Please enable JavaScript.
Coggle requires JavaScript to display documents.
Case 1: Exotic Pathogens, Intestinal obstruction secondary to Ascaris…
Case 1: Exotic Pathogens
ParasiteDefine ParasitesParasites are eukaryotes that live in/on the host, derive nutrition from the host at the expense of the host and are different species from the host. Parasites are NOT viruses, bacteria, fungi or algaeClassification of ParasitesBriefly classify ParasitesParasites can be Endoparasites or Ectoparasites
- Endoparasites
- Endoparasites live in the host
- Endoparasites can be:
- Unicellular Protozoa
- Multicellular Helminths (Worm)
- Ectoparasites
- Ectoparasites live on the host
- Ectoparasites are ticks, fleas, lice and mites
Classification of ProtozoaExplain how Protozoa are classified
- Protozoa are unicellular endoparasites
- Protozoa are classified according to their mode of locomotion.
- Amoeboids form Pseudopodia
- Ciliates have short-hairy processes called Cilia
- Sporozoa are non-motile
- Flagellates have long whip-like structure called flagella
Protozoa (Unicellular)Give an example of each type of Protozoa
- Amoeboid
- Example of a Parasitic Amoeba: Entamoeba
- Ciliates
- Example of a Parasitic Ciliate: Balantidium
- Sporozoa
- Example of a Parasitic Sporozoa: Plasmodium which causes malaria
- Flagellates
- Example of a Flagellate: Giardia
Multicellular HelminthsMulticellular Helminths are endoparasitesClassification of Helminths (Worms)Classify the Helminths
- Nematodes (round worms)
- Trematodes (flat worms)
- Cestodes (Tape Worm)
HelminthsOutline Nematodes
- Nematodes are cylindrical worms with a body cavity and a digestive tract
- Individual nematodes are either male or female
- And reside in the Intestines or Body tissues
- Intestinal Nematodes: Enterobius (pinworm), Ascaris (round worm)
- Body tissue Nematodes: Onchocera
Outline Trematodes
- Trematodes are also known as flukes
- Trematodes have unsegmented plates, no body cavity and have incomplete digestive tracts
- Trematodes are Hermaphrodites except Schistosoma
Outline Cestodes
- Cestodes or tapeworms have Segmented plates
- No body cavity, no digestive tract
- Cestodes are Hermaphrodites
- Eg: Taenia
Protozoa: MalariaWhat is Malaria ?
- Malaria is a parasitic disease
- Malaria is caused by the parasitic species: Plasmodium species
- Examples of Plasmodium species
- Plasmodium falciparum
- Plasmodium vivax
- Plasmodium ovale, malariae. knolwesi
- Malaria is transmitted to humans by the Anopheles mosquito
Aedes mosquito can transmit dengue fever and Zika virusWhich areas does malaria commonly occur in ?
- Tropical and Subtropical Regions (Limpopo, Mpumalanga and KZN), airport or aeroplanes
What is the Malaria vaccine ?
Malaria Life CycleDescribe the Malaria Life Cycle
- Malaria Lifecyle is initiated by injection of the sporozoites in the saliva of the mosquito into human blood
- Sporozoites then infect the hepatocytes via the binding of Malaria Circuspozite Protein to the Hepatocyte Thrombospondin Receptor
- Subsequently, there is an incubation period with asymptomatic multiplication in Hepatocytes
- Hepatocytes mature into Schizonts that eventually rupture and release Merozoites into the blood
- Merozoites the infect the Red Blood Cells and become Trophozoites
- Trophozoites can either undergo repeated asexual multiplications and mature into Schizonts or develop into male and female gametes
- Schizonts rupture and release merozoites into the blood
- Gametes undergo sexual replication inside mosquito gut to develop Sporozoites
List the consequences of Malaria
- Merozoite release cause Haemolysis
- Haemolysis results in:
- Anaemia
- Jaundice
- Hematuria which results in renal failure
- Merozoites also cause Malaria toxins to be released which elevates levels of the Tumour necrosis Factor leading to high fever
Fever Terminology
- Chills are feelings of cold
- Rigors is shivering
- High grade fever is when the temperature is 39-41.5°C
- Diaphoresis is sweating
Fever usually occurs in the sequence of chills, rigors, high grade fever and diaphoresis and then the sweating subsides
- Fever in Plasmodium falciparum is irregular
- Plasmodium ovale, vivax and quartan have a regular pattern of fever which occurs every third day
- Plasmodium malariae fever occurs every fourth day
List the other manifestations of Malaria
- Immune activation, congestion and phagocytosis of haemolysis red cells result in Splenomegaly and Hepatomegaly
- Repeated attacks result in massive splenomegaly also known as tropical splenomegaly syndrome
MalariaOutline the complications of Malaria
- Cerebral malaria caused by Plasmodium falciparum.
- Plasmodium falciparum causes red blood cells to clump and stick to endothelium especially in the brain.
- Pulmonary oedema due to renal failure
- Shock and DIC due to Hypoxia, Hypovolaemia, Hypoglycaemia, Acidosis and Sepsis
- Burkitt Lymphoma due to chronic immune activation and EBV infection
- Increased miscarriages, maternal death and small fetuses in Pregnancy.
Protozoa: AmoebiasisWhat is Amoebiasis ?
- Amoebiasis is a parasitic infection caused by Entamoeba Histolytica
- As the name suggests the Amoeba lives in the gut and causes the lysis of tissue
- It is transmitted faecal orally - not washing hands after making contact with faeces.
- Most infection are asymptomatic, and 10% are invasive Proctocolitis
- Proctocolitis is the inflammation of the rectum and colon
- Invasive amoeba digests tissue and causes ulceration with pus formation and bleeding
- Patient present with bloody, painful diarrhoea known as Dysentery
- Additionally, the Amoeba can spread to the liver via mesenteric and portal veins resulting in Liver Abscess
ColonDescribe the development of the Invasive Amoeba(Amoebiasis) in the Colon
- In the environment the Amoeba exist as a cyst
- Once ingested the Amoeba excyst and develops into Trophozoites
- These trophozoites feed on red blood cell by the process of Erythrophagocytosis and secrete the enzyme, Cysteine prosteinase
- Cysteine prosteinase erodes on the bowel and interferes on Neutrophil function
- Resulting in flask shaped ulcers that perforate
Liver Describe the development of the Invasive Amoeba (Amoebiasis) in the Liver
- If the Amoeba gets into the bloodstream it is spread Haematogenously into the Liver
- Resulting in Abscess formation
- Liver abscess contains red-brown "anchovy paste' like pus due to paucity of neutrophils that are associated with Amoebic Function
- Pus contains necrotic hepatocytes, blood and fibrin exudate
SchistosomiasisWhat is Schistosomiasis ?Schistosomiasis is caused by a Helminth called SchistosomaDescribe Schistosoma ?
- Schistosoma lifecycle involves the fresh water snail as an intermediate host
- Once the Cercaria penetrate the human skin, Schistosoma larvae migrate to the lungs
- Mature in the Portal Veins
- Migrate to the Deep Veins:
- Schistosoma Haematobium migrate to the bladder
- Schistosoma mansoni migrates to the Mesenteric Veins
- Depending on the dominant organ of involvement the eggs are then excreted into the faeces or the urine.
- Schistosoma eggs can cause an inflammatory reaction and affects mainly the:
- Bladder
- Ureter
- Genital tract
- Liver
- GIT
- CNS
- Schistosoma mainly affects Limpopo,
Mpumalanga and KZN
Pathogenesis of Schistosoma: Host reaction to Schistosoma Eggs
- The adult flukes evades host immunity
- There is mucosal erosion as eggs are excreted
- Schistosoma eggs cause a chronic immune reaction characterized by:
- Acute Eosinophilic Inflammation
- Granuloma around the eggs
- With subsequent fibrosis resulting in organ dysfunction
Schistosoma HaematobiumDescribe the Host response to S. haematobium Eggs in the Bladder
- In the Bladder the eggs cause Cystitis with Haematuria and Inflammation
- Over time Progressive Bladder fibrosis and Calcification occurs
- Leading to Ureteric Obstruction/ Granulomatous inflammation
- And Bladder Squamous cell carcinoma
Schistosoma mansoniDescribe the Host response to S. mansoni Eggs in the Colon
- Eggs/ Ova in the Colon will cause Colitis with bloody diarrhoea
- Deposition of Ova/Eggs in the portal veins results in Granulomatous Inflammation of the small portal veins
Hepatosplenic SchistosomiasisList the results of Hepatosplenic Schistomiasis
- Splenomegaly
- Hepatomegaly
- Ascites
- Chronic portal tract fibrosis (not cirrhosis)
- Portal Hypertension
- Variceal Haemorrhage
Hydatid DiseaseWhat is Hydatid Disease ?Hydatid disease is caused by Echinococcus granulosusDescribe the development of Echinococcus granulosus into Hydatid Disease
- The adult host is the Dog where the worms reside in the gut and the parasite ova are deposited in the dog faeces
- Intermediate hosts are sheep, pigs and cattle
- Humans are accidental hosts that acquire Hydatid Disease by ingesting parasite ova
- Once ingested the ova hatch in the Duodenum and release Oncospheres
- Oncospheres are transported to the Liver via the Portal Veins
- In the liver and other organs the Oncospheres expand to form Hydatid Cysts
Hydatid Cysts Hydatid cysts are formed when Oncospheres expand in the liver and other organsOutline the structure of Hydatid Cysts
- Hydatid cysts have a soft, white laminated membrane with a germinal layer on the inside of the cyst
- Germinal layer forms a Daughter Cyst containing protoscoleces or Scolices (heads of future adult worms)
- There is a surrounding Fibrous Host Response
Describe the effect of the Hydatid Cyst in the various organs: Liver, Spleen, Bone, Brain and Any organ
- Liver: Liver Enlargement, Abdominal discomfort, Bile duct obstruction
- Bone: Fracture and Vertebral Collapse
- Brain: Cerebral Discomfort and Epilepsy
- Any organ: Resembles Cystic Tumours
- If Cyst ruptures Anaphylactic Shock occurs and then death
CysticercosisWhat is Cysticercosis ?
- Cysticercosis is caused by Cestodes: Taenia Solium and Taenia Saginata
Describe the development of Taenia Solium and Taenia Saginata into Cysticercosis
- Humans are definitive hosts of tapeworm: Taenia solium and Taenia saginata
- Pigs are intermediate hosts of Taenia Solium and Cattle are intermediate host of Taenia Saginata
- Humans acquire the adult worm infection if they ingest infected pork or beef
- Normally, tape worms remain asymptomatic in human gut.
- However, humans can become intermediate host of Taenia solium if the ova of the tapeworm are accidently ingested.
- Neurocysticercosis due to Taenia solium
Taenia solium: Cardiac cysticercosis
Ascariasis What is Ascariasis ?Ascariasis is caused by Nematodes (Round Worms) called Ascaris lumbricoidesDescribe the development of Ascaris lumbricoides in the Human host to Ascariasis
- Ascaris lumbricals are transmitted faecal orally where the ova is ingested
- In the small bowel the ova hatch
- Larvae travel to the lungs via the portal circulation and inferior vena cava
- In the lungs the larvae penetrate the Alveoli, migrate to the trachea and are swallowed into the gut where they become adult worms
- Ascaris lumbricoides can cause:
- Appendicitis
- Jaundice
- Infection with obstruction
- Growth retardation
- Pancreatitis
with a jaundiced liver
PruritusWhat is Pruritus ?Pruritus is caused by Enterobius vermicularis (pinworm)Describe the development of Enterobius vermicularis in the host
- Enterobius vermicularis is spread faecal orally
- The Enterobius vermicularis worm resides in the Ileum, Proximal Colon and Appendix
- Can cause Appendicitis
- However, the female migrates to the anus and lay eggs where it causes Pruritus
Intestinal obstruction secondary to Ascaris lumbricoides worm boluds
- necrotic bowel
- worms in vomit
Cerebral Malaria
- Dark Malaria Pigment