Infectious and Parasitic disease II

Overview Respiratory infections GI and liver infections Meningitis Sexually transmitted diseases

Respiratory infections Viruses most common  Range from self limited, common cold to life threatening infection. Rhinoviruses  Viruses responsible for common cold  Composed of single stranded RNA, unencapsulated.  Induce production of IgG and IgA antibodies by the host to the particular subtype.  100’s of subtypes

Influenza viruses Contain 8 single stranded RNAs bound to nucleoproteins that determine the subtype, A, B or C. Have envelope containing a hemagglutinin and a neuraminidase which project out from the envelope and determine the further subtype of the virus eg. H1N5. Affect nasal channels, sinuses, eustachian tubes, tonsils and bronchioles. Hyperaemia, swelling, lymphomonocytic and plasmacytic infiltation of submucosa with oversecretion of mucus.

Influenza viruses Clearance of the virus occurs when cytotoxic T cells kill virus infected cells. Host develops antibodies to H and N components therefore preventing re-infection. Mutations occur in H and N, allowing new strains to emerge. Major complication is bacterial superinfection with pneumococcus, staphylococcus or haemophilus.

Haemophilus influenza Gram negative bacteria. Major cause of epiglottitis, meningitis and laryngotracheobronchitis – all life threatening conditions that affect children. Bacteria has a capsule that helps it evade host immune system. Children are vaccinatied against H. influenza type B. Causes fibrin rich exudates of neutrophils.

TB

Bacillus – Mycobacterium tuberculosis Important infectious disease worldwide, particularly in the developing world – 2 – 3 million deaths from TB per year. AIDS patients particularly vulnerable – multidrug resistant forms developing. Primary infection: resolves in 95% as causes T cell mediated response.

Classification of pnemonias Community acquired  Strep pneumoniae  Haemophilus influenza  S. aureus  Mycoplasma pneumonia  Chlamydia pnemonia Hospital acquired  Strep pneumoniae  Haemophilus influenza  E coli  Klebsiella  Serratia  Pseudomonas aerguinosa Pneumonia in immunocompromised

Diarrhoeal diseases Major causes:  Campylobacter  Salmonella  Rotavirus  Shigella  E. coli

Epidemiology Sporadic or outbreaks  Eg Campylobacter – sporadic  Shigella – outbreak  Related to their transmissibility  Big outbreak – Epidemic Seasonal pattern Age Patient profile

Diarrhoea kills by dehydration. Spread:  Faecal/oral route  Infection from animal (zoonosis)

Bacteria causing diarrhoea Staph aureus Bacillus cereus Clostridium perfringens Clostridium botulinum E coli Vibrio cholera Aeromonas species Yersinia enterocolitica Campylobacter Shigella Salmonella

Viral causes Rotavirus Adenovirus Norwalk/SRS viruses

Parasites Cryptosporidium Giardia Entamoebae

Syndromes Food poisoning Gastroenteritis  Tends to refer to greenish watery diarrhoea from small intestine Dysentary  Tends to mean from large bowel.  Mucus, possibly blood in the stool.

E coli Bacteria can be typed according to their cell antigen. E coli are identified by an O antigen. Various serotypes eg 044, 0157 Common serotype = 078

E. coli 0157 Haemorrhagic colitis. Very low infective dose required. Infected food especially ground beef Person to person spread. <5 years and the elderly. Barbeque season. Clinically:  Incubation 4-9 days  Watery blood stained diarrhoea.  Occasional vomiting.  Low grade fever.  10 days.

Hepatitis

Complication of Hepatitis C HCV infection Acute hepatitis Recovery (50%) Chronic persistant hepatitis (50%) Chronic hepatitis (50%) Chronic active hepatits Cirrhosis Hepatocellular ca

Other viral causes of hepatitis Cytomegalovirus Epstein Barr virus Herpes simplex Yellow fever Other causes of hepatitis: - Drugs - Autoimmune - Chemical

Meningitis

Organisms:  E. coli  Listeria  Haemophilus influenza  Strep pnemonia  Neisseria meningitidis  Fungi: Cyptococcal meningitis  Viral meningitis  TB meningitis  Protozoal meningitis (acanthamoeba)

Neisseria meningitidis (meningococcus) 1-3 day incubation Carried in throat by 10%. Droplet spread. Carriage increased when cough and cold going around.

Clinical symptoms and signs:  Neck stiffness  Aversion to light  Irritable  Headache  Pyrexial illness  Purpura (spots that do not blanch) 3 main types: A, B, C Lab diagnosis:  Lumbar puncture should show: Raised WCC Low glucose Raised protein Bacteria Neisseria meningitidis (meningococcus)

Vaccines available for types A and C.  A most common internationally  B problematic in Europe  C less of a problem Neisseria meningitidis (meningococcus)

Sexually transmitted diseases Syphilis Gonorrhoea Chlamydia Genital mycoplasms Vaginitis  Gardnerella vaginalis  Trichomonas vaginalis Warts – papilloma viruses Genital herpes

Syphilis

Initial contact causes primary syphilis  chancre, 2-10 weeks after contact Secondary syphilis  1 to 3 months after with flu like illness, measle like rash, myalgia and headache. Tertiary syphilis – 3-30 years later  Neurosyphilis  Cardiovascular syphilis  Progressive destructive disease Treatment = Penicillin

Gonorrhoea Neisseria gonorrhoea, gram –ve diplococcus Infects mucosa  Urethritis  Cervicitis Complications:  Pelvic inflammatory disease  Septic arthritis  Opthalmia neonatorum

Chlamydia Chlamydia trachomatis

Chlamydia Lives and reproduces intracellularly. Must use other cells’ DNA to reproduce. When enters cell, maturation arrest occurs and get multiplication inside cell and then released. Causes:  Chlamydial urethritis and cervicitis  Opthalmia neonatorum