CPH

• Vectors


  Living organisms that can transmit infectious diseases between humans or from animals to humans
• Vectors are usually arthropods, mosquitoes, rodents which are infected only as a passive or mechanical carrier of the agent
• Vector-Borne Diseases


  Human illnesses caused by parasites, viruses and bacteria that are transmitted by vectors
• Serotype


  A group of organisms that are characterized by a common set of antigens
• Incubation period


  The period between exposure to an infection and the appearance of the first symptoms
• Vectors and their Diseases

  • Sandflies - Leishmaniasis, Sandfly/Phlebotomus fever
  • Triatomine bugs (kissing bug) - Chagas' disease
  • Blackflies - Onchocerciasis
  • Ticks - Lyme disease
  • Tsetse flies - Sleeping sickness
  • Mites - Scrub typhus
  • Snails - Schistosomiasis
  • Lice - Louse-borne relapsing fever, Typhus fever
• Vectors are usually arthropods, mosquitoes, rodents which are infected only as a passive or mechanical carrier of the agent
• Dengue is a severe, flu-like illness that affects all ages and is transmitted by the bite of female Aedes aegypti/Aedes albopictus mosquitoes
• Dengue vector life cycle

  1. Female Aedes aegypti mosquitoes lay eggs in water

  2. Male feed on nectar, female feed on human/animal blood

  3. Eggs hatch into larvae, develop into pupae, then emerge as adult flying mosquitoes

  
• Vector-Borne Diseases


  Human illnesses caused by parasites, viruses and bacteria that are transmitted by vectors
• Serotype


  A group of organisms that are characterized by a common set of antigens
• Dengue virus


  A small single-stranded RNA virus comprising four distinct serotypes (DEN 1 to 4)
• Among the dengue serotypes, "Asian" genotypes of DEN-2 and DEN-3 are frequently associated with severe disease accompanying secondary dengue infections
• Incubation period


  The period between exposure to an infection and the appearance of the first symptoms
• Dengue pathogenesis


  1. Virus multiplies in the blood for 4-10 days

  2. Leads to plasma leakage, dehydration, organ failure
• Vectors and their Diseases

  • Sandflies - Leishmaniasis, Sandfly/Phlebotomus fever
  • Triatomine bugs (kissing bug) - Chagas' disease
  • Blackflies - Onchocerciasis
  • Ticks - Lyme disease
  • Tsetse flies - Sleeping sickness
  • Mites - Scrub typhus
  • Snails - Schistosomiasis
  • Lice - Louse-borne relapsing fever, Typhus fever
• Dengue clinical presentation

  • Febrile phase
  • Critical phase
  • Convalescent phase
• Dengue is also known as "Breakbone fever"
• Febrile phase


  • Sudden onset, 2-7 days duration, symptoms include severe headache, muscle/joint/bone pain, rash, minor hemorrhagic manifestations
• Dengue


  A severe, flu-like illness that affects all ages
• Critical phase


  • 24-48 hours duration, symptoms include defervescence, plasma leakage leading to dehydration, major hemorrhagic manifestations
• Dengue is transmitted by the bite of female Aedes aegypti/Aedes albopictus mosquitoes
• Convalescent phase


  • Resolution of symptoms, normalization of blood status
• Dengue is common in tropical countries and is a public health concern
• Plasma leakage


  A process in which the protein rich, fluid component of the blood leaks from blood vessels into the surrounding tissue
• Dengue can be prevented and controlled
• Dengue with warning signs

  • Abdominal pain
  • Persistent vomiting
  • Fluid accumulation
  • Mucosal bleed
  • Lethargy, restlessness
  • Liver enlargement
  • Increase in haematocrit with rapid decrease in platelet count
• Dengue vector life cycle


  1. Female Aedes aegypti mosquitoes lay eggs in water

  2. Male mosquitoes feed on nectar

  3. Female mosquitoes feed on human/animal blood to produce eggs

  4. Eggs hatch when submerged in water

  5. Larvae develop into pupae in 5 days

  6. Pupae develop into adult flying mosquitoes in 2-3 days
• Severe dengue


  Defined by plasma leakage leading to shock and/or fluid accumulation, severe bleeding, severe organ impairment
• Dengue virus


  A small single-stranded RNA virus comprising four distinct serotypes (DEN 1 to 4)
• Dengue diagnosis


  • Screening tests: Tourniquet test, complete blood count
  • Confirmatory tests: Dengue NS1 antigen, Dengue IgG/IgM
  • Gold standard: Polymerase Chain Reaction, Dengue Plaque Reduction Neutralization Test
• Tourniquet test


  A test to detect increased capillary fragility by inflating a blood pressure cuff and counting petechiae
• The "Asian" genotypes of DEN-2 and DEN-3 are frequently associated with severe disease accompanying secondary dengue infections
• Dengue pathogenesis


  1. Virus multiplies in the blood for 4-10 days

  2. Leads to plasma leakage, dehydration, organ failure
• Dengue management


  1. Hydration

  2. Symptomatic relief

  3. Blood transfusion when platelet count is low and there is active bleeding
• Dengue clinical presentation


  • Febrile phase
  • Critical phase
  • Convalescent phase
• Zika virus


  A flavivirus transmitted by Aedes mosquitoes, with an incubation period of 3-14 days
• Febrile phase


  • Sudden onset, 2-7 days duration, symptoms include severe headache, muscle/joint/bone pain, rash, minor hemorrhagic manifestations
• Zika symptoms

  • Fever
  • Rash
  • Conjunctivitis
  • Muscle and joint pain
  • Headache
• Critical phase


  • 24-48 hours duration, symptoms include defervescence, plasma leakage leading to dehydration, hemorrhagic manifestations