Week 9: Digestive system (viral and protozoal) Flashcards
Which virus is responsible for 90% of viral gastroenteritis
Rotavirus
Paramyxovirus causes what viral disease
Mumps
What manifestations are seen in mumps
Inflammation and swelling of parotid (salivary) glands unilaterally, fever, pain
How is mumps transmitted
Saliva and respiratory secretions, via respiratory tract
What vaccine is used for mumps
MMR live attenuated vaccine
Which virus is the cause of cytomegalovirus inclusion disease
Herpes HSV5
Mechanism of viral inclusion in cytomegalovirus inclusion disease
HV5 incorporated into cell, causing nuclear inclusion and enlarged cell with viral inclusion body
Are antibodies effective in cytomegalovirus inclusion disease
No, antibodies are formed but fail to clear virus
What is the relevance of cytomegalovirus inclusion disease to pregnant women
Non immune pregnant women transfer the virus to the fetus, causing death or severe damage
How many viruses are capable of causing viral hepatitis
6
Causative agent of ergot poisoning
Mycotoxin of Claviceps purpeura (fungus)
How does Claviceps purpeura cause disease
The fungus causes smut infection on grain crops. Ingestion of grains contaminated with the fungus cause ergot poisoning with hallucinogenic symptoms
Aflatoxin causative agent
Mycotoxin of Asperguilus flavus
Asperguilus flavus is found on what and causes what
Peanuts and other foods, causing Aflatoxin poisoning and cirrhosis of the liver
6 protozoal diseases of digestive tract
Cryptosporidium, giardia, amoebic dysentry, helminthic diseases, nematode infections
Compare cryptosporidium parvum genotypes 1 and 2
Genotype 1 affects humans and is also known as C. hominis, genotype 2 affects humans and animals
How is cryptosporidium parvum/hominis transmitted
Faecal oral route from water contamination
What staining techniques are used to identify C. parvum?
Methyl green acts as a background for oocysts which do not stain, or oocysts can be stained using modified acid fast technique
Can also be stained using antibody staining or FISH
Can chlorine be used to eliminate oocysts of C. parvum?
No they are resistant to chlorine
What is the difference between platyhelminths and nematodes
Nematodes are round worms, platyhelminths are flat worms
What is a scolex in relation to tape worms?
The head region which has suckers
How do tape worms get nutrition?
Lack digestive system, so absorb food digested by human host through cuticle
What are proglottids in relation to tapeworms?
Segments of the worm’s body that contain eggs
How do Taenia saginata cause disease
Cattle ingest proglottides of the worm which contain eggs. Larvae hatch and migrate into the animal muscle. Humans consume infected meat, digesting the worms except for the scolex, which attaches to the gi epithelium
What is the difference between a definitive and intermediate host?
The definitive host is the one which harbors the adult parasite and where the parasite reproduces sexually. The intermediate host is the host which harbors the larval stage or the asexual forms of the parasite.
Do nematodes (round worms) have a digestive system?
YEs
Which gender of nematode is larger
Female
Do nematodes have a larval stage?
No
Hepatitis A characteristics
Single strand RNA, no envelope
Hepatitis A route of entry
Oral route via food and water, multiplies in GI tract epithelium
What clinical conditions are caused by Hepatitis A (6)
Anorexia, malaise, nausea, diarrhoea, abdominal discomfort, fever and chills
Hepatitis B characteristics
Enveloped, double stranded DNA
Describe the two structures of Hepatitis B
The viral DNA is contained within a capsomere. The capsomere containing the virus may either be housed within a spherical envelope particle or a tubular/filamentous envelope particle. The virus and capsomere housed within the envelope make up a Dane particle, which is the complete HB virus. The envelope features spike proteins which act as surface antigens.
How is hepatitis B transmitted
Blood and other body fluids (milk, saliva, semen) via sexual contact, non-sterile needles and other contaminated equipment, or transplacental transmission to foetus
Which groups are more likely to get Hepatitis B?
Gay dudes, straight peeps with lots of partners, IV drug users, chronic carrier mothers to bebes, healthcare professionals
Major complications of hepatitis B
Liver cirrhosis, liver cancer
Does HB have high or low mortality
Low- around 1-3%
How is HBsAg vaccine manufactured
Genetically engineered in yeast
Hepatitis C transmission (4)
Intimate contact with contaminated blood
Uterus from mother to foetus
Oral faecal route
Organ transplants
Complication of Hepatitis C
50% of cases progress to chronic hepatitis
How is Hepatitis C diagnosed and treated
Serological test for surface antigen, treated with alpha interferon assay and chemotherapy
Hepatitis D characteristics
Single stranded RNA, no envelope
Under what conditions does Hepatitis D infection occur?
The individual must also be infected with HBV so that the envelope of HBV covers the HDV capsid
Describe the two forms of hepatitis D infection
Acute (coinfection)
Chronic: progresses to liver damage with high fatality rate
What is the nature of the treatment for hepatitis D infection
Supportive, allowing liver damage to resolve, and to use the HBV vaccine
Hepatitis E characteristics and mode of transmission
Single stranded RNA, faecal oral
Which hepatitis virus is E most similar to?
Hepatitis A
Where is HEV most prevalent
South east asia
What differentiates HEV from other hepatitis viruses
Does not cause chronic liver disease
For which nematodes are the eggs infective for humans?
Enterobius vernicularis (pin worm) and Ascaris lumbricoides
For which nematodes are the larvae infective for humans
Necator americanus (hook worm) and trichinella spinalis
Which parts of the nematode life cycle occur in the host?
Entire life cycle occurs in one host- egg to mature adult
Name a cause of elephantiasis
Vuchereria bancrofti, blocks lymphatic drainage causing swelling of leg
Ascaris lumbricoides size
Large- around 30 cm
Ascaris lumbricoides life
Eggs are found in animal droppings. Hand to mouth contact with infected soil or unwashed vegetables. Reside inn small intestine of human and animals, feeding on semi-digested food.
Trichinella spiralis life
Encysted larvae in poorly cooked pork ingested. In SI larvae are freed from cysts, mature and sexually reproduce. Live nematodes born. Larvae enter lymph and blood, then encyst in muscles and other tissues. Cause trichinosis.
