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PARASITISM AND PARASITOLOGY
Definition of Terms: Parasitology – is the study of parasites and their host. Parasitism - relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism. Types of Parasites:
- Ectoparasites - are organisms that live on the skin of a host, from which they derive their sustenance. Ex: head lice
- Endoparasites - are parasites that lives inside its host. Ex: tapeworm
- Facultative Parasites – are organisms that may resort to parasitic activity,but does not absolutely rely on any host for completion of its life cycle. Ex: Fungi of Genus Armillaria and nematode species Strongy loides stercoralis which is a type of roundworm that can cause the segmented worms that live in the intestines ofsome animals. Eating undercooked meat from infected animals is the main cause of tapeworm infection in people. PROTOZOA - is an informal term for a group of single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris. Ex. Entamoeba histolytica Protozoan Infection of the SKIN LEISHMANIASIS - a parasitic disease that is found in parts of the tropics, subtropics, and southern Europe caused by infection with Leishmania parasites,which are spread by the bite of phlebotomine sand flies. Three forms of Leishmaniasis
- Cutaneous Leishmaniasis causes painless skin ulcers. It‘s the most common form of leishmaniasis. Treatment may not always be necessary depending on the person, but it can speed healing and prevent complications.
- Mucocutaneous Leishmaniasis is a rare form caused by the cutaneous form of the parasite and can occur several months after skin ulcers heal. The parasites spread to your nose, throat, and mouth. This can lead to partial or complete destruction of the mucous membranes in those areas. This is a more serious form and doesn‘t heal on its own and always requires treatment.
Signs & Symptoms : ∙ Primarily ulcers in the mouth and nose or on the lips. ∙ runny or stuffy nose ∙ nosebleeds ∙ difficulty breathing
- Visceral Leishmaniasis is sometimes known as Systemic Leishmaniasis or Kala azar. It usually occurs 2-8 months after being bitten by a sand fly. It damages internal organs, such as your spleen and liver. It also affects your bone marrow, as well as your immune system through damage to these organs. The condition is almost always fatal if not treated. Signs & Symptoms: ∙ Weakness ∙ Fever that lasts for weeks or months ∙ Enlarged spleen ∙ Enlarged liver ∙ Decreased production of blood cells ∙ Bleeding ∙ Swollen lymph nodes Diagnosis Biopsy or blood sample examination Treatment Antiparasitic drugs Amphotericin B (Ambisome) Paromomycin
Risk Factors a. Infants born to mother with toxoplasmosis b. with weak immune system Diagnosis Blood Test Protozoal Infection of the GASTROINTESTINAL BALANTIDIASIS – is a large intestinal infection with Balantidium Coli , which is a ciliated protozoan. Signs and Symptoms :
- Dysentery
- Rarely intestinal bleeding, intestinal perforation, or extra intestinal involvement
- Bloody diarrhea
- Abnormally high temperature
- Constipation
- Vomiting
- Anorexia
- Weight loss
- Headache
- Colitis Diagnosis:
- Detection of trophozoites or cysts in stool samples from symptomatic patients or in tissue collected during endoscopy
- Colonoscopy or sigmoidoscopy to obtain biopsy from the large intestines which may provide evidence for the presence of trophozoites. Treatment: Tetracycline, Metronidazole or Iodoquinol CRYPTOSPORIDIOSIS - is a diarrheal disease that is spread through contact with the stool of an infected person or animal with the protozoan Cryptosporidium. Mode of Transmission
∙ Ingestion of fecally contaminated food or water (often water in public and residential pools, hot tubs, water parks, lakes, or streams) ∙ Direct person to person contact ∙ Zoonotic spread Signs and Symptoms
- Profuse watery diarrhea
- Abdominal cramping
- Nausea
- Anorexia
- Fever
- Malaise Diagnosis: ∙ Enzyme immunoassay for fecal antigen or molecular probes for parasiteDNA ∙ Microscopic examination of stool (special techniques required) Treatment Cryptosporidiosis is self-limited. For severe/persistent infections,nitazoxanide is used GIARDIASIS - an infection in your small intestine. It's caused by a microscopic parasite called Giardia lamblia. Giardiasis spreads through contact with infected people. And you can get giardiasis by eating contaminated food or drinking contaminated water. Signs & Symptoms
- fatigue
- nausea
- diarrhea or greasy stools
- loss of appetite
- vomiting
- bloating and abdominal cramps
- weight loss
- excessive gas
- headaches
- abdominal pain Diagnosis ∙ Stool Exam
- Cell cultures
- Antigen tests (antibodies bind if the Trichomonas parasite is present,which causes a color change)
- Tests that look for Trichomonas DNA
- Examination of samples of vaginal fluid, urethral discharge, or urine under a microscope Treatment Metronidazole (Flagyl) or tinidazole (Tindamax) Protozoal Infections of the CIRCULATORY SYSTEM A. AFRICAN TRYPANOSOMIASIS - also known as African sleeping sickness or simply sleeping sickness, is an insect-borne (tsetse fly) parasitic infection of humans and other animals. It is caused by the species Trypanosoma brucei. Humans are infected by two types, Trypanosoma brucei gambiense (TbG) and Trypanosoma brucei rhodesiense (TbR). Signs & Symptoms
- Skin lesions
- Intermittent fever
- Headache
- Transient edema
- Generalized lymphadenopathy Diagnosis
- Identification of organism in blood
- Lymph node aspirate
- Cerebrospinal fluid test Treatment ∙ Without CNS involvement, pentamidine for T.b.gambiense; suramin for T. b. rhodesiense ∙ With CNS involvement, eflornithine or melarsoprol for T. b.gambiense; melarsoprol for T. b. rhodesiense
CHAGA’S DISEASE (American trypanosomiasis) - is a potentially life-threatening disease caused by the parasite Trypanosoma cruzi. It is most commonly transmitted by biting insects known as ‗kissing bugs‘ that are infected with the parasite. As people typically show no symptoms for many years, most are unaware they have Chagas. Mode of Transmission ∙ Mother-to-baby (congenital), ∙ Contaminated blood products (transfusions), ∙ An organ transplanted from an infected donor, ∙ Laboratory accident (rare), or ∙ Contaminated food or drink (rare) Signs & Symptoms ∙ Fever ∙ Swelling around the site of inoculation ∙ May result in severe inflammation of the heart muscle or the brain and lining around the brain ∙ Complications of chronic Chagas disease ∙ Heart rhythm abnormalities that can cause sudden death; ∙ A dilated heart that doesn‘t pump blood well; and ∙ A dilated esophagus or colon, leading to difficulties with eating or passing stool. Diagnosis Generally made by testing for parasite specific antibodies Treatment Benznidazole or Nifurtimox BABESIOSIS - is a rare and life-threatening infection of the red blood cells that'susually spread by ticks. It's caused by tiny parasites called Babesia. The kind thatmost often affects humans is called Babesiamicroti. They enter your bloodstream when you're bitten by an infected deer tick.
∙ General feeling of discomfort ∙ Headache ∙ Nausea and vomiting ∙ Diarrhea ∙ Abdominal pain ∙ Muscle or joint pain ∙ Fatigue ∙ Rapid breathing ∙ Rapid heart rate ∙ Cough Complications: ∙ Cerebral Malaria ∙ Organ failure especially kidneys, liver and spleen ∙ Anemia ∙ Low blood sugar ∙ Pulmonary edema Diagnosis : Blood tests for presence of parasites Treatment ∙ Chloroquine phosphate ∙ Artemisinin-based combination therapies (ACTs) for chloroquine-resistant malaria ∙ Atovaquone-proguanil (Malarone) ∙ Quinine sulfate (Qualaquin) with doxycycline (Oracea, Vibramycin,others) ∙ Primaquine phosphate Protozoal Infection of the CNS PRIMARY AMEBIC MENINGOENCEPHALITIS (Naegleriasis) - is an almost invariably fatal infection of the brain by the free-living unicellular eukaryote Naegleria fowleri (―brain-eating amoebaǁ). Signs & Symptoms Stage 1
- Severe frontal headache
- Fever
- Nausea
- Vomiting Stage 2
- Stiff neck
- Seizures
- Altered mental status
- Hallucinations
- Coma Diagnosis : ∙ Naegleria fowleri organisms in cerebrospinal fluid (CSF), biopsy,or tissue specimens, or ∙ Naegleria fowleri nucleicacid in CSF, biopsy, or tissuespecimens, or ∙ Naegleria fowleri antigen in CSF, biopsy, or tissue specimens Treatment Miltefosine has shown ameba-killing activity against free-livingamebae, including Naegleria fowleri, in the laboratory HELMINTHS - are parasitic worms that feed on a living host to gain nourishment and protection, while causing poor nutrient absorption, weaknessand disease in the host. These worms and larvae live in the small bowel and are referred to as intestinal parasites. Major Types
- Roundworms - are parasites that live in your intestine.
- Flatworm, also called platyhelminth, any of the phylum Platyhelminthes, a group of soft-bodied, usually much flattened invertebrates. A number of flatworm species are free-living, but about 80 percent of all flatworms are parasitic—i.e., living on or in another organism and securing nourishment from it.
∙ Inflammation caused by larvae that die in the eye results initially in reversible lesions on the cornea that without treatment progress to permanent clouding of the cornea, resulting in blindness. Diagnosis ∙ Biopsy of the skin is done to identify larvae, which emerge from the skin snip ∙ Slit-lamp examination of the anterior part of the eye where the larvae causes the lesions. ∙ Antibody tests Treatment ∙ Ivermectin kills the larvae ∙ Doxycycline that kills the adult worms by killing the Wolbachia bacteria on which the adult worms depend in order to survive.
2. Muscles and Subcutaneous Tissue TRICHINOSIS (Trichinellosis) - is a parasitic disease caused by roundworms of the Trichinella type which occur when people eat undercooked meat. Signs and Symptoms: Initial : ∙ Diarrhea ∙ Abdominal pain ∙ Fatigue ∙ Nausea and vomiting Late : ∙ High fever ∙ Muscle pain and tenderness ∙ Swelling of the eyelids or face ∙ Weakness ∙ Headache ∙ Sensitivity to light ∙ Pink eye (conjunctivitis) Risk Factors ∙ Improper food preparation. Trichinosis infects humans when they eat undercooked infected meat, such as pork, bear or walrus, or other meat contaminated by grinders or other equipment. ∙ Rural areas. Trichinosis is more common in rural areas. In the United States, higher rates of infection are found in hog-raising regions. ∙ Consumption of wild or noncommercial meats.
Complications ∙ Myocarditis - an inflammation of the myocardium, the thick muscularlayer of your heart wall ∙ Encephalitis - an inflammation of your brain ∙ Meningitis — an inflammation of the membranes (meninges) andcerebrospinal fluid surrounding your brain and spinal cord ∙ Pneumonia — an inflammation of your lungsDiagnosis ∙ Stool sample tests ∙ Physical Exam Treatment : ∙ Anti-parasitic medication is the first line of treatment for trichinosis ∙ Pain reliever ∙ Corticosteroids DRACUNCULIASIS (Guinea-worm disease) - is a parasitic infection by theGuinea worm. A person becomes infected when they drink water that contains water fleas infected with guinea worm larvae. Signs & Symptoms
- Itching and burning pain at the inflamed skin lesion
- Debilitating arthritis
- Urticaria
- Erythema
- Vomiting Diagnosis Clinical Evaluation including ulcer inspection Treatment a. Manual or surgical removal of worm b. Metronidazole can be given but not very effective
- Eyes LOIASIS – known as African eye worm by most people, is caused by the parasitic worm Loa loa. It is passed on to humans through the repeated bites of deer flies (also known as mango flies or mangrove flies) of the genus Chrysops.
∙ Itching and hives ∙ Cough ∙ Shortness of breath ∙ Chest pain ∙ Belly pain ∙ Nausea ∙ Vomiting ∙ Bloody diarrhea ∙ Lumps or bumps on the skin of the belly or legs that come and go over time Diagnosis ∙ Blood tests. A high number of a specific type of white blood cells can suggest parasitic infection. Antibodies against flukes may be present in the blood ∙ Sputum microscopy. Fluke eggs may be detected during examination of coughed-up sputum under a microscope. ∙ Chest X-ray. Nodules (spots) in the lungs, hollowed-out areas (cysts or cavities), or fluid around the lungs (pleural effusions) may be present. ∙ CT scan. High-resolution images of the lungs may show more detailed information than a chest X-ray. Also, CT of the head or abdomen may be abnormal if paragonimiasis involves the brain or liver. ∙ MRI. Very high-definition images of the brain can identify cysts or brain swelling caused by paragonimiasis. ∙ Bronchoscopy. A doctor can put an endoscope (flexible tube with a camera on its tip) through the nose or mouth into the lungs. Flukes or their eggs are collected from lung fluid samples. The flukes or eggs may be seen under a microscope. ∙ Thoracentesis. A doctor puts a needle through the chest wall to sample fluid around the lungs (pleural effusion). ∙ Stool studies. Fluke eggs may be seen in stool samples when examined under a microscope. Treatment ∙ Praziquantel (Biltricide) and Triclabendazole (Egaten) are approved for treatment
References: Bauman, Robert W. (2019), Microbiology with Diseases by Body System, 4th^ Edition, PearsonEducation Hogg, Stuart (2013), Essential Microbiology, 2nd^ edition, John Wiley and Sons Microbiology for Nursing Students by Jzohn Enzo Kreislur First Edition 2011
