Infectious Diseases - Lecture Notes PDF

Infections & Infectious Diseases Dr. Barbara Carey Infectious diseases Most common afflictions of mankind. Their continuance requires: Reservoirs of infection: Human Animal Environmental Effective modes of transmission: airborne, direct contact, food & water Active immunity 1. Live attenuated vaccin...

Infections & Infectious Diseases Dr. Barbara Carey Infectious diseases Most common afflictions of mankind. Their continuance requires: Reservoirs of infection: Human Animal Environmental Effective modes of transmission: airborne, direct contact, food & water Active immunity 1. Live attenuated vaccines: oral poliomyelitis, measles, mumps, rubella, yellow fever, BCG 2. Inactivated organisms : whooping cough, typhoid, cholera, poliomyelitis, hepatitis b, rabies 3. Immunising components of organism : influenza, pneumococcal, meningococcal c conjugate (surface polysaccharide with protein) 4. Toxoid (inactivated toxin) tetanus, diphtheria Passive immunity 1. Natural transmission from mother to foetus 2. Artificial (high levels human / non-human immunoglobulin) Two types : a. Human normal immunoglobulin from pooled plasma of donors e.g. Hepatitis A b. Specific immunoglobulin from pooled blood of convalescent patients e.g. Tetanus, hepatitis C, rabies, varicella / zoster Diagnosis History : foreign travel, immigrants, occupation, domestic pets, sexual activity, drug addiction, tattooing, injections and transfusions. Examination : oral ulceration rashes lymphadenopathy hepatosplenomegaly Investigation 1. Baseline : FBC and blood film, CRP, ESR, liver function tests, urinalysis and chest x-ray 2. Microbiological examination of body fluids 3. Immunodiagnosis : Serology : specific IgG, IgM, IgA Antigen detection : e.g. ELISA 4. Tissue diagnosis : Aspiration / biopsy 5. Imaging procedures Herpes simplex Herpes simplex type 1 spread by infected saliva Herpes simplex type 2 spread by sexual contact Incubation period is 2-12 days Clinical features : Orolabial infection sore throat, fever vesicles on pharynx,buccal mucosa, gingiva & tongue which spreads to lips and face lymphadenopathy recurrence Herpes simplex ❖ Skin infections HSV1 or HSV2 herpetic whitlow primary infections ❖ Eye infections usually HSV1 corneal involvement is serious since it may cause blindness ❖ Genital / anal infections usually HSV2 Herpes simplex Complications : encephalitis - affects temporal lobes neonatal - serious since mortality is 60 % due to transfer of HSV-2 during parturition indication for a caesarian section erythema multiforme eczema herpeticum Treatment : Acyclovir, Valacylcovir Herpes zoster 1. Reactivation of varicella zoster virus 2. Clinical features : preceded by radicular pain and hyperaesthesia of overlying skin rash - unilateral, dermatomal intense erythema which rapidly become vesicles which crust oral, palatal or pharyngeal involvement if v affected ocular involvement causes keratitis or uveitis which may result in blindness Ramsay-Hunt syndrome – reactivation of VZV in the geniculate ganglion of the VII cranial nerve Herpes zoster 3. Complications : post-herpetic neuralgia neurological e.g. Meningitis 4. Treatment : acyclovir reduces pain / accelerates healing no effect on post-herpetic neuralgia Infectious mononucleosis 1. Epstein-Barr virus 2. Incubation period is 4-14 days 3. Clinical features : anorexia, malaise, fever sore throat cervical lymphadenopathy macular rash N.B Ampicillin tonsillitis with white exudate palatal petechiae palpable spleen jaundice (10%) Infectious mononucleosis 4. Complications : respiratory obstruction ruptured spleen hepatitis 5. Diagnosis : blood film Paul-Bunnell test Monospot test 6. Treatment is supportive Chicken pox 1. Varicella zoster virus 2. Incubation period is 14-16 days 3. Clinical features : rash - appears in crops and progresses from macule to papule to vesicle starts on trunk or scalp spreads to limbs and face vesicles dry and crust pruritis shallow ulcers on mm’s Chicken pox 4. Complications are rare and include : cellulitis or impetigo pneumonia neurological e.g. Acute cerebellar ataxia, Reyes syndrome congenital abnormalities 5. Treatment : antihistamines Acyclovir (severe cases/complications) Mumps 1. Paramyxovirus (rna) 2. Incubation period is 16-21 days 3. Spread by droplets from saliva and nasopharyngeal secretions 4. Clinical features : asymptomatic in 40% fever, malaise, "angle pain" enlargement of one or both parotids earache and displacement of earlobe parotid papillae inflamed difficulty in swallowing submandibular glands may be affected Mumps 5. Complications : neurological - aseptic meningitis, encephalitis orchitis - 20-25% in postpubertal non-parotid mumps - ovaries, thyroid, pancreas, breasts 6. Treatment : good oral hygiene scrotal support bed rest in meningitis Whooping cough 1.Bordetella pertussis (gram negative bacillus) 2.Incubation period is 7 days and is followed by the "catarrhal" phase which lasts 1-2 weeks 3.Spasmodic phase occupies next 4-6 weeks & consists of : severe paroxysmal cough with an inspiratory "whoop“ vomiting cyanosis or apnea Whooping cough 4. Complications : bronchopneumonia - secondary to inhalation of secretions during whoops convulsions pressure effects - subconjunctival haemorrhage facial petechiae during spasm cerebral haemorrhage prolapse of hernias laceration of lingual fraenum against the lower incisors 5. Investigation : paranasal swabs and culture on bordet-gengou medium immunofluorescent antibody test 6. Treatment is basically symptomatic Childhood exanthemas Measles German measles Enteroviral infection Infectious mononucleosis Scarlet fever Erythema infectiosum Roseola infantum Drug erruption Measles 1. Paramyxovirus (RNA) 2. Incubation period is 10 days 3. Clinical features : conjunctivitis (res eyes), lymphadenopathy Koplik's spots on buccal mucosa florid maculopapular rash which begins behind the ears and spreads to the face and trunk - brownish discolouration remains after 4. Complications : gingivostomatitis 5. Treatment is supportive while any complications are treated as appropriate German measles 1. Rubella (RNA) 2. Incubation period: 14-21 days 3. Clinical features : fever, malaise, catarrhal lymphadenopathy rash - starts face  trunk/limbs pink maculopapular, non-confluent Conjunctivitis 4. Diagnosis: essential in pregnant women 5. Complications: congenital rubella Enteroviral infections 1. Coxsackie virus A and B 2. E.g. Hand-foot-and-mouth disease 3. Clinical features : malaise, fever, anorexia sore mouth and throat vesicular rash involving buccal mucosa with or without the tongue, palate or gingiva hands are involved in 65%of cases feet often affected 4. No specific treatment Scarlet fever 1. Group a beta-haemolytic streptococci which produces erythrogenic toxin 2. Clinical features : follows a pharyngeal infection rash - diffuse erythema which blanches on pressure skin folds are dark circumoral pallor strawberry tongue 3. Treatment is penicillin Erythema infectiosum 1. Parvovirus B19 2. Clinical features : constitutional symptoms uncommon rash - livid erythema of cheeks (slapped cheeks) then maculo-papular on extremities and trunk as second fades it assumes a lacy reticular appearance 3. Diagnosis is made clinically and there is no specific treatment Roseola infantum 1. Several different viruses. 2. Clinical features : fever lasting 3-4 days rash - erythematous maculopapular or macular on chest and abdomen cervical lymphadenopathy upper eyelid oedema Seizures 3. Diagnosis is made clinically and there is no specific treatment