Transmission and Control of Infection Flashcards
Explain life cycles:
Direct
Indirect
Complex indirect
Direct: Species A → Species A
Indirect: Species A → Species B → Species A
Complex indirect: Species A → Species B → Species C → Species A
Define:
Aetiological agent
Final (definitive) host
Intermediate host
Aetiological agent = causative
Final (definitive) host – host which harbours the sexual stages of the parasite
Intermediate host – host which harbours the asexual/larval stages of the parasite
Define:
Vector
Reservoir Host
Vector – carrier/transmitter of the pathogen
Reservoir host – host which serves as a reservoir of a pathogen of medical/vetinary significance
Define:
Domestic reservoir
Sylvatic reservoir
Domestic reservoir – reservoir in domestic/companion animals
Sylvatic reservoir – reservoir in wild animals
name the types of vector transmission
Mechanical transmission
Biological transmission – pathogen passes through cycle in vector until
Transoval transmission – all offspring acquire the disease
Infective (environmental) transmission – water, vegetables etc
Name some things transmissable person to eprson
Person-to-person transmission
• Direct contact – ie STIs, touching hands
• Droplets – cough, sneezes, air conditioners
• Examples:
o Common cold o Meningococcal meningitis o Influenza o Impetigo o Measles o STIs o Chicken pox o Pertussis o MRS o Athlete’s foot o Giardiasis o Enterobiasis o Headlice o Scabies
Explain nosocomial and iatragenic transmission
Nosocomial & iatrogenic
• Direct spread from person to person within the hospital environment (nosocomial)
• Iatrogenic – contaminated medical instruments
What diseases are zoonotically transmissioned?
- Rabies
- Lyssa virus
- Bovine TB
- Anthrax
- Q fever
- Toxoplasmosis
- Hydatid
- Giardiasis
- Leptospirosis
- Larva migrans
What diseases are transmissable thru food?
- Salmonellosis
- Staph aureus
- Bacillus cereus
- Typhoid
- E coli
- Rotavirus
- Norovirus
- Listeriosis
- Botulism
- Bovine TB
- Toxoplasmosis
- Cryptosporidiosis
- Giardiasis
- Taeniasis
- Trichinosis
What diseases spread via the wateR?
• Water: o Hep A o Cholera o Typhoid o ETEC o Leptospirosis o Giardiasis o Amoebiasis o Schistosomiasis
What diseases spread via soil
o Melioidosis o Hookworm o Strongyloidiasis o Cutaneous Larva Migrans o Tungiasis
what diseases are spread by poor sanitation and hygiene
- Hep A
- Cholera
- Typhoid
- Amoebiasis
- Giardiasis
- Schistosomiasis
- Trichuriasis
- Ascariasis
- Hookworm
- Strongyloidiasis
- Enterobiasis
- Cysticerosis
- All enteric infections
Which diseases are spread via vectors?
Insects: yellow fever, Ross river virus, dengue fever, typhus, bubonic plague, Malaria, African sleeping sickness, filariasis, leishmaniasis
Mites – scrub typhus
Ticks – tick-borne encephalitis, spotted fevers, relapsing fever
Snails – fascioliasis, schistosomiasis
Describe measures used to control infection risk
• Treat cases
o Antimicrobial therapy, immunisation (dead or alive vaccines)
• Immunise
• Protect humans from contact with disease
o Nets, skin repellants, protective clothing etc
• Food inspection – control of food hygiene, hand washing
• Reservoir host control – trap animals, culling, treatment or immunisation of these hosts to eliminate the reservoir for human infection
• Vector control
o Chemical insecticides, molluscicdes
o Biological control
o Naturalistic (environmental) control – make the environment unsuitable for the vector
o Vector sterilization
o Genetic manipulation of vectors – to prevent carriage of disease
• Public health measures
o Education
• Education at the level of postgraduates, level of children
How was Hydatid’s control
- Formation of THEC
- Community involvement
- Sheep offal banned for dogs
- Dead sheeps on pastures had to be buried
- Abattoir inspection – quarantine
- Hydatid test strips – quarantine
- Education
Cholera control
• Prevent faeces contaminating water • Provide clearn water • Antibiotic treatment of infected cases FAECES SAMPLE o Gram negative rod o Grew on TCBS medium giving yellow colonies o Suggestive of Vibrio cholera
• Cholera control o Antibiotic treatment of infected cases o Sanitation & hygeine o Boiling water o Immunisation o Education
Describe Amoebic Dysentary
What do you see in the stool?
What is the lifecycle of the causative organism?
Control measures for ameobic dysentary
Severe dysentery, significant death, liver abscesses
Stool examination:- Microscopic motile organisms moving by means of pseudopodia, Containing RBCs, Suggestive of Entamoeba histolytica
Lifecycle of E. hystolytica
->Human ingests cysts, cysts in faeces
Control measures: o Treatment of infected humans o Sanitation (toilets) o Hygeine (hand washing) o Boiling water (chlorination ineffective) o Education
What is giardiasis?
What carries the pathogen?
Control measures?
Chronic diarrhea – Giardia duodenalis
Harboured by animals & humans
Giardia control
- Treatment of humans and ? domestic /companion animals
- Sanitation
- Hygiene
- Boiling drinking water (chlorination ineffective)
- Education
What is Tapeworm?
What causes it?
Control measures?
Segmented, no hooks → Beef Tapeworm, Taenia saginata
Epidemiology: human infected → egg → cow → human
Control o Treat humans o Sanitation o Beef inspection at abbatoir o Cooking of beef o Education
Hookworm epidemiology and control
Epidemiology: Human → egg → free-living larva → infective larva through skin → human
Control o treat humans o Sanitation o Soil treatment – salt o Shoes o Education
Toxoplasmosis epidemiology and control
Serious potential clinical effects for the immunocompromised & the foetus
Complex lifecycle
Control measures oWash hands after handling cat boxes oTreat cats? No treatment really oCull feral cats oDon’t feed cats raw mutton or pork oWash & Cook veges/salad plants oBoil/chlorinate water if liable to cat faecal contamination oCook meat oEducation oTreat pregnant women with currently acquired infection
Ross River Virus
epidemiology and control
• Epidemiology: Marsupial → mosquito → human
Control:
o Prevent building of this unnecessary development (unbiased assment)
oKill mosquitos – sprays, toxic
o Cull wild mammals – human/domestic animal reservoir
o Ensure canals are well flushed by tidal flow
o Mosquito repellant/nets/clothes
oEducation of politicians
Japanese B encephalitis
• Epidemiology: Pig → Mosquito → Human • Control o Immunise community members o Remove pigs pens from being too close to human dwellings o Mosquito control o Surveillance – humans & mammals o Education
Schistosomiasis - control, epidemiology, cause
Eg: Patient from Zimbabwe with massive hepatosplenomegaly, portal hypertension & marked eosinophilia
Intestinal bilharziasis due to Schistosoma mansoni
Epidemiology: Snail → humans
Control o Treat humans o Sanitation o Snail control • Chemical (effect on water & water life), biological, naturalistic o Safe water o Education
