How do protozoa generally cause disease in the human body?
Protozoa cause disease by exploiting the host's body to complete their life cycle. The primary mechanisms include:
- Tissue Destruction: Parasites like Entamoeba histolytica directly invade and destroy host tissues, such as the intestinal wall, causing ulcers and bleeding.
- Cellular Invasion: Parasites like Plasmodium invade host cells (liver cells and RBCs), multiply within them, and then destroy them, releasing toxins.
- Toxin Production: The metabolic by-products of protozoa, like the haemozoin in malaria, can be toxic to the host and trigger strong immune responses like fever.
- Nutrient Depletion: By residing in the host's intestine or bloodstream, they consume essential nutrients, leading to weakness and malnutrition.
7. Why are vector-borne protozoal diseases like malaria so difficult to control in certain regions?
Controlling vector-borne diseases like malaria is challenging due to a combination of biological and environmental factors. The mosquito vector (Anopheles) thrives in warm, humid climates with standing water, which are common in tropical and subtropical regions. Eradication is difficult because of the vector's ability to develop insecticide resistance. Furthermore, the Plasmodium parasite itself can develop drug resistance, making treatments less effective over time. Socio-economic factors, such as limited access to healthcare, bed nets, and sanitation, also contribute to the persistent spread of the disease.
8. How are protozoal infections typically diagnosed and treated?
Diagnosis usually relies on identifying the parasite or its life stages in the host. For example, malaria is diagnosed by microscopic examination of a blood smear, while amoebiasis is diagnosed by examining a stool sample for the presence of Entamoeba histolytica cysts or trophozoites. Treatment involves specific antiprotozoal drugs that target the parasite's metabolism or life cycle. For instance, malaria is treated with antimalarial drugs like chloroquine, while amoebiasis is treated with drugs like metronidazole.
9. What are the most effective ways to prevent common protozoal diseases?
Prevention strategies target the mode of transmission of the specific disease. Key measures include:
- Vector Control: For diseases like malaria, preventing mosquito bites is crucial. This is done by using insecticide-treated mosquito nets, wearing protective clothing, and eliminating mosquito breeding sites (stagnant water).
- Improving Sanitation and Hygiene: For diseases like amoebiasis and giardiasis, prevention focuses on ensuring access to clean, safe drinking water and proper sewage disposal.
- Personal Hygiene: Simple practices like washing hands with soap before eating and after using the toilet are highly effective in preventing faecal-oral transmission.
